Abstract
Despite the enduring interest in alertness, no research has been conducted to clarify its relationship with visual perceptual learning (VPL, Watanabe & Sasaki, 2015). To examine the relationship, we varied the temporal order of an exposed visual stimulus and the alertness cue. During 12-daily training sessions, two orientations were presented in the trained eye in a random order, whereas simultaneously high contrast dynamic color patches were presented to the untrained eye to render the stimulus imperceptible (Tsuchiya & Koch, 2005; Seitz, Kim & Watanabe, 2009). A beep sound was presented 400 ms prior (Pre-Cue group, n=10) or subsequent to (Post-Cue group, n=6) the presentation of one of the orientations (paired orientation), whereas the other orientation was not paired with sound (unpaired orientation). Subjects were tested on the two orientations in each eye in pre- and post-tests. In both groups, significant VPL of the paired orientation was observed in both the trained and untrained eyes. Unexpectedly, VPL transferred to the unpaired orientation in the Post-Cue group. Attention should not play a role in inducing the transfer to the unpaired orientation, as it is pre-cues that are more efficient in association with attention (Liu et al., 2005). Previously, we presented reward instead of a sound in an otherwise identical paradigm to the current study (Wang, Kim, Sasaki and Watanabe, 2018). VPL occurred only in the paired orientation, in the trained eye of the Post-Reward group, suggesting that VPL driven by reward is significantly different from VPL by alertness. Our results are in accordance with the hypothesis that alertness impacts on the activity in the locus coeruleus norepinephrine (LC-NE) system which influences the decision-making areas (Aston-Jones & Cohen, 2005), where orientations are less specifically processed, which allows for transfer of VPL to other orientations.