Research
The neuromodlab is primarily focused on exploring the use of ultrasound for non-invasive human neuromodulation. We employ several techniques including electroencephalography (EEG), electromyography (EMG), transcranial magnetic stimulation (TMS), functional magnetic resonance imaging (fMRI), behavioural testing, empirical acoustic testing and computer modelling.
Cranial Window Prothesis for Diagnostic and Therapeutic Cerebral Ultrasound in Vitro and in Vivo
Adapted from J Neurosurg, 2020
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Here we tested a polyolefin-based cranial prosthesis to act as a cranial window for ultrasound (US) imaging. The complex microarchitecture of the bones of the skull causes large discrepancies in acoustic imaging. We found that the prothesis resulted in a decrease in maximum pressure and increases the full width half maximum (FWHM), or the width of the curve at half of its maximum value, except at the center, for all transducers tested. During the testing with two female Yorkshire swine, B-mode US images were compared, one through the dura matter of the brain and the through the prothesis. We found that there was a considerable anatomical correlation with no distortion in terms of depth, structure echogenicity, and anatomical structure location. A small degree of distortion in outermost areas was observed.
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Transcranial focused ultrasound modulates the activity of primary somatosensory cortex in humans
Adapted from Nature Neuroscience, 2014
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Here focused ultrasound (tFUS) was targeted to the human primary somatosensory cortex (S1), where we found a behavioral effect of tFUS which enhanced performance on sensory discrimination tasks without affecting task attention or response bias. We also saw that electrophysiological recordings at C3, one of the electrodes near S1, showed a significant reduction in the peak-to-peak amplitude of the short-latency N20–P27 SEP complex for tFUS compared to sham. Additionally, the changes produced by tFUS were abolished when the acoustic beam was focused 1 cm anterior or posterior to S1. Coronal magnetic resonance slices show projections of the measured tFUS fields from EEG electrode site CP3 (beam's center) and 2 mm posterior to the beam's center. This illustrates the acoustic intensity drop-off as a function of tFUS beam width. (Nature Neuroscience, 2014).
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Neuromodulation with single-element transcranial focused ultrasound in human thalamus
Adapted from Human Brain Mapping, 2017
Here we targeted single-element transcranial focused ultrasound to the thalamus, a deep brain region shown above. tFUS is uniquely able to modulate deep brain regions due to its high spatial resolution. In the present study, tFUS was targeted at unilateral thalamus and was shown to inhibit the amplitude of the P14 SEP as compared to sham. These results were accompanied by alpha and beta power attenuation as well as time‐locked gamma power inhibition. Furthermore, participants performed significantly worse than chance on a discrimination task during tFUS stimulation.
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Computational exploration of wave propagation and heating from transcranial focused ultrasound for neuromodulation
Adapted from Journal of Neural Engineering, 2016
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Here a computational model was constructed and validated against empirical data to show properties of biological material have limited effect on ultrasound wave propagation and resulted in safe heating levels in the skull and brain. Empirical data was collected in an acoustic test tank to compare to model data. Modeling of tFUS showed an increase in temperature within brain and skull layers after 0.5 s burst of stimulation. The heating in the brain layer was low compared to that in the skull and temperature increase in the cerebral spinal fluid is likely due to heat dissipation from the skull.
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