# Distinct basal ganglia contributions to learning from implicit and explicit value signals in perceptual decision-making

## TL;DR

The study shows how the brain uses both confidence and explicit feedback to improve decision-making, with distinct brain regions handling each type of signal.

## Contribution

The paper uniquely identifies neural signatures of implicit and explicit feedback in the basal ganglia using EEG-fMRI fusion.

## Key findings

- Neural signatures of post-decision confidence re-emerge during feedback processing.
- Implicit and explicit feedback signals are mapped along a dorsal-ventral striatum gradient.
- The external globus pallidus integrates these signals to enhance perceptual learning.

## Abstract

Metacognitive evaluations of confidence provide an estimate of decision accuracy that could guide learning in the absence of explicit feedback. We examine how humans might learn from this implicit feedback in direct comparison with that of explicit feedback, using simultaneous EEG-fMRI. Participants performed a motion direction discrimination task where stimulus difficulty was increased to maintain performance, with intermixed explicit- and no-feedback trials. We isolate single-trial estimates of post-decision confidence using EEG decoding, and find these neural signatures re-emerge at the time of feedback together with separable signatures of explicit feedback. We identified these signatures of implicit versus explicit feedback along a dorsal-ventral gradient in the striatum, a finding uniquely enabled by an EEG-fMRI fusion. These two signals appear to integrate into an aggregate representation in the external globus pallidus, which could broadcast updates to improve cortical decision processing via the thalamus and insular cortex, irrespective of the source of feedback.

Confidence could act as an implicit learning signal when explicit feedback is unavailable. The authors show confidence can also provide a distinct value signal in the presence of explicit feedback, both of which are integrated to drive perceptual learning via basal ganglia circuits.