The power of vision: calibration of auditory space after sight restoration from congenital cataracts

Abstract

Early visual deprivation typically results in spatial impairments in other sensory modalities. It has been suggested that, since vision provides the most accurate spatial information, it is used for calibrating space in the other senses. Here we investigated whether sight restoration after prolonged early onset visual impairment can lead to the development of more accurate auditory space perception. We tested participants who were surgically treated for congenital dense bilateral cataracts several years after birth. In Experiment 1 we assessed participants' ability to understand spatial relationships among sounds, by asking them to spatially bisect three consecutive, laterally separated sounds. Participants performed better after surgery than participants tested before. However, they still performed worse than sighted controls. In Experiment 2, we demonstrated that single sound localization in the two-dimensional frontal plane improves quickly after surgery, approaching performance levels of sighted controls. Such recovery seems to be mediated by visual acuity, as participants gaining higher post-surgical visual acuity performed better in both experiments. These findings provide strong support for the hypothesis that vision calibrates auditory space perception. Importantly, this also demonstrates that this process can occur even when vision is restored after years of visual deprivation.

Keywords: auditory localization; congenital cataracts; cross-sensory calibration; sight recovery; visual deprivation.

Figure 1.

Auditory space bisection. (a) Apparatus. (b) Psychometric function in one representative participant for each group. Curves are fitted on the proportion of ‘probe closer to the right sound’, plotted against the probe's position (with negative/positive values indicating probe closer to the left/right sound, respectively). (c) JNDs for the auditory bisection task in the different groups (eight Blind, seven Pre-op, 16 Post-op, 30 Sighted), as estimated from the GLMM on the whole sample, with lower JNDs indicating better performance. (d) Factors potentially contributing to task performance in Post-op (visual acuity, time since surgery, age at test). Individual JNDs are estimated with a GLM in each participant. Asterisks represent statistical significance (at α = 0.05). (Online version in colour.)

Figure 2.

Auditory and visual localization in the frontal plane. (a) Performance in the auditory localization task (five Pre-op, 21 Post-op, 29 Sighted). For graphical representations, results are summarized by averaging targets' positions and participants’ endpoint locations along azimuth (x-axis) and elevation (y-axis) in nine different regions of the set-up (defined by the dashed lines). The nine regions were obtained by dividing the space for the analyses into nine equally sized regions: the central region was 25 cm wide and high (i.e. 12.5 cm in each direction from the centre). Since the stimuli were presented on average in a 75 cm diameter circle, each region was around 25 cm wide and high. The dark grey grid connects the averaged actual targets' positions. The magenta grid connects the averaged location of participants’ responses. The black arrows indicate the direction of the localization errors. The horizontal dashed lines indicate the boundaries of the different heights: upper (Up), middle (Mid) and lower (Low) (see electronic supplementary material for further analyses). (b) Results of the visual localization task for the three groups. (c) Absolute localization error (as linear distance between target and response) in the auditory condition averaged across participants in each group. (d) Correlation between visual acuity and localization error in the auditory condition in Post-op. (e) Absolute localization error in the visual condition averaged across participants in each group. (f) Correlation between visual acuity and localization error in the visual condition in Post-op. (g) Absolute localization error in the auditory condition in the different heights averaged across participants in each group. (h) Absolute localization error in the visual condition in the different heights averaged in each group. Error bars represent SEM. Asterisks represent statistical significance. (Online version in colour.)