The hippocampus is critical for value-based decisions guided by dissociative inference

Area of Science:

• Neuroscience
• Cognitive Science
• Animal Behavior

Background:

• The hippocampus is vital for flexible decision-making, enabling memory integration and associative inference.
• Flexible representations of stimulus relationships within and between episodes are key for memory integration.

Purpose of the Study:

• To investigate if the hippocampus is necessary for dissociative inference: parsing experienced episodes into constituents to infer re-combined within-episode associations.
• To determine the role of the hippocampus in allocating value from primary rewards to individual stimuli.

Main Methods:

• Male rats were trained on an appetitive conditioning task with compound auditory stimuli (e.g., AB+, BA+, CD-, DC-).
• Experiments involved testing rats with hippocampal lesions and control groups on compound and individual stimuli.
• The study examined whether rats could infer the value of individual stimuli based on their prior association with compound stimuli.

Main Results:

• Rats with hippocampal lesions acquired and retained compound discriminations similarly to controls.
• Unlike controls, hippocampal rats failed to infer the associated values of single constituent stimuli, treating them as familiar but unvalued.
• This deficit was observed regardless of whether hippocampal lesions occurred before or after compound training, suggesting retrieval-based deficits.

Conclusions:

• The hippocampus is critical for dissociative inference, enabling the parsing of learned associations into constituent parts.
• Hippocampal function is essential for allocating associative value to individual stimuli, extending its known role in memory and decision-making.
• Dissociative inference, supported by the hippocampus, is fundamental for restructuring memories to adapt to changing environments and extract relevant information.