Fig. 6.

An illustration of how the CMC model parameters explain gamma and beta stimulus responses in primary visual cortex for Experiment 1. Four connection strength parameters were the key determinants of beta/gamma features and are presented here. In the top row (a–d) The black line shows the mean CMC output and demonstrates that the model can generate clear beta and gamma peaks in its spectral output. A contribution analysis shows how small changes in each parameter affect the spectral output of the CMC (here the mean across participants). The red curves show how a small additive perturbation (+0.1) affects this spectral output and the blue lines show the spectral modulation to a small reduction (−0.1). In (a) it can be seen that gamma peak frequency is shifted upwards and downwards by increasing and decreasing the strength of the inhibitory gain control parameter on the superficial pyramidal cells. Note how peak gamma amplitude is also modified by this parameter. In (b) the gamma peak amplitude can be seen to be dependent on the inhibitory drive from the inhibitory interneurons onto the superficial pyramidal cells. Beta frequency is determined by the connection from deep pyramidals onto the inhibitory interneurons (c), whereas beta amplitude is strongly related to the inhibitory drive from the inhibitory interneurons on to the deep pyramidals. In the bottom row (e–h), the relationship between these same model parameters and peak gamma frequency (e), peak gamma amplitude (f), peak beta frequency (g) and peak beta amplitude (h) are shown. Each dot represents one of the 97 participants. Significant correlations are demonstrated (see text in each plot) that are consistent with the contribution analysis shown in the top row.