Hemispheric contribution to categorical and coordinate representational processes: A study on brain-damaged patients

According to Kosslyn, two types of spatial relations can be used to arrange parts in mental imagery, i.e., categorical spatial relations and coordinate spatial relations, which are processed respectively by the left and right hemispheres. To investigate this possible hemispheric specialization in the imagery domain, we tested 34 left or right brain-damaged patients using both a categorical and a coordinate mental imagery task. The results show that left brain-damaged patients were selectively impaired on processing categorical representations, while right brain-damaged patients were more impaired on the processing the coordinate ones, regardless of the presence of visuo-spatial neglect. The present study partly support Kosslyn's theory and, despite data reported in previous studies of brain-damaged patients, it also supports the hypothesis of a possible bilateral neural representation of mental imagery, with the two hemispheres taking part in this process in different ways.