Dissociation between awareness and spatial coding: evidence from unilateral neglect.
Prevalent theories about consciousness propose a causal relation between lack of spatial coding and absence of conscious experience: The failure to code the position of an object is assumed to prevent this object from entering consciousness. This is consistent with influential theories of unilateral neglect following brain damage, according to which spatial coding of neglected stimuli is defective, and this would keep their processing at the nonconscious level. Contrary to this view, we report evidence showing that spatial coding and consciousness can dissociate. A patient with left neglect, who was not aware of contralesional stimuli, was able to process their color and position. However, in contrast to (ipsilesional) consciously perceived stimuli, color and position of neglected stimuli were processed separately. We propose that individual object features, including position, can be processed without attention and consciousness and that conscious perception of an object depends on the binding of its features into an integrated percept.
Dipartimento di Scienze della Cognizione e della Formazione, Università degli Studi di Trento, Corso Bettini 31, 38068 Rovereto, Trento, Italy. barbara.treccani@unitn.it
Barbara
B
Treccani
Roberto
R
Cubelli
Roberta
R
Sellaro
Carlo
C
Umiltà
Sergio
S
Della Sala
D000704:Analysis of Variance; D001364:Awareness; D001930:Brain Injuries / Q000150:complications; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D007600:Judgment; D008279:Magnetic Resonance Imaging; D008875:Middle Aged; D009483:Neuropsychological Tests; D010468:Perceptual Disorders / Q000473:pathology / Q000503:physiopathology*; D010775:Photic Stimulation; D011930:Reaction Time / Q000502:physiology; D017603:Signal Detection, Psychological / Q000502:physiology*; D013028:Space Perception / Q000502:physiology*; D014057:Tomography, X-Ray Computed