Evidence that respiratory phase may modulate task-related neural representations of visual stimuli

We investigate how respiration influences cognition by examining the interaction between respiratory phase and task-related brain activity during two visual categorization tasks. While prior research shows that cognitive performance varies along the respiratory cycle, the underlying neurophysiological mechanisms remain poorly understood. Though some studies have shown that large-scale neural activity reflecting for example changes in the excitation-inhibition balance is co-modulated with the respiratory cycle, it remains unclear whether respiration directly shapes the neural signatures reflecting the encoding of task-specific external signals. We address this gap by applying single-trial multivariate analyses to EEG data obtained in humans (n=25, any gender), allowing us to track how respiration relates to the sensory evidence reflected in this neurophysiological signal. Confirming previous studies, our data show that participant's performance varies with the respiratory phase prior and during a trial. Importantly, they suggest that respiration may directly influence the sensory evidence carried by neurophysiological processes emerging around 300 to 200 ms prior to participant's responses. Hence, respiration and sensory-cognitive processes are not only highly intertwined but respiration may directly facilitate the representation of behaviourally-relevant signals in the brain. Significance statement Performance in perceptual-cognitive tasks can fluctuate along the respiratory cycle. Previous work supports this by demonstrating the entrainment of neural activity to the respiratory rhythm. Yet, it remains unclear whether respiration also directly shapes the fidelity of task-related neural representations. We here investigate this based on EEG recordings in human volunteers performing visual categorization tasks. Using multivariate decoding we provide evidence that respiration may modulate decision-related neural signatures of the visual stimuli in a manner predictive of behavioral performance. These results strengthen a direct connection between the respiratory rhythm and sensory-cognitive processes, underscoring the role of bodily rhythms in shaping behavior.