332 PHAN ET AL. s found.Unde this et al.1998b:LaBar et al.1998:Buchel et al.1999 s I ve udies one a 21100g B iti n and ex across studies patterns of activa nde them ine hle to the tions can be evaluated across similar and dissimilar tional tasks in our database.Furthermore.ths fe emotional tasks.This meta-analysis examines findings conditioning related activations were discussed in a recent review by Buchel and Dolan (2000).0n ific activation peaks were examined in this md if there are meta-analysis.The reporting of deactivation or de with emotional activation tasks that had a comitive creases in din acti alty was en component (e.g.. emotional ni tod mined activations remain undetermine and their spe in regions w ere to ifferent tio s re ain inconclusive or unclear (Hutchinson a em 1999:Raichle et al 2001) ditio cer tain brain regions were for different emotional responses Organization of Results (reflected by the frequency of activation in a s Fifty-five publications/studies (43 PET and 12 fMRI) region ith tas ning from May.1993.to December.2000.that met T ehtfanteria.yalding19subtractiornscoatst atterns and the and 761 individual activation peaks,were included for stion of laterality in activation patterns are major topics in neuroimagi meta-analysis(Table 1).Because the studies adopted dif ng of emotion and thus require an extensive and separate discussion. all foci the Therefore,we have as sig ficant by hosen to report these results sep- ia d lual stu arately (Wager et nanner:(1)Res ith Indivdual Emotion METHODS Socated with Induction Method (visual auditpry.auto happiness):(2)regions as Scope of Review plographical recall/imagery): and (3)regions associated with preser e and abs ence of Cognitive Demand.Table sof activa on uy,an a large for English-language manuscripts of PET and fMRI he af rate but emotionindction5udespubihedbetwenpdaotm2a nent of Induction Method.for a variety of reaso 1990,and Decemb To allow us to pertorm literature often distinguishes between er,200 11T Ireports otional tasks contain varous degrees of cognitive de. s②Th mand.Furthermore,there is a clear interaction between tal processes of emotion (thus.studies of lower -order lon and cog onon a eve To exa sensory or motor processes,such as gustatory/olfactory we ti a were excluded)see reviews er al.1999 vation b s in which an emotional task was co pled with a concurren nitive task (e.g en BOLD-MRD der/emotional expression discrimination.emotional rat- across the entire brain (i.e..excl studi tha ing,picture/face recognition/encoding.naming,counting focused on limited regions of the brain):(4)They all autobiographical recall/imagery.etc.)as Emotion- Cog used the image subtraction methodology to determine or eman provided ta dard a irach n the em rnou Montreal pa (MNI ith nitive Demand This classification allo ws us to examing laboratories.We chose not to include studies on aver the effect of a "nonemotional" ognitive component on sive and trace conditioning (Buchel et al,1998:Morris emotional tasks differences in activation patterns found. Under this circumstance, a broader-based meta-analysis of multi￾ple studies may be one solution (Fox et al., 1998). By examining findings across studies, patterns of activa￾tions can be evaluated across similar and dissimilar emotional tasks. This meta-analysis examines findings across imaging studies in search of specific regions associated with emotional activation in general, with specific emotions and different induction methods. We also examined if there are brain regions associated with emotional activation tasks that had a cognitive component (e.g., emotional expression recognition, gender discrimination, etc.). Particularly, we examined how “sensitive” specific brain regions were to different emotional tasks (reflected by the percentage of studies reporting activation in a region according to a condition of interest). We also examined how “specific” certain brain regions were for different emotional responses (reflected by the frequency of activation in a specific region with a given task in comparison to other re￾gions). The effect of gender and valence (the extent to which emotion is unpleasant or pleasant) on activation patterns, and the question of laterality in activation patterns are major topics in neuroimaging of emotion, and thus require an extensive and separate discussion. Therefore, we have chosen to report these results sep￾arately (Wager et al., in preparation). METHODS Scope of Review In order to illuminate both general and specific pat￾terns of activation associated with different emotional tasks, we searched peer-reviewed journals (indexed in large databases [MEDLINE, PsychInfo, BrainMap]) for English-language manuscripts of PET and fMRI emotion induction studies published between January, 1990, and December, 2000. To allow us to performed planned meta-analysis, all reports included met the following criteria: (1) They involved unmedicated healthy adults; (2) They focused on higher-order men￾tal processes of emotion (thus, studies of lower-order sensory or motor processes, such as gustatory/olfactory or pain induction, were excluded) [see reviews by by Small et al., 1999; Casey et al., 1994, respectively]; (3) They all measured regional cerebral blood flow (e.g., O15H2O-PET) or blood oxygenation (e.g., BOLD-fMRI) across the entire brain (i.e., excluding studies that focused on limited regions of the brain); (4) They all used the image subtraction methodology to determine activation foci; (5) They provided standard Talairach (Talairach and Tournoux, 1988) or Montreal Neuro￾logic Institute (MNI) coordinates, allowing for compar￾ison of findings across different studies and different laboratories. We chose not to include studies on aver￾sive and trace conditioning (Bu¨ chel et al., 1998; Morris et al., 1998b; LaBar et al., 1998; Bu¨ chel et al., 1999) because those tasks involve associative learning and behavioral conditioning (including acquisition and ex￾tinction), rendering them incomparable to the emo￾tional tasks in our database. Furthermore, these fear￾conditioning related activations were extensively discussed in a recent review by Bu¨ chel and Dolan (2000). Only activation peaks were examined in this meta-analysis. The reporting of deactivation or de￾creases in brain activity was not consistent across studies which did not allow meaningful generalization. Also, the neural mechanisms underlying reported de￾activations remain undetermined and their interpreta￾tions remain inconclusive or unclear (Hutchinson et al., 1999; Raichle et al., 2001). Organization of Results Fifty-five publications/studies (43 PET and 12 fMRI) spanning from May, 1993, to December, 2000, that met our database criteria, yielding 119 subtractions/contrasts and 761 individual activation peaks, were included for meta-analysis (Table 1). Because the studies adopted dif￾ferent analysis methods and significance criteria, all foci were accepted when reported as significant by the crite￾ria designated in the individual studies. The activation results are grouped in the following manner: (1) Regions associated with Individual Emotion (fear, sadness, disgust, anger, happiness); (2) regions as￾sociated with Induction Method (visual, auditory, auto￾biographical recall/imagery); and (3) regions associated with presence and absence of Cognitive Demand. Table 1 lists all studies included in the review, arranged alpha￾betically, and identifies the Individual Emotion exam￾ined and the Induction Method employed. We examined the effect of Cognitive Demand, as a separate but related component of Induction Method, for a variety of reasons. Neuroimaging literature often distinguishes between cognitive and emotional tasks, but the majority of the emotional tasks contain various degrees of cognitive de￾mand. Furthermore, there is a clear interaction between emotion and cognition on a functional level. To examine the neuroanatomic basis of this interaction, we examined the effect of these cognitive components in emotion acti￾vation by grouping conditions in which an emotional task was coupled with a concurrent cognitive task (e.g., gen￾der/emotional expression discrimination, emotional rat￾ing, picture/face recognition/encoding, naming, counting, autobiographical recall/imagery, etc.) as Emotion
Cog￾nition or with Cognitive Demand. Conversely, we grouped conditions in which the emotional task did not explicitly have a cognitive component (i.e., passive view￾ing, passive listening) as Emotion alone or without Cog￾nitive Demand. This classification allows us to examine the effect of a “nonemotional” cognitive component on emotional tasks. 332 PHAN ET AL