Abstract
Deficits in short-term memory (STM) binding are a distinguishing feature of preclinical stages leading to Alzheimer's disease (AD). However, the neuroanatomical correlates of conjunctive STM binding are largely unexplored. Here we examine the possible association between the volumes of hippocampi, parahippocampal gyri, and grey matter within the subcortical structures - all found to have foci that seemingly correlate with basic daily living activities in AD patients - with cognitive tests related to conjunctive STM binding. Hippocampal, thalamic, parahippocampal and corpus striatum volumes were semi-automatically quantified in brain magnetic resonance images from 25 cognitively normal people and 21 patients with Mild Cognitive Impairment (MCI) at high risk of AD progression, who undertook a battery of cognitive tests and the short-term memory binding test. Associations were assessed using linear regression models and group differences were assessed using the Mann-Whitney U test. Hippocampal and parahippocampal gyrus volumes differed between MCI and control groups. Although the grey matter volume in the globus pallidus (r=-0.71, p<0.001) and parahippocampal gyry (r=-0.63, p<0.05) correlated with a STM binding task in the MCI group, only the former remained associated with STM binding deficits in MCI patients, after correcting for age, gender and years of education (β=-0.56,P=0.042) although with borderline significance. Loss of hippocampal volume plays no role in the processing of STM binding. Structures within the basal ganglia, namely the globus pallidus, could be part of the extrahippocampal network supporting binding. Replication of this study in large samples is now needed.
Highlights
As people reach older age, cognitive deterioration is paralleled by the atrophy of multiple brain regions, distinctively seen in dementias such as Alzheimer's disease (AD) (Dubois et al, 2016; Petersen, 2004; Petersen et al, 2009)
Only a fraction of individuals with Mild Cognitive Impairment (MCI) are known to progress to AD (Lazarczyk et al, 2012). amidst the tests that show promise in predicting progression to AD stands out a cognitive test that assesses short-term memory (STM) binding (Parra et al, 2010; 2011; Della Sala et al, 2016; see Costa et al, 2017 for recent consensus recommendations), once it has been discovered that deficits in the ability to temporarily hold bound features such as shapes and colours are present in the pre-clinical stages of AD (Parra et al, 2010; 2011)
Our final sample consisted of 21 MCI patients and 25 control participants of comparable age and education, who had both adequate magnetic resonance imaging (MRI) sequence data to assess the imaging parameters involved in the analyses, and completed the cognitive tests
Summary
As people reach older age, cognitive deterioration is paralleled by the atrophy of multiple brain regions, distinctively seen in dementias such as Alzheimer's disease (AD) (Dubois et al, 2016; Petersen, 2004; Petersen et al, 2009). Materials and methods: Hippocampal, thalamic, parahippocampal and corpus striatum volumes were semi-automatically quantified in brain magnetic resonance images from 25 cognitively normal people and 21 patients with Mild Cognitive Impairment (MCI) at high risk of AD progression, who undertook a battery of cognitive tests and the short-term memory binding test. The grey matter volume in the globus pallidus (r = -0.71, p < 0.001) and parahippocampal gyry (r = -0.63, p < 0.05) correlated with a STM binding task in the MCI group, only the former remained associated with STM binding deficits in MCI patients, after correcting for age, gender and years of education (β = -0.56,P = 0.042) with borderline significance. Replication of this study in large samples is needed
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