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The correlation between blood oxygenation level-dependent signal strength and latency

✍ Scribed by Karsten Müller; Jane Neumann; Gabriele Lohmann; Toralf Mildner; D. Yves von Cramon

Book ID
102907723
Publisher
John Wiley and Sons
Year
2005
Tongue
English
Weight
946 KB
Volume
21
Category
Article
ISSN
1053-1807

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✦ Synopsis

Abstract

Purpose

To investigate the relationship between signal strength and latency of the blood oxygenation level‐dependent (BOLD) signal.

Materials and Methods

Several correlation analyses were performed on data obtained in a functional magnetic resonance imaging (fMRI) experiment, where subjects were presented with a simple visual stimulus. The BOLD signal strength was correlated with both the phase shift of the spectral density matrix and time‐to‐peak calculated from trial‐averaged time courses. Correlation coefficients were calculated for visual stimuli of 2, 6, and 15 seconds in duration.

Results

Analyzing all functional runs for the same subject separately, i.e., including for each run all significantly activated voxels, we observed that correlations between phase shift and signal strength, as well as between time‐to‐peak and signal strength, decreased with increasing stimulus length. However, when analyses were restricted to voxels found activated in all functional runs, we observed similar correlations between BOLD signal strength and latency in all runs, independent of the length of stimulation. This result was again obtained for both latency measures: the spectral density phase shift and time‐to‐peak.

Conclusion

For both latency measures, phase shift and time‐to‐peak, a high correlation between BOLD signal strength and latency was observed. We have shown that this correlation is independent of the length of visual stimulation. Thus, the correlation between BOLD signal strength and latency seems to be an inherent property of the BOLD response that is independent of the length of stimulation and can be observed using different methods for determining signal latency. J. Magn. Reson. Imaging 2005;21:489–494. © 2005 Wiley‐Liss, Inc.

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