Garcia Lazaro, H. G. | bioRxiv Science

bioRxiv2025

Neural and behavioral correlates of evidence accumulation in human click-based echolocation

Echolocation enables blind individuals to perceive and navigate their environment by emitting clicks and interpreting their returning echoes. While expert blind echolocators demonstrate remarkable spatial accuracy, the behavioral and neural mechanisms supporting the temporal integration of spatial echoacoustic cues remain less explored. Here, we investigated the temporal dynamics of spatial information accumulation in human click-based echolocation using EEG. Blind expert echolocators and novice sighted participants localized virtual spatialized echoes derived from realistic synthesized mouth clicks, with trials presenting trains of 2-11 clicks. Behavioral results showed that blind expert echolocators significantly outperformed sighted controls in spatial localization. For these experts, localization thresholds decreased with more clicks, indicating cumulative integration of spatial cues across repeated samples. EEG decoding analyses revealed that neural representations significantly distinguished echo laterality and predicted overall spatial localization performance from the first click alone. Additionally, brain responses relative to the first click evolved systematically over successive clicks, paralleling psychophysical performance in blind echolocators and providing a possible index of perceptual information accumulation. These findings provide, to our knowledge, the first fine-grained account of temporal neural dynamics underlying click-based echolocation, directly linked to behavioral performance over multiple samples. They reveal how successive echoes are integrated over time into coherent spatial representations. Together, these results advance our understanding of the perceptual and neural mechanisms underlying echolocation and demonstrate adaptive sensory processing in the absence of vision.

neuroscience↗

bioRxiv2024

Sensory and perceptual decisional processes underlying the perception of reverberant auditory environments

Reverberation, a ubiquitous feature of real-world acoustic environments, exhibits statistical regularities that human listeners leverage to self-orient, facilitate auditory perception, and understand their environment. Despite the extensive research on sound source representation in the auditory system, it remains unclear how the brain represents real-world reverberant environments. Here, we characterized the neural response to reverberation of varying realism by applying multivariate pattern analysis to electroencephalographic (EEG) brain signals. Human listeners (12 male and 8 female) heard speech samples convolved with real-world and synthetic reverberant impulse responses and judged whether the speech samples were in a "real" or "fake" environment, focusing on the reverberant background rather than the properties of speech itself. Participants distinguished real from synthetic reverberation with [~]75% accuracy; EEG decoding reveals a multistage decoding time course, with dissociable components early in the stimulus presentation and later in the peri-offset stage. The early component predominantly occurred in temporal electrode clusters, while the later component was prominent in centro-parietal clusters. These findings suggest distinct neural stages in perceiving natural acoustic environments, likely reflecting sensory encoding and higher-level perceptual decision-making processes. Overall, our findings provide evidence that reverberation, rather than being largely suppressed as a noise-like signal, carries relevant environmental information and gains representation along the auditory system. This understanding also offers various applications; it provides insights for including reverberation as a cue to aid navigation for blind and visually impaired people. It also helps to enhance realism perception in immersive virtual reality settings, gaming, music, and film production. SIGNIFICANCEIn real-world environments, multiple acoustic signals coexist, typically reflecting off innumerable surrounding surfaces as reverberation. While reverberation is a rich environmental cue and a ubiquitous feature in acoustic spaces, we do not fully understand how our brains process a signal usually treated as a distortion to be ignored. When asking human participants to make perceptual judgments about reverberant sounds during EEG recordings, we identified distinct, sequential stages of neural processing. The perception of acoustic realism first involves encoding low-level reverberation acoustic features and their subsequent integration into a coherent environment representation. This knowledge provides insights for enhancing realism in immersive virtual reality, music, and film production, and using reverberation to guide navigation for blind and visually impaired people.

neuroscience↗