The gut microbiome has important effects on human health, yet its importance in human ageing remains unclear. In the present study, we demonstrate that, starting in mid-to-late adulthood, gut microbiomes become increasingly unique to individuals with age. We leverage three independent cohorts comprising over 9,000 individuals and find that compositional uniqueness is strongly associated with microbially produced amino acid derivatives circulating in the bloodstream. In older age (over ~80 years), healthy individuals show continued microbial drift towards a unique compositional state, whereas this drift is absent in less healthy individuals. The identified microbiome pattern of healthy ageing is characterized by a depletion of core genera found across most humans, primarily Bacteroides. Retaining a high Bacteroides dominance into older age, or having a low gut microbiome uniqueness measure, predicts decreased survival in a 4-year follow-up. Our analysis identifies increasing compositional uniqueness of the gut microbiome as a component of healthy ageing, which is characterized by distinct microbial metabolic outputs in the blood.
Monday, August 02, 2021
Friday, July 30, 2021
This open source article from Dong et al. has some excellent summary graphics:
Here, we describe age-dependent shifts in the macroscale organization of cortex in childhood and adolescence. The characterization of functional connectivity patterns in children revealed an overarching organizational framework anchored within the unimodal cortex, between somatosensory/motor and visual regions. Conversely, in adolescents, we observed a transition into an adult-like gradient, situating the default network at the opposite end of a spectrum from primary somatosensory/motor regions. This spatial framework emerged gradually with age, reaching a sharp inflection point at the transition from childhood to adolescence. These data reveal a developmental change from a functional motif first dominated by the distinction between sensory and motor systems and then balanced through interactions with later-maturing aspects of association cortex that support more abstract cognitive functions.Abstract
The transition from childhood to adolescence is marked by pronounced shifts in brain structure and function that coincide with the development of physical, cognitive, and social abilities. Prior work in adult populations has characterized the topographical organization of the cortex, revealing macroscale functional gradients that extend from unimodal (somatosensory/motor and visual) regions through the cortical association areas that underpin complex cognition in humans. However, the presence of these core functional gradients across development as well as their maturational course have yet to be established. Here, leveraging 378 resting-state functional MRI scans from 190 healthy individuals aged 6 to 17 y old, we demonstrate that the transition from childhood to adolescence is reflected in the gradual maturation of gradient patterns across the cortical sheet. In children, the overarching organizational gradient is anchored within the unimodal cortex, between somatosensory/motor and visual territories. Conversely, in adolescence, the principal gradient of connectivity transitions into an adult-like spatial framework, with the default network at the opposite end of a spectrum from primary sensory and motor regions. The observed gradient transitions are gradually refined with age, reaching a sharp inflection point in 13 and 14 y olds. Functional maturation was nonuniformly distributed across cortical networks. Unimodal networks reached their mature positions early in development, while association regions, in particular the medial prefrontal cortex, reached a later peak during adolescence. These data reveal age-dependent changes in the macroscale organization of the cortex and suggest the scheduled maturation of functional gradient patterns may be critically important for understanding how cognitive and behavioral capabilities are refined across development.
Wednesday, July 28, 2021
To hopefully enhance the chance that you will pay attention to the creative and seminal thinking in the open source Laukkonen and Slagter review article whose abstract I passed on in my July 21 post, I now pass on their striking concluding statement and then two graphics whose legends summarize the main ideas presented. I think this work offers a plausible and appealing integration of neuroscience and meditative traditions.
We have taken on the daunting task of providing a theory for understanding the effects of meditation within the predictive processing framework. Contemplative science is a young field and predictive processing is a new theory, although both have roots going much farther back. All theories are subject to change, but perhaps particularly so for such new domains of enquiry. Nevertheless, we think the conditions are suitable for a more overarching theory that may also thwart further siloing and fragmentation of scientific research, as has been commonplace among the mind-sciences. A strength of our framework is its simplicity: Being in the here and now reduces predictive processing. And yet, this basic idea can explain how each meditation technique uniquely deconstructs the minds tendency to project the past onto the present, how certain insights may arise, the nature of hierarchical self-processing, and the plasticity of the human mind. There is scope here, we think, to eventually reveal what makes a meditator an expert, why meditation has such broad clinical effects, and how we might begin mitigating some of the negative consequences of meditation. Last but not least, our framework seems to bring ancient Eastern and modern scientific ideas closer together, showing how the notion of conditioned experience in Buddhism aligns with the notion of the experience-dependent predictive brain.
Fig. 1. Here we use the Pythagoras Tree to provide an intuitive illustration of how organisms represent the world with increasing counterfactual depth or abstraction. The tree is constructed using squares that are scaled down by the square root of 2 divided by 2 and placed such that the corners of the squares meet and form a triangle between them, recursively. Analogously, the brain constructs experience from temporally precise and unimodal models of present-moment sensory representations and input (e.g., pixels on a screen), into ever more abstract, transmodal, and temporally deep models (e.g., a theory paper). Meditation brings one increasingly into the present moment, thus reducing the tendency to conceptualize away from the here and now, akin to observing the pixels rather than the words. This reduction of conceptualization ought to also have profound effects on the sense of self, which also relies on abstract model building, and ultimately is said to reveal an underlying seemingly “unconditioned” state of consciousness as such (like the white background underlying the pixels).
Fig. 2. In this schematic we illustrate two aspects of the many-to-(n)one model. The first and most foundational proposal is that meditation gradually flattens the predictive hierarchy or ‘prunes the counterfactual tree’, by bringing the meditator into the here and now, illustrated in the left figure. Thus, meditative depth is defined by the extent that the organism is not constructing temporally thick predictions. In the right figure, we dissect the predictive hierarchy into three broad levels. We propose that thinking (and therefore the narrative self [NS]) sits at the top of the predictive hierarchy (Carhart-Harris and Friston, 2010, 2019). Sensing and perceiving and therefore the embodied experiencing self [ES] sits below it (Gallagher, 2000; Seth, 2013). Finally, a basal form of self-hood characterized by the subject-object [S/O] duality sits at the earliest level. FA brings the practitioner out of the narrative self and into a more experiencing and embodied mode of being. Then, through dereification from present moment experience (including bodily sensations) OM brings the practitioner more into a state where contents of experience are treated equally, and one is able to experience non-judgmentally (sensing without appraisal), but even in very advanced states, a subject-object duality remains. During OM, certain epistemic discoveries or insights about the nature and behavior of generative models may occur. Finally, through ND practices the subject-object distinction may fall away and the background or “groundless ground” of all experience—awareness itself—can be uncovered. Another way to characterize this process is as follows: FA employs regular (conditional) attention to an object of sensing, OM employs bare (unconditional) attention, and ND practice employs reflexive awareness that permits the non-dual witnessing of the subject-object dichotomy and finally pure or non-dual awareness by releasing attention altogether.
Monday, July 26, 2021
Infants look longer at impossible or unlikely events than at possible events. While these responses to expectancy violations have been critical for understanding early cognition, interpreting them is challenging because infants’ responses are highly variable. This variability has been treated as an unavoidable nuisance inherent to infant research. Here we asked whether the variability contains signal in addition to noise: namely, whether some infants show consistently stronger responses to expectancy violations than others. Infants watched two unrelated physical events 6 mo apart; these events culminated in either an impossible or an expected outcome. We found that infants who exhibited the strongest looking response to an impossible event at 11 mo also exhibited the strongest response to an entirely different impossible event at 17 mo. Furthermore, violation-of-expectation responses in infancy predicted children’s explanation-based curiosity at 3 y old. In contrast, there was no longitudinal relation between infants’ responses to events with expected outcomes at 11 and 17 mo, nor any link with later curiosity; hence, infants’ responses do not merely reflect individual differences in attention but are specific to expectancy violations. Some children are better than others at detecting prediction errors—a trait that may be linked to later cognitive abilities.
Friday, July 23, 2021
The posteromedial cortex (PMC) is known to be a core node of the default mode network. Given its anatomical location and blood supply pattern, the effects of targeted disruption of this part of the brain are largely unknown. Here, we report a rare case of a patient (S19_137) with confirmed seizures originating within the PMC. Intracranial recordings confirmed the onset of seizures in the right dorsal posterior cingulate cortex, adjacent to the marginal sulcus, likely corresponding to Brodmann area 31. Upon the onset of seizures, the patient reported a reproducible sense of self-dissociation—a condition he described as a distorted awareness of the position of his body in space and feeling as if he had temporarily become an outside observer to his own thoughts, his “me” having become a separate entity that was listening to different parts of his brain speak to each other. Importantly, 50-Hz electrical stimulation of the seizure zone and a homotopical region within the contralateral PMC induced a subjectively similar state, reproducibly. We supplement our clinical findings with the definition of the patient’s network anatomy at sites of interest using cortico-cortical–evoked potentials, experimental and resting-state electrophysiological connectivity, and individual-level functional imaging. This rare case of patient S19_137 highlights the potential causal importance of the PMC for integrating self-referential information and provides clues for future mechanistic studies of self-dissociation in neuropsychiatric populations.
Wednesday, July 21, 2021
I had a chat with my former University of Wisconsin colleague Richard Davidson during my visit to Madison, WI last week, and he pointed me to an excellent open source review article by Laukkonen and Slagter, From many to (n)one: Meditation and the plasticity of the predictive mind. They offer an integrated predictive processing account of three main styles of meditation. I just finished reading through their lucid account and plan to carefully re-read it several times. I pass on the summary points and abstract:
• Predictive processing provides a novel theoretical window on meditation.
• Deconstructive meditations progressively reduce temporally deep processing.
• Insight experiences arise during meditation due to Bayesian model reduction
• Meditation deconstructs self models by reducing abstract processing.
• Non-dual awareness or pure consciousness is the ‘here and now’.Abstract
How profoundly can humans change their own minds? In this paper we offer a unifying account of deconstructive meditation under the predictive processing view. We start from simple axioms. First, the brain makes predictions based on past experience, both phylogenetic and ontogenetic. Second, deconstructive meditation brings one closer to the here and now by disengaging anticipatory processes. We propose that practicing meditation therefore gradually reduces counterfactual temporally deep cognition, until all conceptual processing falls away, unveiling a state of pure awareness. Our account also places three main styles of meditation (focused attention, open monitoring, and non-dual) on a single continuum, where each technique relinquishes increasingly engrained habits of prediction, including the predicted self. This deconstruction can also permit certain insights by making the above processes available to introspection. Our framework is consistent with the state of empirical and (neuro)phenomenological evidence and illuminates the top-down plasticity of the predictive mind. Experimental rigor, neurophenomenology, and no-report paradigms are needed to further understanding of how meditation affects predictive processing and the self.
Monday, July 19, 2021
Interesting results from Shao et al.:
• Psilocybin ameliorates stress-related behavioral deficit in mice
• Psilocybin increases spine density and spine size in frontal cortical pyramidal cells
• Psilocybin-evoked structural remodeling is persistent for at least 1 month
• The dendritic rewiring is accompanied by elevated excitatory neurotransmissionSummary
Psilocybin is a serotonergic psychedelic with untapped therapeutic potential. There are hints that the use of psychedelics can produce neural adaptations, although the extent and timescale of the impact in a mammalian brain are unknown. In this study, we used chronic two-photon microscopy to image longitudinally the apical dendritic spines of layer 5 pyramidal neurons in the mouse medial frontal cortex. We found that a single dose of psilocybin led to ∼10% increases in spine size and density, driven by an elevated spine formation rate. The structural remodeling occurred quickly within 24 h and was persistent 1 month later. Psilocybin also ameliorated stress-related behavioral deficit and elevated excitatory neurotransmission. Overall, the results demonstrate that psilocybin-evoked synaptic rewiring in the cortex is fast and enduring, potentially providing a structural trace for long-term integration of experiences and lasting beneficial actions.Graphical Abstract:
Friday, July 16, 2021
Thursday, July 15, 2021
The brilliant evolutionary insights of Darwin and others have revolutionized our understanding of the world. Darwin was impressed by the “tangled bank” of elaborate forms that emerged from the undirected processes of evolution to produce the complexity of the biological world. Through continuous innovation coupled with the deceptively simple filter known as natural selection, the characteristics of species and their interactions change in response to changing environments. However, evolution is not limited only to the biological world. Wherever the evolutionary forces of reproduction, variation, and selection exist—as they do in financial markets—evolutionary consequences will follow. There are of course major differences as well between the nature of the evolutionary process in ecological and economic contexts, largely influenced by the relative importance of top-down control, and the degree to which predictive models and long-term planning can be invoked. These are, however, differences of degree.
There are profound similarities between financial systems and the biosphere. Both are complex adaptive systems in which individual agents act to enhance their own interests and objectives, leading to self-organization and emergent features. In viewing global financial markets as comprising a complex-adaptive biological system, researchers in this area intend to develop more effective models to understand these systems. This is not only of theoretical interest, but also has the practical aim to promote economic growth while maintaining financial stability, with the ultimate goal of allocating resources more efficiently through better financial methods.
Evolution is about short-term, relative optimality with respect to other participants in the system. In the biosphere, natural selection acts to improve reproductive success relative to the benchmark of other genomes, within and across species. Evolutionary change can thus be thought of in terms of differential fitness: that is, small differences in reproductive rates between individuals over time leading to large differences in populations. Even the very mechanisms of evolution—including those that generate new variation—are subject to constant modification. In the financial world, the evolutionary forces of mutation, recombination, reproduction, and selection often work on financial institutions and market participants through direct competition, finance “red in tooth and claw.” Financial concepts and strategies thus reproduce themselves through cultural transmission and adoption based on their success in the marketplace. These strategies undergo variation through financial innovation, analogous to mutation or genetic recombination in a biological system, but take place at the level of information and abstract thought in financial contexts. It is “survival of the richest.”
The evolutionary lens provides a natural way to introduce biological concepts into financial and economic analysis. As the evolutionary biologist Theodosius Dobzhansky said, “Nothing in biology makes sense except in the light of evolution” (5). The same may hold for the financial world. Phenomena that have been difficult to analyze within a traditional economic framework, such as growth, size, scale, self-organization, the lifecycle of products and industries, bull/bear market cycles, and the rate of variation or innovation within a system, are all subject to evolutionary forces, whether they take place in the Petri dish or on the trading floor. Biological experiments thus may be able to directly inform economic insights, and market behavior may be able to shed light on evolutionary mysteries in the biological world.
Wednesday, July 14, 2021
“The technological progress we make in the next 100 years will be far larger than all we’ve made since we first controlled fire and invented the wheel...This revolution will generate enough wealth for everyone to have what they need, if we as a society manage it responsibly.”...Altman's argument is this: Since the 1970s, computers have gotten exponentially better even as they’re gotten cheaper, a phenomenon known as Moore’s Law. Altman believes that A.I. could get us closer to Moore’s Law for everything: it could make everything better even as it makes it cheaper. Housing, health care, education, you name it.
A.I. will create phenomenal wealth, but it will do so by driving the price of a lot of labor to basically zero. That is how everything gets cheaper. It’s also how a lot of people lose their jobs...To make that world a good world for people, to make that a utopia rather than a dystopia, it requires really radical policy change to make sure the wealth A.I. creates is distributed broadly. But if we can do that, he says, well, then we can improve the standard of living for people more than we ever have before in less time. So Altman’s got some proposals here for how we can do that. They’re largely proposals to tax wealth and land. And I push on them here.
This is a conversation, then, about the political economy of the next technological age. Some of it is speculative, of course, but some of it isn’t. That shift of power and wealth is already underway. Altman is proposing an answer: a move toward taxing land and wealth, and distributing it to all. We talk about that idea, but also the political economy behind it: Are the people gaining all this power and wealth really going to offer themselves up for more taxation? Or will they fight it tooth-and-nail?
We also discuss who is funding the A.I. revolution, the business models these systems will use (and the dangers of those business models), how A.I. would change the geopolitical balance of power, whether we should allow trillionaires, why the political debate over A.I. is stuck, why a pro-technology progressivism would also need to be committed to a radical politics of equality, what global governance of A.I. could look like, whether I’m just “energy flowing through a neural network,” and much more.
(You can also listen to the whole conversation by following “The Ezra Klein Show” on Apple, Spotify, Google or wherever you get your podcasts.)
Tuesday, July 13, 2021
We all exist as an ongoing simulation of past, present, and future in our brains, with the hallucination we take to be reality being perturbed only when our brains’ expectations are not met. Dotson and Yartsev do experiments in flying bats (of a sort not permitted in humans) that record from the hippocampus showing patterns of neuron activity of the sort needed to support this process. They find that this activity not only encodes the bat’s present location but also signals its positions in the past and future. The technology involved in doing the brain implants that record and wirelessly transmit the neuronal activity, as well as the sophisticated data analysis, is truly awesome (One has to download a massive technical supplement, much too large to include in the article, to get the details.) Here I pass on only the editor’s summary and the abstract for the article:
Representing space in past and future
As an organism moves through space, its brain has to remember its most recent location and anticipate its future position, not just its current place in the world. Earlier studies reported so-called retrospective and prospective place coding in rats while they were running along linear tracks. However, it would be advantageous to study an animal that rapidly moves through three-dimensional space with high precision. Dotson and Yartsev recorded from flying bats to investigate whether place cell activity in hippocampus area CA1 represents local (current) or nonlocal positions. They discovered that the hippocampus not only encodes the bat's present location but also signals its positions in the past and future.Abstract
Navigation occurs through a continuum of space and time. The hippocampus is known to encode the immediate position of moving animals. However, active navigation, especially at high speeds, may require representing navigational information beyond the present moment. Using wireless electrophysiological recordings in freely flying bats, we demonstrate that neural activity in area CA1 predominantly encodes nonlocal spatial information up to meters away from the bat’s present position. This spatiotemporal representation extends both forward and backward in time, with an emphasis on future locations, and is found during both random exploration and goal-directed navigation. The representation of position thus extends along a continuum, with each moment containing information about past, present, and future, and may provide a key mechanism for navigating along self-selected and remembered paths.
Monday, July 12, 2021
Take a big step back. Observe what has happened in our discourse since around 2015...What is it? It is, I’d argue, the sudden, rapid, stunning shift in the belief system of the American elites. It has sent the whole society into a profound cultural dislocation. It is, in essence, an ongoing moral panic against the specter of “white supremacy,” which is now bizarrely regarded as an accurate description of the largest, freest, most successful multiracial democracy in human history...The elites, increasingly sequestered within one political party and one media monoculture, educated by colleges and private schools that have become hermetically sealed against any non-left dissent, have had a “social justice reckoning” these past few years.
..the core point of that movement, its essential point, is that liberalism is no longer enough. Not just not enough, but itself a means to perpetuate “white supremacy,” designed to oppress, harm and terrorize minorities and women, and in dire need of dismantling. That’s a huge deal. And it explains a lot.
The reason “critical race theory” is a decent approximation for this new orthodoxy is that it was precisely this exasperation with liberalism’s seeming inability to end racial inequality in a generation that prompted Derrick Bell et al. to come up with the term in the first place, and Kimberlé Crenshaw to subsequently universalize it beyond race to every other possible dimension of human identity (“intersectionality”)...A specter of invisible and unfalsifiable “systems” and “structures” and “internal biases” arrived to hover over the world. Some of this critique was specific and helpful: the legacy of redlining, the depth of the wealth gap. But much was tendentious post-modern theorizing.
The movement is much broader than race — as anyone who is dealing with matters of sex and gender will tell you. The best moniker I’ve read to describe this mishmash of postmodern thought and therapy culture ascendant among liberal white elites is Wesley Yang’s coinage: “the successor ideology.”...to describe a hegemony that is saturated with “anti-Blackness,” misogyny, and transphobia, in a miasma of social “cis-heteronormative patriarchal white supremacy.” And the term “successor ideology” works because it centers the fact that this ideology wishes, first and foremost, to repeal and succeed a liberal society and democracy...Liberalism leaves you alone. The successor ideology will never let go of you. Liberalism is only concerned with your actions. The successor ideology is concerned with your mind, your psyche, and the deepest recesses of your soul. Liberalism will let you do your job, and let you keep your politics private. S.I. will force you into a struggle session as a condition for employment.
A plank of successor ideology, for example, is that the only and exclusive reason for racial inequality is “white supremacy.” Culture, economics, poverty, criminality, family structure: all are irrelevant, unless seen as mere emanations of white control. Even discussing these complicated factors is racist...The proponents of the successor ideology are] not trying to be malicious, but they are trying to basically annihilate a lot of the foundational processes that we depend upon and then remake them anew. You operate from the starting point that all the previous ideologies, methods, and processes are untrustworthy, because they produced this outcome previously, so we’ve got to remake all of them. Precisely. This is a revolution against liberalism commanded from above.
Due process? If you’re a male on campus, gone. Privacy? Stripped away — by anonymous rape accusations, exposure of private emails, violence against people’s private homes, screaming at folks in restaurants, sordid exposés of sexual encounters, eagerly published by woke mags. Non-violence? Exceptions are available if you want to “punch a fascist.” Free speech? Only if you don’t mind being fired and ostracized as a righteous consequence. Free association? You’ve got to be kidding. Religious freedom? Illegitimate bigotry. Equality? Only group equity counts now, and individuals of the wrong identity can and must be discriminated against. Color-blindness? Another word for racism. Mercy? Not for oppressors. Intent? Irrelevant. Objectivity? A racist lie. Science? A manifestation of white supremacy. Biological sex? Replaced by socially constructed gender so that women have penises and men have periods. The rule of law? Not for migrants or looters. Borders? Racist. Viewpoint diversity? A form of violence against the oppressed.
...check out Kevin Drum’s analysis of asymmetric polarization these past few decades. He shows relentlessly that over the past few decades, it’s Democrats who have veered most decisively to the extremes on policy on cultural issues since the 1990s. Not Republicans. Democrats.On immigration, Republicans have moved around five points to the right; the Democrats 35 points to the left. On abortion, Republicans who advocate a total ban have increased their numbers a couple of points since 1994; Democrats who favor legality in every instance has risen 20 points. On guns, the GOP has moved ten points right; Dems 20 points left.
It is also no accident that, as Drum notes and as David Shor has shown: “white academic theories of racism — and probably the whole woke movement in general —have turned off many moderate Black and Hispanic voters.” This is why even a huge economic boom may not be enough to keep the Democrats in power next year.
Does that mean we should support an increasingly nihilist cult on the right among the GOP? Of course not. Does it mean we should ignore its increasingly menacing contempt for electoral integrity and a stable democracy? Absolutely not. But one reason to fight for liberalism against the successor ideology is that its extremes are quite obviously fomenting and facilitating and inspiring ever-rising fanaticism in response. I fear the successor ideology’s Kulturkampf is already making the 2022 midterms a landslide for a cultish, unmoored GOP. In fighting S.I., we are also fighting Trump.
But I am not making a tactical argument here. I’m making a deeper moral argument. We can and must still fight and argue for what we believe in: a liberal democracy in a liberal society. This fight will not end if we just ignore it or allow ourselves to be intimidated by it, or join the tribal pile-ons. And I will not apologize for confronting this, however unpopular it might make me, just as I won’t apologize for confronting the poison and nihilism on the right. And if you really want to be on “the right side of liberalism,” you will join me.
Friday, July 09, 2021
...in numerous studies conducted throughout the world, consuming four or five eight-ounce cups of coffee (or about 400 milligrams of caffeine) a day has been associated with reduced death rates.But,
..coffee doesn't warrant a totally clean bill of health...The most common ill effect associated with caffeinated coffee is sleep disturbance...People vary widely in how rapidly they metabolize caffeine, enabling some to sleep soundly after drinking caffeinated coffee at dinner while others have trouble sleeping if they have coffee at lunch. But even if you can fall asleep readily after an evening coffee, it may disrupt your ability to get adequate deep sleep, Mr. Pollan states in his forthcoming book, “This Is Your Mind on Plants.”
Caffeine is one of more than a thousand chemicals in coffee, not all of which are beneficial. Among others with positive effects are polyphenols and antioxidants. Polyphenols can inhibit the growth of cancer cells and lower the risk of Type 2 diabetes; antioxidants, which have anti-inflammatory effects, can counter both heart disease and cancer, the nation’s leading killers.
Wednesday, July 07, 2021
The vast majority of people who report a lack of a mind’s eye have no memory of ever having had one, suggesting that they had been born without it. Yet...they had little trouble recalling things they had seen. When asked whether grass or pine tree needles are a darker shade of green, for example, they correctly answered that the needles are.
Researchers are .. starting to use brain scans to find the circuitry that gives rise to aphantasia and hyperphantasia. So far, that work suggests that mental imagery emerges from a network of brain regions that talk to each other...Decision-making regions at the front of the brain send signals to regions at the back, which normally make sense of information from the eyes. Those top-down signals can cause the visual regions to produce images that aren’t there.
In a study published in May, Dr. Zeman and his colleagues scanned the brains of 24 people with aphantasia, 25 people with hyperphantasia and 20 people with neither condition...The people with hyperphantasia had stronger activity in regions linking the front and back of the brain. They may be able to send more potent signals from decision-making regions of the front of the brain to the visual centers at the back.
Monday, July 05, 2021
...our cerebral cortex is only a few millimeters thick (the relative neglect of the rest of the brain below the cortex has prompted the term “corticocentric myopia”). Other regions relevant to behavior include the deep gray matter of the basal ganglia and thalamus, the brainstem and cerebellum, and the white matter that interconnects all of these structures. The white matter is composed of axonal tracts connecting different brain regions, and plays key roles in both normal brain function and a variety of neurological disorders. Zhao et al. have combined detailed magnetic resonance imaging–based assessment of brain structures with genetic data on nearly 44,000 individuals... On the basis of this comprehensive analysis, the authors have identified structural and genetic abnormalities associated with neurological and psychiatric disorders, as well as some nondisease traits, and have created a valuable resource providing some insights into the underlying neurobiology.Here is the Zhao et al. abstract, followed by a graphic from Filley's review.
Brain regions communicate with each other through tracts of myelinated axons, commonly referred to as white matter. We identified common genetic variants influencing white matter microstructure using diffusion magnetic resonance imaging of 43,802 individuals. Genome-wide association analysis identified 109 associated loci, 30 of which were detected by tract-specific functional principal components analysis. A number of loci colocalized with brain diseases, such as glioma and stroke. Genetic correlations were observed between white matter microstructure and 57 complex traits and diseases. Common variants associated with white matter microstructure altered the function of regulatory elements in glial cells, particularly oligodendrocytes. This large-scale tract-specific study advances the understanding of the genetic architecture of white matter and its genetic links to a wide spectrum of clinical outcomes.
Friday, July 02, 2021
A disheartening analysis by Rathje et al.:
Almost four billion people around the world now use social media platforms such as Facebook and Twitter, and social media is one of the primary ways people access news or receive communications from politicians. However, social media may be creating perverse incentives for divisive content because this content is particularly likely to go “viral.” We report evidence that posts about political opponents are substantially more likely to be shared on social media and that this out-group effect is much stronger than other established predictors of social media sharing, such as emotional language. These findings contribute to scholarly debates about the role of social media in political polarization and can inform solutions for creating healthier social media environments.Abstract
There has been growing concern about the role social media plays in political polarization. We investigated whether out-group animosity was particularly successful at generating engagement on two of the largest social media platforms: Facebook and Twitter. Analyzing posts from news media accounts and US congressional members (n = 2,730,215), we found that posts about the political out-group were shared or retweeted about twice as often as posts about the in-group. Each individual term referring to the political out-group increased the odds of a social media post being shared by 67%. Out-group language consistently emerged as the strongest predictor of shares and retweets: the average effect size of out-group language was about 4.8 times as strong as that of negative affect language and about 6.7 times as strong as that of moral-emotional language—both established predictors of social media engagement. Language about the out-group was a very strong predictor of “angry” reactions (the most popular reactions across all datasets), and language about the in-group was a strong predictor of “love” reactions, reflecting in-group favoritism and out-group derogation. This out-group effect was not moderated by political orientation or social media platform, but stronger effects were found among political leaders than among news media accounts. In sum, out-group language is the strongest predictor of social media engagement across all relevant predictors measured, suggesting that social media may be creating perverse incentives for content expressing out-group animosity.
Wednesday, June 30, 2021
ONCE UPON A TIME, you were a little stomach on a stick, floating in the sea. Little by little, you evolved. You grew sensory systems and learned that you were part of a bigger world. You grew bodily systems to navigate that world efficiently. And you grew a brain that ran a budget for your body. You learned to live in groups with all the other little brains-in-bodies. You crawled out of the water and onto land. And across the expanse of evolutionary time - with the innovation that comes from trial and error and the deaths of trillions of animals - you ended up with a human brain. A brain that can do so many impressive things but at the same time severely misunderstands itself.
-A brain that constructs such rich mental experiences that we feel like emotion and reason wrestle inside us
-A brain that’s so complex that we describe it by metaphors and mistake them for knowledge
-A brain that’s so skilled at rewiring itself that we think we’re born with all sorts of things that we actually learn
-A brain that’s so effective at hallucinating that we believe we see the world objectively, and so fast at predicting that we mistake our movements for reactions
-A brain that regulates other brains so invisibly that we presume we’re independent of each other
-A brain that creates so many kinds of minds that we assume there’s a single human nature to explain them all
-A brain that’s so good at believing its own inventions that we mistake social reality for the natural world
We know much about the brain today, but there are still so many more lessons to learn. For now, at least, we’ve learned enough to sketch our brain’s fantastical evolutionary journey and consider the implications for some of the most central and challenging aspects of our lives.
Our kind of brain isn’t the biggest in the animal kingdom, and it’s not the best in any objective sense. But it’s ours. It’s the source of our strengths and our foibles. It gives us our capacity to build civilizations and our capacity to tear down each other. It makes us simply, imperfectly, gloriously human.
Monday, June 28, 2021
Sometimes learning the hard neuroscience of how our brains work leaves me feeling a bit queasy. The first time this happened was when I learned about the Libet experiments that showed that cells in our motor cortex start a movement well before we ‘decide’ to initiate it. “We” think we are initiating a movement when in fact “it” (those brain cells) are already well on their way to doing it. So what happened to my ‘free will’? Well...there is a work around for that problem that I explain in my “I Illusion” and subsequent web lectures.
A further uncomfortable jolt comes on seeing evidence the brain cells that become active during a familiar experience can change over time. Each instance of the recall of an important event can recruit a different group of nerve cells, because each time the memory is fetched from the neuronal ‘library’ it gets put back, sometimes slightly altered, in different nerve cell collections and connections. A very striking example of this has been provided by Schoonover et al. Who show that the network of nerve cells active when a particular smell triggers a specific behavior changes over time, moving to different brain areas. This is an example of ‘representational plasticity’ which is discussed in a review article by Rule et al.
This conflicts with our common sense view of how our minds should work. If you have an experience and then later remember it, you must have put it somewhere in your brain’s library of nerve cell connections, like a book on a library shelf, so that all you have to do to remember something is go fetch it. If the experience is an emotional one it couples with a hard wired circuit for that emotion. This essentialist view of how our minds work is being thoroughly displaced as experimental evidence continues to accumulate showing that in each moment we are constructing our experience anew - reminding of the Buddhist saying that the river you view flowing past is never the same twice. The series of MindBlog posts (starting here) on the work and ideas of Barrett covers this material.
It is from constant change and flux in our evolved neuroendocrine circuitry that we generate the illusion of certainty or constancy - expectations of selves, rules, objects, and emotions that stay in place. We model the world we expect to see before each moment we are about to enter. If our expectations are not met, then our brains perk up to adjust them appropriately.
Friday, June 25, 2021
From Zacharopoulos et al.:
Our knowledge of the effect of a specific lack of education on the brain and cognitive development is currently poor but is highly relevant given differences between countries in their educational curricula and the differences in opportunities to access education. We show that within the same society, adolescent students who specifically lack mathematical education exhibited reduced brain inhibition levels in a key brain area involved in reasoning and cognitive learning. Importantly, these brain inhibition levels predicted mathematical attainment ∼19 mo later, suggesting they play a role in neuroplasticity. Our study provides biological understanding of the impact of the lack of mathematical education on the developing brain and the mutual play between biology and education.Abstract
Formal education has a long-term impact on an individual’s life. However, our knowledge of the effect of a specific lack of education, such as in mathematics, is currently poor but is highly relevant given the extant differences between countries in their educational curricula and the differences in opportunities to access education. Here we examined whether neurotransmitter concentrations in the adolescent brain could classify whether a student is lacking mathematical education. Decreased γ-aminobutyric acid (GABA) concentration within the middle frontal gyrus (MFG) successfully classified whether an adolescent studies math and was negatively associated with frontoparietal connectivity. In a second experiment, we uncovered that our findings were not due to preexisting differences before a mathematical education ceased. Furthermore, we showed that MFG GABA not only classifies whether an adolescent is studying math or not, but it also predicts the changes in mathematical reasoning ∼19 mo later. The present results extend previous work in animals that has emphasized the role of GABA neurotransmission in synaptic and network plasticity and highlight the effect of a specific lack of education on MFG GABA concentration and learning-dependent plasticity. Our findings reveal the reciprocal effect between brain development and education and demonstrate the negative consequences of a specific lack of education during adolescence on brain plasticity and cognitive functions.
Wednesday, June 23, 2021
...a new cognitive construct—decision acuity—that captures global decision-making ability. High decision acuity prominently reflected low decision variability. Decision acuity showed acceptable reliability, increased with age, and was associated with mental health symptoms independently of intelligence. Crucially, it was associated with distinctive resting-state networks, in particular in brain regions typically engaged by decision-making tasks. The association between decision acuity and functional connectivity was temporally stable and distinct from that of IQ.Highlights
• Young people have a general decision-making ability, which we call “decision acuity”
• Decision acuity is reflected in how strongly connected certain brain networks are
• Low decision acuity is associated with general social function psychopathologySummary
Decision-making is a cognitive process of central importance for the quality of our lives. Here, we ask whether a common factor underpins our diverse decision-making abilities. We obtained 32 decision-making measures from 830 young people and identified a common factor that we call “decision acuity,” which was distinct from IQ and reflected a generic decision-making ability. Decision acuity was decreased in those with aberrant thinking and low general social functioning. Crucially, decision acuity and IQ had dissociable brain signatures, in terms of their associated neural networks of resting-state functional connectivity. Decision acuity was reliably measured, and its relationship with functional connectivity was also stable when measured in the same individuals 18 months later. Thus, our behavioral and brain data identify a new cognitive construct that underpins decision-making ability across multiple domains. This construct may be important for understanding mental health, particularly regarding poor social function and aberrant thought patterns.