The prelimbic prefrontal cortex encodes individual differences in approach-avoidance conflict in rats

AQUINO-MIRANDA, G.; FERNANDEZ LEON, J.A.; ENGELKE, D.S.; DO-MONTE, F.H.

houston

Encuentro; UTHeath Virtual Neuroscience Poster Session 2020; 2021

UTHealth

The ability to identify and discriminate cues associated with reward and aversive stimuli allows an organism to select the most appropriate behavioral response. Neurons in the prelimbic subregion of the prefrontal cortex (PL) respond to both reward- and threat-associated cues. However, whether PL activity regulates the animals’ decision to approach or avoid such cues remains unknown. To address this question, male Long-Evans Hooded rats with single-unit recording electrodes implanted in PL were initially trained to press a bar for sucrose during the presentation of audiovisual cues. Next, rats were fear conditioned by pairing a neutral odor with electrical footshocks. During the test session, rats were placed in a rectangular arena comprising two different zones: a food zone where the bar, the sucrose dish, and the odor port were located and an adjacent hidden zone. Rats were exposed to three phases: only audiovisual cues (reward), only odor cues (fear), or both simultaneously (conflict). To search for food during the conflict phase, animals had to leave the hidden zone and approach the conditioned odor presented in the food zone. Our results showed that during the reward phase, animals approached the food zone and pressed the bar immediately after the onset of the food cues. During the fear phase, animals showed stronger defensive behaviors characterized by a reduction in time exploring the food zone and an increase in time spent in the hidden zone. Interestingly, two subpopulations of rats emerged during the conflict phase: rats that continued searching for food (pressers) vs. rats that remained in the hidden area andshowed complete suppression of food-seeking responses (non-pressers). PL recordings (n= 367 neurons, 32 rats) during the reward phase revealed a greater number of sustained reward-cue responses in pressers (~45%), when compared to non-pressers (~11%). Notably, the magnitude of reward-cue responses observed during the conflict phase was similar to the reward phase for pressers, but was drastically reduced for non-pressers (Z-score: >2.58 for excitatory and