FMRI-compatible registration of jaw movements using a fiber-optic bend sensor

Sörös Sörös

doi:10.3389/fnhum.2010.00024

Abstract

A functional magnetic resonance imaging (fMRI)-compatible fiber-optic bend sensor was investigated to assess whether the device could be used effectively to monitor opening and closing of the jaw during an fMRI experiment at 3 T. In contrast to surface electromyography, a bend sensor fixed to the chin of the participant is fast and easy to use and is not affected by strong electromagnetic fields. Bend sensor recordings are characterized by high validity (compared with concurrent video recordings of mouth opening) and high reliability (comparing two independent measurements). The results of this study indicate that a bend sensor is able to record the opening and closing of the jaw associated with different overt speech conditions (producing the utterances /a/, /pa/, /pataka/) and the opening of the mouth without speech production. Data post-processing such as filtering was not necessary. There are several potential applications for bend sensor recordings of speech-related jaw movements. First, bend sensor recordings are a valuable tool to assess behavioral performance, such as response latencies, accuracies, and completion times, which is particularly important in children, seniors, or patients with various neurological or psychiatric conditions. Second, the timing information provided by bend sensor data may improve the predicted hemodynamic response that is used for fMRI analysis based on the general linear model (GLM). Third, bend sensor recordings may be included in GLM analyses not for statistical contrast purposes, but as a covariate of no interest, accounting for part of the data variance to model fMRI artifacts due to motion outside the field of view.

Highlights

A comparison of bend sensor recordings inside the magnet and outside the magnet room with different frequencies (0.25 and 0.5 Hz) revealed no artefacts or distortions of the sensor signal due to functional magnetic resonance imaging (fMRI) scanning (Figure 5)
In this study, recording the opening and closing of the jaw using a fiber-optic, fMRI-compatible bend sensor proved to be a valuable alternative to the established methods, demonstrating good reliability and validity (Figures 5 and 6)
Bend sensor recordings were found to be valid as assessed by a comparison between video recordings and concurrent bend sensor recordings of mouth opening (Figure 6)

Summary

Introduction

A growing number of functional magnetic resonance imaging (fMRI) studies on the neural correlates of overt speaking (Abrahams et al, 2003; Gracco et al, 2005; Bohland and Guenther, 2006; Sörös et al, 2006a; Christoffels et al, 2007; Riecker et al, 2008) and singing (Riecker et al, 2000; Kleber et al, 2007) have been published. A major advantage of investigating overt speech in contrast to silent (or covert) speech is the possibility to monitor the behavioral performance during the experiment (Abrahams et al, 2003). Assessing task performance such as response latency or movement amplitude is especially important in studies involving children, seniors, or patients with various neurological or psychiatric conditions who might give delayed responses or even omit responses. The objective of the present study was to demonstrate the use of a fiber-optic bend sensor, fixed to the chin, to record speech-related jaw movements during fMRI. Fiber-optic based bend sensors have been used in various fields of biomedical research, including the monitoring of finger (Ku et al, 2003; Gorbet et al, 2004; Jindrich et al, 2004; Gorbet and Sergio, 2007) and ankle movements (Seto, 2000; Seto et al, 2001; MacIntosh et al, 2004)

Objectives

Methods

Results

Conclusion