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Implications of variable synaptic weights for rate and temporal coding of cerebellar outputs
Shuting Wu1, Asem Wardak1, Mehak M Khan1
1Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA.
Biorxiv : the Preprint Server for Biology
|June 9, 2023
Summary
Single Purkinje cell (PC) synapses onto cerebellar nuclei (CbN) neurons exhibit significant size variability, impacting neuronal firing rates and timing. This variability allows for concurrent rate coding and precisely-timed responses in CbN neurons.
Area of Science:
- Neuroscience
- Synaptic transmission
- Cerebellar circuitry
Background:
- Purkinje cells (PCs) are inhibitory neurons projecting to cerebellar nuclei (CbN) neurons, crucial for motor control and learning.
- Current models suggest uniform PC inputs converge on CbN neurons to regulate firing through rate or timing codes.
- Individual PC influence on CbN neuron activity is traditionally considered limited.
Approach:
- Investigated the impact of synapse size variability on PC-CbN transmission using dynamic clamp and computational modeling.
- Analyzed how individual and synchronized PC inputs affect CbN neuron firing rate and precise timing.
- Examined the role of PC refractory periods in modulating CbN neuron activity.
Key Points:
- Single PC to CbN synapses display substantial variability in size.
- Variable synapse sizes dynamically regulate CbN neuron firing rates and timing.
- Large PC inputs can transiently suppress CbN firing, with a preceding brief excitation due to PC refractory periods.
- Increased inhibitory conductance variability due to synapse size differences elevates baseline CbN firing rates.
Conclusions:
- PC-CbN synapses are uniquely suited for conveying both rate-based information and generating precisely-timed outputs.
- Synapse size variability influences the impact of PC synchrony on CbN firing.
- Findings suggest broader implications for synaptic plasticity and information processing in other brain regions with variable synapses.
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