The purpose of this thesis was to assess the integrity of the serotonin system, by measuring the neurophysiological response to tasks that measure executive functions, and neuroendocrine function in ecstasy users and non-users. Each of the proposed executive functions outlined in Miyake et al.’s (2000) conceptual framework (inhibition, switching and updating) as well as the addition of access to semantic/long term memory made by Fisk and Sharp (2004), was assessed using behavioural tasks in combination with EEG and fNIRS.
Behavioural performance between ecstasy users and various controls (polydrug and drug naive) was equivalent throughout the thesis. However ERP analysis revealed ecstasy-related atypicalities in cognitive processing during inhibitory control, switching and access. Ecstasy users displayed increases in P2 and N2 components during these tasks that reflect recruitment of additional resources. A diminished P3 response during the switching task was evident for ecstasy users and polydrug users relative to controls. Regression analyses suggest that lifetime cannabis use may be an important factor for this function. Results from fNIRS suggest that ecstasy users show an increased haemodynamic response during all four executive functions relative to non-users, which suggests that ecstasy users are engaged in more effortful cognition than controls. Increases in neuronal activation whilst performing at a similar level behaviourally are understood as recruitment of additional resources. Again during switching cannabis use may have been an important factor.
Another aim of this thesis was to assess neuroendocrine function. Ecstasy users displayed elevated basal cortisol levels relative to polydrug controls and drug naive controls. The results suggest that ecstasy is detrimental to the integrity of the HPA-axis.
This thesis provides support for ecstasy-related damage to the serotonergic system and should be used in educating prospective ecstasy users of relative harms
