Left neglect for near but not far space in man

Tonic and phasic alertness training: a novel behavioral therapy to improve spatial and non-spatial attention in patients with hemispatial neglect

Hemispatial neglect is a debilitating disorder marked by a constellation of spatial and non-spatial attention deficits. Patients’ alertness deficits have shown to interact with lateralized attention processes and correspondingly, improving tonic/general alertness as well as phasic/moment-to-moment alertness has shown to ameliorate spatial bias. However, improvements are often short-lived and inconsistent across tasks and patients. In an attempt to more effectively activate alertness mechanisms by exercising both tonic and phasic alertness, we employed a novel version of a continuous performance task (tonic and phasic alertness training, TAPAT). Using a between-subjects longitudinal design and employing sensitive outcome measures of spatial and non-spatial attention, we compared the effects of 9 days of TAPAT (36 min/day) in a group of patients with chronic neglect (N = 12) with a control group of chronic neglect patients (N = 12) who simply waited during the same training period. Compared to the control group, the group trained on TAPAT significantly improved on both spatial and non-spatial measures of attention with many patients failing to exhibit a lateralized attention bias at the end of training. TAPAT was effective for patients with a range of behavioral profiles and lesions, suggesting that its effectiveness may rely on distributed or lower-level attention mechanisms that are largely intact in patients with neglect. In a follow-up experiment, to determine if TAPAT is more effective in improving spatial attention than an active treatment that directly trains spatial attention, we trained three chronic neglect patients on both TAPAT and search training. In all three patients, TAPAT training was more effective in improving spatial attention than search training suggesting that, in chronic neglect, training alertness is a more effective treatment approach than directly training spatial attention.

Altered spatial distribution of visual attention in near and far space after early deafness

Early deafness results in a redistribution of more attentional resources to the visual periphery in near space, specifically under conditions of selective attention, probably to compensate for the loss of auditory alertness to potentially dangerous stimuli from outside the current attentional focus. It remains poorly understood, however, whether spatial distribution of attention in far space is altered by early deafness as well. In the present study, we investigated whether and how early deafness alters the distribution of visuospatial attention in far space, compared to hearing controls. We asked deaf individuals and hearing controls to perform a flanker task with either peripheral or central distractors, either in near or far space. Sizes of compatibility effect were used to assess the amount of attentional resources received by the peripheral and central distractors. In near space, peripheral distractors induced significantly larger compatibility effect in deaf individuals than in hearing controls while central distractors induced significantly larger compatibility effect in hearing controls than in deaf individuals. On the other hand in far space, although peripheral distractors induced equivalent sizes of compatibility effect in the deaf and hearing groups, central distractors caused significant compatibility effect only in deaf individuals, but not in hearing controls. Our results suggest that early deafness results in a redistribution of visuospatial attention not only in near space but also in far space, with enhanced peripheral attention in near space and enhanced central attention in far space.

Different spatial memory systems are involved in small- and large-scale environments: evidence from patients with temporal lobe epilepsy

Recent reports show that humans and animals do not acquire information about routes and object locations in the same way. In spatial memory, a specific sub-system is hypothesized to be involved in encoding, storing and recalling navigational information, and it is segregated from the sub-system devoted to small-scale environment. We assessed this hypothesis in a sample of patients treated surgically for intractable temporal lobe epilepsy. We found double dissociations between learning and recall of spatial positions in large space versus small space. These results strongly support the hypothesis that two segregate systems process navigational memory for large-scale environments and spatial memory in small-scale environments.

The neural mechanisms of visual selection: the view from neuropsychology

In this review, we discuss how neuropsychological impairments in visual selection can inform us about how selection normally operates. Using neuroanatomical and behavioral evidence on the disorders of neglect, extinction, and simultanagnosia, we propose functional and anatomical links between different aspects of visual selection and distinct sites in the posterior parietal cortex (PPC). This includes linking: (i) bottom-up attentional capture and the right temporo-parietal junction (TPJ); (ii) top-down segmentation of displays and the medial PPC; (iii) grouping, individuation and identification, and the inferior intra-parietal sulcus (IPS) bilaterally; and (iv) the suppression of saliency and the left IPS. In addition, when neuropsychological studies are combined with fMRI, there is evidence that these regions of the PPC interact with striate and extra-striate cortical areas, which respond to specific properties of stimuli. Selection should be viewed as an emergent property of a network of areas involving both ventral and dorsal cortex.

Isolating the internal in endogenous attention

Neuroimaging studies have provided evidence that a bilateral frontal-parietal network is involved in voluntary attentional control. However, because those studies used instructive cue stimuli, some of the activity may have been due to interactions between cue processing and voluntary orienting. Here, we show that self-initiated voluntary orienting, in the absence of any cue stimulus, evokes activity in this frontal-parietal network. In contrast to the typical symmetric activity observed with cued attentional shifts, self-initiated shifts showed a hemispheric asymmetry consistent with studies of unilateral neglect patients. Specifically, the right hemisphere was equally involved in orienting to either visual field, whereas the left hemisphere was biased toward the contralateral field. Our data show that the asymmetry of attentional control can be revealed in neuroimaging of healthy subjects, when voluntary orienting is effectively isolated.

Neuropsychological inference with an interactive brain: A critique of the “locality” assumption

When cognitive neuropsychologists make inferences about the functional architecture of the normal mind from selective cognitive impairments they generally assume that the effects of brain damage are local, that is, that the nondamaged components of the architecture continue to function as they did before the damage. This assumption follows from the view that the components of the functional architecture are modular, in the sense of being informationally encapsulated. In this target article it is argued that this “locality” assumption is probably not correct in general. Inferences about the functional architecture can nevertheless be made from neuropsychological data with an alternative set of assumptions, according to which human information processing is graded, distributed, and interactive. These claims are supported by three examples of neuropsychological dissociations and a comparison of the inferences obtained from these impairments with and without the locality assumption. The three dissociations are: selective impairments in knowledge of living things, disengagment of visual attention, and overt face recognition. In all three cases, the neuropsychological phenomena lead to more plausible inferences about the normal functional architecture when the locality assumption is abandoned. Also discussed are the relations between the locality assumption in neuropsychology and broader issues, including Fodor's modularity hypothesis and the choice between top-down and bottom-up research approaches.

Do perceptual asymmetries differ in peripersonal and extrapersonal space?

A space-based dissociation has been observed in clinical hemineglect, wherein neglect can be specific to either peripersonal or extrapersonal space. This same dissociation might occur in pseudoneglect, where both space-based and visual field differences have been observed. Upper and bottom visual field differences were examined within-subjects (N = 39), by presenting the greyscales task in both peripersonal and extrapersonal space. The leftward bias was strongest in the bottom visual field; however, no space-based differences were observed. It appears that perceptual biases differ between the upper and bottom visual fields, but this is not related to space-based perceptual biases.

Neuroanatomy of hemispatial neglect and its functional components: a study using voxel-based lesion-symptom mapping

Spatial neglect is a perplexing neuropsychological syndrome, in which patients fail to detect (and/or respond to) stimuli located contralaterally to their (most often right) hemispheric lesion. Neglect is characterized by a wide heterogeneity, and a role for multiple components has been suggested, but the exact nature of the critical components remains unclear. Moreover, many different lesion sites have been reported, leading to enduring controversies about the relative contribution of different cortical and/or subcortical brain regions. Here we report a systematic anatomo-functional study of 80 patients with a focal right hemisphere stroke, who were examined by a series of neuropsychological tests assessing different clinical manifestations of neglect. We first performed a statistical factorial analysis of their behavioural performance across all tests, in order to break down neglect symptoms into coherent profiles of co-varying deficits. We then examined the neural correlates of these distinct neglect profiles using a statistical voxel-based lesion-symptom mapping method that correlated the anatomical extent of brain damage with the relative severity of deficits along the different profiles in each patient. Our factorial analysis revealed three main factors explaining 82% of the total variance across all neglect tests, which suggested distinct components related to perceptive/visuo-spatial, exploratory/visuo-motor, and allocentric/object-centred aspects of spatial neglect. Our anatomical voxel-based lesion-symptom mapping analysis pointed to specific neural correlates for each of these components, including the right inferior parietal lobule for the perceptive/visuo-spatial component, the right dorsolateral prefrontal cortex for the exploratory/visuo-motor component, and deep temporal lobe regions for the allocentric/object-centred component. By contrast, standard anatomical overlap analysis indicated that subcortical damage to paraventricular white matter tracts was associated with severe neglect encompassing several tests. Taken together, our results provide new support to the view that the clinical manifestations of hemispatial neglect might reflect a combination of distinct components affecting different domains of spatial cognition, and that intra-hemispheric disconnection due to white matter lesions might produce severe neglect by impacting on more than one functional domain.

Bisecting the mental number line in near and far space

Much evidence suggests that common posterior parietal mechanisms underlie the orientation of attention in physical space and along the mental number line. For example, the small leftward bias (pseudoneglect) found in paper-and-pencil line bisection is also found when participants "bisect" number pairs, estimating (without calculating) the number midway between two others. For bisection of physical lines, pseudoneglect has been found to shift rightward as lines are moved from near space (immediately surrounding the body) to far space. We investigated whether the presentation of stimuli in near or far space also modulated spatial attention for the mental number line. Participants bisected physical lines or number pairs presented at four distances (60, 120, 180, 240cm). Clear rightward shifts in bias were observed for both tasks. Furthermore, the rate at which this shift occurred in the two tasks, as measured by least-squares regression slopes, was significantly correlated across participants, suggesting that the transition from near to far distances induced a common modulation of lateral attention in physical and numerical space. These results demonstrate a tight coupling between number and physical space, and show that even such prototypically abstract concepts as number are modulated by our on-line interactions with the world.

Dissociations and interactions between time, numerosity and space processing

This study investigated time, numerosity and space processing in a patient (CB) with a right hemisphere lesion. We tested whether these magnitude dimensions share a common magnitude system or whether they are processed by dimension-specific magnitude systems. Five experimental tasks were used: Tasks 1-3 assessed time and numerosity independently and time and numerosity jointly. Tasks 4 and 5 investigated space processing independently and space and numbers jointly. Patient CB was impaired at estimating time and at discriminating between temporal intervals, his errors being underestimations. In contrast, his ability to process numbers and space was normal. A unidirectional interaction between numbers and time was found in both the patient and the control subjects. Strikingly, small numbers were perceived as lasting shorter and large numbers as lasting longer. In contrast, number processing was not affected by time, i.e. short durations did not result in perceiving fewer numbers and long durations in perceiving more numbers. Numbers and space also interacted, with small numbers answered faster when presented on the left side of space, and the reverse for large numbers. Our results demonstrate that time processing can be selectively impaired. This suggests that mechanisms specific for time processing may be partially independent from those involved in processing numbers and space. However, the interaction between numbers and time and between numbers and space also suggests that although independent, there maybe some overlap between time, numbers and space. These data suggest a partly shared mechanism between time, numbers and space which may be involved in magnitude processing or may be recruited to perform cognitive operations on magnitude dimensions.

Priming of reach trajectory when observing actions: hand-centred effects

When another person's actions are observed it appears that these actions are simulated, such that similar motor processes are triggered in the observer. Much evidence suggests that such simulation concerns the achievement of behavioural goals, such as grasping a particular object, and is less concerned with the specific nature of the action, such as the path the hand takes to reach the goal object. We demonstrate that when observing another person reach around an obstacle, an observer's subsequent reach has an increased curved trajectory, reflecting motor priming of reach path. This priming of reach trajectory via action observation can take place under a variety of circumstances: with or without a shared goal, and when the action is seen from a variety of perspectives. However, of most importance, the reach path priming effect is only evoked if the obstacle avoided by another person is within the action (peripersonal) space of the observer.

The parietal cortex and the representation of time, space, number and other magnitudes

The development of sub-disciplines within cognitive neuroscience follows common sense categories such as language, audition, action, memory, emotion and perception among others. There are also well-established research programmes into temporal perception, spatial perception and mathematical cognition that also reflect the subjective impression of how experience is constructed. There is of course no reason why the brain should respect these common sense, text book divisions and, here, we discuss the contention that generalized magnitude processing is a more accurate conceptual description of how the brain deals with information about time, space, number and other dimensions. The roots of the case for linking magnitudes are based on the use to which magnitude information is put (action), the way in which we learn about magnitudes (ontogeny), shared properties and locations of magnitude processing neurons, the effects of brain lesions and behavioural interference studies. Here, we assess this idea in the context of a theory of magnitude, which proposed common processing mechanisms of time, space, number and other dimensions.

Recovery from unilateral neglect after right-hemisphere stroke

PURPOSE

To show the recovery process for different forms of unilateral neglect (UN)--including personal neglect and neglect of far space--in relationship to impairment, disability, cognition and mood.

METHOD

Patients were tested at 2-4 weeks, at 6 months and at 1 year. We used the Behaviour Inattention Test and a test for personal neglect. We also used the NIH Stroke Scale, the Functional Independence Measure (FIM), the Mini-Mental State Evaluation and the Geriatric Depression Scale.

RESULTS

Peripersonal neglect diminishes within 6 months, but complete recovery occurred in only 13%. The prognosis for personal neglect and neglect of far space is better, with a recovery ratio at 6 months of 52% and 46%, respective. The correlations between UN and FIM are high. A few patients deteriorate in the absence of recurrent stroke.

CONCLUSIONS

For clinical purposes, it is practical to postpone UN evaluation until a couple of weeks after a stroke. Many of the patients who then have UN are likely to retain their UN, although many will improve. Patients with UN should receive special attention in the rehabilitation phase, as well as at discharge. One explanation of the worsening of UN seen in some patients, may be continuing cerebral atherosclerosis.

Virtual reality and the role of the prefrontal cortex in adults and children

In this review, the neural underpinnings of the experience of presence are outlined. Firstly, it is shown that presence is associated with activation of a distributed network, which includes the dorsal and ventral visual stream, the parietal cortex, the premotor cortex, mesial temporal areas, the brainstem and the thalamus. Secondly, the dorsolateral prefrontal cortex (DLPFC) is identified as a key node of the network as it modulates the activity of the network and the associated experience of presence. Thirdly, children lack the strong modulatory influence of the DLPFC on the network due to their unmatured frontal cortex. Fourthly, it is shown that presence-related measures are influenced by manipulating the activation in the DLPFC using transcranial direct current stimulation (tDCS) while participants are exposed to the virtual roller coaster ride. Finally, the findings are discussed in the context of current models explaining the experience of presence, the rubber hand illusion, and out-of-body experiences.

Near space functioning of the human angular and supramarginal gyri

The posterior parietal cortex (PPC) has been associated with the encoding of events in peripersonal space, but little is known about the precise segregation of parietal areas involved specifically in 'near-space' visuospatial processing. This study applied transcranial magnetic stimulation (TMS) to two parietal areas: the right angular gyrus (ANG) and the right supramarginal gyrus (SMG) in addition to a control site, cortical visual area V5, while subjects performed symmetry judgements on lines presented simultaneously in the left and right visual fields. Eight subjects performed the task with the stimuli presented either in peripersonal or extra personal space. As expected, TMS over the right ANG caused subjects to report lines as being longer ipsilateral to the stimulation site, but only in near space. TMS of the right SMG, however, induced a bias shift in both near and far space, but the change only reached significance in near space. Our findings suggest that, consistent with its role in somatosensory functions, the SMG, like the ANG, is specialised for near space.

Is that within reach? fMRI reveals that the human superior parieto-occipital cortex encodes objects reachable by the hand

Macaque neurophysiology and human neuropsychology results suggest that parietal cortex encodes a unique representation of space within reach of the arm. Here, we used slow event-related functional magnetic resonance imaging (fMRI) to investigate whether human brain areas involved in reaching are more activated by objects within reach versus beyond reach. In experiment 1, graspable objects were placed at three possible locations on a platform: two reachable locations and one beyond reach. On some trials, participants reached to touch or grasp objects at the reachable location; on other trials participants passively viewed objects at one of the three locations. A reach-related area in the superior parieto-occipital cortex (SPOC) was more activated for targets within reach than beyond. In experiment 2, we investigated whether this SPOC response occurred when visual and motor confounds were controlled and whether it was modulated when a tool extended the effective range of the arm. On some trials, participants performed grasping and reaching actions to a reachable object location using either the hand alone or a tool; on other trials, participants passively viewed reachable and unreachable object locations. SPOC was significantly more active for passively viewed objects within reach of the hand versus beyond reach, regardless of whether or not a tool was available. Interestingly, these findings suggest that neural responses within brain areas coding actions (such as SPOC for reaching) may reflect automatic processing of motor affordances (such as reachability with the hand).

Visual search patterns in neglect: comparison of peripersonal and extrapersonal space

Previous studies of visual search patterns in visuospatial neglect have analyzed shifts of attention during search tasks using eye tracking technology and verbal reports. The purpose of the present study was to replicate and extend upon reported parameters of visual scanning patterns of neglect patients in peripersonal space (within arms reach) and to examine whether similar patterns of visual search are also apparent in extrapersonal space (beyond arms reach). Using a simple verbal visual search and target detection paradigm right-hemisphere stroke participants, with and without neglect, and healthy older volunteers named targets on scanning sheets placed in peripersonal and extrapersonal space. The healthy controls and right-hemisphere stroke group without neglect showed similar 'reading' type strategies, while the neglect group displayed an unsystematic search pattern, during search in both peripersonal and extrapersonal space. Group comparisons of search parameters support the presence of multiple cognitive deficits affecting the complex visual search patterns of neglect patients, including a rightward attentional bias, a reduced spatial scale of attention (local processing bias), and a deficit of working memory affecting both near and far space search. Ventral visual stream damage and neglect, however, were related to slower target report rate and more misidentification errors in extrapersonal space. The ease of administration of this verbal target detection task in both peripersonal and extrapersonal space, and the relationship of the measures produced to theorized attentional and executive deficits in neglect, provide impetus for further research on the severity and independence of individual scanning deficits in neglect.

Screening tests are not enough to detect hemineglect

OBJECTIVE

To verify the sensitivity of the conventional subtests of the Behavioral Inattention Test (BIT) in the diagnosis of hemineglect after stroke.

METHOD

One hundred and two patients with cerebral infarct or hemorrhage were prospectively evaluated. In 22, hemineglect was diagnosed using standard BIT criteria. The frequency of hemineglect using 6 commonly used screening subtests of this battery was assessed.

RESULTS

Hemineglect would not be recognized in 10 patients if they were only screened using the line crossing test; this would be the case in 2 patients with the letter cancellation test; and in 4 patient with the line bisection test. Three patients would not be diagnosed even if both line crossing and line bisection tests were used.

CONCLUSION

Hemineglect may not be recognized with single screening tests commonly used. The use of a standard battery is recommended to improve diagnostic sensitivity in individuals with various subtypes of hemineglect.

Spatial neglect: clinical and neuroscience review: a wealth of information on the poverty of spatial attention

Hemispatial neglect (HSN) is a frequent, conspicuous neurobehavioral accompaniment of brain injury. Patients with HSN share several superficial similarities, leading earlier clinical neuroscientists to view neglect as a unitary condition associated with brain structures that mediate relatively discrete spatial cognitive mechanisms. Over the last two decades, research largely deconstructed the neglect syndrome, revealing a remarkable heterogeneity of behaviors and providing insight into multiple component processes, both spatial and nonspatial, that contribute to hemispatial neglect. This review surveys visual HSN, presenting first the means for detection and diagnosis in its manifold variations. We summarize cognitive operations relevant to spatial attention and evidence for their role in neglect behaviors and then briefly consider neural systems that may subserve the component processes. Finally, we propose several methods for rehabilitating HSN, including the challenges facing remediation of such a heterogeneous cognitive disorder.

Language within your reach: near-far perceptual space and spatial demonstratives

Spatial demonstratives (this/that) play a crucial role when indicating object locations using language. However, the relationship between the use of these proximal and distal linguistic descriptors and the near (peri-personal) versus far (extra-personal) perceptual space distinction is a source of controversy [Kemmerer, D. (1999). "Near" and "far" in language and perception. Cognition 73, 35-63], and has been hitherto under investigated. Two experiments examined the influence of object distance from speaker, tool use (participants pointed at objects with their finger/arm or with a stick), and interaction with objects (whether or not participants placed objects themselves) on spatial demonstrative use (e.g. this/that red triangle) in English (this/that) and Spanish (este/ese/aquel). The results show that the use of demonstratives across two languages is affected by distance from speaker and by both tool use and interaction with objects. These results support the view that spatial demonstrative use corresponds with a basic distinction between near and far perceptual space.

Improved visual sensitivity in the perihand space

Studies in monkeys and humans suggest a dissociation between the visual fields near and far from the hand. In this study, we investigated visual detection and spatial discrimination in near- and far-hand fields using the stimulus of a flashing light emitting diode placed near (1 cm) and/or far (40 cm) from the hand. We found that there was greater accuracy (i.e., fewer errors) in the near-hand field. Control experiments indicated that (a) the superior near-hand detection performance was not due to response strategies, (b) the hand did not serve as a spatial reference, (c) the greater accuracy in the near-hand field did not reflect within-hemisphere or within-hemispace facilitation and (d) the effect appeared to be essentially due to viewing of the hand but not proprioceptive information. The results suggest there is an interconnected system for integrated (visual-tactile) coding of peripersonal space centered on body parts and comprising bimodal visuo-tactile cells.

Subjective time in near and far representational space

OBJECTIVE

We set out to measure healthy subjects' estimates of temporal duration during the imagination of left and right sides of an object located in either near or far representational space.

BACKGROUND

Duration estimates during the observation of small-scale scenes are shorter than those during the observation of the same scenes presented in a larger scale. It is not known whether a similar space-time relationship also exists for objects merely imagined and whether subjective time varies with a forced focus on either the left or the right side of a mental image.

METHODS

Eyes closed, 40 healthy, right-handed subjects (20 women) had to imagine a standard Swiss railway clock either at a distance of 30 cm or 6 m. They were required to focus on the imagined movement of the second hand and provide estimates of elapsed durations of 15 and 30 seconds. Separate estimates for the left and right side of the clockface were obtained. The magnitude of implicit line bisection error was assessed in a separate task.

RESULTS

Irrespective of side of the clockface, duration estimates were shorter for the clockface imagined in far space than for the one imagined immediately in front of the inner eye. For men, but not women, duration judgments (left relative to right side of the clockface) correlated with relative lengths of left and right line segments in the bisection task.

CONCLUSIONS

Subjective time seems to run faster during the inspection of a small-size compared with a larger-size mental image. This finding underlines the equivalence of the laws that guide both exploration and representation of space. Together with the observed correlation between spatial and temporal measures of lateral asymmetries, the result also illustrates the conceptual similarities in the processing of space and time. The normative data presented here may be useful for clinical applications of the paradigm in patients with hemispatial neglect or a distorted perception of time.

Low arousal modulates visuospatial attention in three-dimensional virtual space

Clinical, experimental, and functional imaging studies suggest overlapping neuronal networks and functional interactions of alertness and visuospatial attention within the right hemisphere of the brain. To examine the interaction of arousal and visuospatial attention in peripersonal and extrapersonal virtual space, we tested 20 healthy male adults during 24 hr of sleep deprivation at four points during the night (9 p.m., 1 a.m., 5 a.m., and 9 a.m.). The main finding concerning covert orienting in a virtual environment is a highly significant slowing of reorientation toward the left visual hemifield in extrapersonal space due to decreased arousal. The results provide additional evidence for the proposed anatomical and functional overlap of the two attentional systems and indicate a modulation of visuospatial attention by the level of arousal in extrapersonal space.

Visual hemispatial neglect, re-assessed

Increased computer use in clinical settings offers an opportunity to develop new neuropsychological tests that exploit the control computers have over stimulus dimensions and timing. However, before adopting new tools, empirical validation is necessary. In the current study, our aims were twofold: to describe a computerized adaptive procedure with broad potential for neuropsychological investigations, and to demonstrate its implementation in testing for visual hemispatial neglect. Visual search results from adaptive psychophysical procedures are reported from 12 healthy individuals and 23 individuals with unilateral brain injury. Healthy individuals reveal spatially symmetric performance on adaptive search measures. In patients, psychophysical outcomes (as well as those from standard paper-and-pencil search tasks) reveal visual hemispatial neglect. Consistent with previous empirical studies of hemispatial neglect, lateralized impairments in adaptive conjunction search are greater than in adaptive feature search tasks. Furthermore, those with right hemisphere damage show greater lateralized deficits in conjunction search than do those with left hemisphere damage. We argue that adaptive tests, which automatically adjust to each individual's performance level, are efficient methods for both clinical evaluations and neuropsychological investigations and have the potential to detect subtle deficits even in chronic stages, when flagrant clinical signs have frequently resolved.

Pure representational neglect and navigational deficits in a case with preserved visuo-spatial working memory

We describe a patient who, after right hemisphere damage, showed severe, persistent, pure representational neglect but no evidence of perceptual neglect and no deficits in spatial working memory when evaluated with a traditional clinical test (Corsi Block Tapping test). This finding provides evidence against a full explanation of representational neglect within the context of visuo-spatial working memory. Indeed, this patient showed a peculiar deficit in navigational tasks requiring re-orientation in a novel environment by means of his mental representation of the environment. Since no representational neglect was observed in tests requiring mental representation of single or multiple objects (i.e., o'clock test) we suggest that in our patient representational neglect is caused by damage to the cognitive system involved in coding and storing environmental information to be used during navigation.