Biomedical subjects

Karen D Ersche

Publications and source records attributed to Karen D Ersche.

4 recordsLinked to original sources

PubMed2006

Differences in orbitofrontal activation during decision-making between methadone-maintained opiate users, heroin users and healthy volunteers.

OBJECTIVE: Previously, we reported that opiate users enrolled in methadone treatment made 'risky' choices on a decision-making task following a loss of points compared with heroin users and healthy volunteers. One possible explanation for this behaviour is that methadone users were less sensitive to punishment on immediately preceding unsuccessful trials. METHODS: We sought to explore this finding from a neural perspective by performing a post hoc analysis of data from a previous [see text] positron emission tomography study. We restricted the analysis to the opiate groups and controls, assessing differences between opiate users on methadone and those on heroin. RESULTS: We found significant over-activation in the lateral orbitofrontal cortex (OFC) in methadone users compared with both heroin users and controls concomitant with the greatest overall tendency to 'play risky'. Heroin users showed significant under-activation in this area compared with the other two groups whilst exhibiting the greatest overall tendency to 'play safe'. Correlational analysis revealed that abnormal task-related activation of the left OFC was associated with the dose of methadone in methadone users and with the duration of intravenous heroin use in heroin users. 'Playing safe' following a loss of points was also negatively correlated with the activation of pregenual anterior cingulate and insula cortex in controls, but not in opiate users. CONCLUSION: Our findings suggest that the interplay between processes involved in integrating penalty information for the purpose of response selection may be altered in opiate users. This change was reflected differentially in task-related pattern of OFC activation depending on the opiate used.

Adult↗

PubMed2006

Reflection impulsivity in current and former substance users.

BACKGROUND: Chronic drug use is associated with increased impulsivity, risky decision making, and impaired behavioral control, but the underlying mechanisms of this neurocognitive profile remain unclear. We investigated impulsive responding in the context of decision making, using a novel behavioral measure of reflection impulsivity: the tendency to gather and evaluate information before making a decision. METHODS: The Information Sampling Task was administered to current substance users dependent on amphetamines (n = 24) or opiates (n = 40), former users of amphetamines or opiates abstinent for at least 1 year (n = 24), and non-drug-using control subjects (n = 26). RESULTS: Current users of amphetamines and opiates sampled less information than control subjects and responded at a lower probability of making a correct response. Amphetamine- and opiate-dependent subjects did not differ. Reduced reflection was also apparent in the former substance users, who did not differ from the current users. Questionnaire ratings of impulsivity (on the Barratt Impulsivity Scale, version 11) were also inflated in three groups of substance users but were not significantly correlated with performance on the behavioral task. CONCLUSIONS: Reduced reflection is suggested to represent a cognitive marker for substance dependence that does not recover with prolonged abstinence and is associated with multiple drugs of abuse.

Adult↗

PubMed2006

Profile of executive and memory function associated with amphetamine and opiate dependence.

Cognitive function was assessed in chronic drug users on neurocognitive measures of executive and memory function. Current amphetamine users were contrasted with current opiate users, and these two groups were compared with former users of these substances (abstinent for at least one year). Four groups of participants were recruited: amphetamine-dependent individuals, opiate-dependent individuals, former users of amphetamines, and/or opiates and healthy non-drug taking controls. Participants were administered the Tower of London (TOL) planning task and the 3D-IDED attentional set-shifting task to assess executive function, and Paired Associates Learning and Delayed Pattern Recognition Memory tasks to assess visual memory function. The three groups of substance users showed significant impairments on TOL planning, Pattern Recognition Memory and Paired Associates Learning. Current amphetamine users displayed a greater degree of impairment than current opiate users. Consistent with previous research showing that healthy men are performing better on visuo-spatial tests than women, our male controls remembered significantly more paired associates than their female counterparts. This relationship was reversed in drug users. While performance of female drug users was normal, male drug users showed significant impairment compared to both their female counterparts and male controls. There was no difference in performance between current and former drug users. Neither years of drug abuse nor years of drug abstinence were associated with performance. Chronic drug users display pronounced neuropsychological impairment in the domains of executive and memory function. Impairment persists after several years of drug abstinence and may reflect neuropathology in frontal and temporal cortices.

Adult↗

PubMed2005

Punishment induces risky decision-making in methadone-maintained opiate users but not in heroin users or healthy volunteers.

Reinforcing properties of psychoactive substances are considered to be critically involved in the development and maintenance of substance dependence. While accumulating evidence suggests that the sensitivity to reinforcement values may generally be altered in chronic substance users, relatively little is known about the influence reinforcing feedback exerts on ongoing decision-making in these individuals. Decision-making was investigated using the Cambridge Risk Task, in which there is a conflict between an unlikely large reward option and a likely small reward option. Responses on a given trial were analyzed with respect to the outcome on the previous trial, providing a measure of the impact of prior feedback in modulating behavior. Five different groups were compared: (i) chronic amphetamine users, (ii) chronic opiate users in methadone maintenance treatment (MMT), (iii) chronic users of illicit heroin, (iv) ex-drug users who had been long-term amphetamine / opiate users but were abstinent from all drugs of abuse for at least 1 year and (v) matched controls without a history of illicit substance use. Contrary to our predictions, choice preference was modified in response to feedback only in opiate users enrolled in MMT. Following a loss, the MMT opiate group chose the likely small reward option significantly less frequently than controls and heroin users. Our results suggest that different opiates are associated with distinctive behavioral responses to feedback. These findings are discussed with respect to the different mechanisms of action of heroin and methadone. Neuropsychopharmacology (2005) 30, 2115-2124. doi:10.1038/sj.npp.1300812; published online 6 July 2005.

Adult↗