Brains are not purely stimulus–response machines; instead, behavior is profoundly shaped by internal states—hidden, temporally persistent variables that modulate how sensory inputs are processed and transformed into behavioral output. These hidden processes include, for instance, arousal, motivation, attention, affect, and homeostatic drives, and integrate information from the external environment and physiological conditions into centralized brain states that orchestrate behavior and physiology (Marques, …, Li 2019). A central challenge is that the same behavioral output can arise from different internal conditions, and conversely, the same sensory input can lead to different actions depending on an organism’s internal state—especially in naturalistic and ecological settings where task epochs and experimenter-defined labels are absent (Gupta et al. 2024). Signatures of such internal processes are often studied with diverse terminologies: “internal states” in systems neuroscience, “internal values or decisions” in ecological approaches to neuroscience, or “internal cognitive processes” in cognitive neuroscience. In this workshop, we will reconcile these parallel perspectives, establishing shared definitions and benchmarks, and fostering collaboration between experimental and theoretical communities working on different facets of internal states in the brain and behavior. In this workshop, we will mainly focus on two approaches to internal state: (1) Naturalistic behavioral and physiological readouts. Internal states are inferred from changes in movement kinematics, engagement, exploration/exploitation structure, and multimodal neurophysiological signals. (2) Neural population dynamics, where internal states manifest as low-dimensional manifolds, attractors, or transitions between input-driven and autonomous regimes. By bringing these perspectives together, we will aim to define common principles, evaluation criteria, and open challenges for identifying internal states across neural systems.
References:
Marques, J. C., Li, M., Schaak, D., Robson, D. N., & Li, J. M. (2020). Internal state dynamics shape brainwide activity and foraging behaviour. Nature, 577(7789), 239-243.
Gupta, D., DePasquale, B., Kopec, C. D., & Brody, C. D. (2024). Trial-history biases in evidence accumulation can give rise to apparent lapses in decision-making. Nature communications, 15(1), 662.