The role of the basal ganglia in learning and memory: insight from Parkinson's disease

Abstract

It has long been known that memory is not a single process. Rather, there are different kinds of memory that are supported by distinct neural systems. This idea stemmed from early findings of dissociable patterns of memory impairments in patients with selective damage to different brain regions. These studies highlighted the role of the basal ganglia in non-declarative memory, such as procedural or habit learning, contrasting it with the known role of the medial temporal lobes in declarative memory. In recent years, major advances across multiple areas of neuroscience have revealed an important role for the basal ganglia in motivation and decision making. These findings have led to new discoveries about the role of the basal ganglia in learning and highlighted the essential role of dopamine in specific forms of learning. Here we review these recent advances with an emphasis on novel discoveries from studies of learning in patients with Parkinson's disease. We discuss how these findings promote the development of current theories away from accounts that emphasize the verbalizability of the contents of memory and towards a focus on the specific computations carried out by distinct brain regions. Finally, we discuss new challenges that arise in the face of accumulating evidence for dynamic and interconnected memory systems that jointly contribute to learning.

Fig. 1

The “weather prediction” task is a popular probabilistic category learning task. (A) Each of 4 visual cues – cards with shapes – is independently and probabilistically associated with either “rain” or “sun”. (B) On each trial, a combination of one to three cards is shown. Subjects respond based on their prediction of the weather for that trial, and receive response-contingent feedback.

Fig. 2

Learning from immediate vs. delayed feedback (A). Examples of trials where feedback is provided immediately or after a 6-s delay. (B). Performance of Parkinson's disease patients and age-matched controls in a post-learning test phase where participants make the same choices as during learning but without receiving feedback. These results show how well each group has learned after training with feedback of different delays.