Hallucinations represent a transdiagnostic phenomenon observed in multiple neuropsychiatric disorders, including schizophrenia, substance use disorder and substance-induced psychotic conditions. Despite their clinical prevalence, objective assessment remains challenging due to its subjective nature, underscoring the critical need for validated translational models. The present study explores the biological mechanisms underlying hallucinations, evaluates the animal models developed to date, and discusses methods for analyzing these models along specific pathways. Hallucinations are primarily mediated through glutamatergic and/or serotonergic pathways. Numerous animal models for assessing hallucinations have been extensively reported; however, these models have mainly been designed to investigate specific neurotransmitter mechanisms, rather than encompassing all relevant pathways. Therefore, this study systematically examines currently established animal models based on the aforementioned neurotransmitter mechanisms and proposes future directions for developing universal animal models capable of comprehensively evaluating hallucinatory phenomena. The present study aims to provide deeper insights for future research involving animal models of hallucination.

ABSTRACT
INTRODUCTION
NEURAL PATHWAYS ASSOCIATED WITHHALLUCINATIONS
    Serotonergic pathway
    Glutamatergic pathway
DIRECT ASSESSMENT FOR EVALUATION OFHALLUCINATION IN ANIMAL MODEL
    Head twitch response (HTR)
INDIRECT ASSESSMENTS FOR EVALUATIONOF HALLUCINATION IN ANIMAL MODEL
    Pre-pulse inhibition (PPI)
    Open-field test (OFT)
    Stereotypy
PUTATIVE UNIVERSAL ASSESSMENT OFHALLUCINATIONS
    Representation-mediated learning (RML) model
CONCLUSION
REFERENCES

• Gyebin Lee(College of Veterinary Medicine, Gyeongsang National University, Jinju 52828, Korea)
• Sangmin Lee(College of Veterinary Medicine, Gyeongsang National University, Jinju 52828, Korea)
• Yeung Bae Jin(College of Veterinary Medicine, Gyeongsang National University, Jinju 52828, Korea)
• Han-Na Kim(College of Veterinary Medicine, Gyeongsang National University, Jinju 52828, Korea)
• Joo Hyung Park(College of Veterinary Medicine, Gyeongsang National University, Jinju 52828, Korea)
• Hye Jin Cha(College of Veterinary Medicine, Gyeongsang National University, Jinju 52828, Korea) Corresponding author