I basic computed just how gamma is affected by grating proportions, anywhere between step one so you can 10° when you look at the diameter
Performance
I counted neuronal shooting cost and you will LFP gamma electricity and you can peak volume in the V1 of five anesthetized macaque monkeys, for drifting sinusoidal gratings various models, contrasts, orientations and disguised with various quantities of noises.
Across individual web sites, stabilized gamma power dropped twofold when gratings was in fact disguised with 80% music, and the mediocre peak volume managed to move on from 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 energy, height frequency, and you may neuronal capturing speed for various stimuli modifications in the V1. Good, Left, Strength spectra out of LFP to have gratings of different types (n = 209 internet sites). Dashed line indicates the latest gamma energy getting natural interest. Middle, Height frequency regarding the gamma range (heavy red-colored range) and stabilized gamma strength (thick black range). The fresh new weak traces suggest the common studies of per creature. Dashed range ways brand new gamma energy for impulsive interest. Best, Normalized neuronal answers (thicker black line). Faint contours suggest the typical studies regarding for each creature. B, Remaining, Power spectra away from LFP for different quantities of appears-masking (letter = 228 websites). Center, Height volume and normalized gamma electricity. Proper, Normalized neuronal shooting speed. C, Leftover, Stamina spectra from LFP a variety of stimuli contrasts (n = 90 internet). Center, Level frequency and you can stabilized gamma electricity. Right, Normalized neuronal solutions. D, Remaining, Energy spectra of LFP having gratings of various orientations (n = 209 sites). Middle, Level regularity and you may normalized gamma electricity. Best, Normalized neuronal responses. Every colombian cupid mistake pubs suggest 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).
