A Neostriatal Habit Learning System in Humans

TLDR

The human neostriatum, comprising the caudate nucleus and putamen, is crucial for gradual, incremental habit learning and for acquiring nonmotor dispositions that depend on new associations. The study employed a probabilistic classification task in which amnesic and nondemented Parkinson’s disease patients learned which outcome would occur for each cue combination. Amnesic patients learned the task normally but had severe declarative memory deficits, whereas Parkinson’s patients failed to learn despite intact memory, demonstrating a double dissociation that the limbic‑diencephalic system and the neostriatum support separate, parallel learning systems.

Abstract

Amnesic patients and nondemented patients with Parkinson's disease were given a probabilistic classification task in which they learned which of two outcomes would occur on each trial, given the particular combination of cues that appeared. Amnesic patients exhibited normal learning of the task but had severely impaired declarative memory for the training episode. In contrast, patients with Parkinson's disease failed to learn the probabilistic classification task, despite having intact memory for the training episode. This double dissociation shows that the limbic-diencephalic regions damaged in amnesia and the neostriatum damaged in Parkinson's disease support separate and parallel learning systems. In humans, the neostriatum (caudate nucleus and putamen) is essential for the gradual, incremental learning of associations that is characteristic of habit learning. The neostriatum is important not just for motor behavior and motor learning but also for acquiring nonmotor dispositions and tendencies that depend on new associations.