Gwen Folkert^1,2, Leor Katz¹, Richard Krauzlis¹; ¹Laboratory of Sensorimotor Research, National Eye Institute, NIH, ²Brown University

The midbrain superior colliculus (SC) is crucial for visual attention and plays a causal role in shaping attention-related activity across several cortical areas. We recently reported that inactivating SC reduces attention-related modulations of spiking activity in frontal eye fields (FEF) and the floor of the superior temporal sulcus (fSTS). The contribution of SC to mechanisms of rhythmicity and synchrony, measured in local field potentials (LFPs), is unknown. To address this gap, we investigated the effects of inactivating SC on LFP activity in FEF and fSTS. Two monkeys performed a spatial attention task before and during pharmacological inactivation of SC while electrophysiological activity was recorded from a multichannel probe in FEF or fSTS. Monkeys maintained central fixation while patches of moving dots were presented in each hemifield, such that one of the patches was within the response fields of recorded neurons. In Attend blocks, monkeys were rewarded for releasing a joystick in response to a change of motion direction in either of the two patches, requiring attention to both peripheral locations. In Ignore blocks, monkeys were instead rewarded for reporting a dimming of the fixation point. Before SC inactivation, LFP power in FEF was higher during Attend than Ignore trials in the 500 ms epoch preceding the change, prominently in theta (4-8 Hz) and gamma (>30 Hz) frequency bands. This attention-related LFP modulation was weaker and less frequency-specific in fSTS, but still present. During SC inactivation, deficits in task performance were accompanied by ~50% reductions of attention-related LFP modulation in FEF, consistent with the large impact of SC inactivation on spiking. Attention-related LFP modulation in fSTS was relatively unaffected, despite robust effects on spiking activity. This dissociation suggests that the SC contributes to distinct mechanisms of attentional modulation in frontal and temporal cortices, rather than exerting stereotyped effects on neuronal synchronization.