Distinct contributions of the nucleus reuniens, prefrontal cortex, and hippocampus to spatial working memory

Abstract

Memory is an abstract concept referring to stored representations of previous experience that may prove relevant to future behavior. Working memory refers to the process by which those representations are put to use in a given context, with a necessary temporal component. Spatial working memory (SWM), in particular, refers to those working memory activities occurring within the context of spatial navigation behaviors. The process requires representations of learned experiences, current context, comparisons between the two, and rule-based decision making. Each of these has been previously shown to depend on some combination of three critical structures; the prefrontal cortex (PFC), the hippocampus (HC), and the midline thalamic nucleus reuniens (Re). However, it had not yet been demonstrated when during the SWM timeline the information flow across specific pathways linking the structures was necessary to support accurate goal-directed navigation. The current experiments use optogenetics to target pathway-specific activity during isolated portions of the SWM timeline. The results, suggesting high-degrees of selectivity to contributions necessary to SWM, are discussed within the context of how the brain supports the construction and application of critical neuronal representations for: learned experiences, current context, comparisons between the two, and rule-based decision making.