Executive control for methadone maintenance patients: an event-related potential study

Abstract

Objective To discuss the neuropsychological mechanism of executive control for methadone maintenance patients( MMP). Methods Using the event-related potentials (ERPs) technique to reveal the time course of information processes with high temporal resolution, and exam the function of attention monitoring and response inhibition in heroin-dependent MMP. Results (1)The behavioral results: there were significant within-subjects Stroop interference effects for the MMP and control groups(reaction time: control group’s congruent condition(766.57±75.64)ms, incongruent condition(879.52±62.31)ms, MMP group’s congruent condition (821.89± 64.44)ms, incongruent condition(906.29±69.46)ms, P<0.001; error rate: control group’s congruent condition (4.15±2.92)%, incongruent condition(8.70±6.12)%, P<0.001, MMP group’s congruent condition(12.07±10.80)%, incongruent condition (16.60±12.43)%, P<0.01). (2)ERPs data showed that MMP demonstrated significantly smaller incongruent-N2/N450/SP amplitudes than controls, and all disappearing incongruent effects in N2, N450 and SP, comparing statistically significant incongruent effects for controls in N2, N450 and SP. In MMP group, the amplitudes of N2 and N450 incongruent condition(N2(1.40±2.91)μV、N450(1.29±0.55)μV) were bigger than congruent condition amplitudes(N2(0.77±3.61)μV、N450(0.83±1.07)μV, P<0.05), but the amplitude of SP (0.37±3.58)μV was smaller than congruent condition(1.53±3.05)μV, P<0.001; in control group, the amplitudes of N2 and N450 incongruent condition((-0.30±3.45)μV, N450(1.77±1.55)μV) were smaller than congruent condition (N2(1.10±3.64)μV, P<0.001; N450(2.37±2.12)μV, P<0.05), the amplitude of SP ((1.93±1.65)μV) was bigger than congruent condition((0.98±2.02)μV, P<0.01). Conclusion There are impaired executive control functions during the conflict monitoring process and the conflict resolution process for MMP. These results provide the neural electrophysiological evidence to explain relapse behaviors in methadone maintenance patients. Key words: Methadone maintenance patients; Stroop effect; Executive control; Event-related potentials