Toward modeling age-related changes of attentional abilities in rats: simple and choice reaction time tasks and vigilance.

Fischer-344 rats aged 4, 12, or 18 months were trained in a simple or choice reaction time task (SRTT; CRTT). Animals were required to detect a brief (50 ms), rarely, and unpredictably occurring signal that was presented either at the central panel light (SRTT) or above one of the two levers (CRTT). Animals reported detection by pressing either lever (SRTT) or the cued lever (CRTT) within 3 s. False alarm rates were obtained from a nonsignal 3-s bin. In comparison to younger animals, 18-month-old animals showed a reduced signal detectability, and this effect did not interact with practice. These results suggest that age affected vigilance and practice did not attenuate this effect. The benzodiazepine receptor agonist chlordiazepoxide (at subsedative doses; 1, 3, and 5 mg/kg) and the beta-carboline ZK 93 426 (1, 3, and 5 mg/kg) failed to affect signal detectability. Scopolamine HBr and MBr impaired detectability and responsivity to a similar extent. However, scopolamine MBr, unlike the tertiary compound, failed to affect response accuracy in the CRTT. It is speculated that the failure of chlordiazepoxide to affect performance was related to low processing demands of both tasks. Although these behavioral models show good face validity, they do not allow determination of the major components of attentional processes (perceptual sensitivity, response criterion, processing capacity). Animal behavioral paradigms that allow determination of such components are required for the investigation of the neuronal basis of age-related changes in attentional abilities.