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2015.5.20

Jinhui Yoon

Contents

IntroductionSome historyPrecursors of resting state fMRIResting state fMRIResearch examplesSummary

Introduction

“Resting state” defined..

In the context of experimentation, “rest” is an opera-tional definition referring to a constant condition without imposed stimuli or other behaviorally salient events.

Introduction

The objective of resting state experiment is to cap-ture the statistical properties of endogenously gener-ated (intrinsic) neural activity.

The objective of event-related studies is to measure evoked or induced responses.

Introduction

Resting state statistical properties of endogenous ac-tivity are modulated by the state of the eyes, by con-current performance of semantic and motor tasks and by concurrent sensory stimulation.

Similar modulations have also been observed imme-diately following task performance.

These effects provide clues regarding the physiologi-cal significance of resting state activity.

Introduction

Unstrained cognition alone does NOT account for the greatest part of intrinsic activity although it un-doubtedly contributes a small increment.

Imposed tasks evoke responses that are mod-est in magnitude in comparison to intrinsic activity.

During slow wave sleep, and even during sur-gical anesthesia, resting state activity persists.

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 activ-ity.

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 cogni-tive significance of trial-to-trial variability in evoked responses. (Arieli 1996, Debener 2007)

Some history

Metabolic investigations of the resting state also date to the years following the WWII.

Kety and Schmidt introduced first quantitative mea-surement of human whole-brain blood flow and me-tabolism (1948).

Sokoloff measured whole-brain blood flow and oxy-gen consumption of resting state and during task, but there was no change. (1955)

Some history

These observations were extended to regional mea-surement 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 de-tected by methods designed to measure the energy consumption of the brain as a whole.

Some history

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

Summary of some history

“The resting state is not truly a resting state at all.”

Precursors of resting state fMRISpontaneous fluctuations in regional oxygen availabil-ity have been actively investigated since the 1950s.

Brain redox state were synchro-nous in homologous regions of both hemisphere. (Vern 1998)

Precursors of resting state fMRISpontaneous waves of blood flow and oxygen avail-ability were related to patterns of electrical activity in experimental animals. (Golanov 1994)

Resting state fMRI

It had been known since the advent of fMRI that the BOLD signal exhibits slow (<0.1Hz) spontaneous fluc-tuations although this phenomenon was initially re-garded as noise.

The neural origin of fluctuation of BOLD signal was established by Bharat Biswal (1995).

Resting state fMRI

Map of the resting state neural connectivity for the PCC.

Research examples - neu-roscience

He et al., 2008

Showing a corre-spondence between the topography of BOLD resting state networks and the correlation structure of ECoG recorded resting state slow cortical potentials.

Research exmaples - neu-roscience

Research examples - neu-roscienceResting state networks are present in anesthetized monkeys. (Vincent 2007)

Research examples - neu-roscience

DMN may be present as well in the mouse

Research examples - neu-roscienceConcerning 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.

Research examples - neu-roscienceIs functional connectivity tied with anatomical connectivity?

Johnston 2008Inter-hemispheric functional connectivity is effec-

tively obliterated in the acute period (days) after complete section of the corpus callosum.

Uddin 2008Interhemispheric functional connectivity may be

present decades after total corpus callosotomy.

Research examples - pathophysiology

Many neurological and psychiatric entities give rise to resting state functional connec-tivity changes.

Pizoli 2011Dramatic improvement in functional connec-tivity architecture following anterior 2/3 corpus callosomy in a child with epileptic en-cephalopathy.

Research examples – De-velopment and aging

Infants – Smyser 2010Children – Fair 2007,2008,2009,2010Old age

Andrews-Hanna 2007

Long-range functional connectivity between superior and posterior nodes of DMN retrogresses in old age.

Research examples – Inter-individual differencesShannon 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.

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 differ-ences .”

Thank you