Cerebrum

The cerebrum, consisting of five paired lobes within two convoluted hemispheres, contains gray matter in its cortex and in deeper cerebral nuclei. Most of what are considered to be the higher functions of the brain are performed by the cerebrum.

The cerebrum (fig. 8.5), which is the only structure of the telencephalon, is the largest portion of the brain (accounting for about 80% of its mass) and is the brain region primarily responsible for higher mental functions. The cerebrum consists of right and left hemispheres, which are connected internally by a large fiber tract called the corpus callosum (see fig. 8.1). The corpus callosum is the major tract of axons that functionally interconnects the right and left cerebral hemispheres.

The Central Nervous System 193

Precentral Superior frontal gyrus gyrus

Superior frontal sulcus

Central sulcus

Postcentral gyrus

Frontal lobe

Central sulcus

Postcentral gyrus

Superior frontal sulcus

Frontal lobe

Central Sulcus

Parietal lobe

Occipital lobe

Cerebellar hemisphere

Lateral sulcus

Temporal lobe

Parietal lobe

Occipital lobe

Lateral sulcus

Temporal lobe

Cerebellar hemisphere

■ Figure 8.5 The cerebrum. (a) A lateral view and (b) a superior v

Longitudinal^ fissure

Central sulcus

Parietal lobe

Frontal poles

Superior frontal gyrus

Superior frontal sulcus

Central sulcus

Parietal lobe

Postcentral Gyrus Function Picture
Occipital poles

I Ffr Scientist have recently demonstrated that the brains of adult mammals (including humans) can produce new

__A ^ neurons. Neural stem cells, able to differentiate into new neurons and glial cells, have been obtained from the region immediately adjacent to the ventricles. The cells in this "subventricular zone" that function as neural stem cells may be ependyma and/or astrocytes. New neurons from this region have been found to migrate into the olfactory bulb (see fig. 8.14) and additional locations in the forebrain implicated in memory. Other experiments suggest that the hippocampus (see fig. 8.14), an area needed for encoding memories, may be able to generate new neurons throughout life. These findings have important implications for future attempts to regenerate damaged brain tissue or repair it with transplanted stem cells.

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