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SOMATOSENSORY CORTEX

SOMATOSENSORY CORTEX. Learning Objectives. SOMATOSENSORY CORTEX Homunculus SOMATOSENSORY AREA I SOMATOSENSORY AREA II Somatosensory association area. Cerebral Cortex. Brodmann’s areas Fifty Histological ---- Functional General Scheme Central fissure

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SOMATOSENSORY CORTEX

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  1. SOMATOSENSORY CORTEX

  2. Learning Objectives • SOMATOSENSORY CORTEX • Homunculus • SOMATOSENSORY AREA I • SOMATOSENSORY AREA II • Somatosensory association area

  3. Cerebral Cortex • Brodmann’s areas • Fifty • Histological ---- Functional • General Scheme • Central fissure • Sensory signals from all modalities -Posterior • Anterior half parietal Lobe – Somatosensory signals – Reception and Interpretation • Posterior half – Still higher levels of interpretation

  4. Posterior half of frontal Lobe Muscle contraction & Body movements Sensory signals from all modalities- Posterior Anterior half parietal Lobe – somatosensory signals – reception and interpretation Visual signals- Occipital Lobe Auditory signals -Temporal Lobe

  5. SOMATOSENSORY AREA I Post central gyrus -cerebral cortex High degree of localization Extensive and more studied - more important Areas 3,1,2 SOMATOSENSORY AREA II Poor localization Less studied Signals enters here: From brainstem From somatosensory cortex From visual area From auditory area Somatosensory cortex

  6. Receive information from opposite side of body

  7. Structural layers of cerebral cortex I Molecular II Ext Granular III Small Pyramidal cells IV Int Granular cells V Large Pyramidal Cells VI Fusiform/Polymorphic cells layer

  8. Incoming signal excite neuronal Layer IV • Layers I and II receive diffuse, nonspecific input signals from lower brain centers • The neurons in Layers II and III send axons - the cerebral cortex • Layer V - Generally larger and project to more distant areas, such as to the basal ganglia, brain stem and spinal cord. • Layer VI, especially large numbers of axons extend to the thalamus, providing signals from the cerebral cortex

  9. Functions of somatosensory area I • Localize discretely- different sensations • Critical degrees of pressure • Weights of objects • Shape or form of objects -- Stereognosis • Texture of objects • Localizepain and temperature sensations

  10. Somatosensory association area • Brodmann’s area 5 and 7 • Parietal cortex - behind somatosensory area I • Decipher sensory information entering somatosensory area I • Receives signals from: • Somatosensory area I • Ventrobasal nuclei of thalamus • Other nuclei of thalamus • Visual and auditory cortices

  11. Effect of removing somatosensory association area • Unable to recognize complex objects/complex forms by feeling them on opposite side • Loses sense of form of his/her own body / body parts on opposite side • Oblivious to opposite side • Forgets to use opposite side for motor functions • Tends to recognize one side of object and forgets other side - Amorphosynthesis

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