Visual mental imagery of a letter of alphabet: A functional magnetic resonance imaging study

A functional resonance imaging (fMRI) study was performed to investigate what areas are activated, especially whether primary visual area is included, when subjects generate a visual mental imagery of a letter of alphabet. Subjects were instructed to generate a visual mental image of a letter of alphabet sequentially after they hear an auditory signal and not to generate any visual mental images after they hear another auditory signal. The paradigm was constructed to be as simple as possible for the subjects to easily generate visual mental imagery and to eliminate any other contribution of neuronal activity such as discrimination or motor executions. All subjects showed statistically significant activation in pre-motor area, supplementary motor area, posterior parietal area. Three of six subjects showed activation in primary visual area while rest of the subjects who did not showed activation in this area showed activation in fusiform area. These results suggest that there might be two types of visual mental imagery conditions, one is using primary visual area and the other is using fusiform area.