Shifts of Gamma Phase across Primary Visual Cortical Sites Reflect Dynamic Stimulus-Modulated Information Transfer
Fig 5
Changes in phase shift sign modulate dynamically directional information transfer.
(A) Principle of the segmentation of the movie stimulation blocks illustrated on a pair of electrodes (the same one used in Fig 4A). For a given sending–receiving electrodes pair, the sign of the phase difference (whose meaning and color coding is illustrated in the schematic representation at the bottom of the panel) is first computed as a function of time for all trials. The histogram of phase differences across trials for this pair is represented on the right-hand side. Periods with a consistent dominant phase difference during a period superior to 300 ms are labelled according to the sign of the gamma phase difference. (B) TE values (Z-score units), from gamma phase to MUA, computed within blocks of positive and negative phase shifts, respectively. Results are presented as average over all relevant pairs across all sessions. Left: TE along the leading direction of causation (over the whole movie) for strongly asymmetric pairs. Middle: TE along the weakest direction of causation (over the whole movie) for strongly asymmetric pairs. Right: TE for symmetric electrode pairs. In this latter case, the average of TE over the two symmetric directions is shown. Stars indicate statistical differences (sign test). Data available at http://dx.doi.org/10.6084/m9.figshare.1460872.