Sensorimotor Dysfunction Flashcards
What is the hierarchical organization of motor system (top to bottom)?
- Association cortex
- Secondary motor cortex
- Primary motor cortex
- Brainstem motor nuclei
- Spinal motor circuits
**in parallel managing timing, sequence = basal ganglia & cerebellum
What is the function of the hierarchical motor system (top to bottom)?
- abstract plan/initial drive to move
- refining movement design
- specific motor sequence
what changes in the brain occur when there is movement practice?
- response chunking = sequence treated as a unit
- shifting control to lower levels = can operate without higher control
What are the 2 major areas of sensorimotor association cortex?
- Posterior parietal association cortex
- Dorsolateral prefrontal association cortex
What is evidence of function in posterior parietal association cortex?
integrates info about current position of body w/ info abt external objects you may act upon
stimulation can make patient feel like they are performing action
What is evidence of function in dorsolateral prefrontal association cortex?
decision making:
evaluation of external stimuli & initiation of voluntary reactions
involved in cognition
What are consequences of damage in posterior parietal association cortex?
- Contralateral Neglect: dysfunction of attention (right hem)
- Apraxia: inability to perform purposeful movements or gestures (planning/execution issue, left hem, bilateral symptoms)
** apraxic error –> imitation of gesture, performance of gesture on command, use of tools & objects in unusual contexts
What is the defining behaviour of a mirror neuron?
they activate when they watch someone perform an action and also when they perform the action
Where are mirror neurons located in the brain?
ventral premotor cortex (& other areas, ie. hippocampus)
What is organization of the Secondary Motor Cortices?
8 areas of secondary motor cortex (premotor, supplemental, cingulate)
What is the organization of the Primary Motor Cortex?
Somatotopically organized (Penfield)
What is evidence of function in secondary motor cortices?
produce & guide complex movements in space
What is evidence of function in primary motor cortices?
movement
What are consequences of damage in primary motor cortex?
- disrupt person’s ability to move 1 body part independently
- may produce astereognosia
- may reduce speed, accuracy, and force of movements
What are the roles of the cerebellum?
- receiving inputs (from primary & secondary motor cortex, info abt descending motor signals from brain stem nuclei, feedback from motor responses via somatosensory & vestibular systems)
- compares intended movements - actual movements
- critical for timing & sequence of movement
What are consequences of damage to the cerebellum?
- loss ability to precisely control direction, force, velocity, amplitude of movements
- loss ability to adapt patterns of motor output to changing conditions
- difficulties in maintaining steady postures
- impairments in learning of new motor sequences
- impairment on attention & executive control, procedural/working memory, language, visual-spatial processing
What are the 2 pathways of the basal ganglia & briefly describe?
- STOP pathway: at rest, basal ganglia inhibit motor/premotor area = no movement
- GO pathway: to activate must inhibit inhibition (disinhibition) via dopamine signalling from substantia nigra
In Parkinson’s Disease, what pathway is used more/less?
more STOP, less GO
In Huntington’s disease, which pathway is used more/less?
STOP used!
What is Parkinson’s Disease?
dopaminergic neurons of substantia nigra die
results -> diminished movement (particularly movement initiation)
initial symptoms: stiffness, resting tremor (during inactivity)
later symptoms: muscular rigidity, slow movement, “mask like” face, pain, depression
What are 2 treatments for parkinson’s disease?
- L-DOPA
- Deep brain stimulation pf substantia nigra
What is Huntington’s Disease?
decreases tonic inhibition (STOP) leading to excessive movement
rare & highly genetically determined.
no strong treatment options
