Abstracts

We have found that healthy young adults remember odors leading to large emotional reactions (measured with self ratings and galvanic skin response (GSR)) better than odors provoking smaller emotional reactions. Because the amygdala seems to be critically implicated in memory for emotional information and because it is part of the primary olfactory area, we hypothesized that patients with a unilateral amygdala resection (included in a selective amygdalohippocampectomy (SAH) or a corticoamygdalohippocampectomy (CAH)) would not show the normal better memory for emotional than for nonemotional odors, but that instead their memory would be the same without respect to the emotion-arousing properties of the odors to be remembered . We tested 20 patients who had undergone a SAH or CAH (10 left (6 men), 10 right (3 men)) for treatment of intractable epilepsy, and 32 healthy control subjects matched to the patients for age, education and gender. First, participants smelled passively 21 odors (time interval between odors: 45 seconds) while their breathing, heart rate and GSR were measured. Second, they smelled the same 21 odors again and rated each odor[apos]s intensity, pleasantness, familiarity and emotion-arousing properties. Third, a few days later (mean=5.3, standard deviation=3.4), we gave participants an unexpected recognition odor memory test. Patients did not show better memory for emotional odors than for nonemotional ones, whereas the healthy control subjects did. There was no difference between patients with a left or right resection in odor memory accuracy or response bias. However, patients with a right resection tended to rate all odors as less emotionally arousing than did patients with a left resection and healthy control subjects. Control subjects showed greater GSR changes to arousing than to nonarousing odors, but the breathing and heart rate measures did not differ as a function of these properties of the odors. Patients who undergo a SAH or CAH, whether in the left or right hemisphere, lose the memory advantage that odors causing strong emotional reactions normally have. This absence of an effect of arousal is not related to differences in perceiving the odors, because only individuals with right resections rated odors differently whereas both left- and right-resection groups failed to remember the emotional odors better than nonemotional ones. This finding is likely owing to resection of the amygdala, which was included in both types of surgery. (Supported by Savoy Foundation and Canadian Institutes of Health Research.)