Roles of the anterior cingulate cortex and medial thalamus in short-term and long-term aversive information processing.
BACKGROUND
The anterior cingulate cortex (ACC) and medial thalamus (MT) are two of the main components of the medial pain pathway that subserve the affective aspect of pain. The hypothesis of the present study was that the ACC is involved in short-term aversive information processing and that the MT is critical for encoding unconditioned nociceptive information. The roles of these two components in short-term and long-term aversive information processing was investigated using a step-through inhibitory avoidance task.


RESULTS
Behavioral training began 1 week after surgery, in which radiofrequency lesions of the ACC or MT were performed. The retention tests were conducted 30 s (short-term) or 24 h (long-term) after training. Pretraining radiofrequency lesions of the ACC impaired performance in the 30 s, but not 24 h, retention test. Microinfusions of lidocaine into the ACC immediately after training impaired performance in the retention test conducted 10 min later. Pretraining radiofrequency lesions of the MT impaired performance in both the 30 s and 24 h retention tests. However, posttraining, but not pretest, microinfusions of lidocaine into the MT impaired performance in the 24 h retention test.


CONCLUSIONS
These results suggest that the ACC may play an important role in short-term, but not long-term, nociceptive information processing. In contrast, the MT may be important for the consolidation of nociceptive information storage.
Chai
Sin-Chee
SC
Institute of Biomedical Sciences, Academia Sinica, Taipei 11529, Taiwan.
Kung
Jen-Chuang
JC
Shyu
Bai-Chuang
BC
D000818:Animals; D001362:Avoidance Learning; D002540:Cerebral Cortex / Q000502:physiology*; D006179:Gyrus Cinguli / Q000502:physiology*; D008297:Male; D008568:Memory; D010146:Pain / Q000503:physiopathology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013788:Thalamus / Q000502:physiology*