Cerebral hemisphere Flashcards
List the 5 lobes of the brain (cerebral hemispheres)
frontal, parietal, temporal, occipital, and insula
List the 5 main sulci/fissures and their relative locations
The lateral cerebral fissure (lateral sulcus) separates the temporal lobe from the frontal and parietal lobes. The insula lies deep within the fissure.
The longitudinal cerebral fissure separates the right and left hemispheres.
The central sulcus separates the frontal lobe from the parietal lobe.
The parieto-occipital fissure passes along the medial surface of the cerebral hemisphere and separates the parietal lobe from the occipital lobe.
The calcarine fissure/sulcus also passes along the medial surface of the hemisphere near the occipital pole.
List the main gyri of the FRONTAL lobe and their relative locations
The precentral sulcus lies anterior to the precentral gyrus and parallel to the central sulcus.
The superior and inferior frontal sulci extend from the precentral sulcus, dividing the lateral surface of the frontal lobe into three parallel gyri: the superior, middle, and inferior frontal gyri.
The inferior frontal gyrus is divided into three parts: the orbital part, the triangular, and the opercular part (refer to below image).
The orbital gyri are irregular in contour and are located on the orbital surface and the cingulate gyrus is the crescent-shaped on the medial surface between the cingulate sulcus and the corpus callosum.
The paracentral lobule is on the medial surface of the hemisphere and is the continuation of the precentral and postcentral gyri
List the main gyri of the PARIETAL lobe and their relative locations
The postcentral sulcus lies behind the postcentral gyrus. The intraparietal sulcus is a horizontal groove which separates the superior parietal lobule from the inferior parietal lobule.
The supramarginal gyrus is the portion of the inferior parietal lobule that arches above the lateral cerebral fissure.
The angular gyrus arches above the superior temporal sulcus and becomes continuous with the middle temporal gyrus.
The precuneus is located on the medial surface between the parieto-occipital fissure and the ascending end of the cingulate sulcus
List the main gyri of the OCCIPITAL lobe and their relative locations
The calcarine fissure divides the medial surface of the occipital lobe into the cuneus and the lingual gyrus.
The cortex on the banks of the calcarine fissure (striate cortex) which functions as the primary visual cortex.
The wedge-shaped cuneus lies between the calcarine and parieto-occipital fissures.
The lingual gyrus is located below the calcarine fissure.
The fusiform gyrus is on the basal surface of the occipital lobe.
List the main gyri of the TEMPORAL lobe and their relative locations
The lateral surface of the temporal lobe is divided into the parallel superior, middle, and inferior temporal gyri, which are separated by the superior and middle temporal sulci.
The fusiform gyrus is (occipitotemporal) gyrus is on the basal surface of the occipital lobe.
The parahippocampal gyrus is the most medial gyrus on the basal aspect of the temporal lobe. Its anterior part curves in the form of a hook; it is known as the uncus.
What are commissural (transverse) fibres. List examples
These fibers interconnect the two cerebral hemispheres such as:
The corpus callosum is the largest bundle of fibers connecting the corresponding parts of the opposite cerebral hemisphere.
The anterior commissure connects the two olfactory bulbs and temporal lobe structures.
The hippocampal commissure, or commissure of the fornix, joins the two hippocampi
What are projection fibres. List an example
These fibres connect the cerebral cortex to the brainstem and spinal cord (both directions). Corticospinal tract is an example of these fibres. Most of projection fibres pass through the internal capsule
What are association fibres. List examples
These fibers connect the various portions of a cerebral hemisphere and permit the cortex to function as a coordinated whole. Short association fibers (U fibers) connect adjacent gyri. Long association fibers connect more widely separated areas. Example of these fibres are the:
cingulum, a white band within the cingulate gyrus, connects the basal part of the brain and the parahippocampal gyrus.
arcuate fasciculus connects the frontal lobe with the temporal lobe areas which are associated with the speech.
superior longitudinal fasciculus connects portions of the frontal lobe with occipital and temporal areas.
inferior longitudinal fasciculus connects the temporal and occipital lobes.
List the 6 layers of the neocortex of cerebral hemisphere and their compositions
The molecular layer (I) contains afferent fibers that come from within the cortex or other brain region.
The external granular layer (II) is a rather dense layer composed of small cells.
The external pyramidal layer (III) contains pyramidal cells, frequently in row formation.
The internal granular layer (IV) is usually a thin layer with cells similar to those in the external granular layer.
The internal pyramidal layer (V) contains pyramidal cells that are fewer in number but larger in size than those in the external pyramidal layer. These cells project to distal structures (eg, brain stem and spinal cord).
The fusiform (multiform) layer (VI).
What is lateralization and what are the important cognitive activities associated with either side of the brain
Hemispheric dominance, also known as lateralization of brain function, refers to the tendency for either the left or the right side of the brain to carry out specific cognitive activities
- The dominant hemisphere (usually left)
Handedness: It is the most obvious asymmetry in cerebral function which is controlled by the dominance hemisphere (left hemisphere). Approximately 90% of the populations are right-handed and most individuals are clumsy in performing tasks such as writing or closing buttons with the nondominant hand.
Language: In most individuals, language function depends predominantly on the left hemisphere, and it is considered dominant for language in majority of right and left- handed individuals. Thus, lesions of the left hemisphere language areas usually cause language dysfunction, even in left-handed individuals.
- The non-dominant hemisphere (usually right)
-Complex visual-spatial skills
-Social interactions, emotional expression, and processing mathematical information.
-Music perception
-non verbal functions
What is callosal syndrome? What changes occur as a result of this?
Occurs when the corpus callosum, the bundle of nerve fibres connecting the two hemispheres of the brain, is partially or completely severed. The surgery is performed as a last resort to treat severe epilepsy, to prevent seizures from spreading from one hemisphere to the other. The procedure generally improves the epilepsy, however it reveals some remarkable changes as follow:
Language Processing:
When an image is shown only in the right visual field, the left hemisphere processes it and communicate it verbally, however when an image is shown only in the left visual field, the right hemisphere processes it but cannot communicate verbally because speech centres are typically left-lateralized.
Tactile Naming:
If an object is touched with only the left hand (while no visual cues are given), the patient cannot name it, although the nature of the object is understood.
There is no such difficulty when sensory data reaches the left or dominant hemisphere (that is, when the object is held in the right hand).
After section, the right hemisphere is rendered mute (agraphic), where it has no access to memory for language.
Bi-manual skills learnt before an operation are not affected
An expertise learnt post-operation with one hand is not transferable to the other.
What are Brodmann’s areas for primary motor, visual, auditory, Wernicke’s area and motor speech programming
motor- 4
visual- 17
auditory- 41
Wernicke’s area- 22
motor speech programming- 44,45
Explain why split- brain patients are not able to describe an object held in the left hand; however, they can when they hold it in the right hand
A 59-year-old right-handed woman with an explosive, unusual headache suffered syncope while coming down a flight of stairs. She was transferred to the emergency room where the clinical
examinations showed an informative spontaneous oral expression, there was difficulty in articulating sounds and words.
a) Explain what this condition is called and
b) damage to what brain region can cause these symptoms
