International Journal of Comparative Psychology

Behavioral and pharmacological testing in mice has been revamped following the development of new tools for the manipulation of genetic information. We present the results from the peak procedure, an operant test that assesses the capacity to perceive, remember, and act upon temporal information. We studied the basic timing abilities in two different strains of mice, the C57Bl/6J and C3H/HeJ, and their response to psychoactive substances. Scopolamine and high doses of d-amphetamine disrupted performance by increasing response variability. The effect of d-amphetamine was particularly clear in C3H mice. Whereas scopolamine did not seem to affect the location of the response, the effect of a low dose of d-amphetamine, a leftward shift, was consistent with the hypothesis that it accelerates the internal time keeping mechanism. Physostigmine alone improved performance by reducing variability between trials without affecting the response location. Pretreatment with physostigmine partially blocked the deleterious effects of scopolamine. Methylphenidate did not have major effects on timing behavior in C57 but in the highest dose shifted the response of C3H mice to the left. The higher sensitivity of the C3H strain to the effects of d-amphetamine and methylphenidate support its value as an animal model of attention deficit disorder. The performance of mice in this temporal task was comparable to that observed in rats and pigeons, and seemed exquisitely sensitive to pharmacological manipulation.