Drawing from childhood experience: constructional apraxia and the production of oblique lines

We report the performance of two patients (ECR and RA) with constructional apraxia on a drawing task previously used to test the development of planning abilities in children. Patients and controls were required to produce both oblique and horizontal/vertical lines that formed a right angle. Planning demands were manipulated across conditions by providing additional spatial information to constrain the drawing. Both patients produced drawings that were less accurate than controls. In addition, ECR was particularly poor at producing oblique lines compared to both RA and controls, even under conditions with minimal planning demands. This pattern of performance is qualitatively similar to that of children under eight years (see Broderick and Laszlo, 1988). Taken together these results provide further evidence that constructional apraxia is not a unitary disorder (with differential performance between patients) and that those differences are not necessarily related to laterality of damage (as both patients had right-hemisphere lesions). We argue for a more quantitative approach to the study of drawing abilities in neuropsychological testing in order to facilitate a finer grained analysis of the disorder and of comparison between patients.     

Left on the right: allochiria in a case of left visuo-spatial neglect.

A patient with left visuo-spatial neglect after right fronto-parietal haemorrhage failed to cross out stimuli in left space on cancellation tests. Her bisections of horizontal lines were displaced significantly to the right of true centre. On drawing and copying tasks, she sometimes omitted features on the left (neglect) and sometimes transposed them to right space (allochiria). This co-occurrence of neglect and allochiria has been observed previously but has provoked little theoretical comment. We draw attention to aspects of the combination that seem critical to the interpretation of visuo-spatial neglect.     

A progressive breakdown of the body in space

A 74 year-old woman (MD), free of previous neurological history, presented with difficulty in handling cutlery, clothes, writing with what was initially described as an atypical apraxia in acts related to space. Initial neurological evaluation revealed mixed, asymmetric pyramidal, and extrapyramidal semiology. Νeuropsychological testing revealed dressing and constructional deficits, ideomotor apraxia and signs of executive dysfunction in absence of memory, language, and visual perception pathology. The final diagnosis was that of a corticobasal degeneration, where the rare occurrence of a progressively emerging syndrome of self-management loss within peripersonal space is observed.     

EFNS guidelines on cognitive rehabilitation: report of an EFNS task force

Disorders of language, spatial perception, attention, memory, calculation and praxis are a frequent consequence of acquired brain damage [in particular, stroke and traumatic brain injury (TBI)] and a major determinant of disability. The rehabilitation of aphasia and, more recently, of other cognitive disorders is an important area of neurological rehabilitation. We report here a review of the available evidence about effectiveness of cognitive rehabilitation. Given the limited number and generally low quality of randomized clinical trials (RCTs) in this area of therapeutic intervention, the Task Force considered, besides the available Cochrane reviews, evidence of lower classes which was critically analysed until a consensus was reached. In particular, we considered evidence from small group or single cases studies including an appropriate statistical evaluation of effect sizes. The general conclusion is that there is evidence to award a grade A, B or C recommendation to some forms of cognitive rehabilitation in patients with neuropsychological deficits in the post-acute stage after a focal brain lesion (stroke, TBI). These include aphasia therapy, rehabilitation of unilateral spatial neglect (ULN), attentional training in the post-acute stage after TBI, the use of electronic memory aids in memory disorders, and the treatment of apraxia with compensatory strategies. There is clearly a need for adequately designed studies in this area, which should take into account specific problems such as patient heterogeneity and treatment standardization.     

Unilateral spatial neglect due to hemorrhage in the thalamic region

In a series of 33 cases of thalamic hemorrhage, unilateral spatial neglect (USN) was found in 11 patients all of whom had right-sided lesions. An analysis of results suggests that the posteromedial portion of the thalamus plays an important role in the pathogenesis of USN and that extensive lesions beyond the thalamus involving nearby structures may be necessary to cause persistent USN.     

A study of right unilateral spatial neglect in left hemispheric lesions: the difference between right-handed and non-right-handed post-stroke patients

We report 20 cases of right unilateral spatial neglect caused by lesions in the left cerebral hemisphere. Differences in neuropsychological symptoms and lesions sites are discussed in connection with handedness. Of the right-handed patients, 6 had severe aphasia, 4 had Gerstmann's syndrome, and 1 had pure agraphia, but unilateral spatial neglect in these cases disappeared after a number of months. Six of the non-right-handed patients had moderate-to-severe aphasia, while the other 3 cases had no aphasia at all. Eight of the 9 cases in this group continued to have right unilateral spatial neglect for more than 6 months. Lesion site as determined by CT differed as to hemisphere, but all fell into the common area previously mentioned in connection with such disorders: i.e., the temporal, parietal and occipital lobes.     

Influence of response modality on awareness of contralesional tactile stimuli in right brain damaged patients

Thirty right brain-damaged (RBD) patients with left tactile extinction (19 of whom also showed neglect) were given a sequence of 240 tactile stimuli – 80 right, 80 left, 80 bilateral – across 4 different response conditions: (a) verbal report of stimulated side/s, (b) motor report of stimulated side/s, (c) verbal report of unstimulated side/s, (d) motor report of unstimulated side/s. Earlier experiments based on similar tasks but involving RBD patients with visual extinction and/or neglect have shown that visual awareness of contralesional stimuli can be influenced by manipulation of response conditions.

Since neglect and extinction can be double-dissociated both anatomically and behaviourally, the question arises of whether the underlying neuronal mechanisms are different. To answer this question the present work investigated the role of perceptual and premotor factors in generating tactile extinction in response to Double Simultaneous Stimulation (DSS). The hypothesis was that a directional response bias would result in an overall higher frequency of errors for verbal or motor responses indicating the ipsilesional side (right); a perceptual bias would instead result in errors distributed with similar frequency on the ipsilesional and the contralesional (left) side.

Results showed that, in RBD patients, contralesional extinction was not influenced by response conditions (verbal/motor; report of stimulated/unstimulated side) and presence/absence of neglect. This suggests that: (1) among RBD patients, directional response biases are unlikely to play a role in extinction of tactile stimuli on DSS; (2) the mechanisms underlying extinction are, at least to some extent, different from those underlying unilateral neglect.     

Eyelid closing and opening disorders in patients with unilateral brain lesions: A case report with video neuroimage and a systematic review of the literature

Eyelid closing or opening disorders have been only sporadically described in patients with focal brain lesions over the last decades. Furthermore, the restricted number of reports and the lack of uniform clinical assessment of affected individuals did not allow to define more in depth the clinical features and the underlying neural correlates of these uncommon clinical disorders. Here we report an 89-years old woman with a right hemispheric lesion who showed a contralesional defect of eyelid closure. We also include a video neuroimage of this case and a review of eyelid closing and opening disorders in patients with focal unilateral lesions. In this review we found a correlation between right hemisphere and eyelid motor control, particularly for apraxia of eyelid closure affecting only the contralesional eye. The right parietal lobe was most frequently affected in this unilateral form of eyelid closing disorders, whereas putamen and other subcortical structures were more involved in eyelid opening than in eyelid closing disorders. The relations between unilateral eyelid closing disorders and other forms of motor-intentional defects are shortly discussed.     

Geographic information has to be spatialized to be neglected: a representational neglect case

A patient with unilateral neglect had to evoke mentally the map of France in two different conditions. In the first condition, he was asked to build an iconic representation of the map of France and to list all the towns that he could 'see' on this mental image within two minutes. In the second condition, he had to remember and name as many French towns as possible within two minutes, without being instructed to form a mental image. Left representational neglect was observed in the first condition only, i.e., when an iconic representation was required. These findings, which were replicated four months later, suggest a dual mode of coding, retrieval, or both, of geographic information and show that, although topographic, geographic data has to be spatialized to be neglected.     

Acceleration perception and spatial distortion in a left unilateral neglect patient

To explain relative leftward overextension in a line extension task by left unilateral neglect subjects, Bisiach et al. (1998) suggested that the representation of space is distorted--i.e., dilated towards the left side. If perception of the velocity of a moving stimulus is due to a calculation of the distance covered per unit time in representational space, then a stimulus with uniform linear motion should be perceived as decelerating when moving leftwards in the visual field of a subject with left unilateral neglect. We investigated the perception of acceleration in a patient with left unilateral neglect and spatial distortion (revealed as relative left overextension in a line extension task) using a task in which the stimuli were right and left moving targets with variable acceleration. The patient's ability to perceive acceleration was much lower (higher acceleration threshold) for leftward movements than rightward movements. Fourteen months later unilateral neglect had improved, and the relative left overextension and decreasing acceleration threshold for leftward movements were reduced. By contrast, alterations in the perception of acceleration for leftward movements were not found in a patient with left unilateral neglect and left underextension and in a patient with right brain damage and left hemianopia. These findings in one patient with left spatial unilateral neglect and a relative left overextension in a line extension task are consistent with the hypothesis that representational space is distorted, with a disproportionate leftward expansion, that affects perception of movement.     

Multiperturbation analysis of distributed neural networks: The case of spatial neglect

This study assesses the feasibility of using a multiperturbation analysis (MPA) approach for lesion‐symptom mapping. We analyze the relative contribution of damage in different brain regions to the expression of spatial neglect, as revealed in line‐bisection performance. The data set comprised of normalized lesion information and bisection test results from 23 first‐event right‐hemisphere stroke patients. Obtaining quantitative measures of task relevance for different regions of interest (ROIs), the following ROIs were found to be the most contributing: the supramarginal and angular gyri of the inferior parietal lobule, the superior parietal lobule, the anterior part of the temporo‐parietal junction connecting the superior temporal and supramarginal gyri, and the thalamus. MPA is likely to play an important role in elucidating the anatomical substrate of complex functions. Hum Brain Mapp, 2009. © 2009 Wiley‐Liss, Inc.     

Disorders of visual attention and the posterior parietal cortex

Traditionally, both the monkey and human posterior parietal cortex (PPC) have been considered to have a privileged role in spatial perception or action. Lesions to this region of the human brain, particularly of the right hemisphere, undoubtedly lead to spatially lateralised deficits such as visual extinction or neglect. However, although studies in monkeys have revealed much about the spatial functions of the parietal lobe, the monkey PPC may not be a good model system with which to understand fully the disorders of attention that follow damage to the human parietal cortex. Several lines of evidence, from functional imaging as well as investigations of patients with parietal damage, demonstrate that parts of the human inferior parietal lobe (IPL) have non-spatial functions. Here, we argue that it is important to distinguish spatially lateralised from spatial deficits. Both spatial and non-spatial impairments might, in principle, contribute to a spatially lateralised behavioural syndrome such as neglect. In this review, we discuss the evidence for such a proposal and suggest that a better understanding of human parietal syndromes may emerge from considering both the spatial and non-spatial functions of this region.     

EFNS Guidelines on cognitive rehabilitation: report of an EFNS Task Force

In 1999, a Task Force was set up under the auspices of the European Federation of Neurological Societies with the aim to evaluate the existing evidence for the clinical effectiveness of cognitive rehabilitation. This review led to the development of a set of guidelines to be used in the management of adult patients with cognitive disorders due to acquired focal neurological damage.     

Illustrating where spatial perception versus memory-based representation: spatial neglect in a distinguished artist; a case report

Spatial neglect is a disorder of attention, perception, and processing of stimuli in contralesional space. The heterogeneous behaviors involve diverse neuroanatomical mechanisms. Anecdotal evidence suggests that neural circuitry of active spatial perception may differ from that used to encode spatial memory. These differences can escape detection by conventional assessments, thereby leading to missed diagnoses. We present a case, in an artist who demonstrates selective impairment in a contralesional space during active Where spatial perception. His performance is better when asked to draw entirely from memory. This case highlights the variability in neglect, importance for comprehensive testing, and encourages further investigation.     

The eyes have it: Oculomotor exploration and line bisection in neglect

In this issue of Cortex, Ishiai et al. (2006) report the eye movements of patients with left neglect during the bisection of lines of different lengths. This is the latest in a series of papers from Ishiai's group, which form an important corpus of data on the oculomotor behaviour of neglect patients during line bisection and related tasks. In this article, I argue that these data should critically constrain theoretical models of bisection errors in neglect, but that these constraints have been applied rarely in practice. First, I briefly introduce bisection behaviour in neglect and describe some of the models proposed to account for its character. I then consider the implications for these models of Ishiai and colleagues' observations. Finally, I outline a novel view of the bisection task that is more compatible with their observations.     

Selective drawing disorders after right subcortical stroke: a neuropsychological premorbid and follow-up case study

We report the case of a patient affected by a subcortical lesion of the right non-dominant hemisphere, and demonstrate that he had selective constructional disorders by comparing his post-stroke performances with those assessed 18 months before the stroke. A detailed analysis was made of the visuospatial, perceptual, representational and executive competences involved in drawing tasks at one, two and six months post-stroke. Neuropsychological follow-up revealed the progressive recovery of all visuospatial abilities. This study provides some interpretative elements for constructional disorders and, in particular, for the closing-in phenomenon observed only during the subacute phase.

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Sommario Descriviamo un paziente affetto da una lesione sottocorticale dell'emisfero destro. Le prestazioni del paziente dopo l'ictus cerebrale, confrontate con quelle osservate prima dell'evento patologico, hanno dimostrato la presenza di selettivi disturbi costruttivi. Abbiamo effettuato un approfondito esame delle prestazioni costruttive, con prove visuospaziali che esplorano i livelli percettivo, rappresentazionale ed esecutivo, esaminando il paziente fino a sei mesi dopo l'ictus. Il follow-up neuropsicologico ha dimostrato un progressivo recupero di tutte le competenze visuospaziali. Questo studio fornisce dunque alcuni elementi interpretativi per i disordini costruttivi ed, in particolare, per il fenomeno del closing-in osservato nelle prime fasi dello studio longitudinale.

     

Left hand movements and right hemisphere activation in unilateral spatial neglect: a test of the interhemispheric imbalance hypothesis

The aim of the present study was to check one of the main assumptions of the interhemispheric imbalance hypothesis, namely, the prediction that the severity of neglect should be reduced by conditions activating the right hemisphere. To achieve this, a group of neglect patients was studied using a slightly modified version of the limb activation technique. The (verbal or visuo-spatial) nature of the stimuli to be processed by the patient and the (left or right) side of space where the left hand moved were considered as the critical variables to check the interhemispheric imbalance hypothesis.Three traditional and one new methods were used to measure changes induced in the severity of neglect by the material to be processed or by the side of space where the left hand moved. The traditional methods, all based on counting omissions, consisted of measuring: (a) the overall number of omissions; (b) the number of omissions made on the left half sheet; or (c) the difference between the omissions made on the left and right sides of the sheet. The new index, based on the notion of the 'attentional field' and defined as the spatial distribution of stimuli detected by the patient, was operationally measured by computing the distance between each stimulus crossed out by the patient and the right margin of the sheet. The study was conducted by rating the severity of neglect in 42 cancellation sheets which had used, respectively letters (N=21) and small geometric figures (N=21) as targets. The two sets of cancellation sheets were obtained from seven neglect patients during a limb activation task requiring the cancellation of a given target in three different conditions: (a) baseline; (b) active movements of the left hand in the left half space; (c) active movements of the left hand in the right half space.Results were at variance with the predictions based on Kinsbourne's model, since the verbal or visual spatial nature of the material to be processed did not influence the severity of unilateral spatial neglect (USN) and since left hand movements produced a significant reduction in the severity of neglect only when these movements were made on the left side of space.     

Visuospatial deficits due to impaired visual attention: investigation of two cases of slowly progressive visuospatial impairment

Two patients with slowly progressive visuospatial impairment demonstrated a peculiar type of visuoconstructive deficit. The most prominent manifestation appeared when handling kanji (logogram) characters and other figurative patterns. The patients showed pure agraphia for complex kanji but not for kana (syllabogram) or Arabic numerals. Their abilities to read and understand kanji characters and to orally describe the structure of a kanji character were preserved. They could not draw or copy figures or symbols except for single lines or simple symbols, although they could identify and name the targets easily. They also performed poorly in such visuoconstructive tasks as the block design subtest and matching to sample tests that require the ability to simultaneously attend to multiple saliencies. When asked to copy multiple kana characters scattered on a sheet of paper, they could correctly describe the location of a particular character in relation to the others, but actually wrote each character in grossly mislocated positions. These findings suggest that when the patients start particular tasks, which require detailed visual analysis, their range of visual attention becomes extremely narrow. This task-dependent narrowing and fixation of visual attention might explain some of the visuoconstructive symptoms described in patients with slowly progressive visuospatial impairment.     

A revised method for analysing neglect using the landmark task

In order to better disentangle 'perceptual' and 'response' biases in neglect patients, Bisiach and his co-workers developed a new version of the 'landmark task'. In their version, subjects are required to choose which is the longer (first condition) or the shorter (second condition) of the two portions of a pre-bisected horizontal line. Two indices were proposed, for the purpose of measuring perceptual and response bias respectively. The perceptual bias index (PB) is the constant error across conditions, while the response bias index (RB) is the degree of response consistency between conditions. Although valuable in a clinical context, these indices are not mathematically independent of one another. Furthermore, they do not exploit all of the information available in a given set of landmark data, since the responses made at the different landmark locations are all averaged together. To overcome these problems, we propose two new indices that can be derived from the revised landmark task. Our perceptual bias index is the Point of Subjective Equality (PSE)--the mean landmark location that appears to be halfway along the line. The response bias index, M, is the mean probability of making a response that opposes the patient's subjective midpoint. PSE and M are mathematically independent of each other and use most of the landmark information. The method and its theoretical foundation are summarized, and illustrative data obtained from brain damaged patients and control subjects are presented. Finally, computational procedures are provided for both PSE and M.     

Approaches to subjective midpoint of horizontal lines in unilateral spatial neglect

Patients with unilateral spatial neglect usually bisect longer lines with greater rightward errors, while they sometimes err leftward for very short lines (e.g., 25 mm). We analysed movements of eye fixation from the time before line presentation to elucidate whether patients with neglect approach the subjective midpoint differently for lines of various lengths. Four patients with left neglect bisected 200 mm, 100 mm, and 25 mm lines that appeared across the centre of a liquid crystal display (LCD) monitor. The fixation immediately before line presentation was located on average near the centre of the lines. Three of the patients approached the subjective midpoint point directly from the left side in more than 70% of the 200 mm and 100 mm trials. The subjective midpoint frequently deviated leftward on the "attended" segment between the leftmost point of fixation and the right endpoint, while it was displaced rightward on the total extent. The three patients initially explored the 25 mm lines searching for the left endpoint. They thereafter bisected the same lines with leftward errors approaching the subjective midpoint from the left side. The remaining patient searched beyond the right endpoint and in turn approached the subjective midpoint from the right side in about half of the trials and independently of line length. In the 200 mm and 100 mm trials, the subjective midpoint divided the attended right segment nearer to the right endpoint. On the attended right extent of a line, patients with neglect may place the subjective midpoint toward the side from which they approached that point. In the bisection of very short lines, approaches from the left endpoint may cause leftward errors of the subjective midpoint. For longer lines, however, approaches from the left side may result in rightward error of bisection for the total length, as the leftward extent from the fixation immediately before line presentation is hardly explored.