Abnormal P600 in heroin addicts with prolonged abstinence elicited during a working memory test

Implicit Attitudes of New-Type Drug Abstainers towards New-Type Drugs and Their Relapse Tendencies

Over the last decade, new-type drugs have been replacing traditional-type drugs in China. However, studies of implicit attitudes towards new-type drugs are insufficient and contradictory results exist. Previous studies have suggested that implicit attitudes and relapse tendencies are a dual structure model, but that is for traditional or mixed drug addicts. For new drug addicts, is the dual structure model completely suitable or partially supported? This study attempts to explore this point. At a drug rehabilitation center, we randomly selected 50 abstainers (25 males and 25 females; age range: 21–41 years) who only took new-type drugs prior to abstention to participate in this study. Participants complete the General Situation Questionnaire, the Drug Use Characteristics Questionnaire, the Drug Relapse Risk Scale (DRRS), and the Single Category Implicit Association Test (SC-IAT). The relationship between implicit attitudes and relapse tendencies of new-type drug abstainers towards new-type drugs was investigated. The results showed: (1) abstainers had negative attitudes towards new-type drugs, and the data had statistical correlation with abstainers’ drug use characteristics and each relapse risk index; (2) females held relatively positive implicit attitudes towards new-type drugs; (3) being female and divorced could significantly predict abstainers’ implicit attitudes; (4) there is no significant correlation between implicit attitudes and relapse tendencies of new-type drug abstainers towards new-type drugs, which partially supports the dual structure model; (5) fender influences the self-assessment of relapse probability. Compared with traditional or mixed drug addicts, the dual structure model is only partially supported for new-type drug abstainers towards new-type drugs. That is because being female and divorced are the main factors influencing implicit attitudes and relapse tendencies. A few women or divorced people regard consuming new drugs as the source of happiness and forget the harm brought by the drugs themselves in their implicit attitude, which leads to more drug abuse in their explicit behavior. Therefore, we should pay more attention to women who have become new-type drug addicts and pay special attention to the impact of divorce.

Unraveling the Electrophysiological Activity Behind Recognition Memory

Abstract. Traditionally, most event related potential (ERP) studies of memory retrieval have been reported during item-recognition tasks. Those studies lead to two well-known ERP memory components termed FN400 (familiarity) and LPC (recollection). Nevertheless, some critics have raised concerns regarding the actual meaning of that activity since it emerges as the result of contrasting two different memory traces (previously studied vs. seen for the first time), and it is registered after the target presentation. Therefore, they possibly depict operations not related to memory itself but some cognitive processes associated with recognition memory. Based on those critics, we propose an innovative approach to study electrophysiological activity underlying recognition memory. We compared two very similar tasks with only one of them requiring subjects to actively retrieve a “cue-target” pair of visual stimuli from memory, while the other task required subjects to recognize the target stimulus as equal/different to the cue. Because of this experimental manipulation, we assured that active memory retrieval processes take place between the presentation of the cue and the target stimuli for only one of the tasks. As a result, responses upon the targets can give us valuable information regarding ERP components associated with recognition based on memory retrieval. We found three components possibly related to brain computations necessary to achieve correct target recognition. A N200-like component linked to executive functions (inhibition) from frontal cortices, a P300-like component, related to the expectation of the target stimulus, and a P600-like component associated to recognition based on LTM retrieval. These results help us to understand the complexity behind ERP components associated with recognition memory.

Forging Neuroimaging Targets for Recovery in Opioid Use Disorder

The United States is in the midst of an opioid epidemic and lacks a range of successful interventions to reduce this public health burden. Many individuals with opioid use disorder (OUD) consume drugs to relieve physical and/or emotional pain, a pattern that may increasingly result in death. The field of addiction research lacks a comprehensive understanding of physiological and neural mechanisms instantiating this cycle of Negative Reinforcement in OUD, resulting in limited interventions that successfully promote abstinence and recovery. Given the urgency of the opioid crisis, the present review highlights faulty brain circuitry and processes associated with OUD within the context of the Three-Stage Model of Addiction (1). This model underscores Negative Reinforcement processes as crucial to the maintenance and exacerbation of chronic substance use together with Binge/Intoxication and Preoccupation/Anticipation processes. This review focuses on cross-sectional as well as longitudinal studies of relapse and treatment outcome that employ magnetic resonance imaging (MRI), functional near-infrared spectroscopy (fNIRs), brain stimulation methods, and/or electroencephalography (EEG) explored in frequency and time domains (the latter measured by event-related potentials, or ERPs). We discuss strengths and limitations of this neuroimaging work with respect to study design and individual differences that may influence interpretation of findings (e.g., opioid use chronicity/recency, comorbid symptoms, and biological sex). Lastly, we translate gaps in the OUD literature, particularly with respect to Negative Reinforcement processes, into future research directions involving operant and classical conditioning involving aversion/stress. Overall, opioid-related stimuli may lessen their hold on frontocingulate mechanisms implicated in Preoccupation/Anticipation as a function of prolonged abstinence and that degree of frontocingulate impairment may predict treatment outcome. In addition, longitudinal studies suggest that brain stimulation/drug treatments and prolonged abstinence can change brain responses during Negative Reinforcement and Preoccupation/Anticipation to reduce salience of drug cues, which may attenuate further craving and relapse. Incorporating this neuroscience-derived knowledge with the Three-Stage Model of Addiction may offer a useful plan for delineating specific neurobiological targets for OUD treatment.

Acute effects of methadone on EEG power spectrum and event-related potentials among heroin dependents

Methadone as the most prevalent opioid substitution medication has been shown to influence the neurophysiological functions among heroin addicts. However, there is no firm conclusion on acute neuroelectrophysiological changes among methadone-treated subjects as well as the effectiveness of methadone in restoring brain electrical abnormalities among heroin addicts. This study aims to investigate the acute and short-term effects of methadone administration on the brain's electrophysiological properties before and after daily methadone intake over 10 weeks of treatment among heroin addicts. EEG spectral analysis and single-trial event-related potential (ERP) measurements were used to investigate possible alterations in the brain's electrical activities, as well as the cognitive attributes associated with MMN and P3. The results confirmed abnormal brain activities predominantly in the beta band and diminished information processing ability including lower amplitude and prolonged latency of cognitive responses among heroin addicts compared to healthy controls. In addition, the alteration of EEG activities in the frontal and central regions was found to be associated with the withdrawal symptoms of drug users. Certain brain regions were found to be influenced significantly by methadone intake; acute effects of methadone induction appeared to be associative to its dosage. The findings suggest that methadone administration affects cognitive performance and activates the cortical neuronal networks, resulting in cognitive responses enhancement which may be influential in reorganizing cognitive dysfunctions among heroin addicts. This study also supports the notion that the brain's oscillation powers and ERPs can be utilized as neurophysiological indices for assessing the addiction treatment traits.

High Working Memory Load Impairs Language Processing during a Simulated Piloting Task: An ERP and Pupillometry Study

Given the important amount of visual and auditory linguistic information that pilots have to process, operating an aircraft generates a high working-memory load (WML). In this context, the ability to focus attention on relevant information and to remain responsive to concurrent stimuli might be altered. Consequently, understanding the effects of WML on the processing of both linguistic targets and distractors is of particular interest in the study of pilot performance. In the present work, participants performed a simplified piloting task in which they had to follow one of three colored aircraft, according to specific written instructions (i.e., the written word for the color corresponding to the color of one of the aircraft) and to ignore either congruent or incongruent concurrent auditory distractors (i.e., a spoken name of color). The WML was manipulated with an n-back sub-task. Participants were instructed to apply the current written instruction in the low WML condition, and the 2-back written instruction in the high WML condition. Electrophysiological results revealed a major effect of WML at behavioral (i.e., decline of piloting performance), electrophysiological, and autonomic levels (i.e., greater pupil diameter). Increased WML consumed resources that could not be allocated to the processing of the linguistic stimuli, as indexed by lower P300/P600 amplitudes. Also, significantly, lower P600 responses were measured in incongruent vs. congruent trials in the low WML condition, showing a higher difficulty reorienting attention toward the written instruction, but this effect was canceled in the high WML condition. This suppression of interference in the high load condition is in line with the engagement/distraction trade-off model. We propose that P300/P600 components could be reliable indicators of WML and that they allow an estimation of its impact on the processing of linguistic stimuli.

A randomized controlled trial of the effects of working memory training in methadone maintenance patients

OBJECTIVE

Working memory impairment in individuals with chronic opioid dependence can play a major role in cognitive and treatment outcomes. Cognitive training targeting working memory shows promise for improved function in substance use disorders. To date, cognitive training has not been incorporated as an adjunctive treatment for opioid dependence.

METHODS

Methadone maintenance patients were randomly assigned to experimental (n=28) or active control (n=28) 25-session computerized training and run in parallel. Cognitive and drug use outcomes were assessed before and after training.

RESULTS

Participants in the experimental condition showed performance improvements on two of four working memory measures, and both groups improved on a third measure of working memory performance. Less frequent drug use was found in the experimental group than in the control group post-training. In contrast to previous findings with stimulant users, no significant effect of working memory training on delay discounting was found using either hypothetical or real rewards. There were no group differences on working memory outcome measures that were dissimilar from the training tasks, suggesting that another mechanism (e.g., increased distress tolerance) may have driven drug use results.

CONCLUSIONS

Working memory training improves performance on some measures of working memory in methadone maintenance patients, and may impact drug use outcomes. Working memory training shows promise in patients with substance use disorders; however, further research is needed to understand the mechanisms through which performance is improved and drug use outcomes are impacted.

Neuroimaging for drug addiction and related behaviors

In this review, we highlight the role of neuroimaging techniques in studying the emotional and cognitive-behavioral components of the addiction syndrome by focusing on the neural substrates subserving them. The phenomenology of drug addiction can be characterized by a recurrent pattern of subjective experiences that includes drug intoxication, craving, bingeing, and withdrawal with the cycle culminating in a persistent preoccupation with obtaining, consuming, and recovering from the drug. In the past two decades, imaging studies of drug addiction have demonstrated deficits in brain circuits related to reward and impulsivity. The current review focuses on studies employing positron emission tomography (PET), functional magnetic resonance imaging (fMRI), and electroencephalography (EEG) to investigate these behaviors in drug-addicted human populations. We begin with a brief account of drug addiction followed by a technical account of each of these imaging modalities. We then discuss how these techniques have uniquely contributed to a deeper understanding of addictive behaviors.

Forced exercise improves passive avoidance memory in morphine-exposed rats

The aim of this study was to investigate the effect of short-term forced exercise protocol on passive avoidance retention in morphine-exposed rats. Effects of morphine on acquisition and retrieval of retention have been proven in the avoidance paradigms. Twenty four male Wistar rats weighing 250-300 g were used in this study. Animals were randomly divided into four groups including: (1) non-morphine-exposed without exercise (nA.nE) (2) non-morphine-exposed with exercise (nA.E) (3) morphine-exposed without exercise (A.nE) and (4) morphine-exposed with exercise (A.E). Rats ran as forced exercise on the motorized treadmill 1 h daily for ten days. Morphine-exposed animals received intraperitoneal morphine during first 5 days of the exercise period and their dependence to morphine was confirmed by naloxane admistration (10 mg kg(-1), i.p.) and withdrawal test. After 10 days of forced exercise, step down latency was tested and Inflexion Ratio (IR) was evaluated in each rat. Baseline step down latencies before any morphine exposing or exercise have shown no significant alteration in all groups. Inflexion Ratio (IR) ofnA.E group has increased significantly (p<0.001) at 1, 3, 7 and 14 days after receiving shock (learning) compared to nA.nE and A.E groups. Our data showed that short-term forced exercise on treadmill improved retention in both morphine-exposed and non morphine-exposed rats at least up to 7 days and more than 14 days, respectively. Alteration in retention between exercised groups may attribute the release of adrenal stress hormones such as epinephrine and corticosterone because of the emotional arousal.

Recent EEG and ERP findings in substance abusers

Research on electroencephalographic (EEG) correlates of substance use has a long history. The present paper provides a review of recent studies--2001 to the present--with a focus on EEG findings in human participants characterized by a history of chronic substance use, abuse or dependence. In some areas (e.g., alcohol and cocaine dependence), the field has attempted to build upon earlier work by incorporating different methodologies or pursuing research questions of a transdisciplinary nature. New areas of inquiry, such as the investigation of EEG differences among users of ecstasy (MDMA) and methamphetamine, have emerged, primarily as a result of an alarming rise in popularity of these drugs.

Reorganization of the composition of brain oscillations and their temporal characteristics during opioid withdrawal

Majority of the opioid-dependence and withdrawal studies are dominated with many inconsistencies and contradictions. One of the reasons for such inconsistencies may be methodological while performing EEG analysis. To overcome methodological limitations, in the present study we examined the composition of electroencephalographic (EEG) brain oscillations in broad frequency band (0.5-30 Hz) in 13 withdrawal opioid-dependent patients and 14 healthy subjects during resting condition (closed eyes). The exact compositions of brain oscillations and their temporal behaviour were assessed by the probability-classification analysis of short-term EEG spectral patterns (SPs). It was reported that early withdrawal had a generalized effect: the activity in all EEG channels was affected nearly equally. EEG of withdrawal patients was characterized by (a) different dominant SP types (had unique SP types which describe beta-frequency band), (b) increased number of SP types observed in each EEG channel, (c) a larger percentage of alpha(2)-, beta- and poly-rhythmic activity, and by a smaller percentage of delta-, - and alpha(1)-rhythmic activity, (d) predominantly right-sided asymmetry and (e) longer periods of temporal stabilization for alpha- and beta-brain oscillations and by shorter periods of temporal stabilization for -activity when compared with control subjects. When taken together, these findings suggest a considerable reorganization of composition of brain oscillations, which reflects a disorganization process and an allostatic state with neuronal activation in EEG of opioid withdrawal patients.

EEG biofeedback as a treatment for substance use disorders: review, rating of efficacy, and recommendations for further research

Electroencephalographic (EEG) biofeedback has been employed in substance use disorder (SUD) over the last three decades. The SUD is a complex series of disorders with frequent comorbidities and EEG abnormalities of several types. EEG biofeedback has been employed in conjunction with other therapies and may be useful in enhancing certain outcomes of therapy. Based on published clinical studies and employing efficacy criteria adapted by the Association for Applied Psychophysiology and Biofeedback and the International Society for Neurofeedback and Research, alpha theta training-either alone for alcoholism or in combination with beta training for stimulant and mixed substance abuse and combined with residential treatment programs, is probably efficacious. Considerations of further research design taking these factors into account are discussed and descriptions of contemporary research are given.

Reorganization of the composition of brain oscillations and their temporal characteristics in opioid dependent patients

In the present study, we examined the composition of electroencephalographic (EEG) brain oscillations in broad frequency band (0.5-30 Hz) in 22 opioid-dependent patients and 14 healthy subjects during resting condition (closed eyes). The exact compositions of brain oscillations and their temporal behavior were assessed by the probability-classification analysis of short-term EEG spectral patterns. It was demonstrated that EEG of patients with opioid dependence was characterized by (a) significant reorganization of brain oscillations with increase in the percentage of beta- and mostly fast-alpha-rhythmic segments, (b) longer periods of temporal stabilization for alpha and beta brain oscillations and by shorter periods of temporal stabilization for theta and polyrhythmic activity when compared with control subjects, and (c) right-sided dominance (significantly larger relative presence of particular spectral patterns in EEG channels of the right hemisphere). These effects were widely distributed across the cortex with the maximum magnitude in the occipital, right parietal, temporal, and frontal areas. Taken together the present study suggested (a) an allostatic state with neuronal activation, and (b) high sensitivity of the right hemisphere to adverse opioid effects.

Treadmill running reverses retention deficit induced by morphine

Human and animal studies have suggested that exercise has benefits overall health and cognitive function. The aim of this study was to investigate the effect of treadmill running on passive avoidance learning and memory deficit in morphine-treated rats. The passive avoidance learning was measured in different time intervals (1, 2 and 24 h as well as 1 week and 1 month). Four groups of rats were included as follows: control, morphine-treated, exercised-saline and exercised-morphine-treated group. The electrical foot shock and treadmill training (2 h at a speed of 5 m/min for 10 days) were applied for all the groups. The data obtained was analyzed using unpaired Students t-test and ANOVA test with group as the independent variable, and performance in each session (avoidances and crossings) as the dependent variables. The results show that the total time staying in dark box was decreased in exercised-saline and exercised-morphine-treated rats by treadmill running (P<0.05). The avoidance learning was significantly reduced in morphine-treated group as indicated by the increased total time of staying in the dark box compared with the control group (P<0.05). We could conclude that exercise increased the delay time of entry to the dark electrical foot shock box, suggesting that morphine impaired the short-term memory and learning and this was reversed by the treadmill running.

Heroin abusers' performance on the Tower of London Test relates to the baseline EEG alpha2 mean frequency shifts

Planning function deficit is the most consistent finding in neuropsychological studies of heroin addicts. The performance on the Tower of London Test (TLT) correlated with the duration of daily heroin abuse (DDHA) in our previous study. Alpha2 mean frequency in anterior/central derivations was also predicted by DDHA in the same patient population. This retrospective study was undertaken in order to understand better the relationships between observed neurological deviations in heroin abusers. Thirty-three heroin addicts and 12 healthy males were evaluated with 14 neuropsychological tests and resting eyes-closed electroencephalography (EEG). Multivariate tests showed that performance on the difficult (five-move) problems of TLT was strongly predicted by the EEG alpha2 mean frequency shifts, and these relationships were generally mediated by chronic heroin length. However, post-hoc analyses at separate leads demonstrated that the relationships between cognitive variables and alpha2 mean frequencies in the left hemisphere were independent of chronic heroin effects, whereas elevation of alpha2 frequency in the right hemisphere was strongly predicted by chronic heroin intake length. The patients with extremely high alpha2 mean frequency at the left central region were especially prone to failure in TLT due to the inability of the hypothesized alpha2-generating network, which normally projects to the central and temporal derivations bilaterally and to the right posterior temporal derivation to function appropriately. Hence, it was concluded that planning dysfunction in heroin abusers is related to alpha2 mean frequency shifts predominantly at the central regions.

Working memory deficits in multiple sclerosis: a controlled study with auditory P600 correlates

BACKGROUND

Recently, the P600 component of event related potentials, a waveform that is conceived to be generated and/or modulated by basal ganglia and cingulate area has been considered an index of the completion of any synchronised operation after target detection, having much in common with working memory operation. Moreover, dysfunction of these brain structures as well as working memory deficits have been implicated in the pathophysiology of multiple sclerosis. The aim of this study was to investigate the patterns of P600 elicited during a working memory test in multiple sclerosis patients compared with healthy controls.

METHODS

Twenty two definite, chronic progressive multiple sclerosis patients, with recent exacerbation of their illness, and 20 normal subjects matched for age, sex, and educational level, were studied with a computerised version of the digit span test of Wechsler batteries. Auditory P600 were measured during the anticipatory period of this test.

RESULTS

The patient group, as compared with healthy controls, showed significantly reduced latencies of P600 at left frontal areas and reduced P600 amplitudes at left temporoparietal region. Moreover, memory performance of patients was significantly more impaired when compared with healthy controls.

CONCLUSIONS

These findings may indicate that multiple sclerosis is associated with abnormal features of the completion of synchronised operation after target detection, as they are reflected by P600 amplitudes and latencies. Dysfunction of this mechanism may contribute to the identification of basic cognitive processes that could account for the cognitive deficits in multiple sclerosis.

Abnormal P600 in obsessive-compulsive disorder. A comparison with healthy controls

Recently, the P600 component of the event-related potential (ERP), a waveform that is thought to be generated and/or modulated by the anterior cingulate gyrus and basal ganglia has been considered as an index of second pass-parsing processes of information processing, having much in common with working memory (WM) operation. Moreover, dysfunction of these brain structures as well as WM deficits have been implicated in the pathophysiology of obsessive-compulsive disorder (OCD). The present study is focused on P600 elicited during a WM test in OCD patients compared with healthy controls. Twenty drug-free OCD patients and an equal number of normal subjects matched for age, sex and educational level were studied via a computerized version of the Wechsler digit span test. Auditory P600 was measured during the anticipatory period of this test. The patient group, as compared with healthy controls, showed significantly enhanced amplitudes of P600 at the right temporoparietal area and prolonged latencies at the right parietal region. Moreover, the memory performance of patients was significantly impaired. These findings may indicate that OCD patients manifest abnormal aspects of second pass-parsing processes of information processing as they are reflected by P600 amplitudes and latencies.

Impaired P600 in neuroleptic naive patients with first-episode schizophrenia

Deficits of working memory (WM) are recognized as an important pathological feature in schizophrenia. Since the P600 component of event related potentials has been hypothesized that represents aspects of second-pass parsing processes of information processing, and is related to WM, the present study focuses on P600 elicited during a WM test in drug-naive first-episode schizophrenics (FES) compared to healthy controls. We examined 16 drug-naive first-episode schizophrenic patients and 23 healthy controls matched for age and sex. Compared with controls schizophrenic patients showed reduced P600 amplitude on left temporoparietal region and increased P600 amplitude on left occipital region. With regard to the latency, the patients exhibited significantly prolongation on right temporoparietal region. The obtained pattern of differences classified correctly 89.20% of patients. Memory performance of patients was also significantly impaired relative to controls. Our results suggest that second-pass parsing process of information processing, as indexed by P600, elicited during a WM test, is impaired in FES. Moreover, these findings lend support to the view that the auditory WM in schizophrenia involves or affects a circuitry including temporoparietal and occipital brain areas.