An influential model suggests that dopamine signals the difference between predicted and experienced reward. In this way, dopamine can act as a learning signal that can shape behaviors to maximize rewards and avoid punishments. Dopamine is also thought to invigorate reward seeking behavior. Loss of dopamine signaling is the major abnormality in Parkinson’s disease. Dopamine agonists have been implicated in the occurrence of impulse control disorders in Parkinson’s disease patients, the most common being pathological gambling, compulsive sexual behavior, and compulsive buying. Recently, a number of functional imaging studies investigating impulse control disorders in Parkinson’s disease have been published. Here we review this literature, and attempt to place it within a decision-making framework in which potential gains and losses are evaluated to arrive at optimum choices. We also provide a hypothetical but still incomplete model on the effect of dopamine agonist treatment on these value and risk assessments. Two of the main brain structures thought to be involved in computing aspects of reward and loss are the ventral striatum (VStr) and the insula, both dopamine projection sites. Both structures are consistently implicated in functional brain imaging studies of pathological gambling in Parkinson’s disease.
impulse control disorders; impulsivity; reward; loss aversion; insula; ventral striatum
Impulse control disorders are a psychiatric condition characterized by the failure to resist an impulsive act or behavior that may be harmful to self or others. In movement disorders, impulse control disorders are associated with dopaminergic treatment, notably dopamine agonists (DAs). Impulse control disorders have been studied extensively in Parkinson’s disease, but are also recognized in restless leg syndrome and atypical Parkinsonian syndromes. Epidemiological studies suggest younger age, male sex, greater novelty seeking, impulsivity, depression and premorbid impulse control disorders as the most consistent risk factors. Such patients may warrant special monitoring after starting treatment with a DA. Various individual screening tools are available for people without Parkinson’s disease. The Questionnaire for Impulsive-Compulsive Disorders in Parkinson’s Disease has been developed specifically for Parkinson’s disease. The best treatment for impulse control disorders is prevention. However, after the development of impulse control disorders, the mainstay intervention is to reduce or discontinue the offending anti-Parkinsonian medication. In refractory cases, other pharmacological interventions are available, including neuroleptics, antiepileptics, amantadine, antiandrogens, lithium and opioid antagonists. Unfortunately, their use is only supported by case reports, small case series or open-label clinical studies. Prospective, controlled studies are warranted. Ongoing investigations include naltrexone and nicotine.
Impulse control disorders; Parkinson’s disease; restless leg syndrome; parkinsonism; dopamine agonist; non-motor complication; neurobehavioural
Dopamine replacement therapy for Parkinson’s disease (PD) was recently linked to the development of impulse control disorders such as pathological gambling (PG), hypersexuality, compulsive shopping, and binge or compulsive eating. Antiglutamatergic agents including amantadine (Ama) reduce these behaviors in PD and non-PD patients. The aim of our study is to evaluate the changes in executive functions, emotions, and reward/loss processing during Ama treatment in PD patients.
Thirty-three patients affected by idiopathic PD were selected from a cohort of 1,096 PD patients and categorized in three different groups: ten affected by PG (PD-PG); nine PD patients with other impulse control disorder (PD-ICD); and 14 PD patient without any psychiatric disorder (PD-CTR-controls). For the neuropsychological evaluation, the following behavioral tasks where administered: the Stroop, the emotional Stroop, and the monetary reward/loss risk-taking tasks.
During Ama treatment, PD-PGs showed a decrease in risky choices and an increase in non-risky choices (t(9)=−2.40, P<0.05 and t(9)=2,67, P<0.05 uncorrected, respectively). Between-group comparison showed a significant decrease in risky choices for PD-PG with respect to PD-CTR (t(22)=−4.16, P<0.01), and a decreased accuracy for positive words in comparison between PD-PG and PD-ICD (t(17)=−7,49, P<0.01) and PD-PG and PD-CTR (t(22)=−4.29, P<0.01). No within- and between-group differences were observed for Stroop task.
Our data showed that Ama add-on therapy reduces hypersensitivity to reward and sustains activation toward uncertainty in PD-PG patients. These finding might explain the behavioral mechanism underlying the effect of antiglutamatergic drugs.
Parkinson’s disease; executive functions; emotion
Purpose of review
To review the recent advances in the epidemiology and pathophysiology of impulse control disorders (ICD) in Parkinson’s disease (PD).
Large cross-sectional and case-control multicentre studies show that ICDs in PD are common with a frequency of 13.6%. These behaviours are associated with impaired functioning and with depressive, anxiety and obsessive symptoms, novelty seeking and impulsivity. Behavioural subtypes demonstrate differences in novelty seeking and impulsivity suggesting pathophysiological differences. Observational and neurophysiological studies point towards a potential mechanistic overlap between the behavioural (ICDs) and motor (dyskinesias) dopaminergic sequelae. Converging data suggest dopamine agonists in ICDs appear to enhance learning from rewarding outcomes and impulsive choice. ICD patients also have enhanced risk preference and impaired working memory. Neuroimaging data points towards enhanced bottom-up ventral striatal dopamine release to incentive cues, gambling tasks and reward prediction, and possibly inhibition of top-down orbitofrontal influences. Dopamine agonist-related ventral striatal hypoactivity to risk is consistent with impaired risk evaluation.
Recent large scale studies and converging findings are beginning to provide an understanding of mechanisms underlying ICDs in PD which can guide prevention of these behaviours and optimize therapeutic approaches.
Impulse control disorders; Parkinson’s disease; dopamine agonists; pathological gambling; impulsivity
Pathological gambling is an impulse control disorder reported in association with dopamine agonists used to treat Parkinson’s disease. Although impulse control disorders are conceptualized as lying within the spectrum of addictions, little neurobiological evidence exists to support this belief. Functional imaging studies have consistently demonstrated abnormalities of dopaminergic function in patients with drug addictions, but to date no study has specifically evaluated dopaminergic function in Parkinson’s disease patients with impulse control disorders. We describe results of a [11C] raclopride positron emission tomography (PET) study comparing dopaminergic function during gambling in Parkinson’s disease patients, with and without pathological gambling, following dopamine agonists. Patients with pathological gambling demonstrated greater decreases in binding potential in the ventral striatum during gambling (13.9%) than control patients (8.1%), likely reflecting greater dopaminergic release. Ventral striatal bindings at baseline during control task were also lower in patients with pathological gambling. Although prior imaging studies suggest that abnormality in dopaminergic binding and dopamine release may be markers of vulnerability to addiction, this study presents the first evidence of these phenomena in pathological gambling. The emergence of pathological gambling in a number of Parkinson’s disease patients may provide a model into the pathophysiology of this disorder.
PMID: 19346328 CAMSID: cams2369
Parkinson’s disease; dopamine; impulse control disorders; pathological gambling; PET; functional imaging
Clinical reports, primarily with Parkinson’s patients, note an association between the prescribed use of pramipexole (and other direct-acting dopamine agonist medications) and impulse control disorders, particularly pathological gambling. Two experiments examined the effects of acute pramipexole on rats’ impulsive choices where impulsivity was defined as selecting a smaller-sooner over a larger-later food reward. In Experiment 1, pramipexole (0.1 to 0.3 mg/kg) significantly increased impulsive choices in a condition in which few impulsive choices were made during a stable baseline. In a control condition, in which impulsive choices predominated during baseline, pramipexole did not significantly change the same rats’ choices. Experiment 2 explored a wider range of doses (0.01 to 0.3 mg/kg) using a choice procedure in which delays to the larger-later reinforcer delivery increased across trial blocks within each session. At the doses used in Experiment 1, pramipexole shifted choice toward indifference regardless of the operative delay. At lower doses of pramipexole (0.01 & 0.03 mg/kg), a trend toward more impulsive choice was observed at the 0.03 mg/kg dose. The difference in outcomes across experiments may be due to the more complex discriminations required in Experiment 2; i.e., multiple discriminations between changing delays within each session.
Pramipexole; D2/D3 agonist; Impulsivity; Choice; Gambling
To determine the frequency and correlates of impulse control disorders (ICDs) in Parkinson’s disease (PD).
An unstructured screening interview for ICDs (compulsive gambling, buying, and sexual behavior) followed by a telephone-administered structured interview for screen-positive patients.
Two university-affiliated movement disorders centers.
A convenience sample of 272 patients with idiopathic PD who were screened for psychiatric complications.
Main Outcome Measures
Presence of compulsive gambling, buying, or sexual behavior as assessed by the Minnesota Impulsive Disorders Interview.
Eighteen (6.6%) PD patients met criteria for an ICD at some point during the course of PD, including 11 (4.0%) with an active ICD. Compulsive gambling and compulsive sexual behavior were equally common. In a multivariate model, treatment with a dopamine agonist (P = .01) and a history of ICD symptomatology prior to PD onset (P = .02) predicted current ICD. There were no differences between the dopamine agonists in their association with ICDs (P = .21), and daily doses of dopamine agonists were higher in patients with an ICD than in dopamine agonist-treated patients without an ICD (P < .001).
PD patients treated with a dopamine agonist should be made aware of the risk of developing an ICD and monitored clinically. As dopamine agonists are increasing being used for other indications, future research should assess the dopamine agonist-associated risk for ICDs in other populations.
We recently reported that the D2/D3 agonist pramipexole may have pro-cognitive effects in euthymic patients with bipolar disorder (BPD); however, the emergence of impulse-control disorders has been documented in Parkinson's disease (PD) after pramipexole treatment. Performance on reward-based tasks is altered in healthy subjects after a single dose of pramipexole, but its potential to induce abnormalities in BPD patients is unknown. We assessed reward-dependent decision making in euthymic BPD patients pre- and post 8 weeks of treatment with pramipexole or placebo by using the Iowa Gambling Task (IGT). The IGT requires subjects to choose among four card decks (two risky and two conservative) and is designed to promote learning to make advantageous (conservative) choices over time. Thirty-four BPD patients completed both assessments (18 placebo and 16 pramipexole). Baseline performance did not differ by treatment group (F=0.63; p=0.64); however, at week 8, BPD patients on pramipexole demonstrated a significantly greater tendency to make increasingly high-risk, high-reward choices across the five blocks, whereas the placebo group's pattern was similar to that reported in healthy individuals (treatment × time × block interaction, p<0.05). Analyses of choice strategy using the expectancy valence model revealed that after 8 weeks on pramipexole, BPD patients attended more readily to feedback related to gains than to losses, which could explain the impaired learning. There were no significant changes in mood symptoms over the 8 weeks, and no increased propensity toward manic-like behaviors were reported. Our results suggest that the enhancement of dopaminergic activity influences risk-associated decision-making performance in euthymic BPD. The clinical implications remain unknown.
Behavioral Science; bipolar disorder; decision-making; Dopamine; gambling; Mood/Anxiety/Stress Disorders; Neuropharmacology; pramipexole; bipolar disorder; dopamine; pramipexole; decision-making
Risk-taking behavior is characterized by pursuit of reward in spite of potential negative consequences. Dopamine neurotransmission along the mesocorticolimbic pathway is a potential modulator of risk behavior. In patients with Parkinson's Disease (PD), impulse control disorder (ICD) can result from dopaminergic medication use, particularly Dopamine Agonists (DAA). Behaviors associated with ICD include hypersexuality as well as compulsive gambling, shopping, and eating, and are potentially linked to alterations to risk processing. Using the Balloon Analogue Risk task, we assessed the role of agonist therapy on risk-taking behavior in PD patients with (n=22) and without (n=19) active ICD symptoms. Patients performed the task both ‘on’ and ‘off’ DAA. DAA increased risk-taking in PD patients with active ICD symptoms, but did not affect risk behavior of PD controls. DAA dose was also important in explaining risk behavior. Both groups similarly reduced their risk-taking in high compared to low risk conditions and following the occurrence of a negative consequence, suggesting that ICD patients do not necessarily differ in their ability to process and adjust to some aspects of negative consequences. Our findings suggest dopaminergic augmentation of risk-taking behavior as a potential contributing mechanism for the emergence of ICD in PD patients.
Impulse Control Disorders; Dopamine Agonists; Parkinson Disease; Risk behavior
There is an increasing awareness that impulse control disorders (ICDs), including compulsive gambling, buying, sexual behavior, and eating, can occur as a complication of Parkinson’s disease (PD). In addition, other impulsive or compulsive disorders have been reported to occur, including dopamine dysregulation syndrome (DDS) and punding. Case reporting and prospective studies have reported an association between ICDs and the use of dopamine agonists (DAs), particularly at greater dosages, whereas dopamine dysregulation syndrome has been associated with greater dosages of levodopa or short-acting DAs. Data suggest that risk factors for an ICD may include male sex, younger age or younger age at PD onset, a pre-PD history of ICD symptoms, personal or family history of substance abuse or bipolar disorder, and a personality style characterized by impulsiveness. Although psychiatric medications are used clinically in the treatment of ICDs, there is no empiric evidence supporting their use in PD. Therefore, management for clinically significant ICD symptoms should consist of modifications to dopamine replacement therapy, particularly DAs, and there is emerging evidence that such management is associated with an overall improvement in ICD symptomatology. It is important that PD patients be aware that DA use may lead to the development of an ICD, and that clinicians monitor patients as part of routine clinical care. As empirically validated treatments for ICDs are emerging, it will be important to examine their efficacy and tolerability in individuals with cooccurring PD and ICDs.
Some patients with Parkinson disease (PD) develop pathological gambling when treated with dopamine agonists (DAs). However, little is known about DA-induced changes in neuronal networks that may underpin this drug-induced change in behavior in vulnerable individuals. In this case-control study, we aimed to investigate DA-induced changes in brain activity that may differentiate patients with PD with DA-induced pathological gambling (gamblers) from patients with PD without such a history (controls).
Following overnight withdrawal of antiparkinsonian medication, patients were studied with H2
15O PET before and after administration of DA (3 mg apomorphine) to measure changes in regional cerebral blood flow as an index of regional brain activity during a card selection game with probabilistic feedback.
We observed that the direction of DA-related activity change in brain areas that are implicated in impulse control and response inhibition (lateral orbitofrontal cortex, rostral cingulate zone, amygdala, external pallidum) distinguished gamblers from controls. DA significantly increased activity in these areas in controls, while gamblers showed a significant DA-induced reduction of activity.
We propose that in vulnerable patients with PD, DAs produce an abnormal neuronal pattern that resembles those found in nonparkinsonian pathological gambling and drug addiction. DA-induced disruption of inhibitory key functions—outcome monitoring (rostral cingulate zone), acquisition and retention of negative action-outcome associations (amygdala and lateral orbitofrontal cortex)—together with restricted access of those areas to executive control (external pallidum)—may well explain loss of impulse control and response inhibition in vulnerable patients with PD, thereby fostering the development of pathological gambling.
= analysis of variance;
= dopamine agonist;
= Gambling Symptom Assessment Scale;
= external pallidum;
= Montréal Neurological Institute;
= orbitofrontal cortex;
= Parkinson disease;
= regional cerebral blood flow;
= rostral cingulated zone;
= Unified Parkinson's Disease Rating Scale.
Dopaminergic medication-related Impulse Control Disorders (ICDs) such as pathological gambling and compulsive shopping have been reported in Parkinson disease (PD).
We hypothesized that dopamine agonists (DAs) would be associated with greater impulsive choice, or greater discounting of delayed rewards, in PD patients with ICDs (PDI).
Fourteen PDI patients, 14 PD controls without ICDs and 16 medication-free matched normal controls were tested on (i) the Experiential Discounting Task (EDT), a feedback-based intertemporal choice task, (ii) spatial working memory and (iii) attentional set shifting. The EDT was used to assess impulsivity choice (hyperbolic K-value), reaction time (RT) and decision conflict RT (the RT difference between high conflict and low conflict choices). PDI patients and PD controls were tested on and off DA.
On the EDT, there was a group by medication interaction effect [F(1,26)=5.62; p=0.03] with pairwise analyses demonstrating that DA status was associated with increased impulsive choice in PDI patients (p=0.02) but not in PD controls (p=0.37). PDI patients also had faster RT compared to PD controls F(1,26)=7.51 p=0.01]. DA status was associated with shorter RT [F(3,24)=8.39, p=0.001] and decision conflict RT [F(1,26)=6.16, p=0.02] in PDI patients but not in PD controls. There were no correlations between different measures of impulsivity. PDI patients on DA had greater spatial working memory impairments compared to PD controls on DA (t=2.13, df=26, p=0.04).
Greater impulsive choice, faster RT, faster decision conflict RT and executive dysfunction may contribute to ICDs in PD.
dopamine agonist; gambling; impulse control; Parkinson disease; delay discounting
Impulse control disorders (ICD) (most commonly pathologic gambling, hypersexuality, and uncontrollable spending) and compulsive behaviors can be triggered by dopaminergic therapies in Parkinson disease (PD). ICD are especially prevalent in patients receiving a dopamine agonist as part of their treatment regimen for PD, and have also been reported when dopamine agonists are used for other indications (e.g., restless legs syndrome). Although these iatrogenic disorders are common, affecting 1 in 7 patients with PD on dopamine agonists, they often elude detection by the treating physician. ICD lead to serious consequences, causing significant financial loss and psychosocial morbidity for many patients and families. ICD can appear at any time during treatment with dopamine agonists, sometimes within the first few months, but most often after years of treatment, particularly when patients receive dopamine agonists and levodopa together. In most cases ICD resolve if the dopamine agonist is withdrawn, and PD motor symptoms are managed with levodopa monotherapy. Familiarity with the clinical aspects, risk factors, pathophysiology, and management of ICD is essential for physicians using dopaminergic therapies to treat PD and other disorders.
Impulse control disorders (ICDs), including disordered gambling, can occur in a significant number of patients with Parkinson’s disease (PD) receiving dopaminergic therapy. The neurobiology underlying susceptibility to such problems is unclear, but risk likely results from an interaction between dopaminergic medication and a pre-existing trait vulnerability. Impulse control and addictive disorders form part of a broader psychopathological spectrum of disorders, which share a common underlying genetic vulnerability, referred to as externalizing. The broad externalizing risk factor is a continuously varying trait reflecting vulnerability to various impulse control problems, manifested at the overt level by disinhibitory symptoms and at the personality level by antecedent traits such as impulsivity and novelty/sensation seeking. Trait “disinhibition” is thus a core endophenotype of ICDs, and a key target for neurobiological investigation. The ventral striatal dopamine system has been hypothesized to underlie individual variation in behavioral disinhibition. Here, we examined whether individual differences in ventral striatal dopamine synthesis capacity predicted individual variation in disinhibitory temperament traits in individuals with PD. Eighteen early-stage male PD patients underwent 6-[18F]Fluoro-l-DOPA (FDOPA) positron emission tomography scanning to measure striatal dopamine synthesis capacity, and completed a measure of disinhibited personality. Consistent with our predictions, we found that levels of ventral, but not dorsal, striatal dopamine synthesis capacity predicted disinhibited personality, particularly a propensity for financial extravagance. Our results are consistent with recent preclinical models of vulnerability to behavioral disinhibition and addiction proneness, and provide novel insights into the neurobiology of potential vulnerability to impulse control problems in PD and other disorders.
dopa decarboxylase; dopamine; disordered gambling; externalizing; impulse control disorders; impulsivity; reward; ventral striatum
Impulse control disorders such as pathological gambling (PG) are a serious and common adverse effect of dopamine (DA) replacement medication in Parkinson’s disease (PD). Patients with PG have increased impulsivity and abnormalities in striatal DA, in common with behavioural and substance addictions in the non-PD population. To date, no studies have investigated the role of extrastriatal dopaminergic abnormalities in PD patients with PG. We used the PET radiotracer, [11C] FLB-457, with high-affinity for extrastriatal DA D2/3 receptors. 14 PD patients on DA agonists were imaged while they performed a gambling task involving real monetary reward and a control task. Trait impulsivity was measured with the Barratt Impulsivity Scale (BIS). Seven of the patients had a history of PG that developed subsequent to DA agonist medication. Change in [11C] FLB-457 binding potential (BP) during gambling was reduced in PD with PG patients in the midbrain, where D2/D3 receptors are dominated by autoreceptors. The degree of change in [11C] FLB-457 binding in this region correlated with impulsivity. In the cortex, [11C] FLB-457 BP was significantly greater in the anterior cingulate cortex (ACC) in PD patients with PG during the control task, and binding in this region was also correlated with impulsivity. Our findings provide the first evidence that PD patients with PG have dysfunctional activation of DA autoreceptors in the midbrain and low DA tone in the ACC. Thus, altered striatal and cortical DA homeostasis may incur vulnerability for the development of PG in PD, linked with the impulsive personality trait.
PMID: 22766031 CAMSID: cams2373
Parkinson’s disease; Dopamine agonists; Pathological gambling; Impulsivity
Pramipexole and other direct dopamine agonist medications have been implicated in the development of impulsive behavior such as pathological gambling among those taking the drug to control symptoms of Parkinson’s disease or restless leg syndrome. Few laboratory studies examining pramipexole’s effects on gambling-like behavior have been conducted.
The present study used a rodent model approximating some aspects of human gambling to examine within-subject effects of acute pramipexole (0.03, 0.1, 0.18, & 0.3 mg/kg) on rat’s choices to earn food reinforcement by completing variable-ratio (i.e., gambling-like) or fixed-ratio response requirements.
In a condition in which the variable-ratio alternative was rarely selected, all but the lowest dose of pramipexole significantly increased choice of the variable-ratio alternative (an average of 15% above saline).. The same doses did not affect choice significantly in a control condition designed to evaluate the involvement of nonspecific drug effects. Pramipexole increased latencies to initiate trials (+ 9.12 s) and to begin response runs on forced-choice trials (variable-ratio: + 0.21 s; fixed-ratio: + 0.88 s), but did not affect measures of response perseveration (conditional probabilities of “staying”).
The findings are consistent with clinical reports linking pramipexole to the expression of increased gambling in humans. Results are discussed in the context of neurobehavioral evidence suggesting that dopamine agonists increase sensitivity to reward delay and disrupt appropriate feedback from negative outcomes.
pramipexole; dopamine agonist; gambling; impulsive behavior; Parkinson’s disease; rat
Background: Impulsive and compulsive behaviors (ICBs) are a heterogeneous group of conditions that may be caused by long-term dopaminergic replacement therapy (DRT) of Parkinson’s disease (PD). The spectrum of ICBs includes dopamine dysregulation syndrome (DDS), punding, and impulse control disorders (ICDs).
Contents: We made a detailed review regarding the epidemiology, pathology, clinical characteristics, risk factors, diagnosis as well as treatment of ICBs.
Results: The prevalence of ICBs in PD patients is approximately 3–4% for DDS, 0.34–4.2% for punding, and 6–14% for ICDs, with higher prevalence in Western populations than in Asian. Those who take high dose of levodopa are more prone to have DDS, whereas, ICDs are markedly associated with dopamine agonists. Different subtypes of ICBs share many risk factors such as male gender, higher levodopa equivalent daily dose, younger age at PD onset, history of alcoholism, impulsive, or novelty-seeking personality. The Questionnaire for Impulsive–Compulsive Disorder in Parkinson’s Disease-Rating Scale seems to be a rather efficacious instrument to obtain relevant information from patients and caregivers. Treatment of ICBs is still a great challenge for clinicians. Readjustment of DRT remains the primary method. Atypical antipsychotics, antidepressants, amantadine, and psychosocial interventions are also prescribed in controlling episodes of psychosis caused by compulsive DRT, but attention should be drawn to balance ICBs symptoms and motor disorders. Moreover, deep brain stimulation of the subthalamic nucleus might be a potential method in controlling ICBs.
Conclusion: The exact pathophysiological mechanisms of ICBs in PD remains poorly understood. Further researches are needed not only to study the pathogenesis, prevalence, features, and risk factors of ICBs, but to find efficacious therapy for patients with these devastating consequences.
Parkinson disease; impulsive control disorders; dopamine dysregulation syndrome; review; dopaminergic replacement therapy
Impulse control disorders are commonly associated with dopaminergic therapy in Parkinson's disease (PD). PD patients with impulse control disorders demonstrate enhanced dopamine release to conditioned cues and a gambling task on [11C]raclopride positron emission tomography (PET) imaging and enhanced ventral striatal activity to reward on functional MRI. We compared PD patients with impulse control disorders and age-matched and gender-matched controls without impulse control disorders using [123I]FP-CIT (2β-carbomethoxy-3β-(4-iodophenyl)tropane) single photon emission computed tomography (SPECT), to assess striatal dopamine transporter (DAT) density.
The [123I]FP-CIT binding data in the striatum were compared between 15 PD patients with and 15 without impulse control disorders using independent t tests.
Those with impulse control disorders showed significantly lower DAT binding in the right striatum with a trend in the left (right: F(1,24)=5.93, p=0.02; left: F(1,24)=3.75, p=0.07) compared to controls.
Our findings suggest that greater dopaminergic striatal activity in PD patients with impulse control disorders may be partly related to decreased uptake and clearance of dopamine from the synaptic cleft. Whether these findings are related to state or trait effects is not known. These findings dovetail with reports of lower DAT levels secondary to the effects of methamphetamine and alcohol. Although any regulation of DAT by antiparkinsonian medication appears to be modest, PD patients with impulse control disorders may be differentially sensitive to regulatory mechanisms of DAT expression by dopaminergic medications.
BEHAVIOURAL DISORDER; FUNCTIONAL IMAGING; NEUROPSYCHIATRY; SPECT; MOVEMENT DISORDERS
Dopaminergic medication for motor symptoms in Parkinson’s disease (PD) recently has been linked with impulse control disorders, including pathological gambling (PG), which affects up to 8% of patients. PG often is considered a behavioral addiction associated with disinhibition, risky decision-making, and altered striatal dopaminergic neurotransmission. Using [11C]raclopride with positron emission tomography, we assessed dopaminergic neurotransmission during Iowa Gambling Task performance. Here we present data from a single patient with PD and concomitant PG. We noted a marked decrease in [11C]raclopride binding in the left ventral striatum upon gambling, indicating a gambling-induced dopamine release. The results imply that PG in PD is associated with a high dose of dopaminergic medication, pronounced motor symptomatology, young age at disease onset, high propensity for sensation seeking, and risky decision-making. Overall, the findings are consistent with the hypothesis of medication-related PG in PD and underscore the importance of taking clinical variables, such as age and personality, into account when patients with PD are medicated, to reduce the risk of PG.
Parkinson’s disease; pathological gambling; impulse control disorders; decision-making; dopamine
Low doses of dopamine agonists (DA) and levodopa are effective in the treatment of restless legs syndrome (RLS). A range of impulse control and compulsive behaviours (ICBs) have been reported following the use of DAs and levodopa in patients with Parkinson's disease. With this study we sought to assess the cross-sectional prevalence of impulse control behaviours (ICBs) in restless legs syndrome (RLS) and to determine factors associated with ICBs in a population cohort in Germany.
Several questionnaires based on validated and previously used instruments for assessment of ICBs were mailed out to patients being treated for RLS. Final diagnoses of ICBs were based on stringent diagnostic criteria after psychiatric interviews were performed.
10/140 RLS patients of a clinical cohort (7.1%) were finally diagnosed with ICBs, 8 of 10 on dopamine agonist (DA) therapy, 2 of 10 on levodopa. 8 of the 10 affected patients showed more than one type of abnormal behaviour. Among those who responded to the questionnaires 6/140 [4.3%] revealed binge eating, 5/140 [3.6%] compulsive shopping, 3/140 [2.1%] pathological gambling, 3/140 [2.1%] punding, and 2/140 [1.4%] hypersexuality in psychiatric assessments. Among those who did not respond to questionnaires, 32 were randomly selected and interviewed: only 1 patient showed positive criteria of ICBs with compulsive shopping and binge eating. ICBs were associated with higher DA dose (p = 0.001), younger RLS onset (p = 0.04), history of experimental drug use (p = 0.002), female gender (p = 0.04) and a family history of gambling disorders (p = 0.02), which accounted for 52% of the risk variance.
RLS patients treated with dopaminergic agents and dopamine agonists in particular, should be forewarned of potential side effects. A careful history of risk factors should be taken.
Restless legs syndrome; impulse control disorders; dopamine agonist; gambling; levodopa
Impulsivity is a core feature in bipolar disorder. Although mood symptoms exacerbate impulsivity, self-reports of impulsivity are elevated even during euthymia. Neurocognitive processes linked to impulsivity (e.g., attention, inhibition) are also impaired in patients with bipolar disorder and a high frequency of comorbidities associated with impulsivity, such as substance use disorders, further highlight the clinical relevance of this dimension of the illness. Our objective was to assess the relationship between impulsivity and cognition in bipolar disorder.
We evaluated impulsivity in 98 patients with bipolar disorder and its relationship with symptoms, cognition, and substance use history. We assessed self reports of trait-impulsivity [Barrett Impulsiveness Scale (BIS)] and impulsive behaviors on the Iowa Gambling Task (IGT). A comprehensive clinical and neurocognitive battery was also completed. Patients were compared with 95 healthy controls.
Patients with bipolar disorder had higher scores versus healthy controls on all BIS scales. Performance on the IGT was significantly impaired and patients showed a tendency toward more erratic choices. Depressive symptoms were positively correlated with trait-impulsivity and with an increased tendency to attend more readily to losses versus gains on the IGT. We found no significant associations between impulsivity and neurocognition in the full bipolar sample; however, when sub-grouped based on substance abuse history, significant relationships were revealed only in subjects without a substance abuse history.
Our data support prior reports of increased trait-impulsivity and impairment on behavioral tasks of impulsiveness in bipolar disorder and suggest a differential relationship between these illness features that is dependent upon history of substance abuse.
decision making; depression; impulsivity; Iowa Gambling Task; substance use
The suppression of spontaneous motor impulses is an essential facet of cognitive control that is linked to frontal-basal ganglia circuitry. Basal ganglia dysfunction caused by Parkinson’s disease (PD) disrupts the proficiency of action suppression, but how pharmacotherapy for PD impacts impulsive motor control is poorly understood. Dopamine agonists improve motor symptoms of PD, but can also provoke impulsive-compulsive behaviors (ICB). We investigated whether dopamine agonist medication has a beneficial or detrimental effect on impulsive action control in thirty-eight PD patients, half of whom had current ICB. Participants performed the Simon conflict task, which measures susceptibility to acting on spontaneous action impulses as well as the proficiency of suppressing these impulses. Compared to an off agonist state, patients on their agonist were no more susceptible to reacting impulsively, but were less proficient at suppressing the interference from the activation of impulsive actions. Importantly, agonist effects depended on baseline performance in the off agonist state; more proficient suppressors off agonist experienced a reduction in suppression on agonist, whereas less proficient suppressors off agonist showed improved suppression on agonist. Patients with active ICB were actually less susceptible to making fast, impulsive response errors than patients without ICB, suggesting that behavioral problems in this subset of patients may be less related to impulsivity in motor control. Our findings provide further evidence that dopamine agonist medication impacts specific cognitive control processes and that the direction of its effects depends on individual differences in performance off medication.
Parkinson’s disease; simon task; inhibition; dopamine agonist; impulse control
Impulse control disorders (ICD) in Parkinson’s disease (PD) are a disabling non-motor symptom with frequencies of 13–35% among patients receiving dopamine replacement therapy. ICD in PD is strongly associated with dopaminergic drug use, especially non-ergot dopamine agonists (DA). However, individual susceptibility and disease-related neural changes are also important contributors to the development of ICD. Discrepancies between nigrostriatal and mesolimbic dopaminergic degeneration and non-physiological administration of dopaminergic drugs may induce abnormal ’hyperstimulation’ of the mesolimbic system, which alters reward-learning behaviors in PD patients. In addition, DA can make patients more impulsive during decision-making and seek risk-taking behaviors. DA intake is also related to the biased representation of rewards. Ultimately, loss of negative feedback control due to dysfunctional frontostriatal connections is necessary for the establishment of ICD in PD. The subsequent behavioral and neural changes are affected by PD treatment and disease progression; thus, proper treatment guidelines for physicians are needed to prevent the development of ICD. Future studies aimed at producing novel therapeutics to control the risk factors for ICD or treat ICD behaviors in PD are warranted. This review summarizes recent advances from epidemiological and pathophysiological studies on ICD in PD. Management principles and limitations of current therapeutics are briefly discussed.
Impulse control disorder; Parkinson’s disease; Dopamine agonist; Reward-learning; Impulsivity; Addiction
The dopamine agonist pramipexole (PPX) can increase impulsiveness, and PPX therapy for neurological diseases (Parkinson's disease (PD) and restless leg syndrome) is associated with impulse control disorders (ICDs) in subpopulations of treated patients. A commonly reported ICD is pathological gambling of which risk taking is a prominent feature. Probability discounting is a measurable aspect of risk taking. We recently developed a probability discounting paradigm wherein intracranial self-stimulation (ICSS) serves as the positive reinforcer. Here we used this paradigm to determine the effects of PPX on discounting. We included assessments of a rodent model of PD, wherein 6-OHDA was injected into the dorsolateral striatum of both hemispheres, which produced persistent PD-like deficits in posture adjustment. Rats were trained to perform ICSS-mediated probability discounting, in which PD-like and control groups exhibited similar profiles. Rats were treated twice daily for 2 weeks with 2 mg/kg (±)PPX (ie, 1 mg/kg of the active form), a dose that improved lesion-induced motor deficits. In both groups, (±)PPX increased discounting; preference for the large reinforcer was enhanced 30–45% at the most uncertain probabilities. Tolerance did not develop with repeated treatments. Increased discounting subsided within 2 weeks of (±)PPX cessation, and re-exposure to (±)PPX reinstated heightened discounting. Such findings emulate the clinical scenario; therefore, ICSS for discounting assessments in rats exhibited high face validity. This model should prove useful in medication development where assessment of the propensity of a putative therapy to induce risk-taking behaviors is of interest.
pramipexole; probability discounting; 6-OHDA; gambling; rat; reward; animal models; dopamine; addiction & substance abuse; movement disorders; pramipexole; probability discounting; 6-OHDA; gambling; rat
Links between impulsive compulsive behaviors in treated Parkinson’s disease, behavioral addictions and substance abuse have been postulated, but no direct comparisons have been carried out so far.
We directly compared patients with Parkinson’s disease with and without impulsive compulsive behaviors with illicit drug abusers, pathological gamblers and age-matched healthy controls using the beads task, a test of reflection impulsivity and a working memory task.
We found that all patients with Parkinson’s disease made more impulsive and irrational choices than the control group. Parkinson’s disease patients who had an impulsive compulsive behavior showed similar behavior to illicit substance abusers whereas patients without impulsive compulsive behaviors more closely resembled pathological gamblers. In contrast we found no difference in working memory performance within the Parkinson’s disease groups. However Parkinson’s disease patients without impulsive compulsive behaviors remembered distractors significantly less than all other patients during working memory tests.
We were able to correctly classify 96% of the Parkinson’s disease patients with respect to whether or not they had an impulsive compulsive behavior by analyzing 3 trials of the 80/20 loss condition of the beads task with a negative prediction value of 92.3% and we propose that this task may prove to be a powerful screening tool to detect an impulsive compulsive behavior in Parkinson’s disease. Our results also suggest that intact cortical processing and less distractibility in Parkinson’s disease patients without impulsive compulsive behaviors may protect them from developing behavioral addictions.
Impulsive compulsive behavior; Parkinson’s disease; reflection impulsivity; pathological gambling; substance abuse; beads task