Implementation and Validation of Virtual Acoustic Spatial Training (VAST) Program for Remediation of Spatial Deficits in Listeners with Sensorineural Hearing Impairment (SNHI): A Longitudinal Time-Series Study

Abstract

Objective. The present study worked on the validation of a spatial training paradigm using virtual sources (Virtual auditory space training: VAST) as a rehabilitation tool for treating spatial deficits in listeners with sensorineural hearing loss (SNHI). The objectives of the study were to quantify the auditory spatial processing differences between SNHI listeners and normal hearing (NH) using a battery of spatial acuity tests (behavioral and electrophysiological). The second objective was to validate the benefits of VAST in SNHI listeners using a time-series design with multiple timelines of measurement. Method. The study was conducted on 50 participants in the age range of 31-55years were considered in the study. The participants in the study were divided into three groups. Group I (trained SNHI) and Group II (Control SNHI) comprised of 15 individuals each with bilateral symmetrical SNHI, while participants in Group III were 20 NH listeners. The study was conducted in three phases. In the pre-training phase, all the participants underwent - behavioral tests of spatial acuity using tests for binaural processing, virtual auditory space identification (VASI), subjective ratings and P300.In addition, all the behavioral tests were re-administered after a period of 1 month in group I, to quantify variability. In the training phase, group I participants were subjected to VAST, mid-way through which, all the behavioral measures were administered again. Following the completion of training, all pre-training assessments were re-administered on group I and group II (measured at same time-line as group I) as part of post-training evaluation-1. The final series (post-training evaluation-2) of behavioral assessments were conducted after one months post-training in group I. The results indicated that listeners with SNHI (Group I and Group II) had significantly higher (p < 0.05) binaural thresholds and lower VASI scores and subjective ratings (p < 0.01) compared to listeners with NH, indicative of spatial deficits former two groups. The P300 analyses also revealed group differences both in terms of grand average waveforms and other spatio-temporal analyses. Additionally, the results also demonstrated a positive impact of VAST training on all the measures except threshold of interaural level difference in Group I listeners. The benefit derived from VAST was higher than the general variability exhibited by the Group I listeners, whose retention effects lasted for a month after training. In addition, VAST induced new scalp topographies in Group I at post-training evaluation, indicative of spatial plasticity at cortical level. Both behavioral and electrophysiological changes noticed in Group I were absent in group II, whose spatial acuity was measure at two measurement timelines (pre training 1; post training 1) without any formal training. Thus, the efficacy of the VAST paradigm used in the current study is validated in remediating spatial deficits in listeners with SNHI.