Figure 2.

Stop-signal reaction time task performance in PWS^ICdel mice. (A) Altering the position of the auditory stop-signal led to the anticipated increase in impulsive responding as stopping was made more difficult with presentations progressively closer to the execution of the go response. However, PWS^ICdel mice showed increased impulsivity relative to WT littermate controls, particularly when the stop signal was presented near the middle of the individual go response. (B) Altering the position of the stop signal did not affect the proportion of correct go responses made or the speed of the go response (C). However, there was a tendency for PWS^ICdel to make more correct responses than their WT littermates. Further analysis of SSRTT performance was conducted to examine the point where competition between the go and stop responding was at its greatest; thus, data from each subject were ranked and sessions where correct stopping was at 50 ± 10% averaged. When stopping with 50% accuracy, the SSRT, the latency to withhold responding, was calculated (D). PWS^ICdel mice had significantly longer SSRTs than their WT littermates, but there were no genotype-related differences for the proportion of trials initiated (E) and increases in the latency to initiate a trial (F) and the time taken to enter the food magazine following a successful trial (G). Baseline data (BL: i.e. mean of the sessions immediately preceding each session where the stop-signal position was altered) when the stop-signal presentation was concurrent with the start of the go response (0%). Data are mean ± SEM, ^* and ^** denotes P < 0.05 and ^**P < 0.01 for significant difference between WT and PWS^ICdel mice, respectively.