Mapping transient hyperventilation induced alterations with estimates of the multi-scale dynamics of BOLD signal.

Abstract

Temporal blood oxygen level dependent (BOLD) contrast signals in functional MRI during rest may be characterized by power spectral distribution (PSD) trends of the form 1/fα. Trends with 1/f characteristics comprise fractal properties with repeating oscillation patterns in multiple time scales. Estimates of the fractal properties enable the quantification of phenomena that may otherwise be difficult to measure, such as transient, non-linear changes. In this study it was hypothesized that the fractal metrics of 1/f BOLD signal trends can map changes related to dynamic, multi-scale alterations in cerebral blood flow (CBF) after a transient hyperventilation challenge. Twenty-three normal adults were imaged in a resting-state before and after hyperventilation. Different variables (1/f trend constant α, fractal dimension Df, and, Hurst exponent H) characterizing the trends were measured from BOLD signals. The results show that fractal metrics of the BOLD signal follow the fractional Gaussian noise model, even during the dynamic CBF change that follows hyperventilation. The most dominant effect on the fractal metrics was detected in grey matter, in line with previous hyperventilation vaso-reactivity studies. The α was able to differentiate also blood vessels from grey matter changes. Df was most sensitive to grey matter. H correlated with default mode network areas before hyperventilation but this pattern vanished after hyperventilation due to a global increase in H. In the future, resting-state fMRI combined with fractal metrics of the BOLD signal may be used for analyzing multi-scale alterations of cerebral blood flow.

Fractal analysis of spontaneous fluctuations of the BOLD signal in rat brain

“…In support of this suggestion a recent study by Kiviniemi et al . shows that hypocapnia-induced reduction of blood flow actually increases the fractal parameter of the BOLD signal (Kiviniemi et al, 2009). …”

Age-related differences in functional nodes of the brain cortex - a high model order group ICA study

“…Two neuroradiologists (H.L and V.K) using the same criteria as before, depicted the thresholded IC maps corresponding to the previously depicted RSNs sources (Kiviniemi et al, 2009). Some 30 artifactual (residual motion, mal-alignment, and other noise sources) were discarded initially.…”

Time–frequency dynamics of the sum of intra- and extracerebral hemodynamic functional connectivity during resting-state and respiratory challenges assessed by multimodal functional near-infrared spectroscopy

“…Hyperventilation and breath-holding are two short and non-invasive challenge conditions to study cerebral hemodynamics in response to hypo-and hypercapnia, respectively [Kastrup et al, 1998;Kastrup et al, 1999a;Kiviniemi et al, 2009]. Hyperventilation and breath-holding can also induce affective responses, in particular in individuals with a high degree of anxious sensitivity to respiratory symptoms, such as during the experience of spontaneous panic attacks in patients with anxiety disorders [Eke and McNally, 1996;Maddock and Carter, 1991;Rapee et al, 1992;Rassovsky et al, 2000;Roth et al, 1998].…”