Constructional apraxia refers to the inability of patients to copy accurately drawings or three-dimensional constructions. It is a common disorder after right. Abstract. Constructional apraxia refers to the inability of patients to copy accurately drawings or three-dimensional constructions. It is a common. Constructional apraxia. Article (PDF Available) · January with Reads. Export this citation. Sharon Cermak at University of Southern California.
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Crinion, Sheila Merola, Masud Husain; A deficit of spatial remapping in constructional apraxia after right-hemisphere stroke, BrainVolumeIssue 4, 1 AprilPages —, https: Constructional apraxia refers to the inability construcrional patients to copy accurately drawings or three-dimensional constructions. It is a common disorder after right parietal stroke, often persisting after initial problems such as visuospatial neglect have resolved.
However, there has been very little experimental investigation regarding mechanisms that might contribute to the syndrome. Here, we examined whether a key deficit might be failure to apraixa visual information correctly from one fixation to the next.
Specifically, we tested whether this deficit might concern remapping of spatial locations across saccades. Right-hemisphere stroke patients with constructional apraxia were compared to patients without constructional problems and neurologically healthy controls. Participants judged whether a pattern construtional position spatial task or changed in pattern non-spatial task across two saccades, consructional to a control condition with an equivalent delay but without intervening eye movements.
Patients with constructional apraxia were found to be significantly impaired in position judgements with intervening saccades, particularly when the first saccade of the sequence was to the right. The importance of these remapping deficits in constructional apraxia was confirmed through a highly significant correlation between saccade task performance and constructional impairment on standard neuropsychological tasks.
These findings provide the first evidence for a deficit in remapping visual information across saccades underlying right-hemisphere constructional apraxia. Severe deficits in constructional skills such as drawing, copying and building 3D constructionql are a common yet poorly understood outcome of hemispheric stroke e.
Kirk and Kertesz, ; Ala et al. First defined as constructional apraxia by Kleist inpatients with this form of apraxia have no difficulty in making relevant individual movements but are unable to copy even simple drawings accurately.
The deficits seen in copying and drawing are diverse across patient groups, with striking differences in performance between focal lesion patients with right as opposed to left hemisphere damage e. Characteristic of the drawings of right-hemisphere patients with constructional apraxia are the lack of accurate spatial relations between components of objects and an incoherent, disjointed quality.
However, damage to the left wpraxia produces qualitatively different drawing performance with an oversimplification of figures and a perseveration on items suggestive aprxxia planning deficits Gainotti and Tiacci, ; Trojano and Conson, for a recent review of constructional deficits.
Indeed, the range of brain regions implicated and the dissimilarity of inter-group symptoms suggest that a unifying explanation for all constructional apraxia is unlikely to be forthcoming or otherwise useful e. Gainotti, ; Vallar, An additional factor limiting full understanding of these deficits is the involvement of a widespread network of brain areas in the cognitive, perceptual and motor processes required for accurate copying, drawing and construction Trojano et al.
In order to comprehend these deficits fully, it is essential to examine patients who differ both in hemisphere damaged and symptom presentation separately, as the mechanisms involved are likely to be very different Laeng, Precisely delineating the component, contributing impairment will be essential in order to resolve the exact mechanisms underlying constructional deficits after stroke.
Here, we examine the mechanisms that underlie constructional apraxia following right-hemisphere stroke. Constructional impairments are present acutely in a large proportion of such patients Hier et al. The right-hemisphere region most strongly implicated in constructional skills is the parietal cortex, as damage here has been reliably found qpraxia lead to enduring constructional apraxia e.
Gainotti, ; Grossi and Trojano, Neuropsychological evidence of parietal involvement is supported by functional imaging studies of healthy individuals, which have highlighted parietal constructionwl in drawing from copying e. Copying performance in patients with right-hemisphere constructinoal apraxia reveals specific deficits in correctly replicating the spatial relationships of items in complex figures Fig.
Patients do not necessarily fail to notice or copy individual elements and do not have distinctly lateralized impairments as in neglect, but rather the correct spatial relationships between items are lost and elements are transposed, almost piecemeal, to different positions or orientations. Previous attempts to quantify and understand these problems have often focused on analysing and understanding drawing and copying performance itself e.
Whilst this is entirely reasonable given that these are the impairments from which patients suffer, the large number of processes involved in copying might preclude precise analysis of the discrete cognitive functions affected. In order to delineate precisely the deficit involved, here we examine whether a specific function of right parietal cortex—remapping of visual information when we move our eyes see Duhamel et al. B and C Examples from two of the patients in this study.
Colours indicate the order in which the patient drew different elements. The order colours were given to patients was red, blue, green and finally yellow in B and black in C.
Despite the retinal position of the visual input changing every time we move our eyes, we perceive the world as stable. The visual system appears to encode information about the upcoming saccade such as its direction and distance to enable remapping of the old retinal location with respect to new eye positions Matin, ; Bridgeman et al.
Evidence suggests that the parietal lobes particularly the right in humans are critical for this remapping of spatial position across saccades e.
Apraaxia classic double-step paradigm, often used to assess spatial remapping processes, is adapted from neurophysiological experiments that have delineated areas of monkey aprxia involved in remapping across eye movements Duhamel et al. During the double-step procedure, two sequential saccadic targets are presented and extinguished before the participant commences the eye movement towards the first target.
Experiments using this paradigm have suggested that patients with parietal damage fail to make constructiona, second saccades as they do not correctly update the position of the second target. These authors describe this pattern of decrement as demonstrating that failed mechanisms in the damaged right cortex are unable a;raxia remap the retinotopic location of the second target once a saccade has been initiated into impaired hemispace. Related studies in neurologically healthy populations using functional MRI have confirmed the parietal cortex as being critically involved in tasks involving spatial updating across saccades e.
Recently, Vasquez and Danckert confirmed the dominance of the right hemisphere in spatial remapping processes as they examined performance in neurologically healthy individuals when they were required to make judgements after remapping locations overtly with eye movements or covertly without eye movements.
The importance of the right parietal cortex and the failure of some accounts of visuospatial neglect to account for all the features of the syndrome led Pisella and Mattingleyin a theoretical paper, to propose that impairments in spatial remapping processes underlie many deficits in neglect. For example, they suggest that the mislocation of items presented on the contralesional side is not adequately explained by purely attentional accounts of neglect, as these stimuli can often be briefly perceived but are then incorrectly attributed to the ipsilesional side of space Di Pellegrino and De Renzi, Highly relevant to this research, they emphasized that neglect patients often transpose elements from the contralesional side of the figure onto the ipsilesional side whilst they copy see Halligan et al.
The proposed involvement of spatial remapping impairments in visuospatial neglect was recently directly assessed Vuilleumier et al. These investigators were able to demonstrate that patients with neglect suffer from a failure to remap correctly the spatial location of a to-be-remembered target when they moved their eyes.
However, this deficit was particularly strong when they were required to move their eyes towards the ipsilesional side of space.
Free-Drawing from Memory in Constructional Apraxia: A Case Series :: Science Publishing Group
They exhibited a remapping of a saccade plan that was consistently less accurate if the first eye movement was consteuctional into contralesional apraixa Duhamel et al. In contrast, Vuilleumier and colleagues proposed that different processes are involved in the constructioonal types of task: This distinction is supported by neurophysiological studies by Colby et al.
Thus, it would have been necessary to preserve this leftwards remapped position in the neurons of the right parietal cortex. As this is the area damaged in these patients with neglect, this maintenance of spatial location would be severely impaired after any rightwards eye movement.
The lesions of patients with neglect participating in the study of Vuilleumier and colleagues are similar to those typically seen in patients with right-hemisphere constructional apraxia.
A deficit of spatial remapping in constructional apraxia after right-hemisphere stroke.
As figure copying requires precise integration of information across multiple eye movements, we sought to investigate whether patients with constructional apraxia might suffer from impairments in this process.
According to this account, constructionl observed in patients with constructional apraxia could reflect a loss of spatial information gained from previous fixations, leading these patients to be unable to correctly represent spatial relations of items whilst copying.
A recent neurophysiological study construtional linked impairments in constructional apraxia in a study of single cell recordings in monkeys performing a construction task Chafee et al.
Such a mechanism would support the remapping processes that help maintain stable visual percepts in the healthy brain and, as the authors assert, are likely to be critical in the problems suffered by right-hemisphere patients with constructional apraxia see also Averbeck et al. Accordingly, we have examined here whether patients with constructional apraxia are selectively impaired in the ability to remap spatial location information across saccades, as well as exploring whether any remapping impairment is specific to direction of saccade sequence.
Our novel paradigms investigate whether patients with right-hemisphere constructional apraxia have problems in maintaining spatial location information over intervening saccades, or even just one saccade. The direction of single saccades or saccade sequence might be critical, as previous research has found conflicting results.
Some researchers have reported that patients with similar lesions are worse when making saccades in a contralesional direction—i. Furthermore, it is important to assess whether any remapping impairments correlate with level of constructional impairment in right-hemisphere stroke patients, as indexed by standard neuropsychological tests. The paradigms outlined here will examine a possible key deficit that might contribute to constructional apraxia, a common disorder associated with stroke and several neurodegenerative conditions e.
Eight right-hemisphere patients with constructional apraxia aged 31—68 years mean These were compared to seven patients without constructional apraxia, also suffering from lesions in their right hemisphere non-constructional apraxia. The non-constructional apraxia group were aged 45—75 years mean 57 years. Four of the right-hemisphere control patients without constructional apraxia were also from this patient pool, whilst the other 4 were recruited from a research program at The National Hospital for Neurology and Neurosurgery.
A group of eight neurologically healthy volunteers also participated in the saccade studies age range: Figure 2 displays lesion plots for the patient groups. Lesion overlaps and subtractions of all patients. A constructional apraxia patient group, B non-constructional apraxia patient group, and C maps showing constructional apraxia lesions minus non-constructional apraxia.
Yellow indicates areas most damaged in patients with constructional apraxia and that were not damaged in the non-constructional apraxia group.
A T 1 -weighted template consisting of 12 axial slices was used to demarcate the lesions for constructional apraxia and non-constructional apraxia patients. As shown in Fig. Lesions of patients without constructional apraxia solely affected deep white matter and did not encroach upon cortical areas.
Subtracting the lesions of non-constructional apraxia from constructional apraxia patients reveals regions specific to these patients in the white matter adjacent to the temporoparietal junction, extending anteriorly to the insula see yellow regions in Fig. The anatomy presented here is given for completeness, but the principal purpose of the present experiment was to investigate whether there is a deficit of spatial remapping across saccades in constructional apraxia.
Patients within the hospital unit undergo regular screening for visuospatial neglect [a battery of tasks is used, which includes letter cancellation, line bisection, reading aloud, examination of more subtle perceptual problems with the Wundt—Jastrow test e. None of the patients revealed neglect clinically at the time of testing. The lesions seen in these patients with constructional apraxia suggest that it is likely some of them might have suffered from neglect immediately after their stroke, and it remains possible that analysis of reaction times might perhaps reveal that some of these patients are slower to respond to stimuli on the contralesional side.
However, detailed screening revealed that the patients with constructional apraxia fulfilled the clinical diagnosis of constructional apraxia and not of visuospatial neglect. All participants gave written informed consent according to the Declaration of Helsinki.
The study was approved by both the hospital and university research ethics committees. All tasks were programmed with Psyscope software Cohen et al. Participants sat approximately 50 cm from the computer screen.
Observers made judgements about the spatial location or form of a checkerboard pattern, either with or without intervening saccades.
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In all experiments, participants viewed two presentations of the checkerboard and had to judge apeaxia it comstructional moved vertical position in the position judgement conditions, or whether the pattern had altered in the pattern judgement conditions. In the saccade conditions, they made intervening saccades between seeing the first and second checkerboard, while in the no-saccade condition they maintained fixation during a delay. Detection of vertical displacement was chosen for a number of reasons.
First, healthy participants have been shown to suffer differential inaccuracies in detection of lateral movement according to the direction of their saccades, i. Additionally, patients with unilateral brain injury might have a response bias when making left or right judgements after right-hemisphere apraia, e. Finally, these parietal patients may also suffer from some disorientation in making left versus right decisions.
Each trial began with a small central fixation cross, presented for ms Fig. Black and white elements were randomly placed in this checkerboard, with certain constraints.
For example, there was a 3: Schematic outline of experimental paradigms from Experiment 1.