Abstract
Purpose: The integration of information across sensory modalities allows us to create a meaningful, unified percept of events in the world. Although the development of cross-modal integration has been studied previously, most studies have focused on higher-level visual and auditory stimuli, or on the spatial and/or temporal constraints on integrating lower-level sensory stimuli. Here we investigate whether auditory cues can influence the detection of a near-threshold visual stimulus.
Methods: We used a forced choice-preferential looking paradigm to obtain contrast detection thresholds for a visual stimulus (a square subtending 11×11 degrees of visual angle, centered 15 degrees to the left or right of monitor center). The luminance of the visual stimulus fluctuated at 1Hz under three auditory conditions: (1) In-Phase (IP). The visual stimulus fluctuated in-phase with an auditory stimulus (white noise, presented bilaterally) fluctuating in loudness at 1 Hz, (2) Out-of-Phase (OP). The visual stimulus fluctuated out-of-phase with the same auditory stimulus, or (3) No Sound (NS). The visual stimulus was presented with no concurrent auditory stimulus. Visual stimulus contrast (3–100%) was randomized across trials. Threshold was defined as the contrast yielding 75% correct performance (where correct indicates that infants looked to the monitor side containing the visual stimulus). For each subject, visual contrast thresholds were obtained for two of the three possible conditions (IP, OP, NS). If the presence of synchronized auditory information enhances visual detection, we expect lower contrast thresholds for the IP versus the OP or NS condition. The converse would be true if synchronized auditory information hinders visual detection.
Results: In 6-month-old infants thresholds were higher for the IP condition, suggesting that synchronized auditory information may diminish visual detectability. Furthermore, our findings suggest that for low-level sensory processing, infants may have a limited capacity for attending information in more than one modality at a given time.
The Kavli Institute for Brain and Mind Innovative Research Award.