We systematically reviewed the patterns of Continuous Performance Test (CPT) errors of omission and commission exhibited by normal children and children with Attention Deficit and Hyperactivity Disorder (ADHD) under no drug, placebo and methylphenidate drug conditions. Findings from 26 studies were submitted to a meta-analytic procedure. In contrast to the contradictory findings of individual reports, our results revealed that children with ADHD made significantly more errors of omission and commission than normal children. As well, in children with ADHD and treated with methylphenidate, statistically significant reductions in the rate of both error types were noted. The effects of methylphenidate on the percentage of hits (i.e. 1 - omissions) were greater in experiments using shorter stimulus duration, smaller number of trials and higher probability of a target. Using Signal Detection Theory (SDT) parameters, we found that children with ADHD were less sensitive to the difference between targets and non-targets than their normal counterparts, while showing a comparable response bias. Similarly, the effects of methylphenidate were restricted to improving the sensitivity, while not affecting response bias, in both normal children and those with ADHD.

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The effects on activity rhythms of a daily 30 min opportunity to leave the home cage and hoard seeds from an open field were assessed in Syrian hamsters housed in continuous dim illumination. Six of ten hamsters responded with clear entrainment of their activity rhythms to the hoarding opportunity, as demonstrated by responses to phase shifts and by the onset phase of subsequent freerunning rhythms. No entrainable component separate from the freerunning rhythm was ever observed. Two hamsters showed phase shifts in response to the hoarding opportunity, but they did not meet the criteria for stable entrainment, and two did not respond with noticeable changes in rhythmicity. Ablations of the suprachiasmatic nuclei (SCN) were attempted in three hamsters that had entrained stably to the hoarding time. The effects of partial lesions in two animals indicated that the entrained rhythm was controlled by the light-entrainable pacemaker represented by the SCN. The one animal with an apparently complete lesion, however, developed a clear, but irregular, increase in activity in anticipation of the daily hoarding time. SCN ablation apparently unmasked an oscillator system separate from the SCN and susceptible to entrainment by a nonphotic cue. The oscillator mechanism affected by daily hoarding opportunities in hamsters appears to be tightly coupled to the SCN pacemaker, in contrast to the system in rats that is synchronized by daily feeding schedules.