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Tzvi E, Bey R, Nitschke M, Brüggemann N, Classen J, Münte TF, Krämer UM, Rumpf JJ. Motor Sequence Learning Deficits in Idiopathic Parkinson's Disease Are Associated With Increased Substantia Nigra Activity. Front Aging Neurosci 2021; 13:685168. [PMID: 34194317 PMCID: PMC8236713 DOI: 10.3389/fnagi.2021.685168] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2021] [Accepted: 05/21/2021] [Indexed: 11/19/2022] Open
Abstract
Previous studies have shown that persons with Parkinson’s disease (pwPD) share specific deficits in learning new sequential movements, but the neural substrates of this impairment remain unclear. In addition, the degree to which striatal dopaminergic denervation in PD affects the cortico-striato-thalamo-cerebellar motor learning network remains unknown. We aimed to answer these questions using fMRI in 16 pwPD and 16 healthy age-matched control subjects while they performed an implicit motor sequence learning task. While learning was absent in both pwPD and controls assessed with reaction time differences between sequential and random trials, larger error-rates during the latter suggest that at least some of the complex sequence was encoded. Moreover, we found that while healthy controls could improve general task performance indexed by decreased reaction times across both sequence and random blocks, pwPD could not, suggesting disease-specific deficits in learning of stimulus-response associations. Using fMRI, we found that this effect in pwPD was correlated with decreased activity in the hippocampus over time. Importantly, activity in the substantia nigra (SN) and adjacent bilateral midbrain was specifically increased during sequence learning in pwPD compared to healthy controls, and significantly correlated with sequence-specific learning deficits. As increased SN activity was also associated (on trend) with higher doses of dopaminergic medication as well as disease duration, the results suggest that learning deficits in PD are associated with disease progression, indexing an increased drive to recruit dopaminergic neurons in the SN, however, unsuccessfully. Finally, there were no differences between pwPD and controls in task modulation of the cortico-striato-thalamo-cerebellar network. However, a restricted nigral-striatal model showed that negative modulation of SN to putamen connection was larger in pwPD compared to controls during random trials, while no differences between the groups were found during sequence learning. We speculate that learning-specific SN recruitment leads to a relative increase in SN- > putamen connectivity, which returns to a pathological reduced state when no learning takes place.
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Affiliation(s)
- Elinor Tzvi
- Department of Neurology, University of Leipzig, Leipzig, Germany
| | - Richard Bey
- Department of Neurology, University of Lübeck, Lübeck, Germany
| | | | - Norbert Brüggemann
- Department of Neurology, University of Lübeck, Lübeck, Germany.,Institute of Neurogenetics, University of Lübeck, Lübeck, Germany
| | - Joseph Classen
- Department of Neurology, University of Leipzig, Leipzig, Germany
| | - Thomas F Münte
- Department of Neurology, University of Lübeck, Lübeck, Germany.,Department of Psychology, University of Lübeck, Lübeck, Germany.,Center of Brain, Behavior and Metabolism, University of Lübeck, Lübeck, Germany
| | - Ulrike M Krämer
- Department of Neurology, University of Lübeck, Lübeck, Germany.,Department of Psychology, University of Lübeck, Lübeck, Germany.,Center of Brain, Behavior and Metabolism, University of Lübeck, Lübeck, Germany
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2
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Stimulation of the vagus nerve reduces learning in a go/no-go reinforcement learning task. Eur Neuropsychopharmacol 2020; 35:17-29. [PMID: 32404279 DOI: 10.1016/j.euroneuro.2020.03.023] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/22/2019] [Revised: 02/06/2020] [Accepted: 03/27/2020] [Indexed: 02/06/2023]
Abstract
When facing decisions to approach rewards or to avoid punishments, we often figuratively go with our gut, and the impact of metabolic states such as hunger on motivation are well documented. However, whether and how vagal feedback signals from the gut influence instrumental actions is unknown. Here, we investigated the effect of non-invasive transcutaneous auricular vagus nerve stimulation (taVNS) vs. sham (randomized cross-over design) on approach and avoidance behavior using an established go/no-go reinforcement learning paradigm in 39 healthy human participants (23 female) after an overnight fast. First, mixed-effects logistic regression analysis of choice accuracy showed that taVNS acutely impaired decision-making, p = .041. Computational reinforcement learning models identified the cause of this as a reduction in the learning rate through taVNS (∆α = -0.092, pboot = .002), particularly after punishment (∆αPun = -0.081, pboot = .012 vs. ∆αRew =-0.031, pboot = .22). However, taVNS had no effect on go biases, Pavlovian response biases or response time. Hence, taVNS appeared to influence learning rather than action execution. These results highlight a novel role of vagal afferent input in modulating reinforcement learning by tuning the learning rate according to homeostatic needs.
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3
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Al Jaja A, Grahn JA, Herrmann B, MacDonald PA. The effect of aging, Parkinson's disease, and exogenous dopamine on the neural response associated with auditory regularity processing. Neurobiol Aging 2020; 89:71-82. [PMID: 32057529 DOI: 10.1016/j.neurobiolaging.2020.01.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2019] [Revised: 11/25/2019] [Accepted: 01/01/2020] [Indexed: 01/10/2023]
Abstract
Processing regular patterns in auditory scenes is important for navigating complex environments. Electroencephalography studies find enhancement of sustained brain activity, correlating with the emergence of a regular pattern in sounds. How aging, aging-related diseases such as Parkinson's disease (PD), and treatment of PD with dopaminergic therapy affect this fundamental function remain unknown. We addressed this knowledge gap. Healthy younger and older adults and patients with PD listened to sounds that contained or were devoid of regular patterns. Healthy older adults and patients with PD were tested twice-off and on dopaminergic medication, in counterbalanced order. Regularity-evoked, sustained electroencephalography activity was reduced in older, compared with younger adults. Patients with PD and older controls evidenced comparable attenuation of the sustained response. Dopaminergic therapy further weakened the sustained response in both older controls and patients with PD. These findings suggest that fundamental regularity processing is impacted by aging but not specifically by PD. The finding that dopaminergic therapy attenuates rather than improves the sustained response coheres with the dopamine overdose response and is in line with previous findings that regularity processing implicates brain regions receiving dopamine from the ventral tegmental area that is relatively spared in PD and normal aging.
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Affiliation(s)
- Abdullah Al Jaja
- The Brain and Mind Institute, University of Western Ontario, London, Ontario, Canada; Schulich School of Medicine & Dentistry, Graduate Neuroscience Program, University of Western Ontario, London, Ontario, Canada
| | - Jessica A Grahn
- The Brain and Mind Institute, University of Western Ontario, London, Ontario, Canada; Department of Psychology, University of Western Ontario, London, Ontario, Canada
| | - Björn Herrmann
- The Brain and Mind Institute, University of Western Ontario, London, Ontario, Canada; Department of Psychology, University of Western Ontario, London, Ontario, Canada
| | - Penny A MacDonald
- The Brain and Mind Institute, University of Western Ontario, London, Ontario, Canada; Department of Clinical Neurological Sciences, University of Western Ontario, London, Ontario, Canada.
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4
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Levodopa does not affect expression of reinforcement learning in older adults. Sci Rep 2019; 9:6349. [PMID: 31015587 PMCID: PMC6478852 DOI: 10.1038/s41598-019-42904-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2018] [Accepted: 04/02/2019] [Indexed: 11/24/2022] Open
Abstract
Dopamine has been implicated in learning from rewards and punishment, and in the expression of this learning. However, many studies do not fully separate retrieval and decision mechanisms from learning and consolidation. Here, we investigated the effects of levodopa (dopamine precursor) on choice performance (isolated from learning or consolidation). We gave 31 healthy older adults 150 mg of levodopa or placebo (double-blinded, randomised) 1 hour before testing them on stimuli they had learned the value of the previous day. We found that levodopa did not affect the overall accuracy of choices, nor the relative expression of positively or negatively reinforced values. This contradicts several studies and suggests that overall dopamine levels may not play a role in the choice performance for values learned through reinforcement learning in older adults.
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5
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Dorsal striatum does not mediate feedback-based, stimulus-response learning: An event-related fMRI study in patients with Parkinson's disease tested on and off dopaminergic therapy. Neuroimage 2018; 185:455-470. [PMID: 30394326 DOI: 10.1016/j.neuroimage.2018.10.045] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2018] [Revised: 09/22/2018] [Accepted: 10/17/2018] [Indexed: 01/31/2023] Open
Abstract
Learning associations between stimuli and responses is essential to everyday life. Dorsal striatum (DS) has long been implicated in stimulus-response learning, though recent results challenge this contention. We have proposed that discrepant findings arise because stimulus-response learning methodology generally confounds learning and response selection processes. In 19 patients with Parkinson's disease (PD) and 18 age-matched controls, we found that dopaminergic therapy decreased the efficiency of stimulus-response learning, with corresponding attenuation of ventral striatum (VS) activation. In contrast, exogenous dopamine improved response selection accuracy related to enhanced DS BOLD signal. Contrasts between PD patients and controls fully support these within-subject patterns. These double dissociations in terms of behaviour and neural activity related to VS and DS in PD and in response to dopaminergic therapy, strongly refute the view that DS mediates stimulus-response learning through feedback. Our findings integrate with a growing literature favouring a role for DS in decision making rather than learning, and unite two literature that have been evolving independently.
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6
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Robertson BD, Al Jaja AS, MacDonald AA, Hiebert NM, Tamjeedi R, Seergobin KN, Schwarz UI, Kim RB, MacDonald PA. SLC6A3 Polymorphism Predisposes to Dopamine Overdose in Parkinson's Disease. Front Neurol 2018; 9:693. [PMID: 30186226 PMCID: PMC6110885 DOI: 10.3389/fneur.2018.00693] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2018] [Accepted: 07/31/2018] [Indexed: 12/22/2022] Open
Abstract
In Parkinson's disease (PD), cognitive functions mediated by brain regions innervated by ventral tegmental area (VTA) worsen with dopamine replacement therapy, whereas processes relying on regions innervated by the substantia nigra pars compacta (SNc) improve. The SLC6A3 gene encodes the dopamine transporter (DAT). The common 9R polymorphism produces higher DAT concentrations and consequently lower baseline dopamine than SLC6A3 wildtype. Whether SLC6A3 genotype modulates the effect of dopaminergic therapy on cognition in PD is not known. We investigated the effect of dopaminergic therapy and SLC6A3 genotype on encoding and recall of abstract images using the Aggie Figures Learning Test in PD patients. Encoding depends upon brain regions innervated by the VTA, whereas recall is mediated by widespread brain regions, a number innervated by the SNc. We found that dopaminergic therapy worsened encoding of abstract images in 9R carriers only. In contrast, dopaminergic therapy improved recall of abstract images in all PD patients, irrespective of SLC6A3 genotype. Our findings suggest that 9R-carrier PD patients are more predisposed to dopamine overdose and medication-induced impairment of cognitive functions mediated by VTA-innervated brain regions. Interestingly, PD patients without the 9R polymorphism did not show such an impairment. SLC6A3 genotype does not modulate the dopaminergic therapy-induced improvement of functions mediated by SNc-innervated regions in PD patients.
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Affiliation(s)
- Brian D Robertson
- Schulich School of Medicine & Dentistry, University of Western Ontario, London, ON, Canada
| | - Abdullah S Al Jaja
- Brain and Mind Institute, University of Western Ontario, London, ON, Canada.,Department of Neuroscience, University of Western Ontario, London, ON, Canada
| | - Alex A MacDonald
- Department of Medicine, Undergraduate Faculty of Medicine, University of Toronto, Toronto, ON, Canada
| | - Nole M Hiebert
- Brain and Mind Institute, University of Western Ontario, London, ON, Canada.,Department of Physiology and Pharmacology, University of Western Ontario, London, ON, Canada
| | | | - Ken N Seergobin
- Brain and Mind Institute, University of Western Ontario, London, ON, Canada
| | - Ute I Schwarz
- Department of Physiology and Pharmacology, University of Western Ontario, London, ON, Canada.,Division of Clinical Pharmacology, Department of Medicine, Schulich School of Medicine & Dentistry, University of Western Ontario, London, ON, Canada
| | - Richard B Kim
- Department of Physiology and Pharmacology, University of Western Ontario, London, ON, Canada.,Division of Clinical Pharmacology, Department of Medicine, Schulich School of Medicine & Dentistry, University of Western Ontario, London, ON, Canada
| | - Penny A MacDonald
- Brain and Mind Institute, University of Western Ontario, London, ON, Canada.,Department of Neuroscience, University of Western Ontario, London, ON, Canada.,Department of Physiology and Pharmacology, University of Western Ontario, London, ON, Canada.,Department of Clinical Neurological Sciences, Schulich School of Medicine & Dentistry, University of Western Ontario, London, ON, Canada
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7
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Perugini A, Ditterich J, Shaikh AG, Knowlton BJ, Basso MA. Paradoxical Decision-Making: A Framework for Understanding Cognition in Parkinson's Disease. Trends Neurosci 2018; 41:512-525. [PMID: 29747856 PMCID: PMC6124671 DOI: 10.1016/j.tins.2018.04.006] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2018] [Revised: 04/09/2018] [Accepted: 04/16/2018] [Indexed: 12/11/2022]
Abstract
People with Parkinson's disease (PD) show impaired decision-making when sensory and memory information must be combined. This recently identified impairment results from an inability to accumulate the proper amount of information needed to make a decision and appears to be independent of dopamine tone and reinforcement learning mechanisms. Although considerable work focuses on PD and decisions involving risk and reward, in this Opinion article we propose that the emerging findings in perceptual decision-making highlight the multisystem nature of PD, and that unraveling the neuronal circuits underlying perceptual decision-making impairment may help in understanding other cognitive impairments in people with PD. We also discuss how a decision-making framework may be extended to gain insights into mechanisms of motor impairments in PD.
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Affiliation(s)
- Alessandra Perugini
- Fuster Laboratory of Cognitive Neuroscience, Department of Psychiatry and Biobehavioral Sciences, Department of Neurobiology, Semel Institute for Neuroscience and Human Behavior, Brain Research Institute, The David Geffen School of Medicine, Los Angeles, CA 90095, USA
| | - Jochen Ditterich
- Center for Neuroscience and Department of Neurobiology, Physiology, and Behavior, University of California, Davis, CA, USA
| | - Aasef G Shaikh
- Department of Neurology, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Barbara J Knowlton
- Department of Psychology, University of California Los Angeles, Los Angeles, CA, USA
| | - Michele A Basso
- Fuster Laboratory of Cognitive Neuroscience, Department of Psychiatry and Biobehavioral Sciences, Department of Neurobiology, Semel Institute for Neuroscience and Human Behavior, Brain Research Institute, The David Geffen School of Medicine, Los Angeles, CA 90095, USA.
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8
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Vo A, Seergobin KN, MacDonald PA. Independent effects of age and levodopa on reversal learning in healthy volunteers. Neurobiol Aging 2018; 69:129-139. [PMID: 29894903 DOI: 10.1016/j.neurobiolaging.2018.05.014] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2017] [Revised: 05/02/2018] [Accepted: 05/10/2018] [Indexed: 11/25/2022]
Abstract
The dopamine overdose hypothesis has provided an important theoretical framework for understanding cognition in Parkinson's disease. It posits that effects of dopaminergic therapy on cognition in Parkinson's disease depend on baseline dopamine levels in brain regions that support different functions. Although functions performed by more severely dopamine-depleted brain regions improve with medication, those associated with less dopamine deficient areas are actually worsened. It is presumed that medication-related worsening of cognition owes to dopamine overdose. We investigated whether age-related changes in baseline dopamine levels would modulate effects of dopaminergic therapy on reward learning in healthy volunteers. In a double-blind, crossover design, healthy younger and older adults completed a probabilistic reversal learning task after treatment with 100/25 mg of levodopa/carbidopa versus placebo. Older adults learned more poorly than younger adults at baseline, being more likely to shift responses after misleading punishment. Levodopa worsened stimulus-reward learning relative to placebo to the same extent in both groups, irrespective of differences in baseline performance and expected dopamine levels. When order effects were eliminated, levodopa induced response shifts after reward more often than placebo. Our results reveal independent deleterious effects of age group and exogenous dopamine on reward learning, suggesting a more complex scenario than predicted by the dopamine overdose hypothesis.
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Affiliation(s)
- Andrew Vo
- Brain and Mind Institute, University of Western Ontario, London, Canada; Department of Psychology, University of Western Ontario, London, Canada
| | - Ken N Seergobin
- Brain and Mind Institute, University of Western Ontario, London, Canada
| | - Penny A MacDonald
- Brain and Mind Institute, University of Western Ontario, London, Canada; Department of Psychology, University of Western Ontario, London, Canada; Department of Clinical Neurological Sciences, Schulich School of Medicine & Dentistry, University of Western Ontario, London, Canada.
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9
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Perugini A, Basso MA. Perceptual decisions based on previously learned information are independent of dopaminergic tone. J Neurophysiol 2018; 119:849-861. [PMID: 29167328 PMCID: PMC5899318 DOI: 10.1152/jn.00761.2017] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2017] [Revised: 11/07/2017] [Accepted: 11/19/2017] [Indexed: 02/02/2023] Open
Abstract
Both cognitive and motor symptoms in people with Parkinson's disease (PD) arise from either too little or too much dopamine (DA). Akinesia stems from DA neuronal cell loss, and dyskinesia often stems from an overdose of DA medication. Cognitive behaviors typically associated with frontal cortical function, such as working memory and task switching, are also affected by too little or too much DA in PD. Whether motor and cognitive circuits overlap in PD is unknown. In this article, we show that whereas motor performance improves in people with PD when on dopaminergic medication compared with off medication, perceptual decision-making based on previously learned information (priors) remains impaired whether on or off medications. To rule out effects of long-term DA treatment and dopaminergic neuronal loss such as occur in PD, we also tested a group of people with dopa-unresponsive focal dystonia, a disease that involves the basal ganglia, like PD, but has motor symptoms that are insensitive to dopamine treatment and is not thought to involve frontal cortical DA circuits, unlike PD. We found that people with focal dystonia showed intact perceptual decision-making performance but impaired use of priors in perceptual decision-making, similar to people with PD. Together, the results show a dissociation between motor and cognitive performance in people with PD and reveal a novel cognitive impairment, independent of sensory and motor impairment, in people with focal dystonia. The combined results from people with PD and people with focal dystonia provide mechanistic insights into the role of basal ganglia non-dopaminergic circuits in perceptual decision-making based on priors.
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Affiliation(s)
- Alessandra Perugini
- Joaquin Fuster Laboratory of Cognitive Neuroscience, Department of Psychiatry and Biobehavioral Sciences, Department of Neurobiology, and The Semel Institute for Neuroscience and Human Behavior and the Brain Research Institute, David Geffen School of Medicine, University of California , Los Angeles, California
| | - Michele A Basso
- Joaquin Fuster Laboratory of Cognitive Neuroscience, Department of Psychiatry and Biobehavioral Sciences, Department of Neurobiology, and The Semel Institute for Neuroscience and Human Behavior and the Brain Research Institute, David Geffen School of Medicine, University of California , Los Angeles, California
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10
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Yang XQ, Lauzon B, Seergobin KN, MacDonald PA. Dopaminergic Therapy Increases Go Timeouts in the Go/No-Go Task in Patients with Parkinson's Disease. Front Hum Neurosci 2018; 11:642. [PMID: 29354045 PMCID: PMC5758505 DOI: 10.3389/fnhum.2017.00642] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2017] [Accepted: 12/18/2017] [Indexed: 11/13/2022] Open
Abstract
Parkinson's disease (PD) is characterized by resting tremor, rigidity and bradykinesia. Dopaminergic medications such as L-dopa treat these motor symptoms, but can have complex effects on cognition. Impulse control is an essential cognitive function. Impulsivity is multifaceted in nature. Motor impulsivity involves the inability to withhold pre-potent, automatic, erroneous responses. In contrast, cognitive impulsivity refers to improper risk-reward assessment guiding behavior. Informed by our previous research, we anticipated that dopaminergic therapy would decrease motor impulsivity though it is well known to enhance cognitive impulsivity. We employed the Go/No-go paradigm to assess motor impulsivity in PD. Patients with PD were tested using a Go/No-go task on and off their normal dopaminergic medication. Participants completed cognitive, mood, and physiological measures. PD patients on medication had a significantly higher proportion of Go trial Timeouts (i.e., trials in which Go responses were not completed prior to a deadline of 750 ms) compared to off medication (p = 0.01). No significant ON-OFF differences were found for Go trial or No-go trial response times (RTs), or for number of No-go errors. We interpret that dopaminergic therapy induces a more conservative response set, reflected in Go trial Timeouts in PD patients. In this way, dopaminergic therapy decreased motor impulsivity in PD patients. This is in contrast to the widely recognized effects of dopaminergic therapy on cognitive impulsivity leading in some patients to impulse control disorders. Understanding the nuanced effects of dopaminergic treatment in PD on cognitive functions such as impulse control will clarify therapeutic decisions.
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Affiliation(s)
- Xue Q. Yang
- MacDonald Lab, Brain and Mind Institute, University of Western Ontario, London, ON, Canada
| | - Brian Lauzon
- MacDonald Lab, Brain and Mind Institute, University of Western Ontario, London, ON, Canada
| | - Ken N. Seergobin
- MacDonald Lab, Brain and Mind Institute, University of Western Ontario, London, ON, Canada
| | - Penny A. MacDonald
- MacDonald Lab, Brain and Mind Institute, University of Western Ontario, London, ON, Canada
- Clinical Neurological Sciences, Schulich School of Medicine and Dentistry, University of Western Ontario, London, ON, Canada
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11
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Hiebert NM, Owen AM, Seergobin KN, MacDonald PA. Dorsal striatum mediates deliberate decision making, not late-stage, stimulus-response learning. Hum Brain Mapp 2017; 38:6133-6156. [PMID: 28945307 DOI: 10.1002/hbm.23817] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2017] [Revised: 08/08/2017] [Accepted: 09/07/2017] [Indexed: 11/09/2022] Open
Abstract
We investigated a controversy regarding the role of the dorsal striatum (DS) in deliberate decision-making versus late-stage, stimulus-response learning to the point of automatization. Participants learned to associate abstract images with right or left button presses explicitly before strengthening these associations through stimulus-response trials with (i.e., Session 1) and without (i.e., Session 2) feedback. In Session 1, trials were divided into response-selection and feedback events to separately assess decision versus learning processes. Session 3 evaluated stimulus-response automaticity using a location Stroop task. DS activity correlated with response-selection and not feedback events in Phase 1 (i.e., Blocks 1-3), Session 1. Longer response times (RTs), lower accuracy, and greater intertrial variability characterized Phase 1, suggesting deliberation. DS activity extinguished in Phase 2 (i.e., Blocks 4-12), Session 1, once RTs, response variability, and accuracy stabilized, though stimulus-response automatization continued. This was signaled by persisting improvements in RT and accuracy into Session 2. Distraction between Sessions 1 and 2 briefly reintroduced response uncertainty, and correspondingly, significant DS activity reappeared in Block 1 of Session 2 only. Once stimulus-response associations were again refamiliarized and deliberation unnecessary, DS activation disappeared for Blocks 2-8, Session 2. Interference from previously learned right or left button responses with incongruent location judgments in a location Stroop task provided evidence that automaticity of stimulus-specific button-press responses had developed by the end of Session 2. These results suggest that DS mediates decision making and not late-stage learning, reconciling two, independently evolving and well-supported literatures that implicate DS in different cognitive functions. Hum Brain Mapp 38:6133-6156, 2017. © 2017 Wiley Periodicals, Inc.
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Affiliation(s)
- Nole M Hiebert
- Brain and Mind Institute, University of Western Ontario, London, Ontario, N6A 5B7, Canada.,Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, N6A 5C1, Canada
| | - Adrian M Owen
- Brain and Mind Institute, University of Western Ontario, London, Ontario, N6A 5B7, Canada.,Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, N6A 5C1, Canada
| | - Ken N Seergobin
- Brain and Mind Institute, University of Western Ontario, London, Ontario, N6A 5B7, Canada
| | - Penny A MacDonald
- Brain and Mind Institute, University of Western Ontario, London, Ontario, N6A 5B7, Canada.,Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, N6A 5C1, Canada.,Department of Clinical Neurological Sciences, University of Western Ontario, London, Ontario, N6A 5A5, Canada
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12
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Yang XQ, Glizer D, Vo A, Seergobin KN, MacDonald PA. Pramipexole Increases Go Timeouts but Not No-go Errors in Healthy Volunteers. Front Hum Neurosci 2016; 10:523. [PMID: 27803657 PMCID: PMC5067488 DOI: 10.3389/fnhum.2016.00523] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2016] [Accepted: 10/03/2016] [Indexed: 12/03/2022] Open
Abstract
Parkinson's disease (PD) is characterized by motor symptoms, such as resting tremor, bradykinesia and rigidity, but also features non-motor complications. PD patients taking dopaminergic therapy, such as levodopa but especially dopamine agonists (DAs), evidence an increase in impulse control disorders (ICDs), suggesting a link between dopaminergic therapy and impulsive pursuit of pleasurable activities. However, impulsivity is a multifaceted construct. Motor impulsivity refers to the inability to overcome automatic responses or cancel pre-potent responses. Previous research has suggested that PD patients, on dopaminergic medications, have decreased motor impulsivity. Whether effects on impulsivity are main effects of dopaminergic therapies or are specific to PD is unclear. Using a Go No-go task, we investigated the effect of a single dose of the DA pramipexole on motor impulsivity in healthy participants. The Go No-go task consisted of Go trials, for which keystroke responses were made as quickly as possible, and lesser frequency No-go trials, on which motor responses were to be inhibited. We hypothesized that pramipexole would decrease motor impulsivity. This would manifest as: (a) fewer No-go errors (i.e., fewer responses on trials in which a response ought to have been inhibited); and (b) more timed-out Go trials (i.e., more trials on which the deadline elapsed before a decision to make a keystroke occurred). Healthy volunteers were treated with either 0.5 mg of pramipexole or a standard placebo (randomly determined). During the 2-h wait period, they completed demographic, cognitive, physiological and affective measures. The pramipexole group had significantly more Go timeouts (p < 0.05) compared to the placebo group though they did not differ in percent of No-go errors. In contrast to its effect on pursuit of pleasurable activities, pramipexole did not increase motor impulsivity. In fact, in line with findings in PD and addiction, dopaminergic therapy might increase motor impulse control. In these patient groups, by enhancing function of the dorsal striatum (DS) of the basal ganglia in contrast to its effect on impulsive pursuit of pleasurable activities. These findings have implications for use and effects of pramipexole in PD as well as in other conditions (e.g., restless leg, dystonia, depression, addiction-related problems).
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Affiliation(s)
- Xue Qing Yang
- MacDonald Lab, Brain and Mind Institute, University of Western OntarioLondon, ON, Canada
| | - Daniel Glizer
- MacDonald Lab, Brain and Mind Institute, University of Western OntarioLondon, ON, Canada
| | - Andrew Vo
- MacDonald Lab, Brain and Mind Institute, University of Western OntarioLondon, ON, Canada
| | - Ken N. Seergobin
- MacDonald Lab, Brain and Mind Institute, University of Western OntarioLondon, ON, Canada
| | - Penny A. MacDonald
- MacDonald Lab, Brain and Mind Institute, University of Western OntarioLondon, ON, Canada
- Clinical Neurological Sciences, Schulich School of Medicine and Dentistry, University of Western OntarioLondon, ON, Canada
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13
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Gallant H, Vo A, Seergobin KN, MacDonald PA. Pramipexole Impairs Stimulus-Response Learning in Healthy Young Adults. Front Neurosci 2016; 10:374. [PMID: 27594823 PMCID: PMC4990534 DOI: 10.3389/fnins.2016.00374] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2016] [Accepted: 08/02/2016] [Indexed: 01/31/2023] Open
Abstract
Dopaminergic therapy has paradoxical effects on cognition in Parkinson's disease (PD) patients, with some functions worsened and others improved. The dopamine overdose hypothesis is proposed as an explanation for these opposing effects of medication taking into account the varying levels of dopamine within different brain regions in PD. The detrimental effects of medication on cognition have been attributed to exogenous dopamine overdose in brain regions with spared dopamine levels in PD. It has been demonstrated that learning is most commonly worsened by dopaminergic medication. The current study aimed to investigate whether the medication-related learning impairment exhibited in PD patients is due to a main effect of medication by evaluating the dopamine overdose hypothesis in healthy young adults. Using a randomized, double-blind, placebo-controlled design, 40 healthy young undergraduate students completed a stimulus-response learning task. Half of the participants were treated with 0.5 mg of pramipexole, a dopamine agonist, whereas the other half were treated with a placebo. We found that stimulus-response learning was significantly impaired in participants on pramipexole relative to placebo controls. These findings are consistent with the dopamine overdose hypothesis and suggest that dopaminergic medication impairs learning independent of PD pathology. Our results have important clinical implications for conditions treated with pramipexole, particularly PD, restless leg syndrome, some forms of dystonia, and potentially depression.
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Affiliation(s)
- Haley Gallant
- The Brain and Mind Institute, University of Western Ontario London, ON, Canada
| | - Andrew Vo
- The Brain and Mind Institute, University of Western OntarioLondon, ON, Canada; Department of Psychology, University of Western OntarioLondon, ON, Canada
| | - Ken N Seergobin
- The Brain and Mind Institute, University of Western Ontario London, ON, Canada
| | - Penny A MacDonald
- The Brain and Mind Institute, University of Western OntarioLondon, ON, Canada; Department of Psychology, University of Western OntarioLondon, ON, Canada; Department of Clinical Neurological Sciences, University of Western OntarioLondon, ON, Canada
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Vo A, Seergobin KN, Morrow SA, MacDonald PA. Levodopa impairs probabilistic reversal learning in healthy young adults. Psychopharmacology (Berl) 2016; 233:2753-63. [PMID: 27241710 DOI: 10.1007/s00213-016-4322-x] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/19/2015] [Accepted: 05/05/2016] [Indexed: 11/28/2022]
Abstract
RATIONALE Dopaminergic therapy improves some cognitive functions and worsens others in patients with Parkinson's disease (PD). These paradoxical effects are explained by the dopamine overdose hypothesis, which proposes that effects of dopaminergic therapy on a cognitive function is determined by the baseline dopamine levels in brain regions mediating that function. OBJECTIVES We directly tested this prevalent hypothesis, evaluating the effects of levodopa on stimulus-reward learning in healthy young adults, who presumably have optimal baseline dopamine levels and dopamine regulation. METHODS Twenty-six healthy, young adults completed a probabilistic reversal learning task in a randomized, double-blind, placebo-controlled, crossover design. Participants completed one session on levodopa 100 mg/carbidopa 25 mg and another session on placebo. RESULTS We found that levodopa impaired reversal learning relative to placebo. Further analyses revealed that levodopa impaired learning from both punishment and reward. CONCLUSIONS Exogenous dopamine impairs stimulus-reward learning, independent of PD pathology and prior to sensitization through repeated exposure, in healthy adults with normal cognition and baseline dopamine function. Our findings support the dopamine overdose hypothesis and caution clinicians about detrimental effects of levodopa in all clinical populations (e.g., early PD, restless leg syndrome) regardless of baseline cognitive and dopaminergic system function.
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Affiliation(s)
- Andrew Vo
- Brain and Mind Institute, University of Western Ontario, London, ON, Canada.,Department of Psychology, University of Western Ontario, London, ON, Canada
| | - Ken N Seergobin
- Brain and Mind Institute, University of Western Ontario, London, ON, Canada
| | - Sarah A Morrow
- Department of Clinical Neurological Sciences, University of Western Ontario, London, ON, Canada
| | - Penny A MacDonald
- Brain and Mind Institute, University of Western Ontario, London, ON, Canada. .,Department of Psychology, University of Western Ontario, London, ON, Canada. .,Department of Clinical Neurological Sciences, University of Western Ontario, London, ON, Canada.
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Apathy and noradrenaline: silent partners to mild cognitive impairment in Parkinson's disease? Curr Opin Neurol 2016; 28:344-50. [PMID: 26110801 DOI: 10.1097/wco.0000000000000218] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
PURPOSE OF REVIEW Mild cognitive impairment (MCI) is a comorbid factor in Parkinson's disease. The aim of this review is to examine the recent neuroimaging findings in the search for Parkinson's disease MCI (PD-MCI) biomarkers to gain insight on whether MCI and specific cognitive deficits in Parkinson's disease implicate striatal dopamine or another system. RECENT FINDINGS The evidence implicates a diffuse pathophysiology in PD-MCI rather than acute dopaminergic involvement. On the one hand, performance in specific cognitive domains, notably in set-shifting and learning, appears to vary with dopaminergic status. On the other hand, motivational states in Parkinson's disease along with their behavioral and physiological indices suggest a noradrenergic contribution to cognitive deficits in Parkinson's disease. Finally, Parkinson's disease's pattern of neurodegeneration offers an avenue for continued research in nigrostriatal dopamine's role in distinct behaviors, as well as the specification of dorsal and ventral striatal functions. SUMMARY The search for PD-MCI biomarkers has employed an array of neuroimaging techniques, but still yields divergent findings. This may be due in part to MCI's broad definition, encompassing heterogeneous cognitive domains, only some of which are affected in Parkinson's disease. Most domains falling under the MCI umbrella include fronto-dependent executive functions, whereas others, notably learning, rely on the basal ganglia. Given the deterioration of the nigrostriatal dopaminergic system in Parkinson's disease, it has been the prime target of PD-MCI investigation. By testing well defined cognitive deficits in Parkinson's disease, distinct functions can be attributed to specific neural systems, overcoming conflicting results on PD-MCI. Apart from dopamine, other systems such as the neurovascular or noradrenergic systems are affected in Parkinson's disease. These factors may be at the basis of specific facets of PD-MCI for which dopaminergic involvement has not been conclusive. Finally, the impact of both dopaminergic and noradrenergic deficiency on motivational states in Parkinson's disease is examined in light of a plausible link between apathy and cognitive deficits.
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Robertson BD, Hiebert NM, Seergobin KN, Owen AM, MacDonald PA. Dorsal striatum mediates cognitive control, not cognitive effort per se , in decision-making: An event-related fMRI study. Neuroimage 2015; 114:170-84. [DOI: 10.1016/j.neuroimage.2015.03.082] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2014] [Revised: 03/20/2015] [Accepted: 03/28/2015] [Indexed: 10/23/2022] Open
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Xi C, Zhu Y, Mu Y, Chen B, Dong B, Cheng H, Hu P, Zhu C, Wang K. Theory of mind and decision-making processes are impaired in Parkinson's disease. Behav Brain Res 2015; 279:226-33. [DOI: 10.1016/j.bbr.2014.11.035] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2014] [Revised: 11/16/2014] [Accepted: 11/20/2014] [Indexed: 11/26/2022]
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Hiebert NM, Seergobin KN, Vo A, Ganjavi H, MacDonald PA. Dopaminergic therapy affects learning and impulsivity in Parkinson's disease. Ann Clin Transl Neurol 2014; 1:833-43. [PMID: 25493274 PMCID: PMC4241810 DOI: 10.1002/acn3.128] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2014] [Revised: 07/29/2014] [Accepted: 09/04/2014] [Indexed: 11/09/2022] Open
Abstract
OBJECTIVE The aim was to examine the effect of dopaminergic medication on stimulus-response learning versus performing decisions based on learning. METHOD To see the effect of dopaminergic therapy on stimulus-response learning and response selection, participants with Parkinson's disease (PD) were either tested on and/or off their prescribed dose of dopaminergic therapy during different testing days. Forty participants with PD and 34 healthy controls completed the experiment on consecutive days. On Day 1, participants learned to associate abstract images with spoken, "right" or "left" responses via feedback (Session 1). On Day 2, participants recalled these responses (Session 2) and indicated the location (i.e., right or left of center) of previously studied images intermixed with new images (Session 3). RESULTS Participants with PD off medication learned stimulus-response associations equally well compared to healthy controls. Learning was impaired by dopaminergic medication. Regardless of medication status, patients recalled the stimulus-response associations from Day 1 as well as controls. In Session 3 off medication, patients demonstrated enhanced facilitation relative to controls and patients on medication, when the stimulus location was congruent with the spoken response that was learned for the stimulus in Session 1. INTERPRETATION Learning in PD was comparable to that of healthy controls off medication. Learning was worsened by dopaminergic therapy in PD. We interpret greater facilitation in participants with PD off medication for congruent responses as evidence of greater impulsivity. This motor or reflexive impulsivity was normalized by medication in PD. These findings shed light on the cognitive profile of PD and have implications for dopaminergic treatment.
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Affiliation(s)
- Nole M Hiebert
- Brain and Mind Institute, University of Western Ontario London, Ontario, Canada, N6A 5B7 ; Department of Physiology and Pharmacology, University of Western Ontario London, Ontario, Canada, N6A 5C1
| | - Ken N Seergobin
- Brain and Mind Institute, University of Western Ontario London, Ontario, Canada, N6A 5B7
| | - Andrew Vo
- Brain and Mind Institute, University of Western Ontario London, Ontario, Canada, N6A 5B7 ; Department of Psychology, University of Western Ontario London, Ontario, Canada, N6A 5C2
| | - Hooman Ganjavi
- Department of Psychiatry, University of Western Ontario London, Ontario, Canada, N6A 5W9
| | - Penny A MacDonald
- Brain and Mind Institute, University of Western Ontario London, Ontario, Canada, N6A 5B7 ; Department of Physiology and Pharmacology, University of Western Ontario London, Ontario, Canada, N6A 5C1 ; Department of Psychology, University of Western Ontario London, Ontario, Canada, N6A 5C2 ; Department of Clinical Neurological Sciences, University of Western Ontario London, Ontario, Canada, N6A 5A5
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