Biology subjects

Brimijoin, W. O.

Publications and source records attributed to Brimijoin, W. O..

4 recordsLinked to original sources

bioRxiv2025

Sound source history warps perceived azimuth and elevation

In real-world auditory localization, humans make decisions based on acoustic cues that reach the ear as well as from expectations of where the sound may originate. Past studies have shown that the auditory system makes rapid adjustments in response to changes in the statistics of recent stimulation, which help maintain sensitivity over the range where most stimuli occur. In the current study, we explored the auditory systems adaptability and plasticity by presenting sounds in different spatial contexts and examined the subsequent effects on sound localization accuracy. Identical sounds were rendered at different azimuth and elevation ranges of [-15{degrees}, -30{degrees}, 0{degrees}] or [15{degrees}, 30{degrees}, 0{degrees}] presented in contextual blocks. Sounds presented at 0{degrees} azimuth exhibited a rightward shift in perception when the targets were blocked within the left hemispace, and a leftward shift when targets were blocked in the right hemispace. Sounds that were blocked in the bottom hemispace showed an upward bias in perceived elevation, although the reverse was not found to be significant. Furthermore, participants who showed more errors in overall localization showed a higher degree of bias. Our results corroborate the account that the mapping of auditory space is dynamic and shifts depending on the context in which sounds are presented.

neuroscience↗

bioRxiv2020

Speech intelligibility with various head-related transfer functions: A computational modeling approach

Speech intelligibility is known to be affected by the relative spatial position between target and interferers. The benefit of a spatial separation is, along with other factors, related to the head-related transfer function (HRTF). The HRTF is individually different and thus, the cues that improve speech intelligibility might also be different. In the current study an auditory model was employed to predict speech intelligibility with a variety of HRTFs. The predicted speech intelligibility was found to vary across HRTFs. Thus, individual listeners might have different access to cues that are important for speech intelligibility.

neuroscience↗

bioRxiv2017

The Equivalent Arc Ratio For Auditory Space

The minimum audible movement angle increases as a function of source azimuth. If listeners do not perceptually compensate for this change in acuity, then sounds rotating around the head should appear to move faster at the front than at the side. We examined whether judgments of relative amounts of acoustic motion depend on signal center angle and found that the azimuth of two signals strongly affects their point of subjective similarity for motion. Signal motion centered at 90{degrees} had to be roughly twice as large as motion centered at 0{degrees} to be judged as equivalent. This distortion of acoustic space around the listener suggests that the perceived velocity of moving sound sources changes as a function of azimuth around the head. The \"equivalent arc ratio,\" a mathematical framework based on these results, is used to successfully provide quantitative explanations for previously documented discrepancies in spatial localization, motion perception, and head-to-world coordinate transformations.

neuroscience↗

bioRxiv2017

Egocentric and Allocentric Representations in Auditory Cortex

A key function of the brain is to provide a stable representation of an objects location in the world. In hearing, sound azimuth and elevation are encoded by neurons throughout the auditory system and auditory cortex is necessary for sound localization. However the coordinate frame in which neurons represent sound space remains undefined: classical spatial receptive fields in head-fixed subjects can be explained either by sensitivity to sound source location relative to the head (egocentric) or relative to the world (allocentric encoding). This coordinate frame ambiguity can be resolved by studying freely moving subjects and here we recorded spatial receptive fields in auditory cortex freely moving ferrets. We found two distinct populations of neurons: While the majority ([~]80%) of spatially tuned neurons represented sound source location relative to the head, we provide novel evidence for a group of neurons in which space was represented in an allocentric world-centered coordinate frame. We also use our ability to measure spatial tuning in moving subjects to explore the influence of sound source distance and speed of head movements on auditory cortical activity and spatial tuning. Modulation depth of spatial tuning increased with distance for egocentric but not allocentric units, whereas for both populations modulation was stronger at faster movement speeds. Our findings argue that auditory cortex is involved in the representation of both sound source location relative to ourselves and sound location in the world independent of our own position.

neuroscience↗