Training sound localisation in unilateral cochlear implant users: The effect of audiovisual training on localisation

Abstract

Aims: The purpose of this study was to investigate the effect of audiovisual training, on the horizontal sound localisation ability of adult, unilateral cochlear implant users. It also looked to assess, if learning generalised to untrained stimuli, and whether the addition of feedback to audiovisual training provided any extra effect. Further; it considered the effect of overnight consolidation on performance, and the associations between age, and years of binaural loss pre-implant, with training outcome. Hypotheses: It was hypothesised that audiovisual training would result in improved ability to locate both training and generalisation stimuli in auditory only conditions. Learning was predicted to be greater with feedback, and to increase overnight. Age was hypothesised to have no influence on outcome, and finally, those with shorter periods of bilateral loss preimplant were predicted to improve more. Experimental design: Nine adult unilateral cochlear implant users participated in the study. Ages ranged from 53 to 77 years, and time of binaural loss pre-implant, from nine months to 68 years. Participants were divided into two groups for auditory visual only, or auditory visual with feedback training conditions. There were five training sessions (~50 mins) and a pre- and post-training assessment session. The experimental set-up consisted of a seven loudspeaker array, forming a 135˚ front-horizontal plane arc. Training stimuli were white noise, spatially and temporally matched with red light-emitting diodes, and visual feedback („Yes‟,‟No‟) was displayed on a monitor screen. Generalisation testing was completed with untrained stimuli (words) in the pre- and post-training assessments. Results: Findings showed significantly improved auditory only localisation performance for both training and generalisation stimuli. Feedback had no effect on outcome. There was no significant effect of overnight consolidation on general localisation learning, however, graphical depictions revealed a pattern of overnight improvement, in the localisation of presentations ipsilateral to the implanted ear. There was no effect of age on performance, with participants improving irrespective of age. Those with three years or less, binaural loss pre-implant, showed greater improvements in exact accuracy word localisation, but there was no difference seen in localising the training noise. Conclusions: Adult unilateral cochlear implant recipients can increase their horizontal plane localisation ability after less than five hours of audiovisual training, and crucially, this learning can generalise to untrained stimuli. Furthermore, improvements are seen across a range of ages, hearing loss histories, and CI experience.