Controlled study of decision‐making and cognitive impairment in Parkinson's disease

Decision-making under ambiguity and risk and executive functions in Parkinson's disease patients: A scoping review of the studies investigating the Iowa Gambling Task and the Game of Dice

Evidence shows that patients affected by Parkinson's disease (PD) display the tendency toward making risky choices. This is due, at least in part, to the pathophysiological characteristics of the disease that affects neural areas underlying decision making (DM), in which a pivotal role is played by nonmotor corticostriatal circuits and dopamine. Executive functions (EFs), which can be impaired by PD as well, may sustain optimal choices in DM processes. However, few studies have investigated whether EFs can support PD patients to make good decisions. Adopting the scoping review approach, the present article is designed to deepen the cognitive mechanisms of DM under conditions of ambiguity and risk (that are conditions common to everyday life decisions) in PD patients without impulse control disorders. We focused our attention on the Iowa Gambling Task and the Game of Dice Task, because they are the most commonly used and reliable tasks to assess DM under ambiguity and under risk, respectively, and analyzed the performances in such tasks and their relationships with EFs tests in PD patients. The analysis supported the relationships between EFs and DM performance, especially when a higher cognitive load is required to make optimal decisions, as it happens under conditions of risk. Possible knowledge gaps and further research directions are suggested to better understand DM mechanisms in PD sustaining patients' cognitive functioning and preventing negative consequences in everyday life derived from suboptimal decisions.

Contribution of the sensorimotor beta oscillations and the cortico-basal ganglia-thalamic circuitry during value-based decision making: A simultaneous EEG-fMRI investigation

In decision neuroscience, the motor system has primarily been considered to be involved in executing choice actions. However, a competing perspective suggests its engagement in the evaluation of options, traditionally considered to be performed by the brain's valuation system. Here, we investigate the role of the motor system in value-based decision making by determining the neural circuitries associated with the sensorimotor beta oscillations previously identified to encode decision options. In a simultaneous EEG-fMRI study, participants evaluated reward and risk associated with a forthcoming action. A significant sensorimotor beta desynchronization was identified prior to and independent of response. The level of beta desynchronization showed evidence of encoding the reward levels. This beta desynchronization covaried, on a trial-by-trial level, with BOLD activity in the cortico-basal ganglia-thalamic circuitry. In contrast, there was only a weak covariation within the valuation network, despite significant modulation of its BOLD activity by reward levels. These results suggest that the way in which decision variables are processed differs in the valuation network and in the cortico-basal ganglia-thalamic circuitry. We propose that sensorimotor beta oscillations indicate incentive motivational drive towards a choice action computed from the decision variables even prior to making a response, and it arises from the cortico-basal ganglia-thalamic circuitry.

Decision making in Parkinson's disease: An analysis of the studies using the Iowa Gambling Task

In Parkinson's disease (PD) impairments in decision making can occur, in particular because of the tendency toward risky and rewarding options. The Iowa Gambling Task has been widely used to investigate decision processes involving these options. The task assesses the ability to manage risk and to learn from feedback. The present paper aims at critically examining those studies in which this task has been administered to PD patients, in order to understand possible anomalies in patients' decision processes and which variables are responsible for that. A meta‐analysis has been conducted as well. Features of the task, sociodemographic and clinical aspects (including daily drugs intake), cognitive conditions and emotional disorders of the patients have been taken into account. Neural correlates of decision‐making competences were considered. It emerged that PD patients show a trend of preference toward risky choices, probably due to an impairment in anticipating the unrewarding consequences or to an insensitiveness to punishment. The possible role played by dopamine medications in decision making under uncertain conditions, affecting basal ganglia and structures involved in the limbic loop, was discussed. Attention has been focused on some aspects that need to be investigated in further research, in order to delve into this issue and promote patients' quality of life.

Is there a Neurobiological Rationale for the Utility of the Iowa Gambling Task in Parkinson's Disease?

Up to 23% of newly diagnosed, non-demented, Parkinson’s disease (PD) patients experience deficits in executive functioning (EF). In fact, EF deficits may occur up to 39-months prior to the onset of motor decline. Optimal EF requires working memory, attention, cognitive flexibility, and response inhibition underlying appropriate decision-making. The capacity for making strategic decisions requires inhibiting imprudent decisions and are associated with noradrenergic and dopaminergic signaling in prefrontal and orbitofrontal cortex. Catecholaminergic dysfunction and the loss of noradrenergic and dopaminergic cell bodies early in PD progression in the aforementioned cortical areas likely contribute to EF deficits resulting in non-strategic decision-making. Thus, detecting these deficits early in the disease process could help identify a significant portion of individuals with PD pathology (14–60%) before frank motor impairment. A task to evaluate EF in the domain of non-strategic decision-making might be useful to indicate the moderate loss of catecholamines that occurs early in PD pathology prior to motor decline and cognitive impairment. In this review, we focus on the potential utility of the Iowa Gambling Task (IGT) for this purpose, given significant overlap between in loss of dopaminergic and noradrenergic cells bodies in early PD and the deficits in catecholamine function associated with decreased EF. As such, given the loss of catecholamines already well-underway after PD diagnosis, we evaluate the potential utility of the IGT to identify the risk of therapeutic non-compliance and a potential companion approach to detect PD in premotor stages.

The Impact of Compulsivity and Impulsivity in Cerebellar Ataxia: A Case Series

Background:

The cerebellum has recently been identified to have a key role in reward processing, and individuals with ataxia have been found to be more impulsive and compulsive as part of cerebellum-related cognitive and behavioral disturbances.

Case Report:

We reported five individuals with cerebellar ataxia who demonstrate impulsive and compulsive behaviors, including hobbyism, gambling, and compulsive medication use, to illustrate that these symptoms can be highly disabling.

Discussion:

These five cases provide examples of behavioral symptoms in cerebellar ataxia. Further investigations of the pathomechanism of these symptoms will advance our understanding of the cerebellum in cognition and behavior.

Dopaminergic influences on risk preferences of Parkinson's disease patients

Clinicians are increasingly recognizing impulse control disorders (ICDs) as a complication of dopaminergic treatment in Parkinson's disease (PD). Considering the pivotal role of dopamine in reward information processing, ICDs may originate from dysregulation of reward-oriented behavior, and the behavioral changes may be reflected in shifts of psychological risk preference during decision-making. We used a behavioral economics paradigm to evaluate quantitatively the risk preferences of PD patients in levodopa on and off states. We also examined age-matched healthy controls. We found that levodopa increased the subjective value and prolonged the decision time in PD patients. These effects are apparently not explained by kinematic improvements but are attributed to psychological shifts of risk preferences and increased attention during risky decision-making. The risk preferences of healthy controls were similar to those of PD on levodopa treatment. The risk preferences of PD patients were not correlated with the scores of routine cognitive batteries, suggesting that dopamine-sensitive risk preferences are independent of cognitive capacities as measured by conventional batteries, including general intelligence, memory, and frontal functioning. By contrast, apathy and ICD partially predicted the risk attitude in PD patients, suggesting a common background of limbic origin behind these properties. The present results demonstrated that dopamine deficiency in off-state PD leads to risk-avoiding behavior and levodopa treatment increases the risk preferences. Behavioral economics framework is useful to evaluate short-term psychological changes in response to levodopa in PD patients.

Behavioral and Neuroanatomical Account of Impulsivity in Parkinson's Disease

Impulse control disorder (ICD) is a major non-motor complication of Parkinson's disease (PD) with often devastating consequences for patients' quality of life. In this study, we aimed to characterize the phenotype of impulsivity in PD and its neuroanatomical correlates.

Methods: Thirty-seven PD patients (15 patients with ICD, 22 patients without ICD) and 36 healthy controls underwent a neuropsychological battery. The test battery consisted of anxiety and depression scales, self-report measures of impulsivity (Barratt scale and UPPS-P), behavioral measures of impulsive action (Go/No-Go task, Stop signal task) and impulsive choice (Delay discounting, Iowa gambling task), and measures of cognitive abilities (working memory, attention, executive function). Patients and controls underwent structural MRI scanning.

Results: Patients with ICD had significantly higher levels of self-reported impulsivity (Barratt scale and Lack of perseverance from UPPS-P) in comparison with healthy controls and non-impulsive PD patients, but they performed similarly in behavioral tasks, except for the Iowa gambling task. In this task, patients with ICD made significantly less risky decisions than patients without ICD and healthy controls. Patients without ICD did not differ from healthy controls in self-reported impulsivity or behavioral measurements. Both patient groups were more anxious and depressive than healthy controls. MRI scanning revealed structural differences in cortical areas related to impulse control in both patient groups. Patients without ICD had lower volumes and cortical thickness of bilateral inferior frontal gyrus. Patients with ICD had higher volumes of right caudal anterior cingulate and rostral middle frontal cortex.

Conclusions: Despite the presence of ICD as confirmed by both clinical follow-up and self-reported impulsivity scales and supported by structural differences in various neural nodes related to inhibitory control and reward processing, patients with ICD performed no worse than healthy controls in various behavioral tasks previously hypothesized as robust impulsivity measures. These results call for caution against impetuous interpretation of behavioral tests, since various factors may and will influence the ultimate outcomes, be it the lack of sensitivity in specific, limited ICD subtypes, excessive caution of ICD patients during testing due to previous negative experience rendering simplistic tasks insufficient, or other, as of now unknown aspects, calling for further research.

Functional inhibitory control dynamics in impulse control disorders in Parkinson's disease

BACKGROUND

Impulse control disorders related to alterations in the mesocorticolimbic dopamine network occur in Parkinson's disease (PD). Our objective was to investigate the functional neural substrates of reward processing and inhibitory control in these patients.

METHODS

Eighteen PD patients with impulse control disorders, 17 without this complication, and 18 healthy controls performed a version of the Iowa Gambling Task during functional magnetic resonance scanning under 3 conditions: positive, negative, and mixed feedback. Whole-brain contrasts, regions of interest, time courses, functional connectivity analyses, and brain-behavior associations were examined.

RESULTS

PD patients with impulse control disorders exhibited hyperactivation in subcortical and cortical regions typically associated with reward processing and inhibitory control compared with their PD and healthy control counterparts. Time-course analyses revealed that only PD patients with impulse control disorders exhibited stronger signal intensity during the initial versus final periods of the negative-feedback condition in bilateral insula, and right ventral striatum. Interestingly, hyperactivation of all the examined right-lateralized frontostriatal areas during negative feedback was positively associated with impulse control disorder severity. Importantly, positive associations between impulse control disorder severity and regional activations in the right insula and right inferior frontal gyrus, but not the right subthalamic nucleus, were mediated by functional connectivity with the right ventral striatum.

CONCLUSIONS

During a reward-based task, PD patients with impulse control disorders showed hyperactivation in a right-lateralized network of regions including the subthalamic nucleus that was strongly associated with impulse control disorder severity. In these patients, the right ventral striatum in particular played a critical role in modulating the functional dynamics of right-lateralized inhibitory-control frontal regions when facing penalties. © 2019 International Parkinson and Movement Disorder Society.

Pathological Gambling in Parkinson's disease: Autonomic measures supporting impaired decision-making

According to the somatic marker hypothesis, autonomic measures and arousal modulation can reveal a difference in subgroups of patients developing impaired decision-making because of addictions. Previously, pathological gambling (PG) and Parkinson's disease (PD) have been associated with differential arousal levels during gambling behavior. However, no research considered the specific autonomic responses of Parkinson's disease patients with pathological gambling and with a previous history of gambling. Thus, this study investigated skin conductance responses (SCRs), skin conductance level (SCL) and heart rate (HR) during the Iowa Gambling Task (IGT) in two groups of PD patients with gambling disorder, active (PD Gamblers; n = 14) or remitted (PD Non-Gamblers; n = 13) and a control group of patients with Parkinson's disease only (n = 13). Anticipatory autonomic responses to disadvantageous decks and advantageous decks during the Iowa Gambling Task were measured for each participant. The PD Gamblers group performed worse than the PD Non-Gamblers and the control groups at the IGT task and exhibited lower SCRs, SCL, and HR during the decision-making processing of cards belonging to disadvantageous decks. The role of autonomic and behavioral measures was considered.

Personality Traits and Cortical Activity Affect Gambling Behavior in Parkinson's Disease

BACKGROUND

Pathological gambling (PG) in Parkinson's disease (PD) manifests as a persistent and uncontrollable gambling behavior, characterized by dysfunctional decision-making and emotional impairment related to high-risk decisions.

OBJECTIVE

The aim of this study was to explore the relationship between personality traits and prefrontal cortex activity in PD patients with or without PG.

METHODS

Thus, hemodynamic cortical activity measured by functional near-infrared spectroscopy (fNIRS) and Iowa Gambling Task (IGT) performance were recorded in forty-six PD patients, divided into three groups according to their gambling status: PD patients with active gambling behavior (PDG); PD patients who remitted from PG (PDNG); and a control group (CG) composed by patients with PD only.

RESULTS

Results indicates that gambling behavior in PD patients is strongly predictive of dysfunctional cognitive strategy; affecting anomalous cortical response with a left hemispheric unbalance in dorsal areas; and it is related to more reward sensitivity than impulsivity personality components.

CONCLUSIONS

PDG patients differed from PDNG and CG from both behavioral and brain response to decision-making. Overall, these effects confirm a pathological condition related to cognitive and emotional aspects which makes the patients with PGD victims of their dysfunctional behavior.

Biased numerical cognition impairs economic decision-making in Parkinson's disease

Objective

Previous findings suggest a context‐dependent bihemispheric allocation of numerical magnitude. Accordingly, we predicted that lateralized motor symptoms in Parkinson's disease (PD), which reflect hemispheric asymmetries, would induce systematic lateralized biases in numerical cognition and have a subsequent influence on decision‐making.

Methods

In 20 PD patients and matched healthy controls we assessed numerical cognition using a number‐pair bisection and random number generation task. Decision‐making was assessed using both the dictator game and a validated questionnaire.

Results

PD patients with predominant right‐sided motor symptoms exhibited pathological biases toward smaller numerical magnitudes and formulated less favorable prosocial choices during a neuroeconomics task (i.e., dictator game). Conversely, patients with left‐sided motor symptoms exhibited pathological biases toward larger numerical magnitudes and formulated more generous prosocial choices. Our account of context‐dependent hemispheric allocation of numerical magnitude in PD was corroborated by applying our data to a pre‐existing computational model and observing significant concordance. Notably, both numerical biasing and impaired decision‐making were correlated with motor asymmetry.

Interpretation

Accordingly, motor asymmetry and functional impairment of cognitive processes in PD can be functionally intertwined. To conclude, our findings demonstrate context‐dependent hemispheric allocation and encoding of numerical magnitude in PD and how biases in numerical magnitude allocation in Parkinsonian patients can correspondingly impair economic decision‐making.

Meta-Analytic Evidence for a Reversal Learning Effect on the Iowa Gambling Task in Older Adults

Iowa Gambling Task (IGT) is one of the most widely used tools to assess economic decision-making. However, the research tradition on aging and the Iowa Gambling Task (IGT) has been mainly focused on the overall performance of older adults in relation to younger or clinical groups, remaining unclear whether older adults are capable of learning along the task. We conducted a meta-analysis to examine older adults' decision-making on the IGT, to test the effects of aging on reversal learning (45 studies) and to provide normative data on total and block net scores (55 studies). From the accumulated empirical evidence, we found an average total net score of 7.55 (±25.9). We also observed a significant reversal learning effect along the blocks of the IGT, indicating that older adults inhibit the prepotent response toward immediately attractive options associated with high losses, in favor of initially less attractive options associated with long-run profit. During block 1, decisions of older adults led to a negative gambling net score, reflecting the expected initial pattern of risk-taking. However, the shift toward more safe options occurred between block 2 (small-to-medium effect size) and blocks 3, 4, 5 (medium-to-large effect size). These main findings highlight that older adults are able to move from the initial uncertainty, when the possible outcomes are unknown, to decisions based on risk, when the outcomes are learned and may be used to guide future adaptive decision-making.

Effects of deep brain stimulation of the subthalamic nucleus on perceptual decision making

When faced with difficult decisions, people prefer to stay with the default. This status quo bias often leads to suboptimal choice behavior. Neurophysiological evidence suggests a pivot role of the Subthalamic Nucleus (STN) for overcoming such status quo bias in difficult decisions, but causal evidence is lacking. The present study investigated whether subthalamic deep brain stimulation (DBS) in patients with Parkinson's disease (PD) influences the status quo bias. Eighteen PD patients treated with STN-DBS performed a difficult perceptual decision task incorporating intrinsic status quo option. Patients were tested with (ON) and without (OFF) active STN stimulation. Our results show that DBS of the STN affected perceptual decision making in PD patients depending on the difficulty of decision. STN-DBS improved difficult perceptual decisions due to a selective increase in accuracy (hit rate) that was independent of response bias (no effect on false alarm rate). Furthermore, STN-DBS impacted status quo bias as a function of baseline impulsivity. In impulsive patients, STN-DBS increased the default bias, whereas in less impulsive PD patients, DBS of the STN reduced the status quo bias. In line with our hypothesis, STN-DBS selectively affected the tendency to stick with the default option on difficult decisions, and promoted increased decision accuracy. Moreover, we demonstrate the impact of baseline cognitive abilities on DBS-related performance changes in PD patients.

Decision-making performance in Parkinson's disease correlates with lateral orbitofrontal volume

BACKGROUND

Patients with Parkinson's disease (PD) exhibit poor decision-making, and the underlying neural correlates are unclear. We used voxel-based morphometry with Diffeomorphic Anatomical Registration through Exponentiated Lie algebra to examine this issue.

METHODS

The decision-making abilities of 20 patients with PD and 37 healthy controls (HCs) were measured with a computerized Iowa Gambling Task (IGT). We assessed the local gray matter volumes of the patients and HCs and their correlations with decision-making performance, disease duration, disease severity, and anti-Parkinsonism medication dose.

RESULTS

Compared with the HCs, the patients with PD exhibited poor IGT performances. The gray matter volumes in the medial orbitofrontal cortex, left inferior temporal cortex, and right middle frontal gyrus were decreased in the patients. Results in the regression analysis showed that lateral orbitofrontal volume correlated with performance in the IGT in PD. Regions that correlated with disease duration, severity, and medication dose did not overlap with orbitofrontal regions.

CONCLUSION

Our results indicate that the lateral and medial orbitofrontal cortex are related to decision-making in PD patients. Since the medial orbitofrontal cortex is shown to be involved in monitoring reward, reward monitoring seems to be impaired as a whole in PD patients. Meanwhile, the lateral region is related to evaluation of punishment, which is considered to have an influence on individual differences in decision-making performance in PD patients.

Deep Brain Stimulation: In Search of Reliable Instruments for Assessing Complex Personality-Related Changes

During the last 25 years, more than 100,000 patients have been treated with Deep Brain Stimulation (DBS). While human clinical and animal preclinical research has shed light on the complex brain-signaling disturbances that underpin e.g., Parkinson's disease (PD), less information is available when it comes to complex psychosocial changes following DBS interventions. In this contribution, we propose to more thoroughly investigate complex personality-related changes following deep brain stimulation through refined and reliable instruments in order to help patients and their relatives in the post-surgery phase. By pursuing this goal, we first outline the clinical importance DBS has attained followed by discussing problematic and undesired non-motor problems that accompany some DBS interventions. After providing a brief definition of complex changes, we move on by outlining the measurement problem complex changes relating to non-motor symptoms currently are associated with. The latter circumstance substantiates the need for refined instruments that are able to validly assess personality-related changes. After providing a brief paragraph with regard to conceptions of personality, we argue that the latter is significantly influenced by certain competencies which themselves currently play only a tangential role in the clinical DBS-discourse. Increasing awareness of the latter circumstance is crucial in the context of DBS because it could illuminate a link between competencies and the emergence of personality-related changes, such as new-onset impulse control disorders that have relevance for patients and their relatives. Finally, we elaborate on the field of application of instruments that are able to measure personality-related changes.

The impact of Parkinson's disease and subthalamic deep brain stimulation on reward processing

BACKGROUND

Due to its position in cortico-subthalamic and cortico-striatal pathways, the subthalamic nucleus (STN) is considered to play a crucial role not only in motor, but also in cognitive and motivational functions. In the present study we aimed to characterize how different aspects of reward processing are affected by disease and deep brain stimulation of the STN (DBS-STN) in patients with idiopathic Parkinson's disease (PD).

METHODS

We compared 33 PD patients treated with DBS-STN under best medical treatment (DBS-on, medication-on) to 33 PD patients without DBS, but optimized pharmacological treatment and 34 age-matched healthy controls. We then investigated DBS-STN effects using a postoperative stimulation-on/ -off design. The task set included a delay discounting task, a task to assess changes in incentive salience attribution, and the Iowa Gambling Task.

RESULTS

The presence of PD was associated with increased incentive salience attribution and devaluation of delayed rewards. Acute DBS-STN increased risky choices in the Iowa Gambling Task under DBS-on condition, but did not further affect incentive salience attribution or the evaluation of delayed rewards.

CONCLUSION

Findings indicate that acute DBS-STN affects specific aspects of reward processing, including the weighting of gains and losses, while larger-scale effects of disease or medication are predominant in others reward-related functions.

Decision-making impairments in Parkinson's disease as a by-product of defective cost-benefit analysis and feedback processing

Studies examining decision-making in people with Parkinson's disease (PD) show impaired performance on a variety of tasks. However, there are also demonstrations that patients with PD can make optimal decisions just like healthy age-matched controls. We propose that the reason for these mixed findings is that PD does not produce a generalized impairment of decision-making, but rather affects sub-components of this process. In this review we evaluate this hypothesis by considering the empirical evidence examining decision-making in PD. We suggest that of the various stages of the decision-making process, the most affected in PD are (1) the cost-benefit analysis stage and (2) the outcome evaluation stage. We consider the implications of this proposal for research in this area.

Long-term cognitive follow-up of Parkinson's disease patients with impulse control disorders

This study investigated cognitive functions in Parkinson's disease (PD) patients with impulse control disorders (ICDs) and aimed to identify possible predictors of behavioral outcome. In this longitudinal cohort study, 40 PD outpatients with ICDs and 40 without, were matched for sex, age at PD onset, age and disease duration at cognitive assessment. All patients had two neuropsychological assessments at least 2 years apart (mean, 3.5 years). Multivariate logistic regression analysis was performed to identify predictors of ICDs remission at follow-up. The PD patients with and without ICDs had overall comparable cognitive performance at baseline. When evaluating changes between baseline and follow-up, we found significant group × time interactions in several frontal lobe-related tests, with the ICDs group showing a less pronounced worsening over time. ICDs remission was associated with better performance at baseline in working memory-related tasks, such as digit span (odds ratio [OR] = 2.69 [95% confidence interval (CI), 1.09-6.66]) and attentive matrices (OR=1.19 [95%CI, 1.03-1.37]). ICDs remitters and non-remitters had no remarkable differences in baseline PD-related features and therapy management strategies (including the extent of dopamine agonist dose reduction). In conclusion, ICDs in PD patients are not related to greater cognitive impairment or executive dysfunction, but rather show relatively lower cognitive decline over time. The impaired top-down inhibitory control characterizing ICDs is likely attributable to a drug-induced overstimulation of relatively preserved prefrontal cognitive functions. Full behavioral remission in the long term was predicted by better working memory abilities. © 2015 International Parkinson and Movement Disorder Society.

Iowa gambling task impairment in Parkinson's disease can be normalised by reduction of dopaminergic medication after subthalamic stimulation

BACKGROUND

Impulse control disorders (ICD), including pathological gambling, are common in Parkinson's disease (PD) and tend to improve after subthalamic (STN) stimulation after a marked reduction of dopaminergic medication. In order to investigate the effect of STN stimulation on impulsive decision making, we used the Iowa Gambling task (IGT).

METHODS

We investigated IGT performance in 20 patients with PD before STN surgery with and without dopaminergic treatment and in 24 age-matched controls. All patients underwent an extensive neuropsychological interview screening for behavioural disorders. Assessment in patients was repeated 3 months after surgery without dopaminergic treatment with and without stimulation.

RESULTS

Chronic antiparkinsonian treatment was drastically reduced after surgery (-74%). At baseline, on high chronic dopaminergic treatment 8/20 patients with PD presented with pathological hyperdopaminergic behaviours, which had resolved in 7/8 patients 3 months after surgery on low chronic dopaminergic treatment. Preoperative performance on the IGT was significantly impaired compared to after surgery.

CONCLUSIONS

Dopaminergic medication likely contributes to the impairment in decision making underlying ICDs. Deep brain stimulation allows drastic reduction of dopaminergic medication and, thus, concomitant remediation of medication-induced impairment in decision making.

Reward processing in neurodegenerative disease

Representation of reward value involves a distributed network including cortical and subcortical structures. Because neurodegenerative illnesses target specific anatomic networks that partially overlap with the reward circuit, they would be predicted to have distinct impairments in reward processing. This review presents the existing evidence of reward processing changes in neurodegenerative diseases including mild cognitive impairment (MCI), Alzheimer's disease, frontotemporal dementia, amyotrophic lateral sclerosis (ALS), Parkinson's disease, and Huntington's disease, as well as in healthy aging. Carefully distinguishing the different aspects of reward processing (primary rewards, secondary rewards, reward-based learning, and reward-based decision-making) and using tasks that differentiate the stages of processing reward will lead to improved understanding of this fundamental process and clarify a contributing cause of behavioral change in these illnesses.

Betting on DBS: Effects of subthalamic nucleus deep brain stimulation on risk taking and decision making in patients with Parkinson's disease

OBJECTIVE

Concerns persist that deep brain stimulation (DBS) for Parkinson's disease (PD) increases impulsivity or induces excessive reward seeking. We report here the performance of PD patients with implanted subthalamic nucleus electrodes, with stimulation on and off, on 3 laboratory tasks of risk taking and decision making. They are compared with PD patients maintained on medication and healthy participants.

METHODS AND RESULTS

In the Game of Dice Task, a test of "risky" decision making, PD patients with or without DBS made highest risk bets more often and ended up with less money than did healthy participants. There was a trend for DBS stimulation to ameliorate this effect. Deal or No-Deal is an "ambiguous" decision-making task that assessed preference for risk (holding on to one's briefcase) over a "sure thing" (accepting the banker's offer). Here, DBS patients were more conservative with stimulation on than with it off. They accepted smaller offers from the banker and won less money in the DBS-on condition. Overall, the 2 PD groups won less money than did healthy participants. The Framing Paradigm assessed willingness to gamble on a fixed (unambiguous) prize depending on whether the reward was "framed" as a loss or a gain. Nonsurgical PD patients tended to be more risk-averse than were healthy participants, whereas DBS patients were more willing to gamble for gains as well as losses both on and off stimulation.

CONCLUSIONS

On risky decision-making tasks, DBS patients took more risks than did healthy participants, but stimulation may temper this tendency. In contrast, in an ambiguous-risk situation, DBS patients were more risk-averse (conservative) than were healthy participants, and this tendency was greatest with stimulation.

Executive dysfunction in Parkinson's disease: a review

Executive dysfunction can be present from the early stages of Parkinson's disease (PD). It is characterized by deficits in internal control of attention, set shifting, planning, inhibitory control, dual task performance, and on a range of decision-making and social cognition tasks. Treatment with dopaminergic medication has variable effects on executive deficits, improving some, leaving some unchanged, and worsening others. In this review, we start by defining the specific nature of executive dysfunction in PD and describe suitable neuropsychological tests. We then discuss how executive deficits relate to pathology in specific territories of the basal ganglia, consider the impact of dopaminergic treatment on executive function (EF) in this context, and review the changes in EFs with disease progression. In later sections, we summarize correlates of executive dysfunction in PD with motor performance (e.g., postural instability, freezing of gait) and a variety of psychiatric (e.g., depression, apathy) and other clinical symptoms, and finally discuss the implications of these for the patients' daily life.

Decision and dopaminergic system: an ERPs study of Iowa gambling task in Parkinson's disease

Recent researches reported behavioral and emotional impairment in Parkinson's disease (PD), even in the earliest stages. This impairment affects also decision-making and learning processes. The Iowa gambling task (IGT) is commonly used to examine the decision-making capacity. The purpose of the present study was to investigate the neural correlates of feedback evaluation in the decision-making process into a learning context, using IGT and event-related potentials (ERPs) in a group of non-demented medicated PD patients. Fifteen PD patients and 15 healthy controls were recruited for the study. PD patients were administrated a basic neuropsychological assessment oriented to exclude cognitive impairments. Both groups underwent the computerized IGT during electroencephalography (EEG) registration. To analyse ERPs, continuous EEG data were epoched within a time-window starting 1000 ms before and ending 1000 ms after feedback presentation and averaged separately for positive (i.e., win condition) and negative (i.e., loss condition) feedbacks. Behavioral data revealed a significant lower performance of PD patients (p < 0.05) compared with the controls. While controls demonstrated a correct feedback evaluation, PD patients did not show any learning, selecting more disadvantageous decks even in the last part of task. Furthermore, ERPs results revealed that controls showed a significant difference (p < 0.05) in ERPs morphology recorded after the win and the loss conditions, suggesting that positive and negative feedbacks were differently evaluated and processed. PD patients showed a different pattern: their ERPs morphology was the same for positive and negative feedback. Interestingly, our ERPs results suggest that in PD patients an incorrect evaluation of context-relevant outcomes could be the reason of a poor performance in decision-making tasks, and could explain cognitive and behavioral problems related to impulse control disorder.

Depression and impulse control disorders in Parkinson's disease: two sides of the same coin?

Depression and impulse control disorders (ICD) are two common neuropsychiatric features in Parkinson's disease (PD). Studies have revealed that both phenomena are associated with aberrations in ventral striatal dopamine signaling and concomitant dysfunction of the reward-related (limbic) cortico-striatal-thalamocortical (CSTC) circuit. Depression in PD seems associated with decreased activity in the limbic CSTC circuit, whereas ICD seem associated with increased limbic CSTC circuit activity, usually after commencing dopamine replacement therapy (DRT). Not all DRT using PD patients, however, develop symptoms of ICD, suggesting an additional underlying neurobiological susceptibility. Furthermore, the symptoms of depression and ICD frequently coincide even though they are related to seemingly contrasting limbic CSTC circuit activation states. The aim of this review is to provide an overview of the currently available literature on the neurobiology of PD-related depression and ICD and discusses possible susceptibility factors. Finally, we propose a neurobiological model that identifies ventral striatal dopaminergic denervation as a common underlying neurobiological substrate of depression and ICD and subsequent dysfunction of reward and motivation-related brain areas.

Subthalamic stimulation modulates self-estimation of patients with Parkinson's disease and induces risk-seeking behaviour

Patients with Parkinson's disease with deep brain stimulation in the subthalamic nucleus postoperatively often display higher impulsivity and therefore may experience difficulties in social interactions. Here, we examined social interactions of patients with Parkinson's disease with and without deep brain stimulation in the subthalamic nucleus in competitive situations. We hypothesized altered self-estimation and risk-seeking behaviour in this patient group induced by deep brain stimulation in the subthalamic nucleus. To test the hypothesis, an experimental setting was used in which participants performed a calculation task and chose their preferred compensation. Based on their actual calculation performance, more patients with Parkinson's disease with deep brain stimulation chose a competitive tournament compensation. Assuming rational behaviour, this self-selection pattern reflects increased risk tolerance. Since patients who performed in the lowest quartile chose the tournament option, the data suggest that deep brain stimulation in the subthalamic nucleus results in a loss of the correct reference frame against which patients with Parkinson's disease evaluate their performance. The stimulation-induced combination of overestimation of their own performance, increased risk-taking, and preference for competitive environments despite poor performance is likely to impact considerably on the patients' social and work life.

Dopaminergic and clinical correlates of pathological gambling in Parkinson's disease: a case report

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 [(11)C]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 [(11)C]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.

Impaired financial abilities in Parkinson's disease patients with mild cognitive impairment and dementia

PURPOSE

Financial capacity (FC) is an instrumental activity of daily living (IADL) critical to independent functioning and sensitive to cognitive impairment in dementia. Little is known about FC in cognitively impaired patients with Parkinson's disease (PD). The present study investigated FC in PD patients with prodromal and clinical dementia.

METHODS

Participants were 20 older controls and 35 PD patients who met consensus criteria for either mild cognitive impairment (PD-MCI, n = 18) or PD dementia (PDD, n = 17). FC was assessed using a standardized performance based measure consisting of 9 domain and two global scores (Financial Capacity Instrument; FCI) (1). FCI domain and global performance scores were compared across groups. Capacity impairment ratings (no impairment, mild/moderate impairment, severe impairment) were calculated for each PD patient's domain and global scores.

RESULTS

Relative to controls, PD-MCI patients were impaired on both FCI global scores and domains of basic monetary skills, financial concepts, and investment decision-making. Relative to both controls and PD-MCI patients, PDD patients were impaired on virtually all FCI variables. With respect to impairment ratings, greater than 50% of PD-MCI patients and greater than 90% of PDD patients were classified as either mild/moderate or severely impaired on the two FCI global scores.

CONCLUSIONS

Impairment of financial capacity is already present in PD-MCI and is advanced in PDD. Complex cognitively-mediated IADLs such as financial capacity appear to be impaired early in the course of PD dementia.

Impulsivity and apathy in Parkinson's disease

Impulse control disorders (ICDs) and apathy are recognized as two important neuropsychiatric syndromes associated with Parkinson's disease (PD), but as yet we understand very little about the cognitive mechanisms underlying them. Here, we review emerging findings, from both human and animal studies, that suggest that impulsivity and apathy are opposite extremes of a dopamine-dependent spectrum of motivated decision making. We first argue that there is strong support for a hypodopaminergic state in PD patients with apathy, as well as for an association between dopamine therapy and development of ICDs. However, there is little evidence for a clear dose-response relationship, and great heterogeneity of findings. We argue that dopaminergic state on its own is an insufficient explanation, and suggest instead that there is now substantial evidence that both apathy and impulsivity are in fact multi-dimensional syndromes, with separate, dissociable mechanisms underlying their 'surface' manifestations. Some of these mechanisms might be dopamine-dependent. According to this view, individuals diagnosed as impulsive or apathetic may have very different mechanisms underlying their clinical states. We propose that impulsivity and apathy can arise from dissociable deficits in option generation, option selection, action initiation or inhibition and learning. Review of the behavioural and neurobiological evidence leads us to a new conceptual framework that might help understand the variety of functional deficits seen in PD.

Dissecting the effects of disease and treatment on impulsivity in Parkinson's disease

Converging evidence, including observations in patients with Parkinson's disease (PD), suggests that dopamine plays a role in impulsivity. This multi-faceted construct includes considerations of both time and risk; determining how these more specific processes are affected by PD and dopaminergic treatment can inform neurobiological models. We examined the effects of PD and its treatment on temporal discounting and risky decision-making in a cohort of 23 mild-moderate PD patients and 20 healthy participants. Patients completed the Balloon Analogue Risk Task and a temporal discounting paradigm both on and off their usual dopamine replacement therapy. PD patients did not differ from controls in their initial risk-taking on the Balloon Analogue Risk Task, but took progressively more risks across trials when on medication. A subset of patients and controls was tested again, 1.5-3 years later, to explore the effects of disease progression. On follow-up, baseline risk-taking diminished in patients, but the tendency to take increasing risks across trials persisted. Neither disease progression nor its treatment affected the temporal discounting rate. These findings suggest a different neural basis for temporal discounting and risk-taking, and demonstrate that risk-taking can be further decomposed into initial and trial-by-trial effects, with dopamine affecting only the latter.

Impulse control disorders in Parkinson's disease: background and update on prevention and management

Given that impulse control disorders (ICDs) have been identified among a considerable minority of Parkinson's disease (PD) patients, these conditions have gained increased clinical and research attention in the past decade. Dopamine-replacement therapies, taken to ameliorate PD symptoms, have been associated with ICDs in PD. Unfortunately, there are relatively sparse empirical data regarding how best to address ICDs in PD patients. Conversely, progress has been made in understanding the clinical, neurobiological and cognitive correlates of ICDs in PD. Some of these findings may inform possible courses of action for care providers working with PD patients with ICDs. The literature on ICDs in non-PD populations may also be informative in this regard. The goals of the present article are to outline important clinical characteristics of ICDs in PD, briefly review relevant neurocognitive and neurobiological studies and discuss possible ways to prevent and manage ICDs in PD.

Cannabinoids and value-based decision making: implications for neurodegenerative disorders

In recent years, disturbances in cognitive function have been increasingly recognized as important symptomatic phenomena in neurodegenerative diseases, including Parkinson's Disease (PD). Value-based decision making in particular is an important executive cognitive function that is not only impaired in patients with PD, but also shares neural substrates with PD in basal ganglia structures and the dopamine system. Interestingly, the endogenous cannabinoid system modulates dopamine function and subsequently value-based decision making. This review will provide an overview of the interdisciplinary research that has influenced our understanding of value-based decision making and the role of dopamine, particularly in the context of reinforcement learning theories, as well as recent animal and human studies that demonstrate the modulatory role of activation of cannabinoid receptors by exogenous agonists or their naturally occurring ligands. The implications of this research for the symptomatology of and potential treatments for PD are also discussed.

An exploration of apathy and impulsivity in Parkinson disease

Background. Apathy and impulsivity in Parkinson disease (PD) are associated with clinically significant behavioral disorders. Aim. To explore the phenomenology, distribution, and clinical correlates of these two behaviors. Methods. In PD participants (n = 99) without dementia we explored the distribution of measures of motivation and impulsivity using univariate methods. We then undertook factor analysis to define specific underlying dimensions of apathy and impulsivity. Regression models were developed to determine the associated demographic and clinical features of the derived dimensions. Results. The factor analysis of apathy (AES-C) revealed a two-factor solution: “cognitive-behavior” and “social indifference”. The factor analysis of impulsivity (BIS-11) revealed a five-factor solution: “inattention”; “impetuosity”; “personal security”; “planning”; and “future orientation”. Apathy was significantly associated with: age, age of motor symptom onset (positive correlation), disease stage, motor symptom severity, and depression. Impulsivity was significantly associated with: age of motor symptom onset (negative correlation), gambling and anxiety scores, and motor complications. We observed an overlap of apathy and impulsivity in some participants. Conclusion. In PD, apathy and impulsivity have specific phenomenological profiles and are associated with particular clinical phenotypes. In spite of this, there is some overlap of behaviors which may suggests common aspects in the pathology underlying motivation and reward processes.

Decision making and executive functions in REM sleep behavior disorder

STUDY OBJECTIVES

This study was designed to assess decision making and executive functions in patients with idiopathic REM sleep behavior disorder (iRBD). IRBD is often seen as an early sign of later evolving neurodegenerative disease, most importantly Parkinson disease (PD) and Lewy body dementia (DLB). It has been proposed that iRBD patients show a cognitive profile similar to patients with PD.

DESIGN

All participants performed an extensive test battery tapping executive functions as well as the IOWA gambling task, which measures decision making under ambiguity.

SETTING

University hospital sleep disorders center.

PARTICIPANTS

16 iRBD patients and 45 age- and education-matched controls.

INTERVENTION

N.A.

MEASUREMENTS AND RESULTS

Compared with controls, iRBD patients showed disadvantageous decision making under ambiguity and did not learn by feedback over the task. IRBD patients' decision pattern was characterized by the lack of a consistent strategy, as indicated by frequent shifts between the single choices. A high proportion of iRBD patients (75%) showed random performance or worse even at the end of the task. No group differences were found in tasks assessing information sampling, flexibility and categorization, problem solving, and impulsivity.

CONCLUSIONS

As suggested by the present investigation, iRBD patients may show difficulties in decision making under ambiguity in a stage when other cognitive functions are relatively well preserved. Whether this is driven by subgroups of patients prone to develop PD or DLB has to be assessed by follow-up investigations.

Sensitivity and bias in decision-making under risk: evaluating the perception of reward, its probability and value

Background

There are few clinical tools that assess decision-making under risk. Tests that characterize sensitivity and bias in decisions between prospects varying in magnitude and probability of gain may provide insights in conditions with anomalous reward-related behaviour.

Objective

We designed a simple test of how subjects integrate information about the magnitude and the probability of reward, which can determine discriminative thresholds and choice bias in decisions under risk.

Design/Methods

Twenty subjects were required to choose between two explicitly described prospects, one with higher probability but lower magnitude of reward than the other, with the difference in expected value between the two prospects varying from 3 to 23%.

Results

Subjects showed a mean threshold sensitivity of 43% difference in expected value. Regarding choice bias, there was a ‘risk premium’ of 38%, indicating a tendency to choose higher probability over higher reward. An analysis using prospect theory showed that this risk premium is the predicted outcome of hypothesized non-linearities in the subjective perception of reward value and probability.

Conclusions

This simple test provides a robust measure of discriminative value thresholds and biases in decisions under risk. Prospect theory can also make predictions about decisions when subjective perception of reward or probability is anomalous, as may occur in populations with dopaminergic or striatal dysfunction, such as Parkinson's disease and schizophrenia.

Impaired decision-making in idiopathic REM sleep behavior disorder

BACKGROUND

Patients with REM sleep behavior disorder (RBD) frequently develop Parkinson's disease (PD), which can impair decision-making ability. This study was undertaken to investigate decision-making ability and its relation to olfactory function in patients with idiopathic RBD.

METHODS

This study used the Iowa Gambling Task (IGT) and the Sniffin' Stick Test for examination of 38 patients with idiopathic RBD (iRBD) and 34 age-matched healthy control subjects (HC). Associations between these test results and other clinical RBD variables were also assessed.

RESULTS

Total IGT score and Sniffin' Stick Test scores were significantly lower in the iRBD group than in the HC group. The iRBD group IGT scores in the first, third, and final blocks were significantly lower than those of the HC group. In the iRBD group, no association was found between the total IGT score and the Sniffin' Stick Test score or any clinical RBD variable.

CONCLUSIONS

Impaired decision-making associated with iRBD can herald PD. However, decision-making disability is thought to appear irrespective of olfactory dysfunction and progression of RBD pathology.

Selective IGT decision-making impairment in a patient with juvenile Parkinson's disease and pathological gambling: a role for dopaminergic therapy?

The orbitofrontal cortex and the dopaminergic system are structures involved in managing impulsivity and sensibility to reinforcements, and both are typically impaired in Parkinson's disease (PD). Also, l-DOPA treatment can contribute to the development of the 'Dopamine Dysregulation Syndrome', a syndrome that can influence the patients' personality and lead to risk-taking behaviors. In this study, we describe the case of a 42-year-old woman (LT) affected by juvenile PD, treated with both l-DOPA and dopamine agonists, who showed a sudden onset of pathological gambling (PG), as the only neuropsychiatric symptom. We assessed LT with a full neuropsychological battery and the Iowa Gambling Task (IGT), in order to describe her specific failure in decision making. LT's performance on the IGT is compared with that of 15 non-demented PD patients under therapy with dopamine agonists and no behavioral dysregulations and with that of 16 age- and education-matched healthy subjects. Results showed fully preserved memory, executive functions, and reasoning abilities for LT, but a remarkable and stable impairment in the IGT. Performance of LT on the IGT is significantly lower than that of both control groups. This case shows, for the first time, that high cognitive functioning and preserved executive functions are no guarantee for advantageous decision making, and that the onset of PG is consistent with selective orbitofrontal disruption and side-effects of dopamine agonist therapy. It is also showed that the IGT is a useful neuropsychological device to detect specific risk-taking behaviors, which compromise functioning in real life.

Similarities and differences between pathological gambling and substance use disorders: a focus on impulsivity and compulsivity

RATIONALE

Pathological gambling (PG) has recently been considered as a "behavioral" or nonsubstance addiction. A comparison of the characteristics of PG and substance use disorders (SUDs) has clinical ramifications and could help advance future research on these conditions. Specific relationships with impulsivity and compulsivity may be central to understanding PG and SUDs.

OBJECTIVES

This review was conducted to compare and contrast research findings in PG and SUDs pertaining to neurocognitive tasks, brain function, and neurochemistry, with a focus on impulsivity and compulsivity.

RESULTS

Multiple similarities were found between PG and SUDs, including poor performance on neurocognitive tasks, specifically with respect to impulsive choice and response tendencies and compulsive features (e.g., response perseveration and action with diminished relationship to goals or reward). Findings suggest dysfunction involving similar brain regions, including the ventromedial prefrontal cortex and striatum and similar neurotransmitter systems, including dopaminergic and serotonergic. Unique features exist which may in part reflect influences of acute or chronic exposures to specific substances.

CONCLUSIONS

Both similarities and differences exist between PG and SUDs. Understanding these similarities more precisely may facilitate treatment development across addictions, whereas understanding differences may provide insight into treatment development for specific disorders. Individual differences in features of impulsivity and compulsivity may represent important endophenotypic targets for prevention and treatment strategies.

Impulsivity and Parkinson's disease: more than just disinhibition

In the last few years it has become clear that impulsivity is a complex behaviour composed of different domains and dependent on different neural networks. The proposed pathogenetic mechanisms for the emergence of impulsivity disorders in Parkinson's Disease (PD) can be broadly separated into three potentially interacting processes: the contribution of premorbid susceptibility to impulsivity, the contribution of the disease itself to the behaviour and the potential contribution of therapeutic agents. Growing evidence suggests that dopamine and the subthalamic nucleus are playing a certain role in the pathophysiology of different aspects of impulsivity. In this review, we summarise the main concepts defining various components of impulsivity both in healthy subjects and patients affected by PD.