THE EFFECTS OF CAFFEINE AND DIRECTED ATTENTION ON ACOUSTIC STARTLE HABITUATION

The present experiment tested the effects of caffeine on acoustic star tle habituation during different attention tasks in which subjects eit her (a) attended to the acoustic startle stimulus (auditory attention; n = 9) (b) attended to a visual search task during presentation of ac oustic startle stimuli (visual attention; n = 10), or (c) were given n o specific instructions during acoustic startle testing (no attention; n = 9). Startle eyeblink responses were measured after subjects recei ved either caffeine (1 mg/kg) or placebo. Caffeine significantly delay ed response habituation in the no attention group and in the auditory attention group, but had no effect on habituation in the visual attent ion group. These data show that startle habituation can occur with min imal attention being directed to the acoustic startle stimulus, and th at visual attention cancels the effects of caffeine on startle habitua tion. (C) 1998 Elsevier Science Inc.