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The Perception of the Müller-Lyer Visual Illusion in Schizophrenics and Non-human Primates: A Translational Approach
Ana Luísa Lamounier Costa1,2, Ronaldo Coelho Silva1,2, Pedro H Coelho-Cordeiro1,2
1Primate Center, Institute of Biology, University of Brasília, Brasilia, Brazil.
Abstract:
The Müller-Lyer Illusion (MLI) has been suggested as a potential marker for the perceptual impairments observed in schizophrenia patients. Along with some positive symptoms, these deficits are not easily modeled in rodent experiments, and novel animal models are warranted. Previously, MK-801 was shown to reduce susceptibility to MLI in monkeys, raising the prospects of an effective perception-based model. Here, we evaluate the translational feasibility of the MLI task under NMDA receptor blockage as a primate model for schizophrenia. In Experiment 1, eight capuchin monkeys (Sapajus spp.) were trained on a touchscreen MLI task. Upon reaching the learning criteria, the monkeys were given ketamine (0.3 mg/kg; i.m.) or saline on four consecutive days and then retested on the MLI task. In Experiment 2, eight chronic schizophrenia patients (and eight matching controls) were tested on the Brentano version of the MLI. Under saline treatment, monkeys were susceptible to MLI, similarly to healthy human participants. Repeated ketamine administrations, however, failed to improve their performance as previous results with MK-801 had shown. Schizophrenic patients, on the other hand, showed a higher susceptibility to MLI when compared to healthy controls. In light of the present and previous studies, the MLI task shows consistent results across monkeys and humans. In spite of potentially being an interesting translational model of schizophrenia, the MLI task warrants further refinement in non-human primates and a broader sample of schizophrenia subtypes.
Insights
The Müller-Lyer Illusion (MLI) shows promise as a schizophrenia marker. However, ketamine did not replicate previous findings in monkeys, suggesting the need for further refinement of this primate model for schizophrenia research.
Area of Science:
- Neuroscience
- Psychiatry
- Animal Models
Background:
- Perceptual impairments, like the Müller-Lyer Illusion (MLI), are observed in schizophrenia.
- Rodent models struggle to replicate these deficits, necessitating novel animal models.
- MK-801 previously reduced MLI susceptibility in monkeys, suggesting a potential perception-based model.
Purpose of the Study:
- To evaluate the translational feasibility of the MLI task as a primate model for schizophrenia under NMDA receptor blockage.
- To investigate the effects of ketamine on MLI susceptibility in capuchin monkeys.
- To compare MLI susceptibility between chronic schizophrenia patients and healthy controls.
Main Methods:
- Eight capuchin monkeys were trained on a touchscreen MLI task and tested after ketamine or saline administration.
- Eight chronic schizophrenia patients and eight matched controls were tested on the Brentano version of the MLI.
- Data analysis focused on comparing MLI susceptibility across conditions and groups.
Main Results:
- Monkeys exhibited MLI susceptibility under saline, similar to healthy humans.
- Repeated ketamine administration did not alter monkey performance on the MLI task.
- Schizophrenia patients demonstrated significantly higher MLI susceptibility compared to healthy controls.
Conclusions:
- The MLI task shows consistent results across species, indicating its potential as a translational model for schizophrenia.
- Ketamine's ineffectiveness in the monkey model contrasts with previous MK-801 findings, requiring further model refinement.
- The study highlights the MLI's utility in modeling schizophrenia-related perceptual deficits, but suggests further research with diverse patient subtypes and refined non-human primate protocols.
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