cerebellum and basal ganglia function Flashcards
control theory
a branch of engineering and mathematics that deals with dynamical systems (dynamical systems are
mathematical models of the behavior of a point over time.) a branch of engineering and mathematics that deals with dynamical systems (dynamical systems are
mathematical models of the behavior of a point over time.)
- Understand the difference between a feedback and feedforward controller, and the value of prediction in motor control
In the context of a thermostat: 1. feedback regulator: heater turns on when room drops below threshold, and cooler turns on when temp exceeds a threshold. Tends to be slow and attempts to speed it up cause oscillations (too hot to too cold). 2. Feedforward regulator: Uses sensory data to predict future states and preemptively counteracts temp change. (ie sensing variables such as how many windows are open, outside temp, etc). will acheive target value and stay there
Adaptive feedforward control
Uses sensory data to predict future states, but also generates a targeting error when things change so that next time it will be more effective.
What kind of control is the cerebellum
adaptive feedforward controller
How does a prism affecting reaching movement in a normal person and in someone with cerebellar damage
Predictions of system are no longer valid. Normal: CNS is able to adapt to the change in vision. Damaged: Can not adapt to the prism and will constantly point beyond the target.
What areas of brain are involved in estimating position of limb in space
Joint position is sent to primary somatosensory cortex in post central gyrus, and visual info is sent to occipital cortex
describe components of the “what” and “where” pathways
visual information goes to occipital cortex then can take two pathways. 1. The what pathway: info from occipital lobe is sent via ventral visual stream to inferior temporal lobe where object form is encoded. 2. The where pathway: info from occipital lobe is sent dorsally into parietal lobe where the location in space of visual stimuli is encoded
Role of parietal association cortex
In parietal association cortex, btw the “where” pathway and the joint position info from somatosensory cortex, the brain integrates visual information about the target (and limb position) and somatosensory information about the limb position, and this integrated information is fed to the premotor corticies in the frontal lobe to guide movement of the limb to the target.
Parietal association cortex internal model
This network contains an internal model of the system, which specifies certain predictions: for a given visual coordinate, the system predicts that certain joint angles
will achieve that locationThis network contains an internal model of the system, which specifies certain predictions: for a given visual coordinate, the system predicts that certain joint angles
will achieve that location
Describe cerebellar pathway connecting parietal and pre-motor cortices
parietal cortex > cortico-pontine fibers > synapse on ponto-cerebellar neurons (mossy fibers) > cross midline > synapse on contralateral cerebellar granule cells > parallel fibers synapse on purkinje cells > output to dentate nucleus > thalamus > motor and pre motor cortices
- Describe how the inferior olivary nucleus might contribute to joint position/ visual adaptation
Inferior olivary nucleus sends climbing fibers to purkinje cells and stimulation of these climbing fibers simultaneously with parallel fibers leads to changes in synaptic strengths of parallel-purkinje synapses, reconfiguring the network
What drives inferior olivary activity
GABAergic neurons from deep cerebellar nuclei
What kind of info does the inferior olivary nucleus receive
proprioceptive and visual feedback
How does the inferior olivary nucleus act as a comparator
It compares the expected state with observed state. If the proprioceptive and visual feedback are exactly
what the current parietal network would predict, then the reflection of the parietal network conveyed to the ION cancel out the proprioceptive and visual feedback, and no change in ION activity would result. If the feedback are different from expected, the ION will produce an error signal proportional to the magnitude of difference btw observed and expected states. It compares the expected state with observed state. If the proprioceptive and visual feedback are exactly
what the current parietal network would predict, then the reflection of the parietal network conveyed to the ION cancel out the proprioceptive and visual feedback, and no change in ION activity would result. If the feedback are different from expected, the ION will produce an error signal proportional to the magnitude of difference btw observed and expected states.
How is the error signal from inferior olivary nucleus conveyed
Error signal is carried by climbing fibers to the cerebellar cortex, where it initiates complex spikes in purkinje cells. The parallel fiber synapses on purkije cells that were active simultaneously with the climbing fiber-induced complex spike undergo a change in synaptic plasticity, termed Long Term Depression, leading to decrease in parallel fibers efficacy of firing the purkinje cell
Which cells in the cerebellar cortex and basal ganglia serve as pattern recognizers
cerebellar cortex: purkinje cels. Basal ganglia: medium spiny cells of striatum
- Understand the role that dopaminergic neurons in the Ventral Tegmental Area/substantia nigra play in conveying reward prediction errors to the striatum
When an unexpected reward is achieved (receiving ice tea after pressing a button), there is a spike in number of action potentials produced by dopaminergic neurons in SN and VTA. Eventually, the spike of dopaminergic neural activity will occr just when the button is seen, then eventually dopamine release will stop completely
describe the histochemical stain for Mu-opioid receptors of the striatum
Has patches that stain densely and a matrix that does not stain. Both the patch and matrix have medium spiny GABAergic neurons, but the matrix contains the neurons who project via the direct and indirect pathways.
Where do neurons in the “patch” of the striatum project
Directly to the substantia nigra/ ventral tegmental area dopaminergic neurons. They convey the current predictions about rewards
How is the substantia nigra/ ventral tegmental area a comparator
It detects mismatch btw observed and expected rewards. An unpredicted reward will strongly activated these neurons, and the dopamine released into the striatum will alter the activity and the plasticity of corticostriatal networks, such that networks that correctly predicted the error will be reinforced,
and those that do not correctly predict the error will be diminished.
- Describe similarities between the role the ION plays in modifying cerebellar circuitry and the role that VTA/SNc neurons play in modifying corticostriatal circuitry
Just as the ION acted as a comparator that was activated by a mismatch between observed and expected sensory feedback, the SNc/VTA acts as a comparator activated by a mismatch between observed and expected rewards.
Compare basal ganglia and cerebellum: source of error signal, return projection
Error signal: For the basal ganglia, the input from dopaminergic neurons provides the error signal; for the cerebellum it arises from neurons in the ION. Return projection: In the basal ganglia, return projection
comes to DA neurons from small groups of striatal medium spiny neurons in the patches or striosomes. In the cerebellum, this return projection comes to the ION neurons directly from the deep cerebellar nuclei or indirectly via the red nucleus
