EEG theta dynamics for error processing during online movement control

To ensure optimal visuomotor feedback control during manual tracking, the brain must continuously monitor the error between the hand and the target. Modulations in the theta band (3-8 Hz) are related to error processing, but this has been mainly shown in cognitive control contexts. Hence, their relationship with hand-target errors during online control remains unclear. Here we assessed the impact of motor error processing on EEG theta-band activity in 29 healthy participants while they performed continuous tracking of a moving target with their dominant (right) hand. Two conditions were used to manipulate error processing demands: 1) in the Repeated condition, the same target trajectory was presented 80 times, allowing participants to implicitly learn the pattern and reduce tracking errors; 2) in the Random condition, 80 different trajectories were used, inducing persistent high tracking errors. Behavioral analyses confirmed that tracking errors were significantly higher in the Random than in the Repeated condition. Importantly, EEG theta power was also significantly higher in the Random condition, with a peak difference occurring at electrodes overlaying the left sensorimotor regions. This effect was selective to theta activity, as there was no modulation in alpha- (8-12 Hz) and beta-band (15-30 Hz) activity. Overall, this study extends the role of theta oscillations to online error processing in the context of motor control. It is possible that theta modulations reflected cortical activity mediating the communication and integration of information within sensorimotor circuits including the motor, premotor and parietal cortex, which are known to mediate online movement control.