Response of rats with bilateral superior collicular lesions to change in the ambient visual environment

Abstract

Rats with bilateral lesions of the superior colliculus and controls were tested in an apparatus in which the ambient visual environment could be globally modified without changing nonvisual environmental cues. On each of 4 test days, the animals were habituated to either a blank or a patterned visual environment for 5 min (the habituation phase), removed from the apparatus for 5 min, and then replaced for another 5 min (the test phase) in either a blank or a patterned environment. When the habituation and test environments were the same (whether patterned or blank), all animals showed a small increase in activity in response to removal and replacement, but this rapidly fell to preremoval levels. When the two environments were visually different, the increase was significantly greater and remained so throughout the test phase, in both the control and the collicular-lesioned groups. In terms of behavioral change, colliculars were therefore as responsive as controls to this form of visual novelty. That the effect was as great in the pattern-to-blank condition as in the blank-to-pattern condition is further evidence that the “missing-stimulus effect” is demonstrable in an open field exploratory paradigm, where it does not depend on the integrity of the superior colliculus. © 1993, Psychonomic Society, Inc.. All rights reserved.