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A comparison of hemodynamic and neural responses in cat visual cortex using complex stimuli
Christoph Kayser1, Mina Kim, Kamil Ugurbil
1Institute of Neuroinformatics, University & ETH Zurich, 8057, Switzerland. kayser@ini.phys.ethz.ch
Cerebral Cortex (New York, N.Y. : 1991)
|April 16, 2004
Summary
Functional magnetic resonance imaging (fMRI) blood-oxygen-level-dependent (BOLD) signals correlate with local field potentials (LFPs) in cat visual cortex, especially with natural stimuli. However, spiking activity shows poor BOLD signal concordance.
Area of Science:
- Neuroscience
- Systems Neuroscience
- Visual Neuroscience
Background:
- The blood-oxygen-level-dependent (BOLD) signal measured by functional magnetic resonance imaging (fMRI) is a widely used proxy for neural activity.
- However, the precise relationship between the BOLD signal and underlying electrophysiological measures, such as local field potentials (LFPs) and spiking activity, remains debated.
Purpose of the Study:
- To compare fMRI-BOLD responses with electrophysiological recordings (LFPs, aggregate high-frequency responses, and spiking activity) in the visual cortex of cats.
- To investigate how different stimulus types (artificial vs. natural) and frequency ranges affect the correlation between BOLD and electrophysiological signals.
Main Methods:
- Simultaneous recordings of fMRI-BOLD, LFPs, aggregate high-frequency responses (analog-Mua), and spiking activity in the visual cortex of anesthetized and alert cats.
- Comparison of signal similarities based on relative activation patterns elicited by artificial, complex, and natural stimuli.
- Quantification of concordance by counting recording sites with matching activation patterns.
Main Results:
- BOLD and LFP signals show good agreement, particularly between 20 and 50 Hz, with natural stimuli reducing frequency dependence.
- Aggregate high-frequency responses (analog-Mua) qualitatively mirrored LFP responses.
- Spiking activity exhibited low concordance with the BOLD signal, a dissociation most pronounced with natural stimuli.
Conclusions:
- The BOLD signal is more closely related to LFPs and aggregate high-frequency activity than to spiking activity in the visual cortex.
- Natural stimuli enhance the correlation between BOLD and LFPs, suggesting LFPs may be a better correlate of BOLD than previously thought.
- The dissociation between BOLD and spiking activity highlights the complexity of interpreting fMRI signals and the need to consider different neural components.