The pusher syndrome reverses the orienting bias caused by spatial neglect

Honoré Jacques; Arnaud Saj; Thérèse Bernati; Marc Rousseaux

doi:10.1016/j.neuropsychologia.2008.11.008

Neuropsychologia 47 (2009) 634–638

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Neuropsychologia

journal homepage: www.elsevier.com/locate/neuropsychologia

The pusher syndrome reverses the orienting bias caused by spatial neglect

Jacques Honoré

a,∗

, Arnaud Saj

b

, Thérèse Bernati

c

, Marc Rousseaux

c

a

UMR 8160, CNRS & University of Lille Nord-de-France, France

b

Laboratory for Behavioral Neurology and Imaging of Cognition, Department of Neuroscience, University Medical Center, Geneva, Switzerland

c

EA 2691 and Neurological Rehabilitation Department, Hospital Swynghedauw, CHRU, Lille, France

article info

Article history:

Received 13 February 2008

Received in revised form 3 October 2008

Accepted 7 November 2008

Available online 13 November 2008

Keywords:

Stroke

Subjective straight ahead

Pusher syndrome

Spatial neglect

abstract

Spatial neglect can be accompanied by a pusher syndrome (PS) which is characterized by a postural

deviation towards the contralesional side. In this study, the representation of the body orientation in the

horizontal plane was evaluated in neglect patients with and without PS. The participants had to align

a luminous rod with the straight ahead direction, a method allowing the measure of both horizontal

components of subjective straight ahead, i.e. lateral shift and yaw rotation. Eighteen patients with a

lesion of the right hemisphere were compared with ten healthy participants. Patients had neglect and

PS (P + N+; n = 3), neglect only (P − N+; n = 10), or neither neglect nor PS (P − N−; n = 5). P + N+ patients

showed a signiﬁcant leftward shift contrasting with the rightward shift of P − N+. No shift occurred in

patients without neglect and controls. No signiﬁcant yaw error was recorded in any groups. The original

result of this study was an inversion of the sign of the bias in neglect patients with PS. This could be

related to the postural disorders characterizing this syndrome, and which are opposite to those usually

observed in spatial neglect. Thus, these data suggest a link between disorders of spatial representations

and disorders of posture.

1. Introduction

Neglect patients frequently deviate towards the lesion side when

required to point in front of the middle of the body (Heilman,

Bowers, & Watson, 1983; Richard, Honoré, Bernati, & Rousseaux,

2004, for a review). This erroneous subjective straight ahead (SSA)

may result from a bias in an internal representation of body orienta-

tion essential for perception and action in extrapersonal space. This

egocentric reference is thought to be coded in a network includ-

ing the posterior parietal cortex (Jeannerod & Biguer, 1987; Ventre,

Flandrin, & Jeannerod, 1984), and its distortion could explain

behavioural and clinical disorders of neglect patients (Karnath,

Schenkel, & Fisher, 1991; Ventre et al., 1984). An argument for this

assumption is the temporary remission of neglect signs obtained

during sensory stimulations, especially vibratory and vestibular

(Karnath, 1994; Rossetti & Rode, 2002, for a review), which also

inﬂuence the representation of body orientation and induce illu-

sions of displacement in healthy subjects. In the initial version

of the hypothesis, the egocentred framework of reference under-

went a horizontal rotation in spatial neglect (Ventre et al., 1984).

This assumption seemed supported by Ferber and Karnath’s study

∗

Corresponding author at: UMR 8160, CNRS & University of Lille Nord-de-France,

CHU Hôpital Salengro, 59037 Lille Cedex, France. Tel.: +33 320446281;

fax: +33 320446732.

E-mail address: ja-honore@chru-lille.fr (J. Honoré).

(1999) on the visual SSA, whereas the data obtained by Vallar,

Guariglia, Nico, and Bisiach (1995) with an auditory method instead

argued for a bias in translation (see however Kerkhoff et al., 2006).

Two recent studies using a more direct measurement of the SSA

(Richard, Rousseaux, Saj, & Honoré, 2004; Saj et al., 2006) clearly

argue for an ipsilesional translation of the egocentric reference in

neglect patients.

Beside this bias affecting orientation in the horizontal dimen-

sion, spatial neglect is accompanied by postural disorders

(Pérennou, 2006). In a stabilometric study, left hemiparetic patients

with left neglect showed a centre of pressure deviated toward the

right (Rode, Tiliket, Charlopain, & Boisson, 1998). This deviation,

deﬁnitely more marked than (and of opposite direction to) that of

right hemiparetic patients, could be corrected by sensory (vestibu-

lar caloric stimulation, Rode et al., 1998) or sensorimotor (prismatic

adaptation, Tiliket et al., 2001) manipulations. According to these

authors, these manipulations, which also improved other neglect

signs, would reduce the distortion of a ‘postural space representa-

tion’. Since they appear biased conjointly in neglect and improved

by the same manipulations, the question of a possible link between

this ‘postural space representation’ and the egocentric reference

arises. A way of addressing the issue is to examine the deviation

of the SSA in neglect patients presenting with a particular postural

behaviour described as pusher syndrome (PS).

The study of PS is recent (Karnath, Ferber, & Dichgans, 2000),

although its clinical description is relatively old (Beevor, 1909). It

associates a severe imbalance, a tilt contralateral to the hemisphere

doi:10.1016/j.neuropsychologia.2008.11.008

The pusher syndrome reverses the orienting bias caused by spatial neglect

Honoré Jacques; Saj, Arnaud; Bernati, Thérèse; Rousseaux, Marc

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