Why science needs philosophy

I have always been in awe of the clarity and precision of the thinking of one of my Univ. of Wisconsin colleagues, philosopher Elliott Sober. He is one of the coauthors of a fascinating article on the uses science has for the tools of philosophers (for example, to clean up their fuzzy thinking.) The article might be a bit intense for many readers, but I recommend reading through it. Just a few clips:

...philosophy’s contribution can take at least four forms: the clarification of scientific concepts, the critical assessment of scientific assumptions or methods, the formulation of new concepts and theories, and the fostering of dialogue between different sciences, as well as between science and society.

An example of conceptual clarification:

The definition of stem cells is a prime example. Philosophy has a long tradition of investigating properties, and the tools in use in this tradition have recently been applied to describe “stemness,” the property that defines stem cells. One of us has shown that four different kinds of properties exist under the guise of stemness in current scientific knowledge (1). Depending on the type of tissue, stemness can be a categorical property (an intrinsic property of the stem cell, independent of its environment), a dispositional property (an intrinsic property of the stem cell that is controlled by the microenvironment), a relational property (an extrinsic property that can be conferred to non–stem cells by the microenvironment), or a systemic property (a property that is maintained and controlled at the level of the entire cell population).

Spinning drops!

Here is a really neat, gee whiz kind of study:

To make the water droplets spin, researchers first had to make sure they didn’t wet the surface they fell on—otherwise, they’d just splash. The researchers did this by coating alumina plates with a fluorinated nonstick coating, similar to those found in nonstick cooking pans. Next, they masked some regions of the surface and shone ultraviolet (UV) light on the entire plate. The regions exposed to the UV became highly “wettable,” meaning water touching those regions spread out immediately rather than bouncing back up. The team created several designs of the wettable regions, including one with spiral arms radiating out from a center, much like a pinwheel.

As the droplet bounds up from the patterned surface, the portions encountering the wettable spirals stick to the surface, whereas the parts of the droplet in contact with the water-repelling surface rebound immediately. This creates a set of unbalanced forces, pulling on the droplet more in some parts than in others, twisting it.

Psychological underpinnings of politics

I want to point to a number of commentaries on psychological determinants of political behavior that have been languishing in my queue of potential posts...

How brain science could determine the election. A review of differences between liberals and conservatives in brain processes - with a strong genetic component - that regulate risk tolerance, openness to novelty, fearfulness, etc.

Why Trump will win a second term. Amy Chozick discusses Trump's uncanny grasp, deriving from his experience as a reality show host, of how to keep people's attention by creating an unscripted drama that fills living rooms everywhere, providing entertainment value in the chaos.

The end of the two-party system. David Brooks describes the dissolution of political parties into warring clans competing for declining resources.

Our Culture of Contempt.  Arthur Brooks notes that the problem in America today is not incivility or intolerance, it is contempt for those with opposing views. This is based on motive attribution asymmetry, which leads one side to consider itself driven by benevolence while thinking the other side is motivated by evil and hatred.

Is there such a thing as an authoritarian voter?  Molly Worthen review work studying the psychological traits of voters who are attracted to authoritarian personalities. 

Why is it so hard for democracy to deal with inequality? The Brahmins vs the Merchants

I want to pass on an article that I wish I had made the subject of a longer post when it first appeared.

Thomas Edsall, in "Why is it so hard for democracy to deal with inequality" points to a Power Point presentation by Thomas Piketty, "Brahmin Left vs Merchant Right," that notes a straightforward answer:

Traditional parties of the left no longer represent the working and lower middle classes...the domination of the Democratic Party here (and of socialist parties in France) by voters without college or university degrees came to an end over the period from 1948 to 2017. Both parties are now led by highly educated voters whose interests are markedly different from those in the working class...The result, Piketty argues, is a political system that pits two top-down coalitions against each other...high-education elites vote for the left, while high-income/high-wealth elites for the right, i.e., intellectual elite (Brahmin Left) vs business elite (Merchant Right).

Social threat learning transfers to our decision making.

Lindström et al. (open source) demonstrate that threat associations acquired both by social observation (e.g., through video) and by instruction (e.g., through spoken language) strongly transfer to decision making. This transfer leads to maladaptive decisions when socially acquired associations are outdated rather than valid. The full text describes the three different experimental paradigms noted in the abstract below:

Significance

In today’s world, indirect exposure to threatening situations is more common than ever, as illustrated by footage of terror and disaster in social media. How do such social threat learning experiences shape our decisions? We found that learning about threats from both observation and verbal information strongly influenced decision making. As with learning from our own experience, this influence could be either adaptive or maladaptive depending on whether the social information provided accurate expectations about the environment. Our findings can help explain both adaptive and pathological behaviors resulting from the indirect exposure to threatening events.

Abstract

In today’s world, mass-media and online social networks present us with unprecedented exposure to second-hand, vicarious experiences and thereby the chance of forming associations between previously innocuous events (e.g., being in a subway station) and aversive outcomes (e.g., footage or verbal reports from a violent terrorist attack) without direct experience. Such social threat, or fear, learning can have dramatic consequences, as manifested in acute stress symptoms and maladaptive fears. However, most research has so far focused on socially acquired threat responses that are expressed as increased arousal rather than active behavior. In three experiments (n = 120), we examined the effect of indirect experiences on behaviors by establishing a link between social threat learning and instrumental decision making. We contrasted learning from direct experience (i.e., Pavlovian conditioning) (experiment 1) against two common forms of social threat learning—social observation (experiment 2) and verbal instruction (experiment 3)—and how this learning transferred to subsequent instrumental decision making using behavioral experiments and computational modeling. We found that both types of social threat learning transfer to decision making in a strong and surprisingly inflexible manner. Notably, computational modeling indicated that the transfer of observational and instructed threat learning involved different computational mechanisms. Our results demonstrate the strong influence of others’ expressions of fear on one’s own decisions and have important implications for understanding both healthy and pathological human behaviors resulting from the indirect exposure to threatening events.

How sleep aids recovery from infection, may protect brain from Alzheimer's disease

Dimitrov et al. show how a good night's sleep accelerates recovering from an infection. Glue like proteins (integrins) used by immune system T cells to attach to virus particles and mark them for destruction are produced at greater levels during sleep. In the awake state, signaling molecules like adrenaline are produced at greater levels and inhibit integrin production, reducing the ability of T cells to attach to invading microbes. Here is their technical abstract:

Efficient T cell responses require the firm adhesion of T cells to their targets, e.g., virus-infected cells, which depends on T cell receptor (TCR)–mediated activation of β2-integrins. Gαs-coupled receptor agonists are known to have immunosuppressive effects, but their impact on TCR-mediated integrin activation is unknown. Using multimers of peptide major histocompatibility complex molecules (pMHC) and of ICAM-1—the ligand of β2-integrins—we show that the Gαs-coupled receptor agonists isoproterenol, epinephrine, norepinephrine, prostaglandin (PG) E2, PGD2, and adenosine strongly inhibit integrin activation on human CMV- and EBV-specific CD8+ T cells in a dose-dependent manner. In contrast, sleep, a natural condition of low levels of Gαs-coupled receptor agonists, up-regulates integrin activation compared with nocturnal wakefulness, a mechanism possibly underlying some of the immune-supportive effects of sleep. The findings are also relevant for several pathologies associated with increased levels of Gαs-coupled receptor agonists (e.g., tumor growth, malaria, hypoxia, stress, and sleep disturbances).

Also, Holth et al. show that sleep appears to have a direct protective effect on a key protein that drives AD pathology. They provide direct evidence that disrupting sleep, or stimulating excitatory neurons in brain nuclei that control wakefulness and arousal, promotes the release and spread of damaging tau aggregates across the brains of mice, and that sleep deprivation leads to increased extracellular Aβ and tau in people.

The sleep-wake cycle regulates interstitial fluid (ISF) and cerebrospinal fluid (CSF) levels of β-amyloid (Aβ) that accumulates in Alzheimer’s disease (AD). Furthermore, chronic sleep deprivation (SD) increases Aβ plaques. However, tau, not Aβ, accumulation appears to drive AD neurodegeneration. We tested whether ISF/CSF tau and tau seeding and spreading were influenced by the sleep-wake cycle and SD. Mouse ISF tau was increased ~90% during normal wakefulness versus sleep and ~100% during SD. Human CSF tau also increased more than 50% during SD. In a tau seeding-and-spreading model, chronic SD increased tau pathology spreading. Chemogenetically driven wakefulness in mice also significantly increased both ISF Aβ and tau. Thus, the sleep-wake cycle regulates ISF tau, and SD increases ISF and CSF tau as well as tau pathology spreading.

How many push-ups can you do? Predicting heart health...

Gretchen Reynolds points to work showing that men who could get through 40 or more push-ups had 96 percent less risk of heart problems in the next 10 years than those who quit at 10 or fewer.

Abstract

Importance - Cardiovascular disease (CVD) remains the leading cause of mortality worldwide. Robust evidence indicates an association of increased physical fitness with a lower risk of CVD events and improved longevity; however, few have studied simple, low-cost measures of functional status.

Objective - To evaluate the association between push-up capacity and subsequent CVD event incidence in a cohort of active adult men.

Design, Setting, and Participants - Retrospective longitudinal cohort study conducted between January 1, 2000, and December 31, 2010, in 1 outpatient clinics in Indiana of male firefighters aged 18 years or older. Baseline and periodic physical examinations, including tests of push-up capacity and exercise tolerance, were performed between February 2, 2000, and November 12, 2007. Participants were stratified into 5 groups based on number of push-ups completed and were followed up for 10 years. Final statistical analyses were completed on August 11, 2018.

Main Outcomes and Measures - Cardiovascular disease–related outcomes through 2010 included incident diagnoses of coronary artery disease and other major CVD events. Incidence rate ratios (IRRs) were computed, and logistic regression models were used to model the time to each outcome from baseline, adjusting for age and body mass index (BMI) (calculated as weight in kilograms divided by height in meters squared). Kaplan-Meier estimates for cumulative risk were computed for the push-up categories.

Results - A total of 1562 participants underwent baseline examination, and 1104 with available push-up data were included in the final analyses. Mean (SD) age of the cohort at baseline was 39.6 (9.2) years, and mean (SD) BMI was 28.7 (4.3). During the 10-year follow up, 37 CVD-related outcomes (8601 person-years) were reported in participants with available push-up data. Significant negative associations were found between increasing push-up capacity and CVD events. Participants able to complete more than 40 push-ups were associated with a significantly lower risk of incident CVD event risk compared with those completing fewer than 10 push-ups (IRR, 0.04; 95% CI, 0.01-0.36).

Conclusions and Relevance - The findings suggest that higher baseline push-up capacity is associated with a lower incidence of CVD events. Although larger studies in more diverse cohorts are needed, push-up capacity may be a simple, no-cost measure to estimate functional status.

Control of OCD behavior by amygdala to prefrontal input.

Sun et al. find a brain circuit in mice regulating OCD behavior that in humans might be susceptible to non drug manipulations such as transcranial magnetic stimulation.

Significance

The pathophysiology underlying obsessive-compulsive disorder (OCD) remains unclear, leading to major challenges in the treatment of OCD patients. Here, we defined a projection from the basolateral amygdala glutamate neurons to the medial prefrontal cortex glutamate and GABA neurons and described the putative importance of this circuit in manifesting the checking symptoms of OCD in mice. In addition, the above major findings were further verified in an fMRI mouse study. These findings raise the possibility of developing optimal treatments for OCD that involve the use of nondrug approaches, such as transcranial magnetic stimulation, that target the converging pathways.

Abstract

Obsessive-compulsive disorder (OCD) affects ∼1 to 3% of the world’s population. However, the neural mechanisms underlying the excessive checking symptoms in OCD are not fully understood. Using viral neuronal tracing in mice, we found that glutamatergic neurons from the basolateral amygdala (BLA^Glu) project onto both medial prefrontal cortex glutamate (mPFC^Glu) and GABA (mPFC^GABA) neurons that locally innervate mPFC^Glu neurons. Next, we developed an OCD checking mouse model with quinpirole-induced repetitive checking behaviors. This model demonstrated decreased glutamatergic mPFC microcircuit activity regulated by enhanced BLA^Glu inputs. Optical or chemogenetic manipulations of this maladaptive circuitry restored the behavioral response. These findings were verified in a mouse functional magnetic resonance imaging (fMRI) study, in which the BLA–mPFC functional connectivity was increased in OCD mice. Together, these findings define a unique BLA^Glu→mPFC^GABA→Glu circuit that controls the checking symptoms of OCD.

Long term trends in politics - Trump is not an outlier

A sobering analysis from Jordan et al.:

Significance

Donald Trump and a small group of emerging leaders around the world have been labeled as outliers in the ways that they think and communicate with others. Are they really anomalies, or do they fit into larger political trends? This study adds to existing scholarship by analyzing two important psychological dimensions, analytic thinking and confidence, in 12 large corpora of political texts representing political leaders of various levels in both the United States and other countries as well as 4 corpora of cultural texts. Rather than being anomalous, linguistic analyses find that, over the last century, there have been consistent declines in analytic thinking and rises in confidence in the ways that political leaders communicate with the public.

Abstract

From many perspectives, the election of Donald Trump was seen as a departure from long-standing political norms. An analysis of Trump’s word use in the presidential debates and speeches indicated that he was exceptionally informal but at the same time, spoke with a sense of certainty. Indeed, he is lower in analytic thinking and higher in confidence than almost any previous American president. Closer analyses of linguistic trends of presidential language indicate that Trump’s language is consistent with long-term linear trends, demonstrating that he is not as much an outlier as he initially seems. Across multiple corpora from the American presidents, non-US leaders, and legislative bodies spanning decades, there has been a general decline in analytic thinking and a rise in confidence in most political contexts, with the largest and most consistent changes found in the American presidency. The results suggest that certain aspects of the language style of Donald Trump and other recent leaders reflect long-evolving political trends. Implications of the changing nature of popular elections and the role of media are discussed.

Even 10 minutes of low intensity physical activity enhances executive function in older adults

Petrella et al. (open source) find that executive function in older adults is boosted almost immediately by low intensity exercise as brief as 10 minutes. When a group of 17 older adults with average age of 73 engaged moderate, heavy and very heavy levels of brief exercise, the authors found that the magnitude of the post-exercise executive function benefit did not vary that much with intensity. They evaluated executive function with a pre- and post-exercise antisaccade task. Antisaccades require that an individual look (i.e., saccade) mirror-symmetrical to a visual stimulus and result in longer reaction times, increased directional errors, and less accurate and more variable endpoints than their prosaccade (i.e., saccade to a target’s veridical location) counterparts. Here is the detailed abstract:

Highlights

•Antisaccades assess executive function.

•Older adults show decreased antisaccade reaction times following exercise.

•The executive benefit is observed across moderate to very-heavy exercise intensities.

•Older adults demonstrate subtle executive-related aerobic exercise effects.

Abstract

Ten minutes of aerobic or resistance training can ‘boost’ executive function in older adults. Here, we examined whether the magnitude of the exercise benefit is influenced by exercise intensity. Older adults (N = 17: mean age = 73 years) completed a volitional test to exhaustion (VO2peak) via treadmill to determine participant-specific moderate (80% of lactate threshold (LT)), heavy (15% of the difference between LT and VO2peak) and very-heavy (50% of the difference between LT and VO2peak) exercise intensities. Subsequently, in separate sessions all participants completed 10-min constant load single-bouts of exercise at each intensity. Pre- and post-exercise executive function were examined via the antisaccade task. Antisaccades require a saccade mirror-symmetrical to a target and extensive evidence has shown that antisaccades are supported via frontoparietal networks that demonstrate task-dependent changes following single-bout and chronic exercise. We also included a non-executive task (saccade to veridical target location; i.e., prosaccade) to determine whether a putative post-exercise benefit is specific to executive-related oculomotor control. Results showed that VO2 and psychological ratings of perceived exertion concurrently increased with increasing exercise intensity. As well, antisaccade reaction times showed a 24 ms (i.e., 8%) reduction from pre- to post-exercise assessments (p less than .001), whereas prosaccade values did not (p = .19). Most notably, the post-exercise change in antisaccade RTs did not reliably vary with exercise intensity. Further, for each exercise intensity participants’ cardiorespiratory fitness level was unrelated to the magnitude of the post-exercise executive benefit (ps greater than .13). Accordingly, an exercise duration as brief as 10-min provides a selective benefit to executive function in older adults across the continuum of moderate to very-heavy intensities.

Our emotional reward from music is modulated by dopamine.

Ferreri et al. present evidence that enhancing or inhibiting dopamine signaling using levodopa or risperidone modulates the pleasure experienced while listening to music:

Significance

In everyday life humans regularly seek participation in highly complex and pleasurable experiences such as music listening, singing, or playing, that do not seem to have any specific survival advantage. The question addressed here is to what extent dopaminergic transmission plays a direct role in the reward experience (both motivational and hedonic) induced by music. We report that pharmacological manipulation of dopamine modulates musical responses in both positive and negative directions, thus showing that dopamine causally mediates musical reward experience.

Abstract

Understanding how the brain translates a structured sequence of sounds, such as music, into a pleasant and rewarding experience is a fascinating question which may be crucial to better understand the processing of abstract rewards in humans. Previous neuroimaging findings point to a challenging role of the dopaminergic system in music-evoked pleasure. However, there is a lack of direct evidence showing that dopamine function is causally related to the pleasure we experience from music. We addressed this problem through a double blind within-subject pharmacological design in which we directly manipulated dopaminergic synaptic availability while healthy participants (n = 27) were engaged in music listening. We orally administrated to each participant a dopamine precursor (levodopa), a dopamine antagonist (risperidone), and a placebo (lactose) in three different sessions. We demonstrate that levodopa and risperidone led to opposite effects in measures of musical pleasure and motivation: while the dopamine precursor levodopa, compared with placebo, increased the hedonic experience and music-related motivational responses, risperidone led to a reduction of both. This study shows a causal role of dopamine in musical pleasure and indicates that dopaminergic transmission might play different or additive roles than the ones postulated in affective processing so far, particularly in abstract cognitive activities.

From a review piece by Goupil and Aucouturier in the same PNAS issue:

This result is the latest development in an already remarkable series of studies by the groups of Robert Zatorre and Antoni Rodriguez-Fornells on the implication of the reward system in musical emotions. In their seminal 2001 study, Blood and Zatorre used the PET imaging technique to show that episodes of peak emotional responses to music (or musical “chills”) were associated with increased blood flow in the ventral striatum, the amygdala, and other brain regions associated with emotion and reward. In a 2011 follow-up study, Salimpoor et al. then relied on [11C]raclopride PET—a technique that allows estimating dopamine release in cerebral tissue—to show that peak emotional arousal during music listening is associated with the simultaneous release of dopamine in the bilateral dorsal and ventral striatum. With the increasing spatial resolution of fMRI techniques, in 2013 the same team was able to narrow in on a specific dopaminoceptive subregion of the ventral striatum, the nucleus accumbens (NAcc). Specifically, they found that NAcc activity during music listening is associated with how much money participants are subsequently willing to pay for the songs that they found pleasurable. In a final salvo to establish not only the correlational but also the causal implication of dopamine in musical pleasure, the authors have turned to directly manipulating dopaminergic signaling in the striatum, first by applying excitatory and inhibitory transcranial magnetic stimulation over their participants’ left dorsolateral prefrontal cortex, a region known to modulate striatal function, and finally, in the current study, by administrating pharmaceutical agents able to alter dopamine synaptic availability, both of which influenced perceived pleasure, physiological measures of arousal, and the monetary value assigned to music in the predicted direction.

The finding that music constitutes a privileged stimulus able to activate phylogenetically ancient systems involved in valuation and motivation may very well be interpreted as an indication that the human brain contains an adaptive neural specialization for processing music as a rewarding stimulus. As such, one might wonder whether the crucial question for future research is not so much whether music is rewarding, but rather why.

Mindfulness + acceptance training - randomized controlled trial shows prosocial effects, less loneliness

From Lindsay et al.:

Significance

Loneliness (i.e., feeling alone) and social isolation (i.e., being alone) are among the most robust known risk factors for poor health and accelerated mortality. Yet mitigating these social risk factors is challenging, as few interventions have been effective for both reducing loneliness and increasing social contact. Mindfulness interventions, which train skills in monitoring present-moment experiences with an orientation of acceptance, have shown promise for improving social-relationship processes. This study demonstrates the efficacy of a 2-wk smartphone-based mindfulness training for reducing loneliness and increasing social contact in daily life. Importantly, this study shows that developing an orientation of acceptance toward present-moment experiences is a critical mechanism for mitigating these social risk factors.

Abstract

Loneliness and social isolation are a growing public health concern, yet there are few evidence-based interventions for mitigating these social risk factors. Accumulating evidence suggests that mindfulness interventions can improve social-relationship processes. However, the active ingredients of mindfulness training underlying these improvements are unclear. Developing mindfulness-specific skills—namely, (i) monitoring present-moment experiences with (ii) an orientation of acceptance—may change the way people perceive and relate toward others. We predicted that developing openness and acceptance toward present experiences is critical for reducing loneliness and increasing social contact and that removing acceptance-skills training from a mindfulness intervention would eliminate these benefits. In this dismantling trial, 153 community adults were randomly assigned to a 14-lesson smartphone-based intervention: (i) training in both monitoring and acceptance (Monitor+Accept), (ii) training in monitoring only (Monitor Only), or (iii) active control training. For 3 d before and after the intervention, ambulatory assessments were used to measure loneliness and social contact in daily life. Consistent with predictions, Monitor+Accept training reduced daily-life loneliness by 22% (d = 0.44, P = 0.0001) and increased social contact by two more interactions each day (d = 0.47, P = 0.001) and one more person each day (d = 0.39, P = 0.004), compared with both Monitor Only and control trainings. These findings describe a behavioral therapeutic target for improving social-relationship functioning; by fostering equanimity with feelings of loneliness and social disconnect, acceptance-skills training may allow loneliness to dissipate and encourage greater engagement with others in daily life.

A ketamine inspired nasal spray for depression.

I pass on this New Atlas article link on a nasal spray based on ketamine (the party drug PCP or 'angel dust') that is likely to receive FDA approval soon. From the article (which has a link to a series on that site called Psychedelic medicine 101, describing formerly taboo substances now being found useful, cf. Michael Pollan's recent book "Changing your Mind"):

Originally developed decades ago as a novel anesthetic, ketamine has been undergoing a renaissance in recent years... Of course in the world of Big Pharma there is no money to be made investing in clinical trials for a decades-old drug past its patent. So in comes esketamine, a chemical cousin of ketamine with many similar pharmacological actions. Esketamine is roughly twice as strong as ketamine, eliminated by the body faster, and allegedly presents less negative dissociative symptoms when compared to its relative. For the most part, esketamine acts on the brain in similar ways to ketamine, except it doesn't influence a few key neurological receptors.

Johnson & Johnson has been developing an esketamine-based nasal spray to treat depression for several years. The treatment's development process has been undeniably rocky with two major clinical trials failing to prove the drug is more effective than placebo and some experts questioning its ultimate efficacy.

Ahead of a final FDA decision, expected by early March, an independent advisory committee was recently established to offer a recommendation on the treatment's efficacy. After evaluating a multitude of research submitted by the pharmaceutical company, the committee overwhelmingly voted 14-to-2 in favor of recommending the treatment.

New form of neural communication at a distance.

The branch of parapsychology that claims subtle sensing and psychological action at a distance might be heartened that they are finding a shred of supportive data in recent bizarre findings suggesting a new form of neural communication. It turns out that two pieces of brain tissue in close proximity can still communicate with each other even though they have been completely severed, leaving a gap between them. From Dickson's summary of work by Chiang et al.:

Chiang et al. show that slow periodic activity in a horizontal hippocampal slice preparation occurs through dendritic NMDA receptor‐dependent Ca2+ spiking, which is itself self‐generating and self‐propagating, via ephaptic interactions across neurons. Consistent with purely ephaptic transmission, this activity and its active propagation across the slice were resistant to pharmacological blockers of fast ionotropic chemical neurotransmission, as well as pharmacological blockade of electrical transmission via gap junctions. What is particularly compelling is that the activity could be not only modulated, but also eliminated or even regenerated by imposed electrical fields. Most shockingly, this activity could be transmitted from one side of a surgically severed slice to the other when the two cut edges were simply placed in close proximity. These surprising findings were further supported by a computer model of hippocampal circuitry.

Here are the key points listed in the Chiang et al. (open source) article:

Slow periodic activity can propagate with speeds around 0.1 m s−1 and be modulated by weak electric fields.

Slow periodic activity in the longitudinal hippocampal slice can propagate without chemical synaptic transmission or gap junctions, but can generate electric fields which in turn activate neighbouring cells.

Applying local extracellular electric fields with amplitude in the range of endogenous fields is sufficient to modulate or block the propagation of this activity both in the in silico and in the in vitro models.

Results support the hypothesis that endogenous electric fields, previously thought to be too small to trigger neural activity, play a significant role in the self‐propagation of slow periodic activity in the hippocampus.

Experiments indicate that a neural network can give rise to sustained self‐propagating waves by ephaptic coupling, suggesting a novel propagation mechanism for neural activity under normal physiological conditions.

The Neuroscience of ‘Rock-a-Bye Baby’

I've always wondered why I sleep like a baby when on a boat being slowly rocked by waves, so was intrigued by Friedman's recent piece pointing to work by Perrault et al. showing that a slow rocking motion not only improves sleep but also can help people consolidate memories overnight. This is because continuous rocking stimulation strengthens deep sleep via the neural entrainment of intrinsic sleep oscillations. The Perrault et al. summary:

Highlights

•Rocking boosts deep sleep, sleep maintenance, and memory in healthy sleepers

•Fast spindles increase during rocking and synchronize with the slow oscillation up-state

• Rocking-induced overnight memory improvement relates to increased sigma activity

• Continuous rocking stimulation actively entrains intrinsic sleep oscillations

Summary

Sensory processing continues during sleep and can influence brain oscillations. We previously showed that a gentle rocking stimulation (0.25 Hz), during an afternoon nap, facilitates wake-sleep transition and boosts endogenous brain oscillations (i.e., EEG spindles and slow oscillations [SOs]). Here, we tested the hypothesis that the rhythmic rocking stimulation synchronizes sleep oscillations, a neurophysiological mechanism referred to as “neural entrainment.” We analyzed EEG brain responses related to the stimulation recorded from 18 participants while they had a full night of sleep on a rocking bed. Moreover, because sleep oscillations are considered of critical relevance for memory processes, we also investigated whether rocking influences overnight declarative memory consolidation. We first show that, compared to a stationary night, continuous rocking shortened the latency to non-REM (NREM) sleep and strengthened sleep maintenance, as indexed by increased NREM stage 3 (N3) duration and fewer arousals. These beneficial effects were paralleled by an increase in SOs and in slow and fast spindles during N3, without affecting the physiological SO-spindle phase coupling. We then confirm that, during the rocking night, overnight memory consolidation was enhanced and also correlated with the increase in fast spindles, whose co-occurrence with the SO up-state is considered to foster cortical synaptic plasticity. Finally, supporting the hypothesis that a rhythmic stimulation entrains sleep oscillations, we report a temporal clustering of spindles and SOs relative to the rocking cycle. Altogether, these findings demonstrate that a continuous rocking stimulation strengthens deep sleep via the neural entrainment of intrinsic sleep oscillations.

Female brains are younger than male brains.

Fascinating, from Goyal et al. (open source article):

Significance

Prior work has identified many sex differences in the brain, including during brain aging and in neurodegenerative diseases. Notably, many of these studies are performed by comparing age-matched females and males. Evolutionary theorists have predicted that females might have more youthful brains (neoteny) as compared with males, but until now findings in support of this theory have been limited to postmortem transcriptional analysis, some of which is contradictory. To test this hypothesis in vivo, we analyzed sex differences in a unique brain PET dataset in over 200 normal human adults across the adult life span. We find that in terms of brain metabolism, the adult female brain is on average a few years younger than the male brain.

Abstract

Sex differences influence brain morphology and physiology during both development and aging. Here we apply a machine learning algorithm to a multiparametric brain PET imaging dataset acquired in a cohort of 20- to 82-year-old, cognitively normal adults (n = 205) to define their metabolic brain age. We find that throughout the adult life span the female brain has a persistently lower metabolic brain age—relative to their chronological age—compared with the male brain. The persistence of relatively younger metabolic brain age in females throughout adulthood suggests that development might in part influence sex differences in brain aging. Our results also demonstrate that trajectories of natural brain aging vary significantly among individuals and provide a method to measure this.

Ohmygawd.....warms of drones with one distributed brain.

I have to pass on the scary video below, pointed to by a recent WaPo article. Reminds me of the fighter battles in the Star Wars movies. Wars of the future are going to be increasingly digital, hopefully less damaging to real human bodies.

Dr. Will Roper, who now serves as Assistant Air Force Secretary, described that swarm in a Jan. 2017 as “a collective organism, sharing one distributed brain for decision-making and adapting to each other like swarms in nature."

Watching social influence start to bias perceptual integration as children develop

From Large et al.:

The opinions of others have a profound influence on decision making in adults. The impact of social influence appears to change during childhood, but the underlying mechanisms and their development remain unclear. We tested 125 neurotypical children between the ages of 6 and 14 years on a perceptual decision task about 3D-motion figures under informational social influence. In these children, a systematic bias in favor of the response of another person emerged at around 12 years of age, regardless of whether the other person was an age-matched peer or an adult. Drift diffusion modeling indicated that this social influence effect in neurotypical children was due to changes in the integration of sensory information, rather than solely a change in decision behavior. When we tested a smaller cohort of 30 age- and IQ-matched autistic children on the same task, we found some early decision bias to social influence, but no evidence for the development of systematic integration of social influence into sensory processing for any age group. Our results suggest that by the early teens, typical neurodevelopment allows social influence to systematically bias perceptual processes in a visual task previously linked to the dorsal visual stream. That the same bias did not appear to emerge in autistic adolescents in this study may explain some of their difficulties in social interactions.

Fighting social media misinformation using crowdsourced judgements

From Pennycook and Rand:

Significance

Many people consume news via social media. It is therefore desirable to reduce social media users’ exposure to low-quality news content. One possible intervention is for social media ranking algorithms to show relatively less content from sources that users deem to be untrustworthy. But are laypeople’s judgments reliable indicators of quality, or are they corrupted by either partisan bias or lack of information? Perhaps surprisingly, we find that laypeople—on average—are quite good at distinguishing between lower- and higher-quality sources. These results indicate that incorporating the trust ratings of laypeople into social media ranking algorithms may prove an effective intervention against misinformation, fake news, and news content with heavy political bias.

Abstract

Reducing the spread of misinformation, especially on social media, is a major challenge. We investigate one potential approach: having social media platform algorithms preferentially display content from news sources that users rate as trustworthy. To do so, we ask whether crowdsourced trust ratings can effectively differentiate more versus less reliable sources. We ran two preregistered experiments (n = 1,010 from Mechanical Turk and n = 970 from Lucid) where individuals rated familiarity with, and trust in, 60 news sources from three categories: (i) mainstream media outlets, (ii) hyperpartisan websites, and (iii) websites that produce blatantly false content (“fake news”). Despite substantial partisan differences, we find that laypeople across the political spectrum rated mainstream sources as far more trustworthy than either hyperpartisan or fake news sources. Although this difference was larger for Democrats than Republicans—mostly due to distrust of mainstream sources by Republicans—every mainstream source (with one exception) was rated as more trustworthy than every hyperpartisan or fake news source across both studies when equally weighting ratings of Democrats and Republicans. Furthermore, politically balanced layperson ratings were strongly correlated (r = 0.90) with ratings provided by professional fact-checkers. We also found that, particularly among liberals, individuals higher in cognitive reflection were better able to discern between low- and high-quality sources. Finally, we found that excluding ratings from participants who were not familiar with a given news source dramatically reduced the effectiveness of the crowd. Our findings indicate that having algorithms up-rank content from trusted media outlets may be a promising approach for fighting the spread of misinformation on social media.

Sleeping in standby mode

In the editor's choice section of the current Science Magazine, Claudia Pama points to work by Legendre et al. showing that sleepers process surrounding events sufficiently to know when it might be a good idea to rapidly wake up. Here is the article abstract:

Sleep is a vital need, forcing us to spend a large portion of our life unable to interact with the external world. Current models interpret such extreme vulnerability as the price to pay for optimal learning. Sleep would limit external interferences on memory consolidation and allow neural systems to reset through synaptic downscaling. Yet, the sleeping brain continues generating neural responses to external events, revealing the preservation of cognitive processes ranging from the recognition of familiar stimuli to the formation of new memory representations. Why would sleepers continue processing external events and yet remain unresponsive? Here we hypothesized that sleepers enter a ‘standby mode’ in which they continue tracking relevant signals, finely balancing the need to stay inward for memory consolidation with the ability to rapidly awake when necessary. Using electroencephalography to reconstruct competing streams in a multitalker environment, we demonstrate that the sleeping brain amplifies meaningful speech compared to irrelevant signals. However, the amplification of relevant stimuli was transient and vanished during deep sleep. The effect of sleep depth could be traced back to specific oscillations, with K-complexes promoting relevant information in light sleep, whereas slow waves actively suppress relevant signals in deep sleep. Thus, the selection of relevant stimuli continues to operate during sleep but is strongly modulated by specific brain rhythms.