A dendrite-resolved, in vivo transfer function from spike patterns to dendritic Ca²

Area of Science:

• Neuroscience
• Cellular Electrophysiology
• Calcium Signaling

Background:

• Dendrites are crucial for neuronal computation, converting electrical activity into intracellular calcium (Ca2+) signals that regulate synaptic plasticity.
• The precise relationship between dendritic voltage changes and Ca2+ influx during natural behaviors is not well understood.

Purpose of the Study:

• To quantitatively map the voltage-to-Ca2+ transfer function across the dendritic arbor of hippocampal CA2 pyramidal neurons in behaving mice.
• To elucidate the mechanisms underlying dendritic Ca2+ signaling during natural behaviors.

Main Methods:

• Simultaneous in vivo imaging of voltage and Ca2+ signals throughout the dendritic arbors of CA2 pyramidal neurons in awake, behaving mice.
• Utilizing a biophysics-inspired computational model to predict local Ca2+ transients based on voltage waveforms.

Main Results:

• Dendritic Ca2+ activation followed a hierarchical pattern, primarily driven by back-propagating action potentials.
• Simple spikes mainly influenced somatic and proximal dendritic Ca2+ signals.
• Complex spikes elicited larger somatic Ca2+ signals and propagated further into distal dendrites, sometimes in a branch-specific manner.
• Dendrite-specific voltage and Ca2+ co-activation without concurrent somatic events was infrequent.

Conclusions:

• The study provides a quantitative understanding of dendritic Ca2+ dynamics in CA2 pyramidal cells during behavior.
• A biophysical model successfully predicted local Ca2+ transients from voltage signals, highlighting the importance of electrical activity in shaping Ca2+ responses.
• Findings clarify the conditions under which dendritic Ca2+ signals arise and contribute to neuronal function and plasticity in the hippocampus.