Hippocampal neural representational dynamics: differential effects of visual information on place field directionality, position, and size

Stored hippocampal spatial maps differ substantially from ones the hippocampus creates on initial acquaintance with a new environment. During the first few laps on a new maze, spatially tuned hippocampal ‘place cells’ develop an experience-dependent direction specificity and a backward shift of the place field centre of mass, normally associated with place field expansion. In this work, we used reliance on visual cues as a tool to test the putative functions and mechanisms of these three adjustments. We found that place field directionality was not affected by the availability of visual cues and therefore is not a primary mechanism to associate spatial and nonspatial information, as was previously hypothesized. Contrary to expectations, however, the place field expansion and backward shift appeared to be two distinct, independent phenomena with different reliance on visual cues. We propose new mechanisms for the observed phenomena taking into account their reliance on visual cues