# Enhancing the spatial control of non-invasive brain stimulation by magnetic temporal interference

> **NIH NIH F32** · MASSACHUSETTS GENERAL HOSPITAL · 2021 · $36,331

## Abstract

Project Summary/Abstract
Electromagnetic brain stimulation is a safe and proven way of controlling neural activity non-invasively with no
implanted hardware or injected biochemical agents. Transcranial magnetic stimulation (TMS) is FDA approved
for treatment of drug resistant depression and obsessive compulsory disorder with a range of other clinical
applications under investigation. Its use in neuroscience research has also seen rapid expansion in recent years
due to its ability to test causality by non-invasively perturbing neural activity.
The most critical limitation of TMS is its inability to focus the stimulation depth-wise in a spatially selective manner;
the electric field (E-field) is always maximal in the superficial region, closest to the stimulating coil. This is a major
limitation given the critical role that subcortical structures play in both health and disease. Using the superposition,
or “temporal interference”, of E-fields oscillating at different frequencies to create an amplitude modulation (AM)
maximum at a given target in the subcortex has been suggested as a work-around to this problem. While the E-
fields are still strongest in the superficial region, the neurons time-lock to the AM oscillation rather than the
oscillations of the individual E-fields, yielding enhanced stimulation in the subcortical superposition zone. A
recent study demonstrated the feasibility of this concept in a mouse model using electrical stimulation delivered
via two electrode pairs at opposing sides of the skull. Although these pre-clinical animal data were very promising,
the use of scalp electrodes will be problematic for human translation due to the high conductivity ratio between
the scalp and skull tissues that shunts the current and leads to very weak E-fields inside the cranium of humans.
In this F32 project, we propose developing a temporal interference approach using magnetic stimulation (TiMS)
which could be a more translatable technique to humans than electrical stimulation. Unlike electrical stimulation,
magnetic fields efficiently pass through the human skull inducing clearly suprathreshold E-fields in the brain that
can directly depolarize neurons. Firstly, the theoretical feasibility of the proposed technique in terms of
stimulation efficiency and safety limits will be investigated by computational modeling. The theoretical results will
then be validated in a phantom head model using a low-power system usually used for MRI shimming that is
currently in place in our lab. Finally, based on these computational results and the experimental verification of
the idea, we will design, build, and validate a prototype device capable of delivering effective intracranial TiMS
by connecting custom made TMS coils to an in-house MRI gradient amplifier system. The end goal of the project
is to have a novel device prototype capable of non-invasive brain stimulation that is steerable along the depth
dimension and ready to be used in non-human primate m...

## Key facts

- **NIH application ID:** 10316652
- **Project number:** 1F32MH127789-01
- **Recipient organization:** MASSACHUSETTS GENERAL HOSPITAL
- **Principal Investigator:** John Gustaf Wilhelm Samuelsson
- **Activity code:** F32 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $36,331
- **Award type:** 1
- **Project period:** 2021-09-01 → 2022-02-27

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10316652

## Citation

> US National Institutes of Health, RePORTER application 10316652, Enhancing the spatial control of non-invasive brain stimulation by magnetic temporal interference (1F32MH127789-01). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10316652. Licensed CC0.

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