Social information as an entrainment cue for the circadian clock.

Animals adapt to the daily changes in their environmental conditions by means of genetically encoded circadian clocks. These clocks, found throughout the tree of life, regulate diverse biological functions, and allow periodical changes in physiology and behaviour. The molecular underpinnings of these clocks have been extensively studied across taxa, revealing a brain-based system that coordinates rhythmic activities through neuronal networks and signalling pathways. Entrainment, the alignment of internal rhythms with external cues or zeitgebers, is crucial for the adaptive value of these internal clocks. While the solar light-dark cycle is a primary zeitgeber for most animals, other relevant cues such as temperature, meal timing, predators, anxiety, fear, physical activity, and social interactions also play roles in entraining circadian clocks. The search of a detailed description of the circadian clocks is a goal for neurobiology and an area of growing societal interests. Moreover, as disruptions in circadian rhythms are implicated in various diseases, understanding the entrainment pathways contributes to developing interventions for improved wellbeing and health outcomes. This review focuses on socially relevant cues, examining their impact on animal physiology and behaviour, and explores the sensory pathways transmitting information to the central clock.