Objective. To analyze brain event-related responses in heroin-dependent patients under different emotional conditions, in order to determine the influence of specific emotional loading on information processing in drug addicts. Methods. Fifteen male heroin-dependent patients, matched to 11 male healthy individuals, were exposed to emotion-triggering slides designed to elicit neutral, pleasant or unpleasant emotions, while ERPs were obtained by means of an auditory oddball paradigm. Evoked potential analysis consisted of measuring the amplitude, latency, and topographic distribution ( mapped from 19 scalp sites) of the early and late latency component waveforms. Results. Both groups showed large-amplitude, long-latency, and positive-polarity responses to odd stimuli under all emotional conditions. A within-group comparison between the three emotional conditions showed that the control group had smaller P300 amplitudes under pleasant stimulation; drug addicts showed no differences between all three emotional conditions. Between-group analysis revealed smaller P300 amplitudes in drug addicts than in controls, both for unpleasant and neutral emotional conditions, but this was only significant for some electrode sites. Brain electrical activity mapping at P300 showed that high activation is less spread in the brain areas of drug addicts than in controls for unpleasant and neutral emotional conditions. Conclusion. Drug addicts have deficits in extracting relevant information from sensory stimuli under different emotional conditions, particularly under unpleasant and neutral stimulation. Decreased P300 in controls under pleasant stimulation is interpreted as a result of an attentional bias mechanism that directs attentional resources to environmental stimuli of positive emotional valence, in contrast to drug addicts where there is no such effect.
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