Evidence of impaired naming in patients with hippocampal amnesia

Abstract

Object naming involves accessing meaning and retrieving the associated word form from remote semantic memory. Historically, previously acquired semantic knowledge (i.e., remote semantic memory) was thought to be independent of the hippocampus via neocortical consolidation. This view is based on evidence demonstrating a dissociation in behavior in patients with hippocampal amnesia: amnesic patients are impaired in acquiring new vocabulary yet can name and define previously acquired words. More recently, the view that remote semantic memory is hippocampusindependent has been challenged by the documentation of disruptions in aspects of remote semantic memory in patients with hippocampal amnesia, particularly in language use and depth of semantic knowledge. Based on these findings, we hypothesized that the hippocampus plays a long-term role in remote semantic memory. We tested amnesic patients and demographically matched healthy comparison participants in an extensive naming task using photographic images of objects normalized for familiarity, object agreement, and visual complexity. Amnesic patients were less likely to correctly name objects than healthy comparison participants. Further, amnesic patients' performance worsened for words that were less familiar, more visually complex, and had less object agreement. These findings suggest that the hippocampus may play a long-term role in semantic memory processes, rather than a timelimited role in the initial acquisition of semantic information, and that hippocampal damage can disrupt object naming.

Evidence of Impaired Remote Experience-near Semantic Memory in Medial Temporal Lobe Amnesia

“…In fact, in comparison to experience-far semantic memories, experience-near semantic memories are arguably more specific and richer in detail because they have spatiotemporal content. As such, it is possible that the present findings reflect an extension of prior research showing that individuals with medial temporal lobe lesions have difficulty generating specific details of remotely learned stories (Rosenbaum et al, 2009;Verfaellie et al, 2014), rich features and specific names of concepts (Hilverman & Duff, 2021;Klooster & Duff, 2015), context-related features of concepts (Blumenthal et al, 2017), or specific details of repeated events involving a spatiotemporal context (Lynch et al, 2020;St-Laurent et al, 2009). Future research could attempt to systematically vary spatiotemporal content, specificity, and total detail/richness of experience-near semantic memory as this could provide clarity as to which mechanism(s) might be in play.…”

“…familiar concepts (Hilverman et al, 2017;Hilverman & Duff, 2021) (although also see (Race et al, 2021)). These findings can be interpreted as evidence that certain cognitive processes often viewed as essential to episodic memory, such as generative retrieval, scene construction, visual imagery, and relational processing, may be applied flexibly to other forms of memory and cognition (Duff et al, 2020;Lynch et al, 2020;Rosenbaum et al, 2009).…”

No consolidation without representation: Correspondence between neural and psychological representations in recent and remote memory

“…In developmental amnesia, semantic memory appears to be intact despite significant hippocampal agenesis and episodic memory impairment (Vargha-Khadem et al, 2001;Gadian et al, 2000;Guillery-Girard et al, 2004;Elward and Vargha-Khadem, 2018). Though developmental amnesia allows for normal knowledge of intrinsic features of concepts, it leads to abnormal semantic representations of extrinsic features of concepts (e.g., typical uses or locations of objects) (Blumenthal et al, 2017) similar to deficits described in remote semantic knowledge in adult-acquired amnesia (Waidergoren et al, 2012;Hilverman and Duff, 2021). Rapid acquisition of new knowledge has also been described in adult-acquired amnesia when it is tied to prior knowledge (Skotko et al, 2004;Ryan et al, 2013;Sharon et al, 2011;Merhav et al, 2014;Kopelman and Morton, 2015;Westmacott et al, 2004;Corkin, 2013), consistent with the notion that cortical memory traces can be formed rapidly at the time of encoding (Hebscher et al, 2019b).…”

Missing links: the functional unification of language and memory (L∪M)

“…Despite apparent "autonetic" amnesia, these children who grew up without functional hippocampi show vast preservation of the verbal "semantic" learning and productioncomprehension language abilities (Gadian et al, 2000). However, similar damage occurring in adulthood can lead to quantifiable disorders of naming or the social use of language (Duff et al, 2009;Hilverman & Duff, 2021). The idiosyncratic interdependencies and equilibria specific to an early atypical brain configuration have yet to be specified.…”