Function/dysfxn of cerebellum and BG [3] PD DRUGS [3] Flashcards
The cerebellum is an example of an ________ control
adaptive feed forward control
- deals with predictions
- create adaptation and the post adaptation after effect
- significant cerebellar lesion fails to show post adaptation after effect with stim removed
Info is first processed in the occipital cortex, and divided into two major streams of info:
- neurons represent which form
- name that pathway (what vs where)
- Ventral cortical areas
- from occipital lobe → inferior temporal lobe
- neurons represent object form
- “what” pathway - Dorsal
- from occipital → parietal lobe
- neurons encode locations in space
- “where” pathway
Parietal cortex fxn
conveys the joint angel calculations to the premotor cortices (Broadmanns area 6)
- calculates the diff between current and desired location and issues the command for the desired changes in joint angles to primary motor cortex to accurately target the effector
- change in network is stored in parietal and premotor cortices. Only the period of adaptation depends on the cerebellum.
What drives the inferior olivary activity?
GABAergic outputs with the GABAergic neurons projecting to the ION
ION receives proprioceptive and visual feedback
If the proprioceptive and visual feedback (from deep nuclei) are exactly what the current parietal network would predict, then the reflection of the parietal network conveyed to the ION would cancel out the proprioceptive and vidual feedback, and no change in ION activity would result.
ION is a comparator
ION acted as a comparator that was activated by mismatch btween observed and expected sensory feedback. What acts as a comparator activated by mismatch btwn observed and expected rewards?
SNc/VTA
- Unpredicted rewards → activate these neurons and release DA into striatum → alter corticostriatal networks
- correctly predicted error reinforced, incorrectly predicted error will be diminished
- Eventually DA will be released at the time of stimulus presentation (stim. predicts the reward), instead of receipt of reward leading to DA release.
What two systems function as “critics” of the cortico-striatal and parallel purkinje networks?
SNc
ION
Error signal inputs:
- Input from Dopaminergic neurons (SNc) provides error signal to BASAL GANGLIA
- ION Neurons input into cerebellum
Return projections though to carry prediction signals (PREDICTION ERRORS), and and DA and IOn neurons compute error between that prediction and the inputs that actually occur (thus acts as comparators)
Difference between Basal Ganglia and Cerebellum in predicting neural signals
*note that the validity of the neural signals are evaluated at a comparator (SNc+ION)
Basal ganglia: predicts input that produce + biological value (nutrients)
Cerebellum: predicts neural signals that are imp in producing and adjusting reflexes and other motor commands
Carbidopa
decarboxylase inhibitor - use with L-DOPA
blocks decarboxylase in the intestine, liver (where most L-DOPA is decarboxylated)
(note that DDC converts L-DOPA to DA)
DA receptor agonist (D2) in Caudate/putamen
Bromocriptine Pergolide Cabergoline Pramipexole Ropinirole
Amantadine
facilitates DA release
Anticholinergics
Trihexyphenidyl
Benztropine
Diphenhydramine (benadryl)
Selegiline
MAO-B inhibitor (prev DA breakdown)
ComT-I
Tolcapone
Entacapone
(prev DA breakdown, sim to selegiline)
Why do you need anticholinergic drugs in PD?
Balance the overactivity of the cholinergic interneurons in the caudate/putamen caused by lack of DA
*note that DA normally is inhibitory to cholinergic interneurons.
Anticholinergic effects
No pee, no see, no spit, no shit
