Figure 7.
Gamma band synchronization between PFC and MT specifically enhances the firing rate effects attributed to selective visual attention, in a similar way as PFC rate increases. A, Trial-averaged (Nt = 20) population activity during the test period in attention (orange), nonattention (gray), and random top-down latencies (green) cases. Attention enhances selectivity, and interareal gamma band synchronization contributes. B, Modulation ratios [i.e., point-by-point division of attentional rates by nonattentional rates (Martinez-Trujillo and Treue, 2004) in A] are accentuated in the control case (orange) relative to the case with asynchronous top-down input (green). Attentional modulation is recovered when, in addition, PFC neurons receive external injected current (red). C, PFC activity for the cases depicted in B. Activity is boosted by external current injection (red), and this results in a recovered modulation ratio through asynchronous top-down signal in B. D, Interareal synchronization increases the exponent of the power-law relationship between MT neuron activity and input (I = IS + IA). The exponent increases from 3.79 to 3.92. Inset, Tuning curves with interareal synchrony (orange) and without (green).