Laterality of mental imagery generation and operation: tests with brain-damaged patients and normal adults.

The relationships between hemispheric function and components of the imagery process were examined in patients with unilateral right and left brain damage and in intact adult subjects. In the image generation condition, subjects were required to mentally generate Katakana letters corresponding to Hiragana letters displayed on a CRT. The results for the intact adults suggested a left hemisphere superiority, but the unilaterally brain-damaged subjects showed no hemispheric difference in this task. In the imagery operation task (transformation or lateral translation), subjects were asked to find a genuine Kanji among distractors (pseudo-Kanji) that were constructed from two Kanji radicals (themselves real Kanji) that were either displayed in reverse order or shifted apart. The results for both intact adults and patients with unilateral brain damage suggest the superiority of the right hemisphere.