Abstract

After a prolonged exposure (adaptation) to unidirectional motion, a subsequently presented test pattern is perceived as moving in the opposite direction to that of the adaptation pattern (motion aftereffect - MAE; Mather et al., 2009). The motion adaptation paradigm has been widely used to investigate the spatial and temporal characteristics of the channels involved in motion perception, since it provides selective suppression of the mechanisms responding to specific temporal and spatial frequencies. Till recently, the spatiotemporal characteristics of the channels have been investigated using long adaptation durations (from several seconds to minutes). However, rapid forms of neural plasticity (i.e., short-term suppression and facilitation) have been recently found at the neural level in response to brief adaptations (Priebe et al., 2002; Hempel et al., 2000). Recent psychophysical studies on humans have proposed that such short-term forms of neural plasticity could provide the physiological substrate for rapid forms of MAE (rMAE) and visual motion priming (rVMP), and a longer lasting form of facilitation called Perceptual Sensitization (PS) (Pinkus and Pantle, 1997; Kanai and Verstraten, 2005; Pavan, et al., 2009, 2010). Indeed, the spatiotemporal characteristics of the perceptual outcomes obtained following brief motion adaptation with different types of motion stimuli (translational vs. optic flow components, first- vs. second-order, directional vs. ambiguous) seem to reflect the competition between coexistent forms of short- and longer-term synaptic forms of neural suppression and facilitation implemented at different levels of the visual cortical circuitries.