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Functional Near Infrared Spectroscopy of the Sensory and Motor Brain Regions with Simultaneous Kinematic and EMG Monitoring During Motor Tasks
Published on: December 5, 2014
Detection of the early decrease in fMRI signal in the motor area
1Center for Magnetic Resonance Research, University of Minnesota, 2021 6th Street SE, Minneapolis, MN 55455, USA.
Abstract:
The initial decrease in BOLD signal at stimulus onset (i.e., the initial dip) has generated a great deal of interest because of its potential for providing more spatially specific mapping. Despite a number of experimental fMRI studies demonstrating its existence in the visual cortex, the initial dip has not been reported in other areas. The present work examined the initial dip in the motor area. Using a visually-guided finger-tapping paradigm, the dip was detected in both motor and visual areas simultaneously. The dip in the motor area was found to exhibit characteristics similar to those revealed by visual stimulation studies. The motor dip peaked approximately 2 sec after stimulus onset and reached an amplitude that was roughly 0.3 times of the positive amplitude. Furthermore, the dip in the motor area was more localized and less sensitive to large vessels, indicating an improvement in spatial specificity despite the relatively low spatial resolution used in this study. These data indicate that the initial dip is a general phenomenon that can be employed for more spatially specific functional mapping, although its full utility in humans remains to be further demonstrated. Magn Reson Med 45:184-190, 2001.
Insights
The initial dip in brain activity, a signal decrease at stimulus onset, was found in the motor cortex. This finding suggests the initial dip can improve spatial mapping accuracy in functional MRI studies.
Area of Science:
- Neuroimaging
- Functional Magnetic Resonance Imaging (fMRI)
- Neurophysiology
Background:
- The initial dip in Blood-Oxygen-Level-Dependent (BOLD) signal is a potential marker for high-resolution functional mapping.
- Previous studies have primarily identified the initial dip in the visual cortex.
- Its presence and characteristics in other brain regions, like the motor cortex, remain less explored.
Purpose of the Study:
- To investigate the presence and characteristics of the initial dip in the human motor cortex.
- To compare the motor cortex initial dip with that observed in the visual cortex.
- To assess the potential of the initial dip for improved spatial specificity in neuroimaging.
Main Methods:
- Utilized a visually-guided finger-tapping task in a functional MRI (fMRI) experiment.
- Simultaneously measured BOLD signal changes in both motor and visual cortices.
- Analyzed the timing, amplitude, and spatial localization of the initial dip response.
Main Results:
- The initial dip was successfully detected in the motor cortex during the finger-tapping task.
- Motor cortex dip characteristics (peak latency ~2s, amplitude ~0.3x positive amplitude) were similar to visual cortex findings.
- The motor dip demonstrated greater localization and reduced sensitivity to large blood vessels compared to typical fMRI signals.
Conclusions:
- The initial dip is a general neuroimaging phenomenon, not limited to the visual cortex.
- It exhibits properties suggesting enhanced spatial specificity for functional mapping.
- Further research is needed to fully establish the utility of the initial dip in human neuroimaging applications.
