Nrurups)‘~.holuqla. Vol. 29. No Printed m Great Britain.

2. pp. 165-176,

HEMISPHERIC

1991. c

ACTIVATION VS SPATIO-MOTOR VISUAL NEGLECT: A CASE STUDY

PETER W. HALLIGAN,*

LILIANNE

MANNING?

and

JOHN

0028 3932.91 53.00+000 199 I Pergamon Preab

CUEING

plc

IN

C. MARSHALL$$

*Rivermead Rehabilitation Centre. Oxford, U.K.; tuniversidad Autonoma de Madrid, Spain; and $Neuropsychology Unit, University Department of Clinical Neurology. The Radcliffe Infirmary, Oxford OX2 6HE. U.K.

(Recriwd17April

1990; accepted

8 September

1990)

Abstract-We report a case of mild visuo-spatial neglect consequent upon right-hemisphere stroke. At the time of testing, the patient had a complete left visual field deficit but only a very slight left hemiparesis. Under conventional testing conditions, line bisection performed with the right hand showed more severe left neglect than when performed with the left hand. This pattern of performance could. however, be modified, both quantitatively and qualitatively, by changing the starting position of the patient’s hand when bisecting horizontal lines. The results suggest that spatio-motor cueing has a more profound effect upon task performance than does differential hemispheric activation per se. We also provide a demonstration that, in a normal subject, the starting position of the hand is likewise a crucial determinant of task performance. In this case, however, there is also an interaction between the hand (and hence hemisphere) deployed and the position of that hand in space.

INTRODUCTION MOST PATIENTS with left visuo-spatial neglect consequent upon right-hemisphere stroke have left hemiparesis. Testing for neglect in paradigms that require motor response is thus usually undertaken with only the right arm and hand. One obvious consequence is that it is impossible to assertain the respective contributions of the right and left hemispheres to task performance. The visuo-spatial deficit is presumably consequent upon right hemisphere damage, but the hand (right) that directs overt performance is controlled by the intact (left) hemisphere. There are, however, two studies that have explicitly compared left- and right-hand performance in those (relatively) rare neglect patients who do not manifest contralesional hemiparesis. JOANETTE et al. [9] employed a task in which pointing was required to whichever member of a lateral display of light-emitting diodes became illuminated on a particular trial. HALLIGAN and MARSHALL [7] employed two conventional neglect tests: cancellation of pre-specified targets in a two dimensional array of targets and distracters, and horizontal line bisection. The two studies agreed in finding a significant attenuation of (left) neglect when the left hand was used. The results of both studies were compatible with a theoretical account whereby use of the left hand increases the “level of activation” of the damaged right hemisphere [lo]. In the current paper, we report a replication of our finding [7] that the hand employed

lcorrespondence Clinical Neurology,

to be addressed to: Dr John C. Marshall, Neuropsychology Unit, University The Radcliffe Infirmary, Woodstock Road, Oxford OX2 6HE, U.K. 165

Department

of

166

PLTI K W. HALLIGAY, LILIANNE MASKING and JOHN C. MAKSHALL

modulates the expression of left neglect in line bisection (Experiment 1). We then consider an alternative theoretical account to the activation-hypothesis; namely, that the hand used acts as an external cue (either visual or somesthetic) determining the direction of (internal scan) approach to the midsagittal plane [4] (Experiments 2, 3 and 4).

EXPERIMENT

1

The prediction underlying the present experiment is that rightwards displacements of transections in line bisection with the right hand will be significantly decreased when the left hand is deployed. Subjects. D.F. 1s a 41 year old. right-handed man who, for a living, drove heavy articulated trucks. On 19 December 1989, he collapsed with loss of consciousness. When seen at Charing Cross Hospital, a diagnosis of intracranial bleed was made; risk factors included hypertension and pseudo von Willebrand’s disease. CT scan revealed a right temporo-parietal haematoma (and aneurysm was excluded on angiography). He then underwent a craniotomy with evacuation of the clot. D.F. made a slow improvement post-operatively with persistent complete left-sided hemianopia and inattention, in addition to left hemiplegia. He was referred to Rivermead Rehabilitation Centre on 12 February 1990, at the which time the hemianopia persisted (without diplopia or nystagmus), but the motor signs had resolved to a very mild left-sided weakness. Evaluated on the Beharioural inattention Test [I 81 on 12 February 1990, D.F. obtained a score of 129,/146,just outside the normal cut-off of 130/146. The current data were collected 10 weeks post-onset. Procedurr. Horizontal line bisection was performed with 1I lines (1 mm in width) that varied in length from 1 in. (25 mm) to 1I in. (279 mm) in steps of 1 in. Each black line was presented individually and centred both horizontally and vertically on a sheet of white A4 paper (298 x 208 mm). Each stimulus sheet was placed on the desk top and was always centred on the midsagittal plane of the patient’s head and trunk. All stimulus lengths were presented IOtimes in one session, with order of presentation pseudo-randomized across the lengths. D.F. bisected two sets of 110 lines (1I lengths x IO trials). one set with the right hand and one with the left. All stimuli were shown in free vjision. without restraint on head and eye movements. Knowledge of the results was not provided.

Results Transection accuracy was measured to the closest mm, and expressed as positive (+ ) for rightwards displacements and negative (- ) for leftwards displacements. The data are given in Table 1, where we display the mean and absolute displacements (and their respective standard deviations and ranges) for all lengths. The best-fitting regression equation for right-hand transections is -3.1885+ (0.088 17 x line length), with 93% of the variance accounted for. The comparable equation for the left hand is - 7.001 + (0.05436 x line length), with 54% of the variance accounted for. The difference between the two sets of readings is significant at P

Hemispheric activation vs spatio-motor cueing in visual neglect: a case study.

We report a case of mild visuo-spatial neglect consequent upon right-hemisphere stroke. At the time of testing, the patient had a complete left visual...
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