Transcript Default mode network

Default mode network
2015.5.20
Jinhui Yoon
Contents
Introduction
Some history
Precursors of resting state fMRI
Resting state fMRI
Research examples
Summary
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.
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.
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.
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.
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.
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)
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)
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.
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)
Summary of some history
“The resting state is not truly a resting state at all.”
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)
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)
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).
Resting state fMRI
Map of the resting state neural connectivity for the
PCC.
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.
Research exmaples - neuroscience
Research examples - neuroscience
Resting state networks are present in anesthetized
monkeys. (Vincent 2007)
Research examples - neuroscience
DMN may be present as well in the mouse
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.
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.
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.
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.
Research examples – Interindividual 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.
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 .”
Thank you