Abstract #3847

Modulation by cardiac and respiratory cycles of single-trial BOLD responses to visual stimulation using ultrafast fMRI at 7T

Francisco Moreira Azevedo¹, João Jorge^2,3, Wietske van der Zwaag⁴, and Patrícia Figueiredo¹

¹ISR-Lisboa/LARSyS and Department of Bioengineering, Instituto Superior Técnico, Universidade de Lisboa, Lisboa, Portugal, Lisbon, Portugal, ²Laboratory for Functional and Metabolic Imaging, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland, Lausanne, Switzerland, ³Systems Division, Swiss Center for Electronics and Microtechnology (CSEM), Neuchâtel, Switzerland, Lausanne, Switzerland, ⁴Spinoza Centre for Neuroimaging, Amsterdam, Netherlands, Amsterdam, Netherlands

The haemodynamic response to neuronal activity measured by BOLD-fMRI exhibits substantial trial-by-trial variability, but the underlying sources remain largely unknown. Here, we investigated whether single-trial BOLD responses were modulated by cardiac and respiratory cycles, by recording the BOLD responses to single trials of brief visual stimulation using an ultrafast acquisition (TR=0.4s) at ultrahighfield (7T). We found that, when binning trials according to the respiratory phase, the BOLD responses were more similar to each other when occurring up to 1sec following expiration. Our results suggest that trial-by-trial variability of BOLD responses may partly be explained by the respiratory cycle.

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