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Leow LA, Bernheine L, Carroll TJ, Dux PE, Filmer HL. Dopamine Increases Accuracy and Lengthens Deliberation Time in Explicit Motor Skill Learning. eNeuro 2024; 11:ENEURO.0360-23.2023. [PMID: 38238069 PMCID: PMC10849023 DOI: 10.1523/eneuro.0360-23.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2023] [Revised: 11/23/2023] [Accepted: 11/28/2023] [Indexed: 01/23/2024] Open
Abstract
Although animal research implicates a central role for dopamine in motor skill learning, a direct causal link has yet to be established in neurotypical humans. Here, we tested if a pharmacological manipulation of dopamine alters motor learning, using a paradigm which engaged explicit, goal-directed strategies. Participants (27 females; 11 males; aged 18-29 years) first consumed either 100 mg of levodopa (n = 19), a dopamine precursor that increases dopamine availability, or placebo (n = 19). Then, during training, participants learnt the explicit strategy of aiming away from presented targets by instructed angles of varying sizes. Targets jumped mid-movement by the instructed aiming angle. Task success was thus contingent upon aiming accuracy and not speed. The effect of the dopamine manipulations on skill learning was assessed during training and after an overnight follow-up. Increasing dopamine availability at training improved aiming accuracy and lengthened reaction times, particularly for larger, more difficult aiming angles, both at training and, importantly, at follow-up, despite prominent session-by-session performance improvements in both accuracy and speed. Exogenous dopamine thus seems to result in a learnt, persistent propensity to better adhere to task goals. Results support the proposal that dopamine is important in engagement of instrumental motivation to optimize adherence to task goals, particularly when learning to execute goal-directed strategies in motor skill learning.
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Affiliation(s)
- Li-Ann Leow
- School of Psychology, The University of Queensland, St Lucia, 4072, Australia
- Centre for Sensorimotor Performance, School of Human Movement & Nutrition Sciences, St Lucia, 4067, Australia
| | - Lena Bernheine
- Centre for Sensorimotor Performance, School of Human Movement & Nutrition Sciences, St Lucia, 4067, Australia
- School of Sport Science Faculty of Sport Governance and Event Management, University of Bayreuth, 95447 Bayreuth, Germany
| | - Timothy J Carroll
- Centre for Sensorimotor Performance, School of Human Movement & Nutrition Sciences, St Lucia, 4067, Australia
| | - Paul E Dux
- School of Psychology, The University of Queensland, St Lucia, 4072, Australia
| | - Hannah L Filmer
- School of Psychology, The University of Queensland, St Lucia, 4072, Australia
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2
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Ghanavati E, Salehinejad MA, De Melo L, Nitsche MA, Kuo MF. NMDA receptor-related mechanisms of dopaminergic modulation of tDCS-induced neuroplasticity. Cereb Cortex 2022; 32:5478-5488. [PMID: 35165699 PMCID: PMC9712712 DOI: 10.1093/cercor/bhac028] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2021] [Revised: 01/14/2022] [Accepted: 01/15/2022] [Indexed: 12/27/2022] Open
Abstract
Dopamine is a key neuromodulator of neuroplasticity and an important neuronal substrate of learning, and memory formation, which critically involves glutamatergic N-methyl-D-aspartate (NMDA) receptors. Dopamine modulates NMDA receptor activity via dopamine D1 and D2 receptor subtypes. It is hypothesized that dopamine focuses on long-term potentiation (LTP)-like plasticity, i.e. reduces diffuse widespread but enhances locally restricted plasticity via a D2 receptor-dependent NMDA receptor activity reduction. Here, we explored NMDA receptor-dependent mechanisms underlying dopaminergic modulation of LTP-like plasticity induced by transcranial direct current stimulation (tDCS). Eleven healthy, right-handed volunteers received anodal tDCS (1 mA, 13 min) over the left motor cortex combined with dopaminergic agents (the D2 receptor agonist bromocriptine, levodopa for general dopamine enhancement, or placebo) and the partial NMDA receptor agonist D-cycloserine (dosages of 50, 100, and 200 mg, or placebo). Cortical excitability was monitored by transcranial magnetic stimulation-induced motor-evoked potentials. We found that LTP-like plasticity was abolished or converted into LTD-like plasticity via dopaminergic activation, but reestablished under medium-dose D-cycloserine. These results suggest that diffuse LTP-like plasticity is counteracted upon via D2 receptor-dependent reduction of NMDA receptor activity.
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Affiliation(s)
- Elham Ghanavati
- Department of Psychology and Neurosciences, Leibniz Research Centre for Working Environment and Human Factors, Ardeystr. 67, 44139 Dortmund, Germany
| | - Mohammad Ali Salehinejad
- Department of Psychology and Neurosciences, Leibniz Research Centre for Working Environment and Human Factors, Ardeystr. 67, 44139 Dortmund, Germany
| | - Lorena De Melo
- Department of Psychology and Neurosciences, Leibniz Research Centre for Working Environment and Human Factors, Ardeystr. 67, 44139 Dortmund, Germany,International Graduate School of Neuroscience, Ruhr University Bochum, Universitätsstr. 150, 44801 Bochum, Germany
| | | | - Min-Fang Kuo
- Corresponding address: Department of Psychology and Neurosciences, Leibniz Research Centre for Working Environment and Human Factors, Ardeystr 67, 44139 Dortmund, Germany.
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Mi TM, Zhang W, McKeown MJ, Chan P. Impaired Formation and Expression of Goal-Directed and Habitual Control in Parkinson's Disease. Front Aging Neurosci 2021; 13:734807. [PMID: 34759813 PMCID: PMC8574955 DOI: 10.3389/fnagi.2021.734807] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2021] [Accepted: 09/23/2021] [Indexed: 11/30/2022] Open
Abstract
Selective depletion of dopaminergic neurotransmission in the caudal sensorimotor striatum, a subdivision implicated in habitual control, is a major pathological feature in Parkinson’s disease (PD). Here, we evaluated the effects of PD on the formation of goal-directed and habitual control during learning, and for the first time investigated the conflict between these two strategies in the expression of acquired learning. Twenty PD patients and 20 healthy individuals participated in a set of tasks designed to assess relative goal-directed versus habitual behavioral control. In the instrumental training phase, participants first learned by trial and error to respond to different pictured stimuli in order to gain rewarding outcomes. Three associations were trained, with standard and congruent associations mediated predominantly by goal-directed action, and incongruent association regulated predominantly by habitual control. In a subsequent “slips-of-action” test, participants were assessed to determine whether they can flexibly adjust their behavior to changes in the desirability of the outcomes. A baseline test was then administered to rule out the possibility of general inhibitory deficit, and a questionnaire was finally adopted to test the explicit knowledge of the relationships between stimuli, responses, and outcomes. Our results showed that during the instrumental training phase, PD patients had impaired learning not only of the standard and congruent associations (mediated by goal-directed system), but also the incongruent association (mediated by habitual control system). In the slips-of-action test, PD patients responded less for valuable outcomes and more often to stimuli that were associated with devalued outcomes, with poor performance predicted by symptom severity. No significant difference was found between PD and healthy subjects for the baseline test and questionnaire performance. These results collectively demonstrate that the formation of both goal-directed and habitual control are impaired in PD patients. Furthermore, PD patients are more prone to slips of action, suggesting PD patients exhibit an impairment in engaging the goal-directed system with a relatively excessive reliance on habitual control in the expression of acquired learning.
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Affiliation(s)
- Tao-Mian Mi
- Department of Neurology, Neurobiology and Geriatrics, Xuanwu Hospital of Capital Medical University, Beijing Institute for Brain Disorders, Beijing, China.,National Clinical Research Center for Geriatric Disorders, Beijing, China
| | - Wei Zhang
- Department of Neurology, Neurobiology and Geriatrics, Xuanwu Hospital of Capital Medical University, Beijing Institute for Brain Disorders, Beijing, China.,Department of Neurology, The Affiliated Hospital of Xuzhou Medical University, Xuzhou, China
| | - Martin J McKeown
- Pacific Parkinson's Research Centre, University of British Columbia, Vancouver, BC, Canada.,Division of Neurology, Department of Medicine, University of British Columbia, Vancouver, BC, Canada
| | - Piu Chan
- Department of Neurology, Neurobiology and Geriatrics, Xuanwu Hospital of Capital Medical University, Beijing Institute for Brain Disorders, Beijing, China.,National Clinical Research Center for Geriatric Disorders, Beijing, China.,Clinical Center for Parkinson's Disease, Capital Medical University, Beijing, China.,Key Laboratory for Neurodegenerative Disease of the Ministry of Education, Beijing Key Laboratory for Parkinson's Disease, Beijing, China
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4
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Palidis DJ, McGregor HR, Vo A, MacDonald PA, Gribble PL. Null effects of levodopa on reward- and error-based motor adaptation, savings, and anterograde interference. J Neurophysiol 2021; 126:47-67. [PMID: 34038228 DOI: 10.1152/jn.00696.2020] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Dopamine signaling is thought to mediate reward-based learning. We tested for a role of dopamine in motor adaptation by administering the dopamine precursor levodopa to healthy participants in two experiments involving reaching movements. Levodopa has been shown to impair reward-based learning in cognitive tasks. Thus, we hypothesized that levodopa would selectively impair aspects of motor adaptation that depend on the reinforcement of rewarding actions. In the first experiment, participants performed two separate tasks in which adaptation was driven either by visual error-based feedback of the hand position or binary reward feedback. We used EEG to measure event-related potentials evoked by task feedback. We hypothesized that levodopa would specifically diminish adaptation and the neural responses to feedback in the reward learning task. However, levodopa did not affect motor adaptation in either task nor did it diminish event-related potentials elicited by reward outcomes. In the second experiment, participants learned to compensate for mechanical force field perturbations applied to the hand during reaching. Previous exposure to a particular force field can result in savings during subsequent adaptation to the same force field or interference during adaptation to an opposite force field. We hypothesized that levodopa would diminish savings and anterograde interference, as previous work suggests that these phenomena result from a reinforcement learning process. However, we found no reliable effects of levodopa. These results suggest that reward-based motor adaptation, savings, and interference may not depend on the same dopaminergic mechanisms that have been shown to be disrupted by levodopa during various cognitive tasks.NEW & NOTEWORTHY Motor adaptation relies on multiple processes including reinforcement of successful actions. Cognitive reinforcement learning is impaired by levodopa-induced disruption of dopamine function. We administered levodopa to healthy adults who participated in multiple motor adaptation tasks. We found no effects of levodopa on any component of motor adaptation. This suggests that motor adaptation may not depend on the same dopaminergic mechanisms as cognitive forms or reinforcement learning that have been shown to be impaired by levodopa.
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Affiliation(s)
- Dimitrios J Palidis
- Brain and Mind Institute, Western University, London, Ontario, Canada.,Department of Psychology, Western University, London, Ontario, Canada.,Graduate Program in Neuroscience, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada
| | - Heather R McGregor
- Department of Applied Physiology and Kinesiology, University of Florida, Gainesville, Florida
| | - Andrew Vo
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
| | - Penny A MacDonald
- Brain and Mind Institute, Western University, London, Ontario, Canada.,Department of Psychology, Western University, London, Ontario, Canada.,Department of Physiology and Pharmacology, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada.,Department of Clinical Neurological Sciences, University of Western Ontario, London, Ontario, Canada
| | - Paul L Gribble
- Brain and Mind Institute, Western University, London, Ontario, Canada.,Department of Psychology, Western University, London, Ontario, Canada.,Department of Physiology and Pharmacology, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada.,Haskins Laboratories, New Haven, Connecticut
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5
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Fearon C, Butler JS, Waechter SM, Killane I, Kelly SP, Reilly RB, Lynch T. Neurophysiological correlates of dual tasking in people with Parkinson's disease and freezing of gait. Exp Brain Res 2020; 239:175-187. [PMID: 33135132 DOI: 10.1007/s00221-020-05968-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2019] [Accepted: 10/21/2020] [Indexed: 11/24/2022]
Abstract
Freezing of gait in people with Parkinson's disease (PwP) is associated with executive dysfunction and motor preparation deficits. We have recently shown that electrophysiological markers of motor preparation, rather than decision-making, differentiate PwP with freezing of gait (FOG +) and without (FOG -) while sitting. To examine the effect of locomotion on these results, we measured behavioural and electrophysiological responses in PwP with and without FOG during a target response time task while sitting (single-task) and stepping-in-place (dual-task). Behavioural and electroencephalographic data were acquired from 18 PwP (eight FOG +) and seven young controls performing the task while sitting and stepping-in-place. FOG + had slower response times while stepping compared with sitting. However, response times were significantly faster while stepping compared with sitting for controls. Electrophysiological responses showed no difference in decision-making potentials (centroparietal positivity) between groups or conditions but there were differences in neurophysiological markers of response inhibition (N2) and motor preparation (lateralized readiness potential, LRP) in FOG + while performing a dual-task. This suggests that the addition of a second complex motor task (stepping-in-place) impacts automatic allocation of resources in FOG +, resulting in delayed response times. The impact of locomotion on the generation of the N2 and LRP potentials, particularly in freezers, indirectly implies that these functions compete with locomotion for resources. In the setting of multiple complex tasks or cognitive impairment, severe motor dysfunction may result, leading to freezing of gait.
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Affiliation(s)
- Conor Fearon
- Trinity Centre for Bioengineering, The School of Medicine and the School of Engineering, Trinity College, The University of Dublin, Dublin 2, Ireland.
- School of Engineering, Trinity College, The University of Dublin, Dublin 2, Ireland.
- Dublin Neurological Institute at the Mater Misericordiae University Hospital, 57 Eccles Street, Dublin 7, Ireland.
| | - John S Butler
- Trinity Centre for Bioengineering, The School of Medicine and the School of Engineering, Trinity College, The University of Dublin, Dublin 2, Ireland.
- School of Mathematical Sciences, Technological University Dublin, Kevin Street, Dublin, Ireland.
- School of Medicine, Trinity College, The University of Dublin, Dublin 2, Ireland.
| | - Saskia M Waechter
- Trinity Centre for Bioengineering, The School of Medicine and the School of Engineering, Trinity College, The University of Dublin, Dublin 2, Ireland
- School of Engineering, Trinity College, The University of Dublin, Dublin 2, Ireland
| | - Isabelle Killane
- Trinity Centre for Bioengineering, The School of Medicine and the School of Engineering, Trinity College, The University of Dublin, Dublin 2, Ireland
- School of Engineering, Trinity College, The University of Dublin, Dublin 2, Ireland
- School of Mechanical and Design Engineering, Technological University Dublin, Bolton Street, Dublin, Ireland
| | - Simon P Kelly
- School of Electrical and Electronic Engineering, University College Dublin, Dublin 4, Ireland
| | - Richard B Reilly
- Trinity Centre for Bioengineering, The School of Medicine and the School of Engineering, Trinity College, The University of Dublin, Dublin 2, Ireland
- School of Engineering, Trinity College, The University of Dublin, Dublin 2, Ireland
- School of Medicine, Trinity College, The University of Dublin, Dublin 2, Ireland
| | - Timothy Lynch
- Dublin Neurological Institute at the Mater Misericordiae University Hospital, 57 Eccles Street, Dublin 7, Ireland
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Gibson AS, Keefe KA, Furlong TM. Accelerated habitual learning resulting from L-dopa exposure in rats is prevented by N-acetylcysteine. Pharmacol Biochem Behav 2020; 198:173033. [PMID: 32888972 DOI: 10.1016/j.pbb.2020.173033] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/06/2020] [Revised: 08/29/2020] [Accepted: 08/31/2020] [Indexed: 10/23/2022]
Abstract
Instrumental actions are initially goal-directed and driven by their associated outcome. However, with repeated experience habitual actions develop which are automated and efficient, as they are instead driven by antecedent stimuli. Dopamine is thought to facilitate the transition from goal-directed to habitual actions. This idea has been largely derived from evidence that psychostimulants accelerate the development of habitual actions. In the current study, we examined the impact of L-dopa (levodopa or L-dihydroxyphenylalanine), which also potentiates dopamine activity, on habitual learning. L-dopa was systemically administered prior to training rats to press a lever for a food outcome. When tested, L-dopa exposed animals were insensitive to changes in the value of the food outcome, and hence demonstrated accelerated habitual behavioral control compared to control animals that remained goal directed. We also showed that when N-acetylcysteine (NAC), an antioxidant and regulator of glutamate activity, was co-administered with L-dopa, it prevented the transition to habitual behavior; an effect demonstrated previously for cocaine. Therefore, this study establishes similarities between L-dopa and psychostimulants in both the development and prevention of habitual actions, and supports the notion that excess dopamine potentiates habitual learning. This finding extends the limited existing knowledge of the impact of L-dopa on learning and behavior, and has implications for neurological disorders where L-dopa is the primary treatment.
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Affiliation(s)
- Anne S Gibson
- Department of Pharmacology and Toxicology, University of Utah, Salt Lake City, UT, USA; Interdepartmental Program in Neuroscience, University of Utah, Salt Lake City, UT, USA
| | - Kristen A Keefe
- Department of Pharmacology and Toxicology, University of Utah, Salt Lake City, UT, USA; Interdepartmental Program in Neuroscience, University of Utah, Salt Lake City, UT, USA
| | - Teri M Furlong
- Department of Pharmacology and Toxicology, University of Utah, Salt Lake City, UT, USA; Neuroscience Research Australia, 139 Barker Street, Randwick, NSW, Australia; School of Medical Sciences, University of New South Wales, Kensington, NSW, Australia.
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Schüller T, Fischer AG, Gruendler TOJ, Baldermann JC, Huys D, Ullsperger M, Kuhn J. Decreased transfer of value to action in Tourette syndrome. Cortex 2020; 126:39-48. [PMID: 32062469 DOI: 10.1016/j.cortex.2019.12.027] [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: 05/22/2019] [Revised: 09/13/2019] [Accepted: 12/26/2019] [Indexed: 11/30/2022]
Abstract
OBJECTIVE Tourette syndrome is a neurodevelopmental disorder putatively associated with a hyperdopaminergic state. Therefore, it seems plausible that excessive dopamine transmission in Tourette syndrome alters the ability to learn based on rewards and punishments. We tested whether Tourette syndrome patients exhibited altered reinforcement learning and corresponding feedback-related EEG deflections. METHODS We used a reinforcement learning task providing factual and counterfactual feedback in a sample of 15 Tourette syndrome patients and matched healthy controls whilst recording EEG. The paradigm presented various reward probabilities to enforce adaptive adjustments. We employed a computational model to derive estimates of the prediction error, which we used for single-trial regression analysis of the EEG data. RESULTS We found that Tourette syndrome patients showed increased choice stochasticity compared to controls. The feedback-related negativity represented an axiomatic prediction error for factual feedback and did not differ between groups. We observed attenuated P3a modulation specifically for factual feedback in Tourette syndrome patients, representing impaired coding of attention allocation. CONCLUSION Our findings indicate that cortical prediction error coding is unaffected by Tourette syndrome. Nonetheless, the transfer of learned values into choice formation is degraded, in line with a hyperdopaminergic state.
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Affiliation(s)
- Thomas Schüller
- University of Cologne, Faculty of Medicine and University Hospital Cologne, Department of Psychiatry and Psychotherapy, Cologne, Germany.
| | - Adrian G Fischer
- Otto von Guericke University, Center for Behavioral Brain Sciences, Magdeburg, Germany; Freie Universität Berlin, Center for Cognitive Neuroscience, Berlin, Germany
| | - Theo O J Gruendler
- Otto von Guericke University, Center for Behavioral Brain Sciences, Magdeburg, Germany
| | - Juan Carlos Baldermann
- University of Cologne, Faculty of Medicine and University Hospital Cologne, Department of Psychiatry and Psychotherapy, Cologne, Germany
| | - Daniel Huys
- University of Cologne, Faculty of Medicine and University Hospital Cologne, Department of Psychiatry and Psychotherapy, Cologne, Germany
| | - Markus Ullsperger
- Otto von Guericke University, Center for Behavioral Brain Sciences, Magdeburg, Germany; Otto von Guericke University, Institute of Psychology, Magdeburg, Germany
| | - Jens Kuhn
- University of Cologne, Faculty of Medicine and University Hospital Cologne, Department of Psychiatry and Psychotherapy, Cologne, Germany; Johanniter Hospital Oberhausen, Department of Psychiatry, Psychotherapy and Psychosomatic, Oberhausen, Germany
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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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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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10
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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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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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