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Psychiatry Research 229 (2015) 426–433 Contents lists available at ScienceDirect Psychiatry Research journal homepage: www.elsevier.com/locate/psychres Comparison of visual perceptual organization in schizophrenia and body dysmorphic disorder Steven M. Silverstein a,n, Corinna M. Elliott b, Jamie D. Feusner c, Brian P. Keane a, Deepthi Mikkilineni a, Natasha Hansen b, Andrea Hartmann b, Sabine Wilhelm b a Department of Psychiatry and University Behavioral Health Care, Rutgers University, 151 Centennial Avenue, Piscataway, NJ 08854, USA Department of Psychiatry, Massachusetts General Hospital/Harvard Medical School, Boston, MA, USA c Department of Psychiatry and Biobehavioral Sciences, David Geffen School of Medicine at University of California-Los Angeles, Los Angeles, CA, USA b art ic l e i nf o a b s t r a c t Article history: Received 13 September 2014 Received in revised form 5 May 2015 Accepted 17 May 2015 Available online 27 June 2015 People with schizophrenia are impaired at organizing potentially ambiguous visual information into well-formed shape and object representations. This perceptual organization (PO) impairment has not been found in other psychiatric disorders. However, recent data on body dysmorphic disorder (BDD), suggest that BDD may also be characterized by reduced PO. Similarities between these groups could have implications for understanding the RDoC dimension of visual perception in psychopathology, and for modeling symptom formation across these two conditions. We compared patients with SCZ (n ¼ 24) to those with BDD (n ¼ 20), as well as control groups of obsessive–compulsive disorder (OCD) patients (n ¼20) and healthy controls (n ¼20), on two measures of PO that have been reliably associated with schizophrenia-related performance impairment. On both the contour integration and Ebbinghaus illusion tests, only the SCZ group demonstrated abnormal performance relative to controls; the BDD group performed similarly to the OCD and CON groups. In addition, on both tasks, the SCZ group performed more abnormally than the BDD group. Overall, these data suggest that PO reductions observed in SCZ are not present in BDD. Visual processing impairments in BDD may arise instead from other perceptual disturbances or attentional biases related to emotional factors. & 2015 Elsevier Ireland Ltd. All rights reserved. Keywords: Schizophrenia Body dysmorphic disorder Perception Vision Perceptual organization Obsessive–Compulsive Disorder RDoC 1. Introduction It is increasingly recognized that there is overlap between certain psychiatric syndromes in terms of their genetic, neurobiological, cognitive, behavioral, and phenomenological characteristics (Guilmatre et al., 2009; Bellivier et al., 2013; Doherty and Owen, 2014; Monzani et al., 2014). The mounting evidence for this conclusion has led the National Institute of Mental Health (NIMH) to introduce the Research Domain Criteria (RDoC) initiative (Cuthbert and Insel, 2010; Insel et al., 2010). The rationale behind RDoC is that diagnosis and treatment of mental disorders should not be driven primarily by a focus on signs and symptoms (given their problems with reliability and various forms of validity), but rather, by a focus on dimensions of functioning with known pathophysiological mechanisms. A related implication of RDoC is that the yield of psychopathology research may be more fruitful if studies examine these dimensions across current diagnostic categories. One RDoC dimension that has been studied n Corresponding author. E-mail address: [email protected] (S.M. Silverstein). http://dx.doi.org/10.1016/j.psychres.2015.05.107 0165-1781/& 2015 Elsevier Ireland Ltd. All rights reserved. repeatedly within diagnostic categories is cognition, a subcategory of which is perception. A well-documented visual impairment in schizophrenia (SCZ) is in perceptual organization (PO) – the processes by which individual elements of sensory information are collectively structured into larger units of perceived objects and their interrelations (Palmer, 1999). Over 50 studies have demonstrated reduced PO in SCZ (for reviews, see Uhlhaas and Silverstein (2005), Silverstein and Keane (2011)). Some of these studies suggest that, among psychiatric conditions, PO impairment is specific to SCZ, in that it has not been observed in mixed groups of psychotic patients without SCZ, in non-psychotic patients, or in patients who abuse drugs that are not psychotomimetic (Silverstein and Keane, 2011) [there is debate, however, over whether autism, another neurodevelopmental disorder, is characterized by reduced PO (Dakin and Frith, 2005; Sun et al., 2012)]. Recently, however, perceptual impairments that may be aspects of, or secondary to, reduced PO have been observed in body dysmorphic disorder (BDD), a condition characterized by preoccupation with perceived defects in visual appearance. For example, Feusner et al. demonstrated that BDD patients are impaired at processing low spatial frequency information in faces, and S.M. Silverstein et al. / Psychiatry Research 229 (2015) 426–433 427 demonstrate hypoactivity in occipital regions during processing of low spatial frequency information from own face, other face, and object stimuli (Feusner et al., 2007, 2010a, 2010b, 2010c, 2011). Patients with BDD and individuals with a high degree of body image concern also show a reduced face inversion effect (i.e., a worsening of performance when making judgments about faces that are upended compared to upright faces) (Feusner et al., 2010b; Jefferies et al., 2012; Mundy and Sadusky, 2014). Because the face inversion effect has traditionally been thought to reflect the contrast between rapid configural processing of upright faces versus slower serial processing of inverted faces (Tanaka and Farah, 1993; Tanaka and Sengco, 1997; Freire et al., 2000; Taubert et al., 2011; Peters et al., 2013) (but see Rakover (2013), Civile et al. (2014), Xu and Biederman (2014) for other accounts of the effect), and because low spatial frequency information carries the majority of information about global form (Tanaka and Farah, 1993; Costen et al., 1996; Deruelle and Fagot, 2005), these data suggest a reduction in PO in BDD. Of note, patients with SCZ have shown performance impairments on tasks that are similar to the ones used to study face processing in BDD, including reduced face inversion effects (Schwartz et al., 2002; Chen et al., 2008; Soria Bauser et al., 2012; Tsunoda et al., 2012) (but see Chambon et al. (2006), Butler et al. (2008)), reduced processing of low spatial frequency information in faces (Silverstein et al., 2010), and reduced encoding of the structural features of faces (Turetsky et al., 2007; Tsunoda et al., 2012). To date, however, no studies directly comparing BDD and SCZ on visual perception have been conducted. The purpose of this pilot study was, therefore, to directly compare BDD and SCZ patients on two measures of PO that have repeatedly shown sensitivity to impairments in SCZ: an Ebbinguaus illusion task and a contour integration (CI) task. In addition, a group of obsessive–compulsive disorder (OCD) patients was included to control for obsessive–compulsive features, and to determine whether problems in organizational strategies that have been observed in OCD (e.g., on verbal and visual memory tasks (Deckersbach et al., 2000a, 2000b, 2000c; Savage et al., 2000) could account for task performance in BDD. Psychiatrically healthy controls were also included. 1.1. Ebbinghaus illusion In a typical Ebbinghaus illusion demonstration, the perceived size of a circle is altered when it is surrounded by other circles; it appears larger than its actual size when surrounded by smaller circles and smaller than its actual size when surrounded by larger circles (see Fig. 1). The effect has been known for over 100 years (Titchener, 1902), and has been the subject of numerous experiments, especially since the 1970s (e.g., Massaro and Anderson, 1971; Girgus et al., 1972; Weintraub and Schneck, 1986; Coren and Enns, 1993; Rose and Bressan, 2002; Doherty et al., 2010; Schwarzkopf and Rees, 2013). Patients with schizophrenia have demonstrated reduced illusion effects, expressed as more accurate size perception compared to controls when judging target circle size in misleading context conditions (Uhlhaas et al., 2006; Silverstein et al., 2013; Tibber et al., 2013). This effect is most pronounced when patients have active psychotic symptoms (Silverstein et al., 2013). 1.2. Contour integration CI is one of the most widely used measures of PO in the SCZ and basic vision literatures (Field et al., 1993; Kovacs and Julesz, 1993; Polat et al., 1997; Kovacs, 2000; Chandna et al., 2001). CI is typically measured as the ability to detect or make a judgment about a closed contour made up of non-contiguous elements, embedded Fig. 1. Sample stimuli from each of the 2 conditions (bottom 2 panels) of the Ebbinghaus illusion task. In each case, the target circle on the right is larger than the one on the left. The top panel shows the actual circle sizes, for comparison. within a display of randomly oriented elements (see Fig. 2). Previous studies have shown that people with SCZ are less able to detect and make shape judgments about contours when compared to healthy, psychotic, non-psychotic and non-psychotomimetic substance abusing control groups (Uhlhaas and Silverstein, 2005; Silverstein and Keane, 2011). CI impairment has also been observed in aging (Roudaia et al., 2011), dyslexia (Simmers and Bex, 2001), and amblyopia (Polat et al., 1997), and can be affected by psychotomimetic drugs that affect occipital lobe functioning (Uhlhaas et al., 2007; White et al., 2013). To our knowledge, only one prior study has investigated CI in BDD (Rossell et al., 2014). This recent study found normal performance; however, they used an older, card-based version of the task with only 15 stimuli and a lengthy exposure duration (30 s). In the present study, we used a recently developed computerized version of the CI task with a large number of trials and a relatively brief stimulus duration (Silverstein et al., 2012). 428 S.M. Silverstein et al. / Psychiatry Research 229 (2015) 426–433 2.3. Perceptual organization Tasks 2.3.1. Apparatus Stimuli at the Rutgers site (SCZ and CON groups) were presented on Samsung 2243BWX LCD monitors with viewable dimensions of 47.5 by 29.8 cm. The screen resolution was 1680 1050 pixels, viewing distance was 24 in. (61.0 cm), and therefore, the viewable screen subtended 43° 27° of visual angle. Monitor parameters were a gamma value of 2.2, color temperature (white point) of 6500 K, and luminance of 120 cd/m2. Stimuli at the Massachusetts General Hospital site (BDD and OCD groups) were presented on a Hewlett Packard Compaq nc8430 LCD laptop monitor with a viewable dimension of 33.1 by 20.7 cm. The screen resolution was 1680 1050 pixels, viewing distance was 18 in. (45.7 cm), and the viewable screen subtended 40° 26° of visual angle. Therefore, the stimuli were very similar between sites, but not quite identical—at MGH, one pixel subtended .0247 deg2 and at Rutgers, .0266 deg2 (i.e., MGH stimuli were 93% as large as those at Rutgers). At MGH, monitor parameters were a gamma value of 2.2, color temperature (white point) of 6500 K, and luminance of 112.9 cd/m2. Fig. 2. Sample stimuli from the contour integration test. Top left: 7–8° jitter, leaving a still visible contour. Top right: 15–16° jitter, leaving a contour that most people cannot detect. Bottom left: Catch trial with line drawn through contour, to eliminate the need for grouping. Bottom right: Catch trial with no background, eliminating effects of noise. 2. Methods 2.1. Subjects Four groups participated: (1) outpatients with BDD (n¼20; 11 female); (2) outpatients with OCD (n ¼20, 7 female); (3) inpatients with SCZ (n¼ 24; 11 female); and (4) controls (CON) without a psychiatric disorder (n¼ 20; 10 female). BDD and OCD patients were recruited from specialized clinics at the Department of Psychiatry at Massachusetts General Hospital (MGH). All BDD participants were required to have a score of Z 20 on the BDD version of the Yale–Brown Obsessive– Compulsive Disorder Scale (BDD-YBOCS) (Phillips et al., 1997). All OCD participants were required to have a score of Z 16 on the Yale–Brown Obsessive–Compulsive Disorder Scale (YBOCS) (Goodman et al., 1989a, 1989b). Thirteen BDD patients and 10 OCD patients were taking medication at the time of testing. Patients with schizophrenia were recruited from the adult psychiatric inpatient unit at Rutgers University Behavioral Health Care. All SCZ patients were hospitalized while tested, and were tested within 1 week of admission. All were taking second-generation antipsychotic medication at the time of testing. The CON group was recruited from the local community. Data from 58% of the SCZ and 50% of the CON groups only was included in a prior report (Silverstein et al., 2013). More details on exclusion criteria and patient medications can be found in Supplemental information. 2.2. Clinical assessments SCZ, BDD and OCD diagnoses were confirmed via the Structured Clinical Interview for DSM-IV diagnosis (SCID) (First et al., 2002b), in addition to collateral information obtained from clinical staff and the electronic medical record. BDD and OCD groups only also completed the Brown Assessment of Beliefs Scale (BABS) (Eisen et al., 1998) and the Peters’ Delusional Inventory (PDI) (Peters et al., 1999) to assess insight and delusionality, in addition to the Y-BOCS and BDD-YBOCS as noted above. Symptoms were assessed for the SCZ group with the Positive and Negative Syndrome Scale (PANSS) (Kay et al., 1987) which was scored using a 5 factor model that included orthogonal factors for positive, negative, cognitive, depression, and excitement symptoms (Lindenmayer et al., 1994a, 1994b, 1995a, 1995b). We also derived a separate disorganization factor (Cuesta and Peralta, 1995), and focused specifically on item P2, conceptual disorganization, given prior observed relationships between reduced PO, including CI, and reduced thought organization in SCZ (Uhlhaas and Silverstein, 2005; Silverstein and Keane, 2011). Lack of psychiatric diagnosis for the CON group was confirmed with the SCID, non-patient version (First et al., 2002a). 2.3.2. Ebbinghaus illusion task On each trial, the task was to press a key to indicate whether the target on the left or the right half of the screen was larger (see Fig. 1). All circles were black and presented on a white background. The stimulus appeared on the screen until the subject responded or after two seconds (whichever happened first). If a response was not recorded within 2 s of stimulus onset, the trial was counted as a guess (.5 correct) so as not to penalize subjects who preferred to time-out rather than guess on a trial. Trials were separated by 200 ms. The targets were centered on either side of the screen and appeared with surrounding circles (see below). The two target circles always differed in actual size, and this difference varied in magnitude across trials. As noted, the size of the objects at MGH were 93% the size of the objects at Rutgers. At the Rutgers site, the center circle on one side was always 2.67° of visual angle in diameter, while the center circle on the other side was always .05°, .16°, .27°, .37°, or .48° larger or smaller. The side on which the larger circle appeared was randomized across trials. This size comparison was presented in 2 conditions. (1) In the misleading condition, the target circles were always surrounded by 8 larger circles arranged in a square configuration (i.e., 3 above, one on each side, and 3 below, see Fig. 1). Each of the five size differences was shown sixteen times, with the larger central circle always surrounded by larger circles (for Rutgers 3.33° in diameter) and the smaller central circle always surrounded by smaller circles (for Rutgers 1.33° in diameter). In this condition, size contrast impairs discrimination by biasing the observer to perceive the larger target as smaller and the smaller target as larger (Doherty et al., 2008). (2) In the helpful context condition, the two target circles (for Rutgers 2.61° and 2.72° of visual angle) were presented eight times each, again surrounded by 8 circles around the edges of an imaginary square, with the smaller center circle surrounded by larger circles (for Rutgers 3.33° in diameter) and the larger central circle surrounded by smaller circles (for Rutgers 1.33° in diameter). In this condition, size contrast increases accuracy. Note that in this condition, if subjects choose the array with larger surrounds then they will be wrong on every trial. As in prior studies, only 16 trials were presented in the helpful condition, and they were all at the hardest difficulty level (for Rutgers.05° size difference between center circles) (Phillips et al., 2004; Doherty et al., 2008, 2010). The 96 trials in the context conditions (80 in the misleading and 16 in the helpful conditions) were presented in a different random order for each subject. The primary performance index for this study was that of context sensitivity, defined as the difference between scores in the 16-trial helpful condition and scores in the 16trials from the misleading condition with the same target-surround size difference as in the helpful condition (Silverstein et al., 2013). 2.3.3. Contour integration test Participants were shown static Gabor elements forming an oblong shaped contour embedded in a display of randomly oriented Gabor elements (see Fig. 2). On each trial, participants responded whether the narrow end of the oblong contour was pointing left or right. Perceptual organization was manipulated by adding orientation jitter to the Gabor elements forming the contours, across 6 levels: 7 0°, 7–8°, 9–10°, 11–12°, 13–14°, and 15–16°. For all stimuli, there were 207 noise Gabor, and 15 contour-defining Gabor elements. The ratio of the density of adjacent background elements to the density of adjacent contour elements was .9:1.0. At this level, adjacent background elements are closer together than adjacent contour elements, and thus CI requires integration of activity at the spatial filters corresponding to the Gabor elements; perception of the contour by density cues is not possible at D o1.0. All Gabor elements were identical except for their position and orientation. At Rutgers, the average distance between adjacent elements was 1.0°. The width and wavelength of each element was .2°. At MGH, the average distance between adjacent elements was .93° and the width and wavelength of each element was .186°. Each stimulus was presented for 2 s followed by a 1 s inter stimulus interval during which responses were no longer recorded. Forty-eight stimulus trials per jitter condition were presented in blocks of 12 trials. Two types of catch stimuli (i.e., no errors expected) using 0° jitter were administered during each block to assess momentary attention lapses. One had curved lines drawn through the contours to S.M. Silverstein et al. / Psychiatry Research 229 (2015) 426–433 429 highlight contour salience, and the other contained contour elements without background elements to eliminate distractor noise effects. Blocks were presented in increasing order of difficulty (starting with 0° and ending at 15–16°), and each 6-block sequence was repeated 4 times for a total of 288 experimental and 48 catch trials. Total score across all jitter conditions (excluding catch trials) was used as the performance index as this score has higher test-retest reliability compared to psychometric function threshold values (Strauss et al., 2014). As in prior studies (Silverstein et al., 2012; Feigenson et al., 2014), a timed-out response was scored as .5 correct, to not give any advantage to subjects who preferred to guess rather than time-out on a trial. 2.4. Ethics All procedures contributing to this work comply with the ethical standards of Rutgers and MGH IRBs. All subjects provided written informed consent. 3. Results 3.1. Demographic data Table 1 summarizes demographic and psychometric data. Data on comorbid conditions can be found in Supplemental results. The groups did not differ in sex composition: Pearson's Χ2(3) ¼1.75, p ¼.63. There was a significant between-group difference in age: F(3, 83) ¼3.17, p o.05. Post-hoc Tukey tests indicated that the SCZ group (mean ¼42.25, SD ¼11.16) was significantly older than the BDD (31.55 , 12.36) group, but not the CON (38.1 and 11.86) or OCD (36.10 and 11.29) groups. There were no other significant pairwise differences. 3.2. Ebbinghaus illusion The 4 groups were compared across the helpful and misleading indices with a 4(group) 2(condition) ANOVA with repeated measures on the condition factor. As predicted, there was a significant effect of condition, with accuracy being superior in the helpful context compared to the misleading context condition: F (1.80)¼ 41.16, p o.001, partial eta squared¼.34. The main effect of group was not significant: F(3.80) ¼1.96, p ¼.13, partial eta squared¼.068. However, the group x condition interaction was significant [F(3.80) ¼ 3.39, po .05, partial eta squared¼.11; see Fig. 3]. This interaction was explored by comparing groups on the context sensitivity index. The main effect of group on this index Fig. 3. Ebbinghaus illusion: Context sensitivity values, by group. Error bars represent 1 SD. Dotted line represents post-hoc pairwise group difference at the .01 level of statistical significance. Dashed line represents a pairwise difference at p o.05. was significant [F(3.80) ¼4.23, p o.001, partial eta squared¼ .14]. Pairwise comparisons (Tukey) revealed that the expected group difference between SCZ and CON (SCZoCON) was observed, p¼ .01, replicating past studies of reduced context sensitivity in SCZ. The SCZ group also demonstrated reduced context sensitivity compared to the BDD and OCD groups at close to the.05 level (p values were .049 and .051, respectively). Pairwise comparisons between the BDD, OCD, and CON groups were all associated with p values greater than .95. 3.3. Contour integration test There were no effects of group for either type of catch trial [for line type, F(3.79) ¼ 1.83, p ¼ .15; for no background type, F(3.79) ¼ 2.24, p ¼.09] indicating that all groups were paying adequate attention to the task. On the non-catch trials, the SCZ group had the lowest proportion correct (see Fig. 4). Including all jitter conditions in a mixed model ANOVA (group jitter) revealed the expected main effect of jitter [F(5.395) ¼194.61, po .001], a trend towards a Table 1 Means (SDs) for study variables, by group. Ageb Ebbinghaus – misleading contextb Ebbinghaus – helpful contextb Ebbinghaus – context sensitivityb Contour integration – main trialsn Contour integration – catch trial: line Contour integration – catch trial: no noise Y-BOCSb BDD Y-BOCSb BABSb PDI PANSS – positive PANSS – negative PANSS – cognitive PANSS – excitement PANSS – depression PANSS – disorganization PANS – conceptual disorganization * p ¼ .01. po .05. b po .01. b po .001. b BDD (n¼20) OCD (n¼20) SCZ (n¼24) CON (n¼ 20) 31.55(12.36) 37.39(26.38) 86.14(27.15) 11.15(8.45) 65.38(13.89) 92.71(22.78) 93.54(22.72) 3.25(6.92) 26.65(4.88) 11.15(5.21) 6.50(4.88) ******* ******* ******* ******* ******* ******* ******* 36.10(11.29) 47.21(23.83) 87.17(29.30) 11.10(8.50) 65.89(10.97) 98.33(3.42) 97.71(3.44) 22.75(4.85) 3.90(7.73) 2.70(5.88) 9.2(11.43) ******* ******* ******* ******* ******* ******* ******* 42.25(11.16) 60.77(26.90) 67.40(39.06) 3.88(11.83) 62.80(9.83) 89.93(17.15) 89.93(15.68) ******* ******* ******* ******* 12.13(3.53) 16.79(3.75) 11.38(3.05) 9.54(3.19) 14.04(4.87) 5.96(2.01) 2.13(1.15) 38.10(11.86) 47.13(19.67) 91.48(19.62) 12.60(6.14) 71.35(11.00) 97.50(4.36) 98.33(2.49) ******* ******* ******* ******* ******* ******* ******* ******* ******* ******* ******* 430 S.M. Silverstein et al. / Psychiatry Research 229 (2015) 426–433 Fig. 4. Contour integration test: Proportion accuracy, by group. Error bars represent 1 SD. Solid lines represent group differences at the.001 level of statistical significance in post-hoc pair-wise comparisons. Dashed line represents a pairwise difference at po .05. main effect of group [F(3.79) ¼2.50, p ¼.066], and a non-significant group x jitter interaction [F(15.395) ¼.44, p¼ .97], the latter replicating past studies comparing controls and schizophrenia patients. When total proportion correct (summed across all conditions) was used as the dependent variable, however, a significant effect of group was observed: [F(3.79) ¼ 7.67, po .001]. Post-hoc tests (Tukey) indicated that the SCZ group achieved significantly lower scores than the BDD (p¼ .017), OCD (p ¼.001), and CON (p ¼.001) groups. The BDD and OCD groups did not differ from each other or from the CON group. Further exploratory post-hoc analyses indicated that the groups did not differ in performance at jitter levels 0°, 7°, or 9° (the 3 easiest conditions) or 15° (the most difficult condition). However, at 11° jitter, the SCZ group performed more poorly than the CON group (p¼ .023), and at 13° jitter, the SCZ group performed more poorly than the OCD (p ¼.021) and CON (p ¼.033) groups. Similar results to those reported above were observed when age (which can be inversely correlated with contour integration (Del Viva and Agostini, 2007; Roudaia et al., 2011)) was used as a covariate, and when catch trial scores were used as covariates. 3.4. Relationships between symptoms and task performance for the BDD, OCD, and SCZ groups There were no relationships between task scores and symptoms for any group, with one exception (for the SCZ group) that would not survive correction for multiple comparisons. See Supplemental information for details. 4. Discussion The primary finding from this study was that BDD patients do not perform as schizophrenia patients do on two-well validated measures of PO. Rather, their performance was statistically indistinguishable from that of OCD and psychiatrically healthy control groups. Our results are consistent with earlier studies that found normal performance among BDD patients on tasks that have been previously associated with abnormalities in schizophrenia, (Reese et al., 2011a, 2011b), including a recently published study demonstrating normal CI (Rossell et al., 2014), despite the prevalence of delusional thinking regarding personal appearance in many BDD patients seen in clinical settings (Phillips et al., 2006). One potential implication of these findings is that PO impairment may be somewhat specific to schizophrenia, and perhaps other clearly neurodevelopmental conditions such as autism (Sun et al., 2012) among psychiatric disorders. This has been the conclusion in several earlier studies that used mixed groups of patients with psychotic disorders other than schizophrenia (Silverstein et al., 1996, 2000), patients with non-psychotic psychiatric disorders (Uhlhaas et al., 2006), or people with non-psychotomimetic substance abuse disorders (Place and Gilmore, 1980; Uhlhaas et al., 2006) as control groups, and found normal performance therein. Several limitations of the study must be noted. One is that only two tasks were included. Since scores on different tests involving PO are not always highly correlated (Joseph et al., 2013), and since PO occurs at multiple stages of visual information processing (Palmer et al., 2003), it is possible that it involves multiple components. This raises the possibility that SCZ and BDD could both be impaired, but on different sub-processes, and that the tests we included are not sensitive to BDD-specific impairment. Related to this, it is possible that inclusion of tests on which BDD patients are known to perform poorly (e.g., face inversion (Feusner et al., 2010b)) would have revealed domains of greater similarity between the SCZ and BDD groups. This of course raises the issue of the nature of the perceptual impairment in BDD, which will be addressed below. Second, 13 of the 20 BDD participants, half of the OCD, and all of the SCZ participants were medicated. While antipsychotic medication does not appear to affect PO (Silverstein and Keane, 2011), little is known about the perceptual effects of serotonin reuptake inhibitors, and it is possible that they may have resulted in normalization of underlying perceptual disturbances. A third limitation is that the symptom assessment measures given to the patients differed across diagnostic groups. While the measures used were typical and appropriate for clinical and research assessment of each group, a more thorough evaluation of group similarities and differences in PO might have been possible if data on each of the scales were available for all patients regardless of diagnosis. A fourth limitation is that the display devices used to present the tasks differed across the two sites. We consider it unlikely that the pattern of results we observed is related to this, given the similarity in the tasks’ basic effects across multiple studies (cited above) using these identical tasks within the context of variation in display devices, and therefore in stimulus size and brightness. For the CI task, this includes similar results from studies where controls and patients were each tested at different, non-standardized sites (Kozma-Weibe et al., 2006), where controls and patients were both tested at multiple sites (Silverstein et al., 2012), and where controls and patients were tested at the same single site (Silverstein et al., 2000, 2009). In addition, the luminance measurements of the monitors, and stimulus sizes, at Rutgers and MGH were very similar (e.g., MGH stimuli were 93% as large as Rutgers’). And, importantly, scale invariance (i.e., similarity in results across variations in stimulus size) has been previously demonstrated for the CI task (Hess and Dakin, 1997; Keane et al., 2014). A fifth limitation is that the BDD and SCZ groups differed in age, with the latter group being older. This is potentially problematic because perceptual organization, in the form of contour integration, has been shown to gradually decline with age in later adulthood (Del Viva and Agostini, 2007; Roudaia et al., 2008). However, the overall pattern of findings in the study, especially the expected differences between the SCZ and CON groups, cannot be explained by age since these two groups did not differ in age. A final, and perhaps most important, limitation is that the SCZ group was an inpatient group while the BDD and OCD groups were outpatients. This was a deliberate aspect of the study design, because both tasks included in this study have demonstrated S.M. Silverstein et al. / Psychiatry Research 229 (2015) 426–433 relationships with disorganized and psychotic symptoms in past studies, whereas performance is often much closer to normal after symptom remission (Uhlhaas et al., 2006; Silverstein et al., 2013). This is thought to reflect improvements in underlying mechanisms (computational and neurobiological) that are common to these symptoms and to aspects of abnormal perception, rather than simply the result of reduced interference from symptoms on task performance after symptoms remit (Phillips and Silverstein, 2003). So, rather than simply reflecting greater overall disability in the SCZ group, our findings can be taken as further evidence that schizophrenia-related processes are connected with abnormal PO. We consider it unlikely that the group differences simply reflect inpatient vs. outpatient status, since: (1) among SCZ patients in this study, we observed moderate effects (but at the trend level of evidence) for relationships between poorer context sensitivity (on the Ebbinghaus illusion task) and conceptual disorganization – a symptom that often leads to hospitalization (see Supplemental information), and these effects have been observed at statistically significant levels in several prior studies (Uhlhaas and Silverstein, 2005; Silverstein and Keane, 2011); this symptom is not characteristic of either BDD or OCD, however; (2) CI performance has been shown to be stable from inpatient admission to discharge in SCZ patients, (Feigenson et al., 2014), and so similar results to those we observed can be expected in most outpatients with schizophrenia on the CI task; and (3) other groups of inpatients, including psychotic patients without schizophrenia, people with non-psychotomimetic substance abuse disorders, and brain injured patients with behavior disorders, all perform normally on either or both of the tests used in this study (Silverstein et al., 2000; Uhlhaas et al., 2005, 2006). However, it cannot be ruled out that BDD and/or OCD patients who require hospitalization for their OCD spectrum conditions might perform more abnormally on the two perception tasks compared to the patients included in this study, and so this requires further investigation. A major question raised by the data involves the nature of the perceptual impairment in BDD. While earlier studies (reviewed in the Introduction) suggested an impairment in global form processing that might indicate reduced PO in BDD, the problem may lie elsewhere. For example, recent work on the face inversion effect suggests that it may not be due to an inability to process global features of inverted faces. Rather, it may be due to the more rapid (top-down) application of face-specific schemata during interpretation of sensory information in the upright faces condition (Rakover, 2013). This raises the possibility that high-level perceptual and/or emotional factors in BDD, distinct from PO, may interfere with this process. Alternatively, since in both studies that found reduced face inversion effects in BDD (Feusner et al., 2010b; Jefferies et al., 2012), the differences were due to better performance than controls with inverted faces, yet similar performance with upright faces, it is possible that individuals with BDD may have a tendency to preferentially allocate attention to processing details, particularly when allowed longer viewing durations, even when PO is normal. It is also possible that reduced occipital activation in laboratory perception tasks among people with BDD reflects excessive modulation of feedforward perceptual activity, perhaps driven by emotional factors. This possibility has not yet been studied, although the ability of prefrontal areas to modulate occipital activity is now generally accepted (Cavada et al., 2000; Rainer and Miller, 2000; Petrides et al., 2002; van Turennout et al., 2003; Hasson et al., 2004; Bar et al., 2006; Deshpande et al., 2010; Chaumon et al., 2014; Volberg et al., 2013; Volberg and Greenlee, 2014). Moreover, the amygdala provides input to the frontal cortex that can affect perception (Sabatinelli et al., 2014), and emotion affects the likelihood that arousing information will be processed (Phelps et al., 2006), as well as how quickly it is processed (Ohman et al., 431 2001). The amygdala is also connected to both the ventral and dorsal visual streams; through these pathways, top-down signals may be carried to the visual cortex to enhance visual processing for emotionally salient stimuli (Furl et al., 2013), which may shift balances in global and local processing. In individuals with BDD, Bohon et al. (2012) found associations between brain activity in amygdala and in the ventral visual stream, as well as an association between anxiety and ventral visual stream activity, suggesting that arousal may increase processing of details in this population. In addition, expectations regarding what one will see can affect how much attention is allocated to processing a stimulus (Bressler et al., 2008). These data suggest that heightened emotional activity, especially regarding one's own appearance, excessively modulates the feedforward sweep of visual information, so that perception is excessively dominated by emotion-syntonic schemata. However, hypoactivity in visual association areas in BDD has been observed not only for emotionally-salient stimuli (own and others’ faces) but also for stimuli that are not normally emotionally arousing (e.g., pictures of houses) (Feusner et al., 2011). Finally, several studies of BDD have demonstrated reduced processing of low spatial frequency (LSF) information. While this typically carries information about global form, reduced LSF processing does not necessarily lead to reduced PO. Another function of LSF processing is to direct attention to relevant aspects in the visual field (Bar et al., 2006). It is therefore possible that reduced LSF processing in BDD serves as a setting condition for allocation of visual attention to be driven more by internal factors than by global form, even if global form can be processed normally under many conditions. All of these potential scenarios suggest the possibility of a perception and emotion-mediated attentional bias in BDD that is different from what characterizes schizophrenia, but that can, in some cases, lead to similar clinical phenomena. Conflicts of interest None. 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