Neuroconscience

The latest thoughts, musings, and data in cognitive science and neuroscience.

Tag: DMN

Mind-wandering and metacognition: variation between internal and external thought predicts improved error awareness

Yesterday I published my first paper on mind-wandering and metacognition, with Jonny Smallwood, Antoine Lutz, and collaborators. This was a fun project for me as I spent much of my PhD exhaustively reading the literature on mind-wandering and default mode activity, resulting in a lot of intense debate a my research center. When we had Jonny over as an opponent at my PhD defense, the chance to collaborate was simply too good to pass up. Mind-wandering is super interesting precisely because we do it so often. One of my favourite anecdotes comes from around the time I was arguing heavily for the role of the default mode in spontaneous cognition to some very skeptical colleagues.  The next day while waiting to cross the street, one such colleague rode up next to me on his bicycle and joked, “are you thinking about the default mode?” And indeed I was – meta-mind-wandering!

One thing that has really bothered me about much of the mind-wandering literature is how frequently it is presented as attention = good, mind-wandering = bad. Can you imagine how unpleasant it would be if we never mind-wandered? Just picture trying to solve a difficult task while being totally 100% focused. This kind of hyper-locking attention can easily become pathological, preventing us from altering course when our behaviour goes awry or when something internal needs to be adjusted. Mind-wandering serves many positive purposes, from stimulating our imaginations, to motivating us in boring situations with internal rewards (boring task… “ahhhh remember that nice mojito you had on the beach last year?”). Yet we largely see papers exploring the costs – mood deficits, cognitive control failure, and so on. In the meditation literature this has even been taken up to form the misguided idea that meditation should reduce or eliminate mind-wandering (even though there is almost zero evidence to this effect…)

Sometimes our theories end up reflecting our methodological apparatus, to the extent that they may not fully capture reality. I think this is part of what has happened with mind-wandering, which was originally defined in relation to difficult (and boring) attention tasks. Worse, mind-wandering is usually operationalized as a dichotomous state (“offtask” vs “ontask”) when a little introspection seems to strongly suggest it is much more of a fuzzy, dynamic transition between meta-cognitive and sensory processes. By studying mind-wandering just as the ‘amount’ (or mean) number of times you were “offtask”, we’re taking the stream of consciousness and acting as if the ‘depth’ at one point in the river is the entire story – but what about flow rate, tidal patterns, fishies, and all the dynamic variability that define the river? My idea was that one simple way get at this is by looking at the within-subject variability of mind-wandering, rather than just the overall mean “rate”.  In this way we could get some idea of the extent to which a person’s mind-wandering was fluctuating over time, rather than just categorising these events dichotomously.

The EAT task used in my study, with thought probes.

The EAT task used in my study, with thought probes.

To do this, we combined a classical meta-cognitive response inhibition paradigm, the “error awareness task” (pictured above), with standard interleaved “thought-probes” asking participants to rate on a scale of 1-7 the “subjective frequency” of task-unrelated thoughts in the task interval prior to the probe.  We then examined the relationship between the ability to perform the task or “stop accuracy” and each participant’s mean task-unrelated thought (TUT). Here we expected to replicate the well-established relationship between TUTs and attention decrements (after all, it’s difficult to inhibit your behaviour if you are thinking about the hunky babe you saw at the beach last year!). We further examined if the standard deviation of TUT (TUT variability) within each participant would predict error monitoring, reflecting a relationship between metacognition and increased fluctuation between internal and external cognition (after all, isn’t that kind of the point of metacognition?). Of course for specificity and completeness, we conducted each multiple regression analysis with the contra-variable as control predictors. Here is the key finding from the paper:

Regression analysis of TUT, TUT variability, stop accuracy, and error awareness.

Regression analysis of TUT, TUT variability, stop accuracy, and error awareness.

As you can see in the bottom right, we clearly replicated the relationship of increased overall TUT predicting poorer stop performance. Individuals who report an overall high intensity/frequency of mind-wandering unsurprisingly commit more errors. What was really interesting, however, was that the more variable a participants’ mind-wandering, the greater error-monitoring capacity (top left). This suggests that individuals who show more fluctuation between internally and externally oriented attention may be able to better enjoy the benefits of mind-wandering while simultaneously limiting its costs. Of course, these are only individual differences (i.e. correlations) and should be treated as highly preliminary. It is possible for example that participants who use more of the TUT scale have higher meta-cognitive ability in general, rather than the two variables being causally linked in the way we suggest.  We are careful to raise these and other limitations in the paper, but I do think this finding is a nice first step.

To ‘probe’ a bit further we looked at the BOLD responses to correct stops, and the parametric correlation of task-related BOLD with the TUT ratings:

Activations during correct stop trials.

Activations during correct stop trials.

Deactivations to stop trials (blue) and parametric correlation with TUT reports (red)

Deactivations to stop trials (blue) and parametric correlation with TUT reports (red)

As you can see, correct stop trials elicit a rather canonical activation pattern on the motor-inhibition and salience networks, with concurrent deactivations in visual cortex and the default mode network (second figure, blue blobs). I think of this pattern a bit like when the brain receives the ‘stop signal’ it goes, (a la Picard): “FULL STOP, MAIN VIEWER OFF, FIRE THE PHOTON TORPEDOS!”, launching into full response recovery mode. Interestingly, while we replicated the finding of medial-prefrontal co-variation with TUTS (second figure, red blob), this area was substantially more rostral than the stop-related deactivations, supporting previous findings of some degree of functional segregation between the inhibitory and mind-wandering related components of the DMN.

Finally, when examining the Aware > Unaware errors contrast, we replicated the typical salience network activations (mid-cingulate and anterior insula). Interestingly we also found strong bilateral activations in an area of the inferior parietal cortex also considered to be a part of the default mode. This finding further strengthens the link between mind-wandering and metacognition, indicating that the salience and default mode network may work in concert during conscious error awareness:

Activations to Aware > Unaware errors contrast.

Activations to Aware > Unaware errors contrast.

In all, this was a very valuable and fun study for me. As a PhD student being able to replicate the function of classic “executive, salience, and default mode” ‘resting state’ networks with a basic task was a great experience, helping me place some confidence in these labels.  I was also able to combine a classical behavioral metacognition task with some introspective thought probes, and show that they do indeed contain valuable information about task performance and related brain processes. Importantly though, we showed that the ‘content’ of the mind-wandering reports doesn’t tell the whole story of spontaneous cognition. In the future I would like to explore this idea further, perhaps by taking a time series approach to probe the dynamics of mind-wandering, using a simple continuous feedback device that participants could use throughout an experiment. In the affect literature such devices have been used to probe the dynamics of valence-arousal when participants view naturalistic movies, and I believe such an approach could reveal even greater granularity in how the experience of mind-wandering (and it’s fluctuation) interacts with cognition. Our findings suggest that the relationship between mind-wandering and task performance may be more nuanced than mere antagonism, an important finding I hope to explore in future research.

Citation: Allen M, Smallwood J, Christensen J, Gramm D, Rasmussen B, Jensen CG, Roepstorff A and Lutz A (2013) The balanced mind: the variability of task-unrelated thoughts predicts error monitoringFront. Hum. Neurosci7:743. doi: 10.3389/fnhum.2013.00743

Switching between executive and default mode networks in posttraumatic stress disorder [excerpts and notes]

From: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2895156/?tool=pubmed

Daniels et al, 2010

We decided to use global scaling because we were not analyzing anticorrelations in this paradigm and because data presented by Fox and colleagues66 and Weissenbacher and coworkers65 indicate that global scaling enhances the detection of system-specific correlations and doubles connection specificity. Weissenbacher and colleagues65 compared different preprocessing approaches in human and simulated data sets and recommend applying global scaling to maximize the specificity of positive resting-state correlations. We used high-pass filtering with a cut-off at 128 seconds to minimize the impact of serial autocorrelations in the fMRI time series that can result from scanner drift.

Very useful methodological clipping!

The control condition was a simple fixation task, requiring attention either to the response instruction or to a line of 5 asterisks in the centre of the screen. We chose this control task to resemble the activation task as closely as possible; it therefore differed considerably from previous resting state analyses because it was relatively short in duration and thus necessitated fast switches between the control condition and the activation task. It also prompted the participants to keep their eyes open and fixated on the stimulus, which has been shown to result in stronger default mode network activations than the closed-eyes condition.60

Good to remember: closed-eyed resting states result in weaker default mode activity.

To ensure frequent switching between an idling state and task-induced activation, we used a block design, presenting the activation task (8 volumes) twice interspersed with the fixation task (4 volumes) within each of 16 imaging runs. Each task was preceded by an instruction block (4 volumes duration), amounting to a total acquisition of 512 volumes per participant. The order of the working memory tasks was counterbalanced between runs and across participants. Full details of this working memory paradigm are provided in the study by Moores and colleagues.6 There were 2 variations of this task in each run concerning the elicited button press response; however, because we were interested in the effects of cognitive effort on default network connectivity, rather than specific effects associated with a particular variation of the task, we combined the response variations to model a single “task” condition for this study. The control condition consisted of periods of viewing either 5 asterisks in the centre of the screen or a notice of which variation of the task would be performed next.

Psychophysiological interaction analyses are designed to measure context-sensitive changes in effective connectivity between one or more brain regions67 by comparing connectivity in one context (in the current study, a working memory updating task) with connectivity during another context (in this case, a fixation condition). We used seed regions in the mPFC and PCC because both these nodes of the default mode network act independently across different cognitive tasks, might subserve different subsystems within the default mode network and have both been associated with alterations in PTSD.8

This paradigm is very interesting. The authors have basically administered a battery of working memory tasks with interspersed rest periods, and carried out ROI inter-correlation, or seed analysis. Using this simple approach, a wide variety of experimenters could investigate task-rest interactions using their existing data sets.

Limitations

The limitations of our results predominantly relate to the PTSD sample studied. To investigate the long-lasting symptoms that accompany a significant reduction of the general level of functioning, we studied alterations in severe, chronic PTSD, which did not allow us to exclude patients taking medications. In addition, the small sample size might have limited the power of our analyses. To avoid multiple testing in a small sample, we only used 2 seed regions for our analyses. Future studies should add a resting state scan without any visual input to allow for comparison of default mode network connectivity during the short control condition and a longer resting state.

The different patterns of connectivity imply significant group differences with task-induced switches (i.e., engaging and disengaging the default mode network and the central-executive network).

Google Wave for Scholarly Co-authorship: excerpt from Neuroplasticity and Consciousness Abstract

Gary Williams and I are working together on a paper investigating the consciousness and neuroplasticity. We’re using Google wave for this collaboration, and I must say it is an excellent co-authorship tool. There is nothing quite so neat as watching your ideas flow and meld together in real time. There are now new built in document templates that make these kinds of projects a blast. As an added bonus, all edits are identified and tracked in real time, letting you keep easy track of who wrote what. One of the most suprising things to come out of this collaboration is the newness of the thoughts. Whatever it is we end up arguing, it is definetely not reducible to the sum of it’s parts. As a teaser, I thought I’d post a thread from the wave I made this morning. This is basically just me rambling on about consciousness and plasticity after reading the results of our wave. I wish I could post the movie of our edits, but that will have to wait for the paper’s submission.

I have an idea I want to work in that was provoked by this paper:
http://www.jneurosci.org/cgi/content/abstract/30/18/6205

Somewhere in here I still feel a nagging paradox, but I can’t seem to put my finger on it. Maybe I’m simply trying to explain something I don’t have an explanation for. I’m not sure. Consider this a list of thoughts that may or may not have any relationship to the kind of account we want to make here.

They basically show that different synthesthetic experiences have different neural correlates in the structural brain matter. I think it would be nice to tie our paper to the (likely) focus of the other papers; the idea of changing qualia / changing NCCs. Maybe we can argue that, due to neural plasticity, we should not expect ‘neural representations’ for sensory experience between any two adults to be identical; rather we should expect that every individual develops their own unique representational qualia that are partially ineffable. Then we can argue that it this is precisely why we must rely on narrative scaffolding to make sense of the world; it is only through practice with narrative, engendered by frontal plasticity, that we can understand the statistical similarities between our qualia and others. Something is not quite right in this account though… and our abstract is basically fine as is.

So, I have my own unique qualia that are constantly changing- my qualia and NCCs are in dynamical flux with one another. However, my embodiment pre-configures my sensory experience to have certain common qualities across the species. Narrative explanations of the world are grounded in capturing this intersubjectivity; they are linguistic representations of individual sense impressions woven together by cultural practices and schema. What we want to say is that, I am able to learn about the world through narrative practice precisely because I am able to map my own unique sensory representations onto others.

I guess that last part of what I said is still weak, but it seems like this could be a good element to explore in the abstract. It keeps us from being too far away from the angle of the call though, maybe. I can’t figure out exactly what I want to say. There are a few elements:

  • Narratives are co-created, coherent, shareable, complex representations of the world that encode temporality, meaning, and intersubjectivity.
  • I’m able to learn about these representations of the world through narrative practice; by mapping my own unique dynamic sensory experience to the sensory and folk psychological narratives of others.
  • Narrative encodes sensory experience in ways that transcend the limits of personal qualia; they are offloaded and are no longer dynamic in the same way.
  • Sensory experience is in constant flux and can be thrown out of alignment with narrative, as in the case of most psychopathy.
  • I need some way to structure this flux; narrative is intersubjective and it provides second order qualia??
  • Narrative must be plastic as it is always growing; the relations between events, experiences, and sensory representations must always be shifting. Today I may really enjoy the smell of flowers and all the things that come with them (memory of a past girlfriend, my enjoyment of things that smell sweet, the association I have with hunger). But tommorow I might get buried alive in some flowers; now my sensory representation for flowers is going to have all new associations. I may attend to a completely different set of salient factors; I might find that the smell now reminds me of a grave, that I remember my old girlfriend was a nasty bitch, and that I’m allergic to sweet things. This must be reflected in the connective weights of the sensory representations; the overall connectivity map has been altered because a node (the flower node) has been drastically altered by a contra-narrative sensory trauma.
  • I think this is a crucial account and it helps explain the role of the default mode in consciousness. On this account, the DMN is the mechanism driving reflective, spontaneous narrativization of the world. These oscillations are akin to the constant labeling and scanning of my sensory experience. That they in sleep probably indicates that this process is highly automatic and involved in memory formation. As introspective thoughts begin to gain coherency and collude together, they gain greater roles in my over all conscious self-narrative.
  • So I think this is what I want to say: our pre-frontal default mode is system is in constant flux. The nodes are all plastic, and so is the pattern of activations between them. This area is fundamentally concerned with reflective-self relatedness and probably develops through childhood interaction. Further, there is an important role of control here. I think that a primary function of social-constructive brain areas is in the control of action. Early societies developed complex narrative rule systems precisely to control and organize group action. This allowed us to transcend simple brute force and begin to coordinate action and to specialize in various agencies. The medial prefrontal cortex, the central node, fundementally invoked in acts of social cognition and narrative comprehension, has massive reciprocal connectivity to limbic areas, and also pre-frontal areas concerned with reward and economic decision making.
  • We need a plastic default mode precisely to allow for the kinds of radical enculturation we go through during development. It is quite difficult to teach an infant, born with the same basic equipment as a caveman, the intricacies of mathematics and philosophy. Clearly narrative comprehension requires a massive amount of learning; we must learn all of the complex cultural nuances that define us as modern humans.
  • Maybe sensory motor coupling and resonance allow for the simulation of precise spatiotemporal activity patterns. This intrinsic activity is like a constant ‘reading out’ of the dynamic sensory representations that are being constantly updated, through neuroplasticity; whatever the totality of the connection weights, that is my conscious narrative of my experience.
  • Back to the issue of control. It’s clear to me that the prefrontal default system is highly sensitive to intersubjective or social information/cues. I think there is really something here about offloading intentions, which are relatively weak constructions, into the group, where they can be collectively acted upon (like in the drug addict/rehab example). So maybe one role of my narration system is simply to vocalize my sensory experience (I’m craving drugs. I can’t stop craving drugs) so that others can collectively act on them.

Well there you have it. I have a feeling this is going to be a great paper. We’re going to try and flip the whole debate on it’s head and argue for a central role of plasticity in embodied and narrative consciousness. It’s great fun to be working with Gary again; his mastery of philosophy of mind and phenomenology are quite fearsome, and we’ve been developing these ideas forever. I’ll be sure to post updates from GWave as the project progresses.

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