# MEPs elicited by multidirectional rotational-field TMS show marked differences compared to unidirectional Figure-of-8 and H7 coils

## TL;DR

A new TMS coil design elicits stronger muscle responses at lower thresholds compared to traditional coils, suggesting it could better stimulate neurons for potential brain injury recovery.

## Contribution

The study introduces a novel rotational-field TMS coil that shows improved motor evoked potential responses in healthy subjects.

## Key findings

- rfTMS elicited larger MEPs at a lower resting motor threshold compared to unidirectional coils.
- The multidirectional electric field of rfTMS may recruit a larger neuronal population than conventional TMS configurations.

## Abstract

Unidirectional transcranial magnetic stimulation (udTMS; e.g., via Figure-of-8 coil) depolarizes mainly neurons whose axonal orientation aligns with the direction of the induced electric field. A novel dual H-coil (T360°) TMS system (BrainsWayTM, Israel) generates a rotational magnetic field aimed to recruit a larger neuronal population by induction of a multidirectional electric field (rfTMS). This study aimed to comparatively assess the neurophysiological properties of motor evoked potentials (MEPs) elicited from the first dorsal interosseous (FDI) muscle following udTMS (via Figure-of-8 and H7 coils) vs. multidirectional rfTMS. In this study, 10 healthy adult subjects received TMS via the three coil configurations in a random order. The results showed that rfTMS elicited larger MEPs at a lower resting motor threshold (rMT) compared to the unidirectional coils. These findings suggest that rfTMS is likely to recruit larger populations of neurons compared to conventional udTMS coil configurations. This may be advantageous in efforts to enhance motor recovery following brain damage by treatments using TMS.