title: BOLD responses in human auditory cortex are more closely related to transient MEG responses than to sustained ones.
abstract: Blood oxygen level dependent-functional magnetic resonance imaging (BOLD-fMRI) and magnetoencephalographic (MEG) signals are both coupled to postsynaptic potentials, although their relationship is incompletely understood. Here, the wide range of BOLD-fMRI and MEG responses produced by auditory cortex was exploited to better understand the BOLD-fMRI/MEG relationship. Measurements of BOLD and MEG responses were made in the same subjects using the same stimuli for both modalities. The stimuli, 24-s sequences of click trains, had duty cycles of 2.5, 25, 72, and 100%. For the 2.5% sequence, the BOLD response was elevated throughout the sequence, whereas for 100%, it peaked after sequence onset and offset and showed a diminished elevation in between. On the finer timescale of MEG, responses at 2.5% consisted of a complex of transients, including N(1)m, to each click train of the sequence, whereas for 100% the only transients occurred at sequence onset and offset between which there was a sustained elevation in the MEG signal (a sustained field). A model that separately estimated the contributions of transient and sustained MEG signals to the BOLD response best fit BOLD measurements when the transient contribution was weighted 8- to 10-fold more than the sustained one. The findings suggest that BOLD responses in the auditory cortex are tightly coupled to the neural activity underlying transient, not sustained, MEG signals.
authors.affiliation: Department of Neurology, Ruprecht-Karls-Universität Heidelberg, 69120 Heidelberg, Germany. Alexander.Gutschalk@med.uni.heidelberg.de
authors.forename: Alexander
authors.initials: A
authors.lastname: Gutschalk
authors.forename: Matti S
authors.initials: MS
authors.lastname: Hämäläinen
authors.forename: Jennifer R
authors.initials: JR
authors.lastname: Melcher
mesh_terms: D000328:Adult; D001303:Auditory Cortex / Q000502:physiology*; D001931:Brain Mapping; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D015225:Magnetoencephalography; D008297:Male; D008954:Models, Biological; D010100:Oxygen / Q000097:blood*; D011930:Reaction Time; D055366:Synaptic Potentials / Q000502:physiology*; D013997:Time Factors
chemical_list: D010100:Oxygen