Mean (+/- SE) performance of lesion and control animals under different signal length conditions. Data for the 1500 ms signal represent combined data from days 11–15 while data for the 4000 ms signal represent combined data from days 16–20. The 4 panels show: A – Percent correct responses (response to bright light), B – Percent signal omissions (failure to respond during the bright signal), C – Percent timed omissions (failure to respond within 4000 ms of the onset of the bright signal), D – Latency to lever press on a correct response. Full statistical analysis appears in the text. Main effects of signal length (without interaction) were found for timed omissions (p < 0.001), signal omissions (p < 0.001) and percent correct responses (p < 0.001). Significant signal length effects were only present in the PPTg group (p < 0.005) and the controls (p < 0.05) for the latency measure. Significant task × group interactions were found only in relation to the reaction time data depicted in panel B: there were significant differences between the 1500 and 4000 msec conditions in the control group (* p < 0.01) and in the PPTg group (**p < 0.009).