Functional Areas of Cerebral Cortex

Functional areas of cerebral cortex Motor areas Primary motor area Brodmann’s area 4 Premotor area 6 Supplementary motor area (extrapyramidal center) 6 Site Precentral gyrus of lateral surface, Anterior part of paracentral lobule In front of area 4 Broad above narrow below Function Fine specific discrete movement mainly extremities - storing motor programs. - coordination of coarse movement mainly trunk, shoulders and hip muscles. - Inhibitory to muscle tone. - send input to area 4 Mostly on the medial - postural stabilization of frontal gyrus anterior to the body. paracentral lobule - coordination of both sides of the body. - control of sequences of movements. Lesion Contralateral hemiplegia (UMN syndrome) - motor apraxia - spasticity - loss of postural stability. Not definite Frontal eye field 8 In front of premotor area, mainly middle frontal gyrus. Connected to visual area in occipital lobe Broca’s area of speech (motor language area) 44,45 Inferior frontal gyrus Mainly on the left dominant hemisphere Voluntary tracking movement (conjugate movement) to the opposite side. Deviation of both eyes to same side of lesion. Coordination of muscles of Motor aphagia (nonlarynx, mouth, tongue and fluent/ expressive palate. aphagia): Connected to wernicke’s area Good comprehension, through arcuate fasciculus poor speech Sensory areas Primary sensory area Brodmann’s area 3,1,2 Site Postcentral gyrus, Extends on the paracentral lobule Function -Localize, discriminate different sensations. -Gives 20% of pyramidal tracts lesion Contralateral hemianesthesia Secondary sensory area Visual area 17 Lowermost part of postcentral gyrus (depth of lateral sulcus) Around calcarine sulcus Visual perception lips (cuneus above and lingual below) Receive visual radiation from LGN Primary auditory area 41, 42 Vestibular area Gustatory area Olfactory area 43 Middle of the superior temporal gyrus Perception and analysis of pitch, intensity of sound Superior temporal gyrus Equilibrium posterior part Inferior end of Taste perception postcentral gyrus + insula Uncus and adjoining Smell perception hippocampal gyrus (rhinencephalon) (uncus-piriform area) No marked lesion Contralateral homonymous hemianopsia with macular sparing Reduction of hearing acuity on both ears mainly on opposite side. Wernicke’s area (sensory language area) 22,39,40 Superior temporal gyrus of left dominant hemisphere, extending into posterior end of lateral sulcus into parietal lobe Receive fibers from visual and auditory areas Understanding written and spoken words, enables person to read and understand. Sensory aphagia (fluent/ receptive aphagia) Works in coordination with angular gyrus (39) and supramarginal gyrus (40). Association areas Visual association area Brodmann’s area 18, 19 Occipital eye field area Auditory association area 22 Site Function Lesion Remainder of cuneus and lingual gyri Interpretation of visual stimulus with past experience Rest of occipital lobe Reflex conjugate movement of both eyes to opposite side Interpretation of auditory Auditory (verbal/ stimulus acoustic) agnosia Back of superior temporal gyrus along with wernicke’s area Visual agnosia and color blindness Posterior parietal (somatosensory) association area Prefrontal association area 5,7 9,10,11,12 Greater part of frontal cortex Body image, know object by feeling it Astereognosis Judgment, foresight, personality - Alzheimer (amyloid degeneration. - Schizophrenia (low dopamine).