One of the most common pieces of advice you’ll get when you’re stuck on a seemingly intractable problem is to stop trying and just let your mind wander.
Sometimes your best efforts are no conscious effort at all. Listen to the rain falling, watch the sunset, do anything but do anything, the advice goes, and the answer to your problem will emerge all on its own.
That this is not nonsensical advice is thanks to a series of brain functions known as the “default mode network” (DMN), and until now it’s been thought to be one of the many cognitive functions that we have and other animals don’t — one of the ways that our consciousness differs from that of “lower” animals.
New research begins to question this view, as reported in “Zoned-out rats may give clue to consciousness,” published by New Scientist on October 12th. Here’s how the article’s author, Jessica Hamzelou, describes the functioning of the human DMN:
The default mode network (DMN) is one of about 10 networks of brain regions that are active when a person is at rest. What makes the DMN interesting is that it becomes active when a person is asked to let their [sic] mind wander, but the network’s activity drops away completely as soon as that person is given an external task. This suggests that, in humans at least, the DMN is involved in self-reflection and introspective thought processing.
Recent studies with monkeys show that our primate relatives seem to have similar structures. As Hamzelou reports, a team in Belgium analyzed the data of fifteen studies of monkey brains at rest and “by looking at the baseline brain activity measured in each project, the group was able to spot a network of brain structures that were active when the monkeys were not engaged in a task. This network looked strikingly similar to the human DMN.”
More recently, and further “down” the evolutionary chain from us, “the latest evidence … suggests that a similar network also exists in resting rats.” A researcher “minimally sedated 16 rats before assessing their brain activity using functional MRI. By comparing the brain activity of each rat while they were resting or stimulated with a gentle shock to the paw, the group was able to identify a DMN in the rats. ”
This is interesting enough in itself, but of course there’s a larger and more important issue at play here:
The big question raised by the results is whether the monkey or rat DMN might perform a similar function to the human network. Can such animals really share our self-reflecting ability or does the presence of the DMN in monkey and rat brains suggest another, more basic function?
One “more basic function” offered by researchers is that the DMN in other animals is part of the system by which the animal processes memories. The “down time” may be used to recall old memories, or to lay down new ones. If this is true, monkeys and rats in the DMN state may not experience the equivalent of what we know as “consciousness,” aware self-reflection, at all.
But then again, they might. “The latest study … found that the DMN of awake monkeys does include the PFC, suggesting that the original findings may have been affected by sedation instead of representing a species difference. … the DMN in the minimally anaesthetised rat also includes prefrontal regions.”
Hamzelou concludes by citing this observation from one researcher: “The activity in frontal areas [could suggest] the notion of a sense of self in the rat. … I’ve got to believe it’s different from humans but it’s certainly provocative.”
Provocative, indeed. Of course a few studies with a few dozen monkeys and rats and an MRI machine are nowhere near conclusive, nor do the researchers claim anything remotely like that.
Still, I have no hesitation to suggest that these results are another nail in the coffin of the notion of a non-material human consciousness.
Once again, “lower” animals exhibit modest versions of the brain structures and, to some extent at least, the cognitive activity of human minds. It’s not that these animals are thinking like we do, or experiencing the rich perceptions of selfhood that we do. But they are using similar brain parts in similar ways. And that’s the big deal.
Let’s grant that human consciousness is massively richer and more complex than the equivalent mental state of any other animal. Let’s even grant that what we experience as consciousness is so much richer and so much more complex than the mental life of other animals that we can’t call what they experience “consciousness” at all. Granted, and granted.
Nothing in the last two paragraphs adds any evidence to the “consciousness is more” argument or takes anything away from the claim that the mind is a function of the brain — and that consciousness is our perception of the mind.
I’ve yet to encounter a better explanation of this notion than that contained in Antonio Damasio’s Self Comes to Mind, which I reviewed in two articles a few months ago, and once again I urge you to read it, if you haven’t done so already.
I don’t see how anyone can argue seriously that the human brain started out as a physical entity, developed functions that made it mind, and those functions spontaneously generated an ephemeral, non-material state called consciousness.
Consciousness comes from mind, and mind comes from brain — and brain we share with monkeys, and rats, and wombats, and geckos, and …
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Enough of this for now. I’m sure that regular readers have gotten the point by now, or grown weary of my reiterations of a single point, or — most likely — both.
Starting next time, a series on our social problems, somewhat in response to the “Occupy _fillintheblank_” movements that are all over the news these days.