Right-brain-damaged patients showing unilateral neglect underwent a specifically devised line-bisection task that allowed uncoupling of the direction of visual attention from that of hand movement. This made it possible to isolate and separately assess perceptual and premotor factors of the disorder. Comparison of experimental and radiologic data suggested that premotor factors were more pronounced in patients with lesions involving the frontal lobes than in patients with lesions confined to postrolandic areas. The technique employed is compatible with bedside examination and provides data useful for standard assessment of neglect symptomatology for both clinical and experimental purposes.

The effects of vestibular stimulation upon somatosensory deficits or tactile extinction contralateral to a hemispheric lesion were investigated in 20 right brain-damaged patients and 11 left brain-damaged patients. After stimulation, right brain-damaged patients showed a temporary partial recovery from left hemianaesthesia or extinction. Conversely, right somatosensory deficits associated with left brain damage were virtually unaffected by vestibular stimulation. Temporary recovery from somatosensory deficits was independent of the presence of visuo-spatial hemineglect. The suggestion is made that somatosensory deficits and extinction produced by right brain damage have an important non-sensory or perceptual component, that may be positively affected by vestibular stimulation. The mechanisms whereby this treatment may ameliorate somatosensory deficits may involve the restoration of the normal correspondence between somatotopic and egocentric representations of the body.

The anatomical correlates of tactile and visual extinction with double simultaneous stimulation were investigated in a series of 159 patients with right brain damage caused by stroke. Forty six patients showed extinction (22 tactile, 14 visual, 10 tactile and visual). Over 50% of the patients with extinction had deep lesions, which were found in about 25% of the patients with visuospatial neglect not associated with extinction. In the patients with extinction and cortico-subcortical damage the paraventricular occipital white matter and the dorsolateral frontal cortex were most often involved. By contrast, when neglect was also present, the lesions clustered in the inferior parietal lobule. These data suggest, from an anatomical perspective, that partly different neural mechanisms may underlie neglect and extinction. The comparatively high frequency of subcortical lesions involving the ascending pathways may be a neural correlate of a sensory component of extinction.