Accelerated forgetting of contextual details due to focal medio-dorsal thalamic lesion.

Sicong Tu,Olivier Piguet,Laurie Miller,Michael Hornberger

doi:10.3389/fnbeh.2014.00320

Abstract

Effects of thalamic nuclei damage and related white matter tracts on memory performance are still debated. This is particularly evident for the medio-dorsal thalamus which has been less clear in predicting amnesia than anterior thalamus changes. The current study addresses this issue by assessing 7 thalamic stroke patients with consistent unilateral lesions focal to the left medio-dorsal nuclei for immediate and delayed memory performance on standard visual and verbal tests of anterograde memory, and over the long-term (>24 h) on an object-location associative memory task. Thalamic patients showed selective impairment to delayed recall, but intact recognition memory. Patients also showed accelerated forgetting of contextual details after a 24 h delay, compared to controls. Importantly, the mammillothalamic tract was intact in all patients, which suggests a role for the medio-dorsal nuclei in recall and early consolidation memory processes.

Highlights

The thalamus is one of the major relay centers of the brain, and part of the limbic memory circuit, comprising hippocampus, fornix, mammillary bodies, mammillothalamic tract, thalamus, and cingulate cortex (Aggleton and Brown, 1999)
Thalamic patients performed in the normal range on assessments of overall cognitive function (MMSE, Addenbrooke’s Cognitive Examination-Revised (ACE-R): total and memory subscore) and did not differ significantly from the control group (Table 1)
No significant correlations were present between memory retention and mammillothalamic tract (MTT) integrity as measured by fractional anisotropy (FA) or mean diffusivity

Summary

Introduction

The thalamus is one of the major relay centers of the brain, and part of the limbic memory circuit, comprising hippocampus, fornix, mammillary bodies, mammillothalamic tract, thalamus, and cingulate cortex (Aggleton and Brown, 1999). With a couple of exceptions (Van der Werf et al, 2003; Perren et al, 2005), reports of memory impairment in patients with focal thalamic lesions have been mostly confined to case studies (Kishiyama et al, 2005; Edelstyn et al, 2006; Carlesimo et al, 2007; Cipolotti et al, 2008; Hampstead and Koffler, 2009). The impact of focal MD damage on memory is, virtually unexplored at the group level

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