Challenging the Point Neuron Dogma

Orateur : Alexandra TZILIVAKI (Einstein Center for Neurosciences, Charité Universitätsmedizin, Berlin, Germany)

Fast spiking basket cells constitute one of the main types of hippocampal and neocortical interneurons, controlling executive functions. However, most studies have focused on their molecular and anatomical features and supported the dogma that these cells integrate inputs like linear point neurons, completely ignoring potential dendritic influences. But exciting new findings reveal that the dendrites of interneurons may allow for a two-stage integration. To address this question, we developed biologically constrained biophysical models of basket cells using anatomical reconstructions of both hippocampal and cortical neurons. Synaptic stimulation within the dendrites predicts the co-existence of two distinct integration modes ; some dendrites exhibit supralinear synaptic integration while others operate in a sublinear mode. Morphological features influence the integration mode. By generating different spatial patterns of synaptic activation we find that spatially dispersed inputs lead to higher firing rates than inputs clustered within a few dendrites. Our findings challenge the current dogma, whereby interneurons are treated as linear summing devices, essentially void of dendrites. We predict that the dendrites of basket cells can operate in distinct non-linear modes. Thus, basket cells are better represented by a 2-stage integrator abstraction rather than a point neuron.

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