Default mode network
The wiki’s third intrinsic network, and the last to get a page — it had appeared only as the thing the right anterior insula switches away from in Craig (2009). Barrett (2017) gives it a central role.
Barrett’s hypothesis: the DMN is the internal model
I hypothesize, as others do (Mesulam, 2002; Hassabis and Maguire, 2009; Buckner, 2012), that the default mode network is necessary for the brain’s internal model.
Whatever else gets mapped to DMN activity — mind-wandering, memory, prospection, self-reference, semantics — the simulations initiated there “cascade to create concepts that eventually categorize sensory inputs and guide movements in the service of allostasis.”
Barrett is careful about what this does and does not say, and the care is the interesting part. Two disclaimers:
- Concepts are not stored in the DMN. “I’m saying that the default mode network represents efficient, multimodal summaries, from which a cascade of predictions issues through the entire cortical sheet, terminating in primary sensory and motor regions. The whole cascade is an instance of a concept.” The DMN holds part of the pattern, not the pattern.
- This does not make the DMN an emotion network. Domain-general networks “can be mapped to many psychological categories at the same time.” That is the point of them.
The hypothesis is “partially consistent” with the semantic-network reading of the DMN (Binder et al., 2009): Barrett’s addition is that simulations are “more than just multimodal sensorimotor summaries; they are fully embodied brain states,” which they become as the summaries cascade out and particularize.
The species-general claim, and the footnote defending it
Worth recording because it shows the shape of the theory. Rats have a DMN and, as far as anyone can tell, cannot engage in mental time travel (Hsu et al., 2016). If the DMN were for mental time travel, that would be awkward. Barrett’s footnote says it “in no way disconfirms the hypothesis that the network is running an internal model of the animal’s world in the service of allostasis.”
That is a reasonable reply and also a demonstration of the falsifiability worry recorded on theory-of-constructed-emotion: the network’s function is specified at a level general enough that a species lacking the headline capacity is not a counterexample.
Relation to the wiki’s other networks
Barrett’s division of labour across the three intrinsic networks:
| network | job |
|---|---|
| default mode | hosts the internal model; initiates the prediction cascade |
| salience | precision — decides which prediction errors are worth encoding |
| frontoparietal control | sustains simulations over longer timescales; suppresses low-prior ones |
She reports (Table 2) that DMN–salience interconnectivity tracks the intensity of emotional experience, as distinct from arousal (Raz et al., 2016) — one of the few entries in her supporting table that is a direct positive prediction rather than a reinterpreted null.
Figure 6 of the source presents the two networks as a single large-scale system for allostasis and interoception, interconnected by rich-club hubs (ventral anterior insula, midcingulate, parahippocampal gyrus, postcentral gyrus, cuneus) and reaching subcortically to PAG, PBN, NTS, ventral striatum, hypothalamus and thalamus. Mapped in 280 participants and replicated in a further 270 — though the anatomy is credited to Kleckner et al., which was “in press” at the time.
The DMN as a clinical predictor: self-reference that will not disengage
Farb et al. (2011) give the DMN’s self-referential role a prospective clinical stake. In remitted depressed patients watching a sad film, reactivity in medial prefrontal cortex (BA 24/32 — a core DMN hub) predicted relapse over 18 months (r = .68) and tracked trait rumination, while sensory (visual) reactivity protected against relapse and tracked acceptance. The signature of risk was specifically a failure to disengage self-referential processing: dorsal and ventral mPFC, normally anticorrelated, became positively coupled in the patients who relapsed. So the DMN here is not merely “the internal model” in the abstract (Barrett) — it is the substrate of the ruminative, self-evaluative mode whose over-engagement forecasts a return of depression (see cognitive-reactivity). The wiki thus meets the DMN twice: as Barrett’s body-budgeting internal model, and as the clinical site of pathogenic self-focus — the same anatomy, read once as generative machinery and once as a mode that can get stuck on the self.
Why this page matters to the wiki’s convergence story
Note what has happened to the region set. The wiki records a three-way convergence on nearly the same regions from independent starting points — the salience-network (functional connectivity, Seeley), the core affect network (meta-analytic, Lindquist), and the VMAs (cytoarchitectural, Seth & Friston).
Barrett’s Figure 6 adds the DMN to that set and reframes the whole thing: these are not three descriptions of an emotion system that happen to coincide. They are one system, and it is not for emotion — it is for budgeting the body. The convergence the wiki had been treating as a striking coincidence between literatures is, on this account, what you would expect, because all three were measuring the allostasis/interoception system and calling it emotion.