Housing-dependent variation in goal-tracking behavior predicts use of a spatial strategy in a dual-solution Morris water maze task

Abstract

Pavlovian Lever Autoshaping (PLA) is a common method for assessing individual differences in addiction vulnerability, while the Morris water maze (MWM) dual solution task may hold promise as a complimentary behavioral assay. In this procedure, brief lever insertion predicts delivery of a food pellet, non-contingent upon behavior. Sign-trackers preferentially interact with the lever, while goal-trackers preferentially interact with the foodcup. To enhance motivation, rats commonly undergo mild food restriction requiring isolation housing—stressful living conditions for a social species. The present work examines the contribution of housing conditions to performance in PLA and a MWM dual solution task. Male and female rats are assigned to one of three housing conditions at weaning: Enriched (four rats per large cage with enrichment objects), Single (singly-housed standard cage with no enrichment), and Raised Enriched (raised under Enriched conditions, but transitioned to Single conditions at eight weeks). Housing conditions influence PLA performance in a sex-dependent manner. Overall, enriched rats engage in more goal-directed behavior while Single and Raised Enriched rats engage in more cue-directed behavior; this pattern is driven by male rats. Additionally, goal-trackers favor a flexible “place” strategy in the MWM. Results suggest that measures of individual differences in goal- vs. cue-directed behavior are highly sensitive to housing conditions; this sensitivity is greater in males.