The role of spatial hearing as a key factor in speech perception in noise: Investigating an auditory hypothesis in right hemisphere stroke patients with unilateral spatial neglect

Speech perception in noise is an important function in everyday auditory environments and strongly affects the quality of life. This function depends on the ability of auditory system to separate different streams of sounds and to focus on desired target ones. For this purpose, auditory system uses different sound features. It seems that spatial hearing or auditory lateralization/localization skills plays an important role in speech perception in noise. To test this hypothesis, we recruited the stroke patients with unilateral spatial neglect whose main characteristic of their disorder is multisensory spatial biases. We hypothesized that training of spatial hearing (auditory lateralization training) should improve the speech perception in noise. Participants in our interventional study included 15 patients with right hemisphere stroke and unilateral spatial neglect. Auditory lateralization training consisted of lateralization of sounds simulated by interaural time difference under headphone. Training group received 12 sessions of auditory lateralization training in a modified manner with long-lasting trial time and an oddball stimulus presentation method. To investigate the training program effects, spatial word recognition score in noise test and SSQ questionnaire were conducted three times, before training, after training, and one month later. Patients in training group demonstrated significant improvements in auditory lateralization task and even untrained measures of spatial WRS in noise score (p value <= 0.001). Our results suggest that auditory lateralization training could ameliorate auditory spatial biases in neglect patients. Importantly, this training resulted to enhanced spatial word recognition score in noise without any specific speech in noise practices that could support the hypothetical role of spatial hearing in speech perception in noise.