Effects of Transcranial Focused Ultrasound on Human Primary Motor Cortex Using 7T fMRI

Transcranial focused ultrasound (tFUS) is a form of neuromodulation that uses a single element transducer to produce highly focused low-intensity acoustic energy that can be used to affect cortical excitability in humans. This technology has an advantage over existing electric and electromagnetic technologies in that it has very high spatial resolution and can be focused deep to the cortical surface to target sub-cortical neural structures and circuits. Previous research has shown that tFUS can affect human tactile detection thresholds (Legon et al. 2014a) as well as functional measures of the electroencephalogram (EEG) (Legon et al. 2014a; Mueller et al. 2014a). However, EEG does not provide for detailed spatial mappings and thus the specific spatial extent of the effect of acoustic energy in the cortex is not yet understood. This is an important consideration for the advancement of tFUS as a non-surgical method of stimulation of discrete cortical circuits and small sub-cortical neural structures. Is the effect of tFUS limited to its beam maxima? Does the effect extend along the beam path? And if so, to what extent? These questions can be answered if tFUS is combined with magnetic resonance imaging (MRI).