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Cereb Cortex. 2018 Oct 11. doi: 10.1093/cercor/bhy260. [Epub ahead of print]

Sparse Representation in Awake Auditory Cortex: Cell-type Dependence, Synaptic Mechanisms, Developmental Emergence, and Modulation.

Liang F1,2,3, Li H2,3, Chou XL2,3,4, Zhou M2,4, Zhang NK2, Xiao Z5, Zhang KK6, Tao HW2,3, Zhang LI2,3.

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Department of Medical Engineering, School of Biomedical Engineering, Southern Medical University, Guangzhou, China.
Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA.
Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA.
Neuroscience Graduate Program, University of Southern California, Los Angeles, CA 90089, USA.
Department of Physiology, School of Basic Medical Sciences, Southern Medical University, Guangzhou, China.
Department of Pathology, the University of North Dakota, Grand Forks, ND, USA.


Sparse representation is considered an important coding strategy for cortical processing in various sensory modalities. It remains unclear how cortical sparseness arises and is being regulated. Here, unbiased recordings from primary auditory cortex of awake adult mice revealed salient sparseness in layer (L)2/3, with a majority of excitatory neurons exhibiting no increased spiking in response to each of sound types tested. Sparse representation was not observed in parvalbumin (PV) inhibitory neurons. The nonresponding neurons did receive auditory-evoked synaptic inputs, marked by weaker excitation and lower excitation/inhibition (E/I) ratios than responding cells. Sparse representation arises during development in an experience-dependent manner, accompanied by differential changes of excitatory input strength and a transition from unimodal to bimodal distribution of E/I ratios. Sparseness level could be reduced by suppressing PV or L1 inhibitory neurons. Thus, sparse representation may be dynamically regulated via modulating E/I balance, optimizing cortical representation of the external sensory world.


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