Abstract
Patients with hemispatial neglect exhibit a myriad of profound deficits. A hallmark of this syndrome is the patients' absence of awareness of items located in their contralesional space. Many studies, however, have demonstrated that neglect patients exhibit some level of processing of these neglected items. It has been suggested that unconscious processing of neglected information may manifest as a fast denial. This theory of fast denial proposes that neglected stimuli are detected in the same way as non-neglected stimuli, but without overt awareness. We evaluated the fast denial theory by conducting two separate visual search task experiments, each differing by the duration of stimulus presentation. Specifically, in Experiment 1 each stimulus remained in the participants' visual field until a response was made. In Experiment 2 each stimulus was presented for only a brief duration. We further evaluated the fast denial theory by comparing verbal to motor task responses in each experiment. Overall, our results from both experiments and tasks showed no evidence for the presence of implicit knowledge of neglected stimuli. Instead, patients with neglect responded the same when they neglected stimuli as when they correctly reported stimulus absence. These findings thus cast doubt on the concept of the fast denial theory and its consequent implications for non-conscious processing. Importantly, our study demonstrated that the only behavior affected was during conscious detection of ipsilesional stimuli. Specifically, patients were slower to detect stimuli in Experiment 1 compared to Experiment 2, suggesting a duration effect occurred during conscious processing of information. Additionally, reaction time and accuracy were similar when reporting verbally versus motorically. These results provide new insights into the perceptual deficits associated with neglect and further support other work that falsifies the fast denial account of non-conscious processing in hemispatial visual neglect.
Highlights
Hemispatial visual neglect is a syndrome of attention deficit that frequently occurs after unilateral brain damage, such as from stroke
Conclusions our study did not elicit overt unconscious processing behavior, it cannot be definitively concluded that this type of processing did not take place
Behavioral evidence of unconscious processing has converged with neuroimaging results showing cortical activation to neglected information [34]
Summary
Hemispatial visual neglect is a syndrome of attention deficit that frequently occurs after unilateral brain damage, such as from stroke. People with neglect may lack explicit awareness of information in their contralesional space, it is well established that unconscious processing of this visual field can take place This phenomenon has been repeatedly demonstrated across different modalities and behavioral functions [3,4,5,6,7,8,9,10,11,12,13,14]. When asked to choose the house she would prefer to live in, she consistently chose the non-burning house while claiming that both were identical Even though such examples like this are common, the mechanistic underpinnings behind unconscious processing of neglected information are still under debate
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
