Goetz, L., Roth, A., & Häusser, M. (2021). Active dendrites enable strong but
sparse inputs to determine orientation selectivity. Proceedings of the National Academy of
Sciences, 118(30). https://www.pnas.org/content/118/30/e2017339118.short
Compartmental modeling constrained by in vivo dendritic recordings
Mouse primary visual cortex (V1) Layer 2/3 pyramidal neuron
A fundamental open question in neuroscience is the importance of active dendritic
conductance (leading to local dendritic spikes) to the tuning properties of neurons. The authors
create a compartmental model of a layer 2/3 pyramidal neuron in mouse visual cortex and a
model of its synaptic input (based on previous in vivo experiments) to explore this question.
Authors used algorithmic criteria to identify the spatial and temporal extent of key events such
as Na+ and NMDA dendritic spikes as well as somatic and back propagating action potentials.
This model was tuned to replicate key experimental findings. Exploring the model, authors
conclude that: “Our model provides a mechanistic explanation for how narrowly tuned
orientation-selective responses can arise from dendritic integration of weakly tuned synaptic
input: a few strong synapses, which provide input from similarly tuned presynaptic neurons,
preferentially trigger dendritic spikes. Dendritic spikes in turn are more narrowly tuned to
orientation than the synaptic input and efficiently drive the majority of somatic AP output. Thus,
by triggering dendritic spikes, a small subset of strong synapses drives amplification of
orientation-selective signals, effectively determining the tuning of neuronal output.”
“[W]e provide a quantitative account of the relationship between synaptic inputs,
nonlinear dendritic events, and action potential output. We developed a detailed pyramidal
neuron model constrained by in vivo dendritic recordings. We drive this model with realistic input
patterns constrained by sensory responses measured in vivo and connectivity measured in
vitro. We show mechanistically that under realistic conditions, dendritic Na+ and NMDA spikes
are the major determinants of neuronal output in vivo.”