Head centered but no body centered modulation of horizontal space misrepresentation in neglect and in hemianopia

Visual neglect is doubly dissociated from impairments due to damage of retinotopic representations of space in primary visual pathways (i.e. hemianopia) and is thought to depend on the disruption of extra-retinotopic multimodal representations. Anisometric representation of horizontal space with relative underestimation of contralesional object size or between-object distances and corresponding relative overestimation of equivalent ipsilesional ones, was recently hypothesised to be a relevant component of neglect Here we show that space misrepresentation in neglect patients depends on the concomitant damage of retinotopic and extraretinotopic information at a stage of visuospatial processing where the gain of eye-centered retinotopic and head-centered representation of space is not modulated by mechanisms underlying the body centered coding of space. The absence of any modulation from eye or neck proprioception on space misrepresentation in N+H+ confirms that the total unilateral loss of retinotopic representations of space predisposes neglect patients to the highest probability of suffering the most severe form of horizontal space misperception.