Il sonno locale come possibile causa di perdite temporanee dell'autocontrollo nella soppressione comportamentale delle emozioni: uno studio EEG ad alta densità
Among the main emotional regulation strategies there is expressive suppression, which consists in inhibiting behavioural responses elicited by stimuli with emotional value. Of note, expressive suppression represents a form of self-control, that is, the ability to voluntarily suppress different types of impulses. Some studies have shown that failures in self-control may be associated with temporary local increases in low-frequency (< 9 Hz) electroencephalographic (EEG) activity – also indicated as local sleep-like episodes - within frontal brain regions. Converging lines of evidence showed that the incidence of these episodes increases during prolonged wakefulness. Moreover, it is well known that sleep restriction or deprivation commonly determine significant alterations in emotional regulation. Based on these considerations, this Thesis project aimed at investigating whether local sleep-like episodes could represent a possible cause of failure in the implementation of expressive suppression strategies.
Nineteen healthy volunteers (26.3 ± 2.9 years, 10F) completed two distinct experimental sessions during which amusing video clips were presented and brain activity was continuous recorded using EEG (64 electrodes). In one experimental session, participants were asked to inhibit the emotional behavioural response, with the instruction to maintain a neutral facial expression (expressive suppression, ES), while in the other experimental session they were allowed to freely express their emotions (free expression, FE). The changes in facial expression were monitored through video recordings. Finally, the sleep/wake patterns of the days preceding the experiments was monitored through wrist-worn actigraphy.
The obtained results demonstrate that the failures of expressive suppression (i.e. changes of facial expression in the ES condition) are preceded by an increase in delta activity (1-4 Hz) in the frontal and parietal regions (p <0.05). Moreover, a shorter sleep duration on the night preceding the ES condition is associated with a greater number of failures (p = 0.01) and greater delta activity in frontal regions during the failure of expressive suppression (p = 0.03).
These results demonstrate that local sleep-like episodes in brain regions associated with emotional regulation may represent a possible direct cause of failure in expressive suppression, and that their probability of occurrence is directly influenced by the hours slept during the previous night
