Temporal Autocorrelation of Noise for BOLD and IRON fMRI
Mandeville J, Greve D, Leite F, Vanduffel W
A A Martinos Center for Biomedical Imaging
IRON contrast has much better functional sensitivity than BOLD contrast, both in block designs and in ER designs using randomization of ISIs and/or event types. This work examines temporal noise using BOLD and IRON contrasts. We observe temporal correlations within a first order autocorrelation model, whose dominant source is likely to be signal dependent physiological noise. The BOLD noise correlation is twice that of IRON, but the AR noise scaling has relatively little effect on differences between BOLD and IRON sensitivities. The spatial distribution differs between the methods, probably reflecting different underlying physiology.