Transcranial alternating current stimulation over multiple brain areas with non-zero phase delays other than 180
Jimin Park1, Sangjun Lee1, Seonghun Park1
1Department of Electronic Engineering, Hanyang University, 222 Wangsimni-ro, Seongdong-gu, Seoul, 133-791, Republic of Korea.
Scientific Reports
|August 5, 2023
Summary
New multi-site multi-phase transcranial alternating current stimulation (msmp-tACS) can modulate brain communication directions. This noninvasive brain stimulation method influenced visuospatial working memory by altering phase delays between brain regions.
Area of Science:
- Neuroscience
- Cognitive Science
- Biomedical Engineering
Background:
- Brain region communication is often characterized by zero-phase lag synchronization.
- Systematic phase delays in electroencephalography (EEG) signals may indicate communication direction between cortical regions.
- Modulating these phase delays could offer new ways to study and influence brain network dynamics.
Purpose of the Study:
- To propose and test a novel noninvasive brain stimulation (NIBS) method, multi-site multi-phase tACS (msmp-tACS).
- To investigate if msmp-tACS can modulate the direction of communication between distant brain areas using phase delays.
- To assess the impact of msmp-tACS on visuospatial working memory (VWM) performance.
Main Methods:
- Developed msmp-tACS, a novel NIBS technique applying tACS with controlled phase differences across multiple scalp electrodes.
- Utilized finite element analysis with phasor representation to determine optimal stimulation parameters (amplitudes and phases).
- Applied 80 Hz msmp-tACS over bilateral intraparietal sulci (IPS) in a case study involving a VWM task, comparing synchronized, right-leading (RL), and left-leading (LR) phase conditions.
Main Results:
- msmp-tACS with a 90° phase lead of the right IPS over the left IPS (RL condition) significantly lateralized VWM performance towards the right visual hemifield.
- This VWM shift resulted from effects on both left and right hemifield trials, not a change in capacity of a specific hemifield.
- The observed VWM performance modulation is attributed to altered brain dynamics and effective connectivity between the rIPS and lIPS.
Conclusions:
- msmp-tACS is a promising NIBS method capable of modulating cortical networks with specific phase delays.
- This technique offers a way to influence brain communication direction, potentially impacting cognitive functions like VWM.
- msmp-tACS may overcome limitations of conventional multi-site stimulation methods in modulating specific neural network dynamics.
