Neglect for low luminance contrast stimuli but not for high colour contrast stimuli: a behavioural and electrophysiological case study.

We describe a patient with a right hemisphere lesion involving the frontal lobe, the post-central gyrus and the superior parietal lobule. Behavioural testing demonstrated severe left unilateral neglect to low luminance contrast stimuli, but not to high colour contrast stimuli. Evoked potentials to low contrast luminance gratings presented in the left hemifield were not reliable. However, equiluminant coloured gratings presented in the same hemifield evoked reliable electrophysiological responses, although longer in latency than those evoked in the right hemifield. These findings suggest that the patient has severe damage of the high contrast sensitivity magnocellular pathway in the right hemisphere, with minor involvement of the parvocellular pathway.