Takafumi Sasaoka, Hiroaki Mizuhara, and Toshio Inui


Dynamic Parieto-premotor Network for Mental Image Transformation
Revealed by Simultaneous 
EEG and fMRI Measurement


Journal of Cognitive Neuroscience





Previous studies have suggested that the posterior parietal cortices and
premotor areas are 
involved in mental image transformation. However, it
remains unknown whether these regions 
really cooperate to realize mental
image transformation. In this study, simultaneous EEG and 
fMRI were
performed to clarify the spatio-temporal properties of neural networks
engaged in
 mental image transformation. We adopted a modified version of
the mental clock task used 
by Sack et al. [Sack, A. T., Camprodon, J.
A., Pascual-Leone, A., & Goebel, R. The dynamics 
of interhemispheric
compensatory processes in mental imagery. Science, 308, 702-704, 2005; 
 Sack, A. T., Sperling, J. M., Prvulovic, D., Formisano, E., Goebel, R.,
Di Salle, F., et al. 
Tracking the mind’s image in the brain II:
Transcranial magnetic stimulation reveals parietal 
asymmetry in
visuospatial imagery. Neuron, 35, 195-204, 2002]. In the modified mental
task, participants mentally rotated clock hands from the position
initially presented at a learned 
speed for various durations.
Subsequently, they matched the position to the visually presented 
hands. During mental rotation of the clock hands, we observed
significant beta EEG 
suppression with respect to the amount of mental
rotation at the right parietal electrode. 
The beta EEG suppression
accompanied activity in the bilateral parietal cortices and left 
 premotor cortex, representing a dynamic cortical network for mental
image transformation. 
These results suggest that motor signals from the
premotor area were utilized for mental image 
transformation in the
parietal areas and for updating the imagined clock hands represented in 
 the right posterior parietal cortex.

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