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

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.

Brain regions involved in subprocesses of small-space episodic object-location memory: a systematic review of lesion and functional neuroimaging studies

“…There were no significant group differences for the number of learning trials until perfect immediate cued OLM recall, delayed cued OLM recall after one hour, and in all OM measures. Hence, Tu et al's (2014) results implicate that the left medio-dorsal nucleus of the thalamus is not involved in object processing within categorical OLM. It is also not involved in location processing or object-location binding during encoding or cued recall up to one hour of categorical OLM, but seems to be specialised for location processing or object-location binding for cued recall after at least one hour.…”

“…Only two lesion studies (Incisa della Rocchetta et al, 2004;Tu, Miller, Piguet, & Hornberger, 2014) investigated easy delayed OM recognition which was required for object processing in the OLM tasks of the two PET studies (Owen et al, 1996b;Petersson et al, 2001). However, they assessed patients with lesions to other brain regions than those found in the two PET studies.…”

“…This is compatible with all other previously reviewed studies on this subject. Tu et al (2014) examined patients with unilateral focal strokes to the left medio-dorsal nucleus of the thalamus (in a few patients the stroke also affected the anterior nucleus or the ventrolateral nucleus of the thalamus, in one patient also the cerebellum, and in another also the brainstem). They assessed categorical OLM and OM within the same paradigm with six different measures.…”

Thalamic amnesia after infarct

“… 11 Therefore, anterior-medial thalamic strokes may also damage the MTT and cause memory impairment. 4 , 11 , 16 , 17 An important caveat in previous studies is that many have relied on single or a few cases. Neuroimaging has been absent or of poor quality, and few studies have used a thalamic atlas fused with MRI scans to identify the damaged structures.…”

The GABAB receptor agonist, baclofen, contributes to three distinct varieties of amnesia in the human brain – A detailed case report

“…The hippocampus is a plausible candidate, given its high density of GABA B receptors (Osten, Wisden, & Sprengel, 2007), proximity to the CSF and involvement in TEA and related disorders. However other structures, such as the septal nuclei (Moor, DeBoer, & Westerink, 1998;Turi, Wittmann, Lechan, & Losonczy, 2015) and thalamus (Tu, Miller, Piguet, & Hornberger, 2014), could also have played a role.Other comments: 1)The authors state that Baclofen is standard treatment of spasticity. This is not true in general, as baclofen is standard treatment for spasticity associated with certain neurological conditions, but not with others…”