How Salient Sensory Stimuli Induce Brain-Wide State Alterations

The brain is a highly integrated organ, capable of dynamically adjusting its internal states through interactions with the ever-changing environment. This moment-to-moment control underlies the process from sensory perception to behavioral output, reflecting the essence of biological intelligence. However, the broad and ambiguous concept of "brain state" poses challenges for unifying research findings and deciphering the neural logic underlying sensory-induced state changes. Here, we focus on arousal-an essential and quantifiable dimension of brain state-which we further subdivide into general arousal and behavior-relevant specific arousal. Building on recent advances, we examine how salient sensory stimuli rapidly drive state transitions to promote adaptive behavior. We further highlight conserved features shared across subcortical sensory systems and provide an abstract framework for how distinct systems couple sensory input to arousal levels. This perspective clarifies mechanisms underlying behavioral flexibility and sensory consciousness, offering a unified framework for interpreting diverse findings in the field.