Christoph Kayser

Respiration is a unique physiological process that can operate automatically but can also be deliberately used to modulate the bodily state. Importantly, respiration is deeply intertwined with neural processes, influencing functions from arousal and attention to executive control. Although structured respiration (breathing practice) has been exploited for centuries, the immediate consequences of short periods of structured respiration for sensation and cognition remain poorly understood. The present explorative study examined how brief, 1‐min episodes of structured respiration affect respiration and performance in a subsequent sensory‐cognitive task. Across two experiments, participants engaged in structured breathing practices that manipulated either respiratory frequency (slow breathing vs. fast breathing) or the inhalation–exhalation ratio (short inspiration–long expiration and long inspiration–short expiration) prior to performing a visual emotion discrimination task. Immediately after breathing practice, participants' respiration deviated from their baseline: Each technique resulted in specific deviations of respiratory frequency, inhalation–exhalation ratio, or the occurrence of atypical respiratory cycles, suggesting technique‐specific returns to regular respiration. During the subsequent discrimination task response accuracy and reaction times did not differ between breathing practices. However, we observed transient changes in reaction times immediately following all practices, suggesting a brief facilitation of attentional or sensorimotor responsiveness following conscious breathing. Our findings indicate that even brief, consciously controlled respiration can transiently influence cognitive performance, highlighting the role of voluntary respiratory modulation in shaping brain function and behavior.

Recent studies describe Eye Movement-Related Eardrum Oscillations (EMREOs), low‑frequency signals recorded in the ear canal that arise from the tympanic membrane and are triggered by saccadic eye movements. Because EMREOs are thought to arise from motor elements in the peripheral auditory system, we examined how two known modulators of these elements affect the EMREO time course. First, the activity of outer hair cells (OHCs) can be suppressed by the medial olivocochlear reflex (MOCR). If OHCs contribute to the generation of EMREOs, activation of this reflex should reduce EMREO amplitude. To test this, we compared EMREO amplitudes elicited by saccades performed in silence and in the presence of contralateral noise. Second, postural (i.e., vestibular and proprioceptive) cues linked to head orientation may influence EMREOs via oculomotor control circuits that possibly modulate middle ear muscles. To test this, we recorded EMREOs while participants made saccades with their head upright (0° azimuth) and with their head tilted 30° in either direction. Across both experiments our data reveal no significant modulation of the EMREO by these experimental manipulations. Together with other recent studies these findings advocate for a stability of the EMREO towards multiple experimental modulations. We discuss how this fuels speculations that the signal may serve as a temporal reference frame, while also being compatible with the notion that the EMREO reflects a spatial coordinate transform for combining signals across the senses.

In this viewpoint, Christoph Kayser, Uta Noppeney, and Tim Rohe highlight the central role of normative Bayesian frameworks, in particular Bayesian causal inference, for explaining how the brain decides whether sensory signals should be integrated or segregated and how they are weighted by their reliabilities. In parallel, the Multisensory Correlation Detector model is emphasized as a mechanistic proposal for how the brain computes spatial and temporal relations across sensory channels. Together, these developments have shifted the field from merely locating multisensory processing in the brain to characterizing the specific computations implemented across cortical hierarchies. The authors outline current trends, such as model-based analyses of neuroimaging and neurophysiological data, increasing use of artificial neural networks to study multisensory processing at larger scales, and emerging work in naturalistic, real-world settings. They discuss ongoing controversies surrounding the influence of attention and tasks on multisensory integration, the limits of Bayes optimality, and the role of neural oscillations, especially alpha rhythms, in shaping multisensory binding. They further advocate for stronger open-science practices and systematic replication of influential findings to consolidate the empirical and theoretical foundations of the field. Finally, they encourage early-career scientists to develop strong methodological skills, cultivate their own conceptual ‘angle’, and actively engage with the multisensory community.

The perceptual interpretation of a static image, such as the Necker cube, can change spontaneously, resulting in endogenously driven changes in perception. We studied how different peripheral markers of the bodys physiological state, as well as time-resolved markers of EEG-derived brain activity, modulate around such spontaneous changes in perception. Specifically, we quantified the time course of heart rate, respiration rate, respiration phase, pupil size, EEG evoked responses, and EEG time-frequency activity around spontaneous perceptual reversals, and tested how these signals differ between the two interpretations of the Necker cube. Our results show that signals relating to the bodys and brains momentary state differ between the two perceptual interpretations, including pupil size, respiration phase, and rhythmic EEG activity. In contrast, signals relating to metabolic state or external stimuli, including respiration rate, heart rate and EEG evoked responses, did not differ between perceptual interpretations, but were consistently modulated around these. This corroborates the notion that spontaneous changes in perception are related to specific and coordinated windows in the cardiorespiratory cycle and neural markers of arousal or top-down processing. These windows are differentially expressed across interacting physiological systems, highlighting the intricate link between perception, brain activity and bodily physiology.

Recent studies describe Eye Movement-related Eardrum Oscillations (EMREOs), low-frequency signals recorded in the ear canal that arise from the tympanic membrane and are triggered by saccadic eye movements. Because EMREOs are thought to arise from motor elements in the peripheral auditory system, we examined how two known modulators of these elements affect the EMREO time course. First, the activity of outer hair cells (OHC) can be suppressed by the medial olivocochlear reflex (MOCR). If OHCs contribute to the generation of EMREOs, activation of this reflex should reduce EMREO amplitude. To test this, we compared EMREO amplitudes elicited by saccades performed in silence and in the presence of contralateral noise. Second, gravitational cues linked to head orientation may influence EMREOs via oculomotor control circuits that possibly modulate middle ear muscles. To test this, we recorded EMREOs while participants made saccades with their head upright (0 degrees azimuth) and with their head tilted 30 degrees in either direction. Across both experiments our data reveal no clear modulation of the EMREO time course by these experimental manipulations. Together with other recent studies these findings advocate for a stability of the EMREO time course towards multiple experimental modulations and fuel speculations that the signal may serve as a temporal reference frame when combining signals across the senses.

Eye movement-related eardrum oscillations (EMREOs) have intrigued auditory neuroscientists for the past couple of years, as their origin and function remain unclear. We probed whether the EMREO accurately represents eardrum movements by comparing sound lateralization performance in spatial discrimination tasks. However, we found no effects driven by EMREOs deflections magnitude and sign. This suggests that eardrum movements during saccades are not directly reflected by the EMREO signal.

Humans tend to align their respiration with important events, in line with the notion that respiration serves as a tool to allocate (neuro-)physiological resources. This respiration alignment is consistently reported in laboratory studies relying on sequences of stimulus-driven experimental trials. However, whether such respiration alignment also occurs in the absence of external cues - such as during spontaneous perceptual changes - remains unknown. However, pupil size is known to change around spontaneous changes in perception, and pupil size supposedly covaries with respiration phase, suggesting that indeed respiration may align to spontaneous changes in perception. We investigate the link between respiration, pupil size, and spontaneous perceptual changes while participants (n=21) reported spontaneous perceptual reversals while viewing an ambiguous Necker cube. We confirmed the biphasic modulation of pupil size around reversals (constriction followed by dilation) and the general variation of pupil size with respiration phase. However, this coupling of pupil size and respiration phase broke down around perceptual reversals. Crucially, our data reveal no clear alignment of respiration phase to perceptual reversals although respiration frequency was predictive of the perceptual stability duration. These findings suggest that the temporal predictability of external events is critical for the robust respiration alignment to cognitive events.

Respiration is a unique physiological process that can operate automatically but can also be deliberately used to modulate the bodily state. Importantly, respiration is deeply intertwined with neural processes, influencing processes from arousal and attention to executive control. Although structured respiration (breathing practice) has been exploited for centuries, the immediate consequences of short periods of structured respiration for sensation and cognition remain poorly understood. The present study examined how brief, one-minute episodes of structured respiration affect respiration and performance in a subsequent sensory-cognitive task. Across two experiments, participants engaged in structured breathing practices manipulating either respiratory frequency (slow breathing vs. fast breathing) or the inhalation-exhalation ratio (short inspiration-long expiration; long inspiration-short expiration) prior to performing a visual emotion discrimination task. Immediately after breathing practice, participant’s respiration deviated from their baseline: each technique resulted in specific deviations of respiratory frequency, inhalation-exhalation ratio, or the occurrence of atypical respiratory cycles, suggesting technique-specific returns to regular respiration. During the subsequent emotion response accuracy or reaction times did not differ between breathing practices. However, we observed transient improvements in reaction times immediately following all practices, suggesting a brief facilitation of attentional or sensorimotor responsiveness following conscious breathing. Our findings indicate that even brief, consciously controlled respiration can transiently influence cognitive performance, highlighting the role of voluntary respiratory modulation in shaping brain function and behavior.