Dissociation Between Awareness and Spatial Coding: Evidence from Unilateral Neglect
Dissociation between Awareness and Spatial Coding: Evidence from Unilateral Neglect Barbara Treccani1, Roberto Cubelli1, Roberta Sellaro1, Carlo Umiltà2, and Sergio Della Sala3 Downloaded from http://mitprc.silverchair.com/jocn/article-pdf/24/4/854/1777452/jocn_a_00185.pdf by MIT Libraries user on 17 May 2021 Abstract ■ Prevalent theories about consciousness propose a causal re- dissociate. A patient with left neglect, who was not aware of lation between lack of spatial coding and absence of conscious contralesional stimuli, was able to process their color and po- experience: The failure to code the position of an object is sition. However, in contrast to (ipsilesional) consciously per- assumed to prevent this object from entering consciousness. ceived stimuli, color and position of neglected stimuli were This is consistent with influential theories of unilateral neglect processed separately. We propose that individual object fea- following brain damage, according to which spatial coding of tures, including position, can be processed without attention neglected stimuli is defective, and this would keep their process- and consciousness and that conscious perception of an ob- ing at the nonconscious level. Contrary to this view, we report ject depends on the binding of its features into an integrated evidence showing that spatial coding and consciousness can percept. ■ INTRODUCTION the effects of processing of neglected stimuli on responses Awareness of a stimulus can be defined as the explicit to stimuli presented in the intact hemispace. Properties knowledge of its physical and semantic properties or sim- that can be processed implicitly include color and shape, ply of its existence. This knowledge can be demonstrated identity of alphanumerical symbols, and even the mean- by direct reports of the perception of the stimulus; for ing of words and pictures (Della Sala, van der Meulen, example, by naming it, categorizing it, or just by signaling Bestelmeyer, & Logie, 2010; Làdavas, Paladini, & Cubelli, its presence.
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