Abstract
The objective was to investigate the influence of audiovisual training on horizontal sound localization and the underlying neurological mechanisms using a combination of psychoacoustic and electrophysiological (i.e., event-related potential, ERP) measurements on sound localization. Audiovisual stimuli were used in the training group, whilst the control group was trained using auditory stimuli only. Training sessions were undertaken once per day for three consecutive days. Sound localization accuracy was evaluated daily after training, using psychoacoustic tests. ERP responses were measured on the first and last day of tasks. Sound localization was significantly improved in the audiovisual training group when compared to the control group. Moreover, a significantly greater reduction in front-back confusion ratio for both trained and untrained angles was found between pre- and post-test in the audiovisual training group. ERP measurement showed a decrease in N1 amplitude and an increase in P2 amplitude in both groups. However, changes in late components were only found in the audiovisual training group, with an increase in P400 amplitude and decrease in N500 amplitude. These results suggest that the interactive effect of audiovisual localization training is likely to be mediated at a relatively late cognitive processing stage.
Highlights
The ability to correctly localize sounds is an important feature of the auditory system and is directly associated with the ability to extract binaural information from surrounding sounds (Ahveninen et al, 2014)
The results demonstrated a main effect of factor ‘‘Group’’ (F(1,12) = 5.366, p = 0.039), which revealed that Mean absolute error (MAE) for only auditory control group was significantly larger than that for audiovisual training group
Considering findings obtained from the spread of the reduction of front-back confusion by the effect of audiovisual training to untrained locations, the present study suggests that high cognitive level of cortical process contribute to the sound localization enhancement of audiovisual training
Summary
The ability to correctly localize sounds is an important feature of the auditory system and is directly associated with the ability to extract binaural information from surrounding sounds (Ahveninen et al, 2014). To accurately localize a sound, many acoustic cues may be needed These include monaural cues such as spectral cues (determined by the interaction of the sound with the body, torso, head and shape of the external pinna), and binaural cues such as interaural-time difference (ITD) and interaural-level difference (ILD; which result from time and intensity differences between sounds arriving at the two ears; Bregman, 1990; Blauert, 1997). These cues are integrated in the brain and help to form and adjust individualized spatial map and related cortex and sub-cortex structures (Grothe et al, 2010; Ahveninen et al, 2014). Change to central reorganization and plasticity associated with hearing impairment may be one of the reasons for poor sound localization (Keating and King, 2013; Kral et al, 2016)
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