Morphine exposure modulates dimensional bias and set formation in anthropoids

Area of Science:

• Cognitive Neuroscience
• Primate Behavior
• Neuropharmacology

Background:

• Humans show behavioral advantages in perceptual tasks, modulated by stimulus dimensions and repetition.
• These modulations are altered in neuropsychological and addiction disorders, with unclear underlying mechanisms.

Purpose of the Study:

• To investigate if behavioral modulations in perceptual tasks exist in other primates.
• To determine if repeated opioid exposure influences these modulations in non-human primates.

Main Methods:

• A target detection task was used, varying the defining dimension (color or shape) trial-by-trial.
• Behavioral (response time) and physiological (electrodermal activity) measures were recorded in humans and macaque monkeys.
• Monkeys underwent scheduled, repeated exposure to morphine.

Main Results:

• Humans showed a bias towards color, while macaques favored shape, but both species exhibited faster responses when the relevant dimension repeated (dimensional set formation, 'switch cost').
• Repeated morphine exposure augmented dimensional bias in monkeys and altered switch costs, even during abstinence.
• These effects were observed during periods of morphine-induced conditioned place preference.

Conclusions:

• Dimensional biases and set formation are evolutionarily preserved cognitive traits in humans and monkeys.
• Repeated opioid exposure interacts with the manifestation of these cognitive traits, suggesting shared neural mechanisms.
• Long-lasting effects of morphine may involve neural pathways underlying perceptual set formation in primates.