Changes in Heart Rate and Slow Brain Potentials Related to Motor Preparation and Stimulus Anticipation in a Time Estimation Task

Based on previous research, it was hypothesized that both the final cardiac deceleration and the late wave of the Contingent Negative Variation (CNV) at the end of the foreperiod of a simple reaction time task are composed of a movement‐related component and a stimulus‐anticipation component. Forty right‐handed adult female and male subjects performed a time estimation task. They had to press a button with the index‐finger at intervals of 20 to 22 seconds. After the button‐press a visual stimulus was presented, which provided Knowledge of Results (KR) about the correctness of the timing. For half the subjects the delay between button‐press and stimulus presentation was 2 s, for the other half it was 4 s. Recordings of both the electrocardiogram (ECG) and the electroencephalogram (EEG) were obtained, the latter being derived bilaterally from precentral. postcentral. and parietal sites. As was expected, cardiac deceleration was found both prior to the movement and prior to stimulus presentation in both delays. At the cortical level the movement was preceded by a Readiness Potential (RP). Stimulus presentation was preceded by a cortical negative wave, the Stimulus‐Preceding Negativity (SPN), at all positions. Precentrally and postcentrally the Stimulus‐Preceding Negativity exhibited a larger right hemisphere preponderance in the 2‐s delay than in the 4‐s delay.