NEUROPHYSIOLOGICAL CORRELATES OF MENTAL-IMAGERY IN DIFFERENT SENSORY MODALITIES

Mental Imagery is supposed to be a basic phenomenon of conscious menta l operations, which is exerted in any sensory modality. The aim of the present study was to investigate neurophysiological correlates of men tal imagery in the visual the acoustic and tactile modality. For that purpose, word lists were created based on their power to evoke mental imagery in these modalities. Nine young healthy volunteers were includ ed. Words were presented on a computer screen with 3-s intervals. Evok ed electrical activity was recorded simultaneously with a 21-channel s ystem. After inspection for artifacts and off-line averaging, further analysis was performed in a time range of 250-450 ms, corresponding to the P300 component. Within this range, six topographically stable seg ments were found. A repeated measures ANOVA was significant for the le ft-right directions of the positive and of the negative centroid, but not for the anterior-posterior directions. The posterior centroid was most right-located in the visual sensory modality and most left-locate d for tactile imagery; in the acoustic modality it had a midline-posit ion. These differences in centroid locations during mental imagery in different sensory modalities can be explained by the underlying activi ty of different neural generator ensembles, possibly involving modalit y specific primary cortical areas. (C) 1997 Elsevier Science B.V.