Frequency-dependent attentional modulation of local field potential signals in Macaque Area MT

Abstract

Visual attention modulates neuronal responses in primate motion processing area MT. However, whether it modulates the strength local field potentials (LFP-power) within this area remains unexplored, as well as how this modulation relates to the one of the neurons' response.Weinvestigated these issues by simultaneously recording LFPs and neuronal responses evoked by movingrandomdot patterns of varying direction and contrast in area MT of two male monkeys (Macaca mulatta) during different behavioral conditions. We found that: (1) LFP-power in the γ(30-120 Hz), but not in the δ(2-4 Hz), θ(4-8 Hz), α(8-12 Hz), β1 (12-20 Hz), and β2 (20-30 Hz) frequency bands, was tuned for motion direction and contrast, similarly to the neurons' response, (2) shifting attention into a neuron's receptive field (RF) decreased LFP-power in the bands below 30 Hz (except the θband), whereas shifting attention to a stimulus motion direction outside the RF had no effect in these bands, (3) LFP-power in the γ band, however, exhibited both spatial- and motion directiondependent attentional modulation (increase or decrease), which was highly correlated with the modulation of the neurons' response. These results demonstrate that in area MT, shifting attention into the RFs of neurons in the vicinity of the recording electrode, or to the direction of a moving stimulus located far away from these RFs, distinctively modulates LFP-power in the various frequency bands. They further suggest differences in the neural mechanisms underlying these types of attentional modulation of visual processing. Copyright © 2010 the authors.