Abstract
Previous studies indicate that performance on visual discrimination tasks is enhanced after a delay involving sleep, a result that has been interpreted as reflecting sleep consolidation (Karni, et al., 1994). In the motor domain, however, sleep gains are eliminated when fatigue-reducing spaced practice is used (Rickard, et al., 2008). We applied analogous methodology to test sleep enhancement in a classic texture discrimination task in which subjects indicate whether three slanted lines embedded in an array of lines have a vertical or horizontal orientation. Improvement in this task is measured by a decreased stimulus-to-mask onset asynchrony (SOA), here estimated using a staircase algorithm. Subjects trained on a TDT in the evening and were retested after a 24-hour delay involving normal sleep. Fifteen subjects trained using a standard massed training paradigm involving 192 trials with no breaks. Another 15 trained using an optimized training paradigm. In that condition there were 20s break after every 12 trials to reduce fatigue, and the 192 training trials were randomly interspersed with dummy trials which have been shown to mitigate adaptation effects thought to impair learning (Harris, Gliksberg & Sagi, 2012). Performance in the standard training paradigm was indeed improved on retest. The average SOA (109.6 ms) from the first 8 blocks of Session 2 was significantly decreased compared to the average SOA (137.7 ms) from the last 8 blocks of Session 1, t(1) = 3.45, p = .0014. However, in the optimized training group we found no evidence of enhancement after sleep, t(14) = 0.18, p= .52. The group by session interaction was highly significant, F(1, 28) = 8.4, p = .007. Retinotopic specificity was observed for both groups, indicating that training was sufficient to induce neural changes. These findings invite a theoretical reinterpretation of prior results demonstrating enhanced visual discrimination performance following sleep.
Meeting abstract presented at VSS 2014