Hypnotizability-related cerebral oxygenation during actual and imagined movements

EEG studies revealed different information processing in participants with high hypnotizability scores (highs), who exhibit scarcely localized task-related EEG changes, and low hypnotizables (lows), who display specifically network-related changes. The study aimed to confirm those findings using near-infrared spectroscopy (NIRS). NIRS was applied to 10 highs and 9 lows (according to the Stanford Hypnotic Susceptibility Scale: A) during actual (M) and imagined (MI) sequential movements of the left arm and hand. The ability to be deeply absorbed in tasks and to vividly imagine through the visual and kinesthetic modalities was preliminarily assessed by the Tellegen Absorption Scale (TAS) and Betts' questionnaire, respectively. TAS scores were higher in highs than lows; Betts scores did not differ between groups. During tasks, NIRS revealed task-related increases in mean [OHb] in anterior and dorsolateral prefrontal areas only in lows, reduced [OHb] in the medial prefrontal and premotor cortex in highs, and no differences between tasks and groups in the right sensorimotor areas. Absorption was responsible for the [OHb] changes in prefrontal areas. Correlational analysis between the areas' mean [OHb] showed different neural patterns during M and MI, with hypnotizability playing a greater role in MI than in M. NIRS supports earlier EEG findings, indicating lower oxygenation demand in highs than lows during tasks compared to baseline. Since highs reported lower cognitive effort than lows during tasks (NASA TLX questionnaire) and exhibited lower oxygenation demand, the findings may indicate higher neural efficiency in highs than in lows.