Differential time courses and specificity of amygdala activity in posttraumatic stress disorder subjects and normal control subjects

Differential Time Courses and Specificity of Amygdala Activity in Posttraumatic Stress Disorder Subjects and Normal Control Subjects Xenia Protopopescu, Hong Pan, Oliver Tuescher, Marylene Cloitre, Martin Goldstein, Wolfgang Engelien, Jane Epstein, Yihong Yang, Jack Gorman, Joseph LeDoux, David Silbersweig, and Emily Stern Background: Previous neuroimaging studies have demonstrated exaggerated amygdala responses to negative stimuli in posttraumatic stress disorder (PTSD). The time course of this amygdala response is largely unstudied and is relevant to questions of habituation and sensitization in PTSD exposure therapy. Methods: We applied blood oxygen level dependent functional magnetic resonance imaging and statistical parametric mapping to study amygdala responses to trauma-related and nontrauma-related emotional words in sexual/physical abuse PTSD and normal control subjects. We examined the time course of this response by separate analysis of early and late epochs. Results: PTSD versus normal control subjects have a relatively increased initial amygdala response to trauma-related negative, but not nontrauma-related negative, versus neutral stimuli. Patients also fail to show the normal patterns of sensitization and habituation to different categories of negative stimuli. These findings correlate with measured PTSD symptom severity. Conclusions: Our results demonstrate differential time courses and specificity of amygdala response to emotional and control stimuli in PTSD and normal control subjects. This has implications for pathophysiologic models of PTSD and treatment response. The results also extend previous neuroimaging studies demonstrating relatively increased amygdala response in PTSD and expand these results to a largely female patient population probed with emotionally valenced words. Key Words: PTSD, amygdala, fMRI, time course, neuroimaging, emotion

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osttraumatic stress disorder (PTSD) occurs when an individual experiences a traumatic event; reacts with intense fear, helplessness, or horror; and develops symptoms including reexperiencing (nightmares, flashbacks), avoidance, numbing, and hyperarousal that persist for at least a month (American Psychiatric Association 2000). Posttraumatic stress disorder is a common disorder with a lifetime prevalence of about 8% in the general population (American Psychiatric Association 2000). In addition to assault, accident, and combat-related trauma, terrorism-related trauma has recently focused additional attention on this disorder (LeDoux and Gorman 2001). The amygdala is of interest to the study of PTSD because of its involvement in emotional memory, emotional/behavioral manifestations of fear, and autonomic response (LeDoux 1996, 2000). Neurocircuitry models of PTSD have hypothesized an overactive amygdala with inadequate top-down governance over the amygdala by medial prefrontal cortex (mPFC; specifically, the rostral anterior cingulate cortex) and the hippocampus (Golier and Yehuda 2002; Rauch et al 2003b; Shin et al 2004; Vermetten and Bremner 2002). Posttraumatic stress disorder patients, compared with normal control subjects, have shown increased cardiac, skin conductance, and electromyogram responses to loud tones (Orr From the Functional Neuroimaging Laboratory (XP, HP, OT, MG, WE, JE, YY, DS, ES), Weill Medical College of Cornell University; The Rockefeller University Laboratory of Neuroendocrinology (XP); New York University School of Medicine (MC); Mount Sinai School of Medicine (JG); and New York University (JL), New York, New York. Address reprint requests to Dr. Emily Stern, Functional Neuroimaging Laboratory, Department of Psychiatry, Box 140, Room 1302, Weill Medical College of Cornell University, 1300 York Avenue, New York, NY 10021; E-mail: [email protected]. Received June 28, 2004; revised December 1, 2004; accepted December 13, 2004.

0006-3223/05/$30.00 doi:10.1016/j.biopsych.2004.12.026

et al 1995; Shalev et al 1992). A disturbance in memory function is one of the core symptoms in PTSD (Golier and Yehuda 2002; McNally 1997). Functional neuroimaging studies in normal subjects have found selective activation of the amygdala in processing negative emotional stimuli, including words (Breiter et al 1996; Isenberg et al 1999; Morris et al 1996; Phelps et al 2001), and in fear conditioning (Buchel et al 1998; LaBar et al 1998). Numerous studies have found increased amygdala activity to traumatic stimuli in PTSD patients (Liberzon et al 1999; Rauch et al 1996, 2000; Shin et al 1997). Based on animal studies showing that mPFC lesions disrupt emotional regulation (Morgan et al 1993; Quirk et al 2000), this may represent an intrinsic lower threshold of amygdala response to fearful stimuli and/or a dysfunction of the mPFC, including the anterior cingulate, with a failure to inhibit amygdala activation (Pitman et al 2001; Villarreal and King 2001). A study demonstrating exaggerated amygdala response to masked fearful faces in PTSD supports an intrinsic lower threshold of amygdala response dissociated from medial frontal activation (Rauch et al 2000). However, a number of studies that have successfully demonstrated alterations in hippocampal and prefrontal activation in PTSD patients have not found amygdala hyperresponsivity (Bremner et al 1999a, 1999b, 2003b). Further characterization of the amygdala response in PTSD subjects and normal control subjects is essential to gain an improved understanding of the neurobiology of PTSD. Such a characterization can also help test models of PTSD pathophysiology, understand mechanisms of treatment, and explain interstudy differences. Amygdala habituation to emotional stimuli is well documented in normal control subjects (Fischer et al 2003; Phelps et al 2001; Wright et al 2001). Posttraumatic stress disorder patients may differ from normal control subjects in temporal dynamics as well as magnitude of amygdala response. Current questions include the time course of the amygdala response, the specificity of the amygdala response to given classes of stimuli, the extent to which the amygdala response is generalizable to different PTSD patient populations, and the degree to which the BIOL PSYCHIATRY 2005;57:464 – 473 © 2005 Society of Biological Psychiatry

X. Protopopescu et al amygdala response correlates with overall PTSD severity and specific PTSD symptoms. We previously demonstrated increased amygdala response to threatening words and have been utilizing the specificity of linguistic stimuli to study limbic function in psychiatric disorders (Isenberg et al 1999). Here, we developed a linguistic emotional task in conjunction with blood oxygenation level dependent (BOLD) functional magnetic resonance imaging (fMRI) to investigate the neurocircuitry underlying PTSD. We examined the time course of amygdala response by dividing our 24-minute study into early and late epochs. Using trauma-relevant negative, panic-relevant negative (negative control condition), positive, and neutral words, we tested the hypothesis that PTSD subjects would show differential amygdala activation to these different emotional word categories over time and specifically demonstrate initial increased amygdala activity to trauma-related versus neutral words, possibly in the context of a “primed” traumaspecific limbic response.

Methods and Materials Subjects Participants consisted of 11 sexual/physical assault PTSD and 21 normal control subjects. Data sets were excluded if there was significant loss of echo-planar imaging (EPI) signal in the orbitofrontal cortex, ghosting artifact, or head motion. Subjects were also excluded for failing to respond to the task and for medical history misinformation. Subjects included in the final analysis consisted of 9 PTSD subjects (mean age ⫽ 35, range ⫽ 20 –55; 7 female subjects and 2 male subjects) and 14 normal control subjects (mean age ⫽ 27, range ⫽ 22– 42; 7 female subjects and 7 male subjects). All subjects gave informed consent prior to participation in the study, which was part of a protocol approved by the Institutional Review Board at New York-Presbyterian Hospital/Weill Medical College of Cornell University. All subjects were right-handed, native English speakers, aged 18 to 55. Posttraumatic stress disorder subjects all had a primary diagnosis of PTSD by DSM-IV criteria, eight of nine subjects had sexual assault PTSD, and one subject had physical assault PTSD. Two subjects had secondary diagnoses of social phobia, one of which also had secondary diagnoses of specific phobia, obsessive-compulsive disorder, and dysthymia. One subject had a secondary diagnosis of major depressive disorder. Only one of the nine PTSD subjects had ever taken psychiatric medication, and that subject was medication-free for over 1 year prior to scanning. No subjects had any history of substance abuse or dependence, and urine toxicology was performed prior to scanning. Normal and PTSD subject characterization used the following measures: Structured Clinical Interview for DSM-IV Axis I Disorders (SCID-I) (First et al 1997), Beck Depression Inventory (BDI) (Beck et al 1981), State-Trait Anxiety Inventory (STAI/TRAI), and Dissociative Experience Scale (DES) (Bernstein and Putnam 1986). Posttraumatic stress disorder subject characterization additionally used a variety of measures including: Structured Clinical Interview for DSM-IV Personality Disorders (SCID-II) (Spitzer et al 1994), State Trait Anger Expression Inventory (STAXI) (Spielberger et al 1983), PTSD Symptom Scale-Self Report (PSS-SR) (Foa 1995), COPE, and Anxiety Sensitivity Index (ASI) (Reiss et al 1986). For PTSD subjects, a trauma history was first established using the Sexual Assault and Adult Interpersonal Violence (SAAIV), Childhood Interpersonal Violence Before Age 18 (CIVI), and Adult Non-Interpersonal Violence scales. The Clinician Administered PTSD Scale (CAPS) (Blake et al 1995) was

BIOL PSYCHIATRY 2005;57:464 – 473 465 used to establish a diagnosis of PTSD. To meet criteria for diagnosis of PTSD, the subject must have had the following symptoms: for symptom B cluster (reexperiencing symptoms), at least one symptom with a frequency rating of 1 and intensity rating of 2; for symptom C cluster (avoidance and numbing symptoms), at least three symptoms; and for symptom D cluster (startle response/hyperarousal), at least two symptoms. The CAPS scores of our PTSD subjects ranged from 37 to 91 with a mean of 60. Stimuli Stimuli consisted of 48 negative/anxiety (24 negative/PTSD, 24 negative/panic), 48 neutral, and 48 positive/safety words, balanced across categories for frequency, length, and part of speech (nouns and adjectives/verbs). Posttraumatic stress disorder words were designed to be relevant to physical/sexual trauma; panic words were designed to be relevant to panic attack symptoms and somatic/illness-related anxiety (a negative control condition, as well as explicit probes for panic disorder patients also studied as part of a larger project); and positive words were designed to be counter-anxiety and evocative of safety, relaxation, and reward, as defined by the literature and clinical experience. These word types were rated for suitability by a panel of three experienced clinicians. They were based on a similar list of words that had been piloted on 34 normal subjects, who rated the three word types (positive, negative, and neutral) as significantly different in valence (p ⬍ .001) and rated positive and negative words as not significantly different in intensity (p ⬎ .2). Examples are as follows: negative/PTSD–rape, assault, force; negative/panic–frantic, death, cancer; neutral– bookcase, clarinet, rotate; positive/rewarding–safe, gentle, delighted. The three valences of words were presented within a block design (six words per block, eight blocks per valence), with blocks balanced to control for order and time effects. Posttraumatic stress disorder words and panic words were presented for four blocks each (each representing half of the total negative word blocks). Each word appeared for 2 seconds, followed by an interstimulus interval jittered around an average of 2.8 seconds, for a total of 28.8 seconds per block. Blocks were presented in four study epochs containing six blocks each (Figure 1). Each block was followed by 24 seconds of rest, with each epoch as a whole preceded and followed by 2 additional 12-second rest periods. The entire word paradigm took approximately 24 minutes. Stimulus presentation and response collection were performed within the Integrated Functional Imaging System– Stand Alone (IFIS-SA; www.MRIDevices.com/Funct/IFIS.asp)/EPrime environment. During presentation of stimuli, subjects were instructed to read each word silently and to then immediately press a button under their right index finger. During rest periods, they were instructed to look at a dash at the center of the screen and to have their minds either blank or floating freely. Subjects also completed an instructed fear-conditioning paradigm in the scanner (discussed elsewhere). Approximately half of the subjects completed this before and half completed this after the word paradigm. After the emotional word paradigm, subjects were removed from the scanner and given an incidental memory test utilizing a list of words consisting of the 144 stimuli seen during scanning (targets) randomly interspersed with 72 other words (distracters to control for false alarms); divided equally into negative (PTSD and panic), neutral, and positive categories; and balanced for the same qualities as the targets. They were instructed to read each word and to indicate those that they believed they had seen in the scanner. Following www.elsevier.com/locate/biopsych

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Figure 1. Schematic figure of the neuropsychological paradigm architecture.

completion of that task, subjects were also asked to rate the valence and intensity of each word on scales of ⫺3 to ⫹3. Image Acquisition All image data were acquired with a research-dedicated GE Signa 3 Tesla MRI scanner (maximum gradient strength 40mT/m, maximum gradient slew rate 150T/m/s) (General Electric Company, Waukesha, Wisconsin) at the Weill Medical College of Cornell University. Blood oxygen level dependent fMRI measures hemodynamic and oxygenation changes associated with localized neuronal activity in the brain. After shimming to maximize homogeneity, a series of 3T fMRI scans was collected using gradient echo echo-planar imaging (repetition time [TR] ⫽ 1200; echo time [TE] ⫽ 30; flip angle ⫽ 70o; field of view [FOV] ⫽240 mm; 15 slices; 5 mm thickness with 1 mm interslice space; matrix ⫽ 64 x 64), with a modified z-shimming algorithm to reduce susceptibility artifact at the base of the brain (Gu et al 2002). T1-weighted anatomical images were acquired using a spoiled gradient recalled acquisition (SPGR) sequence with a resolution of .9375 x .9375 x 1 mm3. Image Processing and Data Analysis Statistical Parametric Mapping (SPM99) software (Wellcome Department of Imaging Neuroscience, London, United Kingdom) was used for processing and preprocessing of the data (Friston et al 1995a, 1995b). To build the statistical model, a whole-brain, voxel-by-voxel multiple linear regression model was employed at the single subject level. The resulting set of voxel values for each contrast constituted a statistical parametric map of the t statistic (SPM{t}), which was then transformed to the unit normal distribution, SPM{Z} (Friston et al 1995b). All coordinates presented here are in Montreal Neurological Institute (MNI) space (MNI average 152 T1 brain). For group analyses, we used a random effects model, which accounts for intersubject variability and allows population-based inferences to be drawn (Friston et al 1999). For each subject, the contrast image for each condition (i.e., the condition effects against the resting state) was generated, and these were combined in a series of linear contrasts to assess group effects. We also ran the analysis using the nine PTSD patients and nine gender-matched normal control subjects. The conditions of interest were the four word types: positive, neutral, PTSD/ negative, and panic/negative. In addition, the analysis was run separately using age, gender, or paradigm order as covariates of no interest in an analysis of variance (ANOVA) setting. The results were analyzed from the first two study epochs (early) and the last two study epochs (late) separately to examine time effects. Group and condition comparisons of interest generated www.elsevier.com/locate/biopsych

statistical parametric maps (SPMs) of the t statistic (SPM{t}), which was again transformed to a unit normal distribution (SPM{Z}). Because we had a region-specific hypothesis for the amygdala, a region-of-interest analysis was performed. For this purpose, to ensure complete coverage of all amygdala subnuclei, a combined mask of the amygdala (as defined by Automated Anatomical Labeling [AAL] areas 41 and 42 [Tzourio-Mazoyer et al 2002]) and adjacent periamygdaloid cortex (Brodmann area 28) was created in MNI space. Reflecting hypotheses, an initial t map threshold of p ⫽ .01 uncorrected was used (p values presented are uncorrected unless specified). As the AAL-Brodmann area 28 combined mask extends somewhat anteriorly and posteriorly to the amygdala proper, only those points falling within the mask and meeting the additional criteria of falling between ⫺6 and ⫹3 in the y-direction were considered as amygdala cluster peaks. Within the amygdala, a priori regions of interest were specified using the small volume correction (SVC) function to a surrounding sphere of radius 4 mm (approximately .25 cc) in SPM and were considered significant if the corresponding voxelwise p value was less than .05 corrected (Friston 1997; Worsley et al 1996). Significant differences in group, condition, and interaction effects were assessed in these regions within the context of a General Linear Model and Gaussian Random Field Theory. A correlation analysis was also performed to determine the association between activity in the amygdala and a clinical measure of PTSD severity (CAPS total). A correlation analysis was also performed to determine the association between activity in the amygdala and the clinical measure thought to be of greatest relevance to the experimental paradigm, subjective rating of psychological distress experienced at trauma reminders (CAPS B4).

Results Between-Group Effects of Condition As hypothesized and consistent with previous studies in PTSD subjects, PTSD versus normal subjects show increased left amygdala BOLD response to trauma-relevant negative (PTSD) words versus neutral words p ⫽ .006 (Table 1). Of note, here this difference was demonstrated in the early, but not late, half of the study. Posttraumatic stress disorder versus normal subjects demonstrate differential time courses of left amygdala BOLD response to PTSD words controlled for neutral words, p ⫽ .005 (Table 1, Figures 2 and 3). The [(PTSD/early versus Neutral/ early) versus (PTSD/late versus Neutral/late)] contrast, abbreviated [(PTe vs. NUe) vs. (PTl vs. NUl)], represents the change in response to PTSD words, controlled for neutral words, from the first half of the study to the second half of the study. A direct comparison of early versus late PTSD words in normal subjects shows a sensitization pattern, with left amygdala

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X. Protopopescu et al Table 1. PTSD Versus Normal Control Subjects

Left Amygdala x, y, z Z p Uncorrected p Corrected SVC. Volume (mm3) Right Amygdala x, y, z Z p Uncorrected p Corrected SVC. Volume (mm3)

PTe vs. NUe

(PTe vs. NUe) vs. (PTl vs. NUl)

(PAe vs. NUe) vs. (PAl vs. NUl)

PAe vs. PAl

⫺21, 0, ⫺27 ⫹2.5 .006 .027 81

⫺18, 3, ⫺30a ⫹2.57 .005 .024 189

⫺30, ⫺6, ⫺15b ⫺2.80 .003 .007 (⫺30, ⫺9, ⫺15)c 513

⫺24, 0, ⫺27 ⫺3.57 .000 .001 999 21, ⫺3, ⫺24 ⫺2.57 .005 .022 351

Contrasts showing differential activations within a bilateral amygdala region for p ⬍ .01, volume (within amygdala region) ⱖ50 mm3. PTSD, posttraumatic stress disorder; PT, PTSD words; PA, panic words; NU, neutral words; e, early first two epochs; l, late second two epochs; SVC, small volume correction. a Figure 2. b Figure 6. c These activations extend into the defined amygdala boundary although the maxima lie slightly outside of that boundary.

BOLD response increasing in the late versus early blocks, p ⫽ .001 (Table 2, Figure 4). This sensitization pattern for PTSD words in normal subjects is still apparent after controlling for neutral words, p ⫽ .002 (Table 2, Figure 5). Thus, normal subjects build up a response to PTSD words during the study, and they demonstrate increased left amygdala BOLD response for PTSD versus neutral words late, but not early, in the study, p ⫽ .001 (Table 2). Posttraumatic stress disorder subjects fail to show this sensitization pattern in the left amygdala, as demonstrated by the left amygdala increase in BOLD response seen in PTSD versus normal subjects for the [(PTe vs. NUe) vs. (PTl vs. NUl)] contrast (Table 1, Figure 2). The time course of left amygdala activity to nontrauma relevant negative words (panic words) controlled for neutral words demonstrates the opposite pattern to that of PTSD words controlled for neutral words in PTSD versus normal subjects, p ⫽

Figure 2. Amygdala response in PTSD versus normal subjects to PTSDrelated words controlled for neutral words over time (Table 1) ([PTe vs. NUe] vs. [PTl vs. NUl]) (y ⫽ 3) p ⬍ .01. Color-coding in the scale represents study specific t values. PTSD, posttraumatic stress disorder; PT, PTSD-related words; NU, neutral words; e, early epochs; l, late epochs.

.003 (Table 1, Figure 6). The [(PAe vs. NUe) vs. (PAl vs. NUl)] contrast represents the change in response to panic words, controlled for neutral words, from the first half of the study to the second half of the study. A direct comparison of early versus late panic words in normal subjects shows a habituation pattern, with bilateral amygdala BOLD response increased in the early versus late blocks, p ⫽ .001 (Table 2, Figure 5). This habituation pattern for panic words in normal subjects is still apparent in the left amygdala after controlling for neutral words, p ⫽ .007 (Table 2). Thus, normal subjects have an initially strong response to panic words that diminishes during the study, and they demonstrate increased left, p ⫽ .007, amygdala BOLD response for panic versus neutral words early, but not late, in the study (Table 2). Posttraumatic stress disorder subjects, compared with normal control subjects, fail to show this habituation pattern in the left, p ⬍ .001, or right, p ⫽ .005, amygdala for panic words (Table 1). Posttraumatic stress disorder subjects, compared with normal control subjects, also fail to show this habituation pattern for panic words compared with neutral words in the left amygdala, p ⫽ .003 (Table 1). Further evidence that PTSD subjects actually demonstrate the opposite pattern of sensitization to panic words is that when compared with normal control subjects, they demonstrate increased left amygdala BOLD response to panic words late, but not early, in the study (Figure 7). No differential time course for PTSD versus normal subjects for positive words controlled for neutral words was seen in the amygdala at p ⬍ .01. Symptom Correlations Blood oxygenation level dependent response for PTSD versus neutral words in the left amygdala correlated with severity of PTSD symptoms, as measured by the total CAPS score (x, y, z: ⫺18, 3, ⫺24; p ⬍ .001, pcorr ⬍ .050, volume ⫽ 54 mm3) (Figure 8). This correlation also appears in the right amygdala at a lower threshold (15, ⫺6, ⫺21; p ⫽ .01, volume ⫽ 27 mm3). Separate CAPS total correlation analysis of the early and late responses to PTSD words versus neutral words in PTSD subjects indicates that this finding is driven primarily by a positive correlation with early increased activity in the left (⫺24, 3, ⫺18; p ⫽ .019) and right (18, www.elsevier.com/locate/biopsych

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Figure 3. BOLD activity size of effect (%) at the amygdala point showing maximum activity in PTSD versus normal subjects to PTSD-related words controlled for neutral words over time (⫺18, 3, ⫺30). Activity is shown for neutral early and late (NUE, NUL), PTSD early and late (PTE, PTL), and PTSD versus neutral early and late (PTEVNUE, PTLVNUL) word conditions relative to a resting baseline in PTSD patients and normal control subjects. BOLD, blood oxygenation level dependent; PTSD, posttraumatic stress disorder.

⫺3, ⫺30; p ⫽ .017) amygdala for PTSD versus neutral words, since no correlation with late amygdala activity for PTSD versus neutral words is seen at p ⬍ .05. The CAPS rated symptom with the greatest relevance to our trauma-related word paradigm is B4, subjective rating of frequency and intensity of psychological distress when presented with reminders (internal or external cues that symbolize or resemble an aspect of the traumatic event). Positive correlations between CAPS B4 and left (⫺21, 0, ⫺18, p ⬍ .001, pcorr ⫽ .004, volume ⫽ 486 mm3) and right (18, 3, ⫺24, p ⬍ .001, pcorr ⫽ .004, volume ⫽ 1242 mm3) amygdala BOLD response for PTSD versus neutral words in the early half of the study further strengthens our finding of increased activity for PTSD versus normal subjects

for this contrast (Tuescher et al, unpublished data). Further evidence for the importance of time effects can be seen in a trend toward a negative correlation between CAPS B4 and right amygdala activity for PTSD versus neutral words in the late half of the study (21, ⫺3, ⫺24, p ⫽ .018). Correlations between CAPS B4 and amygdala activation for PTSD and neutral words in the two halves of the study support the time course differences found between PTSD patients and normal control subjects. The greater the CAPS B4 score, the greater the difference in bilateral amygdala response to PTSD words controlled for neutral words from the early to the late half of the study, p ⫽ .002 (Figure 9, Table 3). The greater the CAPS B4 score, the greater the increase in right amygdala response to

Table 2. Normal Control Subjects

Left Amygdala x, y, z Z p Uncorrected p Corrected SVC Volume (mm3) Right Amygdala x, y, z Z p Uncorrected p Corrected SVC Volume (mm3) Left Amygdala x, y, z Z p Uncorrected p Corrected SVC Volume (mm3)

PTe vs. PTl

PAe vs. PAl

(PTe vs. NUe) vs. (PTl vs. NUl)

(PAe vs. NUe) vs. (PAl vs. NUl)

⫺21, 0, ⫺24b ⫺3.04 .001 .009 1296

⫺27, ⫺3, ⫺24c ⫹3.09 .001 .006 648

(⫺24, 6, ⫺30)a ⫺2.84 .002 .014 108

⫺27, ⫺3, ⫺27 ⫹2.47 .007 .026 (⫺27, ⫺6, ⫺27)a 54

(27, ⫺9, ⫺12)a ⫺2.58 .005 .027 162 PTl vs. NUl

18, ⫺3, ⫺24 ⫹3.26 .001 .004 1161 PAe vs. NUe

(⫺18, 6, ⫺30)a ⫹3.28 .001 .004 351

⫺21, ⫺6, ⫺12 ⫹2.47 .007 .025 (⫺18, ⫺6, ⫺12)a 108

Activations within the bilateral amygdala region for PTSD, panic, and neutral words in the early and late study epochs. p ⬍ .01, volume (within amygdala region) ⱖ50 mm3. PTSD, posttraumatic stress disorder; SVC, small volume correction; PT, PTSD words; PA, panic words; NU, neutral words; e, early first two epochs; l, late second two epochs. a These activations extend into the defined amygdala boundary, although the maxima lie slightly outside of that boundary. b Figure 4. c Figure 5.

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Figure 4. Amygdala response in normal subjects to PTSD-related words over time (Table 2) (PTe vs. PTl) (y ⫽ 0) p ⬍ .01. Color-coding in the scale represents study specific t values. PTSD, posttraumatic stress disorder; PT, PTSD-related words, e, early epochs; l, late epochs.

PTSD words in the early versus the late half of the study, p ⫽ .005, and the greater the decrease in bilateral amygdala response to neutral words in the early versus the late half of the study, p ⫽ .002 (Table 3). Additional Control To be certain that gender difference, paradigm order (instructed fear conditioning paradigm run before or after the word paradigm), and age did not account for our between-group differences, the analysis was run with gender, paradigm order, and age entered as covariates of no interest in an ANOVA setting. When the covariate of no interest was gender, the key betweengroup findings in the left amygdala still reached the significance cutoff of p ⬍ .01. When the covariate of no interest was paradigm order, the between-group findings in the amygdala still reached the significance cut-off of p ⬍ .01. The results remain consistent

Figure 5. Amygdala response in normal subjects to panic-related words over time (Table 2) (PAe vs. PAl) (y ⫽ ⫺3) p ⬍ .01. Color-coding in the scale represents study specific t values. PA, panic-related words; e, early epochs; l, late epochs.

Figure 6. Amygdala response in PTSD versus normal subjects to panicrelated words controlled for neutral words over time (Table 1) ([PAe vs. NUe] vs. [PAl vs. NUl]) (y ⫽ ⫺3) p ⬍ .01. Color-coding in the scale represents study specific t values. PA, panic-related words; NU, neutral words; e, early epochs; l, late epochs.

on entering age as a covariate of no interest, but the significance of the between-group findings decreases, becoming (for the left amygdala) (PTe vs. NUe) (p ⫽ .012), [(PTe vs. NUe) vs. (PTl vs. NUl)] (p ⫽ .031), [(PAe vs. NUe) vs. (PAl vs. NUl)] (p ⫽ .000), PAe vs. PAl (p ⫽ .000), and PAl (p ⫽ .003). In interpreting this effect, it is not possible to separate age from duration of illness, and differences in degrees of freedom can be considered as well. Nevertheless, this suggests that this finding cannot be purely an age effect, as it is still present with the introduction of age as a covariate, albeit at a slightly lower threshold.

Discussion We found that left amygdala BOLD response for traumarelated versus neutral words in the early study epochs was greater in PTSD than in normal subjects (Figure 2) and that left amygdala BOLD response for trauma-related versus neutral words in the PTSD subjects correlated with severity of PTSD symptoms, as measured by the CAPS (Figure 8). These findings are consistent with the findings of Rauch et al (2000), demonstrating that patients with PTSD exhibit exaggerated automatic responses within the amygdala to general threat-related stimuli and that signal intensity change within the amygdala correlates with the severity of PTSD symptoms as measured by the CAPS. This study extends these results, demonstrating time and stimulus specificity. Our results expand their findings of relative trauma-specific increase in amygdala activity in male combat veterans to a largely female patient population suffering from sexual and physical abuse related PTSD in the context of an explicit word driven, rather than implicit face driven, paradigm. Furthermore, we have explored the time course and specificity of this relatively increased amygdala activity across different categories of valenced linguistic stimuli. These findings suggest that in PTSD, the amygdala response to PTSD-related versus neutral linguistic stimuli is initially relatively increased. While normal subjects build up an amygdala response to these PTSD (versus neutral) stimuli over the study session, PTSD subjects have an amygdala response that is present immediately and stays constant or diminishes over the study www.elsevier.com/locate/biopsych

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Figure 7. BOLD activity size of effect (%) at the amygdala point showing maximum activity in PTSD versus normal subjects to panic-related words controlled for neutral words over time (⫺30, ⫺6, ⫺15). Activity is shown for neutral early and late (NUE, NUL), panic early and late (PAE, PAL), and panic versus neutral early and late (PAEVNUE, PALVNUL) word conditions relative to a resting baseline in PTSD patients and normal control subjects. BOLD, blood oxygenation level dependent; PTSD, posttraumatic stress disorder.

session. Furthermore, the opposite amygdala temporal pattern of habituation by normal control subjects and sensitization by PTSD subjects for the negative control condition, panic-related words, indicates that the time course of amygdala response can be quite stimulus-specific. One issue is the universal problem of establishing a “true” baseline in fMRI. Any within-group single condition BOLD signal must be interpreted as relative to a measured baseline. Perceptual and cognitive tasks may interrupt processes ongoing during rest that involve many of the same brain areas engaged during task performance (Binder et al 1999; McKiernan et al 2003). In some cases, including this study, nonaffective cognitive operations can result in a reduction in amygdalar activity in the “neutral” condition. This may represent reallocation of processing resources and/or the supression of affective processing under conditions of cognitive demand. This is why between-group comparisons and between-condition comparisons may actually be easier to interpret than the single condition results, rendering the neutral word condition particularly relevant.

Figure 8. Amygdala response to PTSD words versus neutral words correlated with PTSD symptom severity as measured by the total CAPS score. Total CAPS correlation with PT versus NU (y ⫽ 3) p ⬍ .01. Color-coding in the scale represents study specific t values. PTSD, posttraumatic stress disorder; CAPS, Clinician-Administered PTSD Scale; PT, PTSD-related words; NU, neutral words.

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Currently, most of the functional neuroimaging studies on PTSD patients support amygdala hyperresponsivity (Liberzon et al 1999; Rauch et al 1996, 2000, 2003b; Shin et al 1997), hippocampal volume reduction (Bremner et al 1995, 1997; Gurvits et al 1996; Stein et al 1997), hippocampal activation reduction (Bremner et al 2003a, 2003b), hippocampal N-acetylaspartate (NAA) level reduction (Schuff et al 2001), and attenuated recruitment of anterior cingulate cortex (Bremner et al 1999b; Shin et al 1999, 2001). There is also some evidence for decreased pregenual anterior cingulate and subcallosal cortex volumes in PTSD (Rauch et al 2003a). However, some studies have not found differential amygdala activity (Bremner et al 1999a, 1999b, 2003b) or hippocampal volume reductions (Bonne et al 2001; Carrion et al 2001; De Bellis et al 1999, 2001). Methodological considerations that may explain these discrepancies include signal-to-noise issues in acquiring BOLD and cerebral blood flow (CBF) measurements; interstudy variability in psychological stimuli or in time-windows of acquisition; and

Figure 9. Amygdala response in PTSD patients to PTSD-related words over time controlled for neutral words correlated with severity of psychological distress experienced at traumatic reminders as measured by the CAPS B4 score (Table 3). CAPS B4 correlation with ([PTe vs. NUe] vs. [PTl vs. NUl]) (y ⫽ ⫺2) p ⬍ .01. Color-coding in the scale represents study specific t values. PTSD, posttraumatic stress disorder; CAPS, Clinician-Administered PTSD Scale; PT, PTSD-related words; NU, neutral words; e, early epochs; l, late epochs.

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X. Protopopescu et al Table 3. PTSD Subjects Symptom Correlations (PTe vs. NUe) vs. (PTl vs. NUl) Left Amygdala x, y, z Z p Uncorrected p Corrected SVC Volume (mm3) Right Amygdala x, y, z Z p Uncorrected p Corrected SVC Volume (mm3)

PTe vs. PTl

⫺24, 3, ⫺18b ⫹2.87 .002 .013 (⫺21, 3, ⫺18)a 270 18, ⫺3, ⫺24 ⫹2.95 .002 .012 (18, ⫺6, ⫺24)a 648

NUe vs. NUl ⫺12, 0, ⫺18 ⫺2.85 .002 .019 162

18, ⫺3, ⫺24 ⫹2.54 .005 .035 108

15, ⫺3, ⫺18 ⫺3.24 .001 .008 972

Correlations Between CAPS B4 and temporal changes in amygdala activation for PTSD and neutral words. p ⬍ .01, volume (within amygdala region) ⱖ50 mm3. PTSD, posttraumatic stress disorder; SVC, small volume correction; CAPS, Clinician-Administered PTSD Scale; PT, PTSD words; PA, panic words; NU, neutral words; e, early first two epochs; l, late second two epochs. a These activations extend into the defined amygdala boundary, although the maxima lie slightly outside of that boundary. b Figure 9.

PTSD population heterogeneity with respect to instigating trauma, psychiatric comorbidity, substance abuse, age, gender, and other individual differences. In addition, as imaging resolution improves, distinguishing activity in amygdalar subnuclei may resolve some interstudy differences. Our results, showing differential activity between PTSD and normal subjects in the early and late sessions considered separately but not for the average of all sessions, indicate that careful consideration of time course effects needs to be taken into account and may shed light on the lack of demonstrated differences between psychiatric patient populations and normal control subjects in some studies. The amygdala is central to most models for a neural circuitry in PTSD because it permits assessment of the fear-producing nature of an event, is critical to effectively lay down memory traces related to a potential threat, and is able to influence an individual’s neuroendocrine, autonomic, and motor responses. There is strong evidence that the amygdala and hippocampus are involved in differentiable aspects of learning and/or memory (Bechara et al 1995; Eichenbaum and Cohen 2001; LeDoux 1996), but information processed within the amygdala also modulates synaptic activity and function within the hippocampal formation (Ikegaya et al 1996a, 1996b; Packard et al 1994; Roozendaal and McGaugh 1997; Thomas et al 1984). The most well-studied amygdala-mediated behavior is fear conditioning, in which an animal learns to associate a tone with a shock (Eichenbaum and Cohen 2001; Fanselow and LeDoux 1999; LeDoux 2000). Gender is an important consideration, as males and females may have differential responses depending on the modality used (semantic vs. visual stimuli) and gender may have an effect on laterality of responses (Cahill 2003). Due to our decision to study sexual and physical abuse PTSD, our patient population was largely female subjects. This should be kept in mind when comparing with PTSD studies largely consisting of male subjects (e.g., combat veterans), although our main findings are present with introduction of gender as a nuisance covariable. Age is another important consideration. One caveat is that although

none of the subjects were elderly and while average ages ranged from late 20s to mid 30s, the study groups are not entirely balanced for age. Age can be a difficult variable to control for, as it may correlate with duration of illness. However, our key findings in this hypothesized region do not appear to be simply an effect of age, as they are present, although to a slightly lower threshold, with age entered as a nuisance covariate. In the interpretation of these findings, a limitation is the absence of a trauma-exposure–matched control group. However, the strong correlations between PTSD symptoms as measured by the CAPS scale and amygdala activations in our conditions of interests strongly indicate that our results are relevant to PTSD and not simply trauma exposure. Furthermore, other studies from the literature support the finding of trauma stimulus specific amygdala activation in PTSD versus trauma-exposed PTSD-negative control subjects (Shin et al 1997). Although our data highlight clear differences in the time course of amygdala response to differential emotional word stimuli in PTSD and normal control subjects, any explanation for the behavior of the amygdala in the normal control subjects, sensitization to PTSD words and habituation to panic words, is speculative. One hypothesis is that the majority of panic words used in the study (death, illness, suffocate, etc.) are instantly evocative of negative associations, while a number of the PTSD words used in the study (semen, intercourse, fondle, etc.) may require the context of the other words seen over time (rape, murder, assault, etc.) to become negatively evocative in normal control subjects. Regardless of the reason for this pattern of amygdala activations in normal control subjects, it serves as an interesting baseline against which differential stimulus-specific activations can be seen in PTSD patients. While the initial relative increase of amygdala activity in PTSD patients to PTSD words (versus neutral words) fits with the current literature, the sensitization to panic words indicates that rather than being hyperresponsive to negative stimuli in general, the amygdala in PTSD patients may be initially increased to trauma-relevant versus neutral stimuli and actually exhibit a delayed response, in comparison with normal control subjects, to nontrauma-related negative stimuli. Time courses of response to trauma-related and general negative stimuli have clinical relevance. Exposure therapy, which requires the patient to focus on and describe the details of a traumatic experience in a therapeutic manner, is the most well-established treatment for PTSD with many positive clinical outcome studies (Rothbaum et al 2000; Rothbaum and Schwartz 2002). However, there is still some debate over the efficacy of exposure therapy (Tarrier et al 1999). Exposure methods share the common feature of confrontation with frightening, yet realistically safe, stimuli that continues until the anxiety is reduced (Rothbaum and Schwartz 2002). Habituation, a decreased response to the same stimulus with repeated presentation, is one of the simplest mechanisms accounting for this reduction in anxiety (Rothbaum and Schwartz 2002). It is essential for successful exposure therapy that patients remain in the exposure situation long enough for their anxiety to decrease (Astin and Rothbaum 2000). Short exposures may further sensitize the patient, making fear worse by leaving it unchecked (Rothbaum and Mellman 2001). Thus, key issues in exposure therapy are the time courses of habituation and sensitization to trauma-related stimuli in www.elsevier.com/locate/biopsych

472 BIOL PSYCHIATRY 2005;57:464 – 473 PTSD subjects. We have demonstrated differential time courses of amygdala response to different categories of emotionally valenced words in PTSD and normal control subjects over a 24-minute study. This time window is comparable to that employed in a single-exposure therapy session. Our data may be relevant to mechanisms underlying exposure therapy by indicating that the amygdala of PTSD patients does not sensitize to trauma-relevant words in this time period but rather has a constant to diminishing response. We have also demonstrated correlations between the severity of a PTSD symptom, CAPS B4, and these time courses of amygdala response. Such differential temporal patterns of amygdala activation may provide information of relevance to therapeutic decision making. A clearer understanding of the neurocircuitry of PTSD is emerging, as results accumulate from neuroimaging studies utilizing assorted psychological stimuli in different populations of PTSD patients. This study extends reports of amygdala activation to trauma-related stimuli by providing information regarding temporal dynamics and specificity of response. These features are an important consideration in understanding the neurocircuitry of PTSD and have pathophysiological and therapeutic implications.

This work was supported by NIMH Grant 5-P50MH58911, “Center for Neural Systems of Fear and Anxiety”; the DeWitt Wallace Fund of the New York Community Trust; and NIH MSTP Grant GM07739 (XP). We thank Paul Toth, Dan Zimmerman, Jude Allen, Josefino Borja, Hong Gu, Hilary Hochberg, James Murrough, and Erika Strohmayer for their help on this project. American Psychiatric Association (2000): Diagnostic Criteria from DSM-IV-TR. Washington, DC: American Psychiatric Association. Astin MC, Rothbaum BO (2000): Exposure therapy for the treatment of posttraumatic stress disorder. NC-PTSD Clin Q 9:49 –54. Bechara A, Tranel D, Damasio H, Adolphs R, Rockland C, Damasio AR (1995): Double dissociation of conditioning and declarative knowledge relative to the amygdala and hippocampus in humans. Science 269:1115–1118. Beck AT, Ward CH, Mendelsohn M, Mock J, Erbaugh J (1981): An inventory for measuring depression. Arch Gen Psychiatry 4:561–571. Bernstein EM, Putnam FW (1986): Development, reliability and validity of a dissociation scale. J Nerv Ment Dis 174:727–735. Binder JR, Frost JA, Hammeke TA, Bellgowan PS, Rao SM, Cox RW (1999): Conceptual processing during the conscious resting state. A functional MRI study. J Cogn Neurosci 11:80 –95. Blake DD, Weather FW, Nagy LM, Kaloupek DG, Gusman FD, Charney DS, et al (1995): The development of a clinician-administered PTSD scale. J Trauma Stress 8:75–90. Bonne O, Brandes D, Gilboa A, Gomori JM, Shenton ME, Pitman RK, et al (2001): Longitudinal MRI study of hippocampal volume in trauma survivors with PTSD. Am J Psychiatry 158:1248 –1251. Breiter HC, Etcoff NL, Whalen PJ, Kennedy WA, Rauch SL, Buckner RL, et al (1996): Response and habituation of the human amygdala during visual processing of facial expression. Neuron 17:875– 887. Bremner JD, Narayan M, Staib LH, Southwick SM, McGlashan T, Charney DS (1999a): Neural correlates of memories of childhood sexual abuse in women with and without posttraumatic stress disorder. Am J Psychiatry 156:1787–1795. Bremner JD, Randall P, Scott TM, Bronen RA, Seibyl JP, Southwick SM, et al (1995): MRI-based measurement of hippocampal volume in patients with combat-related posttraumatic stress disorder [see comment]. Am J Psychiatry 152:973–981. Bremner JD, Randall P, Vermetten E, Staib L, Bronen RA, Mazure C, et al (1997): Magnetic resonance imaging-based measurement of hippocampal volume in posttraumatic stress disorder related to childhood physical and sexual abuse–a preliminary report. Biol Psychiatry 41:23–32.

www.elsevier.com/locate/biopsych

X. Protopopescu et al Bremner JD, Staib LH, Kaloupek D, Southwick SM, Soufer R, Charney DS (1999b): Neural correlates of exposure to traumatic pictures and sound in Vietnam combat veterans with and without posttraumatic stress disorder: A positron emission tomography study. Biol Psychiatry 45:806 – 816. Bremner JD, Vythilingam M, Vermetten E, Southwick SM, McGlashan T, Nazeer A, et al (2003a): MRI and PET study of deficits in hippocampal structure and function in women with childhood sexual abuse and posttraumatic stress disorder. Am J Psychiatry 160:924 –932. Bremner JD, Vythilingam M, Vermetten E, Southwick SM, McGlashan T, Staib LH, et al (2003b): Neural correlates of declarative memory for emotionally valenced words in women with posttraumatic stress disorder related to early childhood sexual abuse. Biol Psychiatry 53:879 – 889. Buchel C, Morris J, Dolan RJ, Friston KJ (1998): Brain systems mediating aversive conditioning: An event-related fMRI study. Neuron 20:947–957. Cahill L (2003): Sex-related influences on the neurobiology of emotionally influenced memory. Ann N Y Acad Sci 985:163–173. Carrion VG, Weems CF, Eliez S, Patwardhan A, Brown W, Ray RD, et al (2001): Attenuation of frontal asymmetry in pediatric posttraumatic stress disorder. Biol Psychiatry 50:943–951. De Bellis MD, Hall J, Boring AM, Frustaci K, Moritz G (2001): A pilot longitudinal study of hippocampal volumes in pediatric maltreatment-related posttraumatic stress disorder. Biol Psychiatry 50:305–309. De Bellis MD, Keshavan MS, Clark DB, Casey BJ, Giedd JN, Boring AM, et al (1999): A.E. Bennett Research Award. Developmental traumatology. Part II: Brain development [see comment]. Biol Psychiatry 45:1271–1284. EichenbaumH,CohenNJ(2001):FromConditioningtoConsciousRecollection:Memory Systems of the Brain. Upper Saddle River, NJ: Oxford University. Fanselow MS, LeDoux JE (1999): Why we think plasticity underlying Pavlovian fear conditioning occurs in the basolateral amygdala. Neuron 23: 229 –232. First MB, Spitzer RL, Gibbon M, Williams JBW (1997): Structured Clinical Interview for DSM-IV (SCID). Washington, DC: American Psychiatric Press. Fischer H, Wright CI, Whalen PJ, McInerney SC, Shin LM, Rauch SL (2003): Brain habituation during repeated exposure to fearful and neutral faces: A functional MRI study. Brain Res Bull 59:387–392. Foa E (1995): The Post Traumatic Diagnostic Scale Manual. Minneapolis: NCS. Friston KJ (1997): Testing for anatomically specified regional effects. Hum Brain Mapp 5:133–136. Friston KJ, Frith CD, Turner R, Frackowiak RS (1995a): Characterizing evoked hemodynamics with fMRI. Neuroimage 2:157–165. Friston KJ, Holmes AP, Price CJ, Buchel C, Worsley KJ (1999): Multisubject fMRI studies and conjunction analyses. Neuroimage 10:385–396. Friston KJ, Holmes AP, Worsley KJ, Poline JP, Frith CD, Frackowiak RSJ (1995b): Statistical parametric maps in functional imaging: A general linear approach. Hum Brain Mapp 2:189 –210. Golier J, Yehuda R (2002): Neuropsychological processes in post-traumatic stress disorder. Psychiatr Clin North Am 25:295–315. Gu H, Feng H, Zhan W, Xu S, Silbersweig DA, Stern E, et al (2002): Single-shot interleaved z-shim EPI with optimized compensation for signal losses due to susceptibility-induced field inhomogeneity at 3 T. Neuroimage 17:1358 –1364. Gurvits TV, Shenton ME, Hokama H, Ohta H, Lasko NB, Gilbertson MW, et al (1996): Magnetic resonance imaging study of hippocampal volume in chronic, combat-related posttraumatic stress disorder. Biol Psychiatry 40:1091–1099. Ikegaya Y, Saito H, Abe K (1996a): The basomedial and basolateral amygdaloid nuclei contribute to the induction of long-term potentiation in the dentate gyrus in vivo. Eur J Neurosci 8:1833–1839. Ikegaya Y, Saito H, Abe K (1996b): Dentate gyrus field potentials evoked by stimulation of the basolateral amygdaloid nucleus in anesthetized rats. Brain Res 718:53– 60. Isenberg N, Silbersweig D, Engelien A, Emmerich S, Malavade K, Beattie B, et al (1999): Linguistic threat activates the human amygdala. Proc Natl Acad Sci U S A 96:10456 –10459. LaBar KS, Gatenby JC, Gore JC, LeDoux JE, Phelps EA (1998): Human amygdala activation during conditioned fear acquisition and extinction: A mixed-trial fMRI study. Neuron 20:937–945. LeDoux J (1996): Emotional networks and motor control: A fearful view. Prog Brain Res 107:437– 446. LeDoux JE (2000): Emotion circuits in the brain. Annu Rev Neurosci 23:155–184. LeDoux JE, Gorman JM (2001): A call to action: Overcoming anxiety through active coping. Am J Psychiatry 158:1953–1955.

X. Protopopescu et al Liberzon I, Taylor SF, Amdur R, Jung TD, Chamberlain KR, Minoshima S, et al (1999): Brain activation in PTSD in response to trauma-related stimuli. Biol Psychiatry 45:817– 826. McKiernan KA, Kaufman JN, Kucera-Thompson J, Binder JR (2003): A parametric manipulation of factors affecting task-induced deactivation in functional neuroimaging. J Cogn Neurosci 15:394 – 408. McNally RJ (1997): Implicit and explicit memory for trauma-related information in PTSD. Ann N Y Acad Sci 821:219 –224. Morgan MA, Romanski LM, LeDoux JE (1993): Extinction of emotional learning: Contribution of medial prefrontal cortex. Neurosci Lett 163:109 –113. Morris JS, Frith CD, Perrett DI, Rowland D, Young AW, Calder AJ, et al (1996): A differential neural response in the human amygdala to fearful and happy facial expressions. Nature 383:812– 815. Orr SP, Lasko NB, Shalev AY, Pitman RK (1995): Physiologic responses to loud tones in Vietnam veterans with posttraumatic stress disorder. J Abnorm Psychol 104:75– 82. Packard MG, Cahill L, McGaugh JL (1994): Amygdala modulation of hippocampal-dependent and caudate nucleus-dependent memory processes. Proc Natl Acad Sci U S A 91:8477– 8481. Phelps EA, O’Connor KJ, Gatenby JC, Gore JC, Grillon C, Davis M (2001): Activation of the left amygdala to a cognitive representation of fear. Nat Neurosci 4:437– 441. Pitman RK, Shin LM, Rauch SL (2001): Investigating the pathogenesis of posttraumatic stress disorder with neuroimaging. J Clin Psychiatry 62(suppl 17):47–54. Quirk GJ, Russo GK, Barron JL, Lebron K (2000): The role of ventromedial prefrontal cortex in the recovery of extinguished fear. J Neurosci 20: 6225– 6231. Rauch SL, Shin LM, Segal E, Pitman RK, Carson MA, McMullin K, et al (2003a): Selectively reduced regional cortical volumes in post-traumatic stress disorder. Neuroreport 14:913–916. Rauch SL, Shin LM, Wright CI (2003b): Neuroimaging studies of amygdala function in anxiety disorders. Ann N Y Acad Sci 985:389 – 410. Rauch SL, van der Kolk BA, Fisler RE, Alpert NM, Orr SP, Savage CR, et al (1996): A symptom provocation study of posttraumatic stress disorder using positron emission tomography and script-driven imagery. Arch Gen Psychiatry 53:380 –387. Rauch SL, Whalen PJ, Shin LM, McInerney SC, Macklin ML, Lasko NB, et al (2000): Exaggerated amygdala response to masked facial stimuli in posttraumatic stress disorder: A functional MRI study. Biol Psychiatry 47:769 –776. Reiss S, Peterson RA, Gursky DM, McNally RJ (1986): Anxiety sensitivity, anxiety frequency and the predictions of fearfulness. Behav Res Ther 24:1– 8. Roozendaal B, McGaugh JL (1997): Basolateral amygdala lesions block the memory-enhancing effect of glucocorticoid administration in the dorsal hippocampus of rats. Eur J Neurosci 9:76 – 83. Rothbaum BO, Meadows EA, Resick P, Foy DW (2000): Cognitive-behavioral therapy. In: Keane T, editor. Effective Treatments for Posttraumatic Stress Disorder: Practice Guidelines from the International Society for Traumatic Stress Studies. New York: Guilford, 60 – 83. Rothbaum BO, Mellman TA (2001): Dreams and exposure therapy in PTSD. J Trauma Stress 14:481– 490. Rothbaum BO, Schwartz AC (2002): Exposure therapy for posttraumatic stress disorder. Am J Psychother 56:59 –75.

BIOL PSYCHIATRY 2005;57:464 – 473 473 Schuff N, Neylan TC, Lenoci MA, Du AT, Weiss DS, Marmar CR, et al (2001): Decreased hippocampal N-acetylaspartate in the absence of atrophy in posttraumatic stress disorder. Biol Psychiatry 50:952–959. Shalev AY, Orr SP, Peri T, Schreiber S, Pitman RK (1992): Physiologic responses to loud tones in Israeli patients with posttraumatic stress disorder. Arch Gen Psychiatry 49:870 – 875. Shin LM, Kosslyn SM, McNally RJ, Alpert NM, Thompson WL, Rauch SL, et al (1997): Visual imagery and perception in posttraumatic stress disorder. A positron emission tomographic investigation. Arch Gen Psychiatry 54: 233–241. Shin LM, McNally RJ, Kosslyn SM, Thompson WL, Rauch SL, Alpert NM, et al (1999): Regional cerebral blood flow during script-driven imagery in childhood sexual abuse-related PTSD: A PET investigation. Am J Psychiatry 156:575–584. Shin LM, Orr SP, Carson MA, Rauch SL, Macklin ML, Lasko NB, et al (2004): Regional cerebral blood flow in the amygdala and medial prefrontal cortex during traumatic imagery in male and female Vietnam veterans with PTSD. Arch Gen Psychiatry 61:168 –176. Shin LM, Whalen PJ, Pitman RK, Bush G, Macklin ML, Lasko NB, et al (2001): An fMRI study of anterior cingulate function in posttraumatic stress disorder. Biol Psychiatry 50:932–942. Spielberger CD, Jacobs G, Russell S, Crane R (1983): Assessment of anger: The State-Trait Anger Scale. In: Spielberger CD, editor. Advances in Personality Assessment, vol 2. Hillsdale, NJ: Lawrence Erlbaum. Spitzer RL, Williams JBW, Gibbon M, First MB (1994): Structured Clinical Interview for DSM-IV - Patient Edition. New York: New York State Psychiatric Institute, Biometrics Research Department. Stein MB, Koverola C, Hanna C, Torchia MG, McClarty B (1997): Hippocampal volume in women victimized by childhood sexual abuse. Psychol Med 27:951–959. Tarrier N, Pilgrim H, Sommerfield C, Faragher B, Reynolds M, Graham E, et al (1999): A randomized trial of cognitive therapy and imaginal exposure in the treatment of chronic posttraumatic stress disorder. J Consult Clin Psychol 67:13–18. Thomas SR, Assaf SY, Iversen SD (1984): Amygdaloid complex modulates neurotransmission from the entorhinal cortex to the dentate gyrus of the rat. Brain Res 307:363–365. Tzourio-Mazoyer N, Landeau B, Papathanassiou D, Crivello F, Etard O, Delcroix N, et al (2002): Automated anatomical labeling of activations in SPM using a macroscopic anatomical parcellation of the MNI MRI singlesubject brain. Neuroimage 15:273–289. Vermetten E, Bremner JD (2002): Circuits and systems in stress. II. Applications to neurobiology and treatment in posttraumatic stress disorder. Depress Anxiety 16:14 –38. Villarreal G, King CY (2001): Brain imaging in posttraumatic stress disorder. Semin Clin Neuropsychiatry 6:131–145. Worsley KJ, Marrett S, Neelin P, Vandal AC, Friston KJ, Evans AC (1996): A unified statistical approach for determining significant signals in images of cerebral activation. Hum Brain Mapp 4:58 –73. Wright CI, Fischer H, Whalen PJ, McInerney SC, Shin LM, Rauch SL (2001): Differential prefrontal cortex and amygdala habituation to repeatedly presented emotional stimuli. Neuroreport 12:379 –383.

www.elsevier.com/locate/biopsych