Unilateral Spatial Neglect

A complex link exists between vision and unilateral spatial neglect (USN). Firstly, USN is not a perceptual deficit, secondly, USN is not necessarily accompanied by a visual deficit and finally, USN can be observed in non-visual modalities as well as in mental spatial imagery. This apparent supramodality of USN stands in sharp contrast to the fact that neglect signs are often more severe and more durable in the visual than in other sensory modalities (Chokron et al., 2002). The influence of vision on spatial representation has rarely been studied. In the present study we assessed six right brain-damaged patients suffering from left USN on two tasks involving spatial representations: a clock-drawing task and a drawing from memory task in two experimental conditions, with and without visual control. We confirm that even in mental imagery, the absence of visual feedback may decrease and even suppress left neglect signs (Bartolomeo and Chokron, 2001b; 2002). Since vision is largely involved in the orientation of attention in space, suppressing visual control could reduce the magnetic attraction towards the right ipsilesional hemispace and in this way could allow a re-orientation of attention towards the left neglected hemispace. We discuss the theoretical and therapeutic implications of these findings.

Visual Neglect (VN) is a common neuropsychological deficit associated with a person having a stroke (approximately 1/3/ of cases). Visual neglect is characterised by an inability to notice things on the side contralateral to the stroke site, typically the left. Currently in the clinical setting, pen and paper-based techniques such as the Behavioural Inattention Test (BIT) and Star Cancellation are used to assess the presence of VN in patients but they are purely binary classifiers and lack sensitivity so may fail to pick up subtle neglect. Regarding rehabilitation, there have been a number of programs developed to try and ameliorate the symptoms of VN with limited/varying degrees of success. Using the Leap Motion Controller, the associated SDK and the Processing programming language, this project sets out to develop a novel measurement paradigm for the mapping the spatial distribution of visual neglect to give a more nuances assessment of severity. It also lays the groundwork for developing a novel rehabilitative intervention based on Visual Scanning and Limb Activation.

The acclaimed Italian directors Luchino Visconti and Federico Fellini had very different life trajectories that led them to become major figures in the history of cinema. Similarities, however, can be found in their debuts with the neorealist genre, their personalities, creative styles and politicocultural involvement, and ultimately in the neurological disease that struck them at the end of their careers. Both suffered a right-hemispheric stroke that left them hemiplegic on the left side. We review their life and career to put that event into perspective, and then discuss its aftermath for both artists in the light of our current knowledge of right-hemispheric functions. Visconti showed a tremendous resilience following the accident and managed to direct several films and plays as an infirm, whereas Fellini had to put an end to his career but still was able to display his talents to the neuropsychologists that treated him. A speculative account is given of the links between right-hemispheric symptomatology and the premorbid personality of these highly prolific patients.

This work tackles the problem of whether the dissociation between two performances in a single-case study should be computed as the difference between the raw or between the standardized (e.g. z) scores. A wrong choice can lead to serious inflation of the probability of finding false dissociations and missing true dissociations. Two common misconceptions are that (i) standardized scores are a universally valid choice, or (ii) raw scores can be subtracted when the two performances concern the same "task/test", otherwise standardized scores are better. These and other rules are shown to fail in specific cases and a solution is proposed in terms of in-depth analysis of the meaning of each score. The scores that should be subtracted are those that better reflect "deficit severities"the latent, unobservable degrees of damage to the cognitive systems that are being compared. Thus explicit theoretical modelling of the investigated cognitive function(s)-the "scenario"-is required. A flowchart is provided that guides such analysis, and shows how a given neuropsychological scenario leads to the selection of an appropriate statistical method for detecting dissociations, introducing the critical concept of "deficit equivalence criterion"-the definition of what exactly a non-dissociation should look like. One further, overlooked problem concerning standardized scores in general (as measures of effect size, of which neuropsychological dissociations are just one example) is that they cannot be meaningfully compared if they have different reliabilities. In conclusion, when studying dissociations, increases in false-positive and false-negative risks are likely to occur when no explicit neuropsychological theory is offered that justifies the definition of what are to be considered as equivalent deficit severities in both performances, and which would lead to appropriate selection of raw, standardized, or any other type of score. More generally, the choice of any measure in any research context needs explicit theoretical modelling, without which statistical risks cannot be controlled.

For many historians, sociologists, and anthropologists of medicine, “disease” and “illness” are not equivalent. Whereas “disease” denotes the physician’s ostensibly objective criteria, “illness” emphasizes the patient’s subjective experience. This dissertation examines that distinction precisely at a point where it breaks down, in the history of a diagnosis called “anosognosia,” also known as the denial of illness.
    In the 1890s, Austrian psychiatrist Gabriel Anton observed a number of patients who denied being blind, deaf, or paralyzed. “That is just how it is,” a patient demurred, “one sees better in youth.” The question to Anton was, were such patients truly unaware of their loss or did they sense it on some level, if only to deny it?
    The history of Anton’s syndrome, later named “anosognosia” by the French neurologist Joseph Babinski, spans more than a century and a half across two continents and through both world wars. I treat its history as a special type of lens to focus on some of the broader intellectual and professional differences between neurology and psychiatry. I argue that the clinical perception and portrayal of this apparent loss of the patient’s experience depended on historical patterns of thinking about the distinction between conscious and unconscious perception as well as categories of health and disease. To think about the denial of illness was to think about the very meaning of illness and awareness, and the difference, if any, between the mind and the brain.

Spatial neglect (SN) is commonly associated with poor functional outcome. Adaptation to a rightward optical deviation of vision has been shown to benefit to SN rehabilitation. The neurophysiological foundations and the optimal modalities of prism adaptation (PA) therapy however remain to be validated. This study is aimed at exploring the long-term sensory-motor, cognitive and functional effects produced by weekly PA sessions over a period of four weeks. A double-blind, monocentric randomized and controlled trial (RCT) was carried out. Twenty patients with left SN secondary to stroke were included, 10 in the “prism” group and 10 in the “control” group. The sensory-motor effects of PA were evaluated by measurement of manual and visual straight-ahead, and also by precision of pointing without visual feedback before and after each PA session. The functional independence measure (FIM) was evaluated before and at 1, 3 and 6 months after PA, while SN severity was assessed using the Behavioural Inattention Test (BIT) before and 6 months after PA. Before the intervention, only manual straight-ahead pointing constituted a reproducible sensory-motor measurement. During prism exposure, a questionnaire showed that not a single patient were aware of the direct effects of optical deviation on pointing movement performance. The sensory-motor after-effects produced by the PA produced a more rapid reduction of the rightward manual straight-ahead, which was secondarily followed by visual straight-ahead. These sensory-motor effects helped to clarify the action mechanisms of PA on SN. At the conclusion of the 6-month follow-up, the two groups showed similar improvement, indicating that a weekly PA session over 4 weeks was not sufficient to produce long-term functional benefit. This improvement was correlated with the evolution of visual straight-ahead, which can be proposed as a marker for patients outcome.

Although dissociations between anosognosia for motor deficit and neglect have been reported, several authors consider anosognosia and neglect as deeply related syndromes. Different techniques, such as optokinetic stimulation, adaptation to prismatic shift of the visual field to the right, or transcutaneous electrical nerve stimulation (TENS), have been shown to alleviate neglect at least temporarily. However, their effect on anosognosia has not been systematically investigated. The aim of this study is to investigate the effect of these techniques on anosognosia and to investigate whether the therapeutic effect, if any, matches that on neglect. A disparity in the outcome of treatment between anosognosia and neglect would support the dissociation between the two syndromes. We have named this procedure “Treatment Response Bias”.

Neglect dyslexia is a reading disorder often associated with right-sided brain lesions. In reading single words, errors are mostly substitutions or omissions of letters that occupy the left-sided positions. Typically, these errors have been thought to depend on a single mechanism. Conversely, we propose that they are due to different mechanisms. In particular, a visuo-spatial mechanism is responsible for omissions and a perceptual integration process for substitution errors. We measured the performance of six patients with both neglect and neglect dyslexia, analyzing their reading errors as a function of letter spacing. According to our conjecture, letter spacing should increase omissions by moving part of the string further in the unattended space, while it should reduce substitutions by restoring the integration processes. Furthermore, we predict that letter spacing should be more effective with pseudowords compared to words, in that in this latter case lexical effects are supposed to influence attentional and perceptual processes. Accordingly, we found that for pseudowords only the two types of errors are differently affected by this manipulation and only omissions correlate with the severity of the disorder in visuo-spatial tasks.

In the late 1970's Edoardo Bisiach and his coworkers provided definitive evidence that spatial unilateral neglect involves a disorder of the internal representation of extra-personal space. A few years later Bisiach and Berti (1987) revived the so far neglected contribution of an Austrian neurologist, Hermann Zingerle (1913). Ninety years ago Zingerle had described the symptom-complex of two right-brain-damaged patients, who showed left hemisomatoagnosia, unawareness of left hemiplegia, and left motor neglect. In addition to the detailed case reports, Zingerle had put forward a unitary interpretation of these deficits in terms of a disordered representation of one side of the body (dyschiria). A unitary representational account of these unilateral impairments was conspicuously absent in the contemporary neurological literature (Anton, Pick, Babinski), and attracted Bisiach's interest. An abridged translation of Zingerle's paper is provided. The clinical case reports and Zingerle's conclusions are discussed, with reference both to Bisiach's views, and to present knowledge of unilateral spatial neglect.

The critical lesion site responsible for the syndrome of unilatera lspatial neglect has been debated for more than a decade. Here we performed an activation likelihood estimation (ALE) to provide for the first time an objective quantitative index of the consistency of lesion sites across anatomical group studies of spatial neglect. The analysis revealed several distinct regions in which damage hasc onsistently been associated with spatial neglect symptoms. Lesioned clusters were located in several cortical and subcortical regions of the right hemisphere, including the middle and superior temporal gyrus, inferior parietal lobule, intraparietal sulcus, precuneus, middle occipital gyrus, caudate nucleus, and posterior insula, as well as in the white matter pathway corresponding to the posterior part of the superior longitudinal fasciculus. Further analyses suggested that separate lesion sites are associated with impairments in different behavioral tests, such as line bisection and target cancellation. Similarly, specific subcomponents of the heterogeneous neglects yndrome, such as extinction and allocentric and personal neglect, are associated with distinct lesion sites. Future progress in delineating the neuropathological correlates of spatial neglect will depend upon the development of more refined measures of perceptual and cognitive functions than those currently available in the clinical setting.

Recent evidence revealed the importance of inter-hemispheric communication for the compensation of functional deficits after brain damage. This review summarises the biological consequences observed using histology as well as the longitudinal findings measured with magnetic resonance imaging methods in brain damaged animals and patients. In particular, we discuss the impact of post-stroke brain hyperactivity on functional recovery in relation to time. The reviewed evidence also suggests that the proportion of the preserved functional network both in the lesioned and in the intact hemispheres, rather than the simple lesion location, determines the extent of functional recovery. Hence, future research exploring longitudinal changes in patients with brain damage may unveil potential biomarkers underlying functional recovery.

This article was originally published in the Encyclopedia of Human Behavior published by Elsevier, and the attached copy is provided by Elsevier for the author's benefit and for the benefit of the author's institution, for non-commercial research and educational use including without limitation use in instruction at your institution, sending it to specific colleagues who you know, and providing a copy to your institution's administrator. All other uses, reproduction and distribution, including without limitation commercial reprints, selling or licensing copies or access, or posting on open internet sites, your personal or institution's website or repository, are prohibited. For exceptions, permission may be sought for such use through Elsevier's permissions site at: http://www.elsevier.com/locate/permissionusematerial Berti A. and Neppi-Modona M. (2012) Agnosia (including Prosopagnosia and Anosognosia). In: V.S. Ramachandran (ed.) The Encyclopedia of Human Behavior, vol. 1, pp. 60-67. Academic Press.

This work tackles the problem of whether the dissociation between two performances in a single-case study should be computed as the difference between the raw or between the standardized (e.g. z) scores. A wrong choice can lead to serious inflation of the probability of finding false dissociations and missing true dissociations. Two common misconceptions are that (i) standardized scores are a universally valid choice, or (ii) raw scores can be subtracted when the two performances concern the same “task/test”, otherwise standardized scores are better.
These and other rules are shown to fail in specific cases and a solution is proposed in terms of in-depth analysis of the meaning of each score. The scores that should be subtracted are those that better reflect “deficit severities” – the latent, unobservable degrees of damage to the cognitive systems that are being compared. Thus explicit theoretical modelling of the investigated cognitive function(s) – the “scenario” – is required. A flowchart is provided that guides such analysis, and shows how a given neuropsychological scenario leads to the selection of an appropriate statistical method for detecting dissociations, introducing the critical concept of “deficit equivalence criterion” – the definition of what exactly a non-dissociation should look like. One further, overlooked problem concerning standardized scores in general (as measures of effect size, of which neuropsychological dissociations are just one example) is that they cannot be meaningfully compared if they have different reliabilities.
In conclusion, when studying dissociations, increases in false-positive and false-negative risks are likely to occur when no explicit neuropsychological theory is offered that justifies the definition of what are to be
considered as equivalent deficit severities in both performances, and which would lead to appropriate selection of raw, standardized, or any other type of score. More generally, the choice of any measure in any research context needs explicit theoretical modelling, without which statistical risks cannot be controlled.

According to the dominant focus model, the differential activation of the thalamocortical network is a sufficient condition for the diversity of states of consciousness to occur, and coherent patterns of interactive forebrain activation peaks are sufficient to generate specific conscious figures against ground. These minimal assumptions are consonant with the known properties of unilateral neglect. It becomes unnecessary to suppose that consciousness is an independent entity, occupies a dedicated location in the brain, is contingent on a minimal level of neural complexity, plays a causal role in enabling perception or action, or evolved because it plays any such role.

According to a longstanding view, inferior as opposed to superior parietal cortex critically contributes to the spatial attentional deficits encountered following unilateral parietal ischemic lesions. We review the evidence on which this view is based and contrast it with more recent structural lesion evidence concerning the critical role of the intraparietal sulcus in spatial attention deficits. In a classical spatial cueing paradigm, focal lesions of the posterior and of the middle segment of the intraparietal sulcus
give rise to a pathological invalidity effect that is indistinguishable from that seen after classical inferior parietal lesions. When a competing distracter is added to a target stimulus, the deleterious consequences of focal IPS lesions are again very similar to those classically observed following inferior parietal lesions. The deficit could not be accounted for by functional effects at a distance affecting inferior parietal cortex. These single-case lesion data establish the critical role of the posterior and the middle IPS segment in spatially selective attention and are in line with a vast amount of functional imaging evidence in the intact brain pointing to the prominent role of the intraparietal sulcus in spatial attention, along with inferior parietal cortex under specific circumstances. Functional imaging has also provided hints about
the differences in functional contribution between inferior and superior parietal cortex. These hypotheses await further confirmation based on lesion evidence.

In the late 1970's Edoardo Bisiach and his coworkers provided definitive evidence that spatial unilateral neglect involves a disorder of the internal representation of extra-personal space. A few years later Bisiach and Berti (1987) revived the so far neglected contribution of an Austrian neurologist, Hermann Zingerle (1913). Ninety years ago Zingerle had described the symptom-complex of two right-brain-damaged patients, who showed left hemisomatoagnosia, unawareness of left hemiplegia, and left motor neglect. In addition to the detailed case reports, Zingerle had put forward a unitary interpretation of these deficits in terms of a disordered representation of one side of the body (dyschiria). A unitary representational account of these unilateral impairments was conspicuously absent in the contemporary neurological literature (Anton, Pick, Babinski), and attracted Bisiach's interest. An abridged translation of Zingerle's paper is provided. The clinical case reports and Zingerle's conclusions are discussed, with reference both to Bisiach's views, and to present knowledge of unilateral spatial neglect.

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.

Unilateral spatial neglect is defined as a disorder in which a patient fails to pay attention to stimuli presented to the contralateral side of the lesion; it is known to be associated with decreased functional independence. Our objective was to determine the suitability and feasibility of using a PC-based, non-immersive VR system for training individuals with unilateral spatial neglect to cross streets in a safe and vigilant manner. A virtual environment, consisting of a typical city street, was programmed via Superscape’s 3D-Webmaster, a 3D web-authoring tool. Twelve subjects, aged 55 to 75 years, participated. Results demonstrated that this virtual environment was suitable in both its cognitive and motor demands for the targeted population. With very few exceptions, the control subjects were able to complete all levels of the program with success. The performance of the patient subjects was considerably more variable, and they were able to complete fewer levels, and usually took...

Recently, several theorists have proposed that we can perceive a range of high-level features, including natural kind features (e.g., being a lemur), artifactual features (e.g., being a mandolin), and the emotional features of others (e.g., being surprised). I clarify the claim that we perceive high-level features and suggest one overlooked reason this claim matters: it would dramatically expand the range of actions perception-based theories of action might explain. I then describe the influential phenomenal contrast method of arguing for high-level perception and discuss some of the objections that have been raised against this strategy. Finally, I describe two emerging defenses of high-level perception, one of which appeals to a certain class of perceptual deficits and one of which appeals to adaptation effects. I sketch a challenge for the latter approach.

Recent cognitive models of numerical abilities have postulated that number processing may in part rely on a representation of quantities where magnitude is organized by spatial proximity, along a "mental number line" extending from left to right. We describe four experiments that examined whether such a spatial representation of number would be affected by the presence of unilateral neglect after right hemisphere damage. When asked to judge whether a single number shown at fixation was smaller or larger than "5", patients with neglect were selectively slower to respond to "4", but when asked to compare numbers to "7" they were selectively slower to respond to "6". This is consistent with a representational deficit for numbers located to the left of a reference point along the mental number line and was not found in other right brain-damage patients without neglect. No effect of represented number position was found in a non-numerical task requiring judgements of the physical size of single digit characters. Finally, when asked to classify numbers as indicating hours earlier or later than six o'clock, neglect patients showed a reverse pattern with slower responses to numbers larger than "6', consistent with a representational deficit for hour numbers located on the left side of an imagined clock-face. Our findings demonstrate that unilateral spatial neglect may produce specific representational deficits in number processing that implicate different spatial representations according to the task demands.