Anterior cingulate cortex lesions disrupt latent inhibition in theinhibitory avoidance paradigm

• Main Authors: Chih-Chia Yen, 顏志家
• Other Authors: Sin-Chee Chia
• Format: Others
• Language: zh-TW
• Online Access: http://ndltd.ncl.edu.tw/handle/53j68m

碩士 === 慈濟大學 === 神經科學研究所 === 96 === Latent inhibition(LI) is a phenomenon whereby repeatedly exposure to a neutral stimulus (or conditioned stimuli, CS) in the absence of reinforcement produces a decrement in the capacity of the stimulus to elicit a conditioned response after paired presentations of the CS and unconditioned stimuli (US). In the previous study, we have shown that 5 day pre-exposure to the context retarded the retention of inhibitory avoidance (IA) learning as well as reduced the number of pERK-ir neurons in the central and basolateral nuclei of the amygdala, perirhinal cortex, hippocampus, and secondary motor cortex while comparing the no and different context pre-exposure conditions. The role of anterior cingulate cortex (ACC) in latent inhibition of the IA learning task was investigated in the present study. In experiment one, we established a latent inhibition paradigm with 5 day of context pre-exposure. In experiment two, we examined the effect of ACC and fimbria-fornix (FF) lesions on IA with 5 day pre-exposure. The present result shows that retention latency increased significantly after radiofrequency lesions of the ACC, but not the FF. In experiment three, we examined the effect of ACC lesions on IA learning per se. The data demonstrates that pre-training ACC lesions have no effect on IA retention latency. In experiment four, we examined the effect of neurotoxic N-methyl-D-aspartate (NMDA) on the LI effect. Similarly, neurotoxic lesions of the ACC blocked LI of IA learning. This pattern of results reveals that neurons in the ACC are required for LI learning. Finally, we examined the effect of temporary inactivations of the ACC on the acquisition, consolidation and expression of the LI effect. Microinfusions of lidocaine into the ACC were administered either before or after pre-exposure, or prior to retention test. Post-PE infusions of lidocaine induced significant enhancement of retention performance on 24-h test. The present findings suggest that the ACC may play a critical role in latent inhibition learning by modulating unreinfoced but not reinforced learning in the brain.