Cerebellar hemisphere

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Sulci, fissures and gyri

Identify the major sulci / fissures, gyri and lobes on the surface of the cerebrum

Lateral surface

  • Central sulcus
    • Separates frontal lobe from parietal lobe
    • Starts at the highest point of the brain midway between frontal and occipital poles
    • extends onto the medial surface of the cerebral hemisphere
  • Lateral fissure
    • Separates the frontal and parietal lobes from the temporal
  • Parieto-occipital sulcus
    • Only partially seen on the lateral view
    • Imaginary line drawn from it to the preoccipital notch separates the occipital lobe from the parietal lobe (superiorly) and temporal lobe (inferiorly)

Medial surface

  • Longitudinal fissure
    • separates the two cerebral hemispheres
    • occupied by the falx cerebri
    • corpus callosum forms the inferior limit of the fissure and falx cerebri
  • Calcarine sulcus
    • medial side of occipital lobe
    • extends from the occipital pole to the parieto-occipital sulcus
  • Cingulate sulcus
    • Superior to the named gyrus
  • Central sulcus
    • continues from the lateral surface
    • terminates at the cingulate sulcus
  • Parieto-occipital sulcus
    • Continues from the lateral sulcus
    • clearly demarcated on the medial surface
    • Extends inferiorly to the fissure between the cerebrum and cerebelllum

Ventral Surface

  • Parahippocampal gyrus
    • lies medial to the inferior temporal gyrus
    • continuation of the cingulate gyrus
  • medial-most portion is the uncus where the amygdaloid nucleus is situated

Miscellaneous Sulci

  • Frontal Lobe
    • precentral sulcus - parallel and rostral to central sulcus
    • superior frontal sulcus
    • inferior frontal sulcus
  • Parietal Lobe
    • postcentral sulcus - parallel and posterior to central sulcus
  • Temporal Lobe
    • superior temporal sulcus
    • inferior temporal sulcus

Miscellaneous Gyri

Major gyri lie adjacent to the correspondingly named sulci. In addition:

  • Parietal Lobe
    • supramarginal gyrus - caps the posterior end of the lateral fissure
    • angular gyrus - caps the end of the superior temporal sulcus
  • Occipital Lobe
    • cuneate gyrus - runs superior to the calcarine sulcus
    • lingual gyrus - runs inferior to the calcarine sulcus
    • cuneate and lingual gyri collectively are known as the striate cortex

Cingulate gyrus and sulcus

  • This gyrus runs immediately superior to the corpus callosum
  • curves in a C-shape and extends into the temporal lobe as the parahippocampal gyrus

Cortical function

Identify and define the functional cortical areas

Primary functional areas

  1. Somatosensory (3,1,2) - postcentral gyrus (lat. and med.), parietal lobe
  2. Motor (4) - precentral g. (lat. and med.), frontal lobe
  3. Visual (17) - occipital pole (lat.) and striate cortex (med.), occipital lobe
  4. Auditory (41) - superior temporal gyrus, temporal lobe

High Order Unimodal Association Areas

adjacent to the Primary Areas

  1. Sensory Association (5, 7) - parietal lobe
  2. Premotor (6) - frontal lobe; and Visual Eye Field (8) - frontal lobe
  3. Visual Association (18, 19) - occipital lobe (lat and med)
  4. Auditory Association (42) - temporal lobe

Heteromodal Association Areas

integrate inputs from different areas of the cortex

  1. Prefrontal - foresight planning etc., frontal lobe
  2. Paralimbic - memory, learning, emotion etc., frontal and temporal lobes
  3. Temporo-parietal - sensory integration, supramarginal and angular gyri of the parietal and temporal lobes

Language areas

lateralized on the left hemisphere in the majority of the population

  1. Wernicke's Area for sensory speech (22) - superior temporal gyrus, temporal lobe
  2. Broca's Area for motor speech (44) - inferior frontal gyrus, frontal lobe

Trace the major pathway linking the cerebral cortical areas that are responsible for language

The neural pathway for describing a visual image is located in the left cerebral hemisphere:

  1. Signals from the retina is relayed (via lateral geniculate ganglion) to the primary visual area of the striate cortex
  2. Signals are then relayed from the primary visual cortex to the adjacent association cortex
    • Here, recognition associations of the image are made in the visual association areas and temporo-parietal association area
  3. Signals of the associated image are sent to the Wernicke s area to assign names and words to the image
  4. Signals are sent via the arcuate fasciculus to the Broca's area where the sentence to be spoken is being formulated
  5. Signals from Broca's area travel to the vocalization area of the primary motor cortex
  6. Neurons from the vocalization area send descending tract to structures responsible to vocalization (e.g., larynx).

Map the somatotopic organization (homunculus) of the sensory and motor cortices

  • representation of the body is projected and mapped as the homunculus

True for both the motor (precentral gyrus) and sensory (postcentral) cortices

  • Lesions to a specific area of these gyri results in motor or sensory dysfunction of the corresponding part of the body
  • The cortical representation is not proportional to the size of the body part
  • Body parts which execute fine, skilled movements or are highly sensitive (such as hand and face) have larger representational mapping in the cortex
  • The sensory and motor homunculi are essentially identical
    • Exception: somatic sensation from the genital area is modestly represented in the cortical area just inferior to the foot area
      • There is miniscule representation of voluntary control of musculature in the genital area.

Cortical dysfunction

White matter

See White matter