RT Journal Article
SR Electronic
T1 Large-scale multivariate activation states of the human brain
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 068221
DO 10.1101/068221
A1 Richard H. Chen
A1 Takuya Ito
A1 Kaustubh R. Kulkarni
A1 Michael W. Cole
YR 2016
UL http://biorxiv.org/content/early/2016/08/06/068221.abstract
AB Much of our lives are spent in unconstrained rest states, yet cognitive brain processes are primarily investigated experimentally using task-constrained states. It may be possible to utilize the insights gained from experimental control of task processes as reference points for investigating unconstrained rest. To facilitate comparison of rest and task functional MRI (fMRI) data we focused on activation amplitude patterns, commonly used for task but not rest analyses. During rest, we identified spontaneous changes in temporally extended whole-brain activation pattern states. This revealed a hierarchical organization of rest states. The top consisted of two competing states consistent with previously identified “task-positive” and “task-negative” activation patterns. These states were composed of a variety of more specific states that repeated over time and across individuals. In contrast to the classic view that rest consists of only task-negative states, task-positive states were present over 40% of the time while individuals “rested.” This suggests individuals conduct extensive task-oriented mental activity during rest. Consistent with this interpretation, classifier decoding of rest brain states based on thousands of task fMRI studies identified a variety of matched active tasks. Further, an analysis of task data revealed a similar hierarchical structure of brain states. Together these results suggest brain activation dynamics form a general hierarchy across both task and rest, with a small number of dominant general states reflecting basic modes of brain function along with a variety of specific states likely reflecting the rich variety of cognitive states experienced in everyday life.Significance Statement Neuroimaging has revolutionized understanding of human brain function, yet most brain activation studies have used instructed tasks, limiting understanding of the full range of human brain activation states. When unconstrained (“rest”) states have been investigated, activation of a “default mode” network involved in self-reflective cognition has been detected. This suggests rest periods consist of self-reflection, yet everyday experience suggests task-focused thoughts – such as attending to the environment and efforts to solve the problems of everyday life – also occur during “rest”. We confirmed this, identifying the broad organizational structure of spontaneous brain states in humans. We found that rest consists of approximately 60% self-reflection and 40% task-focused events, with multiple cognitively meaningful sub-states identified using activity pattern decoding.