Age-related impairments in visual recall depend on what you are remembering

The hippocampus is one of the first brain regions to deteriorate with age, and these changes have been linked to the decline in declarative memory frequently observed in older adults. There exist several process-based accounts of the effects of hippocampal damage on memory, such as impairments in context-specific memory with spared gist-based memory, or deficits in recollection alongside intact familiarity-based retrieval. In contrast, representational accounts claim that hippocampal involvement depends on the content of the memory-high-dimensional, containing arbitrary associations (e.g., scenes) versus lower-dimensional, single-items (e.g., objects). Thus, representational theories uniquely predict that aging should differentially impair retrieval depending on the memory content (high-versus lower-dimensional) when the retrieval process is held constant. However, testing this prediction is difficult because most recall or recognition tasks draw upon arbitrary associations, which are high-dimensional, even if the memoranda are single items (e.g., Did this item appear in the study context? Which item was paired with this cue?). We tested memory in younger and older adults in a visual recall task that circumvents this problem by cueing memory with a partial "patch view" of a studied item, analogous to word-stem completion. Thus, the newly learned associations needed for good retrieval were not arbitrary but rather linked parts of a coherent image. For scenes, such cued retrieval required item-to-item associations, but for objects it involved intra-item associations. Older adults were impaired relative to younger, for patch-cued recall of scenes but not objects. Given hippocampal deterioration with age, this supports representational accounts of memory.