Abstract:
Background: Responsiveness to suggestions while hypnotised is termed hypnotic susceptibility. We investigated the effect of hypnotic susceptibility on the speed of information processing in human participants who performed precued simple (SRT) and choice (CRT) reaction time tasks. Method: Thirty-six right-handed participants (14 male), aged 19-37 (24.6 ± 4.6) years took part in the experiment. They were classified as “high” (Stanford Hypnotic Susceptibility Scale Form C (SHSS:C) score > 6; 15 participants) or “low” (SHSS:C score ≤ 6; 21 participants) hypnotic susceptibility. Participants completed a precued reaction time task with their right or left index finger requiring a key-press in response to a visual stimulus with high stimulus-response compatibility. The task was performed under hypnotised and non-hypnotised state conditions. Key-press force, surface electromyography, and electroencephalography (EEG) data were recorded. Premotor, reaction, motor, and movement times were measured for each trial, and the contingent negative variation (CNV) was derived from EEG data for each block of trials. Results: There was no significant effect of hypnotic state. Between-group analysis indicated that mean reaction times (SRT low = 239.6 ± 54.9 ms, high = 209.7 ± 29.3 ms, p<0.05; CRT low = 278.1 ± 57.6 ms, high = 244.3 ± 32.9 ms, p<0.05) and mean premotor times (SRT low = 192.5 ± 5.2 ms, high = 163.5 ± 25.3 ms, p<0.05; CRT low = 230.9 ± 54.9 ms, high = 198.7 ± 29.2 ms, p<0.05) were shorter in “high” than “low” participants. The mean CNV amplitude was larger for “high” participants than “low” participants (SRT low = -6.42 ±3.59 µV, high = -9.00 ± 4.96 µV, p<0.05; CRT low = -4.98 ± 3.10 µV, high = -7.47 ± 4.20 µV, p<0.05). Conclusions: We show that the observed difference in reaction time is primarily due to central information processing speed differences in premotor time. The difference in CNV amplitudes between “high” and “low” hypnotically susceptible individuals is a novel finding that establishes an association between changes in brain activity during motor preparation and hypnotic susceptibility. Significance Statement: This is the first study investigating reaction time in individuals of high and low hypnotic susceptibility that assessed both premotor time and the CNV. We show that hypnotic susceptibility is associated with the speed of cognitive processing underlying motor preparation. Results indicate that reaction time is faster in individuals who are more hypnotically susceptible, and faster reaction time is associated with a greater change in brain activity demonstrated by a significantly increased CNV amplitude preceding stimulus onset. One interpretation is that hypnotic susceptibility and neural mechanisms of arousal and selective attention are linked.