Spontaneous back-pain alters randomness in functional connections in large scale brain networks

Abstract

14We use randomness as a measure to assess the impact of evoked pain on brain networks. 15Randomness is defined here as the intrinsic correlations that exist between different brain regions 16 when the brain is in a task-free state. We use fMRI data of three brain states in a set of back pain 17 patients monitored over a period of 6 months. We find that randomness in the task-free state closely 18 follows the predictions of Gaussian orthogonal ensemble of random matrices. However, the 19 randomness decreases when the brain is engaged in attending to painful inputs in patients suffering 20 with early stages of back pain. A persistence of this pattern is observed in the patients that develop 21 chronic back pain, while the patients who recover from pain after 6 months, the randomness reverts 22 back to a normal level. 23 Author Summary 25 26Back-pain is a salient percept known to affect brain regions. We studied random correlations in 27 brain networks using random matrix theory. The brain networks were generated by fMRI scans 28 obtained from a longitudinal back-pain study. Without modelling the neuronal interactions, we 29 studied universal and subject-independent properties of brain networks in resting state and two 30 distinct task states. Specifically, we hypothesized that relative to the resting state, random 31 correlations would decrease when the brain is engaged in a task and found that the random 32 correlations showed a maximum decrease when the brain is engaged in detecting back pain than 33 performing a visual task. 34 35 suggest that chronic pain alters the nervous system so that the brain perceives persistent pain due back pain (SP); and, c) A control state in which they are rating changes in length of a visual bar 132 (SV). 133 134 MRI data acquisition 135 136 157 Anatomical parcellation and construction of correlation matrix 158 159