Painful engrams: Oscillatory correlates of working memory for phasic nociceptive laser stimuli.

Research suggests that working memory (WM) is impaired in chronic pain. Yet, information on how potentially noxious stimuli are maintained in memory is limited in patients as well as in healthy people. We recorded electroencephalography (EEG) in healthy volunteers during a modified delayed match-to-sample task where maintenance in memory of relevant attributes of nociceptive laser stimuli was essential for subsequent cued-discrimination. Participants performed in high and low load conditions (i.e. three vs. two stimuli to keep in WM). Modulation of EEG oscillations in the beta band during the retention interval and in the alpha band during the pre-retention interval reflected performance in the WM task. Importantly, both a non-verbal and a verbal neuropsychological WM test predicted oscillatory modulations. Moreover, these two neuropsychological tests and self-reported personality measures predicted the performance in the nociceptive WM task. Results demonstrate (i) that beta and alpha EEG oscillations can represent WM for nociceptive stimuli; (ii) the association between neuropsychological measures of WM and the brain representation of phasic nociceptive painful stimuli; and (iii) that personality factors can predict memory for nociceptive stimuli at the behavioural level. Altogether, our findings offer a promising approach for investigating cortical correlates of nociceptive memory in clinical pain conditions.