Impaired inference in a case of developmental amnesia

Abstract

Amnesia is associated with impairments in relational memory, which is critically supported by the hippocampus. By adapting the transitivity paradigm, we previously showed that age‐related impairments in inference were mitigated when judgments could be predicated on known pairwise relations, however, such advantages were not observed in the adult‐onset amnesic case D.A. Here, we replicate and extend this finding in a developmental amnesic case (N.C.), who also shows impaired relational learning and transitive expression. Unlike D.A., N.C.'s damage affected the extended hippocampal system and diencephalic structures, and does not extend to neocortical areas that are affected in D.A. Critically, despite their differences in etiology and affected structures, N.C. and D.A. perform similarly on the task. N.C. showed intact pairwise knowledge, suggesting that he is able to use existing semantic information, but this semantic knowledge was insufficient to support transitive expression. The present results suggest a critical role for regions connected to the hippocampus and/or medial prefrontal cortex in inference beyond learning of pairwise relations. © 2016 The Authors Hippocampus Published by Wiley Periodicals, Inc.

The hippocampus is critical for value‐based decisions guided by dissociative inference

“…Other examples of flexible use of information include acquired equivalence (Coutureau et al, ; Myers et al, ; Winocur & Salzen, ) and transitive inference (D'Angelo et al, ; Dusek & Eichenbaum, ; Ryan et al, ) where relationships are derived between disparate stimuli that were not previously presented together. These cognitive processes, dissociative inference among them, differ in substantive ways from one another, including whether they are more likely to occur at encoding or retrieval, but they are similar to the extent that they require inferential processing and the re‐organization of information.…”

“…The hippocampus is involved in inferential processing by virtue of the relational representations it forms (D'Angelo, Rosenbaum, & Ryan, ; Dusek & Eichenbaum, ; Frank, Rudy, & O'Reilly, ; Greene, Gross, Elsinger, & Rao, ; Schlichting, Zeithamova, & Preston, ). For example, animals with hippocampal lesions are impaired on tests of associative inference in which a relationship is formed between two stimuli that have never been co‐presented (e.g., AC) because of their previously overlapping association with a third stimulus (e.g., AB, BC).…”

Larger capacity for unconscious versus conscious episodic memory

“…Findings indicate that drawing inferences by forming associations indirectly (not based on sensory input) requires both episodic memory and working memory. [9][10][11][12][13][14][15] Here, we probe the formation and delayed retrieval of inferences to assess the role of consciousness in episodic memory and working memory.…”

Superior explicit memory despite severe developmental amnesia: In‐depth case study and neural correlates

“…First, the conclusion of preserved semantic learning is usually based on the results of tests measuring academic achievement or general knowledge, such as the Information, Vocabulary and Comprehension subtests of the Wechsler Adult Intelligence Scale (WAIS; Bindschaedler et al, ; Brizzolara et al, ; D'Angelo, Rosenbaum, & Ryan, ; Gadian et al, 2001; Martins et al, ; Picard et al, ; Rosenbaum et al, ; Vargha‐Khadem et al, , ). It should be noted that more thorough assessments of semantic knowledge always elicit performances in the low‐to‐normal range (Bindschaedler et al, ; Brizzolara et al, ; Martins et al, ) or, in some cases, impaired performances (e.g., Patient KF, Martins et al, ; Patient CL, Vicari et al, ; Patient Jocelyn, Picard et al, ).…”

“…However, just because some patients with DA perform the Vocabulary or Information subtest of the WAIS correctly does not mean that they have normal semantic memory. Recent findings suggest that their semantic knowledge structure differs from that of healthy individuals (Blumenthal et al, ; D'Angelo et al, ; Patient HC). There is also the question of whether these patients acquire new semantic knowledge in a similar way to healthy individuals, with available evidence suggesting that they do so at a slower pace (e.g., Gardiner et al, ; Martins et al, ).…”