Short- and long-term forms of neural adaptation: An ERP investigation of dynamic motion aftereffects.

Adaptation is essential to interact with a dynamic and changing environment, and can be observed on different timescales. Previous studies on a motion paradigm called dynamic motion aftereffect (dMAE) showed that neural adaptation can establish even in very short timescales. However, the neural mechanisms underlying such rapid form of neural plasticity is still debated. In the present study, short- and long-term forms of neural plasticity were investigated using dynamic motion aftereffect combined with EEG (Electroencephalogram). Participants were adapted to directional drifting gratings for either short (640 msec) or long (6.4 sec) durations. Both adaptation durations led to motion aftereffects on the perceived direction of a dynamic and directionally ambiguous test pattern, but the long adaptation produced stronger dMAE. In line with behavioral results, we found robust changes in the event-related potentials elicited by the dynamic test pattern within 64-112 msec time range. These changes were mainly clustered over occipital and parieto-occipital scalp sites. Within this time range, the aftereffects induced by long adaptation were stronger than those by short adaptation. Moreover, the aftereffects by each adaptation duration were in the opposite direction. Overall, these EEG findings suggest that dMAEs reflect changes in cortical areas mediating low- and mid-level visual motion processing. They further provide evidence that short- and long-term forms of motion adaptation lead to distinct changes in neural activity, and hence support the view that adaptation is an active time-dependent process which involves different neural mechanisms.