Adaptation to artificial associations between low-level visual and auditory features

David Wozny, UCLA NeuroEngineering

Abstract
Sensory plasticity in adulthood is characterized as being very limited, however some flexibility, even in low-level perceptual processing, remains. The McGurk and Ventriloquist aftereffects are demonstrations of this flexibility. The aim of this study was to discover if 1.) audio-visual pairings can influence sensitivity to low-level visual processing (as compared to subjective perception in other effects), and, 2.) visual perception can be altered by exposure to audio-visual stimuli that are not naturally correlated in the environment (e.g., tone-frequency and visual angle-of-orientation). METHODS: The experiment consisted of two test sessions with an intervening adaptation period. In tests, a 2IFC protocol evaluated subjects’ detection of oriented sinusoidal circular gratings that were spatially masked in white noise. In a given trial, the target interval could contain one of two orientations (O1=45°, or O2=135°) and was presented either in silence or paired with one of two tones (T1= 350Hz, or T2= 925Hz). During exposure, subjects were passively exposed to two types of trials: a 45° oriented grating paired with a 350Hz tone (O1T1), and a 135° oriented grating paired with no sound (O2), randomly interleaved. RESULTS: Exposure caused a relative increase in performance and relative decrease in reaction time for the exposed pairing O1T1 compared to O1 and O2T1 conditions. CONCLUSIONS: These results show that adaptation to a coupled auditory stimulus can facilitate delectability of the visual stimulus, specific to the exposed feature pairing. This suggests that auditory and visual stimuli are integrated at an early stage of visual processing, and that low-level AV features can be acquired even in adulthood.

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