Hierarchical and binary associations compete for behavioral control during instrumental biconditional discrimination

Area of Science:

• Neuroscience
• Behavioral Neuroscience
• Animal Cognition

Background:

• Instrumental discrimination learning involves stimulus-response (S-R) associations.
• Hierarchical stimulus-outcome (S-O) and response-outcome (R-O) associations may also play a role.
• The striatum is implicated in different forms of associative learning.

Purpose of the Study:

• To investigate the role of hierarchical stimulus-(response-outcome) [S-(R-O)] associations versus associative alternatives in biconditional discrimination learning in rats.
• To differentiate the roles of the dorsomedial striatum (DMS) and dorsolateral striatum (DLS) in S-(R-O) and S-R learning, respectively.

Main Methods:

• Two experiments using male rats with selective lesions of the posterior DMS or DLS.
• Experiment 1: Standard biconditional discrimination task.
• Experiment 2: More challenging discrimination protocol.

Main Results:

• Lesions of the posterior DMS, which impair R-O associative learning, abolished biconditional discrimination.
• Lesions of the DLS, which impair S-R learning, did not abolish biconditional discrimination in Experiment 1.
• DLS lesions enhanced biconditional discrimination learning in Experiment 2.

Conclusions:

• Hierarchical S-(R-O) associations, mediated by the DMS, are critical for solving biconditional discrimination problems.
• S-R associations, mediated by the DLS, are less important and may even compete with S-(R-O) associations for behavioral control.
• These findings highlight the importance of hierarchical associations in instrumental learning and decision-making.