1. Default mode network 2015.5.20 Jinhui Yoon

3. Contents Introduction Some history Precursors of resting state fMRI Resting state fMRI Research examples Summary

4. Introduction “Resting state” defined.. In the context of experimentation, “rest” is an operational definition referring to a constant condition without imposed stimuli or other behaviorally salient events.

5. Introduction The objective of resting state experiment is to capture the statistical properties of endogenously generated (intrinsic) neural activity. The objective of event-related studies is to measure evoked or induced responses.

6. Introduction Resting state statistical properties of endogenous activity are modulated by the state of the eyes, by concurrent performance of semantic and motor tasks and by concurrent sensory stimulation. Similar modulations have also been observed immediately following task performance. These effects provide clues regarding the physiological significance of resting state activity.

7. Introduction Unstrained cognition alone does NOT account for the greatest part of intrinsic activity although it undoubtedly contributes a small increment. Imposed tasks evoke responses that are modest in magnitude in comparison to intrinsic activity. During slow wave sleep, and even during surgical anesthesia, resting state activity persists.

8. Some history Thomas Henry Huxley addressed the significance of patterned nervous activity. (1884) George Bishop observed cyclic changes of excitability in the visual cortex of the rabbit during stimulation of the optic nerve. (1933) - He understood that the brain’s response to stimuli is modulated by fluctuating endogenous activity.

9. Some history More recent, fMRI-based study showed that percepts as well as actions are modulated by ongoing activity. (review, 2010) The same perspective underlies studying the cognitive significance of trial-to-trial variability in evoked responses. (Arieli 1996, Debener 2007)

10. Some history Metabolic investigations of the resting state also date to the years following the WWII. Kety and Schmidt introduced first quantitative measurement of human whole-brain blood flow and metabolism (1948). Sokoloff measured whole-brain blood flow and oxygen consumption of resting state and during task, but there was no change. (1955)

11. Some history These observations were extended to regional measurement with PET in the 1980s. It was shown that locally induced changes in blood flow were accompanied by proportionate increase in glucose consumption but not oxygen utilization. The local change was too small to have been detected by methods designed to measure the energy consumption of the brain as a whole.

12. Some history The first formal characterization of task-induced activity decreases from a resting state derived from a large meta-analysis of published PET data from our group. (Shulman, 1997)

13. Summary of some history “The resting state is not truly a resting state at all.”

14. Precursors of resting state fMRI Spontaneous fluctuations in regional oxygen availability have been actively investigated since the 1950s. Brain redox state were synchronous in homologous regions of both hemisphere. (Vern 1998)

15. Precursors of resting state fMRI Spontaneous waves of blood flow and oxygen availability were related to patterns of electrical activity in experimental animals. (Golanov 1994)

16. Resting state fMRI It had been known since the advent of fMRI that the BOLD signal exhibits slow (<0.1Hz) spontaneous fluctuations although this phenomenon was initially regarded as noise. The neural origin of fluctuation of BOLD signal was established by Bharat Biswal (1995).

17. Resting state fMRI Map of the resting state neural connectivity for the PCC.

18. Research examples - neuroscience He et al., 2008 Showing a correspondence between the topography of BOLD resting state networks and the correlation structure of ECoG recorded resting state slow cortical potentials.

19. Research exmaples - neuroscience

20. Research examples - neuroscience Resting state networks are present in anesthetized monkeys. (Vincent 2007)

21. Research examples - neuroscience DMN may be present as well in the mouse

22. Research examples - neuroscience Concerning role of this functional system is thought to be include moral reasoning, model building, and prospection. (Buckner 2008, Schacter 2007) If, as appears increasingly likely, all mammals have a DMN, currently prevailing theories concerning the cognitive operations represented in the DMN will have to be revised.

23. Research examples - neuroscience Is functional connectivity tied with anatomical connectivity? Johnston 2008 Inter-hemispheric functional connectivity is effectively obliterated in the acute period (days) after complete section of the corpus callosum. Uddin 2008 Interhemispheric functional connectivity may be present decades after total corpus callosotomy.

24. Research examples - pathophysiology Many neurological and psychiatric entities give rise to resting state functional connectivity changes. Pizoli 2011 Dramatic improvement in functional connectivity architecture following anterior 2/3 corpus callosomy in a child with epileptic encephalopathy.

25. Research examples – Development and aging Infants – Smyser 2010 Children – Fair 2007,2008,2009,2010 Old age Andrews-Hanna 2007 Long-range functional connectivity between superior and posterior nodes of DMN retrogresses in old age.

26. Research examples – Inter- individual differences Shannon 2011 Cohort of 107 incarcerated juvenile offenders and observed that impulsivity scores correlated with functional connectivity in dorsal premotor cortex. Separate cohort of normally developing teenagers and young adults, the impulsivity-associated pattern was found to be a correlate of youth.

27. Summary “The resting state is not truly a resting state at all.” “The cognitive function of resting state network might have a chance to be revised.” “The resting state network changes by neurological, psychiatric, and aging.” “The resting state network has inter-individual differences.”

28. Thank you