Structural features of the hippocampus covary with memory-guided attention depending on the side of hippocampal sclerosis

: Past experiences stored in long-term memory (LTM) provide a valuable resource for making predictions that shape perception and guide goal-directed behavior. Contents from the high-capacity LTM system guide contextual selective attention to enhance sensory and higher-order processing of memory-predicted targets, in a process known as LTM-guided attention. While this essential cognitive function is believed to depend on the hippocampus, evidence is still scarce. In this study, we used a neuropsychological approach to test LTM-guided attention in the context of isolated hippocampal pathology and to explore structure-behavior covariance patterns. We tested healthy individuals (n = 20) and individuals suffering from focal epilepsy, with isolated, unilateral left (n = 20) or right (n = 17) hippocampal sclerosis (HS), in a task probing LTM-guided attention. Behavioral data indicated that individuals with left or right HS retained LTM-guided attention. We also assessed structure-behavior covariance using a multivariate structural neuroimaging approach. Hierarchical clustering analysis revealed that, in healthy individuals, LTM-guided attention performance covaried with atlas-derived subfield measures of the left hippocampal body. The volume of the left hippocampal body also covaried with attentional benefit in individuals with right HS. Interestingly, for individuals with left HS, LTM-guided attention covaried with the volume of the left hippocampus and with part of the right hippocampal volume. Together, these findings suggest that LTM-guided attention can be preserved in unilateral HS, with differences in hippocampal volume-behavior covariance depending on the side of hippocampal pathology.