Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
6039532 | NeuroImage | 2008 | 9 Pages |
Abstract
In this study, the spatial and temporal frequency tuning characteristics of the MEG gamma (40-60Â Hz) rhythm and the BOLD response in primary visual cortex were measured and compared. In an identical MEG/fMRI paradigm, 10 participants viewed reversing square wave gratings at 2 spatial frequencies [0.5 and 3Â cycles per degree (cpd)] reversing at 5 temporal frequencies (0, 1 6, 10, 15Â Hz). Three-dimensional images of MEG source power were generated with synthetic aperture magnetometry (SAM) and showed a high degree of spatial correspondence with BOLD responses in primary visual cortex with a mean spatial separation of 6.5Â mm, but the two modalities showed different tuning characteristics. The gamma rhythm showed a clear increase in induced power for the high spatial frequency stimulus while BOLD showed no difference in activity for the two spatial frequencies used. Both imaging modalities showed a general increase of activity with temporal frequency, however, BOLD plateaued around 6-10Â Hz while the MEG generally increased with a dip exhibited at 6Â Hz. These results demonstrate that the two modalities may show activation in similar spatial locations but that the functional pattern of these activations may differ in a complex manner, suggesting that they may be tuned to different aspects of neuronal activity.
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Authors
Suresh D. Muthukumaraswamy, Krish D. Singh,