Behavioural and neurochemical mechanisms of learning and memory in Planaria

Planaria, a freshwater flatworm with unique regenerative abilities, has emerged as a valuable model organism for studying learning and memory. A growing body of evidence shows that planarians can recover their learning behaviour even after decapitation and regeneration. Behavioural paradigms, including classical, operant, and threat-related conditioning responses, show the capacity of planaria in learning and expressing both appetitive and aversive memories. Evidence at the molecular level, further confirms the presence of principal neurotransmitters, including glutamate, gamma-aminobutyric acid (GABA) and dopamine, which may contribute to planarian learning, memory and behavioural expression. Importantly, the dynamic balance among glutamatergic, GABAergic and dopaminergic pathways is consistently implicated in learning, memory, neuronal expression and behavioural activity. This review summarises behavioural evidence for learning and memory and highlights the key neurotransmitter systems that regulate these processes. It outlines future research directions for planaria as a valuable model for translational studies on memory and learning.