Specifying 'where' and 'what' is critical for testing hippocampal contributions to memory retrieval

Abstract

Tallman and colleagues' review of consolidation studies found that the length of the delay between 'recent' and 'remote' events is an influential determinant of detecting temporally graded hippocampal activity. Here, we discuss two additional factors - separate analysis of distinct regions within the hippocampus and the use of overt recall methods - that should be considered when testing competing theories of hippocampal contributions to memory.

Keywords: Consolidation; hippocampus; memory; recall.

Figure 1.

Activity in the hippocampus during autobiographical recall dissociates as a function of hippocampal subregion and temporal distance. A) Participant-specific anterior and posterior hippocampal subregions were segmented using the uncal apex as a landmark. B) We reported three main findings. 1. In the anterior region of the hippocampus there was no temporal gradient and no neural activity above our baseline control condition except for the 6-18 month period in the right hemisphere. 2. In the posterior region of the hippocampus there was a temporal gradient in both the left and right hemispheres. 3. The posterior region of the hippocampus was active for the earliest and 6-18 month time periods in both hemispheres, but not during recall from the most distant time period (5-10 years ago) (see Gilmore et al., 2021 for details). * denotes p < .05; ‡ denotes significant one-sample test vs. a baseline task, (p < .05, corrected for multiple comparisons); HC: hippocampus. Figure adapted from Gilmore et al. (2021).