Search results for "unilateral neglect"
showing 9 items of 9 documents
Unconscious processing of Arabic numerals in unilateral neglect
2005
This study explores the processing of Arabic numerals in three patients with dense left unilateral neglect. Three tasks have been used: a test of visual awareness (is the stimulus on the left, on the right or on both sides?), a number comparison task (is the number larger or smaller than 5?), a number parity judgment task (is the number odd or even?). The test of visual awareness indicated that all three patients were completely unaware of the stimuli presented in the left hemifield. Despite this, the number comparison and number parity judgment tasks clearly indicated that Arabic numerals were unconsciously processed at semantic level (i.e. quantity). These results show that patients with …
Visuospatial processing in schizophrenia: Does it share common mechanisms with pseudoneglect?
2011
International audience; ''Schizophrenia patients demonstrate behavioural and cerebral lateralised anomalies, prompting some authors to suggest they exhibit a mild form of right unilateral neglect. To better describe and understand lateralised visuospatial anomalies in schizophrenia, three experiments were run using tasks often utilised to study visuospatial processing in healthy individuals and in neglect patients: the Behavioural Inattention Test (BIT), the manual line bisection task with and without a local cueing paradigm, the landmark task (or line bisection judgement), and the number bisection task. Although the schizophrenia patients did not exhibit the full-blown neglect syndrome, th…
Pseudoneglect in schizophrenia: A line bisection study with cueing
2007
Numerous authors have reported the existence of lateralised abnormalities towards the right side in patients with schizophrenia.In the present study, a manual line bisection task was used to assess the existence of a visuospatial bias in patients with schizophrenia as compared to healthy subjects and left unilateral neglect patients. In addition, we used a local cueing paradigm (consisting of a number placed on the right, on the left, or at both ends of the line).Healthy subjects showed a leftwards trend in the "no cue" condition (known as pseudoneglect) and neglect patients showed a right bias in all cue conditions. In contrast, patients with schizophrenia placed their manual estimation of…
Perceptual and response bias in visuospatial neglect due to frontal and parietal repetitive transcranial magnetic stimulation in normal subjects.
2002
Recently some authors have challenged the conventional association of directional motor neglect with damage of frontal structures, showing that pure sensory perceptual neglect (classically associated with parietal lesion) can follow damage of right frontal cortex. The aim of the present study was to assess the type of defect in visuo-spatial attention consequent upon a virtual frontal or parietal lesion induced by transcranial magnetic stimulation in normal subjects. To this purpose eleven subjects performed a visuo-spatial task requiring judgement about the length of the two segments of asymmetrically bisected horizontal lines, presented for 50 ms on a computer monitor. After each visual s…
Functional reorganization of the attentional networks in low-grade glioma patients: a longitudinal study.
2015
International audience; Right brain damage often provokes deficits of visuospatial attention. Although the spatial attention networks have been widely investigated in stroke patients as well as in the healthy brain, little is known about the impact of slow growing lesions in the right hemisphere. We here present a longitudinal study of 20 patients who have been undergoing awake brain surgery with per-operative line bisection testing. Our aim was to investigate the impact of tumour presence and of tumour resection on the functional (re)organization of the attention networks. We assessed patients' performance on lateralized target detection, visual exploration and line bisection before surger…
The middle house or the middle floor: Bisecting horizontal and vertical mental number lines in neglect
2007
Abstract This study explores the processing of mental number lines and physical lines in five patients with left unilateral neglect. Three tasks were used: mental number bisection (‘report the middle number between two numbers’), physical line bisection (‘mark the middle of a line’), and a landmark task (‘is the mark on the line to the left/right or higher/lower than the middle of the line?’). We manipulated the number line orientation purely by task instruction: neglect patients were told that the number-pairs represented either houses on a street (horizontal condition) or floors in a building (vertical condition). We also manipulated physical line orientation for comparison. All five negl…
Hyperexcitability of parietal-motor functional connections in the intact left-hemisphere of patients with neglect
2008
Hemispatial neglect is common after unilateral brain damage, particularly to perisylvian structures in the right-hemisphere (RH). In this disabling syndrome, behaviour and awareness are biased away from the contralesional side of space towards the ipsilesional side. Theoretical accounts of this in terms of hemispheric rivalry have speculated that the intact left-hemisphere (LH) may become hyper-excitable after a RH lesion, due to release of inhibition from the damaged hemisphere. We tested this directly using a novel twin-coil transcranial magnetic stimulation (TMS) approach to measure excitability within the intact LH of neglect patients. This involved applying a conditioning TMS pulse ove…
Far Space Remapping by Tool Use: A rTMS Study Over the Right Posterior Parietal Cortex
2015
Abstract Background In previous studies, rTMS has been successfully employed to interfere with the right posterior parietal cortex (rPPC) inducing neglect-like behavior in healthy subjects. Several studies have shown that the use of tools can modulate the boundaries between near and far space: indeed when far space is reached by the stick, far space can be remapped as near. Objective The aim of the present study was to investigate whether once that rTMS on the rPPC has selectively induced neglect-like bias in the near space (but not in the far space), neglect can appears also in the far space when the subjects used a tool to perform the task. Methods Fifteen right-handed healthy subjects ex…
Testing cognition and rehabilitation in unilateral neglect with wedge prism adaptation: multiple interplays between sensorimotor adaptation and spati…
2014
Spatial neglect is a neurological condition characterised by deficits for perceiving, attending, representing, and/or performing actions within their left-sided space, responsible for numerous debilitating effects in everyday life, for poor functional recovery, and for decreased ability to benefit from treatment. Exposure to a right lateral displacement of the visual field (induced by a simple target-pointing task with base-left wedge prisms) is known to directionally bias visuomotor coordination and can be compensated by both sensorimotor adaptation and cognitive processes. Sensorimotor adaptation gives rise to after-effects whose duration is amplified in neglect patients and has been repe…