Herche, J. L. | bioRxiv Science

bioRxiv2026

Individual variation in sound localization accuracy is correlated with the properties of eye movement-related eardrum oscillations (EMREOs)

Calibration of sound localization behavior in species with mobile eyes requires not only accurate visual input but also accurate oculomotor signals across the lifespan. The recent discovery of eye movement-related eardrum oscillations suggest that oculomotor signals may be incorporated into auditory processing at the level of the ear. One inference of this discovery is that individual variation in such signals might be correlated with individual variation in sound localization accuracy. Here, we tested this hypothesis in humans with normal hearing. We discovered that there is considerable variation in the accuracy of sound localization (here, saccades to sounds) even in normal individuals: median horizontal errors ranged from 2-6{degrees}, and median vertical errors could be as large as 36{degrees}. We separated the subject pool into groups with "good" performance (median vectorial error < 8{degrees}) vs "poor" performance (median vectorial error > 10{degrees}) and evaluated their respective EMREOs. The EMREOs differed across the two groups in both horizontal and vertical dimensions, in how saccade amplitude vs. initial eye position was encoded, and across time, with considerable individual variation in the "poor" group. These results are consistent with the interpretation that EMREOs are associated with underlying processes that ensure the accuracy of sound localization. HIGHLIGHTSO_LIThe accuracy of eye movements to look at sounds varied across individuals, with median errors spanning a greater than 10-fold range. This range is surprising given that the participants passed screening for normal hearing. C_LIO_LI"Good" vs "poor" sound localizers exhibited differences in their eye movement-related eardrum oscillations (EMREOs) C_LIO_LIEMREOs differed in both horizontal and vertical sensitivity, for both saccade amplitude and initial eye position, and the differences varied in timing with respect to saccade onset. C_LIO_LIWe interpret the results under the theory that poor sound localization may be a consequence of poor eye movement encoding, without which linking visual and auditory space is likely inaccurate. C_LI

neuroscience↗

bioRxiv2024

Visually-evoked activity and variable modulation of auditory responses in the macaque inferior colliculus

How multisensory cues affect processing in early sensory brain areas is not well understood. The inferior colliculus (IC) is an early auditory structure that is visually responsive (Porter et al. 2007; Bulkin and Groh 2012a, 2012b), but little is known about how visual signals affect the ICs auditory representation. We explored how visual cues affect both spiking and local field potential (LFP) activity in the IC of two monkeys performing a task involving saccades to auditory, visual, or combined audiovisual stimuli. We confirm that LFPs are sensitive to the onset of fixation lights as well as the onset of visual targets presented during steady fixation. The LFP waveforms evoked by combined audiovisual stimuli differed from those evoked by sounds alone. In single-unit spiking activity, responses were weak when visual stimuli were presented alone, but visual stimuli could modulate the activity evoked by sounds in a stronger way. Such modulations could involve either increases or decreases in activity, and whether increases or decreases were observed was variable and not obviously correlated with the responses evoked by visual or auditory stimuli alone. These findings indicate that visual stimuli shape the ICs auditory representation in flexible ways that differ from those observed previously in multisensory areas. New & NoteworthyWe find that the inferior colliculus, a primarily auditory brain area, displays distinct population-level responses to visual stimuli. We also find that visual cues can influence the auditory responses of individual neurons. Together, the results provide insight into how relatively early sensory areas may play a role in combining multiple sensory modalities to refine the perception of complex environments.

neuroscience↗