Search

Assessment of hypnotic susceptibility is usually obtained through the application of psychological instruments. A satisfying classification obtained through quantitative measures is still missing, although it would be very useful for both diagnostic and clinical purposes. Aiming at investigating the relationship between the cortical brain activity and the hypnotic susceptibility level, we propose the combined use of two methodologies - Recurrence Quantification Analysis and Detrended Fluctuation Analysis - both inherited from nonlinear dynamics. Indicators obtained through the application of these techniques to EEG signals of individuals in their ordinary state of consciousness allowed us to obtain a clear discrimination between subjects with high and low susceptibility to hypnosis. Finally a neural network approach was used to perform classification analysis.

Retroactive interference from a declarative memory can prevent the consolidation of motor skill memories over wakefulness, but not over a night of sleep. Recently, motor imagery (MI) learning has been showed to allow for a stronger resistance against procedural interference rather than physical practice, but whether declarative interference might impact sleep-dependent consolidation process of an explicit finger tapping task learned with MI remains unknown. To address this issue, 57 subjects mentally rehearsed an explicit finger tapping sequence, and half of them were then requested to practice an interferential declarative task. All participants were re-tested on the initial procedural task either after a night of sleep or a similar daytime interval. The main findings provided evidence that declarative interference affected MI consolidation both over the night- and wakefulness intervals. These results extend our previous findings by underlying that declarative interference might impact more strongly explicit MI practice than physical practice, hence suggesting that MI might rely on declarative memory rather than exclusively on procedural memory system. The relationship between declarative and procedural memories during MI practice, as well as during off-line consolidation, is discussed.

The study was aimed at analyzing the written production of subjects with high (Highs) and low (Lows) hypnotizability scores. The participants were asked to write short texts following highly imaginative titles in standard conditions. The texts were processed through computerized and manual methods. The results showed that the Highs' texts are more sophisticated owing to a higher number of abstract nouns, more intense and imaginative owing to a larger number of similes, metaphors and onomatopoeias, less detailed owing to a higher nouns-to adjectives ratio. The differences in the use of abstract nouns and highly imageable expressions are discussed in relation to the pre-eminent left hemisphere activity of highs during wakefulness and to a possibly different involvement of the precuneus which is involved in hypnotic phenomena.

This study was designed to seek hypnotizability-related differences in attention temporal dynamics. For this purpose, an iconic version of the Attentional Blink Task (AB) was performed on 18 highly (Highs, score 9–12, SHSS form C) and 18 low susceptible individuals (Lows, score 0–3). The procedure consisted of two tasks in which two animal shapes (a coloured animal, Target, and a black butterfly, Probe) appeared in close temporal proximity within a rapid stream of distractors (black animals). In the Single task only Probe detection was required; in the Conditional task, Target identification was also requested. In this case, competition between Target and Probe for limited attentional resources decreases Probe visibility as a function of the time lag from Target (AB effect). A similar AB effect occurred in the two groups; nonetheless, Probe detection scores at the shorter lags were frequently higher in Highs than in Lows. This suggests that time constraints could affect the performance of Highs less than Lows, but also that the two groups could differ in attention capturing mechanisms, i.e. automatic capture by colour at the shorter lag. Moreover, Highs scores on Target identification were lower than Lows' ones indicating an impairment of Highs when engaged in dual tasks.