Seeing the forest but only half the trees?
In visuo-spatial neglect after right hemisphere damage, patients fail overtly to notice and respond to stimuli on the side of space contralateral to lesion. Nonetheless, these neglected stimuli may covertly influence their performance in other tasks less direct than overt detection or identification. We report here a new type of dissociation between two forms of conscious perceptual awareness in a patient with left neglect. J.R. was shown hierarchical drawings in which a larger (global) form, such as a geometric figure or an alphabetic letter, is composed of smaller (local) forms (dots, circles, or letters). She gave accurate verbal reports of the global structure of these stimuli (Navon figures), yet when required to cross out the smaller subfigures, she only cancelled those on the right of each global figure. Conscious perception of the whole does not automatically lead to visual awareness of all the parts thereof.
Marshall
J C
JC
University Department of Clinical Neurology, Radcliffe Infirmary, Oxford, UK.
Halligan
P W
PW
D005260:Female; D007839:Functional Laterality; D006429:Hemiplegia / Q000503:physiopathology*; D006801:Humans; D008875:Middle Aged; D009460:Neurologic Examination; D013028:Space Perception; D014787:Vision Tests