3. “Biological Psychiatry” (1950s), understanding mental
illness via identifying the underlying neural mechanisms.
Novel neuroimaging technologies, (SPECT, PET, and
fMRI) for the assessment of functional characteristics of
brain.
Shifting of focus from task related brain activation to
resting state activation .
Concept of which is being applied to study both the normal
and abnormal functioning of brain
4.
5. Nodes : elements such as neurons or areas
Edges : their interrelations or connections
The arrangement of these nodes and edges relative to
one another defines the network’s topology.
6.
7.
8. (autopilot mode/projection/emotional mind) network
manage a state in which an individual is alert but is not
actively involved in an attention demanding tasks.
Supported by decreased activity in a task engaged state
Associated with attention to internal emotional states
Directs attention to internal word and awareness of self
10. Social cognition : adaptive social cognition by integration
of personal and inter personal information and providing a
means for personal experiences to become social conceptual
knowledge
integrate salient external or internal information with one’s
current social context.
Meditation : In experienced meditators, it was found to
induce deactivation of DMN areas.
Mindfullness and cognitive based intervention e.g. in social
phobia result in increased DMN activity
11. Intelligence :
The brain’s network configuration varies based on
current task demands.
High-performing individuals possess a rest state DMN
that is “preconfigured” to switch to a variety of
possible task FC states
Creativity : depends on the joint engagement of
Executive control is processes that regulate mental
resources.
Spontaneous thinking requires association between the
flow of thoughts, emotions, images, sounds etc, in a
continuous stream of internal processing.
12. Disorder Impaired function Evidence
Schizophrenia internal emotional states reduced connectivity within and
between networks, structural and
functional abnormal connectivity
patterns in patients compared to healthy
controls (Petterson-Yeo, et al)
Mood disorders cognitive symptoms,
difficulty in concentration
repetition of thoughts and
ideas i.e. rumination
a) Dysfunctional connectivity related to
symptoms
b) Correlation between duration and no
of episodes with disrupted DMN
connectivity
OCD problems in disengaging
attention from ruminative
thoughts or mental images
a)Jang et al reported decreased
functional connectivity
btw several regions of the DMN
b) significant negative correlation btwn
symptom severity and functional
connectivity from the posterior
cingulate
13. Disorder Impaired function Evidence
Temporal lobe Epilepsy Dysregulation in
depolarization of specific
neuronal networks
Disrupted functional
connectivity between
mesial temporal lobe and
DMN regions.
Alzheimer’s disease DMN activity at rest is
necessary for memory
consolidation suggests
potential role in AD
development
a) Decreased FC between
posterior & anterior
portions of DMN
b) Overlap between DMN
& pattern of amyloid
deposits
14. Impaired function Evidence
ADHD to perform a task, DMN must
be actively suppressed to
alleviate an inappropriate
response
a) Correlation between DMN
activation and impaired task
performance
b) Normalization of disrupted
connectivity between cognitive
control network and DMN after
treatment with Atomoxetine &
Methylphenidate
Autism impairment in the ability to
decode the mental states of
self and others.
1) increased within-network
connectivity in the DMN, most
notably between the PCC and mPFC;
2) reduced connectivity of DMN
nodes with other functional
systems outside the DMN
15. Parkinson’s
disease
Striatal neurons
have been shown to
coordinate activity
not only in BG, but
also in cortical
regions, specifically
in DMN
a) Disruption in DMN and central
executive network ( CEN)-
heightened activation &
dysfunctional connectivity
b) Visual hallucination- increased
DMN connectivity
PTSD a) reduced network coupling within
the DMN
B )trauma experience alters DMN
connectivity shortly after its
occurrence.
16. Detects and filters salient emotional and
sensory stimuli
key sub cortical nodes of the SN, provide
access to the emotional and reward saliency
of stimuli
detection of deviant stimuli embedded in a
stream of standard stimuli.
Coordinates with the DMN and CEN.
17. Frontotemporal dementia : progressive breakdown of
the SN arising from an initial core of frontoinsular region.
unable to model the emotional impact of their own actions
or inactions.
18. Autism : SN – Identifiable by 2 years of age - 7 yrs
Significant hyperconnectivity - inappropriate assignment
of saliency to external stimuli or internal mental events
The SN’s functional organization also predicts restricted
and repetitive behavior scores – one of the core symptoms
of childhood autism
19. Functional and structural dysfunction of the SN
Bilateral volume reduction in the AI and dACC nodes
of the SN - severity of reality distortion
Aberrant intrinsic functional connectivity of the SN and
its interactions with other networks - found in patients
with schizophrenia and younger adults at risk for
psychosis
Aberrant signaling - abnormalities in the attribution of
salience to external and internal stimuli – Formation of
delusion and hallucination
20. All the major nodes of the SN are affected in patients
with major depression – may be the reason for
repetitive, preservative, negative thinking and biases in
attention to negative events
Decreased intrinsic connectivity of the SN – Improper
detection of motivated behavior – Apathy
21. Hyperactivity of the Angular Insula of the SN has been
consistently detected in patients
Alterations within the SN is a consistent finding in
patients with generalized anxiety disorder (GAD),social
anxiety disorder and posttraumatic stress disorder
22. The amygdala, ventral striatum, and ventral tegmental
area – provide preferential context-specific access to
affective and reward cues
Amygdala -negatively valenced stimuli
Nucleus accumbens and ventral tegmental area –
reward
Emotional and motivational signals - preferential
access to affective cues - cognition–action mechanisms
23. Also known as executive
control network/cognitive
control network.
Takes control and
actively process
information.
involved in suppression
of impulses.
24. The lateral posterior parietal cortex integrates sensory and
interoceptive information in order to facilitate sustained
attention.
In addition to involvement in practical decision-making,
the CEN is also implicated in task-oriented (e.g., top-down)
processing necessary for effective emotion-regulation.
psychiatric relevance :
CEN hypo activity is associated with depression and
various cognitive disorders
lesser CEN activation is associated with greater rumination.
25.
26. Switching between large-scale brain networks involved in
externally oriented attention and internally oriented mental
processes
Cognitively demanding tasks - SN & CEN and DMN
Brain responses within these regions increase and decrease
proportionately and often antagonistically, in relation to
specific cognitive demands and subjective task difficulty
Switching mechanisms - focus attention on task-relevant
stimuli and goals - saliency
27. includes the dACC, bilateral dorsal anterior insula, and
sometimes both thalamic regions and anterior
prefrontal regions.
28. The frontal–parietal and the cingulo–opercular
networks are consistently associated with a variety of
cognitive control functions.
Especially the executive controls
(tested with Flanker task ,wisconsin card sorting task
and stroop task )
29. Reduced global and local efficacy in known cognitively
impaired schizophrenics.
Emotional dysregulations due to altered connectivity
with amygdala : major depression
Deficits in executive control
Perseverative errrors
30. associated with cognitive function
more so top-down and/or stimulus driven attention
functions.
The dorsal attention network is closely aligned with
the frontal–parietal network as it includes both dorsal
frontal and parietal regions
also dorsal supplementary motor and eye field areas.
31. ventral attention system includes the temporal–
parietal junction and the VLPFC
associated with attention to salient events in the
environment.
Altered connectivity has been associated with anxiety
disorders, under the hypotheses that it could
contribute to altered attention to threat relevant
stimuli in anxiety disorders.
32. Retrospenial temporal network- association with DMN
for associative memory
Cingulo – parietal network for intelligence
33. Field is still in its infancy stage
Human Connectome Project has confirmed that individual
variation in intrinsic network connectivity relates to a wide
range of both positive and negative traits and
characteristics in humans.
In schizophrenia evidence for impairments in global and
local efficiency of frontal–parietaland cingulo–opercular
networks in relation to cognitive function.
34. major depression, there is consistent evidence for
altered amygdala to prefrontal–cingulate connectivity
relevant for emotion regulation, as well as evidence for
increased default mode connectivity in relation to
rumination.
35. Clinical and translational aspects: Using network
properties as diagnostic markers.
Linking alterations at this neural circuit level of
analysis with alterations at other levels of analysis,
such as genes, gene expression,neurotransmitter
signaling, and/or cellular architecture.
promising avenue for future biomarker and intervention
work.
36. Sadock, B. J., Sadock, V. A., & Ruiz, P. (2017). Comprehensive
textbook of psychiatry 10th edition.
Sporns, O. (2010). Networks of the Brain. MIT press.
The Significance of the Default Mode Network (DMN) in
Neurological and Neuropsychiatric Disorders: A Review
Uddin, L. Q. (2016). Salience network of the human brain.
Academic press.
Geddes, J. R., & Andreasen, N. C. (2020). New Oxford textbook
of psychiatry. Oxford University Press, USA.
The Brain’s Default Network Anatomy, Function, and
Relevance to Disease
Uddin, L. Q., Supekar, K., Lynch, C. J., Khouzam, A., Phillips,
J., Feinstein, C., ... & Menon, V. (2013). Salience network–
based classification and prediction of symptom severity in
children with autism. JAMA psychiatry, 70(8), 869-879.
Editor's Notes
Lateral and medial view of the default-mode network of the left hemisphereThe medial regions of the default-mode network are connected through the cingulum, whereas the inferior parietal cortex is connected to the precuneus and posterior cingulate cortex through a short intraparietal tract. The tracts are reconstructed using diffusion tensor imaging tractography.
