Dudai, A. | Search bioRxiv

bioRxiv2020

Morphometric reconstructions atlas shows insult-driven plasticity in cortical VIP/ChAT interneurons

We developed an automatic morphometric reconstruction pipeline, Pop-Rec, and used it to study the morphologies of cortical cholinergic VIP/ChAT interneurons (VChIs). Cholinergic networks control high cognitive functions, but their local modulation and stress-driven plasticity patterns remained elusive. Reconstructing thousands of local VChIs registered to their exact coordinates in multiple cleared murine cortices highlighted distinct populations of bipolar and multipolar VChIs which differed in their dendritic spatial organization. Following mild unilateral whisker deprivation, Pop-Rec found both ipsi-and contra-lateral VChI dendritic arborization changes. Furthermore, RNA-seq of FACS-sorted VChIs showed differentially expressed dendritic, synapse and axon-modulating transcripts in whisker-deprived mice. Indicating novel steady-state morphological roles, those genes also clustered distinctly in naive single cell VChIs. This VChIs "morpheome" atlas is the first example of unbiased analysis of neuronal populations and holds the possibility to compare neuronal structure-function relationships across experimental conditions.

neuroscience↗

bioRxiv2020

Synthesis of higher order feature codes through stimulus-specific supra-linear summation

How cortical circuits build representations of complex objects is poorly understood. The massive dimensional expansion from the thalamus to the primary sensory cortex may enable sparse, comprehensive representations of higher order features to facilitate object identification. To generate such a code, cortical neurons must integrate broadly over space, yet simultaneously obtain sharp tuning to specific stimulus features. The logic of cortical integration that may synthesize such a sparse, high dimensional code for complex features is not known. To address this question, we probed the integration and population coding of higher order stimuli in the somatosensory and visual cortices of awake mice using two-photon calcium imaging across cortical layers. We found that somatosensory and visual cortical neurons sum highly specific combinations of sensory inputs supra-linearly, but integrate other inputs sub-linearly, leading to selective responses to higher order features. This integrative process generates a sparse, but comprehensive code for complex stimuli from the earliest stages of cortical processing. These results from multiple sensory modalities imply that input-specific supra-linear summation may represent a widespread cortical mechanism for the synthesis of higher order feature codes. This new mechanism may explain how the brain exploits the thalamocortical expansion of dimensionality to encode arbitrary complex features of sensory stimuli.

neuroscience↗