Relational learning and transitive expression in aging and amnesia

Abstract

Aging has been associated with a decline in relational memory, which is critically supported by the hippocampus. By adapting the transitivity paradigm (Bunsey and Eichenbaum (1996) Nature 379:255‐257), which traditionally has been used in nonhuman animal research, this work examined the extent to which aging is accompanied by deficits in relational learning and flexible expression of relational information. Older adults' performance was additionally contrasted with that of amnesic case DA to understand the critical contributions of the medial temporal lobe, and specifically, the hippocampus, which endures structural and functional changes in healthy aging. Participants were required to select the correct choice item (B versus Y) based on the presented sample item (e.g., A). Pairwise relations must be learned (A‐>B, B‐>C, C‐>D) so that ultimately, the correct relations can be inferred when presented with a novel probe item (A‐>C?Z?). Participants completed four conditions of transitivity that varied in terms of the degree to which the stimuli and the relations among them were known pre‐experimentally. Younger adults, older adults, and DA performed similarly when the condition employed all pre‐experimentally known, semantic, relations. Older adults and DA were less accurate than younger adults when all to‐be‐learned relations were arbitrary. However, accuracy improved for older adults when they could use pre‐experimentally known pairwise relations to express understanding of arbitrary relations as indexed through inference judgments. DA could not learn arbitrary relations nor use existing knowledge to support novel inferences. These results suggest that while aging has often been associated with an emerging decline in hippocampal function, prior knowledge can be used to support novel inferences. However, in case DA, significant damage to the hippocampus likely impaired his ability to learn novel relations, while additional damage to ventromedial prefrontal and anterior temporal regions may have resulted in an inability to use prior knowledge to flexibly express indirect relational knowledge. © 2015 The Authors Hippocampus Published by Wiley Periodicals, Inc.

Impaired inference in a case of developmental amnesia

“…Given the predictions made by the fMRI work and our prior work with D.A. (Ryan et al, ), the present study examined whether D.A. 's impaired inference in the context of known pairwise relations would be replicated in a case of developmental amnesia, N.C. (D'Angelo et al, ).…”

“…Relational memory is a critical component of higher‐order cognitive functioning (Konkel et al, ; Moscovitch, ; Addis et al, ; Duff and Brown‐Schmidt, ; Cohen, ) and is sensitive to neurological disturbances and aging (Ryan et al, ; D'Angelo et al, in press). Relational memory impairments can lead to impairments in the ability to infer novel information indirectly from prior learning (Smith and Squire, ; Ryan et al, ). Impairments in the ability to make inferential judgments in novel situations have implications for social learning, as inference is a key component in problem solving and for guiding behavior in social interactions (Holyoak, ; Koscik and Tranel, ).…”

“…To examine the extent to which prior knowledge can be used to support inferential judgements in amnesia, we used a version of the transitivity task (Bunsey and Eichenbaum, ) adapted for use with humans (Ryan et al, ). In the transitivity task, participants are shown a sample stimulus (e.g., A) and two choice stimuli (e.g., B, X) and are asked to select the choice stimulus that “belongs” with the sample stimulus (e.g., A → B).…”

“…Using these conditions, we recently examined whether prior knowledge could support inferential judgments in older adults (Ryan et al, ), as older adults also show impairments on TP (Driscoll et al, ; Ostreicher et al, ) and TI (Ryan et al, ; Moses et al, ). Relative to younger adults, older adults showed impaired relational learning of premise pairs in the known items/arbitrary relations condition, but older adults had intact knowledge of relations that could be based on prior semantic knowledge (known items/pairwise relations condition).…”

“…Our prior study (Ryan et al, ) also examined whether prior knowledge could support inference in an amnesic case, D.A., who has bilateral damage to his medial temporal lobe (MTL), including the hippocampus, as well as damage to the right ventromedial prefrontal cortex (vmPFC) and right anterior temporal lobe (ATL) (Rosenbaum et al, ). Like the older adults, D.A.…”