Generation of skeletal and multipart mental visual images in the cerebral hemispheres: a study in normal subjects

In a series of three experiments the hemispheric lateralization of structures generating the details and the holistic properties of mental images was investigated in three different samples of normal right-handed subjects. In the first experiment the left hemisphere was faster in discriminating at an imagery level whether animals had short or long tails. No hemispheric dominance was found when the imagery task required the discrimination of the holistic features of objects and a decision of whether they were taller than wider, or vice versa. In the second experiment no hemispheric dominance was found when the same tasks had to be performed perceptually. In the third experiment no hemispheric dominance was found in the speed of lexical recognition of the names that in the first experiment elicited the generation of multipart and skeletal mental images, although the left hemisphere was generally more accurate. These findings provide support to the hypothesis advanced by Kosslyn that multipart mental images are generated by the left hemisphere and skeletal images by both hemispheres. Results are discussed both in terms of Kosslyn's computational theory of imagery generation and in terms of theories advanced by other authors.