Abnormal contextual modulation of visual contour detection in patients with schizophrenia

“Stimuli were presented using MATLAB (The MathWorks) and Psychtoolbox [32,33] software on a MacMini running OSX.”

“Stimuli were presented using MATLAB (The MathWorks) and Psychtoolbox [32,33] software on a MacMini running OSX.”

“BPRS scores were significantly lower among the healthy control group compared with both patients and first-degree relatives, Tukey’s HSD, p 0.05.”

“Further, diminished surround suppression effects have been found to correlate with lower γ-aminobutyric acid (GABA) concentrations in schizophrenia, as measured by magnetic resonance spectroscopy (MRS) [52], lending support to the hypothesis that schizophrenia is related to disruptions in GABAergic inhibition [53].”

“All participants had psychiatric functioning assessed using the Brief Psychiatric Rating Scale (BPRS) [28], with controls and relatives additionally completing the Schizotypal Personality Questionnaire (SPQ) [29].”

“psychophysical [2–4], electrophysiological [5], and”

“Medication dosages for schizophrenia patients were converted to Chlorpromazine equivalents (in milligrams) [31].”

“In addition, abnormal electrophysiological activity within visual cortex has been observed in schizophrenia during illusory contour/Gestalt perception [54–56].”

“that occipital signal abnormalities were associated with visual hallucinations [56].”

“Both contour integration and surround suppression have been highlighted as examples of well documented visual abnormalities in schizophrenia whose investigation may provide insight into the neural underpinnings of this disorder [25].”

“This 3-up 1-down staircase converges on a contour detection threshold at the jitter level for which targets are detected with 79% accuracy [34].”

“Future investigations employing spatially localized fMRI and GABA MRS in visual cortex could help elucidate the neural mechanisms underlying these perceptual abnormalities.”

“psychophysical [2–4], electrophysiological [5], and”

“Patients with schizophrenia have trouble organizing perceptual information, and some experience visual hallucinations [48,49].”

“neuroimaging experiments [6].”

“Previous reports of contour integration deficits in schizophrenia have required subjects to locate closed contours at variable positions within the stimulus array [8–12], or to discriminate contour shape configurations [13,35,36].”

“A recent report suggested attentional factors may account for the weak contrast-contrast effect [24] observed when schizophrenia patients reported the perceived contrast of stimuli with and without surrounding context [18] (but see [22]).”

“psychophysical [2–4], electrophysiological [5], and”

“[1]).”

“In addition, abnormal electrophysiological activity within visual cortex has been observed in schizophrenia during illusory contour/Gestalt perception [54–56].”

“Extensive investigations of contextual effects during early visual processing have been made among healthy subjects in past decades, and several groups have recently demonstrated weaker surround suppression effects among patients with schizophrenia compared with controls [18–22]; but see [23,24].”

“Previous reports of contour integration deficits in schizophrenia have required subjects to locate closed contours at variable positions within the stimulus array [8–12], or to discriminate contour shape configurations [13,35,36].”

“Through the use of functional MRI (fMRI), abnormal early visual cortical responses during contour integration have been observed among patients [13], suggesting that schizophrenia leads to disruptions in contour perception at the earliest stages of cortical processing.”

“Previous reports of contour integration deficits in schizophrenia have required subjects to locate closed contours at variable positions within the stimulus array [8–12], or to discriminate contour shape configurations [13,35,36].”

“A recent report suggested attentional factors may account for the weak contrast-contrast effect [24] observed when schizophrenia patients reported the perceived contrast of stimuli with and without surrounding context [18] (but see [22]).”

“Similarly broad tuning has been reported for basic visual responses among schizophrenia patients [40], and others have proposed that broader tuning for stimulus features may underlie abnormal visual masking in schizophrenia [41].”

“As patients with schizophrenia show diminished ODSS effects [20], we predicted that the effect of flanker orientation on contour detection performance would be relatively weaker among patients.”

“Our results agree in part with the findings of Uhlhaas and colleagues [44], who observed poorer contour integration and weaker context modulation of perceived size among nonclinical schizotypal subjects with disordered thoughts.”

“Our findings also agree with previous work showing that symptom remission in patients with disorganized schizophrenia (but not in other psychiatric patients) coincided with improved contour integration [10].”

“psychophysical [2–4], electrophysiological [5], and”

“Extensive investigations of contextual effects during early visual processing have been made among healthy subjects in past decades, and several groups have recently demonstrated weaker surround suppression effects among patients with schizophrenia compared with controls [18–22]; but see [23,24].”

“Extensive investigations of contextual effects during early visual processing have been made among healthy subjects in past decades, and several groups have recently demonstrated weaker surround suppression effects among patients with schizophrenia compared with controls [18–22]; but see [23,24].”

“orthogonal flankers cause less suppression, in agreement with ODSS [14–17].”

“Index Scz (n = 25) Rel (n = 13) Cont (n = 28) Statistics Age (years) 41.8 (11.9) 40.1 (14.7) 45.1 (11.6) F(2,63) = 0.88, p = 0.42 Gender (n)1 Χ2 (2) = 8.24, p = 0.02 Male 4 7 14 Female 21 6 14 Education (years)2 13.5 (1.5) 13.2 (1.4) 15.2 (1.8) F(2,63) = 9.83, p 0.01 Estimated IQ3 (from WAIS-III) 97.8 (17.6) 107 (17.2…”

“One explanation for our pattern of results is that schizophrenia leads to an overall impairment in contour integration, in agreement with previous reports [8–13,35–39].”

“Previous reports of contour integration deficits in schizophrenia have required subjects to locate closed contours at variable positions within the stimulus array [8–12], or to discriminate contour shape configurations [13,35,36].”

“Previous reports of contour integration deficits in schizophrenia have required subjects to locate closed contours at variable positions within the stimulus array [8–12], or to discriminate contour shape configurations [13,35,36].”

“One explanation for our pattern of results is that schizophrenia leads to an overall impairment in contour integration, in agreement with previous reports [8–13,35–39].”

“Extensive investigations of contextual effects during early visual processing have been made among healthy subjects in past decades, and several groups have recently demonstrated weaker surround suppression effects among patients with schizophrenia compared with controls [18–22]; but see [23,24].”

“Similarly broad tuning has been reported for basic visual responses among schizophrenia patients [40], and others have proposed that broader tuning for stimulus features may underlie abnormal visual masking in schizophrenia [41].”

“controls, and interpreted their results within the framework of impaired visual crowding [42].”

“Finally, previous reports have demonstrated normal fixation in schizophrenia [50,51], and fixational instability would not affect contextual modulation.”

“Finally, previous reports have demonstrated normal fixation in schizophrenia [50,51], and fixational instability would not affect contextual modulation.”

“controls during Vernier discrimination, but no difference between groups in the effect of orientation context [45,46].”

“Previous work has also shown impairments among unaffected relatives of schizophrenia patients during visual backward masking [47].”

“One explanation for our pattern of results is that schizophrenia leads to an overall impairment in contour integration, in agreement with previous reports [8–13,35–39].”

“orthogonal flankers cause less suppression, in agreement with ODSS [14–17].”

“Previous reports of contour integration deficits in schizophrenia have required subjects to locate closed contours at variable positions within the stimulus array [8–12], or to discriminate contour shape configurations [13,35,36].”

“controls during Vernier discrimination, but no difference between groups in the effect of orientation context [45,46].”

“As element separation increases, overall contour detection performance should decrease, but flanker effects should decrease more rapidly, resulting in weak or absent contextual modulation at higher spacing [15].”

“Recently, Schallmo et al. (2013) highlighted the abnormal integrative dimension of perceptual organization in schizophrenia, showing that patients’ abilities for contour integration correlated with their surround suppression sensitivity, while these two illusory phenomena had previously only been…”

“Visual Perception Disturbances in Schizophrenia: A Unifi ed Model 90 contextually modulated gain control (Schallmo et al., 2013a ).”

“…patients have demonstrated weaker suppression for contrast (Dakin, Carlin and Hemsley, 2005; Tibber et al., 2013), and size (Uhlhaas et al., 2005, 2006; Silverstein et al., 2013), with mixed evidence on orientation (Schallmo, Sponheim, and Olman, 2013; Tibber et al., 2013; Yoon et al., 2009, 2010).”

“…have shown weaker surround suppression among SZ patients compared with healthy controls (HCs; Dakin et al. 2005; Tadin et al. 2006; Yoon et al. 2009; Robol et al. 2013; Schallmo et al. 2013; Seymour et al. 2013; Tibber et al. 2013; Yang et al. 2013a, b; but see Chen et al. 2008; Barch et al. 2012).”

“…documented in schizophrenia using a wide variety of paradigms (Silverstein et al., 1996, 2013; Must et al., 2004; Dakin et al., 2005; Kéri et al., 2005; Tadin et al., 2006; Uhlhaas et al., 2006b; Chen et al., 2008b; Yoon et al., 2009; Schallmo et al., 2013; Tibber et al., 2013; Yang et al., 2013).”

“…on impaired surround suppression and related phenomena, which are thought to depend upon lateral interconnections in early visual cortex, in schizophrenia, and bipolar disorder (e.g., Must et al. 2004; Dakin et al. 2005; Yoon et al. 2009, 2010; Yang et al. 2012a, 2012b; Schallmo et al. 2013, 2015).”

“…when compared to various healthy and psychiatric control groups (Butler et al., 2013; Feigenson et al., 2014; Keane et al., 2014, 2012; Kozma-Weibe et al., 2006; Schallmo et al., 2013a, 2013b; Schenkel et al., 2005, 2005; Silverstein et al., 2009, 2006, 2012, 2000; Uhlhaas et al., 2006b, 2005).”

“Further, Schallmo et al.[35] have shown that lower IQ levels in the participants with SZ may contribute to inter-group differences in baseline detection performance: IQ scores correlated negatively with detection thresholds and differed significantly between groups.”

“…objection so far is that subjects may be performing worse on Kanizsa shape perception tasks because these individuals have broader orientation tuning curves, making them less sensitive to the slants of the edges that decide contour convexity (Robol et al., 2013; Schallmo, Sponheim, & Olman, 2013).”

“, 2000), and in still other cases, it was less than 4 cycles/deg (Robol et al., 2013; Schallmo et al., 2013).”

“…studies from multiple paradigms in multiple sensory domains have indicated less precise neuronal tuning than among healthy controls (Green, Lee, Wynn, & Mathis, 2011; Harvey et al., 2011; Javitt, Strous, Grochowski, Ritter, & Cowan, 1997; Rokem et al., 2011; Schallmo, Sponheim, & Olman, 2013).”

“In studies of schizophrenia, bipolar disorder, their respective relatives, and controls, surround suppression and contour detection were both found to be weaker in schizophrenia, relatively less weak in bipolar disorder, and functionally spared in both relative groups (57, 58).”

“stimuli in individuals with liability for schizophrenia (Pokorny et al., 2019; Schallmo et al., 2013; Silverstein et al., 2015).”

“Preliminary studies on whether contour perception deficits are present in unaffected first-degree relatives of schizophrenia patients have yielded conflicting findings (Keri et al., 2004; Schallmo et al., 2013), and the presence of such deficts has yet to be investigated in ultra-high risk samples.”

“Group by term interactions of interest involve parameters EEgg|cc,ss and EEgg|cc based on our previous findings that differences in orientation tuning of surround suppression are evident in IPDs [14].”

“We note that the current study failed to find significant differences between the groups on squiggles and lines, which has been observed in previous studies (Robol et al., 2013; Schallmo et al., 2013).”

“Numerous studies have shown evidence of impaired contour integration performance in schizophrenia populations compared to healthy individuals, who are more successful at distinguishing the form of the fragmented shapes 22 – 29 .”

“Behaviorally, schizophrenia individuals exhibit impaired precision in the form of broadened orientation tuning (Yoon et al. 2010; Rokem et al. 2011; Schallmo et al. 2013), hypothesized to re fl ect altered excitation/inhibition (E/I) balance (Krystal et al. 2017) and/or coarsening of representations…”

“Otras formas se perciben como el fondo que avanza y se destaca en relación al centro o un colapso de (53-57) la periferia que se precipita en el centro o el imperio del blanco-negro-brillante .”