Figure 4.

Caudate Nucleus: Dopamine and Serotonin Signaling Tracks Experienced Trial Type Transitions

(A) Illustration of experienced task statistics for participant 4. Horizontal bars show the probability of encountering each trial type on trial t after having encountered the trial type defined by high coherence and low distance on trial t-1. The trial type transition probabilities, P(type_t|type_t-1), were computed as the normalized counts of the number of times each trial type succeeded a given trial type. The expected value of P(type_t|type_t-1) under randomization is 0.25. The least likely trial type transition is indicated by green color in (A) and (B).

(B) Correlation between neuromodulatory responses and trial type transition probabilities in participant 4. To compute the neuromodulatory responses, we first averaged time points across a window from 0 s to 1.5 s (the period during which a trial type is revealed) within each trial and then averaged across all trials for each trial type transition. Time series were locked to the onset of the motion stimulus, spanning a period from 1 s before stimulus onset to 5 s after stimulus onset, and Z scored separately for each trial. For comparison between dopamine and serotonin, data points are colored according to the associated trial type transition probability. Lines are best-fitting lines from a linear regression. Top right-hand corner indicates participant number and disease state (PD: Parkinson’s disease; ET: essential tremor). DA: dopamine. 5-HT: serotonin.