Evaluating the impact of fast-fMRI on dynamic functional connectivity in an event-based paradigm

Abstract

The human brain is known to contain several functional networks that interact dynamically. Therefore, it is desirable to analyze the temporal features of these networks by dynamic functional connectivity (dFC). A sliding window approach was used in an event-related fMRI (visual stimulation using checkerboards) to assess the impact of repetition time (TR) and window size on the temporal features of BOLD dFC. In addition, we also examined the spatial distribution of dFC and tested the feasibility of this approach for the analysis of interictal epileptiforme discharges. 15 healthy controls (visual stimulation paradigm) and three patients with epilepsy (EEG-fMRI) were measured with EPI-fMRI. We calculated the functional connectivity degree (FCD) by determining the total number of connections of a given voxel above a predefined threshold based on Pearson correlation. FCD could capture hemodynamic changes relative to stimulus onset in controls. A significant effect of TR and window size was observed on FCD estimates. At a conventional TR of 2.6 s, FCD values were marginal compared to FCD values using sub-seconds TRs achievable with multiband (MB) fMRI. Concerning window sizes, a specific maximum of FCD values (inverted u-shape behavior) was found for each TR, indicating a limit to the possible gain in FCD for increasing window size. In patients, a dynamic FCD change was found relative to the onset of epileptiform EEG patterns, which was compatible with their clinical semiology. Our findings indicate that dynamic FCD transients are better detectable with sub-second TR than conventional TR. This approach was capable of capturing neuronal connectivity across various regions of the brain, indicating a potential to study the temporal characteristics of interictal epileptiform discharges and seizures in epilepsy patients or other brain diseases with brief events.

Neuroimaging in Functional Neurological Disorder: State of the Field and Research Agenda

“…Although task fMRI has good spatial resolution (compared to PET and SPECT), temporal resolution is limited by the hemodynamic response, which is a concern when studying sub-second range cognitive-affective-perceptual processes ( Khanna et al, 2015 ). Task fMRI techniques in-development utilizing fast, sub-second approaches may soon overcome these issues ( Sahib et al, 2018 ).…”

Statistical Power or More Precise Insights into Neuro-Temporal Dynamics? Assessing the Benefits of Rapid Temporal Sampling in fMRI

“…connectivity changes within shorter and shorter windows (Sahib et al, 2018) or capturing network effects that are missed in static analyses of clinical populations (Zhang et al, 2018). Though resting state emerged as a methodology focused on slow (0.1 to 0.01Hz) oscillations for which typical 2s TRs are more than adequate, these findings suggest that there are substantial benefits and novel neuroscientific findings waiting to be uncovered with fast fMRI.…”

Modelling a Multiplex Brain Network by Local Transfer Entropy

“…Such data, in fact, have no well-defined time resolution, and spurious results can be easily obtained. Fast fMRI acquisition 70 would be a possible solution to the problem. -the resting state paradigm: In such an experimental condition subjects are not checked for a particular request, and less robust results can be obtained.…”