Neglect and extinction: within and between sensory modalities.

PURPOSE The interest in human conscious awareness has increasingly propelled the study of neglect, the most striking occurrence of an acquired lack of conscious experience of space. Neglect syndromes commonly arise after unilateral brain damage that spares primary sensory areas nonetheless leading to a lack of conscious stimulus perception. Because of the central role of vision in our everyday life and motor behaviour, most research on neglect has been carried out in the visual domain. Here, we suggest that a comprehensive perspective on neglect should examine in parallel evidence from all sensory modalities. METHODS We critically reviewed relevant literature on neglect within and between sensory modalities. RESULTS A number of studies have investigated manifestations of neglect in the tactile and auditory modalities, as well as in the chemical senses, supporting the idea that neglect can arise in various sensory modalities, either separately or concurrently. Moreover, studies on extinction (i.e., failure to report the contralesional stimulus only when this is delivered together with a concurrent one in the ipsilesional side), a deficit to some extent related to neglect, showed strong interactions between sensory modality for the conscious perception of stimuli and representation of space. CONCLUSIONS Examining neglect and extinction by taking into account evidence from all sensory modalities in parallel can provide deeper comprehension of the neglect syndrome mechanisms and possibly more effective multi-sensory based rehabilitation approaches.