What exactly is extinguished in unilateral visual extinction? Neurophysiological evidence.

We propose a model of unilateral visual extinction following right hemisphere lesions based on competition between
contralesional and ipsilesional input to access a decision centre located in the left hemisphere. During bilateral presentations, the
contralesional signal is on average less likely to activate the decision centre than the ipsilesional signal. This is because an
intra-hemispheric lack of top-down attentional influences and an inter-hemispheric impairment of callosal transmission delay
and/or weaken the contralesional input. Here we provide behavioural as well as event-related potential evidence for both these
impairments. Finally, we argue that an essential prerequisite for contralesional extinction is the presence of a restricted general
attentional capacity which often follows large right hemisphere damage