The Resting Baseline Objection

What it is

The default mode network was found by comparing tasks with rest. Researchers noticed that a set of regions was more active at rest than during demanding tasks, and some argued that this resting activity is energetically expensive and represents an absolute baseline of brain function.

Morcom and Fletcher questioned whether studies of the resting state are valuable and interpretable. In their paper, titled "Does the brain have a baseline? Why we should be resisting a rest", they argued that observations made at rest have no privileged status as a fundamental metric of brain functioning. They also contended that resting-state research has limited utility in several areas.

The distinction at the centre of it is between cost and reference. That the brain spends a great deal of energy at rest is not in dispute, and the figures are set out in the energy commentary by Raichle and Gusnard. The objection is that cost alone does not make rest the point against which every other state should be measured. A rest condition is one condition among many, and a pattern found by contrasting it with tasks is a pattern about the contrast.

In effect

The objection matters because of how much now rests on the resting state. In a 2015 review, Raichle notes that resting-state studies of the brain's intrinsic activity now play a major role in research on the healthy and the diseased human brain, and that the default mode network is central to that work. If rest is a poor reference condition, a good deal of that work depends on an assumption that has been challenged.

Two replies are available to those who defend the network. The first is that, in the oxygen-extraction data, the decreases were consistent across goal-directed tasks. That is a claim about organisation, and it does not depend on rest being special. The second is that, in the connectivity work of Greicius and colleagues, the same regions stayed coupled during a visual task, so the network does not need a rest condition to exist.

A third consideration comes from the later literature. A 2021 review by Smallwood and colleagues describes the network's activity as dropping during demanding attention tasks and rising during many complex forms of thought, especially those involving memory or abstract reasoning. On that description the word default records how the network was found, not what it does, which is a point the objection anticipates.

What it does not say

It does not deny that the default mode network exists. Nothing in the objection disputes the pattern of decreases or the coupling between the regions.

It does not say that resting-state studies are worthless. The abstract, as read for this page, says the authors question whether such studies are valuable and interpretable, and that they see limited utility in several areas. The full paper may draw finer distinctions than the abstract does, and this page does not claim to have settled them.

It does not claim that the replies fully answer it. They are the strongest responses the vault has found, and the argument between the two positions is not closed.

This page describes a methodological argument in neuroscience. It carries no clinical guidance.

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