Electrophysiological evidence of atypical processing underlying mental set shifting in ecstasy polydrug and polydrug users.

Abstract

Executive functioning deficits are reported in ecstasy users. However research into mental set switching has been equivocal, with behavioural studies suggesting the function is preserved.The current study sought to address the issue of switching deficits in ecstasy users by combining behavioural performance with electrophysiological correlates (EEG). Twenty ecstasy polydrug users, 20 non-ecstasy polydrug users and 20 drug naive controls were recruited. Participants completed questionnaires about their drug use, sleep quality, fluid intelligence and current mood state. Each participant completed a mental set switching task (the number-letter task) whilst EEG measures were recorded. ANOVA revealed no between group differences on performance of the task, however a regression suggested that ecstasy use was a significant predictor for performance, after controlling for cannabis use. Mixed ANOVA revealed a significant effect of group on the P3, with significant differences between both drug groups and naives. There was also an interaction between electrode and group on the P2 component, with ecstasy users differing from both other groups. On the P3 component the results suggest a reduction in positivity at parieto-occipital electrodes for drug users compared to controls. Furthermore a significant increase in negativity in ecstasy users compared to control groups could be observed in several occipito-parietal electrodes at an N2 component as well as observable atypicalities in early processing (P2) displayed by ecstasy users and polydrug controls. The present study provides evidence of atypical processing of attentional shifting in ecstasy and polydrug users. Deficits in this executive function could reflect cognitive inflexibility and paucity of rapid behavioural adjustment, which may be problematic in real world situations.3

Meta-analysis of executive functioning in ecstasy/polydrug users

“…This suggests that ecstasy users work harder to achieve similar performance to controls, and that functional differences may be apparent with increased workload. Similar conclusions have been drawn from electroencephalogram studies whereby ecstasy users display evidence of recruiting additional resources in comparison with controls, whilst showing similar performance (Burgess et al 2011 ; Roberts et al 2013 a , b , c ). Similarly, functional magnetic resonance imaging (fMRI) studies have shown alterations to neuronal activation consistent with ecstasy-related damage despite not showing any performance deficits (Moeller et al 2004 ; Daumann et al 2005 ; Jager et al 2008 ; Roberts & Garavan, 2010 ).…”

“…However, some studies have observed significant switching differences between ecstasy users and controls (Halpern et al 2004 ; Dafters, 2006 a ) and neuroimaging studies have suggested atypical processing during switching (Roberts et al . 2013 c ). This highlights the necessity for larger samples to elucidate this performance deficit.…”

Immediate and short-term effects of single-task and motor-cognitive dual-task on executive function

“…Participants were generally healthy young men who were recruited through social media and telephone advertisements. Inclusion criteria were as follows: (1) Community-dwelling young men aged 18-30 years; (2) no cognitive impairments; (3) Montreal Cognitive Assessment (MoCA) score � 24; (4) ability to read Chinese characters; (5) normal or corrected-tonormal vision; (6) had enough sleep the day before the experiment; (7) middle to high physical activity levels as determined by the International Physical Activity Questionnaire (IPAQ); (8) received a good education (high school degree and above), could understand simple English words. Exclusion criteria were as follows: (1) color blindness or deficiency in color vision; (2) any severe cardiopulmonary disease; (3) any musculoskeletal difficulties that prevent exercise or other movement disorders; (4) taking of any medication during the intervention period that could impair cognitive function; and (5) alcohol consumption within 24 hours before the experiment.…”

“…Inhibition control is the ability to voluntarily suppress task-irrelevant responses in favor of task-relevant goal-directed responses [ 4 ]. Mental set shifting is the ability to switch attention between multiple tasks, operations, or mental sets [ 5 ]. Information updating involves continuously modifying the content of working memory as new information comes in [ 6 ].…”

Updating of working memory in ecstasy polydrug users: Findings from fNIRS

“…This method is commonly used in this research area (Montgomery et al, 2005: Roberts et al, 2015. Where objective measures of substance use have been collected in our previous work, low levels of recent use were found in participants' urine, and exclusion of participants with positive screens did not change the significant effects (Roberts et al, 2013).…”