Causal emergence in our brains

I recently came across an important paper that I didn't spot when it first appeared in 2013. Tononi and collaborators question the common assumption that knowing everything about the micro level of neurons and their interactions can completely specify the behavior of macro levels of systems of neurons. They use simple simulated systems, including neural-like ones, to show quantitatively that the macro level can causally supersede the micro level, i.e., causal emergence can occur. In practical terms this means, for example, that interactions between nodes in the salience (attentional) or default brain networks that generate our behaviors might be better understood at their level than by knowing everything about the zillions of synapses that compose them. (This perspective is an antidote to the purists who maintain that macro level studies are putting the cart before the horse...not getting us there if we haven't painstakingly worked out the steps of what goes on between ion channels, nerve cells, simple systems of nerve cells, and increasingly higher levels of integration.) My primitive mathematical abilities preclude me from really understanding their computations except in the most general way, I want to pass on their abstract, which is a dense but clear read:

Causal interactions within complex systems can be analyzed at multiple spatial and temporal scales. For example, the brain can be analyzed at the level of neurons, neuronal groups, and areas, over tens, hundreds, or thousands of milliseconds. It is widely assumed that, once a micro level is fixed, macro levels are fixed too, a relation called supervenience. It is also assumed that, although macro descriptions may be convenient, only the micro level is causally complete, because it includes every detail, thus leaving no room for causation at the macro level. However, this assumption can only be evaluated under a proper measure of causation. Here, we use a measure [effective information (EI)] that depends on both the effectiveness of a system’s mechanisms and the size of its state space: EI is higher the more the mechanisms constrain the system’s possible past and future states. By measuring EI at micro and macro levels in simple systems whose micro mechanisms are fixed, we show that for certain causal architectures EI can peak at a macro level in space and/or time. This happens when coarse-grained macro mechanisms are more effective (more deterministic and/or less degenerate) than the underlying micro mechanisms, to an extent that overcomes the smaller state space. Thus, although the macro level supervenes upon the micro, it can supersede it causally, leading to genuine causal emergence—the gain in EI when moving from a micro to a macro level of analysis.

Expensive drugs work better than cheap ones.

Bakalar points to work published in the journal Neurology that found that when Parkinson's disease patients were told they were testing two new drugs, one costing $100 and the other $1500 per dose (both in fact were plain saline solutions), they reported the more expensive drug had almost as much effect as levodopa, the most effective known medication for Parkinson's. Perhaps their hightened expectations of the expensive drug caused them to make more dopamine. (Dopamine levels normally rise in anticipation of pleasure or relief.) The study provides evidence that perception of cost is capable of influencing motor function and brain activation in Parkinson disease.

Computers judge personality more accurately than humans.

This is a bit scary, from Youyou et al.:

Judging others’ personalities is an essential skill in successful social living, as personality is a key driver behind people’s interactions, behaviors, and emotions. Although accurate personality judgments stem from social-cognitive skills, developments in machine learning show that computer models can also make valid judgments. This study compares the accuracy of human and computer-based personality judgments, using a sample of 86,220 volunteers who completed a 100-item personality questionnaire. We show that (i) computer predictions based on a generic digital footprint (Facebook Likes) are more accurate (r = 0.56) than those made by the participants’ Facebook friends using a personality questionnaire (r = 0.49); (ii) computer models show higher interjudge agreement; and (iii) computer personality judgments have higher external validity when predicting life outcomes such as substance use, political attitudes, and physical health; for some outcomes, they even outperform the self-rated personality scores. Computers outpacing humans in personality judgment presents significant opportunities and challenges in the areas of psychological assessment, marketing, and privacy.

Doubting global warming?

My colleague John Young, who is a member of the Univ. of Wisconsin Chaos and Complexity Seminar group I join when I am in Madison, circulated this video to the group. One wishes the current contenders for the Republican presidential candidate nomination, who are either in denial or indifferent to the climate change issue, would have a look. They would probably want to de-fund the climate.gov team that put the video together.
 

Decades ago, the majority of the Arctic's winter ice pack was made up of thick, perennial ice. Today, very old ice is extremely rare. This animation tracks the relative amount of ice of different ages from 1987 through early November 2014. Video produced by the Climate.gov team, based on data provided by Mark Tschudi.

From the more extended description:

This animation tracks the relative amount of ice of different ages from 1987 through early November 2014. The first age class on the scale (1, darkest blue) means "first-year ice,” which formed in the most recent winter. (In other words, it’s in its first year of growth.) The oldest ice (>9, white) is ice that is more than nine years old. Dark gray areas indicate open water or coastal regions where the spatial resolution of the data is coarser than the land map.

As the animation shows, Arctic sea ice doesn't hold still; it moves continually. East of Greenland, the Fram Strait is an exit ramp for ice out of the Arctic Ocean. Ice loss through the Fram Strait used to be offset by ice growth in the Beaufort Gyre, northeast of Alaska. There, perennial ice could persist for years, drifting around and around the basin’s large, looping current.

Around the start of the 21st century, however, the Beaufort Gyre became less friendly to perennial ice. Warmer waters made it less likely that ice would survive its passage through the southernmost part of the gyre. Starting around 2008, the very oldest ice shrank to a narrow band along the Canadian Arctic Archipelago.

A landmark for our human brains.

The search for specifically human cortical landmarks has been frustrating. Reported asymmetries in the planum temporale and the inferior frontal region are not as robust as initially thought and also are observed, less marked, in other primates. Leroy et al. have now identified an asymmetry of the superior temporal sulcus (STS), at the core of our human communication and social cognition systems, that represents a species-specific perisylvian anatomical marker that is barely visible in chimpanzees. They suggest that focusing on gene expression relevant to this regions might shed light on the evolution of our crucial cognitive abilities. Here is their abstract and a figure from the paper:

Identifying potentially unique features of the human cerebral cortex is a first step to understanding how evolution has shaped the brain in our species. By analyzing MR images obtained from 177 humans and 73 chimpanzees, we observed a human-specific asymmetry in the superior temporal sulcus at the heart of the communication regions and which we have named the “superior temporal asymmetrical pit” (STAP). This 45-mm-long segment ventral to Heschl’s gyrus is deeper in the right hemisphere than in the left in 95% of typical human subjects, from infanthood till adulthood, and is present, irrespective of handedness, language lateralization, and sex although it is greater in males than in females. The STAP also is seen in several groups of atypical subjects including persons with situs inversus, autistic spectrum disorder, Turner syndrome, and corpus callosum agenesis. It is explained in part by the larger number of sulcal interruptions in the left than in the right hemisphere. Its early presence in the infants of this study as well as in fetuses and premature infants suggests a strong genetic influence. Because this asymmetry is barely visible in chimpanzees, we recommend the STAP region during midgestation as an important phenotype to investigate asymmetrical variations of gene expression among the primate lineage. This genetic target may provide important insights regarding the evolution of the crucial cognitive abilities sustained by this sulcus in our species, namely communication and social cognition.

Legend - Location of the STAP (yellow) relative to Heschl’s gyrus (blue) and the ventral tip of the central sulcus (green) on both left and right inner cortical surfaces of an individual adult brain. The STAP center is shown by a cross. The black dot with a white contour line shows the planum temporale landmark.  (Click on figure to enlarge.)

Another study on exercise keeping us young - and other fitness trends

Because there are currently no generally agreed on markers of human ageing, Pollock et al. (see review by Reynolds) decided to examine the relationship between age and physiological function by removing inactivity as a factor. They recruited and performed physiological and psychological profiling on a cohort of 55-79 year old very active cyclists. As a group, even the oldest cyclists had younger people’s levels of balance, reflexes, metabolic health and memory ability. Despite studying a large number and diverse range of indices, the authors were not able to identify a physiological marker that could be used to reliably predict the age of a given individual.

Other items from my queue of potential posts:

Reynolds does a review of recent fitness trends such as the super short workout with high intensity bursts, and Brody adds further information on high intensity interval training as an antidote to several chronic ilnesses.

Communicating by having our brains in synchrony.

Stolk et al. have done an interesting experiment by doing MRI scans of people communicating only through a visual display who were working together to complete a task. They found that pair-specific interpersonal synchronization of right temporal lobe activity was driven by communicative episodes in which communicators needed to mutually adjust their conceptualizations of a signal’s use. Thus, it appears that establishing mutual understanding relies on spatially and temporally coherent brain activity between the two people communicating.

Significance

Building on recent electrophysiological evidence showing that novel communicative behavior relies on computations that operate over temporal scales independent from transient sensorimotor behavior, here we report that those computations occur simultaneously in pairs with a shared communicative history, but not in pairs without a shared history. This pair-specific interpersonal synchronization was driven by communicative episodes in which communicators needed to mutually adjust their conceptualizations of a signal’s use. That interpersonal cerebral synchronization was absent when communicators used stereotyped signals. These findings indicate that establishing mutual understanding is implemented through simultaneous in-phase coordination of cerebral activity across communicators, consistent with the notion that pair members temporally synchronize their conceptualizations of a signal’s use.

Abstract

How can we understand each other during communicative interactions? An influential suggestion holds that communicators are primed by each other’s behaviors, with associative mechanisms automatically coordinating the production of communicative signals and the comprehension of their meanings. An alternative suggestion posits that mutual understanding requires shared conceptualizations of a signal’s use, i.e., “conceptual pacts” that are abstracted away from specific experiences. Both accounts predict coherent neural dynamics across communicators, aligned either to the occurrence of a signal or to the dynamics of conceptual pacts. Using coherence spectral-density analysis of cerebral activity simultaneously measured in pairs of communicators, this study shows that establishing mutual understanding of novel signals synchronizes cerebral dynamics across communicators’ right temporal lobes. This interpersonal cerebral coherence occurred only within pairs with a shared communicative history, and at temporal scales independent from signals’ occurrences. These findings favor the notion that meaning emerges from shared conceptualizations of a signal’s use.

Low social status enhances prosocial orientation.

Interesting observations from Guinote et al. :

Humans are a cooperative species, capable of altruism and the creation of shared norms that ensure fairness in society. However, individuals with different educational, cultural, economic, or ethnic backgrounds differ in their levels of social investment and endorsement of egalitarian values. We present four experiments showing that subtle cues to social status (i.e., prestige and reputation in the eyes of others) modulate prosocial orientation. The experiments found that individuals who experienced low status showed more communal and prosocial behavior, and endorsed more egalitarian life goals and values compared with those who experienced high status. Behavioral differences across high- and low-status positions appeared early in human ontogeny (4–5 y of age).

This is yet another study using undergraduate college students as subjects. The first experiment manipulated perceived status by telling students their department had high versus low national rankings. After this simple intervention, lower status students showed more helpful behavior when an experimenter pretended to drop a pack of pens on the floor. A second experiment gave a group bogus feedback about their group standing compared with another group. Individuals in low status groups showed more communal and prosocial signaling during self-presentations and interactions than those in high status groups. The third experiment had a status manipulation similar to the first, and the life goals of low versus high status subjects were probed, the finding being that lower lower status participants indicated more benevolent self-transcendent life goals while higher-status participants endorsed more power values. The fourth study was done with a group of 28 children of mean age 4.7 years. After manipulations of their dominance hierarchy, lower status children were more generous and helpful than higher status peers.

Parallel brain systems regulate our pain.

Our subjective sensory experiences are regulated by defined brain areas subh visual cortex, auditory cortex,somatosensory cortex, etc., but there doesn't appear to be a "pain cortex" that directly codes our subjective perception of pain. Mano and Seymour, in a review of Woo et al., note the emerging concept that pain might emerge from the coordinated activity of an integrated brain network. Woo et al. provide evidence that distinct brain networks support the subjective changes in pain that result from nociceptive input and self-directed cognitive modulation. Their abstract, followed by a summary graphic from Mano and Seymour:

Cognitive self-regulation can strongly modulate pain and emotion. However, it is unclear whether self-regulation primarily influences primary nociceptive and affective processes or evaluative ones. In this study, participants engaged in self-regulation to increase or decrease pain while experiencing multiple levels of painful heat during functional magnetic resonance imaging (fMRI) imaging. Both heat intensity and self-regulation strongly influenced reported pain, but they did so via two distinct brain pathways. The effects of stimulus intensity were mediated by the neurologic pain signature (NPS), an a priori distributed brain network shown to predict physical pain with over 90% sensitivity and specificity across four studies. Self-regulation did not influence NPS responses; instead, its effects were mediated through functional connections between the nucleus accumbens and ventromedial prefrontal cortex. This pathway was unresponsive to noxious input, and has been broadly implicated in valuation, emotional appraisal, and functional outcomes in pain and other types of affective processes. These findings provide evidence that pain reports are associated with two dissociable functional systems: nociceptive/affective aspects mediated by the NPS, and evaluative/functional aspects mediated by a fronto-striatal system.

Distinct component to the subjective perception of pain. Core nociceptive nodes comprise a multivariate pattern (the neurological pain signature [NPS]), and fronto-striatal brain regions comprise an evaluative pathway sensitive to self-directed cognitive modulation.

Power and your voice.

Margaret Thatcher did it, and so can you. She went through voice training that permitted her to exude a more authoritative powerful persona. Her voice became higher in pitch and loudness variability but lower in pitch variability, like playing a piano with a smaller number of notes, but varying their volume more. Ko et al. report a similar transformation in the usual cadre of college undergraduates recruited for an experiment. Here is a description of the experiments provided by an APS summary:

In the first experiment, they recorded 161 college students reading a passage aloud; this first recording captured baseline acoustics. The participants were then randomly assigned them to play a specific role in an ensuing negotiation exercise.

Students assigned to a “high” rank were told to go into the negotiation imagining that they either had a strong alternative offer, valuable inside information, or high status in the workplace, or they were asked to recall an experience in which they had power before the negotiation started. Low-rank students, on the other hand, were told to imagine they had either a weak offer, no inside information, or low workplace status, or they were asked to recall an experience in which they lacked power.

The students then read a second passage aloud, as if they were leading off negotiations with their imaginary adversary, and their voices were recorded. Everyone read the same opening, allowing the researchers to examine acoustics while holding the speech content constant across all participants.

Comparing the first and second recordings, the researchers found that the voices of students assigned to high-power roles tended to go up in pitch, become more monotone (less variable in pitch), and become more variable in loudness than the voices of students assigned low-power roles.

And the students’ vocal cues didn’t go unnoticed. A second experiment with a separate group of college students revealed that listeners, who had no knowledge of the first experiment, were able to pick up on these power-related vocal cues to determine who did and did not have power: Listeners ranked speakers who had been assigned to the high-rank group as more likely to engage in high-power behaviors, and they were able to categorize whether a speaker had high or low rank with considerable accuracy.

In line with the vocal changes observed in the first experiments, listeners tended to associate higher pitch and voices that varied in loudness with high-power behaviors. They also associated louder voices with higher power.

Musical training accelerates cortical thickness maturation.

Hudziak et al. have examined a database of MRI scans of 232 youths ranging from 6 to 18 years of age, obtained over a period of years. Their analysis revealed that music training was associated with an increased rate of cortical thickness maturation.  Clips from their discussion and a figure:

Music training was associated with the rate of cortical thickness maturation in a number of brain areas distributed throughout the right premotor and primary cortices, the left primary and supplementary motor cortices, bilateral parietal cortices, bilateral orbitofrontal cortices, as well as bilateral parahippocampal gyri. Our finding that music training was associated with cortical thickness development in the premotor and primary motor cortices is not surprising, given that both regions contribute to the control and execution of movement.

Music training was also found to influence cortical thickness maturation within aspects of the DLPFC. Myriad imaging and neuropsychological studies have implicated the DLPFC in aspects of executive functioning, including working memory, attentional control, as well as organization and planning for the future. Interestingly, developmental structural neuroimaging studies have shown that participants with quantitatively higher scores on attention problems exhibit delayed cortical thickness maturation in portions of the DLPFC as well as other cortical regions.

Brain areas where local cortical thickness is associated with the “Age × Years of Playing” interaction (N = 232; 334 time points)

Judging and adapting to norm violations engage different brain regions.

Gu et al. find that our insula is critical for learning to adapt when reality deviates from norm expectations, and the ventromedial prefrontal cortex is important for valuation of fairness during social exchange.

Social norms and their enforcement are fundamental to human societies. The ability to detect deviations from norms and to adapt to norms in a changing environment is therefore important to individuals' normal social functioning. Previous neuroimaging studies have highlighted the involvement of the insular and ventromedial prefrontal (vmPFC) cortices in representing norms. However, the necessity and dissociability of their involvement remain unclear. Using model-based computational modeling and neuropsychological lesion approaches, we examined the contributions of the insula and vmPFC to norm adaptation in seven human patients with focal insula lesions and six patients with focal vmPFC lesions, in comparison with forty neurologically intact controls and six brain-damaged controls. There were three computational signals of interest as participants played a fairness game (ultimatum game): sensitivity to the fairness of offers, sensitivity to deviations from expected norms, and the speed at which people adapt to norms. Significant group differences were assessed using bootstrapping methods. Patients with insula lesions displayed abnormally low adaptation speed to norms, yet detected norm violations with greater sensitivity than controls. Patients with vmPFC lesions did not have such abnormalities, but displayed reduced sensitivity to fairness and were more likely to accept the most unfair offers. These findings provide compelling computational and lesion evidence supporting the necessary, yet dissociable roles of the insula and vmPFC in norm adaptation in humans: the insula is critical for learning to adapt when reality deviates from norm expectations, and that the vmPFC is important for valuation of fairness during social exchange.

Subjective status shapes political preferences.

Brown-Iannuzzi et al. suggest that people's subjective perception of their socioeconomic status (SES) has a large influence on whether they support wealth redistribution as a remedy for increasing economic inequality in America. This is distinct from attitudes based on economic ideologies and economic self-interest. Here is their abstract, followed by their description of their studies:

Economic inequality in America is at historically high levels. Although most Americans indicate that they would prefer greater equality, redistributive policies aimed at reducing inequality are frequently unpopular. Traditional accounts posit that attitudes toward redistribution are driven by economic self-interest or ideological principles. From a social psychological perspective, however, we expected that subjective comparisons with other people may be a more relevant basis for self-interest than is material wealth. We hypothesized that participants would support redistribution more when they felt low than when they felt high in subjective status, even when actual resources and self-interest were held constant. Moreover, we predicted that people would legitimize these shifts in policy attitudes by appealing selectively to ideological principles concerning fairness. In four studies, we found correlational (Study 1) and experimental (Studies 2–4) evidence that subjective status motivates shifts in support for redistributive policies along with the ideological principles that justify them.

In Study 1, we measured subjective and objective SES and predicted that higher subjective SES would be associated with greater opposition to redistributive policies, independently of objective SES. In Study 2, we manipulated subjective SES, hypothesizing that participants induced to feel high status would be less supportive of redistribution and would endorse a more conservative ideology to justify that position than would participants induced to feel low status. In Study 3, we gained greater experimental control by creating an economic game in which players earned money and a portion of the profits of high earners were redistributed to low earners. We manipulated how well participants performed relative to other players, and we predicted that players who performed better would support less redistribution and would justify their preferences on the basis of ideological principles. In Study 4, we sought to replicate this finding and investigated whether the manipulation of subjective status led high-status participants to perceive other participants who disagreed with them as biased by self-interest. Together, these studies investigated whether subjective status may lead to political division.

[The results provide evidence] that perceptions of relative status can cause changes in political preferences. In Study 1, feeling higher in relative status was associated with lower support for redistribution. In Study 2, feeling higher in status caused reduced support for redistribution. In Study 3, we manipulated relative status in the context of an economic game and obtained similar results. Although participants could not profit from their recommendations, they recommended rule changes to reduce redistribution when they believed they had outperformed most other players. These changes were accompanied by shifts in construals of what counts as fair. Study 4 replicated these effects and showed that participants’ status affected their perceptions of bias in another player. High-status participants thought a player who recommended increased redistribution was more biased by self-interest than a player who recommended cutting redistribution. Together, these results suggest that subjective feelings of status can drive opinions toward redistribution, along with ideological views that justify those positions. An implication of the present work is that growing subjective perceptions of class differences may drive increased political polarization.

We can see in the infrared!

The major part of my professional life was spent doing research on how the rod cells in our retinas change light into a nerve signal. (I just got a request from ResearchGate, a site on which scientists list their work, suggesting that I upload another of my old vision articles, in this case one that appeared in Nature - in 1965 - 50 years ago! - titled "Reaction of the Rhodopsin Chromophore with Sodium Borohydride".) Even though for the past 20 years or so I have focused on the topics covered by MindBlog I occasionally see a vision article that takes me back to 'the old days'. A colleague from those days (Krzysztof Palczewski) and collaborators have recently done a nice piece of work demonstrating that we can actually expand our vision beyond the normal "visible" range of 400 (blue) to 720 (red) nanometer (nm) wavelengths into the higher frequency (lower energy) infrared regions emitted by infrared lasers. It turns out that the Rhodopsin Chromophore of my article above, retinal, which normally has its shape changed (isomerized) by absorbing one photon of visible light, can be activated by a two-photon chromophore isomerization, especially at wavelengths above 900 nm. From their significance and abstract statements:

This study resolves a long-standing question about the ability of humans to perceive near infrared radiation (IR) and identifies a mechanism driving human IR vision. A few previous reports and our expanded psychophysical studies here reveal that humans can detect IR at wavelengths longer than 1,000 nm and perceive it as visible light, a finding that has not received a satisfactory physical explanation. We show that IR light activates photoreceptors through a nonlinear optical process.

Vision relies on photoactivation of visual pigments in rod and cone photoreceptor cells of the retina. The human eye structure and the absorption spectra of pigments limit our visual perception of light. Our visual perception is most responsive to stimulating light in the 400- to 720-nm (visible) range. First, we demonstrate by psychophysical experiments that humans can perceive infrared laser emission as visible light. Moreover, we show that mammalian photoreceptors can be directly activated by near infrared light with a sensitivity that paradoxically increases at wavelengths above 900 nm, and display quadratic dependence on laser power, indicating a nonlinear optical process. Biochemical experiments with rhodopsin, cone visual pigments, and a chromophore model compound 11-cis-retinyl-propylamine Schiff base demonstrate the direct isomerization of visual chromophore by a two-photon chromophore isomerization. Indeed, quantum mechanics modeling indicates the feasibility of this mechanism. Together, these findings clearly show that human visual perception of near infrared light occurs by two-photon isomerization of visual pigments.

Steven Pinker's "Sense of Style"

I've just read through Steven Pinker's new book "The Sense of Style: The Thinking Person's Guide to Writing in the 21st Century." It is a lucid exposition, and I wish that I were disciplined enough to heed its exhortations on substance and clarity. I can't resist passing on the following clips from Chapter 2, the second paragraph in particular grabs me.:

Writing is an unnatural act. As Charles Darwin observed, “Man has an instinctive tendency to speak, as we see in the babble of our young children, whereas no child has an instinctive tendency to bake, brew, or write.” The spoken word is older than our species, and the instinct for language allows children to engage in articulate conversation years before they enter a schoolhouse. But the written word is a recent invention that has left no trace in our genome and must be laboriously acquired throughout childhood and beyond.

At the time that we write, the reader exists only in our imaginations. Writing is above all an act of pretense. We have to visualize ourselves in some kind of conversation, or correspondence, or oration, or soliloquy, and put words into the mouth of the little avatar who represents us in this simulated world. The key to good style, far more than obeying any list of commandments , is to have a clear conception of the make-believe world in which you’re pretending to communicate.

Which simulation should a writer immerse himself in when composing a piece for a more generic readership, such as an essay, an article, a review, an editorial, a newsletter, or a blog post? The literary scholars Francis-Noël Thomas and Mark Turner have singled out one model of prose as an aspiration for such writers today. They call it classic style, and explain it in a wonderful little book called Clear and Simple as the Truth.

The guiding metaphor of classic style is seeing the world. The writer can see something that the reader has not yet noticed, and he orients the reader’s gaze so that she can see it for herself. The purpose of writing is presentation, and its motive is disinterested truth. It succeeds when it aligns language with the truth, the proof of success being clarity and simplicity. The truth can be known, and is not the same as the language that reveals it; prose is a window onto the world. The writer knows the truth before putting it into words; he is not using the occasion of writing to sort out what he thinks. Nor does the writer of classic prose have to argue for the truth; he just needs to present it. That is because the reader is competent and can recognize the truth when she sees it, as long as she is given an unobstructed view. The writer and the reader are equals, and the process of directing the reader’s gaze takes the form of a conversation.

The signature of consciousness in resting-state brain activity.

I've done a number of posts on attentional or salience versus default mode long-range connectivity networks in our brains (for a review see my lecture.) They correspond roughly to supporting outward task oriented processes versus inward processes such as daydreaming or imagining. Activity in these networks is thought to be a marker of consciousness, but this idea conflicts with observations that long-range functional connectivities persist even after loss of consciousness caused by anesthesia, or in vegetative state patients. This post is to point to recent work by Dehaene and collaborators showing clear difference in the behavior of long-range networks in awake and anesthetized monkeys. Their abstract and statement of significance, followed by a movie showing whole brain connectivity patterns at different time points in the awake monkey.

Significance

What are the origins of resting-state functional connectivity patterns? One dominating view is that they index ongoing cognitive processes. However, this conclusion is in conflict with studies showing that long-range functional connectivity persists after loss of consciousness, possibly reflecting structural connectivity maps. In this work we respond to this question showing that in fact both sources have a clear and separable contribution to resting-state patterns. We show that under anesthesia, the dominating functional configurations have low information capacity and lack negative correlations. Importantly, they are rigid, tied to the anatomical map. Conversely, wakefulness is characterized by the dynamical exploration of a rich, flexible repertoire of functional configurations. These dynamical properties constitute a signature of consciousness.

Abstract

At rest, the brain is traversed by spontaneous functional connectivity patterns. Two hypotheses have been proposed for their origins: they may reflect a continuous stream of ongoing cognitive processes as well as random fluctuations shaped by a fixed anatomical connectivity matrix. Here we show that both sources contribute to the shaping of resting-state networks, yet with distinct contributions during consciousness and anesthesia. We measured dynamical functional connectivity with functional MRI during the resting state in awake and anesthetized monkeys. Under anesthesia, the more frequent functional connectivity patterns inherit the structure of anatomical connectivity, exhibit fewer small-world properties, and lack negative correlations. Conversely, wakefulness is characterized by the sequential exploration of a richer repertoire of functional configurations, often dissimilar to anatomical structure, and comprising positive and negative correlations among brain regions. These results reconcile theories of consciousness with observations of long-range correlation in the anesthetized brain and show that a rich functional dynamics might constitute a signature of consciousness, with potential clinical implications for the detection of awareness in anesthesia and brain-lesioned patients.

Dynamical connectivity matrix - red lines mark positive correlations, and blue lines mark negative correlations.

Body movements shape brain representation of musical rhythms.

Entraining our movement to music is a universal human behavior. The enhancement of social cohesion by group movements in synchrony with the rhythms of chants and songs could have had an adaptive value in human evolution. Chemin et al. have done the interesting experiment of recording EEG evoked potentials caused by study participants listening to an ambiguous rhythm, before and after a body-movement session designed to disambiguate the perception of this rhythm by favoring a specific meter (e.g., two beats per measure vs. three beats per measure). They found that the brain responses to the rhythm after body movement were significantly enhanced at frequencies related to the meter to which the participants had moved. Here is their abstract:

It is increasingly recognized that motor routines dynamically shape the processing of sensory inflow (e.g., when hand movements are used to feel a texture or identify an object). In the present research, we captured the shaping of auditory perception by movement in humans by taking advantage of a specific context: music. Participants listened to a repeated rhythmical sequence before and after moving their bodies to this rhythm in a specific meter. We found that the brain responses to the rhythm (as recorded with electroencephalography) after body movement were significantly enhanced at frequencies related to the meter to which the participants had moved. These results provide evidence that body movement can selectively shape the subsequent internal representation of auditory rhythms.

An Example of Publication Bias - Cognitive Advantage in Bilingualism

MindBlog has done several posts on experiments that reinforce what has become the conventional wisdom regarding bilingualism: that it enhances our executive control faculties. De Bruin et al., noting that they themselves had chosen to report positive results supporting this conclusion, but had not followed through on negative data (the file drawer effect), thought to do a systematic analysis of the publication fate of experiments with positive, mixed, or negative outcomes. They searched for conference abstracts on bilingualism and executive control in 169 conferences (31 different national and international meetings) organized between 1999 and 2012, and identified 128 abstracts (presented at 52 different conferences) that focused on bilingualism and executive control. Their result:

Sixty-eight percent of the studies that clearly found a bilingual advantage were published, compared with 50% of the studies that found mixed results supporting the bilingual-advantage theories, 39% of the studies that found mixed results partly challenging those theories, and 29% of the studies that found no differences between monolinguals and bilinguals or found a bilingual disadvantage. On the whole, 63% of the studies supporting the bilingual advantage were published, compared with only 36% of the studies that challenged it.

From the authors discussion:

This difference in publication percentage based on the outcomes of the study could be the result of a bias during several steps of the publication process: Authors, reviewers, and editors can decide to submit or accept only studies that showed positive results. In the first step of the publication process, the file-drawer problem could play an important role in the observed publication bias. Authors could decide not to publish studies with null or mixed results, or they could choose to submit their results only partially, for example, by leaving out tasks that did not show an effect of bilingualism. The article by Treccani et al. (2009)[Treccani is a co-author of the current paper] is an example of the file-drawer problem, as it excluded the experiments that did not show an effect of bilingualism.

On the next level, reviewers and editors might reject manuscripts reporting null, negative, or mixed results more often than manuscripts reporting positive effects. This rejection is often based on the argument that null effects are difficult to interpret, or the result of poor stimulus design... Mahoney (1977) asked journal reviewers to referee manuscripts reporting positive, negative, mixed, or null results with identical methodological procedures. Although the methodology was the same, reviewers scored the manuscripts reporting positive results as methodologically better than the manuscripts reporting negative or mixed results. For manuscripts with positive results, reviewers usually recommended acceptance with moderate revisions. For manuscripts with negative results, however, their usual recommendation was major revision or rejection. Manuscripts with mixed results were mostly rejected.

Watching brain oscillations drive perception.

Are the electrical oscillations observed in EEG recordings as we perceive images simply correlations, reflecting brain processes driving our visual experience, or are the oscillations themselves causal, driving the visual experience? Helfrich et al. address this basic question in a clever experiment in which they force brain oscillations of the left and right visual hemispheres into synchrony using transcranial alternating current stimulation. This causes human subjects to more often perceive an ambiguous figure in one of its perceptual instantiations, showing that the oscillations are driving the visual experience, not vice versa. Their summary:

Brain activity is profoundly rhythmic and exhibits seemingly random fluctuations across a very broad frequency range (less than 0.1 Hz to greater than 600 Hz). Recently, it has become evident that these brain rhythms are not just a generic sign of the brain-at-work, but actually reflect a highly flexible mechanism for information encoding and transfer. In particular, it has been suggested that oscillatory synchronization between different areas of the cortex underlies the establishment of task-relevant networks. Here, we investigated whether gamma-band synchronization (~40 Hz) is causally involved in the integration between the two brain hemispheres of alternating visual tokens into a coherent motion percept. We utilized transcranial alternating current stimulation (tACS), a novel non-invasive brain stimulation technique, which allows frequency-specific entrainment of cortical areas. In a combined tACS-electroencephalography study, we selectively up- and down-regulated interhemispheric coherence, resulting in a directed bias in apparent motion perception: Increased interhemispheric connectivity sustained the horizontal motion percept, while decreased connectivity reinforced the vertical percept. Thus, our data suggest that the level of interhemispheric gamma-band coherence directly influenced the instantaneous motion percept. From these results, we conclude that synchronized neuronal activity is essential for conscious perception and cognition.

Perceived control promotes persistence and influences brain response to setbacks

From Bhanji et al:

Highlights

•We report two distinct neural mechanisms for persistence through adversity 

•Perceiving control over setbacks increases persistence 

•Striatum activity relates to persisting after setbacks by correcting mistakes 

•Ventromedial prefrontal activity mediates effects of negative affect on persistence

Summary

How do people cope with setbacks and persist with their goals? We examine how perceiving control over setbacks alters neural processing in ways that increase persistence through adversity. For example, a student might retake a class if initial failure was due to controllable factors (e.g., studying) but give up if failure was uncontrollable (e.g., unfair exam questions). Participants persisted more when they perceived control over setbacks, and when they experienced increased negative affect to setbacks. Consistent with previous observations involving negative outcomes, ventral striatum and ventromedial prefrontal (VMPFC) activity was decreased in response to setbacks. Critically, these structures represented distinct neural mechanisms for persistence through adversity. Ventral striatum signal change to controllable setbacks correlated with greater persistence, whereas VMPFC signal change to uncontrollable setbacks mediated the relationship between increased negative affect and persistence. Taken together, the findings highlight how people process setbacks and adapt their behavior for future goal pursuit.

From Whalen and Kelly's review :

The vmPFC is necessary for regulating our emotional responses...in the present study, the negative affect change is the catalyst that kicks vmPFC into a higher gear and effects adaptive change (i.e., persistence)...when negative affect accompanies uncontrollable setbacks, as is often the case, the vmPFC activity is necessary to adapt to the emotional reaction and, in so doing, preserve persistence.

The ventral striatum on the other hand is important for signaling prediction errors when behavioral outcomes do not match our expectations...when we believe we have control over situations, the ventral striatum can use value signals to motivate future behavior...this striatal effect is problem focused compared to the prefrontal effect that is more emotion focused.

A fetching point about Paul Whalen's and William Kelley's review is that it starts with the example of two professors currently employed at Dartmouth College.

One applied, and he was hired on his very first try (we’ll call him Bill in this example). Imagine that the other; well, he needed more chances before his eventual hire (we’ll call him P.W. to protect his identity). What dictates whether someone will persist when they encounter a setback? Is it the person who remains calm in the moment, not letting this single event rattle her? Or is it the person who reacts strongly to defeat and heavily reinvests in the project, determined to change things the next time? To borrow from Shakespeare, tell us where is persistence bred, or in the heart, or in the head (The Merchant of Venice, 3.2)? ...Bhanji and Delgado (2014) provide clear evidence of the latter.

Guess who Bill and P.W. actually are!