title: Egocentric representations of space co-exist with allocentric representations: evidence from spatial neglect.
abstract: The brain transforms sensory input to motor coordinates to accommodate for changes of posture and gaze direction. Neurophysiological and neuropsychological evidence supports the existence of multiple representations of space. A debated issue regards whether objects that we see are encoded in egocentric frames only or also maintain an object-centered frame of reference. Previous clinical studies were unable to discriminate between these models as the stimuli used to determine object-based (allocentric) biases are contaminated by body-centered (egocentric) effects. To address this, we used stimuli where allocentric side was elicited by gestalt configuration rather than egocentric location. We then displayed these stimuli at different egocentric positions allowing us to independently measure the effects of allocentric position, egocentric position as well as their interaction. In a group of stroke patients with neglect we demonstrate that allocentric biases are modulated as a function of egocentric position. These findings help adjudicate between the different models of space representation, demonstrating that specific allocentric deficits not only exist but also often co-exist with egocentric biases.
authors.affiliation: Center of Neurology, Division of Neuropsychology, Hertie Institute of Clinical Brain Research, University of Tübingen, Tübingen, Germany.
authors.forename: Dongyun
authors.initials: D
authors.lastname: Li
authors.affiliation: Center of Neurology, Division of Neuropsychology, Hertie Institute of Clinical Brain Research, University of Tübingen, Tübingen, Germany; Department of Psychology, University of South Carolina, Columbia, SC, USA. Electronic address: Karnath@uni-tuebingen.de.
authors.forename: Hans-Otto
authors.initials: HO
authors.lastname: Karnath
authors.affiliation: Department of Psychology, University of South Carolina, Columbia, SC, USA.
authors.forename: Christopher
authors.initials: C
authors.lastname: Rorden
mesh_terms: D000368:Aged; D001288:Attention / Q000502:physiology*; D001921:Brain / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D009949:Orientation / Q000502:physiology; D010468:Perceptual Disorders / Q000209:etiology / Q000503:physiopathology*; D012649:Self Concept; D013028:Space Perception / Q000502:physiology*; D020521:Stroke / Q000150:complications / Q000503:physiopathology
keywords: Allocentric; Attention; Egocentric; Human; Reference frames; Space representation; Spatial neglect; Stroke