Serotonin in Animal Cognition and Behavior

Abstract

Serotonin (5-hydroxytryptamine, 5-HT) is acknowledged as a major neuromodulator of nervous systems in both invertebrates and vertebrates. It has been proposed for several decades that it impacts animal cognition and behavior. In spite of a completely distinct organization of the 5-HT systems across the animal kingdom, several lines of evidence suggest that the influences of 5-HT on behavior and cognition are evolutionary conserved. In this review, we have selected some behaviors classically evoked when addressing the roles of 5-HT on nervous system functions. In particular, we focus on the motor activity, arousal, sleep and circadian rhythm, feeding, social interactions and aggressiveness, anxiety, mood, learning and memory, or impulsive/compulsive dimension and behavioral flexibility. The roles of 5-HT, illustrated in both invertebrates and vertebrates, show that it is more able to potentiate or mitigate the neuronal responses necessary for the fine-tuning of most behaviors, rather than to trigger or halt a specific behavior. 5-HT is, therefore, the prototypical neuromodulator fundamentally involved in the adaptation of all organisms across the animal kingdom.

Keywords: aggressiveness; animal phyla; anxiety; decision-making; feeding; impulsive/compulsive dimension; locomotion; mood; neuronal excitability; serotonin receptor.

Figure 1

Functions modulated by 5-hydroxytryptamine (5-HT) in different species. (A) functions modulated related to motor activities and locomotion, (B) functions modulated related to sleep and circadian rhythms, (C) functions modulated related to sleep and circadian rhythms, (D) functions modulated related to social interactions, social status and aggressiveness, (E) functions modulated related to anxiety, (F) functions modulated related to mood, (G) functions modulated related to learning and memory.