Role of Theta Oscillations in Top-Down Control of Feature-based Attention

Applying top-down control to selectively process and distinguish visual stimuli based on their attributes such as color or motion is known as feature-based attention. Attention-control signals from the specialized regions in the frontal and parietal cortex, also known as dorsal attention network (DAN), are reported to bias the activity in the visual cortex in favor of the attended feature. Prior work has been successful in identifying the role of alpha oscillations (8-12 Hz) in modulation of sensory processing in visual cortex. However, it remains unknown whether and which oscillatory neural activity may support network communication and integration within and between the nodes of the attentional control network. We hypothesize that the nodes in the DAN dynamically interact via theta band (3-7 Hz) activity, and this coordination enables the DAN to send top-down control signals to the visual cortex. We investigated this by recording EEG during a cued feature attention experiment where participants were cued on a trial-by-trial basis to attend either the direction of motion or color of the forthcoming stimuli (moving dots). Using multivariate decoding approaches comparing attend-color versus attend-motion in the post-cue/pre-target period, we observe the pattern of theta and alpha activity to be predictive of the attended feature and importantly, the decoding timecourse in theta band to temporally precede the decoding in the alpha band. Further, estimating the spectral coherence between an ensemble of frontal and parietal scalp electrodes as an index of cortical synchronization between attention control networks from different frequency bands (e.g., theta, alpha, beta, and gamma activity), we observed significant decoding only in the theta band compared to decoding on surrogate (temporally shuffled) data. These results highlight the distinct role of theta oscillations in enabling the top-down control of selective sensory processing at the visual cortical level.