Cerebellar interneurons control fear memory consolidation via learning-induced HCN plasticity

Area of Science:

• Neuroscience
• Cellular and Molecular Neuroscience

Background:

• Synaptic plasticity underpins learning and memory.
• Neuronal intrinsic excitability modifications can alter circuit output and behavior.
• Mechanisms of learning-induced intrinsic excitability changes during memory formation are not fully understood.

Purpose of the Study:

• Investigate the role of cerebellar molecular layer interneurons in fear memory.
• Elucidate the mechanisms of learning-induced changes in neuronal intrinsic excitability.
• Determine the contribution of hyperpolarization-activated cyclic nucleotide-gated (HCN) channels and endocannabinoid signaling to fear memory.

Main Methods:

• Fear conditioning paradigm in rodents.
• Silencing of cerebellar molecular layer interneurons.
• Electrophysiological recordings to assess neuronal excitability.
• Measurement of endocannabinoid and cGMP levels.

Main Results:

• Silencing molecular layer interneurons abolished fear memory, highlighting their essential role.
• Fear conditioning induced a lasting reduction in HCN channels in these interneurons.
• This HCN channel reduction increased intrinsic membrane excitability and synaptic response.
• HCN channel loss was mediated by decreased endocannabinoid levels via altered cGMP signaling.
• Increased cerebellar endocannabinoids during memory consolidation prevented HCN plasticity.

Conclusions:

• Cerebellar interneuron activity drives fear memory formation through learning-specific increases in intrinsic excitability.
• This process critically depends on the downregulation of endocannabinoid-HCN signaling.
• Modulation of intrinsic excitability is a key mechanism in memory consolidation.