The structure and functional localization of the cerebral cortex II

Motor & Sensory homunculus on the precentral gyrus

Motor homunculus

Sensory homunculus

Association cortex

1^stry motor & 1^stry sensory areas are only account for small percentage of cortical surface area
There are large remaining areas in the cortex called association areas
There are 3 main association areas
1. Prefrontal
2. Anterior temporal
3. Posterior parietal

Association area	Function
Prefrontal cortex	Associate experiences to Abstract ideas Produce judgments Emotional feelings Personality
Anterior temporal cortex	Store previous sensory experiences
Posterior parietal cortex	Stereognosis – The ability to recognize the 3D shape of an object by touch alone

Cerebral dominance

The 2 hemispheres of the newborn have the same capabilities
During childhood, one hemisphere slowly comes to dominate the other (Only after the 1^st decade that the dominance becomes fixed)
That’s why a 5 years old child with a damaged dominant hemisphere can easily learn to become left handed & speak well; whereas in the adult this is almost impossible

Nervous activities performed predominantly by dominant & non dominant hemispheres

Main anatomical connections of the cerebral cortex

Function	Origin	Cortical area	Destination
Sensory
Somatosensory Most to contra lateral side of body Oral to same side Pharynx, larynx & perineum bilateral	Ventral posterior lateral & VP medial nuclei of the thalamus	1stry somesthetic area (B 3, 2, & 1) – posterior central gyrus	2ndry somesthetic & 1stry motor areas
Vision	Lateral geniculate body	1stry visual area (B 17)	2ndry visual area (B 18 & 19)
Auditory	Medial geniculate body	1stry auditory area (B 41 & 42)	2ndry auditory area (B 22)
Taste	Nucleus solitarius	Posterior central gyrus (B 43)
Smell	Olfactory bulb	1stry olfactory area	2ndry olfactory area (B 28)
Motor
Fine movements Most to contra lateral side of body Extra ocular muscles, upper face, tongue, mandible & larynx are bilateral	Thalamus Cerebellum Basal ganglia Somatosensory area Pre motor area	1stry motor area (B 4)	Motor nuclei of brain stem & anterior horn cells of spinal cord

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