![]() The dashed lines indicate the significance thresholds (p<0.05) obtained with a non-parametric randomization test including correction for multiple comparisons. (G) Spectrum of correlation coefficients between the GPR and RT, separately for attend IN (red) and attend OUT (blue). (F) Same as E but in Cartesian coordinates, and showing both the attend-IN (red) and the attend-OUT (blue) condition. Color code reflects the cosine of the deviation from the mean phase relation, referred to as "goodness of phase relation" (GPR). (E) Same as D, but averaged over all V1-V4 site pairs, after normalizing RTs per monkey. Note that the rotation is based on the mean phase relation shown in A, and it reveals that RTs systematically decrease with decreasing deviation from the mean phase relation. (C,D) Same as A,B, after rotating all phase relations such that the mean phase relation is at zero. (B) Polar plot showing reaction time as a function of the V1-V4 gamma phase relation (copy of Figure 4A). The yellow bar represents the mean gamma phase relation, which corresponds to the phase relation at which gamma-band synchronization occurred. The polar histogram in red shows the corresponding distribution. (A) Each dot represents the gamma phase relation between V1 and V4 in one trial. This rotation was applied to allow pooling of site pairs, and to investigate whether RTs depended systematically on the deviation from the mean phase relation. Panels (A-D) illustrate, using the example pair of Figure 4A during attend-IN, that all phase relations of a given pair were rotated such that the mean phase relation was at zero. ![]() Trial-by-trial deviation from mean interareal gamma-band phase relation predicts reaction time. Shaded areas around the curves show ☑ SEM across trials for the C-F, and site pairs in G,H. In C-F, for area V1 and area V4 separately, data were averaged over the top third of recording sites with the strongest visually induced gamma-band activity, because those sites were used for further analysis. (G) Spectrum of V1-V4 synchronization in monkey K, as quantified by the pairwise phase consistency (PPC). (C) Spectrum of visually induced power changes in V1, quantified as percent change relative to pre-stimulus baseline. Note that the color range is scaled separately per area, because visually induced gamma was substantially stronger in V1. Overlaid color map illustrates visually induced gamma-band activity in areas V1 and V4. (A) Dots represent positions of ECoG recording sites on V1 and V4 in monkey K, projected onto a standard brain. Thus, interareal gamma synchronization occurs at the optimal phase relation for transmission of sensory inputs to motor responses.ĮCoG coverage of areas V1 and V4, and spectra of visually induced power changes and of interareal synchronization. Effects were specific to the attended stimulus and not explained by local power or phase. V1-V4 gamma phase relations accounted for RT differences of 13-31 ms. RTs slowed systematically as trial-by-trial interareal gamma phase relations deviated from the phase relation at which V1 and V4 synchronized on average. V1-V4 gamma synchronization immediately preceding the stimulus change partly predicted subsequent reaction times (RTs). We recorded local field potentials from V1 and V4 of macaques performing an attention task during which they reported changes in the attended stimulus. Effective communication depends on enhanced interareal coherence, but it remains unclear whether this coherence occurs at an optimal phase relation that actually improves stimulus transmission to behavioral report. ![]() Behavior is often driven by visual stimuli, relying on feedforward communication from lower to higher visual areas.
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