Quantifying differences between passive and task-evoked intrinsic functional connectivity in a large-scale brain simulation

Abstract

12Establishing a connection between intrinsic and task--evoked brain activity is critical because it 13 would provide a way to map task--related brain regions in patients unable to comply with such 14 tasks. A crucial question within this realm is to what extent the execution of a cognitive task 15 affects the intrinsic activity of brain regions not involved in the task. Computational models can 16 be useful to answer this question because they allow us to distinguish task from non--task 17 neural elements while giving us the effects of task execution on non--task regions of interest at 18 the neuroimaging level. The quantification of those effects in a computational model would 19 represent a step towards elucidating the intrinsic versus task--evoked connection. Here we used 20 computational modeling and graph theoretical metrics to quantify changes in intrinsic 21 functional brain connectivity due to task execution. We used our Large--Scale Neural Modeling 22 framework to embed a computational model of visual short--term memory into an empirically 23 derived connectome. We simulated a neuroimaging study consisting of ten subjects performing 24 passive fixation (PF), passive viewing (PV) and delay match--to--sample (DMS) tasks. We used the 25 simulated BOLD fMRI time--series to calculate functional connectivity (FC) matrices and used 26 those matrices to compute several graph theoretical measures. After determining that the 27 simulated graph theoretical measures were largely consistent with experiments, we were able 28 to quantify the differences between the graph metrics of the PF condition and those of the PV 29 and DMS conditions. Thus, we show that we can use graph theoretical methods applied to 30 simulated brain networks to aid in the quantification of changes in intrinsic brain functional 31 connectivity during task execution. Our results represent a step towards establishing a 32 connection between intrinsic and task--related brain activity. 33for use under a CC0 license. This article is a US Government work. It is not subject to copyright under 17 USC 105 and is also made available (which was not peer-reviewed) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity.The copyright holder for this preprint . http://dx.doi.org/10.1101/250894 doi: bioRxiv preprint first posted online Jan. 20, 2018; 3 Author Summary 34 35Studies of resting--state conditions are popular in neuroimaging. Participants in resting--state 36 studies are instructed to fixate on a neutral image or to close their eyes. This type of study has 37 advantages over traditional task--based studies, including its ability to allow participation of 38 those with difficulties performing tasks. Further, a resting--state neuroimaging study reveals 39 intrinsic activity of participants' brains. However, task--related brain activity may change this 40 intrinsic activity, much as a stone thrown in a lake causes ripples on the water's surface. Can we 41 measure those activity changes? To answer tha...