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Reward sensitivity deficits modulated by dopamine are associated with apathy in Parkinson ’ s disease

View Article: PubMed Central - PubMed

ABSTRACT

Apathy is extremely common in neurodegenerative disorders such as Parkinson’s disease. Muhammed et al. report that lack of sensitivity to rewards may underlie apathy, with dopamine playing a modulatory role. The study provides a basis for objective clinical markers of motivation and treatment efficacy in neurodegenerative conditions.

No MeSH data available.


Related in: MedlinePlus

Pupillary reward sensitivity in apathetic versus non-apathetic Parkinson’s disease patients, ON/OFF dopamine and elderly age-matched controls. (A) OFF state. Mean pupil reward sensitivity (50p pupil change minus 0p pupil change) plotted over time between apathetic Parkinson’s disease patients (cyan) and non-apathetic Parkinson’s disease patients (green) when OFF dopamine or drug-naïve. A significant difference in sensitivity occurred from ∼1000 ms to the end of the trial, indicated by light purple bar (P < 0.05). There was also a significant time period where apathetic patients had reduced reward sensitivity compared to elderly controls, indicated by light red bar. (B) ON State. Mean pupil reward sensitivity (50p pupil change minus 0p pupil change) plotted over time between apathetic Parkinson’s disease patients (cyan) and non-apathetic Parkinson’s disease patients (green). A significant difference in sensitivity occurred from ∼1100 ms to the end of the trial, indicated by light purple bar (P < 0.05). There was also a significant time period where non-apathetic patients ON dopamine had increased reward sensitivity compared to elderly controls, indicated by grey bar.
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aww188-F5: Pupillary reward sensitivity in apathetic versus non-apathetic Parkinson’s disease patients, ON/OFF dopamine and elderly age-matched controls. (A) OFF state. Mean pupil reward sensitivity (50p pupil change minus 0p pupil change) plotted over time between apathetic Parkinson’s disease patients (cyan) and non-apathetic Parkinson’s disease patients (green) when OFF dopamine or drug-naïve. A significant difference in sensitivity occurred from ∼1000 ms to the end of the trial, indicated by light purple bar (P < 0.05). There was also a significant time period where apathetic patients had reduced reward sensitivity compared to elderly controls, indicated by light red bar. (B) ON State. Mean pupil reward sensitivity (50p pupil change minus 0p pupil change) plotted over time between apathetic Parkinson’s disease patients (cyan) and non-apathetic Parkinson’s disease patients (green). A significant difference in sensitivity occurred from ∼1100 ms to the end of the trial, indicated by light purple bar (P < 0.05). There was also a significant time period where non-apathetic patients ON dopamine had increased reward sensitivity compared to elderly controls, indicated by grey bar.

Mentions: These findings were also reflected in the time course of pupillary reward sensitivity as measured using multiple permutation testing to account for multiple comparison bias, with differences in pupillary response over time performed at each millisecond (Fig. 5). When OFF dopamine, apathetic Parkinson’s disease patients had significantly less reward sensitivity compared to non-apathetic patients from ∼1000 ms to the end of each trial (Fig. 5A). They also showed some significant reduced reward sensitivity over time compared to elderly controls, but no differences were apparent between non-apathetic and elderly participants.Figure 5


Reward sensitivity deficits modulated by dopamine are associated with apathy in Parkinson ’ s disease
Pupillary reward sensitivity in apathetic versus non-apathetic Parkinson’s disease patients, ON/OFF dopamine and elderly age-matched controls. (A) OFF state. Mean pupil reward sensitivity (50p pupil change minus 0p pupil change) plotted over time between apathetic Parkinson’s disease patients (cyan) and non-apathetic Parkinson’s disease patients (green) when OFF dopamine or drug-naïve. A significant difference in sensitivity occurred from ∼1000 ms to the end of the trial, indicated by light purple bar (P < 0.05). There was also a significant time period where apathetic patients had reduced reward sensitivity compared to elderly controls, indicated by light red bar. (B) ON State. Mean pupil reward sensitivity (50p pupil change minus 0p pupil change) plotted over time between apathetic Parkinson’s disease patients (cyan) and non-apathetic Parkinson’s disease patients (green). A significant difference in sensitivity occurred from ∼1100 ms to the end of the trial, indicated by light purple bar (P < 0.05). There was also a significant time period where non-apathetic patients ON dopamine had increased reward sensitivity compared to elderly controls, indicated by grey bar.
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Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC5035817&req=5

aww188-F5: Pupillary reward sensitivity in apathetic versus non-apathetic Parkinson’s disease patients, ON/OFF dopamine and elderly age-matched controls. (A) OFF state. Mean pupil reward sensitivity (50p pupil change minus 0p pupil change) plotted over time between apathetic Parkinson’s disease patients (cyan) and non-apathetic Parkinson’s disease patients (green) when OFF dopamine or drug-naïve. A significant difference in sensitivity occurred from ∼1000 ms to the end of the trial, indicated by light purple bar (P < 0.05). There was also a significant time period where apathetic patients had reduced reward sensitivity compared to elderly controls, indicated by light red bar. (B) ON State. Mean pupil reward sensitivity (50p pupil change minus 0p pupil change) plotted over time between apathetic Parkinson’s disease patients (cyan) and non-apathetic Parkinson’s disease patients (green). A significant difference in sensitivity occurred from ∼1100 ms to the end of the trial, indicated by light purple bar (P < 0.05). There was also a significant time period where non-apathetic patients ON dopamine had increased reward sensitivity compared to elderly controls, indicated by grey bar.
Mentions: These findings were also reflected in the time course of pupillary reward sensitivity as measured using multiple permutation testing to account for multiple comparison bias, with differences in pupillary response over time performed at each millisecond (Fig. 5). When OFF dopamine, apathetic Parkinson’s disease patients had significantly less reward sensitivity compared to non-apathetic patients from ∼1000 ms to the end of each trial (Fig. 5A). They also showed some significant reduced reward sensitivity over time compared to elderly controls, but no differences were apparent between non-apathetic and elderly participants.Figure 5

View Article: PubMed Central - PubMed

ABSTRACT

Apathy is extremely common in neurodegenerative disorders such as Parkinson&rsquo;s disease. Muhammed et al. report that lack of sensitivity to rewards may underlie apathy, with dopamine playing a modulatory role. The study provides a basis for objective clinical markers of motivation and treatment efficacy in neurodegenerative conditions.

No MeSH data available.


Related in: MedlinePlus