Some parameters of heart rate change: perceptual versus motor task requirements, noxiousness, and uncertainty.

Sensory-motor integration and physiological patterns were investigated in a modified reaction time task. Following a READY signal, one of 2 DISCRIMINATIVE signals indicated that a right or left reaction was to be made to a GO signal. For one group, the DISCRIMINATIVE and GO signals occurred simultaneously; for another group, the GO signal was delayed 10 sec. In different sessions, shock occurred with the DISCRIMINATIVE signal on 0%, 33%, or 100% of the trials. The basic pattern of heart rate response was the same in all conditions, namely, acceleration followed by deceleration immediately prior to the DISCRIMINATIVE and GO signals. All experimental manipulations appeared to contribute to cardiac deceleration; for example, the greatest decrease occurred prior to the simultaneous DISCRIMINATIVE-GO signal with 33% shock probability. The least deceleration (and fastest reaction times) occurred to the delayed GO signal. Anticipation of a motor response and or shock also accentuated the accelerative limb of the heart rate curve, as well as producing increased skin conductance. Muscle action potentials from the chin showed an equivocal relationship to cardiac acceleration (or less deceleration) and to faster reaction times. Results are discussed in terms of an attentional hypothesis, and their relevance to speculations by Lacey and Obrist is examined.