Dissociation between egocentric and allocentric visuospatial and tactile neglect in acute stroke

Abstract

Previous investigations provide evidence for distinction between egocentric (viewer-centered) and allocentric (stimulus- or object-centered) hemispatial neglect. However, it has not been determined whether this dissociation is modality-independent or modality-specific. We identify the incidence of egocentric and allocentric neglect in visual and tactile modalities, as well as the frequency of their co-occurrences in each modality. One-hundred patients with acute, right supratentorial ischemic stroke were administered tests for egocentric and allocentric hemispatial neglect in visual (n=98) and tactile (n=58) modalities. The visual test consisted of a page of 30 circles; 10 with no gap, 10 with a gap on the right side, and 10 with a gap on the left. Patients were asked to circle all complete circles and cross out all circles with gaps. A tactile version consisted of the same stimulus types presented as raised circles. Patients were asked to explore the board of circles with their dominant hand and report whether each circle had a gap. To determine the presence of egocentric or allocentric neglect, each test was analyzed for a significantly higher number of errors on the contralesional versus ipsilesional side of the page/board, or of the stimulus, using the Chi square analysis. On the visual test, 17 patients exhibited egocentric neglect; four exhibited allocentric neglect; and only two exhibited both. In the tactile modality, 19 exhibited egocentric neglect; one exhibited allocentric neglect; and none demonstrated both. Only four patients showed egocentric neglect on both visual and tactile tests. We found one patient with bilateral lesions who showed left egocentric visual neglect and right allocentric tactile neglect. These data provide strong evidence that egocentric and allocentric neglect are distinct syndromes that often dissociate and likely reflect damage to different brain areas. They also show that selective egocentric or allocentric neglect can occur in visual or tactile modalities.

Object-based Neglect Varies with Egocentric Position

“…It was speculated whether this obvious distinction between egocentric and object-based inattention separates neglect into body-and object-based forms (e.g., Marsh & Hillis, 2008;Hillis et al, 2005;Walker, 1995;Marshall & Halligan, 1993). In line with this notion, several anatomical studies carried out in neglect patients reported evidence for separate neural structures involved in egocentric versus object-based visual information processing (Medina et al, 2009;Grimsen, Hildebrandt, & Fahle, 2008;Rorden, Fruhmann Berger, & Karnath, 2006;Hillis et al, 2005;Binder, Marshall, Lazar, Benjamin, & Mohr, 1992).…”

“…Egocentric and object-based mechanisms also seem to be involved in the disturbed spatial orienting behavior observed in stroke patients suffering from right hemisphere damage and spatial neglect. The characteristic failure of neglect patients to explore the side contralateral to the lesion has been described to occur not only with respect to egocentric reference frames but also relative to object-based coordinates (Savazzi, Mancini, Veronesi, & Posteraro, 2009;Marsh & Hillis, 2008;Hillis et al, 2005;Behrmann & Geng, 2002;Ota, Fujii, Suzuki, Fukatsu, & Yamadori, 2001;Behrmann & Tipper, 1994, 1999Karnath, Niemeier, & Dichgans, 1998;Pavlovskaya, Glass, Soroker, Blum, & Groswasser, 1997;Tipper & Behrmann, 1996;Behrmann & Moscovitch, 1994;Driver, Baylis, Goodrich, & Rafal, 1994;Karnath, 1994;Arguin & Bub, 1993;Driver, Baylis, & Rafal, 1992;Young, Hellawell, & Welch, 1992;Driver & Halligan, 1991;Gainotti, Messerli, & Tissot, 1972).…”

Perfil Dos Indivíduos Com Alterações Funcionais Características De Heminegligência Após Avc

“…Este dado encontrado no estudo atual, corrobora com o estudo de Marsh et al 22 ., 2008. Os autores argumentam que podem existir diferentes regiões cerebrais com papéis específicos na computação de modalidades visuoespaciais 22 . Apenas o tálamo foi acometido em indivíduos de ambos os grupos no estudo atual.…”

“…Apenas o tálamo foi acometido em indivíduos de ambos os grupos no estudo atual. Em estudo realizado com heminegligentes com a região talâmica acometida, os autores afirmam que lesões no tálamo estão fortemente associadas à heminegligência, principalmente no núcleo pulvinar, que está envolvido na exploração e orientação da atenção no espaço 22 .…”

Neurophysiological Markers of Language Recovery in Subacute Stroke

“…The second stage of recovery is the subacute phase and this lasts until six months post-stroke. Recovery during this period is less rapid and consists of neural reorganisation, specifically, the establishment of alternative networks, synaptic remodelling and axonal sprouting (Lazar & Antoniello, 2008;Marsh & Hillis, 2008). The last stage of recovery is the chronic phase and once this stage is reached, recovery will have slowed considerably.…”