The cerebral cortex represent in humans a highly developed structure concerned with the most
familiar functions we associate with the human brain.
It is the highly convoluted external surface of the brain. Its distinctive shape arose during
evolution as the volume of the cortex increased more rapidly than the cranial volume. This
differential rate of evolutionary development resulted in the convolution of the surface and the
folding of the total structure of the cortex.
The convolutions consist of grooves known as sulci that separate the more elevated regions
called gyri.
The cortex has been divided into four lobes using certain consistently present sulci as
landmarks. These lobes are named after the overlying cranial bones: frontal, parietal, temporal
and occipital.
The primary sensory areas (visual, auditory, somatic sensory and gustatory areas) receive
information from peripheral receptors with only a few synapses interposed. The primary visual
cortex is located at the caudal pole of the occipital lobe, mainly on its medial region. The primary
auditory cortex lies in the temporal lobe, where it includes a portion of the lower bank of the
lateral sulcus. The primary somatic sensory cortex lies on the postcentral gyrus.
On the other hand the primary motor cortex lies within the precentral gyrus and contains neurons
that project directly to the spinal cord. It mediates voluptuary movements of the limbs and trunk
because it contains neurons that projects directly to the spinal cord to activate motor neurons.
Surrounding the primary areas are the so called higher-order secondary and tertiary sensory and
motor areas. These areas integrate information coming from the primary sensory areas. In
contrast Higher order motor areas send complex information required for a motor act to the
primary motor cortex.
There are also three other large regions called association areas. These regions lie outside the
primary, secondary and tertiary. The association areas constitute, in primates, the largest area
of cortex.
The parietal-temporal-occipital association cortex occupies the interface of these three lobes. It
is concerned with higher perceptual functions related to somatic sensations, hearing and vision.
Information from these different sensory modalities is combined to form complex perceptions.
The prefrontal association cortex occupies most of the rostral part of the frontal lobe. An
important function of this area is the planning of voluntary movement.
The limbic association cortex is devoted mainly to motivation, emotion and memory; it is located
on the medial and inferior surfaces of the cerebral hemispheres in portions of the parietal
temporal and frontal lobes.
A close look to the cerebral cortex
Many areas of the cerebral cortex process sensory information or coordinate motor output
necessary for control of movement. These areas are divided into primary, secondary and tertiary
sensory or motor areas, due to the fact that some regions are more directly involved than others
with sensory or motor processing.