One can distinguish several areas in the cerebral cortex with limits and functions relatively well defined. In the figure at left, they are identified with different colors, for the sake of explanation.

The difference between them resides in the thickness and composition of cell layers and the quantity of nervous cells arriving or departing from each layer.

Although the nervous system works as a wholy integrated entity, some cerebral areas are more directly responsible for certain functions. Thus, we can distinguish the main motor area, the main sensitive area, the centers responsible by vision, hearing, touch, olfaction, taste and so forth.

Cortical Area	Function
Primary Motor Cortex (in red)	Initiation of voluntary movement
Primary Somatosensory Cortex (in dark blue)	Receives tactile information, pain, pressure, position and moviment and temperature
Prefrontal Cortex (in pink)	Planning, emotion, judgment
Motor Association Cortex (Premotor Area) (in green)	Coordination of complex movements
Speech Center (Broca's Area) (in black)	Speech production and articulation
Auditory Cortex (in brown)	Auditory perception and hearing
Auditory Association Area (in light blue)	Complex processing of auditory information
(in yellow)
> Visual Association Area (in orange)	Complex processing of visual information
Visual Cortex (in dark green)	Primary visual perception
Wernicke's Area (in light green)	Comprehension of spoken language

The association areas. are important for the maintenance of higher mental activities in man, although it is not possible to localize any specific mental faculty or fraction of conscious experience. Aphasias, or speech defects resulting from cortical lesions illustrate the significance of association areas. In right-handed individuals these are produced by lesions in the left hemisphere (the dominant hemisphere).

Contd. The External Architecture of the Brain
By: Silvia Helena Cardoso, PhD
In: Brain & Mind