Neglect and extinction often present simultaneously in patients. When looking at neglect, studies have demonstrated that there is more to the spatial nature than mere primary sensory loss. Proposals of this kind have become increasingly frequent in recent years but attentional accounts for neglect are not universally popular. We can think of one primary component of neglect as involving inattention and that extinction is by no means the whole story for neglect. Extinction encapsulates a critical general principle that applies for most aspects of neglect, namely that the patient's spatial deficit is most apparent in competitive situations, where information towards the good ipsilesional side comes to dominate information that would otherwise be acknowledged towards the contralesional side. This may relate to the attentional limitation seen in neurologically healthy people. We cannot become aware of multiple targets all at once, even if our sensory systems have transduced them. This is seen in patients with extinction, who are able to detect a single target in any location, with a deficit only for multiple concurrent targets. Therefore, extinction can be regarded as a pathological, spatially specific exaggeration of the normal difficulty in distributing attention to multiple targets so we can predict that it should be reduced if the two competing events could be grouped together. Several recent findings from right-parietal patients with left extinction confirm this prediction, suggesting that grouping mechanisms may still operate despite the pathological spatial bias of the patient to influence whether a particular stimulus will reach the patient's awareness. Thus extinction is reduced when the concurrent target events can be linked into a single subjective object, becoming allies rather than competitors in the bid to attract attention. Furthermore, the extent of residual processing extinct stimuli can vary from one patient to another, depending on the exact extent of their lesion. The examples of residual unconscious processing so far all concern the visual modality although evidence is starting to emerge concerning similar effects for extinguished tactile and auditory stimuli.
