Estimation of the spatial profile of neuromodulation and the temporal latency in motor responses induced by focused ultrasound brain stimulation - PubMed (original) (raw)

Estimation of the spatial profile of neuromodulation and the temporal latency in motor responses induced by focused ultrasound brain stimulation

Hyungmin Kim et al. Neuroreport. 2014.

Free PMC article

Abstract

This study investigates the spatial profile and the temporal latency of the brain stimulation induced by the transcranial application of pulsed focused ultrasound (FUS). The site of neuromodulation was detected using 2-deoxy-2-[¹⁸F]fluoro-D-glucose PET immediately after FUS sonication on the unilateral thalamic area of Sprague-Dawley rats. The latency of the stimulation was estimated by measuring the time taken from the onset of the stimulation of the appropriate brain motor area to the corresponding tail motor response. The brain area showing elevated glucose uptake from the PET image was much smaller (56±10% in diameter, 24±6% in length) than the size of the acoustic focus, which is conventionally defined by the full-width at half-maximum of the acoustic intensity field. The spatial dimension of the FUS-mediated neuromodulatory area was more localized, approximated to be full-width at 90%-maximum of the acoustic intensity field. In addition, the time delay of motor responses elicited by the FUS sonication was 171±63 (SD) ms from the onset of sonication. When compared with latencies of other nonultrasonic neurostimulation techniques, the longer time delay associated with FUS-mediated motor responses is suggestive of the nonelectrical modes of neuromodulation, making it a distinctive brain stimulation method.

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Figures

Fig. 1

Fig. 1

(a) An exemplar PET image from one animal with an illustration of sonication (inset). The arrows indicate the direction of the sonication path. A region-of-interest (marked in a black rectangle) was placed on the opposite side of the sonicated hemisphere to estimate the baseline standardized uptake value signal level. (b) A close-up look near the acoustic focus. The longitudinal (vertical) and transversal (horizontal) orientations to the sonication path are shown by dashed–dotted lines. The contours of the conventional acoustic focus (denoted as ‘FWHM’) and the approximated neuromodulatory area according to the group-based analysis (denoted as ‘FW9/10M’) are shown by dashed lines. Note that the ‘FW9/10M’ of the acoustic intensity field, on the basis of the group-averaged estimation, occupied a much wider area than the stimulated area in the given example from one animal. FWHM, full-width at half-maximum.

Fig. 2

Fig. 2

Recorded tail movement signal and the illustration of criterion (example shown from the single trial data from one animal, i.e. 2_σ_ above the resting-state signal) for the measurement of response delay (inset). The duration of sonication (i.e. 300 ms) is represented by the rectangular boxes.

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