What is the purpose of sensorimotor integration?
to filter out the noise from the relevant signal
noise - malfunctioning system, self-generated noise
background
What is a corollary discharge?
Efference copy
When making a movement we send a “prediction” of how its supposed to feel
Later when the movement is done we compare the predicted and the actual sensory input for discrepancy. If there is discrepancy, we adjust in new trial
What is a forward model of sensorimotor integration?
prediction of sensory input of a movement
What is an inverse model of sensorimotor integration?
reverse engineering the required movements to achieve the desired sensory consequences
Describe how sensorimotor integration works in ELL (electrosensory lateral line lobe) of a fish
ELL is like a cerebellum in humans
mossy fibers provide an efferent copy to granule cells that synapse on medial ganglion cell
actual sensory input also synapses on MG cell
MG cell integrates the inputs and outputs the error signal (if any). Motor command is adjusted for next time
Ideally the efference copy and the sensory input cancel each other out, meaning the prediction and the motor command were correct
this system is plastic and adapts to sensory input changes (input-specific plasticity)
What’s dysmetria?
over-/underreaching as a result to cerebellar damage
How does a mouse distinguish between self-generated and external sounds?
All auditory input goes to the cochlear nuclei. There, the dorsal cochlear nucleus is only sensitive to external, but not self-generated sound, while the ventral cochlear nucleus responds to both self-generated and external sound.
e.g. when the normally self-generated sound is played back to the mouse, both nuclei respond the same
Are the cerebellar projections ipsi/contraleateral to the cerebral cortex and the body?
Ipsilateral to the body
Contralateral to the cerebral cortex
What is ataxia?
Unsteadiness and incoordination, difficulty controlling force and timing of movements (cerebellar damage)
What’s hypotonia?
reduced resting muscle tension (cerebellar damage)
What are the cerebellar layers?
Outside-in:
1. Molecular layer
2. Purkinje layer
3. Granule layer
What cells are in the molecular layer of cerebellum? What do they do?
Purkinje cell dendrites and synapses with parallel fibers (from granule cells) (simple spikes)
Molecular layer interneurons (inhibitory):
- stellate cells (outside) -> synapse on Purkinje cell dendrites
- basket cells (inside) -> synapse on Purkinje cell soma
MLIs provide feedforward inhibition to Purkinje cells
What cells are in the Purkinje layer of cerebellum? What doe they do?
Purkinje cell bodies (inhibitory) -> integrate all inputs and output to deep cerebellar nuclei
Purkinje cells receive (excitatory) climbing fiber input from inferior olive (complex spikes) - provide error signal (involved in learning)
What cells are in the granule layer of cerebellum? What doe they do?
Granule cells (excitatory) -> receive (excitatory) mossy fiber input from pontine nuclei and synapse of purkinje cell dendrites in molecular layer (parallel fibers)
Golgi cells (inhibitory) -> receive inputs from parallel fibers and provide feedback inhibition to granule cells
From where do the deep cerebellar nuclei receive their input?
Inhibitory from purkinje cells
Excitatory from mossy and climbing fiber collaterals
Is there convergence or divergence between parallel fibers and purkinje cells?
convergence
Is there convergence or divergence between mossy fibers and granule cells?
divergence
Is there convergence or divergence between inferior olive and purkinje cells?
divergence
What are the firing properties of zebrin+ bands in the cerebellum? What type of plasticity is more prominent in those bands?
low firing rate
LTP is more prominent
What are the firing properties of zebrin- bands in the cerebellum? What type of plasticity is more prominent in those bands?
high firing rate
LTD is more prominent
What are the 3 main divisions of the cerebellum?
Cerebrocerebellum (hemispheres)
Spinocerebellum (vermis)
Vestibulocerebellum (Flocculus + nodulus)
What are the cerebellar peduncles? What is their function?
Superior -> primary output from cerebellum
Middle -> input to cerebellum from pons
Inferior -> input + output
What are the deep cerebellar nuclei?
Dentate
Interposed (x2)
Fastigial
From where does the cerebellum receive its inputs?
Frontal and parietal cortices -> pontine nuclei -> middle cb peduncle -> cerebrocerebellum
Vestibular nuclei -> inferior cb peduncle -> vestibulocerebellum
Inferior olive -> inferior cb peduncle -> all cerebellum
External cuneate nucleus -> inferior cb peduncle -> spinocerebellum
Clarke’s nucleus -> inferior cb peduncle -> spinocerebellum
Trigeminal nucleus -> inferior cb peduncle -> spinocerebellum
