Neuroconscience

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

Tag: intrinsic connectivity

Neuroscientists: What’s the most interesting question right now?

After 20 years of cognitive neuroscience, I sometimes feel frustrated by how little progress we’ve made. We still struggle with basic issues, like how to ask a subject if he’s in pain, or what exactly our multi-million dollar scanners measure. We lack a unifying theory linking information, psychological function, and neuroscientific measurement. We still publish all kinds of voodoo correlations, uncorrected p-values, and poorly operationalized blobfests. Yet, we’ve also laid some of the most important foundational research of our time. In twenty years we’ve mapped a mind boggling array of cognitive function. Some of these attempts at localization may not hold; others may be built on shaky functional definitions or downright poor methods. Even in the face of this uncertainty, the shear number and variety of functions that have been mapped is inspiring. Further, we’ve developed analytic tools to pave the way for an exciting new decade of multi-modal and connectomic research. Developments like resting-state fMRI, optogenetics, real time fMRI, and multi-modal imaging, make for a very exciting time to be a Cognitive Neuroscientist!

Online, things can seem a bit more pessimistic. Snarky methods blogs dedicated to revealing the worst in field tend to do well, and nearly any social-media savy neurogeek will lament the depressing state of science journalism and the brain. While I am also tired of incessantly phrenological, blob-obsessed reports (“research finds god spot in the brain, are your children safe??”) I think we share some of the blame for not communicating properly about what interests and challenges us. For me, some of the most exciting areas of research are those concerning getting straight about what our measurements mean- see the debates over noise in resting state or the neural underpinnings of the BOLD signal for example. Yet these issues are often reported as dry methodological reports, the writers themselves seemingly bored with the topic.

We need to do a better job illustrating to people just how complex and infantile our field is. The big, sexy issues are methodological in nature. They’re also phenomenological in nature. Right now neuroscience is struggling to define itself, unsure if we should be asking our subjects how they feel or anesthetizing them. I believe that if we can illustrate just how tenuous much of our research is, including the really nagging problems, the public will better appreciate seemingly nuanced issues like rest-stimulus interaction and noise-regression.

With that in mind- what are your most exciting questions, right now? What nagging thorn ails you at all steps in your research?

For me, the most interesting and nagging question is, what do people do when we ask them to do nothing? I’m talking about rest-stimulus interaction and mind wandering. There seem to be two prevailing (pro-resting state) views: that default mode network-related activity is related to subjective mind-wandering, and/or that it’s a form of global, integrative, stimulus independent neural variability. On the first view, variability in participants ability to remain on-task drive slow alterations in behavior and stimulus-evoked brain activity. On the other, innate and spontaneous rhythms synchronize large brain networks in ways that alter stimulus processing and enable memory formation. Either way, we’re left with the idea that a large portion of our supposedly well-controlled, stimulus-related brain activity is in fact predicted by uncontrolled intrinsic brain activity. Perhaps even defined by it! When you consider that all this is contingent on the intrinsic activity being real brain activity and not some kind of vascular or astrocyte-driven artifact, every research paradigm becomes a question of rest-stimulus interaction!

So neuroscientists, what keeps you up at night?

A brave new default mode in meditation practitioners- or just confused controls? Review of Brewer (2011)

Given that my own work focuses on cognitive control, intrinsic connectivity, and mental-training (e.g. meditation) I was pretty excited to see Brewer et al’s paper on just these topics appear in PNAS just in time for the winter holidays. I meant to review it straight away but have been buried under my own data analysis until recently. Sadly, when I finally got around to delving into it, my overall reaction was lukewarm at best. Without further ado, my review of:

“Meditation experience is associated with differences in default mode network activity and connectivity

Abstract:

“Many philosophical and contemplative traditions teach that “living in the moment” increases happiness. However, the default mode of humans appears to be that of mind-wandering, which correlates with unhappiness, and with activation in a network of brain areas associated with self-referential processing. We investigated brain activity in experienced meditators and matched meditation-naive controls as they performed several different meditations (Concentration, Loving-Kindness, Choiceless Awareness). We found that the main nodes of the default mode network(medial prefrontal and posterior cingulate cortices) were relatively deactivated in experienced meditators across all meditation types. Furthermore, functional connectivity analysis revealed stronger coupling in experienced meditators between the posterior cingulate, dorsal anterior cingulate, and dorsolateral prefrontal cortices (regions previously implicated in self- monitoring and cognitive control), both at baseline and during meditation. Our findings demonstrate differences in the default-mode network that are consistent with decreased mind-wandering. As such, these provide a unique understanding of possible neural mechanisms of meditation.”

Summary:

Aims: 9/10

Methods: 5/10

Interpretation: 7/10

Importance/Generalizability: 4/10

Overall: 6.25/10

The good: simple, clear cut design, low amount of voodoo, relatively sensible findings

The bad: lack of behavioral co-variates to explain neural data, yet another cross-sectional design

The ugly: prominent reporting of uncorrected findings, comparison of meditation-naive controls to practitioners using meditation instructions (failure to control task demands).

Take-home: Some interesting conclusions, from a somewhat tired and inconclusive design. Poor construction of baseline condition leads to a shot-gun spattering of brain regions with a few that seem interesting given prior work. Let’s move beyond poorly controlled cross-sections and start unravelling the core mechanisms (if any) involved in mindfulness.

Extended Review:
Although this paper used typical GLM and functional connectivity analyses, it loses points in several areas. First, although the authors repeatedly suggest that their “relative paucity of findings” may be “driven by the sensitivity of GLM analysis to fluctuations at baseline… and since meditation practitioners may be (meditating) at baseline…” the contrast would be weak. However, I will side with Jensen et al (2011) here in saying: Meditation naive controls receiving less than 5 minutes of instruction in “focused attention, loving-kindness and choiceless awareness” are simply no controls at all. The argument that the inability of the GLM to detect differences that are quite obviously confounded by a lack of an appropriately controlled baseline is galling at best. This is why we use a GLM-approach; it’s senseless to make conclusions about brain activity when your baseline is no baseline at all. Telling meditation-naive controls to utilize esoteric cultural practices of which they have only just been introduced too, and then comparing that to highly experienced practitioners is a perfect storm of cognitive confusion and poorly controlled demand characteristic. Further, I am disappointed in the review process that allowed the following statement “We found a similar pattern in the medial prefrontal cortex (mPFC), another primary node of the DMN, although it did not survive whole-brain correction for signifigance” followed by this image:

image

These results are then referred to repeatedly in the following discussion. I’m sorry, but when did uncorrected findings suddenly become interpretable? I blame the reviewers here over the authors- they should have known better. The MPFC did not survive correction and hence should not be included in anything other than a explicitly stated as such “exploratory analysis”. In fact it’s totally unclear from the methods section of this paper how these findings where at all discovered: did the authors first examine the uncorrected maps and then re-analyze them using the FWE correction? Or did they reduce their threshold in an exploratory post-hoc fashion? These things make a difference and I’m appalled that the reviewers let the article go to print as it is, when figure 1 and the discussion clearly give the non-fMRI savy reader the impression that a main finding of this study is MPFC activation during meditation. Can we please all agree to stop reporting uncorrected p-values?

I will give the authors this much; the descriptions of practice, and the theoretical guideposts are all quite coherent and well put-together. I found their discussion of possible mechanisms of DMN alteration in meditation to be intriguing, even if I do not agree with their conclusion. Still, it pains me to see a paper with so much potential fail to address the pitfalls in meditation research that should now be well known. Indeed the authors themselves make much ado about how difficult proper controls are, yet seem somehow oblivious to the poorly controlled design they here report. This leads me to my own reinterpretation of their data.

A new default mode, or confused controls?

Brewer et al (2011) report that, when using a verbally guided meditation instruction with meditation naive-controls and experienced practitioners, greater activations in PCC, temporal regions, and for loving-kindness, amygdala are found. Given strong evidence by colleagues Christian Jensen et al (2011) that these kinds of contrasts better represent differences in attentional effort than any mechanism inherent to meditation, I can’t help but wonder if what were seeing here is simply some controls trying to follow esoteric instructions and getting confused in the process. Consider the instruction for the choiceless awareness condition:

“Please pay attention to whatever comes into your awareness, whether it is a thought, emotion, or body sensation. Just follow it until something else comes into your awareness, not trying to hold onto it or change it in any way. When something else comes into your awareness, just pay attention to it until the next thing comes along”

Given that in most contemplative traditions, choiceless awareness techniques are typically late-level advanced practices, in which the very concept of grasping to a stimulus is distinctly altered and laden with an often spiritual meaning, it seems obvious to me that such an instruction constitutes and excellent mindwandering inducement for naive-controls. Do you meditate? I do a little, and yet I find these instructions extremely difficult to follow without essentially sending my mind in a thousand directions. Am I doing this correctly?  When should I shift? Is this a thought or am I just feeling hungry? These things constitute mind-wandering but for the controls, I would argue they constitute following the instructions. The point is that you simply can’t make meaningful conclusions about the neural mechanisms involved in mindfulness from these kinds of instructions.

Finally, let’s examine the functional-connectivity analysis. To be honest, there isn’t a whole lot to report here; the functional connectivity during meditation is perhaps confounded by the same issues I list above, which seems to me a probable cause for the diverse spread of regions reported between controls and meditators. I did find this bit to be interesting:

“Using the mPFC as the seed region, we found increased connectivity with the fusiform gyrus, inferior temporal and parahippocampal gyri, and left posterior insula (among other regions) in meditators relative to controls during meditation (Fig. 3, Fig. S1H, and Table S3). A subset of those regions showed the same relatively increased connectivity in meditators during the baseline period as well (Fig. S1G and Table1)

I found it interesting that the meditation conditions appear to co-activate MPFC and insula, and would love to see this finding replicated in properly controlled design. I also have a nagging wonder as to why the authors didn’t bother to conduct a second-level covariance analysis of their findings with the self-reported mind-wandering scores. If these findings accurately reflect meditation-induced alterations in the DMN, or as the authors more brazenly suggest “a entirely new default network”, wouldn’t we expect their PCC modulations to be predicted by individual variability in mind-wandering self-reports? Of course, we could open the whole can of worms that is “what does it mean when you ask participants if they ‘experienced mind wandering” but I’ll leave that for a future review. At least the authors throw a bone to neurophenomenology, suggesting in the discussion that future work utilize first-person methodology. Indeed.

Last, it occurs to me that the primary finding, of increased DLPFC and ACC in meditation>Controls, also fits well with my intepretation that this design is confounded by demand characteristics. If you take a naive subject and put them in the scanner with these instructions, I’ve argued that their probably going to do something a whole lot like mind-wandering. On the other hand, an experienced practitioner has a whole lot of implicit pressure on them to live up to their tradition. They know what they are their for, and hence they know that they should be doing their thing with as much effort as possible. So what does the contrast meditation>naive really give us? It gives us mind-wandering in the naive group, and increased attentional effort in the practitioner group. We can’t conclude anything from this design regarding mechanisms intrinsic to mindfulness; I predict that if you constructed a similar setting with any kind of dedicated specialist, and gave instructions like “think about your profession, what it means to you, remember a time you did really well” you would see the exact same kind of results. You just can’t compare the uncomparable.

Disclaimer: as usual, I review in the name of science, and thank the authors whole-heartily for the great effort and attention to detail that goes into these projects.  Also it’s worth mentioning that my own research focuses on many of these exact issues in mental training research, and hence i’m probably a bit biased in what I view as important issues.

Slides from my recent Interacting Minds talk

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.

Follow

Get every new post delivered to your Inbox.

Join 13,107 other followers

%d bloggers like this: