Elsevier

NeuroImage

Volume 13, Issue 1, January 2001, Pages 210-217
NeuroImage

Regular Article
Separating Processes within a Trial in Event-Related Functional MRI: I. The Method

https://doi.org/10.1006/nimg.2000.0710Get rights and content

Abstract

Many behavioral paradigms involve temporally overlapping sensory, cognitive, and motor components within a single trial. The complex interplay among these factors makes it desirable to separate the components of the total response without assumptions about shape of the underlying hemodynamic response. We present a method that does this. Four conditions were studied in four subjects to validate the method. Two conditions involved rapid event-related studies, one with a low-contrast (5%) flickering checkerboard and another with a high-contrast (95%) checkerboard. In the third condition, the same high-contrast checkerboard was presented with widely spaced trials. Finally, multicomponent trials were formed from temporally adjacent low-contrast and high-contrast stimuli. These trials were presented as a rapid event-related study. Low-contrast stimuli presented in isolation (partial trials) made it possible to uniquely estimate both the low-contrast and high-contrast responses. These estimated responses matched those measured in the first three conditions, thereby validating the method. Nonlinear interactions between adjacent low-contrast and high-contrast responses were shown to be significant but weak in two of the four subjects.

References (29)

  • R.L. Buckner et al.

    Detection of cortical activation during averaged single trials of a cognitive task using functional magnetic resonance imaging [see comments]

    Proc. Natl. Acad. Sci. USA

    (1996)
  • V.P. Clark et al.

    FMRI studies of face memory using random stimulus sequences

    NeuroImage

    (1997)
  • T.E. Conturo et al.

    Sensitivity optimization and experimental design in functional magnetic resonance imaging

    Soc. Neurosci. Abstr.

    (1996)
  • M. Corbetta et al.

    Voluntary orienting is dissociated from target detection in human posterior parietal cortex

    Nat. Neurosci.

    (2000)

    • Cited by (0)

    1

    To whom correspondence and reprint requests should be addressed at Washington University School of Medicine, Neuroimaging Laboratory, Campus Box 8225, St. Louis, MO 63110. Fax: 314-362-6110. E-mail: [email protected].

    View full text
    Copyright © 2001 Academic Press. All rights reserved.