Home > neuroscience > Default Mode Network in Rat Brain?

Default Mode Network in Rat Brain?

“Is there a default mode network in the rat brain?”. That was the title of a poster presented by H. LU and colleagues from the Neuroimaging Research Branch of the NIDA-IRP in Baltimore at SfN 10. Here’s the abstract:

The default mode network (DMN), a set of brain regions that exhibit higher basal blood flow, was first identified in humans based on PET measurements (Raichle et al., 2001), and later by resting state fMRI (Greicius et al., 2003). An anatomically similar network has been shown to be present in nonhuman primates (Vincent et al., 2007). From an evolutionary point of view, the discovery of the DMN raises an interesting question: Do rodents also have a DMN? In order to address this question, we performed resting state BOLD fMRI in Sprague-Dawley rats (n = 11) anesthetized with isoflurane in combination with Domitor on a 9.4T scanner. Each rat was scanned once a week for 2 consecutive weeks. Each scan day, four to six sessions of resting state data were acquired within a 2-hour period using single-shot gradient echo EPI. Data from individual animals were registered to a common space. Functional connectivity analyses were performed using both group independent component analysis (gICA) and seed-based correlation methods. The resulting resting state connectivity maps were overlaid onto a digital rat atlas for accurate identification of anatomical structures. The following highly significant bilateral networks were identified by both analytical methods: 1) a motor system; 2) a sensory network, including the whisker barrel cortex, S1FL, S1HL); 3) insular cortex; 4) striatum, which is further divided into ventral medial, ventral lateral and dorsal lateral networks. Some of the networks have been independently reported in previous publications (Lu et al, 2007; Zhao et al., 2008; Pawela et al., 2008; Majeed et al., 2009; Hutchison et al., 2010). Of particular interest, we found a network that includes the anterior cingulate cortex, retrosplenial cortex, bilateral orbitofrontal cortex, medial prefrontal cortex, hippocampus and bilateral temporal association cortex. The retrosplenial cortex is known to be the rat homologue of the human posterior cingulate cortex (Bussey et al., 1996), a key component of the human DMN. The above network appears to mirror that reported in humans (Raichle et al., 2001; Greicius et al., 2003) and nonhuman primates (Vincent et al., 2007). These data raise several interesting questions: What is the exact function of DMN? How did the DMN evolve and did its functional significance remain the same or take on other properties in primates? Our animal model, if further confirmed, could be used to address these questions

So not only DMN correlates with practically anything (see review here), it’s also present in rats? It’s also present in preterm human babies’ brains… What is the exact function of DMN? Probably not “mind wandering” – except if introspection is infants’ and rats’ favourite pastime..

  1. 23/11/2010 at 12:36

    My hypothesis is that the DMN probably exists in all animals. I’ve just submitted a grant to look for it in insects…

  2. 25/11/2010 at 16:07

    I read your papers based on gICA to analyze the resting state fMRI data. However, how can we determine the number of independent components and how can we judge each component as a noise or a signal? It is still difficult work.

  3. 25/12/2012 at 15:24

    Nice blog. I also liked the one on eye movements during reading.

    It seems you are interested in mind-wandering… I thought you might like to know that I am moving to start a group in York in the UK to look at how the mind self-generated the thoughts etc… that we experience during mind-wandering and daydreaming. This should happen in either June or July 2013. You should come and visit as we could have a lot to chat about. Let me know if you are interested (smallwoodjm@gmail.com)

    • 31/01/2013 at 18:28

      thank you! Mind-wandering is very interesting. Currently, using eye tracking technology to investigate attention – personality traits. It’d be great to have a chat when you’re in York.

  4. Dean
    31/01/2013 at 02:40

    I don’t understand how you can know when the mouse’s brain is “at rest”. I’m running a large battery of tasks, one of which is “baseline” or “resting” EEG, in infants and toddlers with various genetic syndromes. However, infants in my lab rarely ever seem to be “at rest”! Of course, investigating the DMN in adults is easy. You just tell them to stay still and quiet, not to engage in any task. But infants are always “doing” something; they are always actively creating and engaging in “tasks”. Obviously, at least some researchers believe that you can investigate the DMN in sleeping infants. I read an excellent paper showing how the DMN develops. But when you’re asleep, isn’t your mind very active – especially during REM sleep? Surely other networks are active, as well as the DMN? Help!

    • 31/01/2013 at 18:18

      Your projects sounds interesting. I agree – the term “resting state” is confusing. The brain is always active anyway! You should probably think of it as spontaneous brain activity that’s not prompted by an external cue/task. And yes, there are other networks active during sleep and rest apart from the DMN. There was an interesting EEG paper that identified loads of task positive and task negative papers a few years ago. I’ll email it to you when I find it! Could be useful.

    • 31/01/2013 at 18:24

      oh, and here’s the DMN in rats paper: http://www.pnas.org/content/109/10/3979.full

  5. Dean
    31/01/2013 at 02:44

    PS In my resting state study (which is based on previous studies), infants look at a dynamic but boring object. But is this really resting state activity?

  1. 06/02/2011 at 21:27

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