Abstract
BackgroundThe deterioration of the central cholinergic system in aging is hypothesized to underlie declines in several cognitive domains, including memory and executive functions. However, there is surprisingly little direct evidence regarding acetylcholine’s specific role(s) in normal human cognitive aging.MethodsWe used short-latency afferent inhibition (SAI) with transcranial magnetic stimulation (TMS) as a putative marker of cholinergic activity in vivo in young (n = 24) and older adults (n = 31).ResultsWe found a significant age difference in SAI, concordant with other evidence of cholinergic decline in normal aging. We also found clear age differences on several of the memory and one of the executive function measures. Individual differences in SAI levels predicted memory but not executive functions.ConclusionIndividual differences in SAI levels were better predictors of memory than executive functions. We discuss cases in which the relations between SAI and cognition might be even stronger, and refer to other age-related biological changes that may interact with cholinergic activity in cognitive aging.
Highlights
The deterioration of the central cholinergic system in aging is hypothesized to underlie declines in several cognitive domains, including memory and executive functions
Young adults generally exhibited marked motor evoked potentials (MEP) suppression in response to afferent conditioning leading to high levels of short-latency afferent inhibition (SAI) (18.13 ± 15.74)
We investigated the relation of SAI, a putative neurophysiological marker of cholinergic activity, to memory and executive functions in aging
Summary
The deterioration of the central cholinergic system in aging is hypothesized to underlie declines in several cognitive domains, including memory and executive functions. Normal aging is associated with declines in several cognitive domains, most notably episodic memory and executive functions (for reviews, see [1,2,3,4]). Much of what we infer about the role of ACh in cognitive aging comes from studies in which Alzheimer’s patients are treated with cholinesterase inhibitors, including donepezil, galantamine, and rivastigmine (e.g., [19]). These patients can be difficult to test and experience other confounding factors including significant structural and functional brain changes. There is a need to further examine the in vivo contribution of age-related alterations in central cholinergic function to declines in human cognition
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