Abstract
The objective of this study was to verify hypothesised changes in event related potentials (visual mismatch negativity, v MMN) in 17 subjects dependent on methamphetamine (MAMP) compared to age and gender matched 17 healthy volunteers. We found a significant correlation between vMMN and duration of methamphetamine abuse (Spearman correlation coeficient r=0.54-0.78;P 0.05).
The positive correlation indicates drop of originally more negative response to deviant stimulus, what may indicate a pre-attentive processing enhancement in the first years of MAMP abuse with its decease later on. Accordingly, post-hoc analysis revealed significantly stronger vMMN in patients with length of MAMP abuse shorter than 5 years than in paired controls.
There were no such differences in abusers with the length of abuse longer than 5 years. The results show that the visual processing on the pre-attentional level can be influenced by long-term MAMP abuse, what can bi specifically assessed by vMMN.