Brain, Vol 121, Issue 12 2357-2367, Copyright © 1998 by Oxford University Press
HO Karnath, M Niemeier and J Dichgans
The present study investigated the gaze as well as the head and the eye-
in-head movements of neglect patients while they were exploring their
surroundings. A random configuration of letters was presented on the inner
surface of a sphere that surrounded the subject, requiring free exploratory
eye and head movements. The subjects were requested to search for a single
(non-existent) target letter. The co-ordination of eye and head movements
in patients with neglect resembled the pattern usually observed in healthy
subjects orienting to eccentric visual targets. They performed hypometric
head movements with additional shifts of eye-in-head position. Moreover,
like healthy subjects, the patients with neglect explored space with gaze,
with head and eye-in- head movements that were symmetrically distributed
around preferred orientations in space. However, in contrast to controls,
these centres of exploration were shifted towards the right. The average
horizontal position of gaze and of head movements lay right of the body's
mid- sagittal plane, the average eye-in-head position right of the head
midline. The preferred orientations were located far away from the
anatomical limits of horizontal gaze, head and eye-in-head movements. The
decrease of exploration towards more eccentric locations left and right of
these orientations thus could not be explained by anatomical restrictions.
The results argue against a model of neglect that proposes a lateral
gradient of attentional orienting towards the ipsilesional side. Exploring
the surroundings, the patients did not orient gaze, the head or the eyes in
the head towards the extreme ipsilesional side, nor even close to it. The
results favour a deviation model suggesting a shift of the whole frame for
exploratory behaviour towards the ipsilesional side. In addition to this
shift, we found a second component of altered visual exploration in
neglect. The patients' head and gaze movements exhibited a reduced
variability around the deviated centre of exploration. The variability was
not generally reduced but rather concerned specifically the horizontal
dimension. The latter was found even when the area of exploration was
paralleled between the groups, requiring the control subjects to search
only in that part of the letter array that the neglect patients had
explored spontaneously. Possible mechanisms, such as a disturbed ability to
update the spatial representation of visual targets or an altered neural
representation of space in the horizontal dimension, are discussed.
ARTICLES
Space exploration in neglect
Department of Neurology, University of Tubingen, Germany. Karnath@uni- tuebingen.de
CiteULike 
Connotea 
Del.icio.us What's this?
This article has been cited by other articles:
|
|
 |
|
  R. Ptak, A. Schnider, L. Golay, and R. Muri A non-spatial bias favouring fixated stimuli revealed in patients with spatial neglect Brain, December 1, 2007; 130(12): 3211 - 3222. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. Lamontagne, C. Paquette, and J. Fung Stroke Affects the Coordination of Gaze and Posture During Preplanned Turns While Walking Neurorehabil Neural Repair, January 1, 2007; 21(1): 62 - 67. [Abstract] [PDF]
|
|
|
|
 |
|
 A. Saj, J. Honore, C. Richard, Y. Coello, T. Bernati, and M. Rousseaux Where is the "straight ahead" in spatial neglect? Neurology, October 24, 2006; 67(8): 1500 - 1503. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
H.-O. Karnath and M. Dieterich Spatial neglect--a vestibular disorder? Brain, February 1, 2006; 129(2): 293 - 305. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. C. Snow and J. B. Mattingley Goal-driven selective attention in patients with right hemisphere lesions: how intact is the ipsilesional field? Brain, January 1, 2006; 129(1): 168 - 181. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 G. Thut, A. Nietzel, and A. Pascual-Leone Dorsal Posterior Parietal rTMS Affects Voluntary Orienting of Visuospatial Attention Cereb Cortex, May 1, 2005; 15(5): 628 - 638. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. Ellison, I. Schindler, L. L. Pattison, and A. D. Milner An exploration of the role of the superior temporal gyrus in visual search and spatial perception using TMS Brain, October 1, 2004; 127(10): 2307 - 2315. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. J Bailey, M J. Riddoch, and P. Crome Treatment of Visual Neglect in Elderly Patients With Stroke: A Single-Subject Series Using Either a Scanning and Cueing Strategy or a Left-Limb Activation Strategy Physical Therapy, August 1, 2002; 82(8): 782 - 797. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 B Fimm, R Zahn, M Mull, S Kemeny, F Buchwald, F Block, and M Schwarz Asymmetries of visual attention after circumscribed subcortical vascular lesions J. Neurol. Neurosurg. Psychiatry, November 1, 2001; 71(5): 652 - 657. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Niemeier and H.-O. Karnath Exploratory saccades show no direction-specific deficit in neglect Neurology, January 25, 2000; 54(2): 515 - 515. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. Ferber and H.-O. Karnath Parietal and occipital lobe contributions to perception of straight ahead orientation J. Neurol. Neurosurg. Psychiatry, November 1, 1999; 67(5): 572 - 578. [Abstract] [Full Text]
|
|