Subjective cognitive impairment: increased prefrontal cortex activation compared to controls during an encoding task

Abstract

SUMMARYObjective Subjective cognitive impairment (SCI) has been proposed as a clinical stage which may precede mild cognitive impairment in the clinical continuum of AD, and is characterised by the presence of subjective memory complaints in the absence of objective cognitive deficits. Specific memory-related brain activation differences have been reported in mild cognitive impairment and in cognitively normal individuals at known genetic risk of AD; our objective was to determine whether similar differences are present in people with SCI. Methods We compared brain activation in a memory clinic sample of 10 SCI subjects and 10 controls during a verbal episodic memory encoding task using functional magnetic resonance imaging (fMRI). Results There were no differences between groups on measures of encoding success (recognition accuracy) nor was there evidence of altered semantic processing. Both groups activated left prefrontal cortex (PFC) and cerebellum during encoding. The SCI group also demonstrated activation in left medial temporal, occipitoparietal and medial frontal cortex. Group comparisons revealed increased activation in SCI in left PFC, where activation strength correlated with memory task performance. Conclusions The activation differences reported in this study may reflect the employment of compensatory strategies in the face of early AD pathology, although a number of alternative explanations need to be considered. Further studies with larger samples may help to determine whether the observed activation changes are likely to be associated with early neuropathological processes or with other unrelated factors.

Alzheimer's disease risk variant in CLU is associated with neural inefficiency in healthy individuals

“…Numerous studies suggest that the dorsolateral prefrontal cortex is recruited in n-back tasks in response to increasing WM load [36,37]. It is of note that an increased activation within prefrontal regions during memory tasks has been linked to other AD risk factors such as APOE (in a considerably older cohort) [4] and mild/subjective cognitive impairment [38,39]; however, [20] in each the n-back conditions. CLU rs11136000 genotype effects that are significant after correction for multiple comparisons are highlighted in bold.…”

Estrogen–cholinergic interactions: Implications for cognitive aging

“…Older adults with subjective cognitive complaints but normal cognitive performance have been shown to convert to dementia at higher rates than those without complaints (Reisberg et al, 2010) and to have morphologic and functional changes in the brain that may presage developing neurodegenerative disorders (Rodda et al, 2011; Rodda et al, 2009; Saykin et al, 2006). Cognitive complaints have also been associated with the menopause transition (e.g.…”

Early dysfunction of functional connectivity in healthy elderly with subjective memory complaints

“…As far as we know, there are only three previous papers published with functional neuroimaging in patients with SMC (Rodda et al 2010;Rodda et al 2009;Maestu et al 2010). In all three of them, SMC subjects showed higher activation than healthy controls.…”

“…Apart from the depression, the SMC have also been related to anxiety and personality traits (Jorm et al 2004). However, there is also growing evidence to suggest that SMC are associated with an increased risk of dementia and with the presence of biological correlates of early Alzheimer's disease (Rodda et al 2009). …”

“…Studies of brain activity during cognitive tasks note that subjects with SMC present an increase in activity in comparison with the control group (Rodda et al 2009;Rodda et al 2010;Maestu et al 2010;Jessen et al 2010;Elfgren et al 2010;Gallassi et al 2010;Benito-León et al 2010;Luck et al 2010). All these studies have evaluated the spatial or the spatiotemporal profiles of activity, but none of them assess whether the functional connectivity between brain regions was spared or not in subjects with SMC.…”