Intrinsic persistent firing in CA1 encodes elapsed time across behaviorally relevant scales

Area of Science:

• Neuroscience
• Cellular Neuroscience
• Systems Neuroscience

Background:

• Temporal relationships are vital for learning, prediction, and episodic memory.
• Hippocampal time cells and entorhinal temporal context cells are known in vivo.
• The intrinsic capacity of single neurons to encode elapsed time independently of synaptic input remains unclear.

Purpose of the Study:

• To investigate whether single neurons possess intrinsic mechanisms for sustained temporal representation over multi-second intervals.
• To determine if these intrinsic mechanisms operate independently of synaptic drive.

Main Methods:

• Whole-cell patch-clamp recordings were performed in rodent hippocampal CA1 slices.
• Recordings were conducted under conditions of synaptic blockade.
• Neurons were stimulated with a brief current pulse to observe their firing rate dynamics.

Main Results:

• Many recorded neurons displayed exponentially decaying firing rates after stimulation.
• The time constants of these decaying rates showed a broad distribution, extending to tens of seconds.
• This demonstrates intrinsic neuronal properties capable of encoding time over behaviorally relevant scales.

Conclusions:

• Single neurons possess intrinsic cellular mechanisms for encoding temporal information over multi-second intervals.
• These findings suggest a potential cellular substrate for temporal coding in the brain, independent of network activity.
• This intrinsic capability spans over an order of magnitude of time, supporting complex temporal processing in memory and cognition.