Biology subjects

Blank, H.

Publications and source records attributed to Blank, H..

5 recordsLinked to original sources

bioRxiv2026

The Influence of Prior Precision on the Inference of Hidden Causes

Perception is widely understood as Bayesian inference, integrating prior expectations with sensory evidence to infer the most probable latent cause of a signal. A common assumption holds that precise priors dominate perception by pulling it strongly toward their mean. However, in hierarchically structured contexts where multiple latent causes compete, Bayesian inference predicts the opposite: imprecise priors can dominate perception under sensory uncertainty. We show that human observers exhibit this counterintuitive bias in an ecologically valid scenario of voice recognition: when classifying ambiguous utterances, observers preferentially attributed them to lower-precision (higher-variance) voice priors. This bias was strongest under high sensory ambiguity and increased with explicit knowledge of prior variance. Computational modeling revealed stable, idiosyncratic prior distributions, suggesting inference operates over hierarchically structured representations of voice identity. These findings identify prior precision as a key determinant of perceptual inference under competing priors.

neuroscience↗

bioRxiv2026

Expectation Consecutively boosts Neural Processing of Expected and Unexpected Visual Information

This electroencephalography (EEG) study provides evidence that expectations dynamically shape visually evoked brain responses through a biphasic temporal mechanism: an earlier enhancement of expected image components, followed by a later prioritization of unexpected components. Across six sessions each, six participants were presented with a deterministic sequence of four images with intermixed composite trials that contained both the expected and the unexpected image. To quantify expected and unexpected identity information over time, we applied Linear Discriminant Analysis. The observed temporal dissociation suggests that the brain initially integrates sensory input with prior expectations in a Bayesian manner before shifting to emphasize surprising information, thereby supporting both efficient recognition and adaptive model updating. Furthermore, expectations affected superordinate image processing (animal vs. non-animal), showing the same pattern as identity processing, with earlier enhancement of expected information followed by a prioritization of surprising information.

neuroscience↗

bioRxiv2025

Sensory sharpening and semantic prediction errors unify competing models of predictive processing in communication

The human brain makes abundant predictions in speech comprehension that, in real-world conversations, depend on conversational partners. Yet, tested models of predictive processing diverge on how such predictions are integrated with incoming speech: The brain may emphasise either expected information through sharpening or unexpected information through prediction error. We reconcile these views through direct neural evidence from electroencephalography showing that both mechanisms operate at different hierarchical levels during speech perception. Across multiple experiments, participants heard identical ambiguous speech in different speaker contexts. Using speech decoding, we show that listeners learn speaker-specific semantic priors, which sharpen sensory representations by pulling them toward expected acoustic signals. In contrast, encoding models leveraging pretrained transformers reveal that prediction errors emerge at higher linguistic levels. These findings support a unified model of predictive processing, wherein sharpening and prediction errors coexist at distinct hierarchical levels to facilitate both robust perception and adaptive world models.

neuroscience↗

bioRxiv2021

Visual speech is processed differently in auditory and visual cortex: evidence from MEG and partial coherence analysis

Speech perception in noisy environments is enhanced by seeing facial movements of communication partners. However, the neural mechanisms by which audio and visual speech are combined are not fully understood. We explore MEG phase locking to auditory and visual signals in MEG recordings from 14 human participants (6 females, 8 males) that reported words from single spoken sentences. We manipulated the acoustic clarity and visual speech signals such that critical speech information is present in auditory, visual or both modalities. MEG coherence analysis revealed that both auditory and visual speech envelopes (auditory amplitude modulations and lip aperture changes) were phase-locked to 2-6Hz brain responses in auditory and visual cortex, consistent with entrainment to syllable-rate components. Partial coherence analysis was used to separate neural responses to correlated audio-visual signals and showed non-zero phase locking to auditory envelope in occipital cortex during audio-visual (AV) speech. Furthermore, phase-locking to auditory signals in visual cortex was enhanced for AV speech compared to audio-only (AO) speech that was matched for intelligibility. Conversely, auditory regions of the superior temporal gyrus (STG) did not show above-chance partial coherence with visual speech signals during AV conditions, but did show partial coherence in VO conditions. Hence, visual speech enabled stronger phase locking to auditory signals in visual areas, whereas phase-locking of visual speech in auditory regions only occurred during silent lip-reading. Differences in these cross-modal interactions between auditory and visual speech signals are interpreted in line with cross-modal predictive mechanisms during speech perception. Significance StatementVerbal communication in noisy environments is challenging, especially for hearing-impaired individuals. Seeing facial movements of communication partners improves speech perception when auditory signals are degraded or absent. The neural mechanisms supporting lip-reading or audio-visual benefit are not fully understood. Using MEG recordings and partial coherence analysis we show that speech information is used differently in brain regions that respond to auditory and visual speech. While visual areas use visual speech to improve phase-locking to auditory speech signals, auditory areas do not show phase-locking to visual speech unless auditory speech is absent and visual speech is used to substitute for missing auditory signals. These findings highlight brain processes that combine visual and auditory signals to support speech understanding.

neuroscience↗

bioRxiv2020

Can expectation suppression be explained by reduced attention to predictable stimuli?

The expectation-suppression effect - reduced stimulus-evoked responses to expected stimuli - is widely considered to be an empirical hallmark of reduced prediction errors in the framework of predictive coding. Here we challenge this notion by proposing that that expectation suppression could be explained by a reduced attention effect. Specifically, we argue that reduced responses to predictable stimuli can also be explained by a reduced saliency-driven allocation of attention. We base our discussion mainly on findings in the visual cortex and propose that resolving this controversy requires the assessment of qualitative differences between the ways in which attention and surprise enhance brain responses.

neuroscience↗