Comparison of auditory stream segregation in sighted and early blind individuals

Abstract

An important characteristic of the auditory system is the capacity to analyze complex sounds and make decisions on the source of the constituent parts of these sounds. Blind individuals compensate for the lack of visual information by an increase input from other sensory modalities, including increased auditory information. The purpose of the current study was to compare the fission boundary (FB) threshold of sighted and early blind individuals through spectral aspects using a psychoacoustic auditory stream segregation (ASS) test. This study was conducted on 16 sighted and 16 early blind adult individuals. The applied stimuli were presented sequentially as the pure tones A and B and as a triplet ABA-ABA pattern at the intensity of 40dBSL. The A tone frequency was selected as the basis at values of 500, 1000, and 2000Hz. The B tone was presented with the difference of a 4-100% above the basis tone frequency. Blind individuals had significantly lower FB thresholds than sighted people. FB was independent of the frequency of the tone A when expressed as the difference in the number of equivalent rectangular bandwidths (ERBs). Early blindness may increase perceptual separation of the acoustic stimuli to form accurate representations of the world.

Keywords: Auditory stream segregation; Blindness; Compensation; Equivalent rectangular bandwidths; Fission boundary threshold; Plasticity.