The Architect Who Lost the Ability to Imagine: The Cerebral Basis of Visual Imagery.

While the loss of mental imagery following brain lesions was first described more than a century ago, the key cerebral areas involved remain elusive. Here we report neuropsychological data from an architect (PL518) who lost his ability for visual imagery following a bilateral posterior cerebral artery (PCA) stroke. We compare his profile to three other patients with bilateral PCA stroke and another architect with a large PCA lesion confined to the right hemisphere. We also compare structural images of their lesions, aiming to delineate cerebral areas selectively lesioned in acquired aphantasia. When comparing the neuropsychological profile and structural magnetic resonance imaging (MRI) for the aphantasic architect PL518 to patients with either a comparable background (an architect) or bilateral PCA lesions, we find: (1) there is a large overlap of cognitive deficits between patients, with the very notable exception of aphantasia which only occurs in PL518, and (2) there is large overlap of the patients' lesions. The only areas of selective lesion in PL518 is a small patch in the left fusiform gyrus as well as part of the right lingual gyrus. We suggest that these areas, and perhaps in particular the region in the left fusiform gyrus, play an important role in the cerebral network involved in visual imagery

Visual imagery vividness appears to be independent of perceptual and memory precision

Visual mental imagery, or the ability to see with the mind’s eye, varies between individuals. The vividness of visual imagery ranges from people with aphantasia who experience no mental image at all, to those with hyperphantasia who experience very clear and vivid mental imagery. In the present study we investigated the possible connection between the vividness of visual mental imagery and precision of information retrieval from visual memory. We predicted that people experiencing weak or no mental imagery are poorer at retrieving information with great details from memory, such as the color of objects, than those experiencing strong and vivid mental imagery. This was tested in three experiments: a visual perception task, a visual working memory task, and a long-term visual memory task. The Vividness of Visual Imagery (VVIQ) questionnaire was used to assess imagery vividness. The perception task served as a control. A colored sample object and a grayscale test object were presented simultaneously. In the working memory and long-term memory tasks, a delay was added between the presentation of colored sample objects and grayscale test objects. Participants were asked to adjust the test object’s color until it matched that of the corresponding sample object. Our findings indicate no association between mental imagery vividness and memory precision. Possible explanations for this lack of an association are discussed