Defective revisualization: dissociation between cognitive and imagistic thought case report and short review of the literature.

A 38-year-old shifted-sinistral patient displayed a definite deficit in visual imagery accompanied by defective dreaming capacity, loss of hypnagogic imagery, some defects in topographical memory, a mild unilateral right spatial neglect and mild difficulties in right-left orientation on the examiner's body. CT-scan and NMR studies showed evidence of an inborn hypoplasia of the right hemisphere and a stretched corpus callosum in its posterior and superior part. The vicarious compensatory action of the cognitive-verbal function of the defect of visual imagery was obvious. It is concluded that: there are various forms of visual imagery deficits: some are "pure" whereas in the great majority of reported cases the loss of visual imagery is associated to different forms of visual agnosia; the brain mechanisms underlying cognitive thought and imagistic thought could be obviously dissociated.