Visuospatial Deficits Research Articles

Biased visuospatial perception in complex regional pain syndrome

Complex regional pain syndrome (CRPS) is a chronic pain condition associating sensory, motor, trophic and autonomic symptoms in one limb. Cognitive difficulties have also been reported, affecting the patients’ ability to mentally represent, perceive and use their affected limb. However, the nature of these deficits is still a matter of debate. Recent studies suggest that cognitive deficits are limited to body-related information and body perception, while not extending to external space. Here we challenge that statement, by using temporal order judgment (TOJ) tasks with tactile (i.e. body) or visual (i.e. extra-body) stimuli in patients with upper-limb CRPS. TOJ tasks allow characterizing cognitive biases to the advantage of one of the two sides of space. While the tactile TOJ tasks did not show any significant results, significant cognitive biases were observed in the visual TOJ tasks, affecting mostly the perception of visual stimuli occurring in the immediate vicinity of the affected limb. Our results clearly demonstrate the presence of visuospatial deficits in CRPS, corroborating the cortical contribution to the CRPS pathophysiology, and supporting the utility of developing rehabilitation techniques modifying visuospatial abilities to treat chronic pain.

Reduced P300 amplitude during a visuospatial attention task in idiopathic rapid eye movement sleep behavior disorder

ObjectivesIdiopathic rapid eye movement sleep behavior disorder (IRBD) patients are prone to cognitive deficits, which include attention, executive, and visuospatial dysfunctions. Even patients with normal cognition may exhibit subclinical electrophysiological dysfunction. This study aimed to evaluate visuospatial attention processing in IRBD patients with normal cognition and to compare their findings with those of age- and sex-matched healthy controls. MethodsWe recorded event-related potentials (ERPs) and performance measures during a variant of the Posner task in 14 IRBD patients and 14 control subjects. Behavioral data and the mean P300 amplitude were compared between groups. ResultsNo group difference was found for reaction time or accuracy, but a significant group effect was observed for the P300 amplitude. IRBD patients had reduced P300 amplitude (μV) than controls in both valid (IRBD: 0.53 ± 1.05 vs Controls: 1.61 ± 0.95; p = 0.008) and invalid (IRBD: 0.74 ± 0.99 vs Controls: 1.73 ± 0.86; p = 0.009) conditions. The P300 amplitude was correlated with Montreal cognitive assessment (MOCA) scores (r = 0.424, p = 0.024). ConclusionReduced P300 amplitude during the Posner task provides electrophysiological evidence for subclinical visuospatial attention deficits in cognitively normal IRBD patients. The results of this study imply that cortical dysfunction is already present in patients with IRBD in their early disease stage.

Dissociation of spatial memory systems in Williams syndrome.

Williams syndrome (WS), a genetic deletion syndrome, is characterized by severe visuospatial deficits affecting performance on both tabletop spatial tasks and on tasks which assess orientation and navigation. Nevertheless, previous studies of WS spatial capacities have ignored the fact that two different spatial memory systems are believed to contribute parallel spatial representations supporting navigation. The place learning system depends on the hippocampal formation and creates flexible relational representations of the environment, also known as cognitive maps. The spatial response learning system depends on the striatum and creates fixed stimulus-response representations, also known as habits. Indeed, no study assessing WS spatial competence has used tasks which selectively target these two spatial memory systems. Here, we report that individuals with WS exhibit a dissociation in their spatial abilities subserved by these two memory systems. As compared to typically developing (TD) children in the same mental age range, place learning performance was impaired in individuals with WS. In contrast, their spatial response learning performance was facilitated. Our findings in individuals with WS and TD children suggest that place learning and response learning interact competitively to control the behavioral strategies normally used to support human spatial navigation. Our findings further suggest that the neural pathways supporting place learning may be affected by the genetic deletion that characterizes WS, whereas those supporting response learning may be relatively preserved. The dissociation observed between these two spatial memory systems provides a coherent theoretical framework to characterize the spatial abilities of individuals with WS, and may lead to the development of new learning strategies based on their facilitated response learning abilities.

Visuo-spatial cueing in children with differential reading and spelling profiles.

Dyslexia has been claimed to be causally related to deficits in visuo-spatial attention. In particular, inefficient shifting of visual attention during spatial cueing paradigms is assumed to be associated with problems in graphemic parsing during sublexical reading. The current study investigated visuo-spatial attention performance in an exogenous cueing paradigm in a large sample (N = 191) of third and fourth graders with different reading and spelling profiles (controls, isolated reading deficit, isolated spelling deficit, combined deficit in reading and spelling). Once individual variability in reaction times was taken into account by means of z-transformation, a cueing deficit (i.e. no significant difference between valid and invalid trials) was found for children with combined deficits in reading and spelling. However, poor readers without spelling problems showed a cueing effect comparable to controls, but exhibited a particularly strong right-over-left advantage (position effect). Isolated poor spellers showed a significant cueing effect, but no position effect. While we replicated earlier findings of a reduced cueing effect among poor nonword readers (indicating deficits in sublexical processing), we also found a reduced cueing effect among children with particularly poor orthographic spelling (indicating deficits in lexical processing). Thus, earlier claims of a specific association with nonword reading could not be confirmed. Controlling for ADHD-symptoms reported in a parental questionnaire did not impact on the statistical analysis, indicating that cueing deficits are not caused by more general attentional limitations. Between 31 and 48% of participants in the three reading and/or spelling deficit groups as well as 32% of the control group showed reduced spatial cueing. These findings indicate a significant, but moderate association between certain aspects of visuo-spatial attention and subcomponents of written language processing, the causal status of which is yet unclear.

VISUAL IMAGERY AND AUTOBIOGRAPHICAL MEMORY IMPAIRMENT IN POSTERIOR CORTICAL ATROPHY

Posterior cortical atrophy (PCA) is a syndrome characterized by progressive disruption of visual processing and neurodegeneration in the parieto-occipital cortex. The most common underlying cause is Alzheimer's pathology. Anterograde memory function and the medial temporal lobes (MTLs) are thought to be relatively preserved. Given that the typical pattern of atrophy in PCA overlaps with brain networks critical for the recollection of personal events, we hypothesised that patients would be impaired on a test of autobiographical memory. 14 PCA, 18 Alzheimer's disease (AD) patients and 28 healthy controls completed the Autobiographical Interview. Patients also underwent detailed neuropsychological testing and volumetric MRI. Autobiographical memory in PCA was characterised by a striking loss of episodic detail relative to controls. PCA patients were as impaired as AD patients for recollection across the lifespan, however, PCA patients showed a specific absence of spatiotemporal and perceptual features in the narratives they produced. These deficits in autobiographical memory occurred alongside visuospatial and global visual imagery deficits. Voxel-based morphometry confirmed prominent prominent atrophy of the parietal and occipital cortices, but sparing of the hippocampi bilaterally. Our findings present novel evidence for remote memory impairment in PCA. We propose that damage to posterior regions of the brain disrupts access to visual information integral to the autobiographical memory trace.

EYE MOVEMENT BEHAVIOR IN EARLY ALZHEIMER'S DISEASE: THE IMPACT OF TIME AND STIMULI SIMILARITY AS A MEASURE OF COGNITIVE EFFORT

Research has been showing that oculomotor measurements can accurately detect higher-order cognitive deficits, namely in memory and visuospatial processing deficits (Rizzo et al., 2004; Garbutt et al., 2008; Crutcher et al., 2009). Literature has still failed to analyze the impact of cognitive effort in the eye movement behavior as a tool to distinguish healthy subjects from those with cognitive decline due to Alzheimer's disease. 26 age and education matched participants (6 AD, 10 MCI, 10 NC) were submitted to a computational task composed by a familiarization phase and a test phase. During the familiarization phase, participants were instructed to look at two initial images. After that, there was a variable time delay of 5 or 90 seconds. During the test phase, other two images were presented, one of them was identical to previously seen, the other was a new one. Subjects were instructed to select the novel image which was either similar or non similar to the familiar stimulus. Eye-movement bahavior was analyzed based on four main parameters: number of visits (VC), duration of visits (VD) number of fixations (FC), fixation duration (FD). Parameters were analyzed regarding diagnostic, stimuli similarity and time between trials. Stimuli similarity revealed significant interference in the following parameters: VC, PrFC, PrVD, PrVC. Stimuli similarity also had impact on eye-movement pattern when associated with time delay between the familiarization phase and the test phase (PrFD, PrFC, PrVC). Both the proportion of time fixated on the novel stimulus (PrFD) and the proportion of the number of visits on the novel stimulus (PrVC) were affected by the participants’ diagnosis, when combined with stimuli similarity and time delay, respectively.

Behavioral and Cortical Effects during Attention Driven Brain-Computer Interface Operations in Spatial Neglect: A Feasibility Case Study.

During the last years, several studies have suggested that Brain-Computer Interface (BCI) can play a critical role in the field of motor rehabilitation. In this case report, we aim to investigate the feasibility of a covert visuospatial attention (CVSA) driven BCI in three patients with left spatial neglect (SN). We hypothesize that such a BCI is able to detect attention task-specific brain patterns in SN patients and can induce significant changes in their abnormal cortical activity (α-power modulation, feature recruitment, and connectivity). The three patients were asked to control online a CVSA BCI by focusing their attention at different spatial locations, including their neglected (left) space. As primary outcome, results show a significant improvement of the reaction time in the neglected space between calibration and online modalities (p < 0.01) for the two out of three patients that had the slowest initial behavioral response. Such an evolution of reaction time negatively correlates (p < 0.05) with an increment of the Individual α-Power computed in the pre-cue interval. Furthermore, all patients exhibited a significant reduction of the inter-hemispheric imbalance (p < 0.05) over time in the parieto-occipital regions. Finally, analysis on the inter-hemispheric functional connectivity suggests an increment across modalities for regions in the affected (right) hemisphere and decrement for those in the healthy. Although preliminary, this feasibility study suggests a possible role of BCI in the therapeutic treatment of lateralized, attention-based visuospatial deficits.

Neuropsychological Subgroups in Non-Demented Parkinson's Disease: A Latent Class Analysis.

Methods to detect early cognitive decline and account for heterogeneity of deficits in Parkinson's disease (PD) are needed. Quantitative methods such as latent class analysis (LCA) offer an objective approach to delineate discrete phenotypes of impairment. To identify discrete neurocognitive phenotypes in PD patients without dementia. LCA was applied to a battery of 8 neuropsychological measures to identify cognitive subtypes in a cohort of 199 non-demented PD patients. Two measures were analyzed from each of four domains: executive functioning, memory, visuospatial abilities, and language. Additional analyses compared groups on clinical characteristics and cognitive diagnosis. LCA identified 3 distinct groups of PD patients: an intact cognition group (54.8%), an amnestic group (32.2%), and a mixed impairment group with dysexecutive, visuospatial and lexical retrieval deficits (13.1%). The two impairment groups had significantly lower instrumental activities of daily living ratings and greater motor symptoms than the intact group. Of those diagnosed as cognitively normal according to MDS criteria, LCA classified 23.2% patients as amnestic and 9.9% as mixed cognitive impairment. Non-demented PD patients exhibit distinct neuropsychological profiles. One-third of patients with LCA-determined impairment were diagnosed as cognitively intact by expert consensus, indicating that classification using a statistical algorithm may improve detection of initial and subtle cognitive decline. This study also demonstrates that memory impairment is common in non-demented PD even when cognitive impairment is not clinically apparent. This study has implications for predicting eventual emergence of significant cognitive decline, and treatment trials for cognitive dysfunction in PD.

Atypical Local Interference Affects Global Processing in Children with Neurofibromatosis Type 1.

To examine hierarchical visuospatial processing in children with neurofibromatosis type 1 (NF1), a single gene disorder associated with visuospatial impairments, attention deficits, and executive dysfunction. We used a modified Navon paradigm consisting of a large "global" shape composed of smaller "local" shapes that were either congruent (same) or incongruent (different) to the global shape. Participants were instructed to name either the global or local shape within a block. Reaction times, interference ratios, and error rates of children with NF1 (n=30) and typically developing controls (n=24) were compared. Typically developing participants demonstrated the expected global processing bias evidenced by a vulnerability to global interference when naming local stimuli without a cost of congruence when naming global stimuli. NF1 participants, however, experienced significant interference from the unattended level when naming both local and global levels of the stimuli. Findings suggest that children with NF1 do not demonstrate the typical human bias of processing visual information from a global perspective. (JINS, 2017, 23, 446-450).

Binge-eating disorder may be distinguished by visuospatial memory deficits

ObjectiveBinge eating disorder (BED), characterized by recurrent episodes of loss of control overeating, is highly comorbid with overweight and obesity. Both loss of control eating and higher body mass index have been associated with poor memory. The current study sought to clarify the relationships between BED, weight and memory. Specifically, visual memory was examined, given evidence of impaired visuospatial abilities in overweight individuals and little research on visual memory in BED. MethodOverweight and normal-weight women with BED and matched healthy controls were administered the Rey Complex Figure Test. ResultsPlanned contrasts revealed that normal-weight healthy controls performed better than all other groups on the immediate and delayed recall portions of the task. Performance on the immediate recall portion was better among normal-weight individuals than overweight individuals, and performance on both the immediate and delayed recall portions was better among individuals without BED than those with BED. No differences between groups were seen on the copy or recognition trials. ConclusionsVisual memory appears to be impaired among overweight participants and both normal and overweight participants with BED. This finding was specific to retrieval. Replication of this finding in BED using different measures of memory is needed.

A Case of erotomanic delusion in dementia

IntroductionIn dementia, delusions are common with prevalence up to 75%. However, erotomanic delusions, or De Clerambault's syndrome, are a rarity in dementia. To date, only six case-reports have been described in vascular dementia, frontotemporal dementia, and Alzheimer's dementia.ObjectivesTo present a case of De Clerambault's syndrome in an older adult diagnosed with vascular dementia.AimsTo review available literature on De Clerambault's syndrome in dementia.MethodsA case report is presented and discussed followed by a literature review.ResultsWe report a 72-year-old female with a history of right posterior cerebral artery infarction. The patient developed a sudden onset erotomanic delusion after she met a male patient of her age during her stay in a dementia day care center. She was agitated, disorientated, presented with confabulation, and showed a dysphoric mood. On MMSE she scored 14/30, the clock-drawing test revealed visuospatial deficits. On MRI, the right occipital lobe showed an encephalomalacia. The patient was treated with sertraline 50 mg/day and olanzapine 5 mg/day. Her erotomanic delusions improved after 3 months of treatment.ConclusionDe Clerambault's syndrome is a rare and poorly understood disorder with generally a poor response to treatment. Some cases were successfully treated with atypical anti-psychotics. However, further research is needed to explore the course and treatment of this delusion.Disclosure of interestThe authors have not supplied their declaration of competing interest.

Resting-State Functional Connectivity Changes Associated with Visuospatial Cognitive Deficits in Patients with Mild Alzheimer Disease

Background/Aims: Alzheimer disease (AD) is a neurodegenerative disorder characterized by progressive disconnection of various brain networks leading to neuropsychological impairment. Pathology in the visual association areas has been documented in presymptomatic AD and therefore we aimed at examining the relationship between brain connectivity and visuospatial (VS) cognitive deficits in early AD. Methods: Tests for VS working memory, episodic memory and construction were used to classify patients with AD (n = 48) as having severe VS deficits (n = 12, female = 4) or mild deficits (n = 11, female = 4). Resting-state functional magnetic resonance imaging and structural images were acquired as per the standard protocols. Between-group differences in resting-state functional connectivity (rsFC) were examined by dual regression analysis correcting for age, gender, and total brain volume. Results: Patients with AD having severe VS deficits exhibited significantly reduced rsFC in bilateral lingual gyri of the visual network compared to patients with mild VS deficits. Conclusion: Reduced rsFC in the visual network in patients with more severe VS deficits may be a functional neuroimaging biomarker reflecting hypoconnectivity of the brain with progressive VS deficits during early AD.

Evidence of the impact of visuo-spatial processing on magnitude representation in 22q11.2 microdeletion syndrome

The influence of visuo-spatial skills on numerical magnitude processing is the subject of a long-standing debate. As most of the numerical and non-numerical magnitude abilities underpinning mathematical development are visual by nature, they are often assessed in the visual modality, thereby confusing visuo-spatial and numerical processing. In order to assess the influence of visuo-spatial processing on numerical magnitude representation, we examined magnitude processing in patients with 22q11.2 deletion syndrome (22q11DS), a genetic condition characterized by a cognitive profile with a relative weakness in visuo-spatial abilities but with preserved verbal abilities. Twenty-seven participants with 22q11DS were compared to two control groups (one matched on verbal intelligence and the other on visuo-spatial abilities) on several magnitude comparison tasks each with different visuo-spatial processing requirements. Our results showed that participants with 22q11DS present a consistent pattern of impairment in magnitude comparison tasks requiring the processing of visuo-spatial dimensions: comparison of lengths and collections. In contrast, their performance did not differ from the control groups in a visual task with no spatial processing requirement (i.e. numerical comparison of flashed dot sequences) or in auditory tasks (i.e., duration comparison and numerical comparison of sound sequences). Finally, a specific deficit of enumeration processes was observed in the subitizing range. Taken together, these results show that deficits in magnitude can occur as a consequence of a visuo-spatial deficit. This highlights the influence of the nature of the tasks selected to assess magnitude representation.

A case of posterior cortical atrophy with vertical neglect

ABSTRACTPosterior cortical atrophy (PCA) is a syndrome caused by a neurodegenerative disease that often presents with visuospatial deficits, and can be debilitating. PCA is often characterized by elements of Balint’s syndrome and dyslexia. The most common underlying pathology has been found to be Alzheimer’s disease. Signs of horizontal neglect are frequently associated with PCA, but the presence of vertical (or altitudinal) neglect has not yet been reported in a patient with PCA or other forms of neurodegenerative dementia. In this paper, we present a patient with PCA who on vertical line bisection and cancellation tests revealed upper altitudinal spatial neglect. Detection of this abnormality may have important implications for diagnosis, therapeutic interventions, and patient safety.

Spastic diplegia in preterm-born children: Executive function impairment and neuroanatomical correlates

BackgroundThe neuropsychological literature on preterm-born children with spastic diplegia due to periventricular leukomalacia is convergent in reporting deficits in non-verbal intelligence and in visuo-spatial abilities. Nevertheless, other cognitive functions have found to be impaired, but data are scant and not correlated with neuroimaging findings. AimsThis study analyzes the neuropsychological strengths and weaknesses in preterm-born children with spastic diplegia (pSD) and their relationships with neuroanatomical findings, investigated by a novel scale for MRI classification. Methods and proceduresNineteen children with pSD, mild to moderate upper limb impairment and Verbal IQ>80, and 38 normal controls were evaluated with a comprehensive neuropsychological battery (NEPSY-II), assessing Attention/Executive Functioning, Language, Memory, Sensorimotor, Social Perception and Visuospatial Processing domains. The MRIs were quantitatively scored for lesion severity. Outcomes and resultsThe results showed that, beyond core visuo-spatial and sensory-motor deficits, impairments in attention and executive functions were present in more than half of the sample, particularly in children with damage to the anterior corpus callosum. Conclusions and implicationsThe findings are discussed in terms of clinical and rehabilitative implications tailored for pSD subgroups diversified for neuropsychological and neuroanatomical characteristics.

Visual Dysfunction in Parkinson's Disease.

This chapter describes the visual problems likely to be encountered in Parkinson's disease (PD) and whether such signs are useful in differentiating the parkinsonian syndromes. Visual dysfunction in PD may involve visual acuity, contrast sensitivity, color discrimination, pupil reactivity, saccadic and pursuit eye movements, motion perception, visual fields, and visual processing speeds. In addition, disturbance of visuospatial orientation, facial recognition problems, rapid eye movement (REM) sleep behavior disorder, and chronic visual hallucinations may be present. Problems affecting pupil reactivity, stereopsis, pursuit eye movement, and visuomotor adaptation, when accompanied by REM sleep behavior disorder, could be early features of PD. Dementia associated with PD is associated with enhanced eye movement problems, visuospatial deficits, and visual hallucinations. Visual dysfunction may be a useful diagnostic feature in differentiating PD from other parkinsonian symptoms, visual hallucinations, visuospatial dysfunction, and variation in saccadic eye movement problems being particularly useful discriminating features.

Neglect Dyslexia in Relation to Unilateral Visuospatial Neglect: A Review

Unilateral visuospatial neglect and neglect dyslexia are neuropsychological syndromes in which patients exhibit consistently lateralised perceptual deficits. However, there is little agreement surrounding whether neglect dyslexia is best understood as a consequence of a domain-general visuospatial neglect impairment or as an independent, content-specific cognitive deficit. Previous case studies have revealed that neglect dyslexia is an exceptionally heterogeneous condition and have strongly suggested that not all neglect dyslexia patient error patterns can be fully explained as a consequence of domain-general visuospatial neglect impairment. Additionally, theoretical models which attempt to explain neglect dyslexia as a consequence of domain-general unilateral visuospatial neglect fail to account for neglect dyslexia errors which occur when reading vertically presented words, lack of neglect errors when reading number strings, and neglect dyslexia which co-occurs with oppositely lateralised domain-general visuospatial neglect. Cumulatively, these shortcomings reveal that neglect dyslexia cannot always be accurately characterised as a side-effect of domain-general visuospatial unilateral neglect deficits. These findings strongly imply that neglect dyslexia may be better understood as a content-specific impairment.

Increased Alpha-Rhythm Dynamic Range Promotes Recovery from Visuospatial Neglect: A Neurofeedback Study.

Despite recent attempts to use electroencephalogram (EEG) neurofeedback (NFB) as a tool for rehabilitation of motor stroke, its potential for improving neurological impairments of attention—such as visuospatial neglect—remains underexplored. It is also unclear to what extent changes in cortical oscillations contribute to the pathophysiology of neglect, or its recovery. Utilizing EEG-NFB, we sought to causally manipulate alpha oscillations in 5 right-hemisphere stroke patients in order to explore their role in visuospatial neglect. Patients trained to reduce alpha oscillations from their right posterior parietal cortex (rPPC) for 20 minutes daily, over 6 days. Patients demonstrated successful NFB learning between training sessions, denoted by improved regulation of alpha oscillations from rPPC. We observed a significant negative correlation between visuospatial search deficits (i.e., cancellation test) and reestablishment of spontaneous alpha-rhythm dynamic range (i.e., its amplitude variability). Our findings support the use of NFB as a tool for investigating neuroplastic recovery after stroke and suggest reinstatement of intact parietal alpha oscillations as a promising target for reversing attentional deficits. Specifically, we demonstrate for the first time the feasibility of EEG-NFB in neglect patients and provide evidence that targeting alpha amplitude variability might constitute a valuable marker for clinical symptoms and self-regulation.

Visuospatial memory in patients with obsessive-compulsive disorder

Background: Obsessive-compulsive disorder (OCD) is a clinically heterogeneous disorder. The previous studies have been conducted to elucidate visuospatial and nonverbal memory deficits in OCD patients. However, they did not reach equivocal results which need to be replicated. Objectives: The current study examines the visuospatial memory in male patients with OCD as compared to normal healthy controls. Materials and Methods: It is a cross-sectional hospital-based study, in which 15 OCD patients and 15 age-, sex-, and education-matched normal healthy controls were chosen by purposive sampling technique. All the participants underwent the Extended Complex Figure Test (ECFT) for the assessment of visuospatial memory. Results: Significant difference was found between OCD patients and normal healthy controls on various domains of ECFT. OCD patients performed poorly on copy condition (t = −4.46; P< 0.001), immediate recall (t = −5.20; P< 0.001), delayed recall (t = −5.18; P< 0.001), recognition task (P < 0.001), and matching task (P < 0.001) than the controls. Conclusion: Visuospatial memory was significantly impaired in OCD that included disturbed encoding and impaired visuospatial functioning. Hence, it is important to understand the significance of visuospatial memory in the pathophysiology for OCD diagnosis and therapeutic decision.

Re-assessing acalculia: Distinguishing spatial and purely arithmetical deficits in right-hemisphere damaged patients

Arithmetical deficits in right-hemisphere damaged patients have been traditionally considered secondary to visuo-spatial impairments, although the exact relationship between the two deficits has rarely been assessed. The present study implemented a voxelwise lesion analysis among 30 right-hemisphere damaged patients and a controlled, matched-sample, cross-sectional analysis with 35 cognitively normal controls regressing three composite cognitive measures on standardized numerical measures. The results showed that patients and controls significantly differ in Number comprehension, Transcoding, and Written operations, particularly subtractions and multiplications. The percentage of patients performing below the cutoffs ranged between 27% and 47% across these tasks. Spatial errors were associated with extensive lesions in fronto-temporo-parietal regions -which frequently lead to neglect- whereas pure arithmetical errors appeared related to more confined lesions in the right angular gyrus and its proximity. Stepwise regression models consistently revealed that spatial errors were primarily predicted by composite measures of visuo-spatial attention/neglect and representational abilities. Conversely, specific errors of arithmetic nature linked to representational abilities only. Crucially, the proportion of arithmetical errors (ranging from 65% to 100% across tasks) was higher than that of spatial ones. These findings thus suggest that unilateral right hemisphere lesions can directly affect core numerical/arithmetical processes, and that right-hemisphere acalculia is not only ascribable to visuo-spatial deficits as traditionally thought.