Synthesis of a comprehensive population code for contextual features in the awake sensory cortex

eLife

Daniel P Mossing¹  Evan H Lyall¹  Scott R Pluta²  Yun Wen Chu²  Hillel Adesnik³  Amir Dudai⁴ 

[1] Biophysics Graduate Group, Berkeley, United States;Department of Molecular and Cell Biology, Berkeley, United States;Department of Molecular and Cell Biology, Berkeley, United States;Department of Molecular and Cell Biology, Berkeley, United States;The Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, United States;The Edmond and Lily Safra Center for Brain Sciences and The Life Sciences Institute, The Hebrew University of Jerusalem, Jerusalem, Israel;

关键词: visual cortex;    barrel cortex;    sparse codes;    receptive field;    two photon calcium imaging;    neural coding;    Mouse;   

DOI  :  10.7554/eLife.62687

来源: eLife Sciences Publications, Ltd

【 摘 要 】

How cortical circuits build representations of complex objects is poorly understood. Individual neurons must integrate broadly over space, yet simultaneously obtain sharp tuning to specific global stimulus features. Groups of neurons identifying different global features must then assemble into a population that forms a comprehensive code for these global stimulus properties. Although the logic for how single neurons summate over their spatial inputs has been well explored in anesthetized animals, how large groups of neurons compose a flexible population code of higher-order features in awake animals 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 developed a novel tactile stimulator that allowed the precise measurement of spatial summation even in actively whisking mice. Using this system, we found a sparse but comprehensive population code for higher-order tactile features that depends on a heterogeneous and neuron-specific logic of spatial summation beyond the receptive field. Different somatosensory cortical neurons summed specific combinations of sensory inputs supra-linearly, but integrated other inputs sub-linearly, leading to selective responses to higher-order features. Visual cortical populations employed a nearly identical scheme to generate a comprehensive population code for contextual stimuli. These results suggest that a heterogeneous logic of input-specific supra-linear summation may represent a widespread cortical mechanism for the synthesis of sparse higher-order feature codes in neural populations. This may explain how the brain exploits the thalamocortical expansion of dimensionality to encode arbitrary complex features of sensory stimuli.

【 授权许可】

CC BY