Neural Representations of Unconditioned Stimuli in Basolateral Amygdala Mediate Innate and Learned Responses.

Stimuli that possess inherently rewarding or aversive qualities elicit emotional responses and also induce learning by imparting valence upon neutral sensory cues. Evidence has accumulated implicating the amygdala as a critical structure in mediating these processes. We have developed a genetic strategy to identify the representations of rewarding and aversive unconditioned stimuli (USs) in the basolateral amygdala (BLA) and have examined their role in innate and learned responses. Activation of an ensemble of US-responsive cells in the BLA elicits innate physiological and behavioral responses of different valence. Activation of this US ensemble can also reinforce appetitive and aversive learning when paired with differing neutral stimuli. Moreover, we establish that the activation of US-responsive cells in the BLA is necessary for the expression of a conditioned response. Neural representations of conditioned and unconditioned stimuli therefore ultimately connect to US-responsive cells in the BLA to elicit both innate and learned responses.

Meta-analysis of cholecystectomy in symptomatic patients with positive hepatobiliary iminodiacetic acid scan results without gallstones.

OBJECTIVE: To study the clinical results of surgical management in patients with right upper quadrant pain, a positive hepatobiliary iminodiacetic acid (HIDA) scan result, and no gallstones. DATA SOURCES: Health care databases and gray literature. STUDY SELECTION: Each article was scrutinized to determine whether it met inclusion criteria. Only abstracts, full articles, and gray literature that passed the detailed screening procedure were included. Case reports, letters, comments, reviews, and abstracts with insufficient details to meet inclusion criteria were excluded. Gallbladder ejection fraction assessed by means other than cholecystokinin HIDA scan were also excluded. DATA EXTRACTION: Three reviewers independently abstracted the following data from each article: first author, year of publication, journal, type of study, location of study population, institution where the study was conducted, symptoms recorded, imaging modality used to establish the absence of gallstones, HIDA scan ejection fraction, number of cases and controls, number of males and females in each group, method of follow-up, and number of cases lost to follow-up. DATA SYNTHESIS: Ten studies met inclusion criteria (N = 615). Follow-up ranged from 3 to 64 months. Surgical treatment was 15-fold more likely than medical treatment to result in symptom improvement, with 4% of patients reporting no symptom improvement with surgery. Sensitivity analysis in patients with complete symptom relief following surgery revealed an 8-fold greater odds difference than those treated medically (indicating variation in study reporting). CONCLUSIONS: Patients without gallstones who have right upper quadrant pain and a positive HIDA scan result are more likely to experience symptom relief following cholecystectomy than those treated medically. There is, however, wide variability in data reporting, particularly with respect to symptom relief and duration of follow-up. Cholecystectomy is indicated in symptomatic patients without gallstones who have a low-ejection fraction HIDA scan.