The importance of mammillary body efferents for recency memory: towards a better understanding of diencephalic amnesia

Nelson, Andrew J. D. ORCID: https://orcid.org/0000-0002-5171-413X and Vann, Seralynne D. ORCID: https://orcid.org/0000-0002-6709-8773 2017. The importance of mammillary body efferents for recency memory: towards a better understanding of diencephalic amnesia. Brain Structure and Function 222 (5) , pp. 2143-2156. 10.1007/s00429-016-1330-x

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Abstract

Despite being historically one of the first brain regions linked to memory loss, there remains controversy over the core features of diencephalic amnesia as well as the critical site for amnesia to occur. The mammillary bodies and thalamus appear to be the primary locus of pathology in the cases of diencephalic amnesia, but the picture is complicated by the lack of patients with circumscribed damage. Impaired temporal memory is a consistent neuropsychological finding in Korsakoff syndrome patients, but again, it is unclear whether this deficit is attributable to pathology within the diencephalon or concomitant frontal lobe dysfunction. To address these issues, we used an animal model of diencephalic amnesia and examined the effect of mammillothalamic tract lesions on tests of recency memory. The mammillothalamic tract lesions severely disrupted recency judgements involving multiple items but left intact both recency and familiarity judgements for single items. Subsequently, we used disconnection procedures to assess whether this deficit reflects the indirect involvement of the prefrontal cortex. Crossed-lesion rats, with unilateral lesions of the mammillothalamic tract and medial prefrontal cortex in contralateral hemispheres, were unimpaired on the same recency tests. These results provide the first evidence for the selective importance of mammillary body efferents for recency memory. Moreover, this contribution to recency memory is independent of the prefrontal cortex. More broadly, these findings identify how specific diencephalic structures are vital for key elements of event memory.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Psychology
Uncontrolled Keywords:	Anterior thalamic nucleiDiencephalic amnesiaMammillothalamic tractPrefrontal cortexRatsRecognition memory
Additional Information:	This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.
Publisher:	Springer
ISSN:	1863-2653
Funders:	Wellcome Trust
Date of First Compliant Deposit:	26 October 2016
Date of Acceptance:	19 October 2016
Last Modified:	07 Nov 2023 11:19
URI:	https://orca.cardiff.ac.uk/id/eprint/95607

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