Biology subjects

Guest, D. R.

Publications and source records attributed to Guest, D. R..

4 recordsLinked to original sources

bioRxiv2025

A computational model of the mammalian auditory periphery with a multichannel, energy-driven, medial olivocochlear reflex

The afferent auditory system, and how its specialized mechanisms and circuits support ecologically relevant auditory computations such as speech recognition, has received considerable attention in decades past. This work has culminated in accurate computational models of early afferent coding alongside a good understanding of how low-level mechanisms (e.g., peripheral tuning) impact auditory perception. In contrast, the auditory efferent system and its role in auditory perception is much less well understood. To address this gap in knowledge, we describe modifications to a model of the auditory periphery to include a medial olivocochlear efferent pathway that dynamically adjusts cochlear gain in response to sound via the classical medial olivocochlear reflex loop. We show that this model can simulate the effects of contralateral elicitors on auditory-nerve responses, including the effect of elicitors that are tonotopically distant from probes. Inclusion of across-frequency efferent effects necessitated a novel multichannel design.

neuroscience↗

bioRxiv2025

Dissociating the neural codes for multiple pitch perception in humans

Pitch is crucial for speech and music perception, yet its neural code remains contested. The classic rate-place theory suggests that pitch is computed from spatial patterns of average neural firing rates along the cochlear tonotopic axis. These cues are thought to be robust for isolated harmonic complex tones (HCTs) but degraded for spectrally dense mixtures of simultaneous HCTs (e.g., musical chords) due to auditory filtering. In many cases, pitch perception remains feasible for HCT mixtures, but it is unclear whether listeners utilize residual rate-place cues or alternative neural codes. To adjudicate between these possibilities, we generated rate-place metamers (META), which are synthetic stimuli with simulated auditory-nerve average-rate responses that are nearly identical to those of original pitch-evoking stimuli (ORIG). Using these stimuli, listeners completed four psychophysical experiments that spanned a wide range of acoustic and cognitive complexity, from single-HCT pitch discrimination to harmonic-expectation judgments. Combining the behavioral data with predictive models of listener performance, we found that listener performance on single pitch discrimination tasks could be adequately explained by a rate-place model, with or without simultaneous pitch maskers (Experiments 1 and 2). More complex tasks involving attention to all pitches in a three-pitch mixture (Experiments 3 and 4) showed a pattern of results more difficult to account for with a rate-place model, perhaps suggesting a role for integration of temporal cues. Significance StatementEveryday listening typically involves parsing or integrating several simultaneous pitches, for example, while listening to music or conversations in noisy environments, rather than hearing a single, isolated pitch. Despite their ubiquity, the neural mechanisms for encoding multiple pitches are not well understood, which partly explains the limitations of modern assistive listening devices in noisy settings. To address this, we developed model-based synthetic stimuli to measure how distinct pitch cues contribute to pitch perception. This approach advances our understanding of the neural basis of music perception, with a goal of informing the design of more effective hearing prostheses.

neuroscience↗

bioRxiv2025

Hierarchical Processing of Natural Scenes in the Human Pulvinar

The hierarchical organization of the ventral visual cortex has been the focus of theories and computational models characterizing high-level visual processing and object recognition, often overlooking potential contributions of subcortical structures. The pulvinar, through its extensive reciprocal connections with ventral visual cortex, is well-positioned to play a prominent role in high-level visual recognition processes. Here, we investigated whether the pulvinar plays such a role using a high-resolution 7T fMRI dataset of responses to tens of thousands of natural scenes. Encoding models testing the representation of different stimulus features revealed a pulvinar region selective for bodies and faces presented within the contralateral visual hemifield. Model-free analyses demonstrated that this region is predominantly co-active with body- and face-selective cortical areas during natural scene viewing. This functional specificity was embedded within a broader gradient of cortical correlations across the pulvinar mirroring the hierarchical organization of ventral visual cortex. These findings challenge cortico-centric models of object vision and implicate a role of the pulvinar in high-level vision. More broadly, these results demonstrate that principles of cortical organization, including functional clustering and hierarchical organization, also manifest in subcortex, and highlight the value of using naturalistic stimuli to probe visual function.

neuroscience↗

bioRxiv2023

A fast and flexible approximation of power-law adaptation for auditory computational models

1.Power-law adaptation is a form of neural adaptation that has been shown to provide a better description of auditory-nerve adaptation dynamics as compared to simpler exponential-adaptation processes. However, the computational costs associated with power-law adaptation are high and, problematically, grow superlinearly with the number of samples in the simulation. This cost limits the applicability of power-law adaptation in simulations of responses to relatively long stimuli, such as speech, or in simulations for which high sampling rates are needed. Here, we present a simple approximation to power-law adaptation based on a parallel set of exponential-adaptation processes with different time constants, demonstrate that the approximation improves on an existing approximation provided in the literature, and provide updates to a popular phenomenological model of the auditory periphery that implements the new approximation.

neuroscience↗