Immediate response strategy and shift to place strategy in submerged T-maze.

Abstract

A considerable amount of research has demonstrated that animals can use different strategies when learning about, and navigating within, their environment. Since the influential research of Packard and McGaugh (1996), it has been widely accepted that, early in learning, rats use a flexible dorsal hippocampal-dependent place strategy. As learning progresses, they switch to a less effortful and more automatic dorsolateral caudate-dependent response strategy. However, supporting literature is dominated by the use of appetitively motivated tasks, using food reward. Because motivation often plays a crucial role in guiding learning, memory, and behavior, we examined spatial learning strategies of rats in an escape-motivated submerged T-maze. In Experiment 1, we observed rapid learning and the opposite pattern as that reported in appetitively motivated tasks. Rats exhibited a response strategy early in learning before switching to a place strategy, which persisted over extensive training. In Experiment 2, we replicated Packard and McGaugh's (1996) observations, using the apparatus and procedures as in Experiment 1, but with food reward instead of water escape. Mechanisms for, and implications of, this motivational modulation of spatial learning strategy are considered.

Dorsolateral striatum implicated in the acquisition, but not expression, of immediate response learning in rodent submerged T-maze

“…Across the interspersed probe tests, we observed the behavioral pattern expected on the basis of Asem and Holland’s (2013) findings, with rats switching from response learning to place learning. However, this pattern was not affected by lidocaine infusions.…”

“…However, in the submerged T-maze, we observed the opposite behavioral pattern—rats initially used a response strategy and gradually switched to a place strategy (Asem & Holland, 2013). Due to a complete inversion of previous behavioral results, the underlying neural circuitry and the characterization of strategy shifts over training in the submerged T-maze warrants investigation.…”

“…However, as learning progresses, rats switch to an automatic, striatal-dependent response strategy (Packard & McGaugh, 1996). Interestingly, in a similar but aversively motivating water-submerged T-maze, rats exhibit the opposite behavioral pattern, initially adopting a response strategy but switching to a place strategy with extended training (Asem & Holland, 2013). Here, we examined the effects of transient lidocaine inactivation of the dorsolateral striatum (DLS) on rats’ acquisition and expression of place and response strategies in the submerged T-maze.…”

“…These differing types of learning have been thoroughly investigated in the field of spatial navigation as “place” and “response” strategies; the place strategy has been discussed as relational and spatial learning, whereas the response strategy as being symptomatic of S-R and habit learning. For example, in the “dual-solution” maze paradigm, rats are trained to find either a food reward or an escape platform in one arm of a dry or submerged T-maze, respectively (Tolman & Gleitman, 1949; Tolman, Ritchie, & Kalish, 1946; Asem & Holland, 2013). The animal can solve the task by employing either a place or response strategy, the relative usage of each assessed by interspersed one-trial probe tests (see Asem & Holland, 2013, for details).…”

Lesions of the hippocampus or dorsolateral striatum disrupt distinct aspects of spatial navigation strategies based on proximal and distal information in a cued variant of the Morris water task

“…Prior research reports have noted differences in shifts in navigation strategy and disruption of behavior as a result of disorientation between dry land and water tasks. One recent study using a T maze found that rats demonstrated an initial response strategy that shifted to place navigation after multiple days of training [23], in contrast to findings in the MWT [22]. Other reports have noted that disorienting rats by rotating holding cages prior to training resulted in impaired navigation in a radial arm maze, but not the MWT [24, 25], even when the task was simplified by using a T maze [26].…”