Brain Advance Access published online on September 22, 2009
Brain, doi:10.1093/brain/awp227
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Neuronal correlates of functional magnetic resonance imaging in human temporal cortex
1 Department of Neurological Surgery, University of Washington, Seattle, WA 98195, USA 2 Department of Psychology, University of Washington, Seattle, WA 98195, USA 3 Department of Radiology, University of Washington, Seattle, WA 98195, USA 4 Department of Biological Structure, University of Washington, Seattle, WA 98195, USA 5 Department of Physiology and Biophysics, University of Washington, Seattle, WA 98195, USA
Correspondence to:
George A. Ojemann, Department of Neurological Surgery, Campus Box 356470, University of Washington, 1959 NE Pacific Street, Seattle, WA 98195, USA E-mail: gojemann{at}u.washington.edu
The relationship between changes in functional magnetic resonance imaging and neuronal activity remains controversial. Data collected during awake neurosurgical procedures for the treatment of epilepsy provided a rare opportunity to examine this relationship in human temporal association cortex. We obtained functional magnetic resonance imaging blood oxygen dependent signals, single neuronal activity and local field potentials from 8 to 300 Hz at 13 temporal cortical sites, from nine subjects, during paired associate learning and control measures. The relation between the functional magnetic resonance imaging signal and the electrophysiologic parameters was assessed in two ways: colocalization between significant changes in these signals on the same paired associate-control comparisons and multiple linear regressions of the electrophysiologic measures on the functional magnetic resonance imaging signal, across all tasks. Significant colocalization was present between increased functional magnetic resonance imaging signals and increased local field potentials power in the 50–250 Hz range. Local field potentials power greater than 100 Hz was also a significant regressor for the functional magnetic resonance imaging signal, establishing this local field potentials frequency range as a neuronal correlate of the functional magnetic resonance imaging signal. There was a trend for a relation between power in some low frequency local field potentials frequencies and the functional magnetic resonance imaging signal, for 8–15 Hz increases in the colocalization analysis and 16–23 Hz in the multiple linear regression analysis. Neither analysis provided evidence for an independent relation to frequency of single neuron activity.
Key Words: fMRI; single neuron activity; local field potentials; paired-associative learning; temporal cortex
Abbreviations: BOLD, blood oxygen level dependent; ECoG, electrocorticogram; fMRI, functional magnetic resonance imaging; ID, word identification; LFP, local field potential; PA, paired associate; ROI, region of interest
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Received February 4, 2009. Revised July 15, 2009. Accepted July 19, 2009.
*Present address: Department of Psychology, Center for Mind and Brain, University of California Davis, Davis CA 95618, USA