Individual theta frequency for associative memory targeted personalized transcranial electrical stimulation

Abstract

Objectives: To develop and evaluate a new approach for determining individual theta frequency (ITF) in EEG data recorded during an associative memory task, that can be used for personalization of frequency-modulated electrical brain stimulation (tACS, otDCS). Content: Non-invasive brain stimulation (NIBS) methods have gained increased interest in research and therapy of associative memory (AM) and its impairments. However, the one-size-fits-all approach yields inconsistent findings, thus putting forward the need for electroencephalography (EEG) guided personalized frequency-modulated transcranial electrical stimulation (tES) protocols to increase the focality and the effectiveness of the interventions. Still, extraction of individual frequency, especially in the theta band, turned out to be a challenging task. We present an approach to extracting the individual theta-band frequency (ITF) from context-dependent EEG signals recorded during the AM task. The method showed a 93% success rate, good reliability, and a full range of variability of the extracted ITFs. The method considers the individual differences in theta-peak latencies and enables quantification of the within-person reliability of the extracted ITF. The approach has been implemented in a healthy-subjects experiment assessing the neurophysiological and behavioral effects of ITF-tES. We will discuss the implementation of the method and how ITF could be used as an input parameter for personalized frequency-modulated NIBS approaches—transcranial alternating current stimulation (tACS) and transcranial oscillatory direct current stimulation (otDCS) directed at AM neuromodulation.