cortexII.pdf - Cerebral Cortex II Where are the neuronal cell bodies located in the cerebral cortex(Hint think white versus gray matter Neocortex Neuron

cortexII.pdf - Cerebral Cortex II Where are the neuronal...

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Unformatted text preview: Cerebral Cortex II Where are the neuronal cell bodies located in the cerebral cortex??? (Hint: think white versus gray matter) Neocortex Neuron types—afferents to and efferents from cortical areas: Granular (stellate): - star shaped - “afferent projections” (input to the cortex) - within the cortex Pyramidal - pyramid shaped - “efferent projections” Organization: Horizontal laminar and Vertical columnar most “afferents” terminate in Horizontal laminar organization Six layers: I. Molecular: mostly dendrites and axons from inner cells thalamus: II. External granular: small granular and pyramidal neurons III. External pyramidal: small/ medium pyramidal neurons IV. Internal granular: closely packed granular neurons V. Internal pyramidal: large pyramidal neurons VI. Multiform (fusiform): many cell types most “efferents” arise from s.c. brainstem Figure 5-8 in Pritchard TC and Alloway KD (1999) Medical Neuroscience. Fence Creek Publ. p. 185. Vertical columnar organization cytoarchitecture/ chunks of neurons with similar function; functional organization (homunculus) - divergent pathways = can influence different areas - good for parallel processing - column size is experience dependent; changes with injury and earning (implications???) Projections classifications: Subcortical (projection fibers): impulses to/from subcortical areas (thalamus, brain stem, s.c.) Association: connect neurons within a hemisphere (ex: synergists share “rich” connections) Commissural: connect neurons to the contralateral hemisphere (ex: corpus callosum and commissures) Development Cell migration: - in to out (layer VI migrate first) - thalamic sensory neurons attach to cortical neurons sensory + motor = sensorimotor integration (dependent on: genetic factors and the environment) - complete before birth Neural Exuberance: “all over the place”; projections to many areas pro: has redundancy con: lacks precision Critical periods: an immature state of neural areas or projections; transformation: Regressive Events cell death- we lose about 50%of neurons during development axonal retraction synaptic retraction pruning- effective synapses ***Activity*** - neural darwinism- “competition” synapse strength, synaptic connections (wiring) (forms neural networks) - without may lead to regressive events REVIEW: 1. imagine you have a brain injury to the right primary and secondary somatosensory cortices. what major motor difficulty would you expect to see and where would it be? difficulties adjusting your grip in the left hand 2. which somatosensory cortical area receives most of its input information directly through the thalamus SI 3. T/F: horizontal layers of the neocortex are always parallel to a horizontal plane of the body false ...
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