Tatter, S. B. | Search bioRxiv

bioRxiv2025

Striatal dopamine modulates reward-reinforced temporal learning in humans.

The neurobiological mechanisms underlying human time perception remain elusive. Evidence has consistently linked striatal dopamine to timing behaviors, but it is still uncertain how rapid changes in dopamine may modulate human time perception. Many tasks designed to measure time perception utilize instrumental conditioning paradigms that reinforce correctly timed intervals. In these tasks, subjects are shown to improve their performance following repeated presentations of temporal cues - a phenomenon known as temporal learning. We sought to determine the association between rapid changes in human dopamine levels and temporal learning on an interval timing task that tested the reproduction of 1000ms, 3000ms, and 5000ms intervals in the presence and absence of monetary reinforcement. We utilized human voltammetry to measure real-time dopamine concentrations from the striatum of patients with Parkinsons disease while they performed the interval timing task. We first compared task behavior between patients with Parkinsons disease and neurologically healthy controls and found significant differences in the reproduction of 1000ms intervals, but not 3000ms or 5000ms intervals of time. Further, we observed that during 1000ms intervals, increases in striatal dopamine concentrations were associated with increases in temporal errors, but only during the expectation of monetary reinforcement. We also demonstrated that as temporal errors decrease overtime during temporal learning, so do striatal dopamine concentrations. These results suggest that dopamine may be driving temporal learning through the generation of temporal errors in response to positive reinforcement. These findings may have significant implications in our understanding of the role that dopamine plays in time perception. Significance StatementHuman time perception is a fundamental cognitive ability but the interaction between how the human brain perceives time and dopamines role is unclear. This study is the first of its kind to apply human voltammetry to measure rapid changes in dopamine levels associated with temporal learning in the presence and absence of positive reinforcement. We demonstrate that temporal learning may be affected by moment-to-moment changes in dopamine levels, which are also counterintuitively related to the generation of temporal errors in the presence of expectations of rewarding feedback.

neuroscience↗

bioRxiv2023

Sub-second Dopamine Signals during Risky Decision-Making in Patients with Impulse Control Disorder

BackgroundImpulse Control Disorder (ICD) in Parkinsons disease is a behavioral addiction arising secondary to dopaminergic therapies, most often dopamine receptor agonists. Prior research implicates changes in striatal function and heightened dopaminergic activity in the dorsal striatum of patients with ICD. However, this prior work does not possess the temporal resolution required to investigate dopaminergic signaling during real-time progression through various stages of decision-making involving anticipation and feedback. MethodsWe recorded high-frequency (10Hz) measurements of extracellular dopamine in the striatum of patients with (N=3) and without (N=3) a history of ICD secondary to dopamine receptor agonist therapy for Parkinsons disease symptoms. These measurements were made using carbon fiber microelectrodes during awake DBS neurosurgery and while participants performed a sequential decision-making task involving risky investment decisions and real monetary gains and losses. Per clinical standard-of-care, participants withheld all dopaminergic medications prior to the procedure. ResultsPatients with ICD invested significantly more money than patients without ICD. On each trial, patients with ICD made smaller adjustments to their investment levels compared to patients without ICD. In patients with ICD, dopamine levels rose or fell on sub-second timescales in anticipation of investment outcomes consistent with increased or decreased confidence in a positive outcome, respectively; dopamine levels in patients without ICD were significantly more stable during this phase. After outcome revelation, dopamine levels in patients with ICD rose significantly more than in inpatients without ICD for better-than-expected gains. For worse-than-expected losses, dopamine levels in patients with ICD remained level whereas dopamine levels in patients without ICD fell. ConclusionWe report significantly increased risky behavior and exacerbated phasic dopamine signaling, on sub-second timescales, anticipating and following the revelation of the outcomes of risky decisions in patients with ICD. Notably, these results were obtained when patients who had demonstrated ICD in the past but were, at the time of surgery, in an off-medication state. Thus, it is unclear whether observed signals reflect an inherent predisposition for ICD that was revealed when dopamine receptor agonists were introduced or whether these observations were caused by the introduction of dopamine receptor agonists and the patients having experienced ICD symptoms in the past. Regardless, future work investigating dopamines role in human cognition, behavior, and disease should consider the signals this system generates on sub-second timescales.

neuroscience↗