Does visual stimuli assist in understanding speech in noise in children? - an EEG and MEG study

It is commonly recognised that visual cues can enhance speech intelligibility in quiet as well as in noisy listening environments. It has been shown that visual cues can improve speech perception in noise and that the improved signal-to-noise ratio may be perceived to be as much as 15 dB (Sumby, 1954). Children with auditory processing disorders are a heterogeneous group (ASHA, 1996; Chermak, 2002; Ramus et al., 2003; Sharma, Purdy, & Kelly, 2009) and are described as having listening difficulties, e.g. difficulties listening in noise and one of the main interventions recommended for this population is addition of visual cues; however, audiovisual integration is not well understood at a cortical level. This study aims to investigate the effect of visual cues on auditory perception of speech in noise in children (7-12 years) with and without auditory processing disorders. Cortical evoked potentials (CAEPS) were recorded using electroencephalography (EEG) and magnetoencephalography (MEG) in response to the natural speech token /ba/ presented as unimodal (auditory only and visual only) or bimodal (audiovisual) stimuli and at two different signal-to-noise ratios (+3 dB and +10dB). Results show that elevated noise levels have a detrimental effect on responses to unimodal auditory stimuli, but that the addition of visual cues results in robust auditory evoked responses at both noise levels.