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Individual cases of crossed aphasia (aphasia after a right hemisphere lesion in a right-hander) have often been reported. A number of theories have been proposed as to the neuropsychological and/or nerobiological mechanisms that might underlie this phenomenon, but there is still disagreement about its language phenomenology and possible significance. We report 2 cases of crossed aphasia after stroke and review 34 cases from the literature with anatomical documentation of lesion site. Analysis of this material suggests that they represent at least two populations. There may be general conclusions concerning mechanisms of cerebral lateralization to be learned from the investigation of anomalous groups such as crossed aphasics.

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In the present exploratory investigation we report nine confabulatory patients of comparable age, education, and general level of intelligence in the acute epoch of recovery after rupture and clipping of ACoA aneurysms. Five of the nine cases had "spontaneous" confabulation, severe anterograde amnesia, markedly poor attentional and executive functions, and denial of illness. These patients all had multiple lesions that involved basal forebrain, ventral frontal lobe, and striatum. The other four patients manifested only "momentary" or "provoked" confabulations. These patients also had severe anterograde amnesia but showed relatively mild deficits in executive functions. These patients had lesions restricted to the basal forebrain except for one who had additional orbital frontal damage. Analysis of these two groups of confabulatory patients suggests that there is a common profile of deficits and anatomic foundation associated with confabulation; "spontaneous" confabulation appears to require extensive, simultaneous disruption of medial basal forebrain and frontal cognitive systems resulting in profound executive and memory deficits, whereas more limited lesions to the basal forebrain or orbital frontal cortex will result in "transient" or "provoked" confabulatory responses and a more restricted profile of cognitive deficits.