Abstract
Iron homeostasis is important for maintaining normal physiological brain functioning. In two independent samples, we investigate the link between iron concentration in the basal ganglia (BG) and implicit sequence learning (ISL). In Study 1, we used quantitative susceptibility mapping and task-related fMRI to examine associations among regional iron concentration measurements, brain activation, and ISL in younger and older adults. In Study 2, we examined the link between brain iron and ISL using a metric derived from fMRI in an age-homogenous sample of older adults. Three main findings were obtained. First, BG iron concentration was positively related to ISL in both studies. Second, ISL was robust for both younger and older adults, and performance-related activation was found in fronto-striatal regions across both age groups. Third, BG iron was positively linked to task-related BOLD signal in fronto-striatal regions. This is the first study investigating the relationship among brain iron accumulation, functional brain activation, and ISL, and the results suggest that higher brain iron concentration may be linked to better neurocognitive functioning in this particular task.
Highlights
Implicit sequence learning (ISL) is a type of non-declarative memory that involves acquisition of complex motor skills
The present investigation examined the potential link between brain iron concentration and neurocognitive markers of ISL
Findings from Study 1 indicate that higher basal ganglia (BG) iron concentration was related to better ISL, and the results from Study 2 confirmed the positive link between brain iron concentration and ISL, using a large age-homogenous sample
Summary
Implicit sequence learning (ISL) is a type of non-declarative memory that involves acquisition of complex motor skills. Such learning occurs when individuals demonstrate significant improvements in speed or accuracy of motor responses, but are typically unable to consciously recall what they have learned. Studies show that ISL is not differentially affected by sleep in older and younger adults (Nemeth et al 2010), but there are observations showing less offline learning (i.e., consolidation) in older compared to younger adults when using a probabilistic second-order regularity sequence that enables separation between general skill learning and sequence-specific learning (Nemeth and Janacsek 2010). The general lack of age differences is somewhat surprising, as the basal ganglia (BG), which is a key region implicated in skill acquisition (Doyon et al 2009a), exhibits marked age-related
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