The cerebellum isn't known for generating voluntary movement (only coordinating it); the motor cortex is. But recent research is showing that the cerebellum and/or other subcortical areas might have a role in generating/modulating voluntary movement sequences through multi-synaptic connections, perhaps through the basal ganglia circuits. Here's a compelling new paper that has to do with this: http://www.cell.com/neuron/abstract/S0896-6273(15)00220-2.
And what's the difference between coordinating and initiating at the physiological level? I'm guessing initiating involves movement without a specific stimulus - i.e. the motor cortex just decides to take a seat or do push-ups; whereas coordinating involves a constant flow of input and output through the cerebellum. Is that correct?
Also, on a side note, cerebellum is involved in athletic conditioning, hand-eye coordination, and "muscle memory" - or most operant-conditioned and observational/social-learning-based tasks. Right? And the motor cortex would be involved in more "artistic" movement like in dance or gymnastics?
And what's the difference between coordinating and initiating at the physiological level? I'm guessing initiating involves movement without a specific stimulus - i.e. the motor cortex just decides to take a seat or do push-ups; whereas coordinating involves a constant flow of input and output through the cerebellum. Is that correct?
The cerebellum is, first and foremost, an error-correction machine. That's the classical view of the cerebellum and it's well-supported by the evidence we have. The mossy fibers carry sensory input to the parallel fibers, which eventually synapse onto Purkinje cells. Purkinje cells also receive a so-called "teaching signal" from the climbing fibers and perform the error calculation to correct your movement. This is a very simplified version of the cerebellar circuit, but it'll suffice for now. So say your motor cortex initiates some movement - moving your spoon to your mouth. Along with the motor signal to the descending motor pathways is sent an efferent copy of the motor command to the cerebellum. When your sensory input comes in - say your hand is moving the spoon towards your cheek instead of your mouth - the teaching signal causes a correction of the motor output so that you bring the spoon to your mouth. This is pretty new stuff and people are still debating whether/how the cerebellum exerts online control since the timescale of those signals is usually pretty slow. It might just be that the teaching signal corrects future versions of that command but not the command itself as it is occurring. But that's basically how the cerebellar circuit works.
Also, on a side note, cerebellum is involved in athletic conditioning, hand-eye coordination, and "muscle memory" - or most operant-conditioned and observational/social-learning-based tasks. Right? And the motor cortex would be involved in more "artistic" movement like in dance or gymnastics?
What recent evidence is suggesting is that the cerebellum and/or other subcortical areas are involved in crude motions - extension, flexion, extending the hand. The motor cortex seems to be involved in motor learning, or learning how to organize those crude, biologically-programmed movements into coherent sequences to solve some task. If you take a look at the paper I cited above, you should find a pretty satisfactory explanation of what motor cortex does and does not do.
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