Neurophysiological features of tactile versus visual guidance of ongoing movement.

Although studies have investigated tactile and visual processing for perception, sensory processing for ongoing action remains poorly understood. The purpose of this study was to explore modality-specific patterns of cortical activation and functional connectivity in a practiced trajectory tracking task. Participants traced irregular shapes with their index finger using either touch or vision for guidance. In 60 tactile-motor (TM) trials, movement was guided only by tactile feedback of semicircular bumps on a plastic tile. In 60 visuo-motor (VM) trials, movement was guided only by vision of dots on a screen seen through a small window at the finger tip. The order of TM and VM trials was counterbalanced across 16 participants. Electroencephalography (EEG) was used to estimate cortical activation (task-related spectral power) and functional connectivity (task-related magnitude-squared coherence) in the alpha (8-12 Hz) and beta (13-30 Hz) bands during the last 12 movement trials in each sensorimotor task. TM vs. VM tasks exhibited a larger drop in global beta cortical activation, and greater alpha coherence between central, parietal, and occipital regions. VM vs. TM tasks were characterized by low global alpha coherence. Trace time and cortical activation of the last 12 VM trials were reduced in the group performing the VM task after the TM task compared to those performing the VM task first. Beta connectivity initiated by the first task was maintained on the subsequent second task, regardless of the task order. Identification of modality- and order-specific EEG characteristics provides insight into the sensory control of movement.