Default Mode Network

The default mode network is the neurological basis of “the self.” It is most commonly active when a person is not focused on the outside world and the brain is at wakeful rest, such as during daydreaming, mind-wandering, thinking about others, thinking about themselves, remembering the past, and planning for the future. It can be active in other goal-oriented tasks such as social working memory or autobiographical tasks. The DMN has been shown to be negatively correlated with the brain’s attention networks.
The brain’s default network participates in internal modes of cognition. The default network is a specific, anatomically defined brain system preferentially active when individuals are not focused on the external environment. [1]
During performance of attention-demanding tasks, structures comprising the Task Positive Network (TPN) are characterized by increases in activation; in contrast, DMN structures are characterized by decreased activity. During wakeful rest, the opposite pattern emerges, with the DMN becoming more active and the TPN less active. [2]
Functional Hubs: Posterior Cingulate Cortex (PCC), Precuneus, Medial-Prefrontal Cortex (mPFC), and Angular Gyrus. [4]
Dorsal Medial Subsystem: Functional Hubs, Dorsal Medial-Prefrontal Cortex (dmPFC), Temporoparietal Junction (TPJ), Lateral Temporal Cortex, and Anterior Temporal Pole. [4]
Medial Temporal Subsystem: Functional Hubs, Hippocampus (HF+), Parahippocampus (PHC), Retrosplenial Cortex (RSC), Posterior Inferior Parietal Lobe (pIPL). [4]

Task Positive Network

The task-positive network is made up of areas in the brain that typically increase in activation during attention-demanding tasks. During performance of attention-demanding tasks, structures that comprise the task-positive network are characterized by increases in activation; in contrast, default mode network structures are characterized by decreased activity. During wakeful rest, the opposite pattern emerges, with the DMN becoming more active and the TPN less active. [2]
The Task Positive Network is also known as the Central Executive Network.
Key Nodes: Posterior Parietal Cortex (PPC) and Dorsal Lateral Prefrontal Cortices (dlPFC). [5]
Other Associated Brain Regions: Intraparietal Sulcus (IPS), Frontal Eye Fields, Ventral Prefontal Cortices (vPFC), Insula, Supplementary Motor Area (SMA). [7] [8]

Default Mode Network and Task Positive/Central Executive Network

*The video states the amygdala is part of the DMN. The amygdala interacts with the DMN, but it is considered part of The Salience Network

Salience Network

Switching Between DMN/TPN

The two major brain networks, the Default Mode Network (DMN) and Task Positive Network, typically reveal negative and variable connectivity in resting-state. The results of this study suggest that the salience network may modulate the relationship between the DMN and Executive Networks. [3]
We observed significant activation of the CEN and deactivation of the DMN, along with activation of a third network when participants perceived salient auditory event boundaries. We show that the rFIC-ACC [Salience] network, and the rFIC, in particular, plays a critical and causal role in switching between the CEN and the DMN. [5]
This work confirms that the salience network drives the switching between default mode and central executive networks and that our novel technique is repeatable. [10]

Salience Network and Behavior Modulation

These findings contribute to existing research indicating a central role for the Salience Setwork in modulating and regulating the activity of other large-scale networks such as the Default Mode Network, which may help to explain the profound behavioural consequences of injury to the Salience Network in behavioural variant FTD and other disorders. [11]
Self-control and the ability to resist temptation are critical for successful completion of long-term goals. Models in cognitive neuroscience emphasize the primary role of prefrontal cognitive control networks in aligning behavior with such goals. These results suggest that individual differences in self-control in the face of temptation might be driven in part by SN functional connectivity context. [12]
These results emphasize that salience detection is a crucial component of moral behavior, and suggest that detection of morally-relevant information in the environment is associated with salience detection systems in the human brain. This model of moral judgment, implicating the salience network in early detection of behaviorally-relevant, moral information, and later coordination of associative and appraisal processes, suggests that attentional influences are involved in everyday moral judgments. [13]
The anterior insula and the anterior cingulate cortex form a “Salience Network” that functions to segregate the most relevant among internal and extrapersonal stimuli in order to guide behavior. In this manner, with the insula as its integral hub, the salience network assists target brain regions in the generation of appropriate behavioral responses to salient stimuli. [14]
Agitation and aggression in Alzheimer’s disease and mild cognitive impairment is associated with neurodegeneration affecting the anterior salience network that may reduce capacity to process and regulate behaviors properly. Greater agitation and aggression severity was associated with greater atrophy of frontal, insular, amygdala, cingulate, and hippocampal regions of interest. [15]
Primary Hubs: Anterior Insula (AI) (Also known as the Fronto Insular Cortex – FIC), Dorsal Anterior Cingulate Cortex (dACC), Ventrolateral Prefrontal Cortex (VLPFC). [5] [6]
Subcortical Structures: Substantia Nigra, Ventral Tegmental Area, Ventral Striatum, Amygdala, Dorsomedial Thalamus, and Hypothalamus. [6]

Limbic System

The Limbic System is traditionally considered to be our emotional brain. It supports a variety of functions including emotion, behavior, motivation, long-term memory, formation of memories, and olfaction. The “boundaries” of the limbic system have been repeatedly redefined because of advances in neuroscience. While it is true that limbic structures are more closely related to emotion, the limbic system itself is best thought of as a component of a larger emotional processing plant, that is responsible for sifting through, organizing, lower order processing, and relaying sensory information to other brain areas for higher order emotional processing.
The Limbic System is not its own network, but rather a system of brain regions, within other networks, responsible for critical front-line, lower order emotional processing.
Cortical Areas: Limbic Lobe, Orbitofrontal Cortex, Piriform Cortex, Entorhinal Cortex, Hippocampus, Fornix. [9]
Subcortical Areas: Septal Nuclei, Amygdala, Nucleus Accumbens. [9]
Diencephalic Structures: Hypothalamus, Mammillary Bodies, Anterior Nuclei of Thalamus. [9]

Limbic System

Amygdala

The amygdala plays a large role in general emotional processing, both positive and negative stimuli.
Involved in the consolidation of memories with a strong positive or negative emotional component.
It receives sensory information from systems that process the external world. (i.e. Visual, Auditory, Olfactory, Touch, Pain, etc.) As a result, it is integral in the physiological response to danger and other sensory stimuli.
This sensory information converges in the amygdala and the amygdala outputs to systems involved in emotional reactivity.
It also receives information from higher order systems like the prefrontal cortex and other higher order association areas involved in integrative activities.
It plays a large role in Pavlovian Associations (i.e. Goal Directed Behavior).

Hippocampus

The Hippocampus is responsible for forming short and long-term memories through consolidating information.
It is important for learning new skills from reward, punishment, reinforcement, and failure.
It plays a role in olfactory senses (i.e. Tying together smells with specific memories).