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Electric Field Modeling for Planning Individualized HD-tACS to Target DLPFC in the Aging Brain.
Summary
Optimizing High-Definition Transcranial Alternating Current Stimulation (HD-tACS) for the aging brain is crucial. Individualizing current in the 2x1 montage enhances targeting of the dorsolateral prefrontal cortex (DLPFC) and reduces eye stimulation.
Area of Science:
- Neuroscience
- Neuroimaging
- Biomedical Engineering
Background:
- Non-invasive brain stimulation efficacy relies on precise targeting.
- Aging populations exhibit significant variations in brain morphology, complicating stimulation.
- High-Definition Transcranial Alternating Current Stimulation (HD-tACS) offers potential for targeted brain modulation.
Purpose of the Study:
- To investigate electric field distribution for HD-tACS targeting the right dorsolateral prefrontal cortex (DLPFC) in young and older adults.
- To compare the focality and strength of electric fields generated by different HD-tACS montages (2x1 vs. 4x1).
- To explore individualized current adjustments for optimizing stimulation efficacy and safety.
Main Methods:
- Utilized SimNIBS and FreeSurfer with T1- and T2-weighted MRI data from 5 young (18-39 years) and 5 older adults (63-76 years).
- Simulated electric field distribution for 2x1 and 4x1 HD-tACS montages delivering 2 mA net current.
- Analyzed peak and mean electric field strength at the DLPFC and spread to the ocular area.
Main Results:
- The 2x1 montage produced approximately three times stronger peak and mean electric fields at the DLPFC compared to the 4x1 montage.
- The 2x1 montage exhibited reduced focality, with electric field spread into the ocular area observed in some participants.
- Individualizing current in the 2x1 montage allowed for comparable electric field strength across participants while mitigating ocular spread.
Conclusions:
- The 2x1 HD-tACS montage delivers a stronger electric field to the DLPFC but requires careful optimization due to potential ocular spread.
- Individualized current delivery is a viable strategy to enhance DLPFC targeting and minimize side effects like phosphenes in HD-tACS.
- These findings are critical for advancing the application of HD-tACS in aging populations and other groups with high interindividual variability.
