Nonlinearity of FMRI responses in human auditory cortex

Authors

  • Thomas M. Talavage,

    Corresponding author
    1. School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana
    2. Department of Biomedical Engineering, Purdue University, West Lafayette, Indiana
    3. Massachusetts Institute of Technology–Harvard Division of Health Sciences and Technology, Cambridge, Massachusetts
    4. Massachusetts General Hospital Nuclear Magnetic Resonance Center, Charlestown, Massachusetts
    • School of Electrical and Computer Engineering, 465 Northwestern Avenue, Purdue University, West Lafayette, IN 47907-2035
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  • Whitney B. Edmister

    1. Massachusetts Institute of Technology–Harvard Division of Health Sciences and Technology, Cambridge, Massachusetts
    2. Massachusetts General Hospital Nuclear Magnetic Resonance Center, Charlestown, Massachusetts
    3. Department of Radiology, Mayo Clinic, Rochester, Minnesota
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Abstract

An investigation was made into the nature of the nonlinearity observed in auditory functional magnetic resonance imaging (fMRI) experiments associated with increases in total duration of acoustic imaging noise [e.g., Edmister et al., 1999; Shah et al., 1999]. A two-stimulus, four-condition paradigm was used to evaluate four acoustic conditions involving: (1) the presence or absence of a desired broadband music stimulus; and (2) two possible durations of trains of acoustic noise associated with image acquisition. Responses observed while increasing the duration of acoustic imaging noise were consistent with previous work (Talavage et al. [1999]: Hum Brain Mapp7:79–88) but the response to combined stimulation did not exhibit variation as a function of the acoustic imaging noise duration. These results suggest that spectral overlap of the stimuli produced colocalized responses that did not add linearly. This conclusion has implications for conducting both blocked and rapid-presentation event-related auditory fMRI experiments. The cortical activity induced by the stimulus may not reflect the activation, in spatial extent or magnitude of signal change, occurring in the absence of other acoustic noise. Hum. Brain Mapping 22:216–228, 2004. © 2004 Wiley-Liss, Inc.

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