SURFACE ANATOMY OF THE FOREBRAIN: LATERAL VIEW
The convolutions of the cerebral cortex permit a large expanse of cortex to be compactly folded into a small volume, an adaptation particularly prominent in primates. Major dependable landmarks separate the forebrain into lobes; the lateral (sylvian) fissure separates the temporal lobe below from the parietal and frontal lobes above, and the central sulcus separates the parietal and frontal lobes from each other. Several of the named gyri are associated with specific functional activities, such as the precentral gyrus (motor cortex) and the post-central gyrus (primary sensory cortex). Some gyri, such as the superior, middle, and inferior frontal and temporal gyri, serve as anatomical landmarks of the cerebral cortex. The insula, the fifth lobe of the cerebral cortex, is deep to the outer cortex and can be seen by opening the lateral fissure.
Some functional characteristics of the cerebral cortex, such as longterm memory and some cognitive capabilities, cannot be localized easily to a particular gyrus or region of cortex. However, other functional capabilities are regionally localized. For example, the inferior frontal gyrus on the left contains the neuronal machinery for expressive language capabilities; the occipital pole, particularly along the upper and lower banks of the calcarine fissure, are specialized for visual processing from the retino-geniculo-calcarine system. Some very discrete lesions in further processing sites such as vision-related regions of the temporal lobe can result in specific deficits, such as agnosia for the recognition of faces or the inability to distinguish animate objects. This knowledge provides some clues about how feature extraction in sensory systems might be achieved in neuronal networks.