Anterior thalamic function is required for spatial coding in the subiculum and is necessary for spatial memory

Abstract

SummaryHippocampal function relies on the anterior thalamic nuclei, but the reasons remain poorly understood. While anterior thalamic lesions disrupt parahippocampal spatial signalling, their impact on the subiculum is unknown, despite the importance of this area for hippocampal networks. We recorded subicular cells in rats with either permanent (N-methyl-D-aspartic acid) or reversible (muscimol) anterior thalamic lesions. Bayesian and other statistical analyses underscored the notable absence of the diverse spatial signals normally found in the subiculum, including place cells, following permanent anterior thalamic lesions. Likewise, there was marked disruption of these diverse spatial signals during transient lesions. By contrast, permanent anterior thalamic lesions had no discernible impact on CA1 place fields. Anterior thalamic lesions reduced spatial alternation performance (permanently or reversibly) to chance, while leaving a non-spatial recognition memory task unaffected. These findings, which help explain why anterior thalamic damage is so deleterious for spatial memory, cast a new spotlight on the importance of subiculum function and reveal its dependence on anterior thalamic signalling.Graphical Abstract