Abstract
The anterior thalamic nuclei are important for spatial and episodic memory, however, surprisingly little is known about the status of these nuclei in neurological conditions that present with memory impairments, such as Down syndrome. We quantified neurons and glial cells in the anterior thalamic nuclei of four older patients with Down syndrome. There was a striking reduction in the volume of the anterior thalamic nuclei and this appeared to reflect the loss of approximately 70% of neurons. The number of glial cells was also reduced but to a lesser degree than neurons. The anterior thalamic nuclei appear to be particularly sensitive to effects of aging in Down syndrome and the pathology in this region likely contributes to the memory impairments observed. These findings reaffirm the importance of examining the status of the anterior thalamic nuclei in conditions where memory impairments have been principally assigned to pathology in the medial temporal lobe.
Highlights
Down syndrome (DS; trisomy 21) is the most common chromosomal disorder, affecting 1 in 1000 live births in the UK (Wu and Morris, 2013)
There was a significant 37% reduction in estimated total number of glial cells in DS brains compared with controls (t(8) 1⁄4 3.43, pc 1⁄4 0.036; g 1⁄4 2.00, 95% CI 1.48e5.43, common language effect size (CL) 1⁄4 93%; Fig. 3D)
A significant reduction in DS brains was observed when glial cells were classified as astroglia (t(8) 1⁄4 3.58, pc 1⁄4 0.036; g 1⁄4 2.09, 95% CI 0.53e3.65; Fig. 3E)
Summary
Down syndrome (DS; trisomy 21) is the most common chromosomal disorder, affecting 1 in 1000 live births in the UK (Wu and Morris, 2013). There has been a noticeable increase in life expectancy for adults with DS, with the median life expectancy in England and Wales currently at 58 years (Wu and Morris, 2013) This increase in lifespan has resulted in a concomitant increase in the number of adults with DS affected by dementia, Alzheimer’s disease (AD), which is considerably more prevalent in adults with DS than the general population (e.g., Zigman and Lott, 2007). Neuroimaging studies have only focused on the thalamus as a whole (e.g., Annus et al, 2017; Teipel et al, 2004), which does not take into account the structural and functional heterogeneity in the thalamus Owing to their size and location, it is difficult to obtain accurate measures of ATN volume using current neuroimaging techniques, which makes postmortem assessments all the more important. Stereological counts of neurons and glial cells were made in the ATN of four aged female brains with DS and six age-matched controls
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