The line bisection bias as a deficit of proportional reasoning - evidence from number line estimation in neglect.

This study aimed to investigate whether neurological patients presenting with a bias in line bisection show specific problems in bisecting a line into two equal parts or their line bisection bias rather reflects a special case of a deficit in proportional reasoning more generally. In the latter case, the bias should also be observed for segmentations into thirds or quarters. To address this question, six neglect patients with a line bisection bias were administered additional tasks involving horizontal lines (e.g., segmentation into thirds and quarters, number line estimation, etc.). Their performance was compared to five neglect patients without a line bisection bias, 10 patients with right hemispheric lesions without neglect, and 32 healthy controls. Most interestingly, results indicated that neglect patients with a line bisection bias also overestimated segments on the left of the line (e.g., one third, one quarter) when dissecting lines into parts smaller than halves. In contrast, such segmentation biases were more nuanced when the required line segmentation was framed as a number line estimation task with either fractions or whole numbers. Taken together, this suggests a generalization of line bisection bias towards a segmentation or proportional processing bias, which is congruent with attentional weighting accounts of line bisection/neglect. As such, patients with a line bisection bias do not seem to have specific problems bisecting a line, but seem to suffer from a more general deficit processing proportions.

Vertical and horizontal reading training in patients with hemianopia and its effect on reading eye movements.

Vertical reading training (VRTr) increases reading speed (RS) significantly in patients with hemianopic field defects (HFD). We ask, how eye movements (EM) contribute to this improvement and whether EM-behavior is affected by the side of HFD. Twenty-one patients, randomly assigned to VRTr or horizontal RTr, trained reading single lines from a screen at home, for 4 weeks. In the clinic, we recorded EM while reading short sentences aloud from a screen before training (T1), directly (T2) and 4 weeks afterwards (T3). RS-screen was correlated with RS during reading printed paragraphs (RS-print) to assess the transfer to everyday life. RS-screen and RS-print correlated positively (horizontal: r > 0.8, vertical: r > 0.9) at all times. Vertical RS did not exceed horizontal RS. We found significant negative correlations of EM-variables and RS-print: in right-HFD with the number of forward saccades (T1: r = - 0.79, T2: r = - 0.94), in left-HFD with the steps during return sweeps (T1: r = - 0.83, T2: r = - 0.56). Training effects remained stable at T3. EM-improvement was specific for the RTr and the side of the HFD: in right-HFD fewer forward saccades after VRTr, in left-HFD fewer steps during return sweeps after HRTr. RTr on a screen transfers to reading printed text in real-life situations.Trial registration: The study was retrospectively registered in the German Clinical Trials register: DRKS-ID: DRKS00018843, March 13th, 2020.

Disconnection in a left-hemispheric temporo-parietal network impairs multiplication fact retrieval.

Arithmetic fact retrieval has been suggested to recruit a left-lateralized network comprising perisylvian language areas, parietal areas such as the angular gyrus (AG), and non-neocortical structures such as the hippocampus. However, the underlying white matter connectivity of these areas has not been evaluated systematically so far. Using simple multiplication problems, we evaluated how disconnections in parietal brain areas affected arithmetic fact retrieval following stroke. We derived disconnectivity measures by jointly considering data from n = 73 patients with acute unilateral lesions in either hemisphere and a white-matter tractography atlas (HCP-842) using the Lesion Quantification Toolbox (LQT). Whole-brain voxel-based analysis indicated a left-hemispheric cluster of white matter fibers connecting the AG and superior temporal areas to be associated with a fact retrieval deficit. Subsequent analyses of direct gray-to-gray matter disconnections revealed that disconnections of additional left-hemispheric areas (e.g., between the superior temporal gyrus and parietal areas) were significantly associated with the observed fact retrieval deficit. Results imply that disconnections of parietal areas (i.e., the AG) with language-related areas (i.e., superior and middle temporal gyri) seem specifically detrimental to arithmetic fact retrieval. This suggests that arithmetic fact retrieval recruits a widespread left-hemispheric network and emphasizes the relevance of white matter connectivity for number processing.

Training of vertical versus horizontal reading in patients with hemianopia - a randomized and controlled study.

HYPOTHESIS: Patients with hemianopic field defects (HFD) might benefit from reading text in vertical orientation if they place the text in the seeing hemifield along the vertical midline. METHODS: We assigned 21 patients with HFD randomly to either vertical or horizontal reading training. They trained reading single lines of texts from a computer screen at home for 2 × 30 min/day, 5 days/week, for 4 weeks. The main outcome variable was reading speed (RS) during reading standardized paragraphs of printed text (IReST) aloud. RS was assessed before training (T1), directly after training (T2) and 4 weeks later (T3). Quality of life (QoL) was assessed by Impact of Visual Impairment (IVI) questionnaire. RESULTS: Vertical training improved RS in the vertical direction significantly. Only patients with right HFD benefited. Horizontal training improved RS in horizontal diection significantly, but much more in patients with left than in those with right HFD. Both effects remained stable at T3. RS during training at the computer improved highly significantly and correlated strongly with RS of printed text (Pearson r= > 0.9). QoL: Vertical training showed a statistically significant improvement in the complete IVI-score, patients with right HFD in the emotional IVI-score. CONCLUSIONS: The improvements of RS were specific for the training. The stable effect indicates that the patients can apply the newly learned strategies to everyday life. The side of the HFD plays an essential role: Left-HFD patients benefitted from horizontal training, right-HFD patients from vertical training. However, the vertical RS did not reach the level of horizontal RS. The study was registered in the German Clinical Trials register (DRKS-ID: DRKS00018843).

Assessing body image in anorexia nervosa using biometric self-avatars in virtual reality: Attitudinal components rather than visual body size estimation are distorted.

BACKGROUND: Body image disturbance (BID) is a core symptom of anorexia nervosa (AN), but as yet distinctive features of BID are unknown. The present study aimed at disentangling perceptual and attitudinal components of BID in AN. METHODS: We investigated n = 24 women with AN and n = 24 controls. Based on a three-dimensional (3D) body scan, we created realistic virtual 3D bodies (avatars) for each participant that were varied through a range of ±20% of the participants' weights. Avatars were presented in a virtual reality mirror scenario. Using different psychophysical tasks, participants identified and adjusted their actual and their desired body weight. To test for general perceptual biases in estimating body weight, a second experiment investigated perception of weight and shape matched avatars with another identity. RESULTS: Women with AN and controls underestimated their weight, with a trend that women with AN underestimated more. The average desired body of controls had normal weight while the average desired weight of women with AN corresponded to extreme AN (DSM-5). Correlation analyses revealed that desired body weight, but not accuracy of weight estimation, was associated with eating disorder symptoms. In the second experiment, both groups estimated accurately while the most attractive body was similar to Experiment 1. CONCLUSIONS: Our results contradict the widespread assumption that patients with AN overestimate their body weight due to visual distortions. Rather, they illustrate that BID might be driven by distorted attitudes with regard to the desired body. Clinical interventions should aim at helping patients with AN to change their desired weight.

Impaired implicit learning and feedback processing after stroke.

The ability to learn is assumed to support successful recovery and rehabilitation therapy after stroke. Hence, learning impairments may reduce the recovery potential. Here, the hypothesis is tested that stroke survivors have deficits in feedback-driven implicit learning. Stroke survivors (n=30) and healthy age-matched control subjects (n=21) learned a probabilistic classification task with brain activation measured using functional magnetic resonance imaging in a subset of these individuals (17 stroke and 10 controls). Stroke subjects learned slower than controls to classify cues. After being rewarded with a smiley face, they were less likely to give the same response when the cue was repeated. Stroke subjects showed reduced brain activation in putamen, pallidum, thalamus, frontal and prefrontal cortices and cerebellum when compared with controls. Lesion analysis identified those stroke survivors as learning-impaired who had lesions in frontal areas, putamen, thalamus, caudate and insula. Lesion laterality had no effect on learning efficacy or brain activation. These findings suggest that stroke survivors have deficits in reinforcement learning that may be related to dysfunctional processing of feedback-based decision-making, reward signals and working memory.

Parietal blood oxygenation level-dependent response evoked by covert visual search reflects set-size effect in monkeys.

Distinguishing a target from distractors during visual search is crucial for goal-directed behaviour. The more distractors that are presented with the target, the larger is the subject's error rate. This observation defines the set-size effect in visual search. Neurons in areas related to attention and eye movements, like the lateral intraparietal area (LIP) and frontal eye field (FEF), diminish their firing rates when the number of distractors increases, in line with the behavioural set-size effect. Furthermore, human imaging studies that have tried to delineate cortical areas modulating their blood oxygenation level-dependent (BOLD) response with set size have yielded contradictory results. In order to test whether BOLD imaging of the rhesus monkey cortex yields results consistent with the electrophysiological findings and, moreover, to clarify if additional other cortical regions beyond the two hitherto implicated are involved in this process, we studied monkeys while performing a covert visual search task. When varying the number of distractors in the search task, we observed a monotonic increase in error rates when search time was kept constant as was expected if monkeys resorted to a serial search strategy. Visual search consistently evoked robust BOLD activity in the monkey FEF and a region in the intraparietal sulcus in its lateral and middle part, probably involving area LIP. Whereas the BOLD response in the FEF did not depend on set size, the LIP signal increased in parallel with set size. These results demonstrate the virtue of BOLD imaging in monkeys when trying to delineate cortical areas underlying a cognitive process like visual search. However, they also demonstrate the caution needed when inferring neural activity from BOLD activity.

The dependencies of fronto-parietal BOLD responses evoked by covert visual search suggest eye-centred coding.

Visual scenes explored covertly are initially represented in a retinal frame of reference (FOR). On the other hand, 'later' stages of the cortical network allocating spatial attention most probably use non-retinal or non-eye-centred representations as they may ease the integration of different sensory modalities for the formation of supramodal representations of space. We tested if the cortical areas involved in shifting covert attention are based on eye-centred or non-eye-centred coding by using functional magnetic resonance imaging. Subjects were scanned while detecting a target item (a regularly oriented 'L') amidst a set of distractors (rotated 'L's). The array was centred either 5° right or left of the fixation point, independent of eye-gaze orientation, the latter varied in three steps: straight relative to the head, 10° left or 10° right. A quantitative comparison of the blood-oxygen-level-dependent (BOLD) responses for the three eye-gaze orientations revealed stronger BOLD responses in the right intraparietal sulcus (IPS) and the right frontal eye field (FEF) for search in the contralateral (i.e. left) eye-centred space, independent of whether the array was located in the right or left head-centred hemispace. The left IPS showed the reverse pattern, i.e. an activation by search in the right eye-centred hemispace. In other words, the IPS and the right FEF, members of the cortical network underlying covert search, operate in an eye-centred FOR.

Anatomical correlate of positive spontaneous visual phenomena: a voxelwise lesion study.

OBJECTIVES: Visual phenomena such as phosphenes, photopsias, or complex visual hallucinations occur in patients with lesions affecting the occipital, parietal, or temporal lobe. Whether these phenomena are provoked by lesions in specific anatomical regions is still uncertain. To determine which brain regions might be involved in such visual phenomena, we used new brain imaging and lesion analysis tools that allow a direct comparison with control patients. METHODS: Visual phenomena were investigated in a total of 23 patients with acute infarctions along the visual pathways (6 patients with left-sided and 17 patients with right-sided lesions). RESULTS: Ten of these 23 patients (43%) reported positive spontaneous visual phenomena (PSVP). Nine of the 10 patients (90%) with PSVP reported phosphenes; only 3 of the 10 (30%) reported photopsias. Statistical voxelwise lesion-behavior mapping revealed that the areas specifically related to PSVP are V1, V2, and the optic radiation. CONCLUSIONS: Disinhibition of earlier visual areas after lesions of the visual cortex and its afferent fibers seems to be the crucial mechanism in the genesis of visual phenomena in acute stroke patients.

The pupillary light reflex pathway: cytoarchitectonic probabilistic maps in hemianopic patients.

OBJECTIVE: The anatomy of the human pupillary light reflex (PLR) pathway is a matter of debate. The aim of this study was twofold: namely, to investigate the association of a relative afferent pupillary defect (RAPD) in acquired suprageniculate lesions with the location and extent of the cerebral lesions. Further, we suggest a new strategy of lesion analysis by combining established techniques with the stereotaxic probabilistic cytoarchitectonic atlas developed by the Jülich group. METHODS: Twenty-three patients with homonymous visual field defects participated in this study. The RAPD was quantified clinically by two independent examiners with graded neutral density filters (swinging flashlight test). Using MRI in each individual, cerebral regions commonly affected in patients with a RAPD but spared in patients without a RAPD were determined and subsequently assessed by using cytoarchitectonic probabilistic maps. RESULTS: A RAPD was present in 10/23 patients. Comparison of patients showing a RAPD vs those not showing a RAPD revealed that a region including the course of the optic radiation at its early beginning in the temporal white matter is commonly associated with a RAPD. CONCLUSIONS: It was demonstrated that the pupillary light reflex (PLR) depends on the input of suprageniculate neurons, thus supporting the involvement of a cortical pathway also. The site of integration of cortical signals in relation to the PLR into the pupillomotor pathway may be located suprageniculately in the vicinity of the lateral geniculate nucleus. Moreover, the suggested combination of established lesion analysis techniques with the probabilistic cytoarchitectonic atlas turned out to be a very helpful amelioration of stroke data analyses.

Abnormally speeded saccades to ipsilesional targets in patients with spatial neglect.

We mapped the distribution of saccadic reaction times (SRTs) in the visual field of patients with spatial neglect in order to characterise the topography of the bias in spatial orientation peculiar to this disorder. LED-generated stimuli were lit randomly in one of four positions (+/-5 degrees , +/-10 degrees , +/-20 degrees , +/-30 degrees ) along the horizontal meridian in blocks of either ipsilesional or contralesional presentations. Patients were asked to move the gaze as quickly as possible from central fixation to target upon its appearance. Unlike control subjects, patients with neglect showed an asymmetric distribution of visuo-motor performance in the two hemifields with an increasing impairment in target detection and saccadic reaction at increasing eccentricities in the contralesional field. In contrast, in the ipsilesional field they showed abnormally speeded SRTs at 5 degrees and 10 degrees , outperforming even healthy subjects. Latency of saccades increased again at more peripheral ipsilesional locations (20 degrees and 30 degrees ) where there was also a tendency for a higher omission rate as compared to control groups. These results indicate that in neglect patients the spatial orientation bias, as witnessed by saccadic performance, specifically affects an off-centred sector of the ipsilesional space, and this is in keeping with evidence from a previous study using a manual RT paradigm. The generality of this phenomenon across different types of motor response suggests that it depends upon abnormal mechanisms of spatial coding interfering with perceptual processing and orienting behaviour.

A general deficit of the 'automatic pilot' with posterior parietal cortex lesions?

Lesions of the parieto-occipital junction (POJ) in humans cause gross deviations of reaching movements and impaired grip formation if the targets are located in the subjects' peripheral visual field. Movements to central targets are typically less impaired. This disorder has been termed "optic ataxia". It has been suggested that a general deficit of online corrections under central as well as peripheral viewing conditions might be sufficient to explain this discrepancy. According to this hypothesis, patients with optic ataxia should demonstrate an impaired online correction of grip aperture under central viewing conditions if the target object changes its size during the grasping movement. We investigated this prediction in a patient with optic ataxia (I.G.) in a virtual visuo-haptic grasping task. We imposed an isolated need for online corrections of the hand aperture independently of positional changes of the target object. While we found some general inaccuracies of her grasping movements, the patient did not show a specific impairment of online adjustment of grip aperture. On the contrary, I.G. smoothly adjusted her grip aperture comparable to healthy subjects. A general deficit of fast movement correction affecting targets in peripheral as well as central visual fields thus does not appear to account for the overt visuomotor deficits in optic ataxia. Rather, it seems more likely that an anatomical dissociation between visuomotor pathways related to actions in the central and in the peripheral visual field underlies the dissociation of visuomotor performance depending on the retinotopic target position in optic ataxia.

Deviation of eyes and head in acute cerebral stroke.

BACKGROUND: It is a well-known phenomenon that some patients with acute left or right hemisphere stroke show a deviation of the eyes (Prévost's sign) and head to one side. Here we investigated whether both right- and left-sided brain lesions may cause this deviation. Moreover, we studied the relationship between this phenomenon and spatial neglect. In contrast to previous studies, we determined not only the discrete presence or absence of eye deviation with the naked eye through clinical inspection, but actually measured the extent of horizontal eye-in-head and head-on-trunk deviation. In further contrast, measurements were performed early after stroke onset (1.5 days on average). METHODS: Eye-in-head and head-on-trunk positions were measured at the bedside in 33 patients with acute unilateral left or right cerebral stroke consecutively admitted to our stroke unit. RESULTS: Each single patient with spatial neglect and right hemisphere lesion showed a marked deviation of the eyes and the head to the ipsilesional, right side. The average spontaneous gaze position in this group was 46 degrees right, while it was close to the saggital body midline (0 degrees ) in the groups with acute left- or right-sided stroke but no spatial neglect as well as in healthy subjects. CONCLUSION: A marked horizontal eye and head deviation observed approximately 1.5 days post-stroke is not a symptom associated with acute cerebral lesions per se, nor is a general symptom of right hemisphere lesions, but rather is specific for stroke patients with spatial neglect. The evaluation of the patient's horizontal eye and head position thus could serve as a brief and easy way helping to diagnose spatial neglect, in addition to the traditional paper-and-pencil tests.

Surviving glioblastoma for more than 5 years: the patient's perspective.

The authors performed a comprehensive analysis of the functional outcome of 10 patients who had survived 5 years from a diagnosis of glioblastoma. Neurologic deficits were mild in most patients, but neuropsychological testing demonstrated cognitive deficits in all patients. Depression and anxiety were common. Although most patients thought that their social functioning and work ability were impaired, little reduction in overall quality of life was perceived.

Children and adolescents with chronic cerebellar lesions show no clinically relevant signs of aphasia or neglect.

We studied language and visuospatial functions of 12 children and adolescents who had undergone surgery for cerebellar astrocytoma without subsequent radiation or chemotherapy and compared them with 27 age-, gender-, and education-matched healthy control subjects. To study possible lateralization of the functions of the left and right cerebellar hemispheres, subjects performed several language tasks including a verb-generation task as well as standard neglect and extinction tests. Three-dimensional-MR images confirmed that lesions affected cerebellar hemispheres in all children but one who had a pure vermal lesion. The right cerebellar hemisphere was affected in six, the left hemisphere in four children, and both hemispheres in one child. There were no signs of aphasia in the children or adolescents with cerebellar lesions. Language abilities did not differ between cerebellar patients and control subjects except for small increases in reaction times in verb generation in patients with left-sided lesions. Visuospatial functions were also intact in cerebellar subjects except for minor group differences in neglect tasks. In sum, chronic focal cerebellar lesions acquired in childhood or youth do not result in persistent language disorders or clinically significant signs of spatial neglect or extinction.

Incidence and diagnosis of anosognosia for hemiparesis revisited.

BACKGROUND: In previous studies, the incidence of anosognosia for hemiparesis has varied between 17% and 58% in samples of brain damaged patients with hemiparesis. OBJECTIVE: To determine whether this wide variation might be explained by the different criteria used for diagnosing anosognosia. METHODS: 128 acute stroke patients with hemiparesis or hemiplegia were tested for anosognosia for hemiparesis using the anosognosia scale of Bisiach et al. RESULTS: 94% of the patients who were rated as having "mild anosognosia"-that is, they did not acknowledge their hemiparesis spontaneously following a general question about their complaints-suffered from, and mentioned, other neurological deficits such as dysarthria, ptosis, or headache. However, they immediately acknowledged their paresis when they were asked about the strength of their limbs. Their other deficits clearly had a greater impact. These patients had significantly milder paresis than those who denied their disorder even when asked directly about their limbs. CONCLUSIONS: Patients who do not mention their paresis spontaneously but do so when questioned about it directly should not be diagnosed having "anosognosia." If this more conservative cut off criterion is applied to the data of the present as well as previous studies, a frequency of between 10% and 18% for anosognosia for hemiparesis is obtained in unselected samples of acute hemiparetic stroke patients. The incidence thus seems smaller than previously assumed.

Neck muscle vibration induces lasting recovery in spatial neglect.

OBJECTIVES: To evaluate whether neck muscle vibration is an effective technique for neglect rehabilitation, with lasting beneficial effects. METHODS: The effects of differential treatment of visual exploration training alone or in combination with neck muscle vibration were evaluated in a crossover study of two matched groups of 10 patients suffering from left sided neglect. Each group received a sequence of 15 consecutive sessions of exploration training and combined treatment. The effects of treatment were assessed with respect to different aspects of the neglect disorder such as impaired perception of the egocentric midline, exploration deficits in visual and tactile modes, and visual size distortion. The transfer of treatment effects to activities of daily living was examined by a reading test and a questionnaire of neglect related everyday problems. All variables were measured six times: three baseline measurements, two post-treatment measurements, and one follow up after two months. RESULTS: The results showed superior effects of combination treatment. A specific and lasting reduction in the symptoms of neglect was achieved in the visual mode, which transferred to the tactile mode with a concomitant improvement in activities of daily living. The improvement was evident two months after the completion of treatment. In contrast, isolated exploration training resulted in only minor therapeutic benefits in visual exploration without any significant transfer effects to other tasks. CONCLUSIONS: Neck muscle vibration is a decisive factor in the rehabilitation of spatial neglect and induces lasting recovery when given as a supplement to conventional exploration training.

Prognosis of contraversive pushing.

Stroke patients with 'pusher syndrome' actively push away from the non-hemiparetic side leading to a loss of postural balance and falling towards the paralysed side. The behaviour is due to an altered perception of the body's orientation in relation to gravity. Here, we studied the prognosis of the disorder. Twelve pusher patients first investigated immediately after the stroke were re-examined 6 months later. Pusher symptoms had nearly completely recovered. The aim for physiotherapy of patients with contraversive pushing thus is to shorten the period of necessary treatment and enable earlier discharge from residential care.