Effects of stimulus modality on the shuttle activity in rats.

Shuttle activity during repeated presentation of irrelevant auditory (white band noise) and visual (darkness) stimuli was studied in 32 male Möll-Wistar rats. The subjects were randomly divided into two groups. In Group ND the auditory stimulus was used in the first habituation session, and the visual stimulus in the second habituation session. The opposite sequence of stimuli was applied in Group DN. House light was used as a background stimulus in both groups of subjects. The rate of crossing from one compartment to the other was markedly enhanced by noise, regardless of the position of the auditory stimulus in the session's sequence. A clear decrease of response rate was caused by noise termination, whereas neither darkness offset nor onset changed the relatively high and stable rate of responding. The results of this study provided convincing evidence of the energizing influence of the irrelevant auditory cue on the shuttle activity in rats. Moreover, these findings showed that a habituation procedure provides an efficient tool to analyze pure unconditional features of the to-be-conditioned stimuli, and to foresee several response modifications during further conditioning.