Increased gamma band activity for lateral interactions in humans.

Alon Shapira,Oren Yehezkel,Uri Polat,Anna Sterkin,Moshe Fried,Zeev Zalevsky,Suliann Ben Hamed

doi:10.1371/journal.pone.0187520

Alon Shapira, Oren Yehezkel + Show 5 more

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https://doi.org/10.1371/journal.pone.0187520

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Journal: PloS one	Publication Date: Dec 14, 2017
Citations: 3	License type: CC BY 4.0

Affiliation: Bar-Ilan University, Tel Aviv University

Abstract

Collinear facilitation of contrast sensitivity supported by lateral interactions within primary visual cortex is implicated in contour and object perception, with neural correlates in several frequency bands. Although higher component of the ERP power spectrum, the gamma-band, is postulated to reflect object representation, attention and memory, its neuronal source has been questioned, suggesting it is an artifact reflecting saccadic eye movements. Here we explored the gamma-band activity during collinear facilitation with no saccade-related confounds. We used single-trial spectral analysis of ERP in occipital channels in a time-window of nearly complete saccadic suppression and discarded sporadic trials containing saccades, in order to avoid saccadic artifacts. Although converging evidence suggests that gamma-band oscillations emerge from local excitatory–inhibitory balance involving GABAergic inhibition, here we show activity amplification during facilitatory collinear interactions, presumably dominated by excitations, in the gamma-band 150–350 milliseconds following onset of low near-threshold contrast stimulus. This result highlights the potential role of gamma-band oscillations in neuronal encoding of basic processes in visual perception. Thus, our findings suggest that gamma-band ERP spectrum analysis may serve as a useful and reliable tool for exploring basic perception, both in normal adults and in special populations.

Highlights

At the earliest stages of visual processing, each neuron responds to stimulation in an isolated region of the visual field, termed classical receptive field (CRF) [1]
A linear prediction (LP) of no lateral interaction for the Lateral Hit (LH) condition type was calculated as the sum of the Flankers Correct Reject (FC) and Target Hit (TH) averaged spectrograms: AiLP 1⁄4 AiFC þ AiTH: ð7Þ
In the spectral analysis of LM trials with correct responses (Lateral Hit, Fig 3A), two peaks in the gamma frequency range were observed, in each one of the subjects, quantified within the following coordinates: first at 70.5±7.8 Hz and 200.7±34.1 msec, and second at 68.4±3.3 Hz and 298.9±6.1 msec. These peaks do not exist in the prediction of no lateral interaction in the LM (Linear Prediction, calculated as a sum of data produced for target presented in isolation and for flankers presented in isolation, with correct responses [80]; Fig 3B)

Summary

Introduction

At the earliest stages of visual processing, each neuron responds to stimulation in an isolated region of the visual field, termed classical receptive field (CRF) [1]. Response to GPs presented within the CRF of each neuron can be facilitated (i.e. increasing the sensitivity) or suppressed (i.e. decreasing the sensitivity) by responses to other GPs falling outside the CRF, which, when presented alone, do not activate the neuron. Because these neuronal interactions are mediated by lateral connections within the visual cortex A recent study mapped the lateral functional connectivity within V1, showing evidence for the psychophysical “association field” for collinear contour perception [35]

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