Finally, i measured this new positioning tuning from gamma strength and you may top frequency and you may opposed these to neuronal spiking craft
Finally, i measured this new positioning tuning from gamma strength and you may top frequency and you may opposed these to neuronal spiking craft

We used responses to large gratings (10°) drifting in 16 different directions (conditions averaged in Fig. 2A). To quantify across recording sites, we defined the preferred orientation (that inducing maximal gamma power) at each site to be 0°. The average power spectra for a subset of orientations are shown in Figure 2D (left; same n = 209 sites as in Fig. 2A). On average, gamma power at the preferred orientation was approximately twice that of the orthogonal orientations. However, the peak frequency of gamma was not significantly modulated by stimulus orientation, with the peak frequency at the preferred and orthogonal orientations nearly indistinguishable (36.8 ± 0.3 vs 36.6 ± 0.3 Hz, p = 0.6, t test; Fig. 2D, middle). When arranged by the preferred orientation of gamma power, spike rate tuning functions showed a response at the preferred orientation that was significantly <1>

Model of gamma generation

We simulated the stimulus dependence of spiking activity and gamma power and peak frequency with a simple three component model, an extended but simplified version of the model developed by Kang et al. (2010). The model consisted of a local excitatory (E), local inhibitory (I), and global (G) excitatory component (see Fig. 1 and Materials and Methods). The local E and I components represent populations in a local V1 region, such as in a cortical hypercolumn. The local E and I components were recurrently connected-the excitatory component provided input to the inhibitory component (WEI) and to itself (WEE), and similarly for the inhibitory component (WWeb browser and WII). Both the E and I components also received external and independent Poisson-distributed input (IE and II). This architecture captures the basic pyramidal-interneuron network gamma (PING) model, commonly used read here to model gamma generation (Bartos et al., 2007; Tiesinga and Sejnowski, 2009; Whittington et al., 2011).

The global part combines excitatory craft during the several local places (W

The third component-the global or G component-represents a more spatially extensive mechanism. Particularly), and affects both the local E and I components through excitatory connections (WGE and WGI, respectively). G might arise from long-distance horizontal connections between columns in V1 or feedback from higher visual areas (Angelucci and Bresslof, 2006). Figure 3, A and B, shows the behavior of the E component of the model for a small and large high contrast “gratings” (i.e., input), respectively. The mean activity of E is higher for the smaller stimulus. Spectral analysis shows the presence of elevated gamma frequency components in the activity of E, which are weaker and at a higher peak frequency for small gratings (centered around 50 Hz, Fig. 3C) than large gratings (?40 Hz, Fig. 3D). The peak frequency of gamma shifts lower as power increases because the time constant for the global component, recruited more strongly by the large stimulus, is slower than for the local E and I, lowering the resonant frequency of the network. Note that for both simulations gamma power fluctuates in time, consistent with previous analysis of physiological data (Burns et al., 2010a,b, 2011).

Example simulator solutions. Good, Impulse of your Age component to a tiny grating (roentgen = 3), due to the fact a function of go out. Notice the strong indicate reaction, and also the exposure from transient gamma fluctuations. Quicker gratings (roentgen = a couple of) brought more powerful responses, but deficiencies in gamma power to visualize in one single demo. B, Effect of one's Age component to a big grating (roentgen = 5). Notice this new ma band craft. C, D, Spectrogram of one's epochs found in A and you can B, respectively. Gamma passion try weakened and also at a higher volume toward short grating. Spectra was computed from inside the a sliding 512 ms window, oriented at the time shown; spectra were smoothed to have screen simply, by the convolving a-two-dimensional Gaussian kernel with the analysis.

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