Pictorial pseudohallucinations with an "aperture effect" in a patient with quadrantanopia

Abstract

Visual pseudohallucinations are reported on in a patient with a left lower quadrantanopia due to a right parietotemporal surgical defect after tumour removal. Besides metamorphopsia, he hallucinated the lower half of human figures which were limited to within the borders of the anopic defect and appeared "amputated" at the hip with one forearm and hand appearing from above in correct anatomical position. The lower half of these human figures was perceived as correctly scaled in relation to anatomical and environmental coordinates and was recognised as unreal. These pseudohallucinations led to the concept of an "aperture effect" which alludes to the visibility through the anopic field defect of a segment of the contents of the visual association cortex. This supports the idea of a pictorial mode for representation of endogenously generated images in the visual association cortex.