The neural code between neocortical pyramidal neurons depends on neurotransmitter release probability

Area of Science:

• Neuroscience
• Computational Neuroscience
• Synaptic Plasticity

Background:

• Neuronal signaling is fundamental to brain function, but the precise mechanisms by which synaptic transmission properties shape neural codes remain unclear.
• Understanding how information is encoded in the timing and rate of neural activity is a central challenge in neuroscience.

Purpose of the Study:

• To investigate how synaptic transmission properties, specifically synaptic depression, influence the encoding of information in neuronal firing rates and temporal patterns.
• To determine the role of neurotransmitter release probability in shaping the neural code transmitted across synapses.

Main Methods:

• Theoretical modeling of neuronal communication.
• Experimental patch-clamp recordings from pairs of neocortical pyramidal neurons.
• Analysis of the relationship between synaptic depression rates and the transmission of firing rate and temporal coherence information.

Main Results:

• The rate of synaptic depression, dependent on neurotransmitter release probability, significantly impacts whether postsynaptic neurons primarily receive information about firing rate or temporal coherence.
• Slow synaptic depression favors the transmission of firing rate information, while fast depression emphasizes temporal coherence.
• A diverse range of synaptic depression rates was observed, indicating a continuum in how rate and temporal signals are processed.

Conclusions:

• Neurotransmitter release probability, by modulating synaptic depression, is a critical determinant of the neural code.
• Synaptic depression acts as a flexible mechanism that adjusts the balance between rate and temporal coding in neural circuits.