Enhancing episodic memory in older adults through modulating oscillatory activities in the fronto-posterior network using transcranial alternating current stimulation (MEMTACS)
Final Report Abstract
Oscillatory brain activity in the theta frequency range plays a central role in episodic memory processes. Age-related changes in frontal theta activity and fronto-posterior phase synchroni-zation have been associated with cognitive deficits in older adults. Studies in young adults show that transcranial alternating current stimulation (tACS) is a promising method to modulate theta phase synchronization between frontal and parietal brain regions and enhance cognitive performance. This opens up the possibility of using tACS to modulate age-related changes in oscillatory brain activity and improve cognitive functions in older individuals. The goal of this project was to investigate the potential of tACS to modulate oscillatory brain activity and thereby improve episodic memory processes in older adults. First, electrophysiological correlates of sequential memory processes were compared between young and older adults to identify age-related differences and determinants of successful performance. Using magnetic resonance imaging (MRI), the functional neural networks underlying episodic memory functions were characterized. In subsequent experimental studies, we examined the effects of fronto-posterior tACS application on episodic memory performance and theta oscillations in young and older adults. Structural MRI data enabled the simulation of individual current distributions in the brain to explore dose-response relationships. Our results provide insights into the neural basis of age-related memory decline. On the electrophysiological level, differ-ences in theta and gamma oscillations during encoding play a particularly important role. At the network level, the findings suggest that connectivity between the posterior hippocampus and other central brain structures of the memory-relevant default mode network may represent compensatory mechanisms. Furthermore, we demonstrated that theta-tACS over fronto-posterior brain structures can modulate hippocampal theta oscillations in relation to memory per-formance and improve episodic memory functions in older adults. Simulations of individual electric fields revealed that the induced dose depends on factors such as head volume, head circumference, and age-related atrophy, highlighting the need for individualized stimulation protocols. Overall, the results contribute to the understanding of tACS-induced effects on memory functions and their underlying mechanisms in the aging process. The insights gained will advance the development of individualized stimulation protocols to enhance cognitive function.
Publications
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“Biophysical models of TES and TMS: accuracy, validation, and applications, Talk at the Non-invasive brain stimulation (NIBS) & DGKN conference, 10.-14.11.2020, Virtual Conference.
Antonenko D.
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Estimation of individually induced e-field strength during transcranial electric stimulation using the head circumference. Brain Stimulation, 14(5), 1055-1058.
Antonenko, Daria; Grittner, Ulrike; Puonti, Oula; Flöel, Agnes & Thielscher, Axel
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Inter-individual and age-dependent variability in simulated electric fields induced by conventional transcranial electrical stimulation. NeuroImage, 224, 117413.
Antonenko, Daria; Grittner, Ulrike; Saturnino, Guilherme; Nierhaus, Till; Thielscher, Axel & Flöel, Agnes
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„Individual differences in electric fields induced by transcranial electrical stimulation“, Talk at the Regional Meeting of the Federal European Neuroscience Society (FENS), 25.-27. August 2021, Virtual Conference.
Antonenko D.
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“Differential oscillatory processes associ-ated with successful sequence memory encoding in young and older adults”, Poster at the Psychologie und Gehirn, 16.-18. June 2022, Freiburg, Germany.
Ehrhardt N., Lucchese G., Flöel A. & Antonenko, D.
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“Targeting hippocampus-dependent memory in older adults with tACS-induced theta synchronization”, Poster at the Tagung experimentell arbeitender Psy-cholog:innen (TeaP), 21.-23. March 2022, Virtual Conference.
Ehrhardt N. & Antonenko D.
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„Brain stimulation and aging, spanning from basic physiology, over model-based adaptation of intervention protocols, to applications to improve performance“, Talk at the 32nd International Congress of Clinical Neurophysiology (ICCN), 4.-8. September 2022, Geneva, Switzerland.
Antonenko D.
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“Theta-gamma phase amplitude coupling during sequence memory encoding in healthy older adults”, Poster at the 30th Annual Meeting der Cognitive Neuroscience Society, 25.-28. March 2023, San Francisco, CA, USA.
Ehrhardt N. & Antonenko D.
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„Dose Response in Non-invasive Brain Stimulation: Exploring the Parameter Space“, Talk at the 5th International Brain Stimulation Conference, 18-22 February 2023, Lisbon, Portugal.
Antonenko D.
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Brain oscillatory processes related to sequence memory in healthy older adults. Neurobiology of Aging, 139, 64-72.
Ehrhardt, Nina M.; Flöel, Agnes; Li, Shu-Chen; Lucchese, Guglielmo & Antonenko, Daria
