Abnormal binocular rivalry in unilateral neglect: evidence for a non-spatial mechanism of extinction.
Unilateral spatial neglect (USN) is considered to be an attention deficit, which is primarily related to space. Recent evidence points to the relevance of non-spatially lateralized mechanisms, with impairments found in rapid stimulus presentation conditions. Here we used the phenomenon of binocular rivalry (BR) to explore a non-spatial deficit over long temporal intervals. Six right-hemisphere damaged (RHD) patients with contralesional neglect (USN+), five RHD patients without neglect (USN-) and six normal controls were tested on the basic properties of BR induced by dichoptic presentation of orthogonal gratings at fixation. USN+ patients had much slower perceptual alternations compared to the USN- and normal groups (factors 2.5 and 4, respectively), and were much more sensitive to inter-ocular changes in relative stimulus contrast, which, unlike normals, altered both the suppression and dominance phases. Most notably, a small advantage of one monocular stimulus caused a long-term extinction of the other stimulus in the USN+ group alone. We explain the results in terms of impaired habituation to dominant and attended stimuli, which normally prevents a winner-takes-all behavior and extinction of the weak. This impaired habituation may in turn contribute to inappropriate environmental monitoring and attenuated novelty-seeking behavior.
Bonneh
Yoram S
YS
Department of Neurobiology, Brain Research, The Weizmann Institute of Science, Rehovot 76100, Israel. yoram.bonneh@weizmann.ac.il
Pavlovskaya
Marina
M
Ring
Haim
H
Soroker
Nachum
N
D000328:Adult; D000368:Aged; D005108:Extinction, Psychological / Q000502:physiology; D005260:Female; D005403:Fixation, Ocular; D007839:Functional Laterality / Q000502:physiology; D006185:Habituation, Psychophysiologic / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D010468:Perceptual Disorders / Q000503:physiopathology*; D010775:Photic Stimulation; D020521:Stroke / Q000503:physiopathology; D015348:Vision, Binocular / Q000502:physiology*