Some mechanisms responsible for the vividness of mental imagery : suppressor, closer, and other functions

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In this paper, studies concerned with the vividness of imagery are reviewed to elucidate the characteristics of vivid imagery, the mechanisms responsible for the vividness of imagery, and the factors that affect those mechanisms. From this review, the following characteristics of imagery can be identified: (a) imagery vividness can be defined by the amount of information in the image, and more perceptual information is in vivid than in dim imagery; (b) information structure in long-term memory (LTM) consists of meaning, affective information, perceptual information, and motoric information, and those components are interconnected; (c) imagery is generated in the image construction stages using perceptual information; (d) a mechanism called the Suppressor controls the channel capacity, or the flow of perceptual information from LTM to the image construction stages; (e) the degree of this suppression is affected by the emotional value of imagery computed on the basis of affective information stored in LTM; (f) motoric information in LTM also influences vividness by acting on the image construction stages. Given these characteristics, we propose a model of imagery processes in order to explain how a certain level of vividness is established for the visual mental image. Finally, some neural correlates of the model are described based on results from our latest fMRI studies, and problems remaining for further development of the model are discussed.