MEG Detects Alpha-Power Modulations in Pulvinar

Abstract

Event Abstract Back to Event MEG Detects Alpha-Power Modulations in Pulvinar Yohan Attal1*, Jérôme Yelnik2, Eric Bardinet1, Marie Chupin1 and Sylvain Baillet3 1 Massachusetts General Hospital, United States 2 Hopital Pitie-Salpetriere, INSERM U679, France 3 Medical College of Wisconsin, United States Objectives: Neuroimaging evidence regarding the functional organization of subcortical nuclei such as pulvinar is rather scarce compared to cortical structures [1]. Further, MEG is often believed to be insensitive to deeper brain structures. We have recently developed a global-brain MEG model that encompasses structural and electrophysiological properties of cortical and subcortical structures for source analysis [2]. Here we use this model to map the brain structures involved in the modulation of brain activity in the alpha range in 6 subjects. Methods and Results: Individual T1-weighted MRI axial scans (1x1x1.5mm voxel size) from 6 healthy subjects were processed to extract cortical and subcortical tessellations. Neocortical and hippocampus surface tessellations were obtained using the automatic pipeline available in the BrainVISA free software solutions [3]. Central grey nuclei were segmented from the individual MR volumes using a deformable atlas approach [4]. Elementary current dipoles (ECD) were placed at the surface of the cortex and hippocampus and along regular volumic grids within subcortical nuclei. The MEG session consisted of a block-designed “eyes open - eyes closed” paradigm (CTF Omega whole-head 151-channel MEG system). Each block lasted for 30 s. Data were band-pass filtered within the alpha band that was determined on an individual basis after inspection of the power spectra of each subject. Distributed source imaging was performed using BrainStorm. Significant ( , non-parametric permutation tests [5]) modulations of MEG source amplitudes were detected by contrasting the eyes open vs. eyes closed conditions. These amplitude modulations were detected in the dorsal and lateral parietal cortex and in the pulvinar thalamic regions. These areas are densely interconnected and generally assumed to be involved in the generation and modulation of alpha brain waves. Conclusions: The global source model has been evaluated on experimental MEG data on a classical eyes-open/eyes-closed paradigm. Modulations of activities were detected in parieto-occipital cortical regions and in the pulvinar part of the thalamus. These results indicate that complete, realistic modelling of MEG source distribution can help detect activation in deeper brain structures that were thought to be invisible to MEG.