The results were consistent with the proposal that ecstasy-related damage to the serotonin system causes behavioural changes on tests of visual perception processes that are thought to reflect serotonergic functions in the occipital lobe.
'Ecstasy' (3,4-methylenedioxymethamphetamine) induces impaired functioning in the serotonergic system, including the occipital lobe. This study employed the 'tilt aftereffect' paradigm to operationalise the function of orientation-selective neurons among ecstasy consumers and controls as a means of investigating the role of reduced serotonin on visual orientation processing. The magnitude of the tilt aftereffect reflects the extent of lateral inhibition between orientation-selective neurons and is elicited to both 'real' contours, processed in visual cortex area V1, and illusory contours, processed in V2. The magnitude of tilt aftereffect to both contour types was examined among 19 ecstasy users (6 ecstasy only; 13 ecstasy-plus-cannabis users) and 23 matched controls (9 cannabis-only users; 14 drug-naive). Ecstasy users had a significantly greater tilt magnitude than non-users for real contours (Hedge's g = 0.63) but not for illusory contours (g = 0.20). These findings provide support for literature suggesting that residual effects of ecstasy (and reduced serotonin) impairs lateral inhibition between orientation-selective neurons in V1, which however suggests that ecstasy may not substantially affect this process in V2. Multiple studies have now demonstrated ecstasy-related deficits on basic visual functions, including orientation and motion processing. Such low-level effects may contribute to the impact of ecstasy use on neuropsychological tests of visuospatial function.
Aims/Objectives:A growing body of evidence suggests that regular ‘ecstasy’ (3,4-methylenedioxymethamphetamine) use causes lasting changes to central serotonergic functioning in humans, including in the occipital lobe. Serotonin may play a role in visual orientation processing, mediated in the occipital lobe, via lateral inhibition. The tilt aftereffect is an illusion apparent following adaptation to stimuli angled 5–50° from vertical and thought to be affected by lateral inhibition between occipital neurons. A recent study identified an enhanced tilt aftereffect among ecstasy users, but only in a subset that were recently abstinent from amphetamines. The current study examined the effects of ecstasy use, cannabis use and their interacting effect on the magnitude of the tilt aftereffect among participants with no recent history of amphetamine consumption. Materials and Methods: Eleven ecstasy users, 15 cannabis users, 15 ecstasy plus cannabis users and 15 drug-naïve controls were compared on the magnitude of the tilt aftereffect elicited following adaptation to stimuli angled 15, 30, 40 or 60° from vertical. Results:At a 40° adaptation condition, ecstasy users had a greater magnitude of the tilt aftereffect compared to those that had not taken the drug. Additionally, the extent of ecstasy use was positively associated with the magnitude of the tilt aftereffect generated following 15, 30 and 40° adaptation conditions, but not at 60°. Conclusions:Given that lateral inhibition mediates the tilt aftereffect following adaptation to 5–50°, the findings of a relationship between ecstasy use and tilt magnitude at the 15–40° but not 60° adaptation conditions support a role for serotonin in visual orientation processing via lateral inhibition.
Results were consistent with the proposal that ecstasy-related memory deficits are more reliable on tasks with greater cognitive complexity. This could arise either because such tasks require a greater contribution from the frontal lobe or because they require greater interaction between multiple brain regions.
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