Higher Motor ControlHigher Motor Control2nd ed: Ch 5: cerebellum (152), basal ganglia 2nd ed: Ch 5: cerebellum (152), basal ganglia

(157), supplementary motor area (162), (157), supplementary motor area (162), parietal lobes (167).parietal lobes (167).

Apraxia: Gazzaniga et al, Apraxia: Gazzaniga et al, Cognitive Cognitive NeuroscienceNeuroscience, pp. 401-404., pp. 401-404.

Major Brain RegionsMajor Brain Regions

CorticalCortical::

A.A. Primary motor cortexPrimary motor cortex

B.B. Secondary motor cortexSecondary motor cortex(supplementary motor area + pre-motor cortex)(supplementary motor area + pre-motor cortex)

C.C. Left parietal lobeLeft parietal lobe

SubcorticalSubcortical::

D.D. Basal GangliaBasal Ganglia

E.E. CerebellumCerebellum

Cortical Motor RegionsCortical Motor Regions

A. Primary Motor CortexA. Primary Motor Cortex

• Provides primary motor signal from Provides primary motor signal from cortexcortex

• Selects which muscle groups to move, Selects which muscle groups to move, and how forcefullyand how forcefully

• Damage: weakness or paralysis in Damage: weakness or paralysis in corresponding region, imprecision of corresponding region, imprecision of fine motor movementsfine motor movements

A. Primary Motor CortexA. Primary Motor Cortex

Mrs. AL: AL suffered a stroke which affected the left Primary Motor Cortex in Mrs. AL: AL suffered a stroke which affected the left Primary Motor Cortex in

the region corresponding to the right hand. "At first, I couldn't use the hand at the region corresponding to the right hand. "At first, I couldn't use the hand at

all, it was as if it was paralysed. Then slowly, I started to get it to move. Now, I all, it was as if it was paralysed. Then slowly, I started to get it to move. Now, I

can use it to do some simple things, like helping me put on my hat, but I don't can use it to do some simple things, like helping me put on my hat, but I don't

seem to have any strength in it, and I can't do anything very sophisticated. I seem to have any strength in it, and I can't do anything very sophisticated. I

dropped my wallet so many times trying to open it that I now use a pouch on dropped my wallet so many times trying to open it that I now use a pouch on

string which I carry around my neck. But the hardest part was learning to write string which I carry around my neck. But the hardest part was learning to write

with my left hand. I still can't write anything at all with the bad hand. With the with my left hand. I still can't write anything at all with the bad hand. With the

left, I now write simple shopping lists and sign my name but my writing looks left, I now write simple shopping lists and sign my name but my writing looks

babyish and clumsy". babyish and clumsy".

B. Secondary Motor CortexB. Secondary Motor Cortex

• Involved in generating plans for complex activitiesInvolved in generating plans for complex activitiese.g. novel movements, movement sequencese.g. novel movements, movement sequences

• Also involved in “control” - selecting amongst Also involved in “control” - selecting amongst competing motor planscompeting motor plans

= Supplementary Motor Area + Pre-Motor Cortex= Supplementary Motor Area + Pre-Motor Cortex

Supplementary motor area

Pre-motor cortex

B. Secondary Motor CortexB. Secondary Motor CortexDamageDamage: :

1.1. can't perform complex tasks (sequencing errors)can't perform complex tasks (sequencing errors)• e.g. placing match to candle before lighting ite.g. placing match to candle before lighting it

2.2. difficulties with bimanual coordination:difficulties with bimanual coordination:

B. Secondary Motor CortexB. Secondary Motor Cortex

• 3.3. externally-driven movement selection: externally-driven movement selection:

As part of a case presentation to staff at a rehab hospital, Mrs. J As part of a case presentation to staff at a rehab hospital, Mrs. J

was interviewed by the charming and handsome neurologist Dr. was interviewed by the charming and handsome neurologist Dr.

C. During the interview, her right hand would repeatedly come C. During the interview, her right hand would repeatedly come

to rest on Dr. C.'s left knee, much to her own amusement and to rest on Dr. C.'s left knee, much to her own amusement and

that of the staff. She insisted that she had no control over this that of the staff. She insisted that she had no control over this

gesture - that it was like her hand had "a mind of its own!"gesture - that it was like her hand had "a mind of its own!"

Damage (cont.)Damage (cont.): :

C. Left Parietal LobeC. Left Parietal Lobe

• Storage/retrieval of commonly-used complex action programsStorage/retrieval of commonly-used complex action programs

e.g. turning key in a locke.g. turning key in a lock

• Also needed for planning novel sequences, esp. those Also needed for planning novel sequences, esp. those

comprising familiar movementscomprising familiar movements

C. Left Parietal LobeC. Left Parietal Lobe

A patient with bilateral lesions of the parietal lobes was unable to continue her A patient with bilateral lesions of the parietal lobes was unable to continue her

work as a fish filleter. When attempting to perform a routine that she had work as a fish filleter. When attempting to perform a routine that she had

completed thousands of times, she correctly inserted the knife point into the head completed thousands of times, she correctly inserted the knife point into the head

of the fish, began the first stroke, but then stopped. She claimed to know how the of the fish, began the first stroke, but then stopped. She claimed to know how the

action should be completed but could not execute it. At home, she found herself action should be completed but could not execute it. At home, she found herself

putting the sugar bowl in the refrigerator or the coffee pot in the oven.putting the sugar bowl in the refrigerator or the coffee pot in the oven.

Damage = Damage = apraxiaapraxia (or "limb apraxia"): (or "limb apraxia"):

• inability to perform familiar, well-learned routinesinability to perform familiar, well-learned routines

• object use errorsobject use errors

• also problems with novel movementsalso problems with novel movements

C. Left Parietal LobeC. Left Parietal Lobe

Object use errors: most clearly seen when P must perform on Object use errors: most clearly seen when P must perform on command and/or without object as promptcommand and/or without object as prompt

e.g. e.g. Body-part error:Body-part error:

C. Left Parietal LobeC. Left Parietal Lobe

May also make errors in novel sequences (e.g. May also make errors in novel sequences (e.g. perseverationsperseverations))

C. Left Parietal LobeC. Left Parietal Lobe

• Left parietal lobe and Left parietal lobe and

Secondary motor cortex - Secondary motor cortex -

damage produces some damage produces some

similar featuressimilar features

-> both regions may work -> both regions may work

together to retrieve and together to retrieve and

execute complex routinesexecute complex routines

D. Basal GangliaD. Basal Ganglia

• Loop-like connections to motor cortex; regulates Loop-like connections to motor cortex; regulates activity in motor cortexactivity in motor cortex

• Ensures that only the most highly activated motor Ensures that only the most highly activated motor plan/signal is executedplan/signal is executed

• Rich in dopaminergic neuronsRich in dopaminergic neurons

D. Basal GangliaD. Basal Ganglia

• Important when a new movement plan is required:Important when a new movement plan is required:

- commencing a new motor activitycommencing a new motor activity

- ceasing a current motor activityceasing a current motor activity

• Also involved in setting postureAlso involved in setting posture

D. Basal GangliaD. Basal Ganglia

• depletion of dopaminergic neurons in BG - motor signals from cortex are depletion of dopaminergic neurons in BG - motor signals from cortex are overinhibitedoverinhibited

• difficulty initiating movement (“hypokinesia”)difficulty initiating movement (“hypokinesia”)

• movements are slowed (“bradykinesia”)movements are slowed (“bradykinesia”)

• external cues may help to overcome:external cues may help to overcome:

"First the feet freeze and feel as if they are glued to the ground. When you "First the feet freeze and feel as if they are glued to the ground. When you

eventually get going, the top half of the body seems to go faster than the bottom eventually get going, the top half of the body seems to go faster than the bottom

and you end up running and sometimes the only way to stop is to run into and you end up running and sometimes the only way to stop is to run into

something. This can often lead to bumps and bruises. Some patients often find it something. This can often lead to bumps and bruises. Some patients often find it

easier to go up and down stairs or to step over objects. It often helps to imagine easier to go up and down stairs or to step over objects. It often helps to imagine

there is something on the ground in front of you and you have to step over it."there is something on the ground in front of you and you have to step over it."

Parkinson’s diseaseParkinson’s disease

D. Basal GangliaD. Basal Ganglia

Huntington’s ChoreaHuntington’s Chorea::

• Atrophy of Basal GangliaAtrophy of Basal Ganglia

• Reduced output from BG means reduced inhibitory control Reduced output from BG means reduced inhibitory control over motor signals from cortexover motor signals from cortex

• Involuntary movements (”chorea”)Involuntary movements (”chorea”)

E. CerebellumE. Cerebellum

• Loop-like connections to other motor areas; also receives Loop-like connections to other motor areas; also receives somatosensory info. somatosensory info.

• Fine-tuning and timing of movementsFine-tuning and timing of movements

-> Esp: fast, precise actions (ballistic movts), actions -> Esp: fast, precise actions (ballistic movts), actions requiring continuous feedbackrequiring continuous feedback

• Damage:Damage:- "drunken" gait"drunken" gait- slurred speechslurred speech- action tremor, esp. when reaching (ataxia)action tremor, esp. when reaching (ataxia)- ballistic movt errors (overshooting target)ballistic movt errors (overshooting target)- time judgementstime judgements

Functional Map of Motor RegionsFunctional Map of Motor Regions

Secondary Secondary Motor CortexMotor Cortex

Left Parietal Left Parietal LobeLobe

Primary Motor Primary Motor CortexCortex

Basal Basal GangliaGangliaCerebellumCerebellum

BrainstemBrainstem

Spinal CordSpinal Cord