Mnemonic search, but not arithmetic transformation, is associated with psychophysiological inhibition

The possibility that mnemonic search and arithmetic transformation induce transient heart rate (HR) slowing was studied. Transient HR slowing was assumed to result from the inhibition of premature responding during information processing. Twenty young men performed a 2-step reaction time task. Two precues were followed by a choice cue: 2 additional precues and 1 final choice cue. Choice cues were varied to compare spatial and perceptual-motor processing with mnemonic or arithmetic processing. Cardiac interbeat interval and impedance cardiograph measures were taken beat by beat. The preparation for the respond cue was associated with HR slowing followed by HR speeding associated with response initiation. Mnemonic search induced a transient HR slowing before the speeding initiated by the motor response. Arithmetic transformation did not, but processing of the arithmetic series decreased cue-induced transient HR slowing. Mnemonic search may be associated with a psychophysiological inhibition analagous to that observed in perceptual-motor tasks during response selection.