These structures, one in each cerebral hemisphere, are involved in the formation of long-term memories.
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Sensations from the hands are processed in parts of the brain called the somatosensory cortices, of which there is one in each cerebral hemisphere.
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Gray's Fig. 726 – Lateral surface of left cerebral hemisphere, viewed from the side. Gray's Fig. 727 – Medial surface of left cerebral hemisphere.
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For right handed people, the majority of speech production activity occurs in the left cerebral hemisphere.
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Neglect and related disorders. New York: Oxford University Press. In contrast, the left cerebral hemisphere is activated only by contralateral stimuli.
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The lesion involved in this syndrome is thought to be in the posterior thalamus on either side, or multiple areas of the right cerebral hemisphere.
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Human right cerebral hemisphere. Lateral view (left) and medial view (right). In both images, inferior temporal gyrus labeled at bottom. The areas colored green represent temporal lobe.
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Mental health services in Egypt. Journal of sociology & social Welfare 1991 Vol. Xviii No. 2 131. Some aspects of the role of the right cerebral hemisphere in psychiatry. Egypt.
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Diagram of lateralized visual pathways of the human brain The Divided Visual Field Paradigm is an experimental technique that involves measuring task performance when visual stimuli are presented on the left or right visual hemifields. If a visual stimulus appears in the left visual field (LVF), the visual information is initially projected to the right cerebral hemisphere (RH), and conversely, if a visual stimulus appears in the right visual field (RVF), the visual information is initially received by the left cerebral hemisphere (LH). In this way, if a cerebral hemisphere has functional advantages with some aspect of a particular task, an experimenter might observe improvements in task performance when the visual information is presented on the contralateral visual field.Banich, M.T. (2003).
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Association fibers are axons that connect cortical areas within the same cerebral hemisphere. In human neuroanatomy, axons (nerve fibers) within the brain, can be categorized on the basis of their course and connections as association fibers, projection fibers, and commissural fibers. The association fibers unite different parts of the same cerebral hemisphere, and are of two kinds: (1) short association fibers that connect adjacent gyri; (2) long association fibers that make connections between more distant parts.
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I make films using my left cerebral hemisphere and series — using my right hemisphere interview at Vedomosti, 28 April 2018 (in Russian) Kovalyov is married, he has a daughter and a son.
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In the end, Fowles uses Rebecca and Ayscough as representatives of two classes of people, one subjective, intuitive, mystical, artistic (i.e., "right-brained"); the other objective, analytical, and judgmental (i.e., "left-brained"). See cerebral hemisphere.
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Diagram of gyri of brain viewed on lateral hemisphere. Occipital gyri shown lower right Animation. Occipital lobe (red) of left cerebral hemisphere. The two occipital lobes are the smallest of four paired lobes in the human brain.
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While epilepsy- induced hypergraphia is usually lateralized to the left cerebral hemisphere in the language areas, hypergraphia associated with lesions and other brain damage usually occurs in the right cerebral hemisphere. Lesions to the right side of the brain usually cause hypergraphia because they can disinhibit language function on the left side of the brain. Hypergraphia has also been known to be caused by right hemisphere strokes and tumors. Lesions to Wernicke's area (in the left temporal lobe) can increase speech output, which can sometimes manifest itself in writing.
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The inferonasal retina are related to the anterior portion of the optic chiasm whereas superonasal retinal fibers are related to the posterior portion of the optic chiasm. The partial crossing over of optic nerve fibres at the optic chiasm allows the visual cortex to receive the same hemispheric visual field from both eyes. Superimposing and processing these monocular visual signals allow the visual cortex to generate binocular and stereoscopic vision. The net result is that the right cerebral hemisphere processes left visual hemifield, and the left cerebral hemisphere processes the right visual hemifield.
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Evidence suggests that the right cerebral hemisphere has a dominant role in attention and awareness to somatic sensations through ipsilateral and contralateral stimulation.Mesulam, M-M. [1981]. A cortical network for directed attention and unilateral neglect. Ann Neurol, 10: 309-325.Mesulam, M-M. [1990].
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More fossils of this species were found at La Venta and in the Ipururo Formation in Peru.Miocochilius anomopodus at Fossilworks.org The holotype specimen of the small typothere, a cursorial insectivore, had a cerebral hemisphere length of , canines of and a cheekbone of . The premaxilla measured .
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Functional magnetic resonance imaging and electroencephalogram studies have found that problem solving requiring insight involves increased activity in the right cerebral hemisphere as compared with problem solving not requiring insight. In particular, increased activity was found in the right hemisphere anterior superior temporal gyrus.
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A Complex partial seizure is a seizure that is associated with unilateral cerebral hemisphere involvement and causes impairment of awareness or responsiveness, i.e. alteration of consciousness.Trescher, William H., and Ronald P. Lescher 2000, p. 1748. ;Presentation Complex partial seizures are often preceded by an aura.
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This results in lesions receiving a higher (worse) score when occurring in the left hemisphere, compared to lesions of equal size in the right hemisphere. Due to this emphasis, the NIHSS is a better predictor of lesion volume in the strokes occurring within the left cerebral hemisphere.
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The two sides of perception. Cambridge, MA: > The MIT Press. Visual information can be transferred from one cerebral hemisphere to the other in as little as 3ms,Poffenberger, A.T. (1912). Reaction time to retinal stimulation: with special reference to the time lost in conduction through nerve centers (No.
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Commissural tracts connect corresponding cortical areas in the two hemispheres. They cross from one cerebral hemisphere to the other through bridges called commissures. The great majority of commissural tracts pass through the largest commissure the corpus callosum. A few tracts pass through the much smaller anterior and posterior commissures.
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Betz cells, along with other cortical neurons, send long axons down the spinal cord to synapse onto the interneuron circuitry of the spinal cord and also directly onto the alpha motor neurons in the spinal cord which connect to the muscles. At the primary motor cortex, motor representation is orderly arranged (in an inverted fashion) from the toe (at the top of the cerebral hemisphere) to mouth (at the bottom) along a fold in the cortex called the central sulcus. However, some body parts may be controlled by partially overlapping regions of cortex. Each cerebral hemisphere of the primary motor cortex only contains a motor representation of the opposite (contralateral) side of the body.
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The frontal lobes are located at the front of each cerebral hemisphere and positioned anterior to the parietal lobes. It is separated from the parietal lobe by the primary motor cortex, which controls voluntary movements of specific body parts associated with the precentral gyrus.Kuypers, H. (1981). Anatomy of the descending pathways.
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Biological psychiatry, 45, 1271-1284.De Bellis, M., & Thomas, L. (2003). Biologic findings of post-traumatic stress disorder and child maltreatment. Current Psychiatry Reports, 5, 108-117. Further studies show that neglected children have poor cerebral hemisphere integration and underdevelopment of the orbitofrontal cortex region which affects the child’s social skills.
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The hippocampus also encodes emotional context from the amygdala. This is partly why returning to a location where an emotional event occurred may evoke that emotion. There is a deep emotional connection between episodic memories and places. Due to bilateral symmetry the brain has a hippocampus in each cerebral hemisphere.
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Personality and Individual Differences, 21, 749-758. found evidence of a relative activation of the right cerebral hemisphere as compared with the left in high schizotypes attempting to induce a hallucinatory episode in the laboratory. This suggested a relative dissociation of arousal between the two hemispheres in such people as compared with controls.
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Measurement of the brain activity of "psychic" individuals such as Ingo Swann and Sean Harribance revealed unusual electrical brain patterns in the right hemisphere (parahippocampal region), increased photon emissions from the right cerebral hemisphere, and small decreases in the intensity of the geomagnetic field when the details of their experiences were most accurate.
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Medial view of the cerebral hemisphere. The retrosplenial cortex encompasses Brodmann areas 26, 29, and 30. The perirhinal cortex contains Brodmann area 35 and 36 (not shown) In humans, damage to the retrosplenial cortex results in topographical disorientation. Most cases involve damage to the right retrosplenial cortex and include Brodmann area 30.
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Rasmussen's encephalitis is a rare inflammatory neurological disease, characterized by frequent and severe seizures, loss of motor skills and speech, hemiparesis (weakness on one side of the body), encephalitis (inflammation of the brain), and dementia. The illness affects a single cerebral hemisphere and generally occurs in children under the age of 15.
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The first theory was proposed by William A. Hammond in 1883. This theory posits that achiria (the term was not officially coined at the time) is caused by an obstruction in the efferent path, which results in impulses being passed to the contralateral side of the body, hence reaching the cerebral hemisphere opposite to where the impulses originated from. In 1891, Albert Paul Weiss tried to validate this theory by blocking the posterior columns of the spinal cord. Bosc also did a similar demonstration in 1892, but he blocked one side of the cerebral hemisphere instead of the spinal cord, such that the signals trying to get to that hemisphere have to pass through the corpus callosum to the opposite hemisphere instead of other pathways.
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Lower extremity function is more spared than that of the faciobrachial region. The majority of the primary motor and somatosensory cortices are supplied by the MCA and the cortical homunculus can, therefore, be used to localize the defects more precisely. Middle cerebral artery lesions mostly affect the dominant hemisphere i.e. the left cerebral hemisphere.
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One of the proposed reasons for the decrease in performance when attention crosses the vertical meridian is the shifting of processing of the information from one cerebral hemisphere to the other, across the corpus callosum (Huges & Zimba, 1987). According to Downing and Pinker (1985),DOWNINGC, . J. and PINKER,S. The spatial structure of visual attention.
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Research using Transcranial magnetic stimulation suggests that the area corresponding to the Wernicke's area in the non-dominant cerebral hemisphere has a role in processing and resolution of subordinate meanings of ambiguous words—such as ‘‘river’’ when given the ambiguous word "bank." In contrast, the Wernicke's area in the dominant hemisphere processes dominant word meanings (‘‘teller’’ given ‘‘bank’’).
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Pachygyria (from the Greek "pachy" meaning "thick" or "fat" gyri) is a congenital malformation of the cerebral hemisphere. It results in unusually thick convolutions of the cerebral cortex. Typically, children have developmental delay and seizures, the onset and severity depending on the severity of the cortical malformation. Infantile spasms are common in affected children, as is intractable epilepsy.
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Each cerebral hemisphere has an outer layer of cerebral cortex which is of grey matter and in the interior of the cerebral hemispheres is an inner layer or core of white matter known as the centrum semiovale. The interior portion of the hemispheres of the cerebrum includes the lateral ventricles, the basal ganglia, and the white matter.
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Hemispatial neglect results most commonly from strokes and brain unilateral injury to the right cerebral hemisphere, with rates in the critical stage of up to 80% causing visual neglect of the left- hand side of space. Neglect is often produced by massive strokes in the middle cerebral artery region and is variegated, so that most sufferers do not exhibit all of the syndrome's traits. Right-sided spatial neglect is rare because there is redundant processing of the right space by both the left and right cerebral hemispheres, whereas in most left-dominant brains the left space is only processed by the right cerebral hemisphere. Although it most strikingly affects visual perception ('visual neglect'), neglect in other forms of perception can also be found, either alone or in combination with visual neglect.
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The right cerebral hemisphere is typically larger than the left, whereas the cerebellar hemispheres are typically closer in size. The adult human brain weighs on average about . In men the average weight is about 1370 g and in women about 1200 g. The volume is around 1260 cm3 in men and 1130 cm3 in women, although there is substantial individual variation.
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Hum Neurobiol, 2: 25-33. Thus, the left and right cerebral hemispheres exhibit redundant processing to the right- side of the body and a lesion to the left cerebral hemisphere can be compensated by the ipsiversive processes of the right cerebral hemisphere.Iachini, T., Ruggiero, G., Conson, M. & Trojano, L. [2009]. Lateralization of egocentric and allocentric spatial processing after parietal brain lesions.
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This phenomenon is frequently associated with damage to the right cerebral hemisphere resulting in severe sensory deficits that are observed on the contralesional (left) side of the body. A right-sided deficit is less commonly observed and the effects are reported to be temporary and minor.Weintraub, S., Ahern, G. L., Daffner, K.R. & Price, B.H. [1992]. Right-sided hemispatial neglect. Neurology, 42[3]: 223.
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Reduplicative paramnesia is the delusional belief that a place or location has been duplicated, existing in two or more places simultaneously, or that it has been 'relocated' to another site. It is one of the delusional misidentification syndromes; although rare, it is most commonly associated with acquired brain injury, particularly simultaneous damage to the right cerebral hemisphere and to both frontal lobes.
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Animation. Parietal lobe (red) of left cerebral hemisphere. In terms of prospective memory, the parietal lobe plays an important role in processing and recognizing cues that trigger and keep attention focused on intended actions while performing other tasks. This part of the brain is activated most intensely when these cues are visual or spatial.Burgess, P.W., Quayle, A., & Frith, C.D. (2001).
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The only clear explanatory factor for the variations in sleep amounts for birds of different species is that birds who sleep in environments where they are exposed to predators have less deep sleep than birds sleeping in more protected environments. A sleeping cockatiel A flamingo with at least one cerebral hemisphere awake Birds do not necessarily exhibit sleep debt, but a peculiarity that birds share with aquatic mammals, and possibly also with certain species of lizards (opinions differ about that last point), is the ability for unihemispheric sleep. That is the ability to sleep with one cerebral hemisphere at a time, while the other hemisphere is awake (Unihemispheric slow-wave sleep). When only one hemisphere is sleeping, only the contralateral eye will be shut; that is, when the right hemisphere is asleep the left eye will be shut, and vice versa.
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Hemimegalencephaly (HME), or unilateral megalencephaly, is a rare congenital disorder affecting all or a part of a cerebral hemisphere. It causes severe seizures, which are often frequent and hard to control. A minority might have seizure control with medicines, but most will need removal or disconnection of the affected hemisphere as the best chance. Uncontrolled, they often cause progressive intellectual disability and brain damage and stop development.
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One of the earliest fossil brain endocast studies has been performed for Triconodon. The olfactory lobe is large, with a teardrop-shaped outline, suggesting a well developed sense of smell. The cerebral hemisphere is long, oval and flat, lacking the inflated appearance present in monotremes, multituberculates and therians. The cerebrum is neither expanded anteriorly to overlap the posterior part of the olfactory lobe, nor is it hemispherical.
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View of the frontal lobe (red) in the left cerebral hemisphere As prospective memory involves remembering and fulfilling an intention, it requires episodic memory, declarative memory, and retrospective memory, followed by supervisory executive functions.Martin, T., McDaniel, M.A., Guynn, M.J., Houck, J.M., Woodruff, C.C., Bish, J.P., et al. (2007). Brain regions and their dynamics in prospective memory retrieval: A MEG study. International Journal of Psychophysiology, 64, 247–258.
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The zygomatic arches are missing in the skull, which are present in most mammals even of that size, such as rodents. The mandible also has a more primitive structure with a double articulating surface. The cerebral hemisphere is relatively small, which is necessary in manipulative abilities. However, the olfactory lobes are well developed, revealing the significance of the ability to smell in the shrew's survival.
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Research employing these techniques has linked increases in mental workload and allocation of attentional resources with increased activity in the prefrontal cortex. Studies employing PET, fMRI and TCD indicate a decline in activity in the prefrontal cortex correlates with vigilance decrement. Neuroimaging studies also indicate that the control of vigilance may reside in the right cerebral hemisphere in a variety of brain regions.Parasuraman, R. & Caggiano, G. (2005).
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Due to the three- dimensional curvature of this structure, two-dimensional sections such as shown are commonly seen. Neuroimaging pictures can show a number of different shapes, depending on the angle and location of the cut. Shape of human hippocampus and associated structures. Topologically, the surface of a cerebral hemisphere can be regarded as a sphere with an indentation where it attaches to the midbrain.
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The subparietal sulcus (Sulcus subparietalis) or suprasplenial sulcus is a sulcus, or crevice, on the medial surface of each cerebral hemisphere, above the splenium of the corpus callosum. It separates the precuneus from the posterior part of the cingulate gyrus. It is the posterior continuation of the cingulate sulcus. The cingulate sulcus actually "terminates" as the marginal sulcus of the cingulate sulcus (margin of cingulate gyrus).
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When deciding which cognitive therapy to employ, it is important to consider the primary cognitive style of the patient. Many individuals have a tendency to prefer visual imagery over verbalization and vice versa. One way of figuring out which hemisphere a patient favours is by observing their lateral eye movements. Studies suggest that eye gaze reflects the activation of cerebral hemisphere contralateral to the direction.
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Falcine meningioma is a meningioma arising from the falx cerebri and completely concealed by the overlying cortex. Falcine meningioma tends to grow predominately into one cerebral hemisphere but is often bilateral, and in some patients the tumor grows into the inferior edge of the sagittal sinus. However, although much information is available regarding meningiomas, little is known about falcine meningiomas.Chung SB, Kim CY, Park CK, Kim DG, Jung HW (2007).
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Animation. Parietal lobe of the left cerebral hemisphere. Although it is still unclear what precise deficits in brain function cause the symptoms of autotopagnosia, the location of brain damage is not as ambiguous. Autotopagnosia is most often attributed to lesions in the parietal lobe of the left hemisphere of the brain. However, it is also believed that the disorder can be caused by general brain damage as well.
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The role RAN plays in testing reading ability is contentious. Research supports the use of RAN as a measure of phonological processing, as a measure of orthographic processing and integration, and as a measure of reading ability. It has been suggested that RAN may link to reading because reading depends on object-naming circuits in the left cerebral hemisphere that are recruited in reading to underpin word-recognition abilities.
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There are, however, reasons to believe that different associations within the cerebral hemisphere have an effect on remembering events from a very early period in a person's life. Mixed-handedness and bilateral saccadic eye movements (as opposed to vertical or pursuit eye movements) have been associated with an earlier offset of childhood amnesia, leading to the conclusion that interactions between the two hemispheres correlate with increased memory for early childhood events.
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The lower portions of the face are controlled by the opposite cerebral hemisphere, causing asymmetric facial expression. Because the right hemisphere is more specialised for emotional expression, emotions are more strongly expressed on the left side of the face. , particularly for negative emotions. Asymmetries in expression can be seen in chimeric faces and also in portraits which more often show the left, more emotional side of the face than the right.
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The motor control for speech production in right handed people depends mostly upon areas in the left cerebral hemisphere. These areas include the bilateral supplementary motor area, the left posterior inferior frontal gyrus, the left insula, the left primary motor cortex and temporal cortex. There are also subcortical areas involved such as the basal ganglia and cerebellum. The cerebellum aids the sequencing of speech syllables into fast, smooth and rhythmically organized words and longer utterances.
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Wernicke's area is traditionally viewed as being located in the posterior section of the superior temporal gyrus (STG), usually in the left cerebral hemisphere. This area encircles the auditory cortex on the lateral sulcus, the part of the brain where the temporal lobe and parietal lobe meet. This area is neuroanatomically described as the posterior part of Brodmann area 22. However, there is an absence of consistent definitions as to the location.
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Hemineglect is more frequent and arguably more severe following damage to the right cerebral hemisphere of right-handed subjects. It has been proposed that the right parietal lobes are comparatively more responsible for the allocation of spatial attention, therefore damage to this hemisphere often produces more severe effects. Additionally, it is difficult to map with accuracy the visual sensory deficits in the neglected hemifield. Neglect is diagnosed using a variety of paper-and-pencil tasks.
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Animation. Parietal lobe (red) of left cerebral hemisphere. Research has shown that some aspects of the syndrome of unilateral visual neglect appear to be similar to normal subjects in a state of inattentional blindness. In neglect, patients with lesions to the parietal cortex fail to respond to and report stimuli presented on the side of space contralateral to damage. That is, they appear to be functionally blind to a range of stimuli.
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He saw this as an opportunity to address language localization. It wasn't until Leborgne, formally known as "tan", died when Broca confirmed the frontal lobe lesion from an autopsy. The second patient had similar speech impairments, supporting his findings on language localization. The results of both cases became a vital verification of the relationship between speech and the left cerebral hemisphere. The affected areas are known today as Broca’s area and Broca’s Aphasia.
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Skeleton Unlike earlier horses, its teeth were low crowned and contained a single gap behind the front teeth, where the bit now rests in the modern horse. In addition, it had another grinding tooth, making a total of six. Mesohippus was a browser that fed on tender twigs and fruit. The cerebral hemisphere, or cranial cavity, was notably larger than that of its predecessors; its brain was similar to that of modern horses.
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He saw this as an opportunity to address language localization. It wasn't until Leborgne, formally known as "tan", died when Broca confirmed the frontal lobe lesion from an autopsy. The second patient had similar speech impairments, supporting his findings on language localization. The results of both cases became a vital verification of the relationship between speech and the left cerebral hemisphere. The affected areas are known today as Broca’s area and Broca’s Aphasia.
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Journal of the American Veterinary Medical Association 239:480-485. The Journal of the American Veterinary Medical Association published a case study in which researchers successfully managed an intracranial phaeohyphomycotic fungal granuloma in a one-year-old male Boxer dog. Veterinarians of the Department of Veterinary Clinical Sciences at Tufts University surgically removed the granuloma in the right cerebral hemisphere. The patient was treated with fluconazole for 4 months, and was followed with voriconazole for 10 months.
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One of the first indications of brain function lateralization resulted from the research of French physician Pierre Paul Broca, in 1861. His research involved the male patient nicknamed "Tan", who suffered a speech deficit (aphasia); "tan" was one of the few words he could articulate, hence his nickname. In Tan's autopsy, Broca determined he had a syphilitic lesion in the left cerebral hemisphere. This left frontal lobe brain area (Broca's area) is an important speech production region.
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John Charles Cutting is a British psychiatrist specialising in schizophrenia research. He has written a number of books, and articles and reviews in professional journals, on the subjects of psychiatry, clinical psychology, schizophrenia and the functioning of the right cerebral hemisphere of the brain. Cutting has been an honorary senior lecturer at Kings College Hospital in London and the Institute of Psychiatry in London. E- Print The page mentions the author being honorary senior lecturer, beneath details of one of his books.
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The discipline of linguistics dedicated to studying the neurological aspects of language is called neurolinguistics. Early work in neurolinguistics involved the study of language in people with brain lesions, to see how lesions in specific areas affect language and speech. In this way, neuroscientists in the 19th century discovered that two areas in the brain are crucially implicated in language processing. The first area is Wernicke's area, which is in the posterior section of the superior temporal gyrus in the dominant cerebral hemisphere.
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He was habilitated into academic career (venia legendi) in 1978 and in 1983 became professor of neurology and psychiatry at the University of Cologne. In 1985 he was appointed director of the Department of Neurology at Merheim Hospital, University of Cologne. He held the until his 1994 retirement. Petrovici published numerous papers on cerebrovascular disease, seizure disorders, therapy of the malignant brain tumours, localisation theory of the higher brain functions, hemispheric specialisation and interhemispheric transfer of learning, the minor cerebral hemisphere and language.
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Each patient that suffers from apperceptive agnosia does not have brain damage in exactly the same area. However, brain damage in proximity to the occipital lobe is largely correlated with the patterns of deficit seen in apperceptive agnosics. For example, patient JB suffered extensive damage to the parietal-occipital areas to the left cerebral hemisphere leading to his deficit in the ability to name distinguish between structurally similar object. Visually presented object recognition is largely mediated by a hierarchical occipitotemporal pathway.
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The internal capsule is a white matter structure situated in the inferomedial part of each cerebral hemisphere of the brain. It carries information past the basal ganglia, separating the caudate nucleus and the thalamus from the putamen and the globus pallidus. The internal capsule contains both ascending and descending axons, going to and coming from the cerebral cortex. It also separates the caudate nucleus and the putamen in the dorsal striatum, a brain region involved in motor and reward pathways.
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Adult brain size varies from to in females and to in males, with the average being and , respectively. The right cerebral hemisphere is typically larger than the left, whereas the cerebellar hemispheres are typically of more similar size. Size of the human stomach varies significantly in adults, with one study showing volumes ranging from to and weights ranging from to . Male and female genitalia exhibit considerable individual variation, with penis size differing substantially and vaginal size differing significantly in healthy adults.
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Anosognosia was a term coined by Joseph Babinski to describe the clinical condition in which an individual suffered from left hemiplegia following a right cerebral hemisphere stroke yet denied that there were any problems with their left arm or leg. This condition is known as anosognosia for hemiplegia (AHP). This condition has evolved throughout the years and is now used to describe people who lack subjective experience in both neurological and neuropsychological cases. A wide variety of disorders are associated with anosognosia.
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The total number of long range fibers within a cerebral hemisphere is 2% of the total number of cortico-cortical fibers (across cortical areas) and is roughly the same number as those that communicate between the two hemispheres in the brain's largest white tissue structure, the corpus callosum. Schüz and Braitenberg note "As a rough rule, the number of fibres of a certain range of lengths is inversely proportional to their length." White matter in nonelderly adults is 1.7–3.6% blood.
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Decussated fibers later reach and connect these segments with the higher centers. The optic chiasm is the primary cause of decussation; nasal fibers of the optic nerve cross (so each cerebral hemisphere receives contralateral—opposite—vision) to keep the interneuronal connections responsible for processing information short. All sensory and motor pathways converge and diverge to the contralateral hemisphere.Excerpt from Cunningham's Textbook of Anatomy Although sensory pathways are often depicted as chains of individual neurons connected in series, this is an oversimplification.
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In Rasmussen's encephalitis, there is chronic inflammation of the brain, with infiltration of T lymphocytes into the brain tissue. In most cases, this affects only one cerebral hemisphere, either the left or the right. This inflammation causes permanent damage to the cells of the brain, leading to atrophy of the hemisphere; the epilepsy that this causes may itself contribute to the brain damage. The epilepsy might derive from a disturbed GABA release, the main inhibitory neurotransmitter of the mammalian brain.
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Hemispherectomy is a very rare neurosurgical procedure in which a cerebral hemisphere (half of the brain) is removed, disconnected, or disabled. This procedure is used to treat a variety of seizure disorders where the source of the epilepsy is localized to a broad area of a single hemisphere of the brain, notably Rasmussen's encephalitis. About one in three patients with epilepsy will continue to have persistent seizures despite epileptic drug therapy.Kraemer, Diana L., MD, and David Vossler Gregg, MD. "Epilepsy Surgery." emedicine.medscape.com/.
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1 (pp. 153-218). New York: Academic Press A major aim of administering the HRNB to patients was if possible to lateralize a lesion to either the left or right cerebral hemisphere by comparing the functioning on the both sides of the body on a variety of tests such as the Suppression or Sensory Imperception Test, the Finger Agnosia Test, Finger Tip Writing, the Finger Tapping Test, and the Tactual Performance Test.Russell, E.W., Neuringer, C., & Goldstein, G. (1970). Assessment of Brain Damage: A Neuropsychological Key Approach.
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The divided visual field paradigm capitalizes on the lateralization of the visual system. Each cerebral hemisphere only receives information from one half of the visual field—specifically, from the contralateral hemifield. For example, retinal projections from ganglion cells in the left eye that receive information from the left visual field cross to the right hemisphere at the optic chiasm; while information from the right visual field received by the left eye will not cross at the optic chiasm, and will remain on the left hemisphere.Jeffery, G. (2001).
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Figure 3: The ventral striatum and self-administration of amphetamine Each cerebral hemisphere has its own nucleus accumbens, which can be divided into two structures: the nucleus accumbens core and the nucleus accumbens shell. These substructures have different morphology and functions. Different NAcc subregions (core vs shell) and neuron subpopulations within each region (D1-type vs D2-type medium spiny neurons) are responsible for different cognitive functions. As a whole, the nucleus accumbens has a significant role in the cognitive processing of motivation, aversion, reward (i.e.
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Hemineglect , also known as unilateral visual neglect, attentional neglect, hemispatial neglect or spatial neglect, is a disorder incorporating a significant deficit in visuospatial attention. Hemineglect refers to the inability of patients with unilateral brain damage to detect objects in the side of space contralateral to the lesion (contralesional); i.e. damage to the right cerebral hemisphere resulting in neglect of objects on the left side of space, and is characterized by hemispheric asymmetry. Performance is generally preserved in the side ipsilateral to the lesion (ipsilesional).
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In 1861, Broca heard of a patient at the Bicêtre Hospital who had a 21-year progressive loss of speech and paralysis but neither a loss of comprehension nor mental function. Broca performed an autopsy and determined that the patient had a lesion in the frontal lobe in the left cerebral hemisphere. Broca published his findings from the autopsies of twelve patients in 1865. His work inspired others to perform careful autopsies with the aim of linking more brain regions to sensory and motor functions.
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The idea of self-parenting is that a person's "mind" is created in the form of a conversation between two voices generated by the two parts of the cerebral hemisphere. One is the "inner parent" represented by the left brain with the other voice being the "inner child" represented by the right brain. The manner and quality by which these "inner conversations" take place between the two voices is most accurately described as self-parenting. The inner parent is parenting the inner child within the inner conversations.
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The fatal shot went through the left side of his forehead and through his frontal bone. It then traveled through the left cerebral hemisphere of his brain, fractured his skull, and went out the back of his neck. Morelli was shot on the left side of his chest through a gap in his bulletproof vest. The bullet went through his left lung, through the back covering of his heart and into the right lung, with the bullet being recovered from his right chest cavity.
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Medial view of the cerebral hemisphere showing the location of the prefrontal cortex and more specifically the medial and ventromedial prefrontal cortex in purple The medial prefrontal cortex processes egocentric spatial information. It participates in the processing of short-term spatial memory used to guide planned search behavior and is believed to join spatial information with its motivational significance. The identification of neurons that anticipate expected rewards in a spatial task support this hypothesis. The medial prefrontal cortex is also implicated in the temporal organization of information.
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Iacoboni also suggests there exists dual attention in split-brained patients, which is implying that each cerebral hemisphere has its own attentional system. An alternative approach taken by Reuter-Lorenz et al. suggests that enhanced redundancy gain in the split brain is primarily due to a slowing of responses to unilateral stimuli, rather than a speeding of responses to bilateral ones. It is important to note that the simple reaction time in split-brained patients, even with enhanced redundancy gain, is slower than the reaction time of normal adults.
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The left cerebral hemisphere of the brain. The left-brain interpreter is a neuropsychological concept developed by the psychologist Michael S. Gazzaniga and the neuroscientist Joseph E. LeDoux. It refers to the construction of explanations by the left brain hemisphere in order to make sense of the world by reconciling new information with what was known before.Neurosociology: The Nexus Between Neuroscience and Social Psychology by David D. Franks 2010 page 34 The left-brain interpreter attempts to rationalize, reason and generalize new information it receives in order to relate the past to the present.
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Animation. Primary motor cortex (Brodmann area 4) of the left cerebral hemisphere shown in red. The primary motor cortex (Brodmann area 4) is a brain region that in humans is located in the dorsal portion of the frontal lobe. It is the primary region of the motor system and works in association with other motor areas including premotor cortex, the supplementary motor area, posterior parietal cortex, and several subcortical brain regions, to plan and execute movements. Primary motor cortex is defined anatomically as the region of cortex that contains large neurons known as Betz cells.
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View of the parietal lobe (red) in the left cerebral hemisphere The parietal lobe is typically involved in processing sensory information and is situated in the superior region of the brain. For prospective memory, the parietal lobe is important for recognizing cues that trigger an intended action, especially when the cues are visual or spatial. The parietal lobe is also responsible for maintaining attention on the intended action and inhibiting other activities during performance.Kondo, K., Maruishi, M., Ueno, H., Sawada, K., Hashimoto, Y., Ohshita, T., et al. (2010).
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The frontal lobe is located at the front of each cerebral hemisphere and positioned in front of the parietal lobe and above and in front of the temporal lobe.It was first discovered by Sir Niks Dhangar. It is separated from the parietal lobe by a space between tissues called the central sulcus, and from the temporal lobe by a deep fold called the lateral sulcus also called the Sylvian fissure. The precentral gyrus, forming the posterior border of the frontal lobe, contains the primary motor cortex, which controls voluntary movements of specific body parts.
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Lenz,Lenz, H.: Raumsinnstorung bei Hirnverletzungen, Deutsche Ztschr. Nervenh. 157:22-64, 1944. and McFie and associatesMcFie, J.; Piercy, M. F., and Zangwill, O. L.: Visuo-Spatial Agnosia Associated with Lesions of the Right Cerebral Hemisphere, Brain 75:433-471, 1952 proposed that the brain's right hemisphere controls a specific function in spatial perception, explaining why damage to the parieto-occipital lobe of the right hemisphere results in the loss of spatial perception. In his article, Denny- Brown alternately proposes that lesions of the parieto-occipital lobe cause errors in spatial summation, not spatial perception.
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The Breakdown theories maintain that stuttering is the result of a weakening or breakdown in physical systems that are necessary for smooth speech production. Cerebral dominance theories (in the stutterer, no cerebral hemisphere takes the neurological lead) and theories of perseveration (neurological "skipping record" of sorts) are both Breakdown theories. Auditory Monitoring theories suggest that stutters hear themselves differently from how other people hear them. Since speakers adjust their communication based upon the auditory feedback they hear (their own speech), this creates conflict between the input and the output process.
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Diagram labeling planum temporale in green. The planum temporale is the cortical area just posterior to the auditory cortex (Heschl's gyrus) within the Sylvian fissure. It is a triangular region which forms the heart of Wernicke's area, one of the most important functional areas for language.The Brain From Top To Bottom Original studies on this area found that the planum temporale was one of the most asymmetric regions in the brain, with this area being up to ten times larger in the left cerebral hemisphere than the right.
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Regional delta wave activity not associated with NREM sleep was first described by W. Grey Walter, who studied cerebral hemisphere tumors. Disruptions in delta wave activity and slow wave sleep are seen in a wide array of disorders. In some cases there may be increases or decreases in delta wave activity, while others may manifest as disruptions in delta wave activity, such as alpha waves presenting in the EEG spectrum. Delta wave disruptions may present as a result of physiological damage, changes in nutrient metabolism, chemical alteration, or may also be idiopathic.
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The premotor cortex occupies the part of Brodmann area 6 that lies on the lateral surface of the cerebral hemisphere. The medial extension of area 6, onto the midline surface of the hemisphere, is the site of the supplementary motor area, or SMA. The premotor cortex can be distinguished from the primary motor cortex, Brodmann area 4, just posterior to it, based on two main anatomical markers. First, the primary motor cortex contains giant pyramidal cells called Betz cells in layer V, whereas giant pyramidal cells are less common and smaller in the premotor cortex.
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Outer surface of cerebral hemisphere, showing areas supplied by cerebral arteries. Pink is the region supplied by the middle cerebral artery, blue is supplied by the anterior cerebral artery and yellow is supplied by the posterior cerebral artery. Cortical watershed strokes occur at the borders between those areas. These events are localized to two primary regions of the brain: # Cortical watershed strokes (CWS), or outer brain infarcts, are located between the cortical territories of the anterior cerebral artery (ACA), middle cerebral artery (MCA), and posterior cerebral artery (PCA).
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There is progression of the encephalitis - the left cerebral hemisphere has been involved with severe brain swelling and shift of the midline structures. The diagnosis may be made on the clinical features alone, along with tests to rule out other possible causes. An EEG will usually show the electrical features of epilepsy and slowing of brain activity in the affected hemisphere, and MRI brain scans will show gradual shrinkage of the affected hemisphere with signs of inflammation or scarring. Brain biopsy can provide very strong confirmation of the diagnosis, but this is not always necessary.
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Wernicke's area (; ), also called Wernicke's speech area, is one of the two parts of the cerebral cortex that are linked to speech, the other being Broca's area. It is involved in the comprehension of written and spoken language, in contrast to Broca's area, which is involved in the production of language. It is traditionally thought to reside in Brodmann area 22, which is located in the superior temporal gyrus in the dominant cerebral hemisphere, which is the left hemisphere in about 95% of right-handed individuals and 60% of left-handed individuals. Damage caused to Wernicke's area results in receptive, fluent aphasia.
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However, some body parts may be controlled by partially overlapping regions of cortex. Each cerebral hemisphere of the primary somatosensory cortex only contains a tactile representation of the opposite (contralateral) side of the body. The amount of primary somatosensory cortex devoted to a body part is not proportional to the absolute size of the body surface, but, instead, to the relative density of cutaneous tactile receptors on that body part. The density of cutaneous tactile receptors on a body part is generally indicative of the degree of sensitivity of tactile stimulation experienced at said body part.
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Grinker's myelinopathy is diagnosed by establishing a clinical history of carbon monoxide poisoning, narcotic overdose, myocardial infarction, or other global cerebral hypoxic events. This diagnosis can then be supported by neuroimaging confirmation of broadcast cerebral hemisphere demyelination sparing cerebellar and brainstem tracts. The neuroimaging evidence can also be used to diagnose Grinker's myelinopathy through an elevation in the concentrations of a myelin basic protein in the cerebrospinal fluid . Because this disease shares many of the symptoms with various forms of dementia or hysteria, these possibilities must be eliminated before a diagnosis for Grinker's myelinopathy can be made.
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Language functions such as grammar, vocabulary and literal meaning are typically lateralized to the left hemisphere, especially in right-handed individuals. p. 367 While language production is left- lateralized in up to 90% of right-handers, it is more bilateral, or even right-lateralized, in approximately 50% of left-handers. Chapter 7 Broca's area and Wernicke's area, associated with the production of speech and comprehension of speech, respectively, are located in the left cerebral hemisphere for about 95% of right-handers but about 70% of left-handers. Individuals who speak multiple languages demonstrate separate speech areas for each language.
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There are two types of prosopagnosia, congenital and acquired. Congenital prosopagnosia is an inability to recognize faces without a history of brain damage; while acquired prosopagnosia is caused by damage to the right occipital-temporal region of the brain. In the 1950s it was theorized that the right cerebral hemisphere was involved in facial recognition and in the 1960s this theory was supported by many experiments. Although the ability for overt facial recognition is inhibited in patients with prosopagnosia, there have been many studies done which show that some of these individuals may have the ability to recognize familiar faces covertly.
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None of these treatments can prevent permanent disability from developing. During the residual stage of the illness when there is no longer active inflammation, treatment is aimed at improving the remaining symptoms. Standard anti-epileptic drugs are usually ineffective in controlling seizures, and it may be necessary to surgically remove or disconnect the affected cerebral hemisphere, in an operation called hemispherectomy or via a corpus callosotomy. This usually results in further weakness, hemianopsia and cognitive problems, but the other side of the brain may be able to take over some of the function, particularly in young children.
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The lateral ventricles are the two largest ventricles of the brain and contain cerebrospinal fluid (CSF). Each cerebral hemisphere contains a lateral ventricle, known as the left or right ventricle, respectively. Each lateral ventricle resembles a C-shaped cavity that begins at an inferior horn in the temporal lobe, travels through a body in the parietal lobe and frontal lobe, and ultimately terminates at the interventricular foramina where each lateral ventricle connects to the single, central third ventricle. Along the path, a posterior horn extends backward into the occipital lobe, and an anterior horn extends farther into the frontal lobe.
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However, when presented with phonemic sounds of longer duration, such as vowels, the participants did not favor any particular ear. Due to the contralateral nature of the auditory system, the right ear is connected to Wernicke's area, located within the posterior section of the superior temporal gyrus in the left cerebral hemisphere. Sounds entering the auditory cortex are treated differently depending on whether or not they register as speech. When people listen to speech, according to the strong and weak speech mode hypotheses, they, respectively, engage perceptual mechanisms unique to speech or engage their knowledge of language as a whole.
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It consists of descending fibers that arise from cells in the motor area of the ipsilateral cerebral hemisphere. The impulse travels from these upper motor neurons (located in the pre-central gyrus of the brain) through the anterior column. In contrast to the fibers for the lateral corticospinal tract, the fibers for the anterior corticospinal tract do not decussate at the level of the medulla oblongata, although they do cross over in the spinal level they innervate. They then synapse at the anterior horn with the lower motor neuron which then synapses with the target muscle at the motor end plate.
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The limbic lobe is an arc-shaped region of cortex on the medial surface of each cerebral hemisphere of the mammalian brain, consisting of parts of the frontal, parietal and temporal lobes. The term is ambiguous, with some authors including the paraterminal gyrus, the subcallosal area, the cingulate gyrus, the parahippocampal gyrus, the dentate gyrus, the hippocampus and the subiculum; while the Terminologia Anatomica includes the cingulate sulcus, the cingulate gyrus, the isthmus of cingulate gyrus, the fasciolar gyrus, the parahippocampal gyrus, the parahippocampal sulcus, the dentate gyrus, the fimbrodentate sulcus, the fimbria of hippocampus, the collateral sulcus, and the rhinal sulcus, and omits the hippocampus.
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Since USWS allows for the one eye to be open, the cerebral hemisphere that undergoes slow-wave sleep varies depending on the position of the bird relative to the rest of the flock. If the bird's left side is facing outward, the left hemisphere will be in slow-wave sleep; if the bird's right side is facing outward, the right hemisphere will be in slow-wave sleep. This is because the eyes are contra-lateral to the left and right hemispheres of the cerebral cortex. The open eye of the bird is always directed towards the outside of the group, in the direction from which predators could potentially attack.
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Animation. Parietal lobe (red) of left cerebral hemisphere. The parietal lobe is defined by three anatomical boundaries: The central sulcus separates the parietal lobe from the frontal lobe; the parieto-occipital sulcus separates the parietal and occipital lobes; the lateral sulcus (sylvian fissure) is the most lateral boundary, separating it from the temporal lobe; and the longitudinal fissure divides the two hemispheres. Within each hemisphere, the somatosensory cortex represents the skin area on the contralateral surface of the body. Immediately posterior to the central sulcus, and the most anterior part of the parietal lobe, is the postcentral gyrus (Brodmann area 3), the primary somatosensory cortical area.
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Image 2: Cross-section of cerebral hemisphere showing structure and location of hippocampus Coronal section of the brain of a macaque monkey, showing hippocampus (circled) The hippocampus can be seen as a ridge of gray matter tissue, elevating from the floor of each lateral ventricle in the region of the inferior or temporal horn. This ridge can also be seen as an inward fold of the archicortex into the medial temporal lobe. The hippocampus can only be seen in dissections as it is concealed by the parahippocampal gyrus.Amaral and Lavenex, 2006 The cortex thins from six layers to the three or four layers that make up the hippocampus.
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The limbic lobe is an arc-shaped region of cortex on the medial surface of each cerebral hemisphere of the mammalian brain, consisting of parts of the frontal, parietal and temporal lobes. The term is ambiguous, with some authors including the paraterminal gyrus, the subcallosal area, the cingulate gyrus, the parahippocampal gyrus, the dentate gyrus, the hippocampus and the subiculum; while the Terminologia Anatomica includes the cingulate sulcus, the cingulate gyrus, the isthmus of cingulate gyrus, the fasciolar gyrus, the parahippocampal gyrus, the parahippocampal sulcus, the dentate gyrus, the fimbrodentate sulcus, the fimbria of hippocampus, the collateral sulcus, and the rhinal sulcus, and omits the hippocampus.
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However, A1 participates in coding more complex and abstract aspects of auditory stimuli without coding well the frequency content, including the presence of a distinct sound or its echoes. Like lower regions, this region of the brain has combination-sensitive neurons that have nonlinear responses to stimuli. Recent studies conducted in bats and other mammals have revealed that the ability to process and interpret modulation in frequencies primarily occurs in the superior and middle temporal gyri of the temporal lobe. Lateralization of brain function exists in the cortex, with the processing of speech in the left cerebral hemisphere and environmental sounds in the right hemisphere of the auditory cortex.
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In 1879, Crichton-Browne published his own considerations of the neuropathology of insanity making some detailed predictions about the morbid anatomy of the human brain in cases of severe psychiatric disorder. He proposed that, in the insane, the weight of the brain was reduced, that the lateral ventricles were enlarged, and that the burden of damage fell on the left cerebral hemisphere. This involved an evolutionary view of cerebral localisation with an emphasis on the asymmetry of cerebral functions. He derived this from the clinical research of the French anatomist Paul Broca (1824–1880)McManus, Chris (2002) Right Hand, Left Hand: The Origins of Asymmetry in Brains, Bodies, Atoms and Cultures London: Weidenfeld and Nicolson.
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From 1936 to 1940, interrupted by the war and never resumed, Beritashvili with his assistant Nina Chichinadze (1896-1972) performed a series of ingenious experiments, testing the ability of one cerebral hemisphere to search out memories initially laid down in the other. Although the puzzle posed by the “two brains” and the huge band of fibers connecting them, had been recognized for centuries, and desultorily explored, almost nothing was known concerning hemispheric interchange, if any. They showed that training the pigeon via one eye, to distinguish different colored patterns, conveyed no advantage to learning with the other, untrained eye. In other words, for these complex visual stimuli what had been learned with one hemisphere was inaccessible to the other.
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In a 1976 published essay, the psychiatrists Colin Martindale, Nancy Hasenfus, and Dwight Hines (University of Maine) suggested that Hitler had suffered from a sub-function of the left hemisphere of the brain. They referred to the tremor of his left limbs, his tendency for leftward eye movements and the alleged missing of the left testicle. They believed that Hitler's behavior was dominated by his right cerebral hemisphere, a situation that resulted in symptoms such as a tendency to the irrational, auditory hallucinations, and uncontrolled outbursts. Martindale, Hasenfus and Hines even suspected that the dominance of the right hemisphere contributed to the two basic elements of Hitler's political ideology: antisemitism and Lebensraum ideology.
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Medial view of the right cerebral hemisphere showing the entorhinal cortex in red at the base of the temporal lobe The dorsalcaudal medial entorhinal cortex (dMEC) contains a topographically organized map of the spatial environment made up of grid cells. This brain region thus transforms sensory input from the environment and stores it as a durable allocentric representation in the brain to be used for path integration. The entorhinal cortex contributes to the processing and integration of geometric properties and information in the environment. Lesions to this region impair the use of distal but not proximal landmarks during navigation and produces a delay- dependent deficit in spatial memory that is proportional to the length of the delay.
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Donald Shankweiler and Michael Studdert- Kennedy used a dichotic listening technique (presenting different nonsense syllables simultaneously to opposite ears) to demonstrate the dissociation of phonetic (speech) and auditory (nonspeech) perception by finding that phonetic structure devoid of meaning is an integral part of language, typically processed in the left cerebral hemisphere. Liberman, Cooper, Shankweiler, and Studdert-Kennedy summarized and interpreted fifteen years of research in "Perception of the Speech Code," still among the most cited papers in the speech literature. It set the agenda for many years of research at Haskins and elsewhere by describing speech as a code in which speakers overlap (or coarticulate) segments to form syllables. Researchers at Haskins connected their first computer to a speech synthesizer designed by the Laboratories' engineers.
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The primary somatosensory cortex is located in the postcentral gyrus, and is part of the somatosensory system. It was initially defined from surface stimulation studies of Wilder Penfield, and parallel surface potential studies of Bard, Woolsey, and Marshall. Although initially defined to be roughly the same as Brodmann areas 3, 1 and 2, more recent work by Kaas has suggested that for homogeny with other sensory fields only area 3 should be referred to as "primary somatosensory cortex", as it receives the bulk of the thalamocortical projections from the sensory input fields. At the primary somatosensory cortex, tactile representation is orderly arranged (in an inverted fashion) from the toe (at the top of the cerebral hemisphere) to mouth (at the bottom).
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Exactly how this may occur is not well understood, but a process of gradual recovery from alien hand syndrome when the damage is confined to a single cerebral hemisphere has been reported. In some instances, patients may resort to constraining the wayward, undesirable and sometimes embarrassing actions of the impaired hand by voluntarily grasping onto the forearm of the impaired hand using the intact hand. This observed behavior has been termed "self-restriction" or "self-grasping". In another approach, the patient is trained to perform a specific task, such as moving the alien hand to contact a specific object or a highly salient environmental target, which is a movement that the patient can learn to generate voluntarily through focused training in order to effectively override the alien behavior.
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Pusher syndrome is a clinical disorder following left or right brain damage in which patients actively push their weight away from the nonhemiparetic side to the hemiparetic side. In contrast to most stroke patients, who typically prefer more weight-bearing on their nonhemiparetic side, this abnormal condition can vary in severity and leads to a loss of postural balance. The lesion involved in this syndrome is thought to be in the posterior thalamus on either side, or multiple areas of the right cerebral hemisphere. With a diagnosis of pusher behaviour, three important variables should be seen, the most obvious of which is spontaneous body posture of a longitudinal tilt of the torso toward the paretic side of the body occurring on a regular basis and not only on occasion.
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Donald Shankweiler's research career has spanned a number of areas related speech perception, reading, and cognitive neuroscience. His main interests have been studying the acquisition of reading and writing, understanding disorders of reading, writing, and spoken language, and exploring the representation of spoken and written language in the brain. In the 1960s, Shankweiler and Michael Studdert-Kennedy used a dichotic listening technique (presenting different nonsense syllables simultaneously to opposite ears) to demonstrate the dissociation of phonetic (speech) and auditory (nonspeech) perception by finding that phonetic structure devoid of meaning is an integral part of language, typically processed in the left cerebral hemisphere. Alvin Liberman, Franklin S. Cooper, Shankweiler, and Studdert- Kennedy summarized and interpreted fifteen years of research in a paper "Perception of the Speech Code," that argued for the motor theory of speech perception.
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The absence of proprioception or two-point tactile discrimination on one side of the body suggests injury to the contralateral side of the primary somatosensory cortex. However, depending on the extent of the injury, damage can range in loss of proprioception of an individual limb or the entire body. A deficit known as cortical astereognosis of the receptive type describes an inability to make use of tactile sensory information for identifying objects placed in the hand. For example, if this type of injury effects the hand region in the primary somatosensory cortex for one cerebral hemisphere, a patient with closed eyes cannot perceive the position of the fingers on the contralateral hand and will not be able to identify objects such as keys or a cell phone if they are placed into that hand.
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Anterior cingulate gyrus of left cerebral hemisphere, shown in red The anterior cingulate cortex can be divided anatomically based on cognitive (dorsal), and emotional (ventral) components. The dorsal part of the ACC is connected with the prefrontal cortex and parietal cortex, as well as the motor system and the frontal eye fields, making it a central station for processing top-down and bottom-up stimuli and assigning appropriate control to other areas in the brain. By contrast, the ventral part of the ACC is connected with the amygdala, nucleus accumbens, hypothalamus, hippocampus, and anterior insula, and is involved in assessing the salience of emotion and motivational information. The ACC seems to be especially involved when effort is needed to carry out a task, such as in early learning and problem-solving.
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Evidence for this comes from patients with damage to the right cerebral hemisphere, who, due to their brain damage, are unable to explicitly report any of the qualities of objects held in their left hand when another object is simultaneously presented in their right hand. Despite this fact, when the patients are asked to compare the characteristics of objects presented to either hand, their judgements are influenced by objects previously held in their right hand. This suggests that the patients have some memory for the properties of objects recently removed from their right hand that they are not consciously aware of, and that this memory is affecting their accuracy on subsequent tasks. Similar evidence has been found in healthy individuals of varying ages, and in patients with Alzheimer's disease.
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Other important fact of the representation of the star in the cerebral cortex is that each hemisphere had clearly visible set of 11 stripes representing the contralateral star. In some favorable cases, a smaller third set of stripes was also apparent; opposite to other body structures that have a unique representation, with each half of the body represented in the opposite cerebral hemisphere. Thus, opposite to other species, the somatosensory representation of the tactile fovea is not correlated with anatomical parameters but rather is highly correlated with patterns of behavior. Recordings from active neurons in the somatosensory cortex show that most cells (97%) responded to light tactile stimulation with a mean latency of 11.6 milliseconds. Besides a fairly large proportion of these neurons (41%) were inhibited by stimulation of proximate Eimer’s organs outside their excitatory receptive field.
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Ornstein's book The Right Mind deals with split-brain studies and other experiments or clinical evidence revealing the abilities of the right cerebral hemisphere. He also wrote on the brain's role in health in The Healing Brain with David Sobel of Kaiser Permanente; the way in which human consciousness is unable to understand the fast paced modern world in New World New Mind: Moving Toward Conscious Evolution with Paul Ehrlich; and the way in which our current consciousness has developed in The Axemaker's Gift, with James Burke, a book that addressed the way in which Western culture has developed and our minds along with it. Ornstein worked to reconcile the wisdom traditions of the East and science in The Psychology of Consciousness and was interested in promoting the modern Sufism of Idries Shah. Shah and Ornstein met in the 1960s.
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Along the length of the primary motor and sensory cortices, the areas specializing in different parts of the body are arranged in an orderly manner, although ordered differently than one might expect. The toes are represented at the top of the cerebral hemisphere (or more accurately, "the upper end", since the cortex curls inwards and down at the top), and then as one moves down the hemisphere, progressively higher parts of the body are represented, assuming a body that's faceless and has arms raised. Going further down the cortex, the different areas of the face are represented, in approximately top-to-bottom order, rather than bottom-to- top as before. The homunculus is split in half, with motor and sensory representations for the left side of the body on the right side of the brain, and vice versa.
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Unihemispheric sleep refers to sleeping with only a single cerebral hemisphere. The phenomenon has been observed in birds and aquatic mammals, as well as in several reptilian species (the latter being disputed: many reptiles behave in a way which could be construed as unihemispheric sleeping, but EEG studies have given contradictory results). Reasons for the development of unihemispheric sleep are likely that it enables the sleeping animal to receive stimuli—threats, for instance—from its environment, and that it enables the animal to fly or periodically surface to breathe when immersed in water. Only NREM sleep exists unihemispherically, and there seems to exist a continuum in unihemispheric sleep regarding the differences in the hemispheres: in animals exhibiting unihemispheric sleep, conditions range from one hemisphere being in deep sleep with the other hemisphere being awake to one hemisphere sleeping lightly with the other hemisphere being awake.
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This is because the image seen in the left visual field is sent only to the right side of the brain (see optic tract), and most people's speech-control center is on the left side of the brain. Communication between the two sides is inhibited, so the patient cannot say out loud the name of that which the right side of the brain is seeing. A similar effect occurs if a split-brain patient touches an object with only the left hand while receiving no visual cues in the right visual field; the patient will be unable to name the object, as each cerebral hemisphere of the primary somatosensory cortex only contains a tactile representation of the opposite side of the body. If the speech-control center is on the right side of the brain, the same effect can be achieved by presenting the image or object to only the right visual field or hand.
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The significant increase in the size of the cerebral hemisphere through evolution has been made possible in part through the evolution of the vascular pia mater, which allows nutrient blood vessels to penetrate deep into the intertwined cerebral matter, providing the necessary nutrients in this larger neural mass. Throughout the course of life on earth, the nervous system of animals has continued to evolve to a more compact and increased organization of neurons and other nervous system cells. This process is most evident in vertebrates and especially mammals in which the increased size of the brain is generally condensed into a smaller space through the presence of sulci or fissures on the surface of the hemisphere divided into gyri allowing more superficies of the cortical grey matter to exist. The development of the meninges and the existence of a defined pia mater was first noted in the vertebrates, and has been more and more significant membrane in the brains of mammals with larger brains.
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The term third visual complex refers to the region of cortex located immediately in front of V2, which includes the region named visual area V3 in humans. The "complex" nomenclature is justified by the fact that some controversy still exists regarding the exact extent of area V3, with some researchers proposing that the cortex located in front of V2 may include two or three functional subdivisions. For example, David Van Essen and others (1986) have proposed the existence of a "dorsal V3" in the upper part of the cerebral hemisphere, which is distinct from the "ventral V3" (or ventral posterior area, VP) located in the lower part of the brain. Dorsal and ventral V3 have distinct connections with other parts of the brain, appear different in sections stained with a variety of methods, and contain neurons that respond to different combinations of visual stimulus (for example, colour-selective neurons are more common in the ventral V3).
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54) Dandy's surgical innovations proceeded at an astounding rate as he became increasingly comfortable operating on the brain and spinal cord. He described in 1921 an operation for the removal of tumors of the pineal region, in 1922 complete removal of tumors of the cerebellopontine angle (namely acoustic neuromas), in 1922 the use of endoscopy for the treatment of hydrocephalus ("cerebral ventriculoscopy"), in 1925 sectioning the trigeminal nerve at the brainstem to treat trigeminal neuralgia, in 1928 treatment of Ménière's disease (recurrent vertiginous dizziness) by sectioning the vestibular nerves, in 1929 removal of a herniated disc in the spine, in 1930 treatment of spasmodic torticollis, in 1923 removal of the entire cerebral hemisphere ("hemispherectomy") for the treatment of malignant tumors, in 1933 removal of deep tumors within the ventricular system, in 1935 treatment of carotid- cavernous fistulas (CCFs), in 1938 ligation or "clipping" of an intracranial aneurysm, and in 1941 removal of orbital tumors. Remarkably, these operations continue to be performed today essentially in the same form described by Dandy. As medicine progresses, other contributions by Dandy have been replaced by alternative therapies.
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