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Lecture 17

Lecture 17 - Cortical Motor Areas

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University of Toronto St. George
Michelle French

PSY300H1F L17; Oct. 21, 2011 direct corticospinal synapses on motoneurons mostly Cortical Motor Areas to distal limb and speech motor nuclei at least of Higher Motor Centers connections on interneurons in spinal tract, so most ..moving beyond postural support connections not directly on motorneurons ex. Using limbs for things besides support Central sulcus dividing frontal from parietal Red nucleus 1 for distal limb movement programming Motor cortex area 4 on Rubro(red)spinal cells activate localized synergies, anterior bank of central especially in distal limbs and face preferentially, (other sulcus, down wall parts of body too) Bulge in motor cortex use distal limbs & face knob interesting ex. gripping & twisting movements of hands feature in most ppl, note contrast to reticulospinal & vestibulospinal tracts that where finger muscles organize widespread postural and locomotory synergies represented activate huge sets of muscles; red nuc focuses on Speech at bottom discrete muscles (like motor cortex) Biggest representations Section of midbrain; s. of speech & finger, most colliculus on top synergies, highest Aqueduct of silvius, receptor density just half shown Red nuc deep down in midbrain, large in humans, often overlooked when talk about motor system overtaken by motor cortex but still there, organizes more gross movements Rubrospinal tract descends, crosses almost immediately, to lateral funiculus in white matter, project to interneurons or directly to motorneurons Feet on medial walls btwn hemispheres; upside-down innervating distal representation of body muscles Knob, speech muscles at lateral side above lateral Synergy fissure Definition: grp of muscles contracting together for a Layer 5 pyr cells give rise to descending tract thru specific purpose bottom of midbrain and white matter underneath red ex. writing, holding a cup, playing instrument involve nuc, extends along bottom of medulla most axons dif combos of muscles cross over at lateral white matter down spinal cord synergies organized by reticulospinal tract are very Rubrospinal tract at same location, axons in widespread (typically cover half of body) for generating corticospinal grp, terminating in intermediate zone or support postures directly on motor nuc rubrospinal (and corticospinal) synergies are highly Some axons dont cross variable in ppl but never localized >15% of entire tract, in some ppl nothing probably depends on motor bhvrs the indiv trains Motor Cortex more space available so motor area took over here, Multiple Representation able to program more synergies; programs more recent every muscle has own motor nuc in spinal cord or uses of distant limbs; ex. Vocal apparatus for language brainstem Precentral gyrus front of central sulcus, extends to Single motor nuclei (muscles) represented in columns bottom of central sulcus at many loci in motor cortex that project to the motor somatotopic organization order or muscles nuc recpresented w feet medially, head laterally, so each muscle column is in a different neighborhood, representation upside-down like in S1 i.e. different adjacent columns layer 5 (output layer) pyramidal cells large; project to each cortical locus represents a different synergy; motor nuclei & interneurons in brainstem & spinal cord muscles which participate in most synergies have (corticobulbar(cortex to brainstem & motor nuc)/spinal biggest representation so whole synergy can be tract) long trajectory/axons, so need support so pyr activated together efficiently cells large
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