Histamine interferes with the early visual processing in mice

Sensory processing is dynamically modulated by an animal's behavior and internal states. Growing evidence suggests that such modulation starts from early stages, even at the retina, but the underlying mechanisms remain elusive. Combining pharmacological and chemogenetic tools with single-unit extracellular recordings in awake head-fixed mice, here we identified that the visual responses of retinal ganglion cells and the lateral geniculate nucleus were both made weaker and slower by histaminergic projections from the tuberomammillary nucleus of the posterior hypothalamus. The observed changes in the visual responses were, however, not directly linked with histaminergic modulation of pupil dynamics or locomotion behavior. Our computational modelling analysis instead suggests neuronal circuit effects, such as gain modulation via the histamine H1 receptors in the retina. As nocturnal animals, facilitation of visual processing at low histamine level is ethologically beneficial for mice to respond faster to visual threats when animals are less active during daytime.