Primary motor cortex (M1) Flashcards
what is the organisation of M1
organised by body part
- larger representation for areas requiring fine, dextrous control (hands, face, lips, tongue, etc)
where is M1
caudal portion of frontal lobe
rostral to central sulcus
what are the inputs for M1
cortical structures
- S1 = somatosensory feedback
- SMA, PMv, PMd = planning related activity
what are the outputs from M1
descending motor tracts = to initiate and control voluntary motor actions (CSTs)
cerebellum = efference copy of motor signals during ongoing actions
basal ganglia = ongoing processing (recurrent connections)
what is the comparison of homunculus in S1 and M1
S1 = larger rep to regions with larger number of receptors
M1 = larger rep to regions that require more dextrous / fine control
ex: face, lips, hands, and tongue have large reps in S1 and M1
ex: feet have large rep in S1 but not M1 (large # of receptors but low motor dexterity)
what are focal reversible lesions
focal = specific to a certain area (doesn’t spread)
caused by muscimol injections
- GABA agonist that temporarily inactivates neurons and causes focal, reversible lesions
- used to provide a model to understand how brain regions contribute to mvmt
how do focal lesions show the importance of M1 in arm movements
large M1 lesions cause temporary or permananet paralysis affecting distal muscels of the proximal arm/trunk
- affects distal more because there is more dedicated rep in the homunculus (proximal areas have more overlap)
what occurs to M1 and CSTs during stroke
- reduction in density / thickness of CSTs
- clinical symptoms may be from damage to M1 ro white matter tracts that connect to the spinal cord
- degradation occurs when there is less input because they’re not useful
what is the UE-FM (upper extremity fugl meyr assessment score)
high score = low impairment (high functioning)
low score = high impairment (low functioning)
- negative correlation between lesion load and UE-FM
