Accommodating to new ears: The effects of sensory and sensory-motor feedback

Abstract

Changing the shape of the outer ear using small in-ear molds degrades sound localization performance consistent with the distortion of monaural spectral cues to location. It has been shown recently that adult listeners re-calibrate to these new spectral cues for locations both inside and outside the visual field. This raises the question as to the teacher signal for this remarkable functional plasticity. Furthermore, large individual differences in the extent and rate of accommodation suggests a number of factors may be driving this process. A training paradigm exploiting multi-modal and sensory-motor feedback during accommodation was examined to determine whether it might accelerate this process. So as to standardize the modification of the spectral cues, molds filling 40% of the volume of each outer ear were custom made for each subject. Daily training sessions for about an hour, involving repetitive auditory stimuli and exploratory behavior by the subject, significantly improved the extent of accommodation measured by both front-back confusions and polar angle localization errors, with some improvement in the rate of accommodation demonstrated by front-back confusion errors. This work has implications for both the process by which a coherent representation of auditory space is maintained and for accommodative training for hearing aid wearers.

From ear to body: the auditory-motor loop in spatial cognition

“…More recently, the role of sensorimotor calibration of audition emerges as very significant (Aytekin et al, 2008; Boyer et al, 2013; Carlile and Blackman, 2013; Carlile et al, 2014). Here we provide data attesting that when humans can use sensorimotor information, their spatial map of an auditory space is very accurate.…”

Short-term effects of sound localization training in virtual reality

“…It is now well established that the adult human brain can adapt to altered cues for sound direction. This has been demonstrated in studies using ear plugs 36,38 as well as molds inserted in the pinnae [16][17][18] . Some recent studies have also demonstrated a learning effect using visual positional feedback delivered via a head-mounted display.…”

“…There is increasing evidence that the adult brain is more adaptable than classically thought 15 . For example, it has been demonstrated that this adaptability (or plasticity) can lead to a decrease in localization error over time when a listener's normal cues for sound location are disrupted by physically altering the shape of the ear using molds [16][17][18] . However, this process typically takes place over the course of days or weeks (for a review see Mendonça et al 19 ).…”

Localization Experiments with Reporting by Head Orientation: Statistical Framework and Case Study

“…A large variety of characteristics have been studied, ranging from the just-noticeable-differences in localization accuracy, adaptation, and learning effects, to the influence of the source's spectral content and room reflections [1][2][3]. Recent experiments also studied the contribution of high frequency content in the presence of a noise masker [4], the degradation of localization accuracy with outer ears occlusions [5] and bilateral hearing aids [6], and the localization of multiple coherent sound sources [7].…”

“…Subjects are typically asked to indicate the direction of the perceived sound source by (a) reporting the closest loud-speaker, fixed acoustic pointer or label [7,4,2]; (b) steering a movable pointer [8]; (c) reporting the direction on a graphical user interface (GUI) or on paper [6]; or (d) turning their face toward the perceived sound source after the stimulus has been presented [9,5]. This paper is concerned with experiments where subjects report the position of the perceived sound source by turning toward it while the stimulus is being presented.…”