PRELIMBIC CORTEX CONTROLS THE SPEED, BUT NOT THE ACCURACY, OF SIMPLE VISUALLY GUIDED DECISIONS

Intra-cortical pharmacology and computational modeling were used to examine motivational and cognitive measures of decision making in a rodent model. Using a task reported in Swanson et al. (2021), male and female rats were trained to select lateralized visual stimuli after responding in a central port, and the luminance of the stimulus was predictive of reward magnitude. We found a sex difference in the initial learning of the task, with female rats responding more selectively and faster to high value stimuli. Computational models suggest that males improve their performance by lowering decision variability as they gain experience, while females remain more stable throughout learning. Rats were then implanted with bilateral cannula targeting the prelimbic cortex (PLC) and received infusions of the GABA-A receptor agonist muscimol (0.01-1.0 μg/μl). Reversible inactivation of PLC had motivational effects on performance, reducing choice latencies without affecting choice preference. As very few studies have examined the role of the opioid system in the frontal cortex, we then made infusions of the mu opioid receptor agonist DAMGO (1 μg/μl) into PLC. We found that DAMGO had the opposite effects of reversible inactivation: increased choice latencies and no effects on choice preference. In both males and females, computational models suggest that inactivating PLC reduces decision variability and the amount of evidence needed to make a decision. By contrast, opioid stimulation increases the amount of evidence needed and slows the rate of evidence accumulation.