Rotational coherent dot movement normalizes spatial disorientation of the subjective visual vertical in patients with rightsided stroke

Author’s Accepted Manuscript Rotational coherent dot movement normalizes spatial disorientation of the subjective visual vertical in patients with rightsided stroke S. Reinhart, A.K. Schaadt, I. Keller, H. Hildebrandt, G. Kerkhoff, K. Utz www.elsevier.com/locate/neuropsychologia

PII: DOI: Reference:

S0028-3932(16)30143-9 http://dx.doi.org/10.1016/j.neuropsychologia.2016.04.027 NSY5974

To appear in: Neuropsychologia Received date: 26 November 2015 Revised date: 26 April 2016 Accepted date: 29 April 2016 Cite this article as: S. Reinhart, A.K. Schaadt, I. Keller, H. Hildebrandt, G. Kerkhoff and K. Utz, Rotational coherent dot movement normalizes spatial disorientation of the subjective visual vertical in patients with rightsided stroke, Neuropsychologia, http://dx.doi.org/10.1016/j.neuropsychologia.2016.04.027 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Rotational coherent dot movement normalizes spatial disorientation of the subjective visual vertical in patients with rightsided stroke

S. Reinhart#1, A. K. Schaadt#1, I. Keller2, H. Hildebrandt3, G. Kerkhoff1, K. Utz4

1

From the Clinical Neuropsychology Unit, Saarland University 2

Dept. of Neuropsychology, Schön Klinik Bad Aibling

3

Dept. of Psychology, Oldenburg University & Zentralkrankenhaus Bremen-Ost 4

Dept. of Neurology, Friedrich-Alexander University Erlangen-Nuremberg

Corresponding authors: Dr. Stefan Reinhart or Dr. A.K. Schaadt, Saarland University, Clinical Neuropsychology Unit, Building A.1.3., D-66123 Saarbruecken, Germany E-mail: [email protected]; [email protected] Phone: +49 681 302 57383, Fax: +49 681 302 57382

# Both authors (SR, AKS) have equally contributed to this publication as first authors (Equal first-author contribution)

Word count: 5847 words total, abstract 231 words, 1 Table, 3 Figures

Abstract Studies in healthy individuals indicate a significant influence of rotating visual motion on judgments of the subjective visual vertical (SVV). Moreover, sensory stimulation manoeuvres like horizontal coherent dot movement significantly modulate horizontal spatial deficits in patients with rightsided stroke. Here, we investigated whether rotational coherent dot movement (RCDM) modulates spatial orientation deficits of the SVV in the roll plane in right hemispheric stroke. We tested the perceptual judgment of the SVV in 20 patients with right-hemispheric, first ever stroke (10 of them with a disorder of the SVV and 10 without a disorder), and 10 healthy, age-matched subjects under three experimental conditions: (1) with a static background of small white dots, (2) with slow clockwise or (3) counterclockwise circular RCDM of these background stimuli. In the baseline condition with static background, the impaired patient group showed a counterclockwise tilt of the SVV. Clockwise RCDM normalized this deficit completely, while with counterclockwise RCDM a slight aggravation was observed. Similar but quantitatively much smaller effects were obtained in the SVV-unimpaired patients and the healthy individuals. These results demonstrate a strong modulatory effect of RCDM on the SVV in patients with a tilt of the SVV due to right-sided stroke. RCDM thus appears to influence higher spatial representations devoted to visuospatial perception of the SVV. Possible mechanisms as well as clinical implications for therapy of visuospatial disorientation (self-orientation in space) after stroke are discussed. Key words: ■ spatial orientation ■ visual vertical ■ visual motion ■ brain damage ■treatment Abbreviations: SVV: subjective visual vertical task (90° orientation); cw: clockwise, ccw: counterclockwise

Introduction Human spatial orientation comprises the veridical perception of the physical vertical as a fundamental ability to orient to gravity (Howard, 1982). Signs of spatial disorientation are frequent after central nervous system injury (Bronstein, 1999). In the frontal (or roll) plane, deficits in the perception of the subjective visual vertical (SVV) have been reported after a variety of lesion sites: brain stem (Dieterich & Brandt, 1993a), thalamic (Dieterich & Brandt, 1993b), and parieto-insular (Brandt, Dieterich, & Danek, 1994) or parietal lesions (Cramon & Kerkhoff, 1993; Kerkhoff & Zoelch, 1998; Kerkhoff, 1999; Darling, Pizzimenti, & Rizzo, 2003) all may cause pathological tilts of the SVV. The direction of this tilt is typically ipsiversive after brain stem lesions (Dieterich & Brandt, 1993a) and contraversive in supratentorial lesions, that is, counterclockwise (ccw) in patients with right hemisphere injury and clockwise (cw) in patients with left hemisphere pathology (Kerkhoff & Zoelch, 1998; Funk et al., 2013; Utz et al., 2011; Oppenlander et al., 2015). Clinically, many studies have shown significant and frequent deficits in the SVV in right hemisphere lesioned patients (De Renzi, 1982; Kerkhoff, 1999; Yelnik et al., 2002; Saj, Honore, Bernati, Coello, & Rousseaux, 2005; Kerkhoff & Zoelch, 1998; Oppenlander et al., 2015; Utz et al., 2011; Funk, Finke, Muller, Utz, & Kerkhoff, 2011). Such perceptual tilts of the SVV are significantly associated with balance recovery after stroke (Bonan et al., 2007) and are significantly correlated to the (poor) ambulation capacity of right hemisphere lesioned stroke patients with left neglect (Kerkhoff, 1999). Furthermore, visuospatial deficits impair functional independence (Mercier, Audet, Hébert, Rouchette, & Dubois, 2001) and are a predictor of unfavourable functional recovery after right hemisphere stroke (Kaplan & Hier, 1982). Many different sources of input contribute to the computation of gravity information (Howard, 1982; Bronstein, 1999). In the visual modality three types of information are important for the sense of verticality: the visual frame (i.e. a tilted rectangular frame around a vertical line), visual polarity (intrinsic up/down information of objects), and visual motion 3

(i.e. rotational motion; cf. Howard & Childerson, 1994). Rotating visual motion (or rotational coherent dot movement, RCDM) around the fixation point influences the perception of verticality in healthy individuals (Hughes & Brecher, 1972; Mauritz, Dichgans, & Hufschmidt, 1977; Howard & Childerson, 1994; Nishida & Johnston, 1999), and leads to a small torsional movement of the eyes in the direction of the roll motion (Kertesz & Jones, 1969). Despite the well-known effects of roll motion, stimulus velocity, and size of the rotating field in healthy individuals little is known about the effects in patients with supratentorial strokes and a pathologically tilted SVV. The investigation of RCDM in the broader context of visuospatial perception might elucidate modulating factors, and thus lead to a better understanding of crucial mechanisms involved in pathological spatial orientation judgments, which finally could identify potential treatments for patients. Horizontal coherent dot movement is known to modulate higher order spatial cognition, such as the perception of the subjective straight ahead (Karnath, 1996), visual size estimation (Schindler & Kerkhoff, 2004), proprioceptive arm position sense (Vallar, Antonucci, Guariglia, & Pizzamiglio, 1993), and tactile perception (Nico, 1999) in patients with right hemispheric lesions. These studies have led to the emergence of novel rehabilitation techniques with active pursuit eye movements (Kerkhoff et al., 2014; Kerkhoff, Keller, Ritter, & Marquardt, 2006; Kerkhoff et al., 2013; Kerkhoff & Schenk, 2012). If RCDM (or roll motion) acts in a similar way on higher order spatial representations in the brain, significant modulation effects on the SVV would be expected both in patients with a tilted SVV after a right sided stroke and - to a smaller extent - also in unimpaired patients and healthy individuals. In analogy to the well-known modulatory effects of horizontal coherent dot movement on leftsided neglect symptoms we thus expect that the effects of RCDM should be marked in patients with a pathological tilt of the SVV but small in patients with a stroke but no tilt of the SVV. We therefore investigated in the present study the modulatory influence of RCDM on perceptual judgments of the SVV in patients with right hemisphere stroke – either with or without a tilt of the SVV - and healthy individuals. We 4

hypothesized that i) cw roll motion normalizes the ccw tilt in the SVV task typically found in right hemisphere lesioned patients whereas ccw roll motion should aggravate this perceptual tilt slightly; ii) Healthy individuals and stroke patients without an impairment in the SVV were expected to show only small and more symmetrical shifts in the SVV towards the direction of roll motion.

Materials and Methods Subjects Ten right handed (according to the German adaptation of a Edinburgh handedness inventory, Salmaso & Longoni, 1985) patients with unilateral, right hemisphere lesions (6 male, 4 female) and ten age-matched, right handed healthy individuals (6 male, 4 female) were tested (see Table 1). Selection criteria for the patients were: a) unilateral, first ever vascular (hemorrhagic or ischemic) lesion of the right cerebral hemisphere, documented by CT/MRI; b) no evidence of a brain stem lesion and no previous neurological or psychiatric disease; c) corrected binocular visual acuity of at least 0.7 (20/30 Snellen; 0.4 m viewing distance). Patients were classified into the SVV impaired group (further termed right brain damaged patients with SVV deficits, RBD+) versus the SVV unimpaired group (RBD-) based on their results in a short screening of the SVV examination prior to the begin of the experimental study. To this purpose, 5 trials with a ccw rotation direction of the test stimulus in the SVV task were conducted using the VS-software, but without background dots. If the results in the constant error of the SVV were >2.8° tilt in either direction (ccw or cw), patients were considered as impaired. Conversely, when the results were within this confidence interval (+/- 2.8°), patients were allocated into the unimpaired group. The cut-off data were derived from normative values in this task obtained by Kerkhoff & Marquardt (1998). All RBD+ patients showed ccw tilts of the SVV (see Table 1). Mean age was 57 years for RBD+ patients, 54 years for RBD-patients and 58 years for healthy controls [F(2, 27) =1.818, p>0.05]. Time since lesion was not significantly different in the two patient 5

groups [t(18)=0.123, p>.05]. We also assessed spatial neglect by three conventional screening tests (line bisection, copying, number cancellation, cf. (Kerkhoff, 2000), for results and explanation see Table 1). Brain lesions were analyzed using the original CT/MRI scans taken from each patient’s brain. Only CT/MRI scans from the post-acute phase (>1 month post

lesion)

were

included.

For

lesion

delineation

the

MRIcron

software

(http://www.sph.sc.edu/comd/rorden/mricron/install.html) was used (results see Fig. 1). Lesion volumes were calculated using the methods described by Rorden & Brett (2000) with this software and overlay plots are given in Figure 1. Lesion volumes were significantly larger in the SVV impaired group [t(18)=3.84, p<.05]. Informed consent was obtained from all subjects prior to investigation. All experiments were performed in accordance with the ethical standards laid down in the 1964 declaration of Helsinki. The study was approved by the local ethics committee (Ärztekammer des Saarlandes, Nr. 147/08, 16.09.2008).

Table 1 and Fig. 1 about here

Experimental Setup Figure 2 illustrates the experimental task. Performance in the SVV (where vertical is defined as 90° and horizontal as 0°) was investigated using computerized software (Kerkhoff & Marquardt, 1998). In the SVV task a 14 x 1.4 cm white bar was presented on a black background in the centre of a computer monitor and had to be positioned to the apparent vertical by verbal commands of the subject to the examiner. Step width was 0.5°. Starting position was +/- 20° away from the veridical vertical (90°). In half of the trials the starting orientation was 70° and thus the stimulus had to be rotated ccw to the true vertical. In the remaining half of trials the starting orientation was 110° and thus the stimulus had to be rotated cw to the vertical. To avoid confusion the rotation direction of the line stimulus and the direction of roll motion (see below) refer to the former starting position or starting 6

orientation, while the background motion conditions always refer to the cw or ccw roll motion. Constant errors (in °) were computed automatically by the software using the method of limits (Engen, 1971). Ten trials were performed in each experimental condition (see below), 5 for each starting position. Subjects were tested in a completely dark room with their head and body upright. The head was fixated in a head- and chinrest to ensure that it remained aligned with the gravitational vertical. Stimuli were shown at a 50 cm viewing distance on a computer monitor (resolution 1024x840). The border of the monitor was covered by a black oval mask to eliminate any visual orientation cues (Figure 2).

Figure 2 about here

Visual rotational motion conditions The SVV task was performed under three experimental conditions: (1) with a static background of 150 randomly distributed white dots (size 2 x 2 mm) on the screen; (2) with cw rotational visual motion (velocity: 9.4°/s) of the background dots, and (3) with ccw rotational motion of the background dots with the same speed (cf. Fig. 2). The static condition was always given first, followed by the two other experimental (roll motion) conditions in a random order. The size of the rotating field within the black mask was 25° horizontally and 20° vertically. Visual motion did not cover or overwrite the stimulus line in the SVV task. A slow velocity was chosen in order to avoid any self-motion sensations in the patients (Deutschlander et al., 2004). Pilot trials had shown that with 9.4°/s and a 25 x 20° display size none of the subjects experienced self-motion sensations (vection) when looking at the motion displays from 0.5 m distance.

Data analysis An Analysis of variance (ANOVA) for repeated measures with the factors motion condition (static background, cw, and ccw rotational visual motion) and starting position of the 7

stimulus (110°, cw rotation vs. 70°, ccw rotation) as within-subject factors, and subject group (SVV impaired as RBD+, SVV unimpaired as RBD-, and healthy controls) as a between-subject factor was performed with the constant error of the SVV as the dependent variable. Results were further analysed with ANOVAs, correlations, and t-tests (two-tailed) and adjusted for multiple sequential comparisons using the procedure by Holm (1979), as well as one-sample t-tests. All analyses were performed with SPSS, version 19.

Results The tilt of the SVV in the baseline measure (without background dot motion) was highly correlated to leftsided deficits in all neglect tests including line bisection (r= 0.59, p = 0.006), copying (r = 0.73, p < 0001), and number cancellation (r = 0.78, p < 0.001). An ANOVA for repeated measures with the factors motion condition and starting position of the stimulus as within-subject factors, and subject group showed significant effects of the factors motion condition [F(2, 54) = 66.50, p < 0.001, ηp = 0.71] and subject group [F(2, 27) = 23.98, p < 0.001, ηp = 0.64], and for the motion condition × subject group interaction [F(4, 54) = 3.58, p = 0.012, ηp = 0.21]. The effect of cw motion was higher in the RBD+ group than in the control groups. As there was neither a significant effect for the factor starting position [F(1, 27) = 0.22, p = 0.645, ηp = 0.01] nor significant interactions with this factor [largest F(4, 54) = 1.65, p = 0.17, ηp = 0.11 for the motion condition × starting position × subject group interaction] the data of the two starting positions were pooled for further analyses. A subsequent ANOVA for the two control groups with the factors motion condition × subject group (RBD- and healthy controls) revealed a significant effect of the factor motion condition [F(2, 36) = 25.91, p < 0.001, ηp = 0.59]. There was no significant effect for the factor subject group [F(1, 18) = 0.88, p = 0.37, ηp = 0.05] and no motion condition × subject group interaction [F(1, 18) = 0.44, p = 0.65, ηp = 0.02]. Therefore, the data of the two 8

control groups were collapsed for further analyses of the motion conditions. Two-tailed ttests (adjusted for multiple sequential comparisons using the procedure by Holm, 1979) revealed significant differences between all comparisons [smallest t(19) = 4.82, p < 0.001 for the no RCDM vs. cw RCDM comparison]. As there was no significant deviation from zero for the SVV in the no RCDM condition [t(19) = 0.47, p = 0.64, mean SVV deviation = 0.15°] but significant deviations for the cw RCDM rotation [t(19) = 5.73, p < 0.001, mean SVV deviation = -5.73°] as well as for the ccw RCDM rotation [t(19) = 4.38, p < 0.001, mean SVV deviation = +4.38°], it can be concluded that RCDM modulated the perception of the SVV towards the direction of the motion. An ANOVA with the factor motion condition showed a significant result for the RBD+ group [F(2,18) = 19.83, p < 0.001, ηp = 0.69]. Subsequent t-tests revealed significant differences between all comparisons [smallest t(9) = 2.71, p = 0.024 for the no RCDM vs. ccw RCDM comparison]. In contrast to the two control groups, a one-sample t-test (against zero) revealed a significant deviation of the SVV also in the baseline condition (no RCDM) [t(9) = 6.96, p < 0.001, mean SVV deviation = 4.58°]. There was also a deviation from zero for the ccw RCDM rotation [t(9) = 7.89, p < 0.001, mean SVV deviation = 6.50°]. For the cw RCDM rotation, there was a deviation of the SVV from zero [t(9) = 3.81, p = 0.004, mean deviation = -1.32°]. However, as there was no difference between the RBD+ group and the control groups [F(2, 29) = 1.21, p = 0.31], it can be concluded that the SVV was nearly normalised under cw RCDM stimulation. Mean errors in the SVV task for the three subject groups and the three experimental conditions are shown in Figure 3.

Fig. 3 about here

Discussion 9

We found high positive correlations between the tilt in the SVV and all neglect tests. These results show, that left visuospatial neglect and the tilt of the SVV are often significantly correlated. We have argued earlier that this frequent association may result from the typically large right-hemispheric lesions causing both disturbances (i.e. Kerkhoff 1999; Oppenländer et al., 2015) Our main finding in this study is that slow, visual roll motion of a small field of dots exerts a strong modulatory influence on the tilt of the SVV in SVV impaired patients due to right-hemispheric, mostly parieto-temporal lesions. Cw roll motion normalized the pathological tilt in the SVV in the impaired RBD+ patients almost completely, whereas ccw roll motion slightly aggravated it. In contrast, only small effects of this manipulation were observed in the unimpaired RBD- patient group and healthy individuals. In sum, our data fully support our hypotheses and suggest a strong influence of sensory stimulation manoeuvres like roll motion on higher order spatial representations involved in the computation of the SVV. We will first discuss possible mechanisms and then implications for recovery and treatment.

Cognitive and neural mechanisms Effects of visual rotating motion on the SVV are well-studied in healthy individuals (Hughes et al 1972; Dichgans, Held, Young, & Brandt, 1972; Held, Dichgans, & Bauer, 1975; Mauritz et al., 1977) using rather fast rotation (20-180°/s) of a large-field visual display (up to 80° per hemifield). These results have been interpreted in terms of visualvestibular interactions. The present study shows that a slowly moving (9.4°/s) and small field of rotating dots (25° x 20°) effectively modulates the perceptual tilts in the SVV task in stroke patients as well. Similarly, though quantitatively smaller effects were obtained in unimpaired patients and healthy individuals. Several studies have shown significant interactions between roll motion and spatial orientation or spatial localization in healthy individuals. For instance, Nishida & Johnston 10

(1999) showed that visual roll motion displaces the perceived orientation of a subsequently viewed vertical windmill-grating into the direction of the previously viewed rotating stimulus. In a related study, Whitney & Cavanagh (2000) showed that roll motion shifted the perceived position of a stationary, flashed stimulus into the direction of the motion. Together, both studies suggest that motion-sensitive cortical areas interact with cortical areas involved either in the computation of the gravitational vertical (i.e. the parieto-insulovestibular cortex, Brandt et al., 1994) or in visuospatial localization of static stimuli (parietooccipital cortex, Ungerleider & Haxby, 1994). Animal studies (Tanaka & Saito, 1989; Sakata et al., 1994) suggest that a variety of anatomical structures within the temporo-parietal cortex are involved in the processing of global visual roll motion or rotating stimuli. Rotation-sensitive neurons in area 7a of the posterior parietal cortex respond to rotation of a single object (Sakata et al., 1994), whereas large-field motion-sensitive cells in the medial superior temporal (MST) cortex respond to large field roll motion and are thought to code the principal body axis during self-motion in the environment (Tanaka & Saito, 1989). Imaging studies in healthy individuals confirm that the human temporo-parieto-occipital cortex is activated by rotating visual stimuli (Haug, Baudewig, & Paulus, 1998). A recent study (Delon-Martin et al., 2006) used high-density event-related potentials to study the cortical activations induced by different types of translational and rotational visual motion. With a cw rotating visual display similar to ours the authors found the right superior and inferior posterior parietal cortex, right inferior occipital cortex, and left middle temporal gyrus to be significantly more active during roll as compared to linear motion. In a related fMRI study (Kleinschmidt et al., 2002) higher-order parietal and temporo-occipital areas were critically involved when the subjects viewed visual roll motion. Finally, a PET-study found stronger activations with roll motion as compared to linear motion in the precuneus, parietal, and temporal cortical areas, with a clear righthemisphere preponderance (Deutschlander et al., 2004). The mentioned imaging studies with healthy individuals suggest that multiple brain regions – with a key role of the parieto11

temporal cortex – respond to circular visual motion displays in the normal brain. Interestingly, parieto-temporal cortex regions were also found to be crucially involved in judgments of the SVV in healthy individuals (Lopez, Mercier, Halje, & Blanke, 2011). As posterior parietal cortex was intact in most of our RBD+ patients (see above) functional remnants of this region and other parts of this distributed network may “survive” even in a large right-hemispheric brain lesion. These spared remnants may be crucially involved in the beneficial effect of cw rotating visual motion on the tilt of the SVV. Such rotating motion could shift the perceived SVV via attentional mechanisms into a cw or ccw direction depending on the direction of motion. A similar effect of horizontal linear motion has been suggested as an explanation of the lasting therapeutic effect in patients with left visual neglect (Kerkhoff et al., 2013; Kerkhoff et al., 2014). As in these studies the modulating effect of roll motion was much more pronounced in patients with neglect (the RBD+ group) versus those patients without neglect (the RBD- group). This stronger modulation in the impaired patient group can be explained by a loss of spatial orientation constancy of the SVV (as suggested earlier by Funk et al 2010 for a similar phenomenon) and in contrast, a greater spatial orientation constancy in the unimpaired patient group and in the healthy control subjects. In turn, such a reduced constancy will result in greater variability, less precision and greater modifiability by external cues (such as roll motion).

Implications for recovery and treatment Pathological tilts of the SVV task are significantly related to a number of “spatially” related, functional tasks crucial for daily living, such as ambulatory capacity in left hemiplegic patients (Birch, Proctor, Bortner, & Lowenthal, 1960; Birch, Belmont, Reilly, & Belmont, 1961; Kerkhoff, 1999), visuo-constructive deficits (Mack & Levine, 1981; Griffiths & Cook, 1986), analogue clock reading and spatial dysgraphia (Funk et al., 2013). Moreover, it is well established that visuospatial deficits hamper activities of daily living (Kaplan & Hier, 1982) in patients with right-sided brain lesions. Therefore, the positive and 12

rather quick effect of visual roll motion on spatial disorientation of the SVV may offer a viable treatment option for these patients. Bottom-up sensory stimulation techniques have emerged in the past two decades into rather successful treatment options for patients with left spatial neglect (for review see Kerkhoff & Schenk, 2012). More specifically, horizontal coherent dot movement is known to reduce spatial neglect deficits significantly stronger than conventional scanning training (Kerkhoff et al., 2013; Kerkhoff et al., 2014) and that it enhances rehabilitative effects when combined with theta-burst stimulation (Hopfner et al., 2015). However, treatment techniques for spatial-cognitive disorders apart from those for hemineglect or extinction are not highly developed yet. In a recent study, Funk et al (2013) showed that perceptual relearning based on error-feedback significantly reduced the perceptual tilts in the SVV in patients with right hemisphere stroke. Moreover, another recent study (Oppenländer et al., 2015) showed that subliminal galvanic-vestibular stimulation rapidly (within 20 min) reduced the errors in the visual and haptic subjective vertical in patients with rightsided stroke. Likewise, our present results indicate that visual roll motion has similar modulating effects on the tilted SVV as horizontal coherent dot movement on the left-right (horizontal) spatial deficits in patients with left neglect. As an aside, it is interesting to mention that nearly all patients in our RBD+ patient group had also signs of left spatial neglect to some extent. This frequent association between neglect and tilts of the SVV has been repeatedly found (Kerkhoff, 1999, Rousseaux, Honore, Vuilleumier, & Saj, 2013) and may be explained by the typically large parieto-temporal and/or subcortical lesions (as in our RBD+ patients) which damage neuronal structures that lead to both neglect and a tilt of the SVV. As the areas of greatest lesion overlap in our post-acute RBD+ patients (Fig. 1) lay in the right frontal and superior insular cortex the right posterior parietal cortex was spared in most of these patients. This differs partially from lesion studies conducted in acute stroke patients with a tilt of the SVV (Baier, Suchan, Karnath, & Dieterich, 2012). Regardless of these differences, the present investigation shows that cw roll motion restores the perception of the SVV in rightsided 13

stroke. As disorders of the SVV are quite frequent after right hemisphere brain lesions (Hier, Mondlock, & Caplan, 1983) and are critically related to the patients’ motor performance and general functional outcome (Mercier et al., 2001), repetitive rotatory RCDM might in the future become – similar as repetitive horizontal coherent dot movement for neglect (Kerkhoff et al., 2013; Kerkhoff et al., 2014) – a promising treatment option for visuospatial deficits after stroke. Table 1: Clinical and demographic data of 20 patients with right hemisphere stroke (10 SVV impaired, 10 SVV unimpaired). Subject

Age, Sex

Etiology, TSL (months)

Lesion Site / volume in 3 mm

1 2

56,f 44, m

I ,8 I, 12

3 4

48,f 70,m

H, 4 I, 4

5

50,f

I, 2

6 7

50,f 70,m

I, 2 I, 3

8 9 10

61,m 58,m 63,f Mean Age: 57.0

I, 3 H, 4 I, 3 Mean TSL: 4.5

T, P,sc/18.9 F,T,P, I/134.4 Sc/19.6 F, T, P, T, sc/112.0 T, P, I, sc/87.5 T, P/30.8 T, P, sc/95.2 T, sc/27.3 T, P/96.6 T, P/87.5 Mean Volume: 80.0

RBD+

Visual Field Sparing (°) HH, 2° HH, 15°

Motor Deficit

LB

Neglect Copy L/R

Cancell. L/R

Tilt in SVV(°) Baseline

Left Left

-8 +9

-/+ -/+

6/1 4/1

6.5 7.2

HH, 3° HH, 20°

-Left

+4 +6

-/+ -/+

4/1 5/4

7.5 3.0

HH, 15°

Left

+10

-/+

5/0

3.0

-HH, 40°

Left Left

+45 +43

-/+ -/+

23/3 11/0

9.5 3.3

HH, 2° -HH, 17° Impaired: 8

Left Left Left Impaired:9

+20 +63 +53 Mean LBE: +26

-/+ -/+ -/+ Impaired: 10

16/8 10/4 8/4 Mean Om.: 9.2/2.6

3.0 4.5 5.2 Mean Tilt: 5.3

RBD11 12 13 14 15 16 17 18 19 20

57,f I, 3 O/28.0 HH, 3° --8 +/+ 0/0 0.8 53,m I, 2 O/2.8 HH, 3° --12 +/+ 0/0 2.0 63,m I, 3 O/0.7 HH, 3° --11 +/+ 0/0 1.0 50,f I,15 O/11.2 HH, 2° --10 +/+ 0/0 2.0 31,f I, 2 O/28.0 HH, 3° --2 +/+ 0/0 0.5 45,m I,3 O/12.6 HH, 3° --8 +/+ 0/0 1.5 68, m H,2 T, BG/32.2 -Left +4 +/+ 0/0 1.0 55,m H,7 BG/30.1 -Left +3.5 +/+ 0/0 0.8 57,m H,7 BG/17.5 -Left +4 +/+ 0/0 0.3 61,m I,3 T/9.8 -Left +2,5 +/+ 0/0 0.3 Mean Mean Mean Impaired: Impaired: Mean Impaired: Mean Mean Age: TSL: 4.7 Volume: 6 4 LBE: 0 Om.: Tilt: 1.0 54.0 17.3 -3.9 0/0 TSL: Time since lesion; I: ischemic; H: hemorrhagic; sc: subcortical; O/P/T/F; occipital, parietal, temporal; frontal; Visual Field Sparing(°): intact visual field (°) on the affected side. Neglect Screening Tests: LB: line bisection of a 20 cm horizontal line; the deviation from the true midline is given (in mm; +/- = right/leftsided deviation; normal cut-off: +/- 5 mm); Copy: copy of a star: -: leftsided omissions or size distortions, +: normal copy on right side of figure; Cancell.: cancellation of 30 numbers embedded in 200 distractors: L/R: the number of left/rightsided omissions is given; normal cut-off: 1 omission per hemifield. SVV: Subjective Visual 14

Vertical: positive values indicate counterclockwise tilt of SVV in the initial baseline test (see text for more details).

Figure Captions

Figure 1: Lesion areas of the 20 patients with right-hemisphere stroke, according to the method of Rorden & Brett (2000).

Figure 2: Outline of the experimental tasks used (upper part) and the visual background motion conditions (lower part). Experimental tasks: The dotted lines indicate the correct orientation of the test line. Deviations to the left side are scored as counterclockwise errors, deviations to the right side as clockwise errors (see arrows). Note that the dotted lines are not visible on the screen. Motion conditions: A static visual background, clockwise, or counterclockwise rotational motion of the dots around the line of sight were shown in separate experimental sessions with a velocity of 9.4°/s.

Figure 3: Mean constant errors (in °; +/- 1 standard error of the mean; averaged from 10 trials) in the SVV task in 10 SVV impaired patients, 10 SVV unimpaired patients, and 10 healthy individuals. Positive constant errors denote counterclockwise tilts, negative errors denote clockwise tilts. Error bars reflect standard deviations.

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Research Highlights  Perceptual tilts of the subjective visual vertical (SVV) are frequent after rightsided stroke  We examined the effects of rotating visual motion on the SVV in 20 stroke patients and healthy individuals.  Counterclockwise tilts of the SVV after rightsided stroke can be transiently normalized by clockwise rotating visual motion  Our study shows that rotating optokinetic stimulation may be a viable treatment option for patients with spatial disorientation of the SVV after rightsided stroke.

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