Abstract
IntroductionDespite the thalamus’ dense connectivity with both cortical and subcortical structures, few studies have specifically investigated how thalamic connectivity changes with age and how such changes are associated with behavior. This study investigated the effect of age on thalamo‐cortical and thalamo‐hippocampal functional connectivity (FC) and the association between thalamic FC and visual–spatial memory and reaction time (RT) performance in older adults.MethodsResting‐state functional magnetic resonance images were obtained from younger (n = 20) and older (n = 20) adults. A seed‐based approach was used to assess the FC between the thalamus and (1) sensory resting‐state networks; (2) the hippocampus. Participants also completed visual–spatial memory and RT tasks, from the Cambridge Neuropsychological Test Automated Battery (CANTAB).ResultsOlder adults exhibited a loss of specificity in the FC between sensory thalamic subregions and corresponding sensory cortex. Greater thalamo‐motor FC in older adults was associated with faster RTs. Furthermore, older adults exhibited greater thalamo‐hippocampal FC compared to younger adults, which was greatest for those with the poorest visual–spatial memory performance.ConclusionAlthough older adults exhibited poorer visual–spatial memory and slower reaction times compared to younger adults, “good” and “poorer” older performers exhibited different patterns of thalamo‐cortical and thalamo‐hippocampal FC. These results highlight the potential role of thalamic connectivity in supporting reaction times and memory in aging. Furthermore, these results highlight the importance of including the thalamus in studies of aging to fully understand how brain changes with age may be associated with behavior.
Highlights
Despite the thalamus’ dense connectivity with both cortical and subcortical structures, few studies have investigated how thalamic connectivity changes with age and how such changes are associated with behavior
Evidence from patients with thalamic infarcts supports the view that disrupted thalamo- cortical structural connectivity is associated with memory problems (Serra et al, 2014), while functional connectivity (FC) strength between the dorsomedial nucleus of the thalamus and parts of the striatum has been negatively associated with episodic memory functioning in 49- to 80-year-olds (Ystad, Eichele, Lundervold, & Lundervold, 2010)
Studies that have used measures of structural connectivity have suggested that the integrity of thalamic nuclei and their projections to cortical regions decline with age (Hasan et al, 2011; Hughes et al, 2012; Ota et al, 2007) and that these changes have implications for attention, processing speed, working, and episodic memory
Summary
The precise function of this diffuse thalamo-cortical and cortico-thalamic connectivity remains poorly understood, it has been argued that higher order nuclei may function to modulate neuronal synchrony between different cortical regions and networks, to increase the efficiency of information transfer (see Saalmann 2014 for a review) These recent studies provide convincing evidence for the role of the thalamus in modulating cortical activity, but how this thalamo- cortical circuitry might be affected by advancing age, and whether changes to the thalamo-cortical system relate to cognitive declines with age, has received surprisingly little attention. We investigated hippocampal–thalamic FC, across all subregions, given the importance of these connections to memory
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