Faculty Bibliography

Language was studied in four patients with bilateral cerebral infarctions. Bilateral destruction of the third frontal gyri did not necessarily produce the severely limited language output characteristic of global or severe Broca aphasia; for Broca aphasia to occur, there must be extensive frontoparietal damage in the dominant cerebral hemisphere. Thus, the marked recovery of language after lesions limited to the dominant third frontal gyrus is mediated by adjacent areas of the dominant hemisphere, and not by the nondominant third frontal gyrus. The nondominant hemisphere nevertheless has a limited capacity to produce oral speech after extensive damage to the dominant hemisphere and may play an appreciable, although still subsidiary, role in normal articulation. The central gyri and rolandic operculum may be more essential than the third frontal gyri for well-articulated speech

A man with a tumor in the right superior parietal lobule had difficulty reaching for visualized objects. There were no significant deficits in visual sensation, visual attention, somatosensory function, elementary motility, praxis, or visuospatial performance. If allowed to visually fixate the target before reaching, he misreached only with his left arm and only when he was not allowed to observe the reaching limb. If he was required to maintain central visual fixation while reaching into his peripheral visual fields, his left arm misreached into both visual hemifields but his right arm misreached only into the left visual hemifield. These results demonstrate abnormalities, referable to both the contralateral arm and the contralateral visual field, that can neither be reduced to elementary disturbances of visual or somatosensory function nor to an elementary disturbance of motility. This pattern of misreaching has not been previously reported in human subjects or in experimental animals, but this may be attributable to differences of methodology. The misreaching observed in this patient may correspond to loss of posterior parietal neurons serving a supramodal integrative function