Why is a moving hand less sensitive to touch than a stationary hand?

Fuehrer et al. do a nice piece showing how our brains' predictive processing can alter our sensory experience:  

Significance

Tactile sensations on a moving hand are perceived weaker than when presented on the same but stationary hand. There is an ongoing debate about whether this weaker perception is based on sensorimotor predictions or is due to a blanket reduction in sensitivity. Here, we show greater suppression of sensations matching predicted sensory feedback. This reinforces the idea of precise estimations of future body sensory states suppressing the predicted sensory feedback. Our results shine light on the mechanisms of human sensorimotor control and are relevant for understanding clinical phenomena related to predictive processes.

Abstract

The ability to sample sensory information with our hands is crucial for smooth and efficient interactions with the world. Despite this important role of touch, tactile sensations on a moving hand are perceived weaker than when presented on the same but stationary hand. This phenomenon of tactile suppression has been explained by predictive mechanisms, such as internal forward models, that estimate future sensory states of the body on the basis of the motor command and suppress the associated predicted sensory feedback. The origins of tactile suppression have sparked a lot of debate, with contemporary accounts claiming that suppression is independent of sensorimotor predictions and is instead due to an unspecific mechanism. Here, we target this debate and provide evidence for specific tactile suppression due to precise sensorimotor predictions. Participants stroked with their finger over textured objects that caused predictable vibrotactile feedback signals on that finger. Shortly before touching the texture, we probed tactile suppression by applying external vibrotactile probes on the moving finger that either matched or mismatched the frequency generated by the stroking movement along the texture. We found stronger suppression of the probes that matched the predicted sensory feedback. These results show that tactile suppression is specifically tuned to the predicted sensory states of a movement.

Mozart and Brahms Piano Trios at an 80th birthday house concert

This post falls in the 'random curious stuff' category mentioned under MindBlog's title. On May 15, one day before my 80th birthday, my piano trio invited friends and family to a Sunday afternoon house concert at the home of our cellist on Cat Mountain in the Northwest Hills of Austin Texas. I have posted the individual movements of the Mozart Piano Trio No. 2 in B flat major, K. 502 and the Brahms Piano Trio No. 1 in B major, Op. 8 on my YouTube channel, as well as in playlists that play through all the movements of each piece. 

To give you a sample, this post passes on the last movements of the two trios. 

The allegretto of the Mozart Trio.

 

The allegro of the Brahms trio. 

Harmonics of the social brain

Interesting work from Mague et al. on the brain-wide network in mice that encodes rewarding social experience: 

Highlights

• Machine learning model discovers and integrates circuits into affective brain network 

• Brain-wide network encodes rewarding social experience of individual mice 

• Causal activation of network sub-circuits selectively induces social behavior 

• Social brain network fails to encode individual behavior in a mouse model of autism

Summary

The architecture whereby activity across many brain regions integrates to encode individual appetitive social behavior remains unknown. Here we measure electrical activity from eight brain regions as mice engage in a social preference assay. We then use machine learning to discover a network that encodes the extent to which individual mice engage another mouse. This network is organized by theta oscillations leading from prelimbic cortex and amygdala that converge on the ventral tegmental area. Network activity is synchronized with cellular firing, and frequency-specific activation of a circuit within this network increases social behavior. Finally, the network generalizes, on a mouse-by-mouse basis, to encode individual differences in social behavior in healthy animals but fails to encode individual behavior in a ‘high confidence’ genetic model of autism. Thus, our findings reveal the architecture whereby the brain integrates distributed activity across timescales to encode an appetitive brain state underlying individual differences in social behavior.

How stress might help reduce dementia and alzheimer’s.

The post today (my 80th birthday) points to experimental results relevant to my interest in not losing my marbles anytime soon. Fauzia points to work by Avezov and collaborators (open source) showing that the accumulation of aggregates of misfolded proteins in the endoplasmic reticulum of brain cells that is associated with dementia and Alzheimer's can be reversed by stressing cells with chemicals or heat, activating molecular chaperones that in turn untangle or remove protein aggregates. How much stress is just enough, but not to much, isn't clear. The abstract of the work:

Protein synthesis is supported by cellular machineries that ensure polypeptides fold to their native conformation, whilst eliminating misfolded, aggregation prone species. Protein aggregation underlies pathologies including neurodegeneration. Aggregates’ formation is antagonised by molecular chaperones, with cytoplasmic machinery resolving insoluble protein aggregates. However, it is unknown whether an analogous disaggregation system exists in the Endoplasmic Reticulum (ER) where ~30% of the proteome is synthesised. Here we show that the ER of a variety of mammalian cell types, including neurons, is endowed with the capability to resolve protein aggregates under stress. Utilising a purpose-developed protein aggregation probing system with a sub-organellar resolution, we observe steady-state aggregate accumulation in the ER. Pharmacological induction of ER stress does not augment aggregates, but rather stimulate their clearance within hours. We show that this dissagregation activity is catalysed by the stress-responsive ER molecular chaperone – BiP. This work reveals a hitherto unknow, non-redundant strand of the proteostasis-restorative ER stress response.

The tabula sapiens consortium - mapping cell types in the human body

It is hard to keep up with the mind boggling advances that pop up in almost every issue of Science Magazine. In a perspective article Liu and Zhang describe the findings of the “Tabula Sapiens Consortium” that has now provided a molecular reference atlas for more than 400 cell types of the human body by measuring the messenger RNA molecules in each of nearly 500,000 cells from 24 tissues and organs. Multiple laboratories used single-cell transcriptomics to measure the messenger RNA molecules in each of nearly 500,000 cells from 24 tissues and organs Here is a single clip summary clip from Liu and Zhang:

...the Tabula Sapiens Consortium discovered that endothelial cells from lung, heart, uterus, liver, pancreas, fat, and muscle exhibit the most distinct transcriptional signatures, suggesting highly specialized functions, whereas endothelial cells from the thymus, vasculature, prostate, and eye resemble one another. The pan-tissue approach led to the discovery of SLC14A1 (solute carrier family 14 member 1) as a marker for heart endothelial cells, likely reflecting specialized metabolism in cardiac blood vessels. Eraslan et al. also found rare cell types, such as neuroendocrine cells in the prostate and enteric neurons in the esophagus. Additionally, the corroborative use of both high-throughput 10X and full-length SMART-seq2 single-cell transcriptome data allowed the quantification of splicing isoform usage at the single-cell level, thereby revealing differential exon usage patterns for genes, including MYL6 (myosin light chain 6) and CD47, in different cell-type compartments.

Increases and decreases in affective polarization over the past 40 years in advanced democracies

An interesting study from Boxell et al. shows that across 12 advanced democracies, affective polarization, the degree to which people feel more negatively toward other political parties than toward their own, has increased the most since the 1980s in the United States and to a lesser extent in Canada, Denmark, France, New Zealand, and Switzerland, and has decreased in Australia, Britain, (West) Germany, Japan, Norway, and Sweden. The authors derived theses conclusions from harmonizing results from 149 surveys and assembled data on economic, media, demographic, and political trends. Trends in the nonwhite share of the population and in the polarization of political elites were most strongly associated with trends in polarization of the general public.

Graziano's conceptual framework for consciousness

I would like to pass on this link to Graziano's latest (open source) explication of his theory of consciousness, continuing a MindBlog thread that started with a 2014 post on his 2013 book "Consciousness and the Social Brain." Here is his abstact:

This article argues that consciousness has a logically sound, explanatory framework, different from typical accounts that suffer from hidden mysticism. The article has three main parts. The first describes background principles concerning information processing in the brain, from which one can deduce a general, rational framework for explaining consciousness. The second part describes a specific theory that embodies those background principles, the Attention Schema Theory. In the past several years, a growing body of experimental evidence—behavioral evidence, brain imaging evidence, and computational modeling—has addressed aspects of the theory. The final part discusses the evolution of consciousness. By emphasizing the specific role of consciousness in cognition and behavior, the present approach leads to a proposed account of how consciousness may have evolved over millions of years, from fish to humans. The goal of this article is to present a comprehensive, overarching framework in which we can understand scientifically what consciousness is and what key adaptive roles it plays in brain function.

The article is worth a read, and here is Graziano's bottom line, from the last paragraph of his article:

If you start your search for consciousness by assuming the existence of a subjective feeling—a private component that cannot be measured and can only be felt and attested to, experienceness itself—then you are assuming the literal accuracy of an internal model. By principle 1, your conviction that you have consciousness depends on an information set in your brain. By principle 2, the brain’s models are never accurate. You have accepted the literal truth of a caricature, and you will never find the answer to your ill-posed question. When the police draw a sketch of a suspect, and you set yourself the task of finding a flat man made of graphite, you will fail. Yet at the same time, if you take the opposite approach and insist that the sketch is an empty illusion, you are missing the point. Instead, understand the sketch for what it is: a schematic representation of something real. We can explain physical processes in the brain; we can explain the models constructed by the brain to represent those physical processes; we can explain the way those models depict reality in a schematic, imperfect manner; we can explain the cognitive beliefs that stem from those imperfect models; and most importantly, we can explain the adaptive, cognitive benefits served by those models. AST is not just a theory of consciousness. It is a theory of adaptive mechanisms in the brain.

The prosocial effect of touching - the Midas touch effect.

Schaefer et al. (open source) examine the neural underpinnings of how light touching enhances prosocial behavior. Their abstract:

Giving and receiving touch are some of the most important social stimuli we exchange in daily life. By touching someone, we can communicate various types of information. Previous studies have also demonstrated that interpersonal touch may affect our altruistic behavior. A classic study showed that customers give bigger tips when they are lightly touched by a waitress, which has been called the Midas touch effect. Numerous studies reported similar effects of touch on different kinds of helping or prosocial behaviors. Here, we aim to examine the neural underpinnings of this effect by employing a functional magnetic resonance imaging approach. While lying in the scanner, participants played different rounds of the dictator game, a measure of prosocial behavior. Before each round, participants were touched (or not touched in the control condition) by an experimenter. We found that touching the hand increased the likeliness to behave prosocial (but not the general liking of control stimuli), thereby confirming the Midas touch effect. The effect was predicted by activity in the primary somatosensory cortex, indicating that the somatosensory cortex here plays a causal role in prosocial behavior. We conclude that the tactile modality in social life may be much more important than previously thought.

Questioning common claims about human brain evolution

From DeCasien et al.:

Highlights

New research has questioned or contradicted multiple long-standing claims about human brain evolution.

Contrary to the social brain hypothesis, new work suggests that ecological factors, rather than social complexity, best predict relative brain size across primate species.

Brain size does not have similar effects or cognitive implications in different phylogenetic lineages since it is associated with different mosaic structural changes.

Although the human prefrontal cortex is proportionally large, this may not represent an adaptive specialization and research emphasis on this region has distracted attention from the importance of wider neural networks.

Functional and anatomical integration, rather than developmental constraints, may primarily explain patterns of brain region size covariation across species.

Abstract

Human brains are exceptionally large, support distinctive cognitive processes, and evolved by natural selection to mediate adaptive behavior. Comparative biology situates the human brain within an evolutionary context to illuminate how it has been shaped by selection and how its structure relates to evolutionary function, while identifying the developmental and molecular changes that were involved. Recent applications of powerful phylogenetic methods have uncovered new findings, some of which overturn conventional wisdom about how and why brains evolve. Here, we focus on four long-standing claims about brain evolution and discuss how new work has either contradicted these claims or shown the relevant phenomena to be more complicated than previously appreciated. Throughout, we emphasize studies of non-human primates and hominins, our close relatives and recent ancestors.

The authors dispute the following common claims about human brain evolution: (Motivated readers can obtain the whole text with their detailed arguments from me.)

Claim 1. Social complexity is the primary driver of non-human primate and human brain evolution

Claim 2. Brain size has similar effects and cognitive implications across a wide range of species

Claim 3. The proportionally large human PFC reflects selection on PFC-specific functions

Claim 4. Developmental constraints play a major role in the evolution of brain structure

Older adults store too much information.

From Amer et al.:  

Highlights

Healthy aging is accompanied by declines in control of attention.

These reductions in the control of attention, result in older adults processing too much information, creating cluttered memory representations.

Cluttered representations can impair memory by interfering with the retrieval of target information, but can also provide an advantage on tasks that benefit from extensive knowledge.

Abstract

Declines in episodic memory in older adults are typically attributed to differences in encoding strategies and/or retrieval processes. These views omit a critical factor in age-related memory differences: the nature of the representations that are formed. Here, we review evidence that older adults create more cluttered (or richer) representations of events than do younger adults. These cluttered representations might include target information along with recently activated but no-longer-relevant information, prior knowledge cued by the ongoing situation, as well as irrelevant information in the current environment. Although these representations can interfere with the retrieval of target information, they can also support other memory-dependent cognitive functions.

The human fear paradox: Affective origins of cooperative care

On the same morning last week that I read a NYTimes essay by Thomas Edsall "The Politics of Fear Show No Sign of Abating" I received an email from the journal Behavioral and Brain Science soliciting reviews on an upcoming article by Tobias Grossmann with an interesting hypothesis on why we humans are so fearful: "The human fear paradox: Affective origins of cooperative care." His 'fearful ape hypothesis' proposes that, in the context of the strong interdependence reflected in cooperative caregiving and provisioning unique to human great ape group life, heightened fearfulness was adaptive. Here I pass on the abstract of Grossmann's piece, and motivated readers can obtain the whole text from me.

Already as infants humans are more fearful than our closest living primate relatives, the chimpanzees. Yet heightened fearfulness is mostly considered maladaptive, as it is thought to increase the risk of developing anxiety and depression. How can this human fear paradox be explained? The fearful ape hypothesis presented herein stipulates that, in the context of cooperative caregiving and provisioning unique to human great ape group life, heightened fearfulness was adaptive. This is because from early in ontogeny fearfulness expressed and perceived enhanced care-based responding and provisioning from, while concurrently increasing cooperation with, mothers and others. This explanation is based on a synthesis of existing research with human infants and children, demonstrating a link between fearfulness, greater sensitivity to and accuracy in detecting fear in others, and enhanced levels of cooperative behaviors. These insights critically advance current evolutionary theories of human cooperation by adding an early-developing affective component to the human cooperative makeup. Moreover, the current proposal has important cultural, societal and health implications, as it challenges the predominant view in WEIRD societies that commonly construe fearfulness as a maladaptive trait, potentially ignoring its evolutionary adaptive functions.

The cultural evolution of love in literary history

An interesting article from Baumard et al. in Nature Human Behaviour:

Since the late nineteenth century, cultural historians have noted that the importance of love increased during the Medieval and Early Modern European period (a phenomenon that was once referred to as the emergence of ‘courtly love’). However, more recent works have shown a similar increase in Chinese, Arabic, Persian, Indian and Japanese cultures. Why such a convergent evolution in very different cultures? Using qualitative and quantitative approaches, we leverage literary history and build a database of ancient literary fiction for 19 geographical areas and 77 historical periods covering 3,800 years, from the Middle Bronze Age to the Early Modern period. We first confirm that romantic elements have increased in Eurasian literary fiction over the past millennium, and that similar increases also occurred earlier, in Ancient Greece, Rome and Classical India. We then explore the ecological determinants of this increase. Consistent with hypotheses from cultural history and behavioural ecology, we show that a higher level of economic development is strongly associated with a greater incidence of love in narrative fiction (our proxy for the importance of love in a culture). To further test the causal role of economic development, we used a difference-in-difference method that exploits exogenous regional variations in economic development resulting from the adoption of the heavy plough in medieval Europe. Finally, we used probabilistic generative models to reconstruct the latent evolution of love and to assess the respective role of cultural diffusion and economic development.

Are we seeing the beginning of World War III?

Below, I am passing on some links to background reading for this Sunday's Austin Rainbow Forum (email forumaustin@gmail.com for information), whose discussion topic is "The War in Ukraine: Start of World War III?." 

David Brooks - Globalization Is Over. The Global Culture Wars Have Begun

Thomas Friedman - Putin Had No Clue How Many of Us Would Be Watching 

Yuval Harari - What’s at stake in Ukraine is the direction of human history 

Fareed Zakaria - Russia is the last multinational empire, fighting to keep its colonies  

Ezra Klein - The Enemies of Liberalism Are Showing Us What It Really Means  

 

Insight from Jonathan Haidt - "After Babel"

This article by Jonathan Haidt in the May 2022 print edition of The Atlantic is a long, frightening, and rewarding read. It lays out the mechanisms by which social media have catalyzed civil society's world wide disintegration over the past 10 years. I will not presume to do my usual extracting of summary chunks apart from passing on the first few paragraphs to whet your appetite:

The story of Babel is the best metaphor I have found for what happened to America in the 2010s, and for the fractured country we now inhabit. Something went terribly wrong, very suddenly. We are disoriented, unable to speak the same language or recognize the same truth. We are cut off from one another and from the past.

It’s been clear for quite a while now that red America and blue America are becoming like two different countries claiming the same territory, with two different versions of the Constitution, economics, and American history. But Babel is not a story about tribalism; it’s a story about the fragmentation of everything. It’s about the shattering of all that had seemed solid, the scattering of people who had been a community. It’s a metaphor for what is happening not only between red and blue, but within the left and within the right, as well as within universities, companies, professional associations, museums, and even families.

Babel is a metaphor for what some forms of social media have done to nearly all of the groups and institutions most important to the country’s future—and to us as a people. How did this happen? And what does it portend for American life?

How the gut talks to the brain.

Gabanyi et al. show that bacterial cell wall molecules that travel to the brain could trigger a host of behaviors. Here is the abstract of a Perspectives essay on this work by Adamantidis:

The mammalian gastrointestinal tract hosts a community of diverse micro-organisms, including bacteria, archea, fungi, and viruses. Bacterial products, such as metabolites and cell wall fragments, are implicated in host metabolic functions. In addition, the gut microbiota influences the immune and central nervous systems, and it has emerged as a key regulator of brain development and the modulation of behaviors, including stress and anxiety, often in a sex-specific manner. Disruption of gut microbiota–brain interactions contribute to the pathogenesis of neurodevelopmental and psychiatric disorders in animal models. ...Gabanyi et al. show that bacterial peptidoglycans, a by-product of bacterial cell wall degradation during cell division and cell death, directly inhibit the activity of feeding-promoting neurons in the hypothalamus and ultimately decrease appetite and body temperature, mostly in female mice. This finding may open new approaches for the treatment of metabolic disorders, including obesity.

A magisterial summary of the new world disorder by David Brooks

A few clips that attempt to summarize a David Brooks essay that does a beautiful job of putting all the pieces together:

I can remember a time — about a quarter-century ago — when the world seemed to be coming together. The great Cold War contest between communism and capitalism appeared to be over. Democracy was still spreading. Nations were becoming more economically interdependent. The internet seemed ready to foster worldwide communications. It seemed as if there would be a global convergence around a set of universal values — freedom, equality, personal dignity, pluralism, human rights...it was sometimes assumed that nations all around the world would admire the success of the Western democracies and seek to imitate us...They’d be more driven by the desire to settle down into suburban homes than by the fanatical ideologies or the sort of hunger for prestige and conquest that had doomed humanity to centuries of war.

...this vision does not describe the world we live in today. The world is not converging anymore; it’s diverging...The 2008 financial crisis delegitimized global capitalism for many people...Global flows of long-term investment fell by half between 2016 and 2019...All manner of antiglobalization movements have arisen: those of the Brexiteers, xenophobic nationalists, Trumpian populists, the antiglobalist left...The world economy seems to be gradually decoupling into, for starters, a Western zone and a Chinese zone. Foreign direct investment flows between China and America were nearly $30 billion per year five years ago. Now they are down to $5 billion...Economic rivalries have now merged with political, moral and other rivalries into one global contest for dominance. Globalization has been replaced by something that looks a lot like global culture war.

The fact is that human behavior is often driven by forces much deeper than economic and political self-interest, at least as Western rationalists typically understand these things...First, human beings are powerfully driven by what are known as the thymotic desires. These are the needs to be seen, respected, appreciated. If you give people the impression that they are unseen, disrespected and unappreciated, they will become enraged, resentful and vengeful. They will perceive diminishment as injustice and respond with aggressive indignation...Global politics over the past few decades functioned as a massive social inequality machine. In country after country, groups of highly educated urban elites have arisen to dominate media, universities, culture and often political power. Great swaths of people feel looked down upon and ignored.

Second, most people have a strong loyalty to their place and to their nation. But over the past few decades many people have felt that their places have been left behind and that their national honor has been threatened. In the heyday of globalization, multilateral organizations and global corporations seemed to be eclipsing nation-states...In country after country, highly nationalistic movements have arisen to insist on national sovereignty and to restore national pride: Modi in India, Recep Tayyip Erdogan in Turkey, Trump in the United States, Boris Johnson in Britain.

Third, people are driven by moral longings — by their attachment to their own cultural values, by their desire to fiercely defend their values when they seem to be under assault. For the past few decades, globalization has seemed to many people to be exactly this kind of assault...The problem is that Western values are not the world’s values. In fact, we in the West are complete cultural outliers. In his book “The WEIRDest People in the World,” Joseph Henrich amasses hundreds of pages of data to show just how unusual Western, Educated, Industrialized, Rich and Democratic values are...Many people around the world look at our ideas about gender roles and find them foreign or repellent...The idea that it’s up to each person to choose one’s own identity and values — that seems ridiculous to many. The idea that the purpose of education is to inculcate critical thinking skills so students can liberate themselves from the ideas they received from their parents and communities — that seems foolish to many.

Finally, people are powerfully driven by a desire for order. Nothing is worse than chaos and anarchy...Today, many democracies appear less stable than they did and many authoritarian regimes appear more stable. American democracy, for example, has slid toward polarization and dysfunction. Meanwhile, China has shown that highly centralized nations can be just as technologically advanced as the West. Modern authoritarian nations now have technologies that allow them to exercise pervasive control of their citizens in ways that were unimaginable decades ago...Autocratic regimes are now serious economic rivals to the West. They account for 60 percent of patent applications. In 2020, the governments and businesses in these countries invested $9 trillion in things like machinery, equipment and infrastructure, while democratic nations invested $12 trillion. If things are going well, authoritarian governments can enjoy surprising popular support.

...something bigger is happening today that is different from the great power struggles of the past, that is different from the Cold War. This is not just a political or an economic conflict. It’s a conflict about politics, economics, culture, status, psychology, morality and religion all at once. More specifically, it’s a rejection of Western ways of doing things by hundreds of millions of people along a wide array of fronts...To define this conflict most generously, I’d say it’s the difference between the West’s emphasis on personal dignity and much of the rest of the world’s emphasis on communal cohesion. But that’s not all that’s going on here. What’s important is the way these longstanding and normal cultural differences are being whipped up by autocrats who want to expand their power and sow chaos in the democratic world. Authoritarian rulers now routinely weaponize cultural differences, religious tensions and status resentments to mobilize supporters, attract allies and expand their own power. This is cultural difference transmogrified by status resentment into culture war.

...rejection of Western liberalism, individualism, pluralism, gender equality and all the rest is not only happening between nations but also within nations. The status resentment against Western cultural, economic and political elites that flows from the mouths of illiberal leaders like Putin and Modi and Jair Bolsonaro of Brazil sounds quite a lot like the status resentment that flows from the mouths of the Trumpian right, from the French right, from the Italian and Hungarian right...How do you win a global culture war in which differing views on secularism and gay rights parades are intertwined with nuclear weapons, global trade flows, status resentments, toxic masculinity and authoritarian power grabs?

The critiques that so many people are making about the West, and about American culture — for being too individualistic, too materialistic, too condescending — these critiques are not wrong. We have a lot of work to do if we are going to be socially strong enough to stand up to the challenges that are coming over the next several years, if we are going to persuade people in all those swing countries across Africa, Latin America and the rest of the world that they should throw their lot in with the democracies and not with the authoritarians — that our way of life is the better way of life.

At the end of the day, only democracy and liberalism are based on respect for the dignity of each person. At the end of the day, only these systems and our worldviews offer the highest fulfillment for the drives and desires I’ve tried to describe here...I have faith in the ideas and the moral systems that we have inherited. What we call “the West” is not an ethnic designation or an elitist country club. The heroes of Ukraine are showing that at its best, it is a moral accomplishment, and unlike its rivals, it aspires to extend dignity, human rights and self-determination to all. That’s worth reforming and working on and defending and sharing in the decades ahead.

The Dance of Sleep

Sleep and wakefulness are characterized by unique intrinsic activity patterns and are usually thought to be two distinct global states, with the preoptic area of the hypothalamus being the regulator of brain state changes. Yamagata et al. find that this area also affects within-state changes of sleep and wake intensity.  

Significance

Our current understanding of how sleep is regulated is based upon the model of sleep homeostasis, which defines a variable called Process S as a measure of sleep need, and a so-called “flip-flop” model of state switching, which builds on a notion of a mutually antagonistic relationship between subcortical sleep-promoting and wake-promoting circuits. The neurobiological substrates of the interaction between the sleep switch and Process S are unknown. Our study identifies a previously unrecognized role of hypothalamic circuitry in tuning within-state brain activity or levels of arousal, which in turn determine the homeostatic drive for sleep.

Abstract

Sleep and wakefulness are not simple, homogenous all-or-none states but represent a spectrum of substates, distinguished by behavior, levels of arousal, and brain activity at the local and global levels. Until now, the role of the hypothalamic circuitry in sleep–wake control was studied primarily with respect to its contribution to rapid state transitions. In contrast, whether the hypothalamus modulates within-state dynamics (state “quality”) and the functional significance thereof remains unexplored. Here, we show that photoactivation of inhibitory neurons in the lateral preoptic area (LPO) of the hypothalamus of adult male and female laboratory mice does not merely trigger awakening from sleep, but the resulting awake state is also characterized by an activated electroencephalogram (EEG) pattern, suggesting increased levels of arousal. This was associated with a faster build-up of sleep pressure, as reflected in higher EEG slow-wave activity (SWA) during subsequent sleep. In contrast, photoinhibition of inhibitory LPO neurons did not result in changes in vigilance states but was associated with persistently increased EEG SWA during spontaneous sleep. These findings suggest a role of the LPO in regulating arousal levels, which we propose as a key variable shaping the daily architecture of sleep–wake states.

The road to our larger brains

Bertrand et al. address the question of how and why mammals evolved large brain sizes relative to their body mass by characterizing the timing and pattern of mammal brain development across the Early Jurassic to the middle Cenozoic (∼200 million to 30 million years ago) when the ecological niches vacated by the extinction of large reptiles were being filled by large mammals. Here is their abstract:

Mammals are the most encephalized vertebrates, with the largest brains relative to body size. Placental mammals have particularly enlarged brains, with expanded neocortices for sensory integration, the origins of which are unclear. We used computed tomography scans of newly discovered Paleocene fossils to show that contrary to the convention that mammal brains have steadily enlarged over time, early placentals initially decreased their relative brain sizes because body mass increased at a faster rate. Later in the Eocene, multiple crown lineages independently acquired highly encephalized brains through marked growth in sensory regions. We argue that the placental radiation initially emphasized increases in body size as extinction survivors filled vacant niches. Brains eventually became larger as ecosystems saturated and competition intensified.

Humans don’t have culture because we’re smart, we’re smart because we have culture.

The title of this post is a sentence taken from the final paragraph of Henrich's Perspective article in Science on the work of Thompson et al. which notes that Thompson et al.'s results

...highlight a deeper point: Humans don’t have culture because we’re smart, we’re smart because we have culture. The selective processes of cultural evolution not only generate more sophisticated practices and technologies but also produce new cognitive tools—algorithms—that make humans better adapted to the ecological and institutional challenges that we confront. Thompson et al.’s results underline the need for the psychological sciences to abandon their implicit reliance on a digital computer metaphor of the mind (hardware versus software) and transform into a historical science that considers not just how cultural evolution shapes what we think (our mental contents) but also how we think [our cognitive processes].

Here I pass on the introductory paragraphs and then the abstract of the Thompson et al. article. Motivated readers can obtain the full text by emailing me.

Reading, counting, cooking, and sailing are just some of the human abilities passed from generation to generation through social learning... Complex abilities like these often depend on learned cognitive algorithms: procedural representations of a problem that coordinate memory, attention, and perception into sequences of useful computations and actions. Accumulation of complex algorithms—from ancient tool-making techniques to bread making, boat building, or horticulture—is central to human adaptation yet challenging to explain because algorithmic concepts can be difficult to discover, communicate, and learn from observation, making them vulnerable to loss. Theories of cultural evolution suggest that human social learning may help overcome this fragility. For example, mathematical models predict that choosing to learn from successful or prestigious individuals can prevent the loss of rare innovations. However, this potential link between sociality and complex abilities is challenging to establish.

We conducted large-scale simulations of cultural evolution with human participants to assess how selective social learning influenced the evolution of cognitive algorithms. Prior research shows that social learning can improve decisions in multiple-choice tasks, perceptual judgments, and search problems and can improve artifacts such as physical structures or computer programs. However, the evolution of cognitive algorithms at the population level has been difficult to study. We developed custom software to recruit large numbers of participants online and organize them into evolving societies facing a common problem. Twenty populations tackled a sequential decision problem... Presented with six images, participants attempted to establish hidden arbitrary orderings using pairwise comparisons. Out-of-order pairs swapped positions when compared. Participants were rewarded for establishing the ordering using fewer comparisons. This task poses a sorting problem, requiring a strategy for executing appropriate sequences of actions, analogous to culturally evolved strategies for making tools or food.

Abstract:

Many human abilities rely on cognitive algorithms discovered by previous generations. Cultural accumulation of innovative algorithms is hard to explain because complex concepts are difficult to pass on. We found that selective social learning preserved rare discoveries of exceptional algorithms in a large experimental simulation of cultural evolution. Participants (N = 3450) faced a difficult sequential decision problem (sorting an unknown sequence of numbers) and transmitted solutions across 12 generations in 20 populations. Several known sorting algorithms were discovered. Complex algorithms persisted when participants could choose who to learn from but frequently became extinct in populations lacking this selection process, converging on highly transmissible lower-performance algorithms. These results provide experimental evidence for hypothesized links between sociality and cognitive function in humans.

The Science of Consciousness - Tucson 2022

For junkies of consciousness and altered states thereof, as in anesthesia or psychedelic-induced states, a browsing of the abstracts submitted for The Science of Consciousness 2022 in Tucson April 18-22 makes for stimulating reading (though I found pauses to recover from input overload to be necessary.) I attended the first “Towards a Science of Consciousness” - now known as TSC “The Science of Consciousness” - in 1994, as well as a number of subsequent meetings, and it was encouragement from several then luminaries in the field that emboldened me to turn the lecture notes from my “Biology of Mind” course at the University of Wisconsin into a book of that title which was published in 1999. There are numerous bon-bons to be found in this year's set of abstracts, one example from many being Huang’s noting of his work on how the anterior insula, situated between unimodal and transmodal cortical areas along the brain’s primary functional gradient, regulates the default mode – dorsal attention network transitions, and gates conscious access of sensory information.