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Modulation of spontaneous fMRI activity in human visual cortex by behavioral state
Marta Bianciardi1, Masaki Fukunaga, Peter van Gelderen
1Advanced MRI Section, Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892-1065, USA. bianciardim@mail.nih.gov
Neuroimage
|November 26, 2008
Summary
Spontaneous brain activity measured by functional MRI (fMRI) decreases with visual fixation. This suggests neuronal activity underlies fMRI signals, impacting how brain activations are interpreted during tasks.
Area of Science:
- Neuroimaging
- Cognitive Neuroscience
Background:
- Spontaneous functional MRI (fMRI) activity reveals brain network connectivity.
- The neuronal basis and behavioral modulation of spontaneous fMRI activity are not fully understood.
Purpose of the Study:
- To investigate how behavioral states modulate spontaneous fMRI activity in occipital brain regions.
- To determine if spontaneous fMRI signals reflect neuronal activity.
Main Methods:
- Utilized 7 Tesla BOLD fMRI to measure spontaneous activity under different behavioral conditions (eyes closed, eyes open with fixation, fixation with visual stimulation).
- Isolated spontaneous activity from evoked activity and physiological noise (cardiac, respiratory).
Main Results:
- Spontaneous activity in visual areas significantly decreased in amplitude (44%) and coherence (25%) during visual fixation compared to eyes-closed rest.
- No further modulation of spontaneous activity was observed with added visual stimulation.
- Spontaneous activity linearly superimposed with evoked activity during visual processing.
Conclusions:
- Behavioral modulation of spontaneous fMRI activity supports its neuronal origin.
- Spontaneous activity influences task-related brain activation, necessitating its consideration in fMRI study interpretations.
