PT  - JOURNAL ARTICLE
AU  - Ling-yun Li
AU  - Xu-ying Ji
AU  - Feixue Liang
AU  - Ya-tang Li
AU  - Zhongju Xiao
AU  - Huizhong W. Tao
AU  - Li I. Zhang
TI  - A Feedforward Inhibitory Circuit Mediates Lateral Refinement of Sensory Representation in Upper Layer 2/3 of Mouse Primary Auditory Cortex
AID  - 10.1523/JNEUROSCI.1516-14.2014
DP  - 2014 Oct 08
TA  - The Journal of Neuroscience
PG  - 13670--13683
VI  - 34
IP  - 41
4099  - http://www.jneurosci.org/content/34/41/13670.short
4100  - http://www.jneurosci.org/content/34/41/13670.full
SO  - J. Neurosci.2014 Oct 08; 34
AB  - Sensory information undergoes ordered and coordinated processing across cortical layers. Whereas cortical layer (L) 4 faithfully acquires thalamic information, the superficial layers appear well staged for more refined processing of L4-relayed signals to generate corticocortical outputs. However, the specific role of superficial layer processing and how it is specified by local synaptic circuits remains not well understood. Here, in the mouse primary auditory cortex, we showed that upper L2/3 circuits play a crucial role in refining functional selectivity of excitatory neurons by sharpening auditory tonal receptive fields and enhancing contrast of frequency representation. This refinement is mediated by synaptic inhibition being more broadly recruited than excitation, with the inhibition predominantly originating from interneurons in the same cortical layer. By comparing the onsets of synaptic inputs as well as of spiking responses of different types of neuron, we found that the broadly tuned, fast responding inhibition observed in excitatory cells can be primarily attributed to feedforward inhibition originating from parvalbumin (PV)-positive neurons, whereas somatostatin (SOM)-positive interneurons respond much later compared with the onset of inhibitory inputs to excitatory neurons. We propose that the feedforward circuit-mediated inhibition from PV neurons, which has an analogous function to lateral inhibition, enables upper L2/3 excitatory neurons to rapidly refine auditory representation.