Excitatory Cerebellar Nucleocortical Circuit Provides Internal Amplification during Associative Conditioning

Area of Science:

• Neuroscience
• Cerebellar Function
• Motor Learning

Background:

• The role of closed-loop circuits in the cerebellum is not fully understood.
• Internal feedback from cerebellar nuclei to the cortex is a key area for investigation.

Purpose of the Study:

• To investigate the function of internal feedback from cerebellar nuclei to the cerebellar cortex.
• To elucidate the role of this circuitry in classical eyeblink conditioning.

Main Methods:

• Characterization of nucleocortical pathways in classical eyeblink conditioning.
• Optogenetic activation and inhibition of nucleocortical fibers.
• Analysis of mossy fiber terminal density.

Main Results:

• Excitatory output neurons in the interposed nucleus send efference-copy signals via mossy fibers.
• These signals trigger responses in granule and Golgi cells, and inhibit Purkinje cells.
• Conditioning increases nucleocortical mossy fiber terminal density, and manipulating this pathway alters learned eyeblink responses.

Conclusions:

• The cerebellum's nucleocortical closed-loop circuitry relays corollary discharge of premotor signals.
• This circuitry plays an amplifying role in associative motor learning.