Open AccessFunctional decoupling of BOLD and gamma‐band amplitudes in human primary visual cortex
Author(s) -
Muthukumaraswamy Suresh D.,
Singh Krish D.
Publication year - 2009
Publication title -
human brain mapping
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.005
H-Index - 191
eISSN - 1097-0193
pISSN - 1065-9471
DOI - 10.1002/hbm.20644
Subject(s) - magnetoencephalography , visual cortex , neuroscience , stimulus (psychology) , physics , functional magnetic resonance imaging , nuclear magnetic resonance , amplitude , auditory cortex , psychology , electroencephalography , optics , psychotherapist
Although functional magnetic resonance imaging is an important tool for measuring brain activity, the hemodynamic blood oxygenation level dependent (BOLD) response is only an indirect measure of neuronal activity. Converging evidence obtained from simultaneous recording of hemodynamic and electrical measures suggest that the best correlate of the BOLD response in primary visual cortex is gamma‐band oscillations (∼40 Hz). Here, we examined the coupling between BOLD and gamma‐band amplitudes measured with magntoencephalography (MEG) in human primary visual cortex in 10 participants. In Experiment A, participants were exposed to grating stimuli at two contrast levels and two spatial frequencies and in Experiment B square and sine wave stimuli at two spatial frequencies. The amplitudes of both gamma‐band oscillations and BOLD showed tuning with stimulus contrast and stimulus type; however, gamma‐band oscillations showed a 300% increase across two spatial frequencies, whereas BOLD exhibited no change. This functional decoupling demonstrates that increased amplitude of gamma‐band oscillations as measured with MEG is not sufficient to drive the subsequent BOLD response. Hum Brain Mapp, 2009. © 2008 Wiley‐Liss, Inc.