Fast dendritic excitations primarily mediate back-propagation in CA1 pyramidal neurons during behavior

Area of Science:

• Neuroscience
• Computational Neuroscience
• Cellular Neuroscience

Background:

• Dendrites integrate synaptic inputs and propagate back-propagating action potentials (bAPs) crucial for synaptic plasticity.
• The in vivo roles of nonlinear dendritic excitations in integration and bAP propagation remain unclear.

Purpose of the Study:

• To investigate the in vivo roles of dendritic nonlinearities in CA1 neuron integration and back-propagation.
• To map dendritic membrane potential dynamics in CA1 neurons during virtual navigation.

Main Methods:

• High-speed voltage imaging using a chronically implanted microprism in mice.
• Mapping membrane potential dynamics across basal and apical dendrites of CA1 neurons.
• Utilizing a virtual reality environment for behavioral control.

Main Results:

• Dendritic excitability dynamics were largely captured by basal, soma, and apical compartments.
• Fast dendritic spikes initiated from bAPs, indicating they are consequences, not causes, of somatic spiking.
• Dendritic excitability biophysics determined the distribution of simple and complex spikes within a place field.

Conclusions:

• Dendritic spikes are primarily a consequence of somatic spiking, not the cause.
• Dendritic nonlinearities play a key role in converting synaptic inputs to spiking outputs in CA1 pyramidal neurons.
• Dendritic nonlinearities are suggested to mediate activity-dependent plasticity.