The neural dynamics underlying unconstrained visuo-spatial and auditory mental imagery
Lizzy Blundon1, Yana Pertels1, Lawrence Ward1,2; 1University of British Columbia, 2Brain Research Centre
The purpose of this study was to investigate the neural dynamics underlying unconstrained mental imagery. We adapted for EEG an fMRI imagery paradigm frequently used to assess awareness in behaviourally unresponsive patients diagnosed with a Disorder of Consciousness (DOC). Neuro-typical participants were asked to alternately imagine themselves walking from room to room in their own home (visuo-spatial imagery) and to imagine themselves singing happy birthday (auditory imagery). Using independent component analysis and single dipole fitting, we inferred dominant neural generators of the EEG signal for each imagery task, including motor, temporal, frontal, and visual regions. Notably, a single dipole was localized to Right Posterior Parietal Cortex (RPPC) and Left Ventromedial Prefrontal Cortex (LVMPFC) in at least 90% of participants, suggesting that these regions represent stable neural generators of mental imagery across participants. Because imagery tasks were unconstrained (unguided), individual differences in local spectral power at, and in functional connectivity between, ROIs prevented meaningful group-level analyses. Individual participant differentiability between imagery tasks based on local spectral power across seven ROIs and four frequency bands, however, was easily demonstrable, particularly in theta and gamma frequency bands. We also found a significant correlation between differentiability in functional connectivity (phase locking value) between RPPC and LVMPFC and overall differentiability in functional connectivity between conditions in the gamma frequency band. We also discuss possible adaptations of this study design and differentiability index to the development of a method of detecting awareness in behaviourally unresponsive (DOC) patients.
Topic Area: ATTENTION: Multisensory