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Proc Natl Acad Sci U S A. 2014 May 6;111(18):6780-5. doi: 10.1073/pnas.1405300111. Epub 2014 Apr 17.

Cortical oscillations arise from contextual interactions that regulate sparse coding.

Author information

1
Howard Hughes Medical Institute, Salk Institute for Biological Studies, La Jolla, CA 92037.

Abstract

Precise spike times carry information and are important for synaptic plasticity. Synchronizing oscillations such as gamma bursts could coordinate spike times, thus regulating information transmission in the cortex. Oscillations are driven by inhibitory neurons and are modulated by sensory stimuli and behavioral states. How their power and frequency are regulated is an open question. Using a model cortical circuit, we propose a regulatory mechanism that depends on the activity balance of monosynaptic and disynaptic pathways to inhibitory neurons: Monosynaptic input causes more powerful oscillations whereas disynaptic input increases the frequency of oscillations. The balance of stimulation to the two pathways modulates the overall distribution of spikes, with stronger disynaptic stimulation (e.g., preferred stimuli inside visual receptive fields) producing high firing rates and weak oscillations; in contrast, stronger monosynaptic stimulation (e.g., suppressive contextual stimulation from outside visual receptive fields) generates low firing rates and strong oscillatory regulation of spike timing, as observed in alert cortex processing complex natural stimuli. By accounting for otherwise paradoxical experimental findings, our results demonstrate how the frequency and power of oscillations, and hence spike times, can be modulated by both sensory input and behavioral context, with powerful oscillations signifying a cortical state under inhibitory control in which spikes are sparse and spike timing is precise.

KEYWORDS:

cerebral cortex; gamma oscillations; inhibitory interneurons; visual cortex model

PMID:
24742427
PMCID:
PMC4020078
DOI:
10.1073/pnas.1405300111
[Indexed for MEDLINE]
Free PMC Article

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