Responses of the T-wave amplitude as a function of active and passive tasks and beta-adrenergic blockade

This paper presents evidence that phasic changes in T-wave amplitude vary as a function of task conditions and beta-adrenergic drugs. Three experiments were designed to test the sensitivity of T-wave amplitude to manipulations in sympathetic arousal. In the first experiment, T-wave amplitude was recorded during an active behavioral task in which 32 subjects believed that they could control the duration of an aversive white noise and during a passive behavioral task in which another 30 subjects knew that they had no control. T-wave amplitude decreased to a greater extent in the active behavior group than in the passive group. In the second experiment, 9 subjects receiving one of two beta-adrenergic blockers and 10 subjects receiving placebo completed the active task. Task-induced reductions in T-wave amplitude were systematically blocked by the beta blockers. In the third experiment, 5 subjects received placebos and 15 received one of two different beta blockers. All subjects performed a mental arithmetic task. Subjects receiving a placebo, but not those receiving beta blockade, exhibited a significant reduction in T-wave amplitude during mental arithmetic.