ALERTING EFFECTS ON CHOICE-REACTION TIME AND THE PHOTIC EYEBLINK REFLEX

To test the possibility that a common mechanism might be responsible f or alerting effects on voluntary and reflexive reactions, choice react ion times (RT) to intense flashes of light were compared with eyeblink reflexes simultaneously evoked by those stimuli. An acoustic accessor y stimulus, irrelevant to the RT task, facilitated both voluntary and reflexive reactions. A time uncertainty manipulation also generated fa cilitation of both responses under conditions in which phasic arousal was presumably greatest. However, there were several dissociations bet ween alerting effects on voluntary and reflexive reactions and between effects on the early and late subcomponents of the photic orbicularis oculi reflex. In conjunction with other research in humans and animal s, these data support the assumption that alerting involves the activa tion of multiple neuromodulatory (e.g. monoamine) systems, each of whi ch is characterized by a distinct behavioral, neuropharmacological, an d electrophysiological profile.