Method for functional MRI mapping of nonlinear response.
Kellman P, Gelderen P, de Zwart JA, Duyn JH.
Laboratory of Cardiac Energetics, NHLBI, National Institutes of Health,
Bethesda, MD 20892, USA. kellman@nih.gov
Nonlinear systems analysis combining blood oxygen level dependent (BOLD),
functional magnetic resonance imaging (fMRI) and m-sequence stimulation
paradigms are proposed as a new method for exploring neuronal responses
and interactions. Previous studies of electrical activity in the human
visual cortex have observed significant nonlinearities of task-induced
activity with temporal dynamics on a timescale of 10-20 ms. Despite the
confounding effect of the seconds-long hemodynamic response, it is
demonstrated that BOLD fMRI can be used to probe neuronal interactions
on a time scale of tens of ms. Visual activation experiments were
performed with various stimuli, and amplitude maps of first and second
order kernel coefficients were generated using correlation analysis.
Second order nonlinearities in BOLD fMRI were observed and attributed
to temporal contrast caused by transitions in the stimulus sequence.
In addition, the kernel maps showed significant differences between second
order nonlinearities of foveal and peripheral vision. By including a
reference experiment with a slightly modified stimulus presentation,
a distinction could be made between (fast) neuronal nonlinearities and
hemodynamic effects on the time scale of the seconds. The results
indicate that BOLD fMRI can probe fast neuronal nonlinearitiest.
PMID: 12781738 [PubMed - indexed for MEDLINE]