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Abstract
Objective To test whether targeting hippocampal-cortical brain networks with high-frequency transcranial magnetic stimulation in older adults influences behavioral and neural measures characteristic of age-related memory impairment.
Methods Fifteen adults aged 64 to 80 years (mean = 72 years) completed a single-blind, sham-controlled experiment. Stimulation targets in parietal cortex were determined based on fMRI connectivity with the hippocampus. Recollection and recognition memory were assessed after 5 consecutive daily sessions of full-intensity stimulation vs low-intensity sham stimulation using a within-subjects crossover design. Neural correlates of recollection and recognition memory formation were obtained via fMRI, measured within the targeted hippocampal-cortical network vs a control frontal-parietal network. These outcomes were measured approximately 24 hours after the final stimulation session.
Results Recollection was specifically impaired in older adults compared to a young-adult control sample at baseline. Relative to sham, stimulation improved recollection to a greater extent than recognition. Stimulation increased recollection fMRI signals throughout the hippocampal-cortical network, including at the targeted location of the hippocampus. Effects of stimulation on fMRI recollection signals were greater than those for recognition and were greater in the targeted network compared to the control network.
Conclusions Age-related recollection impairments were causally related to hippocampal-cortical network function in older adults. Stimulation selectively modified neural and behavioral hallmarks of age-related memory impairment, indicating effective engagement of memory intervention targets in older adults.
Glossary
- TMS=
- transcranial magnetic stimulation
Footnotes
Go to Neurology.org/N for full disclosures. Funding information and disclosures deemed relevant by the authors, if any, are provided at the end of the article.
- Received September 12, 2018.
- Accepted in final form January 17, 2019.
- © 2019 American Academy of Neurology
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