Theta power in the EEG of humans during ongoing processing in a haptic object recognition task

Dynamic changes in spectral theta power (TP) in the EEO over frontal region s were reported previously during the processing of visually presented spat ial and verbal tasks [Cereb. Cortex, 7 (1997) 374-385]. Lower TP was found at the beginning compared to the end of processing. In order to test anothe r modality, we examined theta power during the exploration of haptic stimul i with different complexity. A linear correlation between theta power and m ean exploration time (as a measure of stimulus complexity) was found at the end of exploration but not at its beginning. These data are in line with o ur hypothesis since one could expect minimal load of working memory indepen dent of stimulus complexity at the beginning of exploration whereas working memory would have integrated the stimuli of differing complexity into a pe rceptual model at the end of exploration. (C) 2001 Elsevier Science B.V. Al l rights reserved.