Linking global state fluctuations and recurrent processing to conscious perception in humans

Abstract: The term “consciousness” generally refers to two related aspects. Arousal (or wakefulness) reflects the organism’s overall global state, being awake, asleep, or in a coma, while conscious experience refers to the subjective contents of our awareness. Although generally thought to be strongly related, research studying both aspects and how they interact is rare. In this talk I will first focus on how fluctuations in arousal affect our perception and then on the neural mechanisms underlying subjective experience. I will show that perception is optimal at intermediate levels of pupil-linked arousal and declines at very low or high arousal states. Catecholaminergic enhancement shifted this arousal–performance curve (whereas cholinergic enhancement did not), revealing that the relationship between arousal and perception is adaptive. “Adaptive arousal regulation” likely reflects a global regime shift in arousal tuning, indicating that the brain may recalibrate perception to relative rather than absolute levels of arousal (Beerendonk et al., PNAS 2024, 2025). In the second part of this talk, I will turn to recurrent processing, the iterative exchange of information between higher- and lower-level cortical areas that supports perceptual inference. We show that recurrent processing is crucial for perceptual integration (the processing illusory Kanizsa figures), that it is strongly reduced by masking but less by inattention, and that NMDA receptor blockade selectively affects recurrent processing, while sparing feedforward driven early feature processing (Noorman et al., eLife 2025a/b). Together, these findings highlight how global arousal states affect conscious perception, and how recurrent interactions are crucial for conscious perception in the human brain.