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1 AUTHOR S QUERY SHEET Author(s): MICHEL et al. PCNP Article title: Article no: Dear Author Some questions have arisen during the preparation of your manuscript for typesetting. Please consider each of the following points below and make any corrections required in the proofs. Please do not give answers to the questions on this sheet. All corrections should be made directly in the printed proofs. AQ1 AQ2 AQ3 Please re-work the Abstract under the headings of Introduction, Methods, Results and Discussion. Please confirm correct spelling. Heilman, K. M., Bowers, D., Coslett, H. B., Whelan [ OR Whelam? ], H., & Watson, R. T. (1985). Directional hypokinesia: Prolonged reaction times for leftward movements in patients with right hemisphere lesions and neglect. Neurology, 35, Please clarify this sentence. It was as if spontaneous leftward orientation of attention was equivalent to this made with explicit left-side cue which allows only an effect of right cue.

2 C:/3B2WIN/temp files/pcnp203232_s100.3d[x] Friday, 5th January :14:34 COGNITIVE NEUROPSYCHIATRY 2007, 00 (00), 114 Pseudoneglect in schizophrenia: A line bisection study with cueing AQ1 Carine Michel Espace et Action, Bron, Hôpital Neurologique, Lyon, and Université de Bourgogne, Dijon, France Céline Cavezian Espace et Action, Bron, Université Claude Bernard Lyon, Bron, and Hôpital Neurologique, Lyon, France Thierry d Amatoand and Jean Dalery Université Claude Bernard Lyon, Bron, and Hôpital Neurologique, Lyon, France Gilles Rode Espace et Action, Bron, Service de Rééducation Neurologique, Hôpital Henry Gabrielle, Lyon, and Hôpital Neurologique, Lyon, France Mohamed Saoud Université Claude Bernard Lyon, Bron, and Hôpital Neurologique, Lyon, France Yves Rossetti Espace et Action, Bron, Service de Rééducation Neurologique, Hôpital Henry Gabrielle, Lyon, and Hôpital Neurologique, Lyon, France Numerous authors have reported the existence of lateralised abnormalities towards the right side in patients with schizophrenia. In the present study, a manual line bisection task was used to assess the existence of a visuospatial bias in patients with Gilles Rode, Mohamed Saoud, and Yves Rossetti contributed equally to this study. Correspondence should be addressed to Carine Michel, INSERM-ERM 207 Motricité Plasticité, Université de Bourgogne BP 27877, F Dijon, France; The authors wish to thank Dr James Danckert for commenting on an earlier version of this manuscript. This work was supported by funds from Fondation Berthe Fouassier (CM), Fondation pour la Recherche Médicale (CM), and Conseil Scientifique de la Recherche (CSR) du Vinatier. # 2007 Psychology Press, an imprint of the Taylor & Francis Group, an informa business DOI: /

3 C:/3B2WIN/temp files/pcnp203232_s100.3d[x] Friday, 5th January :14:35 2 MICHEL ET AL. schizophrenia as compared to healthy subjects and left unilateral neglect patients. In addition, we used a local cueing paradigm (consisting of a number placed on the right, on the left, or at both ends of the line). Healthy subjects showed a leftwards trend in the no cue condition (known as pseudoneglect) and neglect patients showed a right bias in all cue conditions. In contrast, patients with schizophrenia placed their manual estimation of the centre further to the left than healthy subjects in all cue conditions, reflecting neglect of the right side of the line. Moreover, like healthy subjects and neglect patients, patients with schizophrenia were affected by the local cueing. Hence, patients with schizophrenia show a bias in their spatial representation, which does not interfere with local context processing. INTRODUCTION Patients with schizophrenia show various deficits in numerous functions (e.g., Harvey, Bowie, & Friedman, 2001; Keefe et al., 2004; for review see Gold & Weinberger, 1995). One of the models proposed to explain these deficits suggests that schizophrenia is related to an anomaly in processing contextual information over time (Cohen & Servan-Schreiber, 1992; Elvevag, Duncan, & McKenna, 2000). In addition, patients with schizophrenia also exhibit motor deficits, independent of their medication regime (Wolff & O Driscoll, 1999). In order to examine the relation between cognitive deficits and motor abnormalities, several studies have explored performance on tasks involving perception and action within a simple context (Saoud et al., 2000). There is much evidence indicating a lateralised visuospatial impairment in patients with schizophrenia, directed towards right hemispace. For instance, Bracha, Cabrera, Karson, and Bigelows (1985) reported a predominance of visual hallucinations in the right visual field. Furthermore patients exhibited a shift in orienting attention with a specific deficit in orienting to visual targets in the right visual field (Bustillo et al., 1997; Harvey, Nelson, Haller, & Early, 1993; Maruff, Hay, Malone, & Currie, 1995; Posner, Early, Reiman, Pardo, & Dhawan, 1988; Wigal, Swanson, & Potkin, 1997). Such a shift in attentional orienting towards left hemispace may be responsible for a perceptual leftward bias in the greyscales task (a sensitive measure of asymmetries in visual processing) in late-onset patients with schizophrenia (Bellgrove et al., 2004). Leftward spatial asymmetries have also been shown in tactile estimation of the centre of a rod while patients were blindfolded (Harvey et al., 1993) and in circling behaviour (Bracha, 1987). Leftward biases in line bisection with the left hand were also shown in healthy subjects with high magical ideation scores (Mohr, Bracha, & Brugger, 2003). Taken together with the asymmetries in visuospatial processes, it has been suggested that schizophrenia may reflect a subtle form of right-sided neglect

4 C:/3B2WIN/temp files/pcnp203232_s100.3d[x] Friday, 5th January :14:35 PSEUDONEGLECT IN SCHIZOPHRENIA 3 AQ2 (e.g., Maruff et al., 1995). In contrast, in the field of neurology, right-brain damaged patients typically with lesions to the parietal lobe, suffer from left unilateral spatial neglect. This syndrome seems to implicate several components such as attention (Kinsbourne, 1970; Posner, Walker, Friedrich, & Rafal, 1984, 1987; Reuter-Lorenz, Kinsbourne, & Moscovitch, 1990), and/ or representation (Bisiach, Bulgarelli, Sterzi, & Vallar, 1983; Bisiach & Luzzatti, 1978; Rode, Rossetti, & Boisson, 2001; Rode, Rossetti, Li, & Boisson, 1998) and/or motor-intention (Heilman, Bowers, Coslett, Whelam, & Watson, 1985). Nevertheless the major characteristic of this condition is that after an asymmetric brain lesion mainly affecting the right hemisphere (e.g., Vallar & Perani, 1986) patients neglect the contralateral left hemispace. As indicated above, certain information processing deficits in schizophrenia resemble those observed in patients with a mild right hemineglect involving a relative hypofunctionality of the left hemisphere (Downing, Phillips, Bradshaw, Vaddadi, & Pantelis, 1998; Posner et al., 1988). Taken together, these results suggest that contextual information processing deficits in schizophrenia are due to lateralised deficits in perceptual and attentional processes. The aim of the present study was two-fold. First, we directly compared visuospatial asymmetries in patients with schizophrenia with neglect patients and healthy individuals. We used a simple task, the manual line bisection task. This is a spatial judgement task that requires subjects to indicate the centre of a line. This test is one of the most traditional clinical tests used to diagnose and define unilateral neglect (e.g., Bisiach et al., 1983). In healthy subjects, many studies have shown a tendency to place the centre of a line towards the left of true centre (for meta-analysis and review see Jewell & McCourt, 2000). In contrast, patients with left hemineglect, following right hemisphere damage, bisect lines towards the right of true centre (e.g., Schenkenberg, Bradford, & Ajax, 1980). Because patients with schizophrenia might exhibit a left hemisphere dysfunction, we predicted that they may exhibit an exaggerated leftward bias (i.e., with respect to healthy subjects) when bisecting horizontal lines. Second, we investigated the processing of spatial context with a local cueing paradigm. It has been shown that the presence of a left or right side cue (e.g., a letter or number placed on the left or right end of the line) induces a modification of the estimation of the centre of the line towards the cued-side in healthy subjects (e.g., Milner, Brechmann, & Pagliarini, 1992) and in neglect patients (e.g., Riddoch & Humphreys, 1983). Orienting attention towards one end of the line may induce an overestimation of that part of the line. In the present study, we expected a cueing effect in patients with schizophrenia that was qualitatively similar to the cueing effect in healthy subjects but quantitatively smaller than the effect seen in neglect patients.

5 C:/3B2WIN/temp files/pcnp203232_s100.3d[x] Friday, 5th January :14:35 4 MICHEL ET AL. Subjects METHODS Three groups of subjects, with normal or corrected-to-normal vision, participated in this study. All were right-handed except for one ambidextrous patient with schizophrenia. Healthy subjects and patients with schizophrenia gave their informed consent prior to their inclusion in the study in accordance with the local ethics committee. For neglect patients, this test was included in their clinical diagnosis history. Characteristics of each group are presented in Tables 1 3. The group of healthy subjects was composed of eight normal individuals. The mean age of this group was (mean9sd) years. The group of patients with left unilateral spatial neglect was composed of seven patients and the mean age of this group was (mean9 SD) years. The group of patients with schizophrenia was composed of eight patients and the mean age of this group was (mean9sd) The group of neglect patients was significantly older than the two other groups, ANOVA one way, F(2, 20)28.78, p B.001. All patients with schizophrenia met the DSM-IV criteria for schizophrenia and were clinically stable with no change in medication for more than 1 month prior to entering the study. Their clinical symptoms were assessed with the Positive And Negative Syndrome Scale (PANSS; Kay, Fiszbein, & Opler, 1987). Concerning neglect patients, the inclusion criterion was left neglect after right hemisphere ischemic or hemorrhagic stroke (see Table 3 for the lesion sites). Unilateral neglect was assessed using the Behavioural Inattention Test (BIT; Wilson, Cockburn, & Halligan, 1987). This test provides an objective TABLE 1 Demographic and clinical characteristics of the group of control subjects (from C1 to C8) Control subjects Age (years) Gender C1 42 M C2 31 M C3 33 M C4 35 F C5 45 F C6 46 M C7 53 M C8 30 F Mean and ratio /5 SD 8.33 C: control subjects; S: patients with schizophrenia; N: neglect patients; M: male; F: female; SD : standard deviation; /: present; : absent; H: hemorrhagic; I: ischemic; PCA: posterior cerebral artery; MCA: middle cerebral artery; NP: not performed.

6 C:/3B2WIN/temp files/pcnp203232_s100.3d[x] Friday, 5th January :14:35 PSEUDONEGLECT IN SCHIZOPHRENIA 5 TABLE 2 Demographic and clinical characteristics of patients with schizophrenia (from S1 to S8), with positive and negative symptom scores, and medical neuroleptics given on the day Patients with schizophrenia Age (years) Gender PANSS positive symptoms score PANSS negative symptoms score Medication S1 36 F Risperidone 8mg/ Cyamemazine 50 mg S2 47 M Haloperidol 15 mg S3 19 M Haloperidol 15 mg S4 29 F Olanzapine 20 mg S5 31 M Zuclopenthixol 50 mg S6 36 M Flupentixol 40 mg S7 25 F Amilsupride 100mg S8 39 M Zuclopenthixol 20 mg Mean and ratio / SD C: control subjects; S: patients with schizophrenia; N: neglect patients; M: male; F: female; SD : standard deviation; /: present; : absent; H: hemorrhagic; I: ischemic; PCA: posterior cerebral artery; MCA: middle cerebral artery; NP: not performed. and standardised measure of unilateral neglect employing a battery of six conventional subtests (line cancellation, letter cancellation, star cancellation, figure and shape copying, line bisection, and representational drawing). Using the cutoff suggested by the authors (Wilson et al., 1987), a score less than 129 was employed as the operational diagnosis of unilateral neglect. Motor and somatosensory deficits were assessed by clinical examination. Experimental procedure Subjects were comfortably seated in front of a table and were verbally informed about the procedure. The line bisection task is one of several traditional clinical tests commonly used to diagnose and define visual neglect (Bisiach et al., 1983; Halligan & Marshall, 1988). It has the advantage of being simple, quantitative, and reproducible (Halligan, 1995). It consists of a spatial judgement task that requires subjects to indicate the centre of a horizontal line, as accurately as possible using the right hand, by making a mark across the centre of the line that would divide it exactly into two halves. The pen, arm, and hand were positioned so as not to hide any part of the line. Subjects were presented with 24 black horizontal lines (200 mm long and 1 mm wide), which were presented one by one centred on A4 sheets of paper and aligned to the subject s body midline. Of these 24 lines, subsets of 6 lines had either a number at the left end, or at the right end, or at

7 Neglect patients Age (years) Gender TABLE 3 Demographic and clinical characteristics of the neglect patients (from N1 to N7) Type of lesion Lesion sites Time since injury onset (m) Motor deficit Somatosensory deficit N1 65 F I (PCA) Temporal, occipital, cingulate cortices, and lenticular nucleus N2 49 M I (MCA) Posterior parietal, temporal, somatosensory 1 L hemiparesis / 126 parietal, primary motor cortices, and thalamus N3 58 F H Posterior parietal, occipital cortices 2 L hemiparesis 109 N4 67 F H Internal capsule, thalamus 2 L hemiplegia / 84 N5 71 M H Posterior parietal, the somatosensory parietal, 2 L hemiparesis / 109 primary motor cortices, and cingulate cortex N6 71 M H Posterior parietal, somatosensory parietal, 4 L hemiparesis / 57 primary motor, and temporal cortices N7 69 M I (MCA) Temporoparietal region including internal 2 L hemiparesis / NP* capsule, putamen, and corona radiata Mean /4 SD 8.10 BIT score *Patient N7 did not perform the BIT; nevertheless he showed extrapersonal neglect when he was asked to perform line bisection, drawing from memory or copying a daisy, a house or a bicycle. C: control subjects; S: patients with schizophrenia; N: neglect patients; M: male; F: female; SD : standard deviation; /: present; : absent; H: hemorrhagic; I: ischemic; PCA: posterior cerebral artery; MCA: middle cerebral artery; NP: not performed. 6 MICHEL ET AL. C:/3B2WIN/temp files/pcnp203232_s100.3d[x] Friday, 5th January :14:35

8 C:/3B2WIN/temp files/pcnp203232_s100.3d[x] Friday, 5th January :14:35 PSEUDONEGLECT IN SCHIZOPHRENIA 7 both ends ( two cues condition), or no number at either end ( no cue condition). The numbers used were 3, 4, 5, 6, 7, and 9, and they were separated from the end of the line by a 6 mm space. Each number was 9 mm long and 6 mm wide. In the two cues condition, numbers were different but quite similar for optical density (i.e., 3/5, 6/9, 4/7). This precaution was taken in order to avoid any spatial attentional bias. The position for the numbers was counterbalanced in all the cueing conditions. Therefore both in the one cue and two cues conditions the numbers were symmetrically presented. Furthermore, cued and uncued conditions were ordered pseudorandomly. The lines were presented in front of the subject s body midline at a viewing distance of approximately 45 cm. There was no time limit. Data analysis For the line bisection task, the distance between the subject s mark and the objective midpoint was carefully measured to 0.5 mm accuracy. Rightward biases (i.e., rightward errors from the true centre of the line) were given a positive value and leftward biases (i.e., leftward errors from the true centre of the line) a negative value. First, to estimate the performance of subjects on the simple line bisection task, we compared biases of the lines without cues ( no cue condition), using a one-way analysis of variance. The deviation from zero was analysed in each group using a one-tailed t-test. Second, in order to evaluate the influence of the spatial context on line bisection, we analysed the observed bias using a two-way analysis of variance with condition (no cue, two cues, left cue, and right cue) as a within-subject factor, and group (healthy subjects, neglect patients, and patients with schizophrenia) as a betweensubjects factor. The specific effects of each factor were analysed with contrast analyses. In the group of patients with schizophrenia, a correlation analysis (Spearman s rho) was performed between PANSS positive or negative symptoms score and the bisection bias for each condition. All statistics were performed by the Statistica software package (release 5.5, 1999). A 95% confidence interval was used to establish statistical significance. In the results section, mean and standard deviation are presented in parentheses. RESULTS The performance in simple bisection As shown in Figure 1, in the no cue condition, patients with schizophrenia demonstrated a leftward bias in their estimation of the centre of the lines ( 0.48 mm90.40), healthy subjects showed a mild leftward bias ( 0.06 mm90.29), and neglect patients showed a rightward bias (1.53 mm9

9 C:/3B2WIN/temp files/pcnp203232_s100.3d[x] Friday, 5th January :14:35 8 MICHEL ET AL. 1.11). One-way ANOVA showed that performance between the three groups was significantly different, F(2, 20) 18.07, p B.001. Moreover, performance of healthy subjects was not different from zero (p.55), whereas the performance of patients with schizophrenia and neglect patients were significantly different from zero (both ps B.05). The effect of cueing A two-way ANOVA showed a significant main effect of group, F(2, 20) 25.80, p B.001, and a main effect of condition, F(3, 60)6.20, p B.001, on bisection bias. For all three cueing conditions, the performance of patients with schizophrenia was biased to the left ( 0.45 mm90.34) of healthy subjects whose performance was relatively accurate ( 0.06 mm90.36). The performance of neglect patients was always towards the right (1.62 mm9 0.88) of the true centre. With respect to the cue condition, in the one-cue condition (left or right), the subjects response was shifted in the direction of the cued extremity of the line with respect to the no cue or two cues conditions (Figure 1). With left cued lines, healthy subjects showed a small leftward estimation of the centre of the lines ( 0.25 mm90.39), patients with schizophrenia showed a leftward bias ( 0.58 mm90.37), whereas neglect patients showed a rightward bias (1.58 mm91.14). When performance with the left cue condition was compared with the no cue condition, a significant effect was observed only in healthy subjects, F(1, 20)5.22, p B.05. With right cued lines, healthy subjects showed a minor rightward bias (0.12 mm90.41), patients with schizophrenia showed a leftward estimation of the centre of the lines ( 0.32 mm90.33) and neglect patients showed a rightward bias (1.76 mm90.94). When performance in the right cue condition was compared with the no cue condition, a significant effect was observed in healthy subjects, F(1, 20)11.02, p B.05, in patients with schizophrenia, F(1, 20)7.74, p B.05, and in neglect patients, F(1, 20) 14.73, p B.05. There was a difference in performance between left and right cueing conditions for healthy subjects, F(1, 20) 19.82, p B.001, and patients with schizophrenia, F(1, 20) 9.14, p B.01. In the two cues condition, healthy subjects showed near perfect performance ( 0.05 mm9 0.31), patients with schizophrenia showed a moderated leftward estimation of the centre of the lines (0.43 mm90.26) and neglect patients showed a rightward bias (1.53 mm90.62). When performance with no cue and two cues was compared, no significant difference was observed in any of the groups (all ps.5). Furthermore, there was no significant correlation between PANSS positive symptoms and bisection bias regardless of the cue condition

10 C:/3B2WIN/temp files/pcnp203232_s100.3d[x] Friday, 5th January :14:36 PSEUDONEGLECT IN SCHIZOPHRENIA 9 (absolute value for Spearman s rho B0.60). There was no significant correlation for PANSS negative symptoms and bisection biases (absolute value for Spearman s rho B0.35). DISCUSSION The present study assessed the asymmetry of visuospatial functions in patients with schizophrenia in comparison to healthy individuals and neglect patients. To examine the processing of the spatial context, we used a manual line bisection task combined with a local cueing paradigm. Patients with schizophrenia showed an overall leftward bias in the estimation of the centre, healthy subjects showed a minor trend towards a leftward bias, and neglect patients showed a rightward bias. Each group demonstrated a cueing effect suggestive of a capacity for processing spatial contexts. The following discussion will attempt to provide explanations for our main results. The leftward bias observed in patients with schizophrenia might be interpreted as an attentional (Bracha et al., 1985; Bustillo et al., 1997; Posner et al., 1988) or intentional/premotor deficit towards right hemispace. This lateralised impairment may reflect a right hemisphere overactivation or a left hemisphere underactivation (Danckert, Saoud, & Maruff, 2004; Downing et al., 1998) consistent with a right hemineglect in schizophrenic patients (Bracha et al., 1985; Bustillo et al., 1997; Posner et al., 1988). Indeed, a leftward bias in line bisection was reported in right neglect after damage to the left hemisphere (e.g., Beis et al., 2004; Bowen, McKenna, & Tallis, 1999). The present results in line bisection show that patients with schizophrenia and neglect patients suffer from a qualitative lateralised spatial deficit albeit in opposite directions. With respect to cueing, the performance of patients with schizophrenia was influenced by a cue placed at the extremity of the line as was the case for healthy subjects and neglect patients. As was proposed for healthy subjects, cueing by attracting attention on one side of the line may induce an overestimation of that part of the line (Harvey, Pool, Roberson, & Olk, 2000; Mattingley, Pierson, Bradshaw, Philips, & Bradshaw, 1993; Milner et al., 1992). Thus, results from the local cueing task show that patients with schizophrenia are able to process spatial context. The cueing paradigm could also be viewed as a good tool to better understand spatial context processing in schizophrenia. However it should be mentioned here that results in the present group of neglect patients differ from those described in the literature on two points. First, the amplitude of the rightward bias is smaller than the bias classically reported (over 11% of the line length*schenkenberg et al., 1980). Second, right-sided cueing increases the bias as has already been reported (Riddoch & Humphreys,

11 C:/3B2WIN/temp files/pcnp203232_s100.3d[x] Friday, 5th January :14:36 10 MICHEL ET AL. AQ3 1983), although no reduction in the rightward bias was observed from the left cue effect*an effect more often shown in the literature (e.g., Harvey, Milner, & Roberts, 1995; Mattingley et al., 1993). Here the right attentional bias seems not to be strong enough to restrict the effect of the right cue, which is more powerful than the left cue. Concerning patients with schizophrenia, there was an improvement of the bisection bias in the right cue condition but no increase of the bias in the left cue condition. That is, cueing of the neglected extremity of the line improved performance in patients with schizophrenia. It was as if spontaneous leftward orientation of attention was equivalent to this made with explicit left-side cue which allows only an effect of right cue. In healthy subjects, a minor trend towards a leftward bias was observed in the present experiment and is referred to as pseudoneglect, as first described by Bowers and Heilman (1980) and frequently reported since (for a review see Jewell & McCourt, 2000). This leftward bias has been observed in many bisection tasks such as manual bisection (Hausmann, Ergun, Yazgan, & Güntürkün, 2002), tactile-kinaesthetic bisection (Chokron, Bartolomeo, Colliot, & Auclair 2002; Laeng, Buchtel, & Butter, 1996; McIntosh, Rossetti, & Milner, 2002), and perceptual bisection (e.g., McCourt, 2001). However, a few studies did not replicate this finding (Manning, Halligan, & Marshall, Mean Biais (mm) Left Right 2,5 2,0 1,5 1,0 0,5 0,0-0,5-1,0 * * Neglect patients Healthy subjects * * Patients with schizophrenia Left Cue No Cue Right Cue Two Cues Cue Condition Figure 1. Estimation of the bisection bias for the four conditions. White circles represent performance of patients with schizophrenia (mean 9/ SE ). Black squares represent performance of healthy subjects and black circles indicate performance of neglect patients. Dotted line indicates the true centre of the line. Leftward biases are indicated with a negative value and rightward biases with a positive value. Only comparisons between no cue condition and left/right cue condition are shown in the figure.

12 C:/3B2WIN/temp files/pcnp203232_s100.3d[x] Friday, 5th January :14:36 PSEUDONEGLECT IN SCHIZOPHRENIA ; Werth & Pöppel, 1988). Right hemisphere dominance for spatial processing has been proposed to explain the origin of the leftward bias characteristic of pseudoneglect (e.g., Laeng et al., 1996). An advantage of the right hemisphere (or disadvantage of the left hemisphere) has also been proposed as a model to elucidate right hemispatial inattention in patients with schizophrenia as mentioned above. A continuum should be considered in the right-sided inattention from schizotypy to schizophrenia manifestations. Indeed, it was shown that Magical Ideation scores (hallucination-like experiences and delusion-like beliefs) are significantly correlated with the size of the right-sided inattention during tactile (Brugger & Graves, 1997) or implicit line bisections (Taylor, Zach, & Brugger, 2002), with reduced rightsided orientation preferences (Mohr et al., 2003) and with a right-sided inattention for spatial memory (Nalcaci, Kalaycioglu, Cicek, & Budanur, 2000). Hence the leftward bias in patients with schizophrenia in the present experiment might be viewed as a manifestation of what we would term hyperpseudoneglect. Based on pseudoneglect results, we might expect a more pronounced leftward bias in experimental conditions which enhance right hemisphere activation such as the left spatial location of the line or responses made with the left hand (Brodie & Pettigrew, 1996; Scarisbrick, Tweedy, & Kuslansky, 1987). Different versions of line bisection may help to better understand interhemispheric dominance for spatial processing in schizophrenia. In conclusion, patients with schizophrenia showed a mild neglect of right space with a preserved capacity for context processing. Further investigations should examine spatial asymmetries in different clinical subtypes of schizophrenia. Manuscript received 9 December 2005 Revised manuscript received 21 September 2006 REFERENCES Beis, J. M., Keller, C., Morin, N., Bartolomeo, P., Bernati, T., Chokron, S., et al. (2004). Right spatial neglect after left hemisphere stroke: Qualitative and quantitative study. Neurology, 63, Bellgrove, M. A., Collinson, S., Mattingley, J. B., Pantelis, C., Fitzgerald, P. B., James, A. C., & Bradshaw, J. L. (2004). Attenuation of perceptual asymmetries in patients with early-onset schizophrenia: Evidence in favour of reduced hemispheric differentiation in schizophrenia? Laterality, 9, Bisiach, E., Bulgarelli, C., Sterzi, R., & Vallar, G. (1983). Line bisection and cognitive plasticity of unilateral neglect of space. Brain and Cognition, 2, Bisiach, E., & Luzzatti, C. (1978). Unilateral neglect of representational space. Cortex, 14, Bowen, A., McKenna, K., & Tallis, R.C. (1999). Reasons for variability in the reported rate of occurrence of unilateral spatial neglect after stroke. Stroke, 30,

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