Abstract
Aging is normally associated with increased predictability of neurophysiological processes. To test the related prediction of age-related increase in the Hurst exponent, H, of functional MRI time series, and its possible cholinergic mechanisms, two groups of healthy participants (old [mean age = 65 years]; young [mean age = 22 years]; N = 11 per group) were scanned twice at rest, following placebo and a muscarinic receptor antagonist, scopolamine 0.3 mg. Older age was associated with significant increase in H of fMRI time series in bilateral hippocampus. Similarly, scopolamine was associated with increased H in left hippocampus; and there was an age-by-drug interaction in medial temporal lobe whereby older participants specifically had increased H following scopolamine. Scopolamine also enhanced fronto-hippocampal low-frequency coherence, and this could be correlated with its effect on hippocampal H. Thus, increased persistence of hippocampal dynamics in older subjects is demonstrable by resting fMRI; scopolamine mimics these effects, especially in older subjects, implying a cholinergic mechanism for age-related change; and cholinergic effects on hippocampal dynamics are associated with enhanced functional connectivity between frontal cortex and hippocampus.
Original language | English |
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Pages (from-to) | 1395-404 |
Number of pages | 10 |
Journal | Neurobiology of aging |
Volume | 27 |
Issue number | 10 |
DOIs | |
Publication status | Published - Oct 2006 |
Keywords
- Acetylcholine/metabolism
- Action Potentials/drug effects
- Adult
- Aged
- Aging/physiology
- Brain Mapping
- Cerebrovascular Circulation/drug effects
- Double-Blind Method
- Electroencephalography
- Female
- Hippocampus/blood supply
- Humans
- Magnetic Resonance Imaging
- Male
- Middle Aged
- Muscarinic Antagonists/administration & dosage
- Placebo Effect
- Scopolamine/administration & dosage