NONSPATIAL ATTENTION DISORDERS IN PATIENTS WITH FRONTAL OR POSTERIOR BRAIN-DAMAGE

The few studies that have looked at attention in patients with brain d amage suggest a prominent role for the frontal lobe in nonspatial atte ntional control. However, the studies usually focus on one variety of attention and do not address the nature of the alteration of attention . In addition, the behavioural consequences of nonspatial attentional deficit remain unknown. The aim of this study was to evaluate the role of focal brain damage on divided and focused attention and the relati onship between attention disorders and behavioural changes. The study group consisted of patients with lesions of the prefrontal and posteri or cortices and control subjects. The assessment of attention used rea ction time tests that evaluated the ability to divide attention betwee n two sources (detection tests) and to focus attention on one source ( Go/No-Go Tests). The response retardation of the 'frontal' group becam e move pronounced as the number of sources to be monitored increased, suggesting the presence of a deficit of divided attention. Focused att ention deficit was demonstrated in the 'frontal' group by the more fre quent responses to irrelevant stimuli on Go/No-Go Tests. Both focused and divided attention deficits were prominent when the lesion included the left dorsolateral prefrontal cortex and the caudate nucleus. Sele ctive deficit of divided or focused attention was shown in a few patie nts. Finally the clinically assessed distractibility was related to di sorders of divided and focused attention. This study provides addition al evidence for the prominent role of the frontal lobe in nonspatial a ttention regulation and shows that it also operates in elementary perc eptuomotor processes. The relationship between distractibility and att ention indexes supports the idea that attention disorders mau have a f unctional counterpart that is clinically assessable. The demonstration of selective deficit of divided or focused attention suggests that no nspatial attention depends upon different mechanisms and that it is no t art undifferentiated, general purpose mechanism. Further studies add ressing the nature of the interactions between attentional mechanisms and other cognitive processes are required.