Relearning in semantic dementia reflects contributions from both medial temporal lobe episodic and degraded neocortical semantic systems: Evidence in support of the complementary learning systems theory

Emily J. Mayberry, Karen Sage, Sheeba Ehsan, Matthew A. Lambon Ralph

    Research output: Contribution to journalArticlepeer-review

    142 Downloads (Pure)

    Abstract

    When relearning words, patients with semantic dementia (SD) exhibit a characteristic rigidity, including a failure to generalise names to untrained exemplars of trained concepts. This has been attributed to an over-reliance on the medial temporal region which captures information in sparse, non-overlapping and therefore rigid representations. The current study extends previous investigations of SD relearning by re-examining the additional contribution made by the degraded cortical semantic system. The standard relearning protocol was modified by careful selection of foils to show that people with semantic dementia were sometimes able to extend their learning appropriately but that this correct generalisation was minimal (i.e. the patients under-generalised their learning). The revised assessment procedure highlighted the fact that, after relearning, the participants also incorrectly over-generalised the learned label to closely related concepts. It is unlikely that these behaviours would occur if the participants had only formed sparse hippocampal representations. These novel data build on the notion that people with semantic dementia engage both the degraded cortical semantic (neocortex) and the episodic (medial temporal) systems to learn. Because of neocortical damage to the anterior temporal lobes, relearning is disordered with a characteristic pattern of under- and over-generalisation. © 2011 Elsevier Ltd.
    Original languageEnglish
    Pages (from-to)3591-3598
    Number of pages7
    JournalNEUROPSYCHOLOGIA
    Volume49
    Issue number13
    DOIs
    Publication statusPublished - Nov 2011

    Keywords

    • Anterior temporal lobes
    • Over-generalisation
    • Relearning
    • Semantic memory
    • Under-generalisation

    Fingerprint

    Dive into the research topics of 'Relearning in semantic dementia reflects contributions from both medial temporal lobe episodic and degraded neocortical semantic systems: Evidence in support of the complementary learning systems theory'. Together they form a unique fingerprint.

    Cite this