It is conventional to distinguish five types of attention: vigilance, sustained attention, and alertness, forming the intensity axis, and focused http://www.selleckchem.com/products/Everolimus(RAD001).html attention and divided attention, forming the selectivity axis of attention.64 The different types of attention can be demonstrated to be distinct and independent of one another, and subserved by a number of different brain structures distributed extensively over the prefrontal, anterior cingulate, and posterior parietal areas

of both hemispheric cortices. Within either hemisphere, and between hemispheres, the system of control processes is complex. However, some broad consistent differences Inhibitors,research,lifescience,medical in hemisphere specialization are striking. Vigilance and sustained attention are grossly impaired Inhibitors,research,lifescience,medical in subjects with right-hemisphere lesions,65-67 especially right frontal lesions,68 and by contrast, are preserved in left-hemisphere lesions.69 Right-hemisphere lesions also lead to perceptuomotor slowing, a sign of diminished alertness, associated with lapses of attention, 70-76 though in

one study slowing was associated with lesions in the left dorsolateral prefrontal cortex.77 Studies in both normal subjects78,79 and split-brain subjects80 corroborate the role of the right hemisphere in the “intensity” aspects of attention, confirmed by neuroimaging.81,82 The other main axis of attention is selectivity (focused and divided Inhibitors,research,lifescience,medical attention). Although selective attention may be bilateral,83 deficits in focused attention are more severe with left-hemisphere injury,76,85 typically in the left caudate,77 or left anterior cingulate.84 Normal subjects show a left-hemisphere preference for choice reactions,86,87 and imaging suggests focused attention is associated with activity Inhibitors,research,lifescience,medical in the left orbitofrontal cortex and basal ganglia.88 By contrast, lesions in the right inferior parietal lobule cause the most

serious impairment of global attention.89 As regards divided attention, the evidence is less conclusive. While some studies suggest that both left and right hemispheres are involved,77 there appears Inhibitors,research,lifescience,medical to be a clear primary role for the right hemisphere, especially the right dorsolateral prefrontal cortex.88,90 In summary, there is evidence of left-hemisphere dominance for local, narrowly focussed attention and righthemisphere dominance for broad, sustained, global, and flexible attention. 65,66,91-95 The scope of the through right hemisphere’s world is broad.96-97 Subjects with a right-hemisphere lesion start with the pieces and put them together to get the overall picture, whereas those with a left-hemisphere lesion prefer a global approach.98-102 Right-hemisphere damaged subjects seem unable to adjust the breadth of the “spotlight” of their attention and suffer ‘an excessive and more or less permanent narrowing of their attentional window.