I counted neuronal shooting costs and you may LFP gamma electricity and you may peak regularity inside V1 of five anesthetized macaque monkeys, having floating sinusoidal gratings of different designs, contrasts, orientations and you can disguised with assorted amounts of noises.
Around the personal websites, stabilized gamma power decrease twofold whenever gratings was indeed disguised with 80% sounds, as well as the mediocre height volume shifted regarding 42
We analyzed a common set of sites across conditions-those that were activated by the smallest grating. The average LFP spectra showed nearly a twofold increase in gamma power with larger gratings (Fig. 2A, left), with a more apparent bump in the gamma range. We quantified the change in gamma power (25–55 Hz) by normalizing to its maximum across stimulus sizes at each site, and then averaging across sites (n = 209 sites). This normalized gamma power increased monotonically from 0.67 ± 0.02 for the smallest grating to 0.93 ± 0.01 for the largest (p < 0.0001, Wilcoxon signed-rank test; Fig. 2A, middle, black). Similar effects were seen in each individual animal (faint black lines, indicating average effect in each animal). Over the same range of sizes, the gamma peak frequency at individual recording sites decreased from 50.5 ± 0.2 to 37.9 ± 0.1 Hz (p < 0.0001, t test; Fig. 2A, middle, red; data from each animal in faint red). Thus, gamma power and peak frequency were modulated in opposite ways by stimulus size: an increase in gamma power was associated with a decrease in peak frequency. The simultaneously recorded neuronal responses showed strong suppression for large gratings, with the normalized spike rate decreasing from 0.86 ± 0.02 to 0.41 ± 0.02 (p < 0.0001, Wilcoxon signed-rank test; Fig. 2A, right).
Gamma stamina, height frequency, and you will neuronal shooting rates for different stimulus alterations into the V1. An excellent, Remaining, Fuel spectra out of LFP to possess gratings various products (letter = 209 internet). Dashed range ways brand new gamma fuel having natural pastime. Center, Level regularity about gamma diversity (dense red line) and you may normalized gamma stamina (thicker black range). The latest weak lines imply the typical study away from for each and every animal. Dashed line suggests the newest gamma energy to possess impulsive passion. Right, Normalized neuronal solutions (thicker black colored line). Faint traces imply the common study off for each and every creature. B, Left, Strength spectra off LFP a variety of levels of music-hiding (n = 228 websites) how to find a sugar daddy Las Vegas NV. Middle, Level regularity and you will normalized gamma energy. Right, Stabilized neuronal firing price. C, Kept, Energy spectra away from LFP for different stimuli contrasts (n = 90 web sites). Center, Height volume and stabilized gamma fuel. Proper, Normalized neuronal answers. D, Remaining, Power spectra away from LFP to possess gratings various orientations (letter = 209 internet). Middle, Level frequency and normalized gamma electricity. Proper, Normalized neuronal solutions. All the mistake bars imply SEM.
We next measured gamma induced by large gratings (10°) masked with different levels of noise. Noise was generated by replacing different proportions of the gratings with random large pixels of the same mean luminance (see Materials and Methods). We used large gratings because these induced the most gamma power, for which the peak frequency was most clearly defined. Masking noise reduced gamma power (see also Jia et al., 2011), and caused the peak frequency of the average spectrum to shift lower (Fig. 2B, left; n = 228 sites). 2 ± 0.1 Hz to 30.1 ± 0.4 Hz (p < 0.0001, t test; Fig. 2B, middle). Thus, for masking noise, gamma power and peak frequency were positively correlated across stimulus conditions: a ma power was associated with a decrease in peak frequency. Despite prominent changes in gamma, population neuronal firing rates were not affected by noise masking (ANOVA: F = 1.18, p = 0.14; Fig. 2B, right). The normalized spike rate for the unperturbed gratings was indistinguishable from the 80% noise condition (0.79 ± 0.02 vs 0.78 ± 0.01; p = 0.04, Wilcoxon signed-rank test).