The Sensory Areas Of Cerebral Cortex

1. The somesthetic area.
2. The visual area.
3. The auditory area.
   4. The olfactory area.

The first three areas are found in the neopallium while the forth is situated in the archipallium.

The somesthetic area : This receives impulses from the skin concerned with touch, warmth, cold and the localisation of pain, impulses concerned with taste, and impulses from muscles, tendons, and joints concerned with proprioceptive sensibility (muscle sense). the principal experimental methods of studying the location bf this area are :

1. A) Electrical stimulation of the cortex exposed under local anesthesia in concious human patients.
2. 
   B) The local application of strychnine to various regions of the exposed cortex, following which the animal bites, scratches, or otherwise signals the skin area to which the sensations aroused in the cortex are projected.
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   C) Detection of electrical changes, of the cortical area which receives afferent impulses from touch or pressure receptors in the skin.

In primates the body sense area is located in the posterior central gyrus, but it extends into the motor area as well. Stimulation of the somesthetic area in man usually gives projected sensations: touch and movement without actual motor response. Sensations warmth and cold are unusual.

 Visual area: The fibres of the optic radiations arise in of the thalamus and pass to the occipital part of the cortex, in which the visual area is located. Into this area these fibers pour impulses that call forth visual sensations.

The fibers of the optic nerve originate from the cells of the retina. Most of them end in the latera1 geniculate body, from which the path is continued to the visual area of the cerebral cortex.

The auditory area : This is located in the temporal lobe, receives the fibers of the auditory radiations from the medial geniculate body of the thalamus Nerve impulses giving rise to auditory sensations are received in this area.

The fibers of the cochlear nerve — the nerve of hearing — originate in the spiral ganglion of the organ of corti and end in the cochlear nuclei of the pons. From these nuclei, fibers pass to the medial geniculate body of the thalamus In addition; important auditory reflex connections exist in the inferior colliculus, which are also included within the tecto-spinal tract.

Olfactory Area:  The centre of smell is situated in the uncus and the anterior part of the hi1ppocampal gyrus Owing to the close relationship of this part to the temporal lobe, lesions of the latter (tumour, abscess etc.) are commonly associated with disturbances of the olfactory lobe. It receives projection fibres from the secondary olfactory centre at the base of the olfactory bulb.

The fibers of the olfactory nerve originate from nerve cells located in the olfactory mucous membrane and terminate in the primary olfactory centre, which is situated in the olfactory bulb. This primary centre is in connection with the secondary olfactory centre.