Abstract
Subcortical age-related white matter changes (ARWMC) are a frequent finding in healthy elderly people suggested to cause secondary tissue changes and possibly affecting cognitive processes. We aimed to determine the influence of the extent of ARWMC load on attention and working memory processes in healthy elderly individuals. Fourteen healthy elderly subjects (MMSE >26; age 55–80 years) performed three fMRI tasks with increasing difficulty assessing alertness, attention (0-back), and working memory (2-back). We compared activation patterns in those with only minimal ARWMC (Fazekas 0–1) to those with moderate to severe ARWMC (Fazekas 2–3). During the fMRI experiments, the study population showed activation in brain areas typically involved in attention and working memory with a recruitment of cortical areas with increasing task difficulty. Subjects with higher lesion load showed a higher activation at all task levels with only sparse increase of signal with increasing complexity. In the lower lesion load group, rising task difficulty lead to a significant and widely distributed increase of activation. Although the number of patients included in the study is small, these findings suggest that even clinically silent ARWMC may affect cognitive processing and lead to compensatory activation during cognitive tasks. This can be interpreted as a reduction of functional reserve and may pose a risk for cognitive decline in these patients.
Highlights
As cerebral white matter lesions are highly prevalent in healthy elderly individuals – having been reported in 27%–92% of this population [1,2] – these findings have been termed agerelated white matter changes (ARWMC)
Using diffusion tensor imaging (DTI) and planimetry of the corpus callosum we have recently demonstrated a loss of tissue integrity and atrophy of the corpus callosum secondary to spatially remote – and per se clinically silent – lesions in the peri- and paraventricular white matter in ARWMC in healthy elderly individuals [4]
While numerous studies have attributed a decrease in grey matter volume to cognitive decline and especially to working memory dysfunction, far less have addressed the effect of ARWMC on functional brain changes during working memory tasks
Summary
As cerebral white matter lesions are highly prevalent in healthy elderly individuals – having been reported in 27%–92% of this population [1,2] – these findings have been termed agerelated white matter changes (ARWMC). Their extent seemingly corresponds to a continuum from normal functioning to clinically overt neurological syndromes in subcortical vascular encephalopathy (SVE) with apraxia of locomotion, gait disturbance, working memory deficits and executive dysfunction [3]. An intriguing finding is the recruitment of larger brain areas interpreted as compensation – either with or without clinical correlation [9,10]
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