BRAIN IMAGING NEUROREPORT 0959-4965 & Lippincott Williams & Wilkins Vol 12 No 8 13 June 2001 1635 Dispositional pessimism and amygdala activity: a PET study in healthy volunteers Ha Êkan Fischer, 1,2 Maria Tillfors, 3 Tomas Furmark 3 and Mats Fredrikson 3,CA 1 Psychiatric Neuroimaging Research Group, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA; 2 Uppsala University PET Centre, University Hospital, Box 1225, SE-751 42 Uppsala Uppsala; 3 Department of Psychology, Uppsala University, Uppsala, Sweden CA Corresponding Author Received 21 February 2001; accepted 20 March 2001 The present study used scores from Seligman's Attribution Style Questionnaire and [ 15 O] water positron emission tomo- graphic measurements of regional cerebral blood ¯ow (rCBF) to investigate the relation between individual differences in dispositional pessimism and amygdala activity. During scanning 13 healthy non-snake-phobic females passively viewed a snake videotape. Using one-tailed tests, signi®cant negative correla- tions were evident between pessimism scores, with low scores re¯ecting relatively more pessimism, and right (r 0.60; p  0.014) and left amygdala rCBF (r 0.53; p  0.032). These results extend previous neuroimaging ®ndings in healthy subjects indicating a role for the amygdala in transient negative emotional states, and suggest that this multimodal brain region also is involved in more durable negative affects such as dispositional pessimism. NeuroReport 12:1635±1638 & 2001 Lippincott Williams & Wilkins. Key words: Affective style; Attributional style; Brain; Emotion; Human; Negative affect; Neuroimaging; Positron Emission tomography INTRODUCTION Data from both animals and humans have highlighted a central role for the amygdala in the regulation of negative affect [1]. Evidence for a role of the amygdala in the processing of transient negative emotions in healthy sub- jects comes from PET [2] and fMRI studies [3] that showed elevated amygdala activity during induction of sad mood. Further support comes from a PET study by Schneider and colleagues [4], who found increased amygdala activity during a transient state of experimentally inducted help- lessness. In depressed patients dispositional negative affect assessed with the PANAS negative affect scale [5] is correlated with glucose metabolism in the right amygdala [6]. Hence, metabolic rate in the right amygdala is asso- ciated with negative affect in depressed patients [6]. To our knowledge no previous study have examined the role of the amygdala in dispositional negative affect in normal healthy subjects. Therefore, the aim was to study the relation between individual differences in negative attribu- tional style [7], indicative of pessimism, and amygdala activity in a group of healthy individuals. Because there exist sex differences in amygdala activity in induced sadness [3] we restricted our sample to include women only. Dispositional pessimism is associated with attributions of negative events to internal, stable and global causes whereas optimism is characterized by external, unstable and speci®c causal attributions when facing negative situa- tions. The reverse is true for attributions of positive events. To study the relation between pessimism and amygdala activity we statistically tested the correlation between scores from Seligman's Attributional Style Questionnaire (SASQ) [7], with low scores re¯ecting relatively more pessimism, and [ 15 O] H 2 O PET measurements of regional cerebral blood ¯ow (rCBF) in the right and the left amygdala. Thus, we performed a hypothesis driven direc- ted search and hypothesized a negative correlation be- tween scores from SASQ [7] and amygdala rCBF. MATERIALS AND METHODS Subjects: Thirteen female subjects, with a mean ( s.d., range) age of 27 ( 6, 20±33) years participated. Subjects were clinically screened and those with DSM-IV [8] de®ned snake phobia, previous or current psychiatric, neurologic, medical disease, or current use of psychoactive medication or substance abuse, were excluded from the study. Subjects refrained from both tobacco and caffeine 12 h prior to the PET investigation. The study was approved by the Uppsala University Medical Faculty Ethical Review Board and the Uppsala University Isotope Committee. Informed consent was obtained from all participants according to the De- claration of Helsinki. Procedure: All subjects viewed a video displaying moving snakes indoors and outdoors. The video was displayed continuously for 2 min, starting 20 s before and lasting 100 s during PET scanning, on a 11 3 8.5 cm TV screen about 30 cm in front of the subject's eyes. This video was novel to the subjects and it was presented twice with 10 min between presentations. In addition, subjects were