Brain Anatomy: Inferior Surface and Occipitotemporal Gyri

Inferior Surface of the Brain

• The parahippocampal gyrus bends and expands medially, forming the uncus
• The occipitotemporal sulcus divides the region into medial and lateral occipitotemporal gyri
• The orbital surface of the frontal lobe features the gyrus rectus, which is limited laterally by the olfactory sulcus
• The H-shaped orbital sulci divide the rest of the orbital surface into four orbital gyri: anterior, posterior, medial, and lateral
• The interpeduncular fossa is bounded by the optic chiasma, optic tracts, cerebral peduncles, and pons
• The fossa contains the tuber cinereum, infundibulum, pituitary gland, mammillary bodies, posterior perforated substance, and CN III emerging from the midbrain

Functional Localization of the Cerebral Cortex

• The frontal lobe is involved in motor and sensory functions
• The parietal lobe is involved in spatial awareness of the body
• The temporal lobe is involved in auditory and visual processing
• The insular cortex is involved in sensory links to emotions and memory
• Broca's area is involved in speech production
• Wernicke's area is involved in speech comprehension

Topography of the Medial Surface

• The corpus callosum is a C-shaped structure with tapered anterior and rounded posterior ends
• The corpus callosum is divided into four parts: splenium, body, genu, and rostrum
• The area below the corpus callosum is the diencephalon
• The line from the tip of the central sulcus to the body of the corpus callosum separates the frontal and parietal lobes
• The line from the pre-occipital notch to the splenium of the corpus callosum isolates the temporal lobe

Topography of the Medial Surface: Sulci and Gyri

• The cingulate gyrus curves around the corpus callosum between the callosal sulcus and cingulate sulcus
• The area above the callosal sulcus is divided by the inflected sulcus into the medial frontal gyrus and paracentral lobule
• The precuneus is separated from the occipital lobe by the parieto-occipital sulcus
• The calcarine sulcus passes from the occipital pole to join the parieto-occipital sulcus and continues as the occipitocalcarine sulcus
• The triangular area between the two sulci is the cuneus
• The lingual gyrus marks the lower edge of the medial surface between the calcarine sulcus above and the collateral sulcus below