title: Subliminal galvanic-vestibular stimulation influences ego- and object-centred components of visual neglect.
abstract: Neglect patients show contralesional deficits in egocentric and object-centred visuospatial tasks. The extent to which these different phenomena are modulated by sensory stimulation remains to be clarified. Subliminal galvanic vestibular stimulation (GVS) induces imperceptible, polarity-specific changes in the cortical vestibular systems without the unpleasant side effects (nystagmus, vertigo) induced by caloric vestibular stimulation. While previous studies showed vestibular stimulation effects on egocentric spatial neglect phenomena, such effects were rarely demonstrated in object-centred neglect. Here, we applied bipolar subsensory GVS over the mastoids (mean intensity: 0.7mA) to investigate its influence on egocentric (digit cancellation, text copying), object-centred (copy of symmetrical figures), or both (line bisection) components of visual neglect in 24 patients with unilateral right hemisphere stroke. Patients were assigned to two patient groups (impaired vs. normal in the respective task) on the basis of cut-off scores derived from the literature or from normal controls. Both groups performed all tasks under three experimental conditions carried out on three separate days: (a) sham/baseline GVS where no electric current was applied, (b) left cathodal/right anodal (CL/AR) GVS and (c) left anodal/right cathodal (AL/CR) GVS, for a period of 20min per session. CL/AR GVS significantly improved line bisection and text copying whereas AL/CR GVS significantly ameliorated figure copying and digit cancellation. These GVS effects were selectively observed in the impaired- but not in the unimpaired patient group. In conclusion, subliminal GVS modulates ego- and object-centred components of visual neglect rapidly. Implications for neurorehabilitation are discussed.
authors.affiliation: Clinical Neuropsychology Unit & Outpatient Department, Saarland University, Saarbruecken, Germany.
authors.forename: Karin
authors.initials: K
authors.lastname: Oppenländer
authors.affiliation: Schön Clinic Bad Aibling, Germany.
authors.forename: Ingo
authors.initials: I
authors.lastname: Keller
authors.affiliation: Department of Educational Science, Saarland University, Saarbrücken, Germany.
authors.forename: Julia
authors.initials: J
authors.lastname: Karbach
authors.affiliation: University of Hull, Department of Psychology, UK.
authors.forename: Igor
authors.initials: I
authors.lastname: Schindler
authors.affiliation: Clinical Neuropsychology Unit & Outpatient Department, Saarland University, Saarbruecken, Germany.
authors.forename: Georg
authors.initials: G
authors.lastname: Kerkhoff
authors.affiliation: Clinical Neuropsychology Unit & Outpatient Department, Saarland University, Saarbruecken, Germany. Electronic address: s.reinhart@mx.uni-saarland.de.
authors.forename: Stefan
authors.initials: S
authors.lastname: Reinhart
mesh_terms: D000223:Adaptation, Psychological / Q000502:physiology; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D016022:Case-Control Studies; D004558:Electric Stimulation / Q000379:methods*; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010468:Perceptual Disorders / Q000503:physiopathology* / Q000628:therapy*; D011597:Psychomotor Performance / Q000502:physiology*; D013028:Space Perception / Q000502:physiology; D014722:Vestibule, Labyrinth / Q000502:physiology*
keywords: Attention; Egocentric; Galvanic vestibular stimulation; Neglect; Object-centred; Rehabilitation