Reversing age related decay of brain plasticity with prozac

Eavri et al. find that treatment of mice with fluoxetine as they are aging slows the decline of several brain plasticity makers. Even if shown to have the same effects in humans, Fluoxetine would probably not be a realistic therapeutic agent for aging humans because it would have to be taken from an early age and is not recommended for use in the elderly due to its side effects. Here is their technical abstract:

Changes in excitatory neuron and synapse structure have been recognized as a potential physical source of age-related cognitive decline. Despite the importance of inhibition to brain plasticity, little is known regarding aging associated changes to inhibitory neurons. Here we test for age-related cellular and circuit changes to inhibitory neurons of mouse visual cortex. We find no substantial difference in inhibitory neuron number, inhibitory neuronal subtypes, or synapse numbers within the cerebral cortex of aged mice as compared to younger adults. However, when comparing cortical interneuron morphological parameters, we find differences in complexity, suggesting that arbors are simplified in aged mice. In vivo two-photon microscopy has previously shown that in contrast to pyramidal neurons, inhibitory interneurons retain a capacity for dendritic remodeling in the adult. We find that this capacity diminishes with age and is accompanied by a shift in dynamics from balanced branch additions and retractions to progressive prevalence of retractions, culminating in a dendritic arbor that is both simpler and more stable. Recording of visually evoked potentials (VEPs) shows that aging-related interneuron dendritic arbor simplification and reduced dynamics go hand in hand with loss of induced stimulus-selective response potentiation (SRP), a paradigm for adult visual cortical plasticity. Chronic treatment with the antidepressant fluoxetine reversed deficits in interneuron structural dynamics and restored SRP in aged animals. Our results support a structural basis for age related impairments in sensory perception, and suggest that declines in inhibitory neuron structural plasticity during aging contribute to reduced functional plasticity.

On the reception and detection of pseudo-profound bullshit

I want to thank MindBlog reader Mike Walterman, who sent me an email pointing me to this article (which won an Ig Nobel Prize) and commented on his experience with "Flow Genome Project" which I reviewed in a Nov. 17, 2017 post titled "Modern flimflam men? - The Flow Genome Project". In commenting on this post, Mike described his experience of signing on for some classes with FGP:

I read your commentary on the Flow Genome Project (FGP) with great interest. Your suspicions about this "effort" are spot on, and I wish that I had your insight before taking two of these classes from the FGP. By the way, Steven Kotler is an alum of UW-Madison!!

The first class (Flow Fundamentals) was a great community of people, and I learned much from them, and nothing from the FGP personnel. The second class (Flow Performance) was pseudo-profound BS (PPBS.) There is a great paper that won an Ig Nobel Prize titled "On the reception and detection of pseudo-profound bullshit." ... The paper perfectly described every aspect of this class!! The instructor - Jamie Wheal - is more interested in impressing people with PPBS than realaying any useful information. Also, each class is prefaced with the promise that "All the secrets of Stealing Fire will be revealed in this next class." I stopped when this promise was not delivered in Flow Performance; but, was promised for private coaching (at an extremely high price).

Here is the abstract from the Pennycook et al. article on pseudo-profound bullshit:

Although bullshit is common in everyday life and has attracted attention from philosophers, its reception (critical or ingenuous) has not, to our knowledge, been subject to empirical investigation. Here we focus on pseudo-profound bullshit, which consists of seemingly impressive assertions that are presented as true and meaningful but are actually vacuous. We presented participants with bullshit statements consisting of buzzwords randomly organized into statements with syntactic structure but no discernible meaning (e.g., “Wholeness quiets infinite phenomena”). Across multiple studies, the propensity to judge bullshit statements as profound was associated with a variety of conceptually relevant variables (e.g., intuitive cognitive style, supernatural belief). Parallel associations were less evident among profundity judgments for more conventionally profound (e.g., “A wet person does not fear the rain”) or mundane (e.g., “Newborn babies require constant attention”) statements. These results support the idea that some people are more receptive to this type of bullshit and that detecting it is not merely a matter of indiscriminate skepticism but rather a discernment of deceptive vagueness in otherwise impressive sounding claims. Our results also suggest that a bias toward accepting statements as true may be an important component of pseudo-profound bullshit receptivity.

The architecture of pride is a cultural universal.

Sznycer et al. provide evidence that the pride system of WEIRD (western-ized, educated, industrialized, rich, and democratic) societies is found in 10 small-scale societies scattered across Central and South America, Africa, and Asia:

Significance

It has been proposed that one key function of pride is to guide behavior in ways that would increase others’ valuation of the individual. To incline choice, the pride system must compute for a potential action an anticipated pride intensity that tracks the magnitude of the approval or deference that the action would generate among local audiences. Data from industrial mass societies support this expectation. However, it is presently not known whether those data reflect cultural evolutionary processes or a panhuman adaptation. Experiments conducted in 10 traditional small-scale societies with widely varying cultures and subsistence modes replicate the pattern observed in mass societies. This suggests that pride is a universal system that is part of our species’ cooperative biology.

Abstract

Becoming valuable to fellow group members so that one would attract assistance in times of need is a major adaptive problem. To solve it, the individual needs a predictive map of the degree to which others value different acts so that, in choosing how to act, the payoff arising from others’ valuation of a potential action (e.g., showing bandmates that one is a skilled forager by pursuing a hard-to-acquire prey item) can be added to the direct payoff of the action (e.g., gaining the nutrients of the prey captured). The pride system seems to incorporate all of the elements necessary to solve this adaptive problem. Importantly, data from western(-ized), educated, industrialized, rich, and democratic (WEIRD) societies indicate close quantitative correspondences between pride and the valuations of audiences. Do those results generalize beyond industrial mass societies? To find out, we conducted an experiment among 567 participants in 10 small-scale societies scattered across Central and South America, Africa, and Asia: (i) Bosawás Reserve, Nicaragua; (ii) Cotopaxi, Ecuador; (iii) Drâa-Tafilalet, Morocco; (iv) Enugu, Nigeria; (v) Le Morne, Mauritius; (vi) La Gaulette, Mauritius; (vii) Tuva, Russia; (viii) Shaanxi and Henan, China; (ix) farming communities in Japan; and (x) fishing communities in Japan. Despite widely varying languages, cultures, and subsistence modes, pride in each community closely tracked the valuation of audiences locally (mean r = +0.66) and even across communities (mean r = +0.29). This suggests that the pride system not only develops the same functional architecture everywhere but also operates with a substantial degree of universality in its content.

Our divided brains

I just came across an engaging video made by British psychiatrist Iain McGilchrist, and want to pass it on to MindBlog readers:

Brain tracking of musical beat is enhanced by low frequency sounds.

Lenc et al. find that that brain activity at the frequency of the perceived beat is selectively enhanced compared with other frequencies in the electroencephalogram (EEG) spectrum when rhythms are conveyed by bass sounds, explaining why across cultures bass instruments are used to induce people to dance to periodic pulse-like beats.

Music makes us move, and using bass instruments to build the rhythmic foundations of music is especially effective at inducing people to dance to periodic pulse-like beats. Here, we show that this culturally widespread practice may exploit a neurophysiological mechanism whereby low-frequency sounds shape the neural representations of rhythmic input by boosting selective locking to the beat. Cortical activity was captured using electroencephalography (EEG) while participants listened to a regular rhythm or to a relatively complex syncopated rhythm conveyed either by low tones (130 Hz) or high tones (1236.8 Hz). We found that cortical activity at the frequency of the perceived beat is selectively enhanced compared with other frequencies in the EEG spectrum when rhythms are conveyed by bass sounds. This effect is unlikely to arise from early cochlear processes, as revealed by auditory physiological modeling, and was particularly pronounced for the complex rhythm requiring endogenous generation of the beat. The effect is likewise not attributable to differences in perceived loudness between low and high tones, as a control experiment manipulating sound intensity alone did not yield similar results. Finally, the privileged role of bass sounds is contingent on allocation of attentional resources to the temporal properties of the stimulus, as revealed by a further control experiment examining the role of a behavioral task. Together, our results provide a neurobiological basis for the convention of using bass instruments to carry the rhythmic foundations of music and to drive people to move to the beat.

The false idols of wellness.

Jen Gunter does an engaging take-down of the wellness-industrial complex in a NYTimes piece. She suggests that the wellness industry is exploiting rather than filling the gaps left by normal medical practice.:

Wellness used to mean a blend of health and happiness...it has become a false antidote to the fear of modern life and death...The wellness industry takes medical terminology, such as “inflammation” or “free radicals,” and levigates it to the point of incomprehension. The resulting product is a D.I.Y. medicine for longevity that comes with a confidence that science can only aspire to achieve.

...take the trend of adding a pinch of activated charcoal to your food or drink...it’s sold as a supposed “detox.”..It has the same efficacy as a spell from the local witch...“Toxins,” as defined by the peddlers of these dubious cures, are the harmful effluvia of modern life that supposedly roam our bodies...for without these toxins there can be no search for purity — “clean” tampons, “clean” food, “clean” makeup. There are also sacred acts and rituals to follow...Medicine and religion have long been deeply intertwined, and it’s only relatively recently that they have separated. The wellness-industrial complex seeks to resurrect that connection. It’s like a medical throwback, as if the halcyon days of health were 5,000 years ago. Ancient cleansing rituals with a modern twist — supplements, useless products and scientifically unsupported tests.

The dietary supplements that are the backbone of wellness make up a $30 billion a year business despite studies showing they have no value for longevity...So what’s the harm of spending money on charcoal for nonexistent toxins or vitamins for expensive urine or grounding bedsheets to better connect you with the earth’s electrons?..Here’s what: the placebo effect or “trying something natural” can lead people with serious illnesses to postpone effective medical care.

Moving the kind of product that churns the wheels of the wellness-industrial complex requires a constant stream of fear and misinformation. Look closer at most wellness sites and at many of their physician partners, and you’ll find a plethora of medical conspiracy theories: Vaccines and autism. The dangers of water fluoridation. Bras and breast cancer. Cellphones and brain cancer. Heavy metal poisoning. AIDS as a construct of Big Pharma.

There are symptoms that I believe have been with us since the beginning of time, so common that they are likely part of the human experience: fatigue, bloat, low libido, episodic pain, loss of vigor. When medicine can only offer a therapy, not a cure, or when doctors give undesired answers — suggesting attention to sleep hygiene, for instance — it isn’t hard to see how the intoxicating confidence and theater of wellness could beckon.

I admit that doctors can learn something from wellness. It’s clear that some people are looking for healers, so we must find ways to serve that need that are medically ethical...We doctors can do more to provide factual information about hazardous substances, such as carcinogens and endocrine disrupting chemicals, in products and the environment from medically vetted sites with no products to sell, such as the National Cancer Institute and the Endocrine Society...Many people — women especially — have long been marginalized and dismissed by medicine, but the answer does not lie in predatory conspiracy theories, a faux religion or expensive magic.

Mesolimbic reward circuitry influences valuation of knowledge versus ignorance.

From Charpentier et al.:

The pursuit of knowledge is a basic feature of human nature. However, in domains ranging from health to finance people sometimes choose to remain ignorant. Here, we show that valence is central to the process by which the human brain evaluates the opportunity to gain information, explaining why knowledge may not always be preferred. We reveal that the mesolimbic reward circuitry selectively treats the opportunity to gain knowledge about future favorable outcomes, but not unfavorable outcomes, as if it has positive utility. This neural coding predicts participants’ tendency to choose knowledge about future desirable outcomes more often than undesirable ones, and to choose ignorance about future undesirable outcomes more often than desirable ones. Strikingly, participants are willing to pay both for knowledge and ignorance as a function of the expected valence of knowledge. The orbitofrontal cortex (OFC), however, responds to the opportunity to receive knowledge over ignorance regardless of the valence of the information. Connectivity between the OFC and mesolimbic circuitry could contribute to a general preference for knowledge that is also modulated by valence. Our findings characterize the importance of valence in information seeking and its underlying neural computation. This mechanism could lead to suboptimal behavior, such as when people reject medical screenings or monitor investments more during bull than bear markets.

Meditation quiets the ego? ….maybe just the opposite.

From Gebauer et al.. In their abstract "self-enhancement bias" refers to exaggerated self views or valuations.

Mind-body practices enjoy immense public and scientific interest. Yoga and meditation are highly popular. Purportedly, they foster well-being by curtailing self-enhancement bias. However, this “ego-quieting” effect contradicts an apparent psychological universal, the self-centrality principle. According to this principle, practicing any skill renders that skill self-central, and self-centrality breeds self-enhancement bias. We examined those opposing predictions in the first tests of mind-body practices’ self-enhancement effects. In Experiment 1, we followed 93 yoga students over 15 weeks, assessing self-centrality and self-enhancement bias after yoga practice (yoga condition, n = 246) and without practice (control condition, n = 231). In Experiment 2, we followed 162 meditators over 4 weeks (meditation condition: n = 246; control condition: n = 245). Self-enhancement bias was higher in the yoga (Experiment 1) and meditation (Experiment 2) conditions, and those effects were mediated by greater self-centrality. Additionally, greater self-enhancement bias mediated mind-body practices’ well-being benefits. Evidently, neither yoga nor meditation fully quiet the ego; to the contrary, they boost self-enhancement.

The neuroscience of pessimism.

Ann Graybiel and collaborators offer a fascinating study showing that stimulation of the brain's caudate nucleus induces persistent and repetitive negative decision making. They devised a cost-benefit situation in which monkeys were offered a reward of juice paired with an unpleasant puff of air to the face. When the caudate nucleus was stimulated the animals began to avoid choosing the reward, when previously they would have put up with the unpleasant stimulus. This suggests that pessimistic decision-making can be tied to an overactive caudate nucleus. Work is now beginning with human patients suffering from anxiety and depression to find out whether abnormal activity in the caudate nucleus can be seen during negative decision making.

Highlights

Caudate nucleus stimulation induces persistent state change affecting value evaluation 

CN stimulation produces repetitive choices, whereas pACC stimulation does not 

CN beta oscillations parallel negative states influencing repetitive decisions 

Abnormal CN beta oscillations are correlated with persistency in OCD-like states

Summary P

ersistent thoughts inducing irrationally pessimistic and repetitive decisions are often symptoms of mood and anxiety disorders. Regional neural hyperactivities have been associated with these disorders, but it remains unclear whether there is a specific brain region causally involved in these persistent valuations. Here, we identified potential sources of such persistent states by microstimulating the striatum of macaques performing a task by which we could quantitatively estimate their subjective pessimistic states using their choices to accept or reject conflicting offers. We found that this microstimulation induced irrationally repetitive choices with negative evaluations. Local field potentials recorded in the same microstimulation sessions exhibited modulations of beta-band oscillatory activity that paralleled the persistent negative states influencing repetitive decisions. These findings demonstrate that local striatal zones can causally affect subjective states influencing persistent negative valuation and that abnormal beta-band oscillations can be associated with persistency in valuation accompanied by an anxiety-like state.

More evidence against the transferable benefits of online brain training on cognitive function

From Stojanoski et al.:

There is strong incentive to improve our cognitive abilities, and brain training has emerged as a promising approach for achieving this goal. While the idea that extensive ‘training’ on computerized tasks will improve general cognitive functioning is appealing, the evidence to support this remains contentious. This is, in part, because of poor criteria for selecting training tasks and outcome measures resulting in inconsistent definitions of what constitutes transferable improvement to cognition. The current study used a targeted training approach to investigate whether training on two different, but related, working memory tasks (across two experiments, with 72 participants) produced transferable benefits to similar (quantified based on cognitive and neural profiles) untrained test tasks. Despite significant improvement on both training tasks, participants did not improve on either test task. In fact, performance on the test tasks after training were nearly identical to a passive control group. These results indicate that, despite maximizing the likelihood of producing transferable benefits, brain training does not generalize, even to very similar tasks. Our study calls into question the benefit of cognitive training beyond practice effects, and provides a new framework for future investigations into the efficacy of brain training.

Rediscovering ancient greek music.

I want to point to a fascinating article by Armand D’Angour at Oxford University, on efforts to reconstruct what music sounded like in ancient Greece. The work is also described in this YouTube video:

Controlling drones with a body-machine interface.

On first glance this article creeped me out, because when control of drones at a distance is mentioned I think of the drones used to bomb ISIS or Al Quaeda cells controlled by operators in Tampa, FL. However, more benign or typical applications include deployments in environments where it is not desirable or possible to send a human operator, such as nuclear plants, scenes of natural hazards, or more generally in search and rescue missions. Also, the use of teleoperated systems can augment human dexterity and precision in fields such as minimally invasive surgery or microfabrication.

Miehlbradt et al. suggest an alternative to current control interfaces (frequently employing joysticks) that that require intensive practice. They have developed an intuitive gesture based interface for real and simulated drones. They recorded the upper-body kinematics and muscle activities during the generation of movements that would imitate the behavior of a flying drone. After identifying two main interaction strategies used by the participants, they assessed the capacity of potential users to actively steer the path of a virtual drone employing these two strategies. Eventually, they evaluated the transferability of the skills acquired during simulation training to the control of a real drone. Their abstract, and a video:

The accurate teleoperation of robotic devices requires simple, yet intuitive and reliable control interfaces. However, current human–machine interfaces (HMIs) often fail to fulfill these characteristics, leading to systems requiring an intensive practice to reach a sufficient operation expertise. Here, we present a systematic methodology to identify the spontaneous gesture-based interaction strategies of naive individuals with a distant device, and to exploit this information to develop a data-driven body–machine interface (BoMI) to efficiently control this device. We applied this approach to the specific case of drone steering and derived a simple control method relying on upper-body motion. The identified BoMI allowed participants with no prior experience to rapidly master the control of both simulated and real drones, outperforming joystick users, and comparing with the control ability reached by participants using the bird-like flight simulator Birdly.

No gender differences in early math cognition.

Kersey et al. have examined data from more than 500 children ranging in age from 6 months to 8 years across several tests of numerosity, counting, and elementary mathematics concepts. They found no differences in mathematical performance between boys and girls in any of the ages tested, suggesting that gender differences in STEM representation are unlikely to be due to intrinsic differences in cognitive ability.

Recent public discussions have suggested that the under-representation of women in science and mathematics careers can be traced back to intrinsic differences in aptitude. However, true gender differences are difficult to assess because sociocultural influences enter at an early point in childhood. If these claims of intrinsic differences are true, then gender differences in quantitative and mathematical abilities should emerge early in human development. We examined cross-sectional gender differences in mathematical cognition from over 500 children aged 6 months to 8 years by compiling data from five published studies with unpublished data from longitudinal records. We targeted three key milestones of numerical development: numerosity perception, culturally trained counting, and formal and informal elementary mathematics concepts. In addition to testing for statistical differences between boys’ and girls’ mean performance and variability, we also tested for statistical equivalence between boys’ and girls’ performance. Across all stages of numerical development, analyses consistently revealed that boys and girls do not differ in early quantitative and mathematical ability. These findings indicate that boys and girls are equally equipped to reason about mathematics during early childhood.

A ecosystem of podcast bros who want to optimize your life.

I'm not a podcast or video kind of person, being too impatient to listen to or watch material that I can absorb more rapidly by reading about it. So, this piece by Molly Worthen describing a whole ecosystem of wellness gurus, a network of podcasters centered on Austin Texas and Southern California, was a revelation for me. (Note: this past November I did a post on an Austin based wellness project.) From her article:

...over the past few years the podcasters have become a significant cultural phenomenon, spiritual entrepreneurs who are filling the gap left as traditional religious organizations erode and modernity frays our face-to-face connections with communities and institutions...By my count, there are at least two dozen members of this podcast ecosystem...Several of these podcasters say they reach millions of listeners each month. In 2016, Joe Rogan put his figure “in the neighborhood of 30 million downloads per month”; his show is ranked second on the iTunes podcast chart, right behind Oprah.

In this secularized age of lonely seekers scrolling social media feeds, they have cultivated a spiritual community. They offer theologies and daily rituals of self-actualization, an appealing alternative to the rhetoric of victimhood and resentment that permeates both the right and the left...All this continues a long American tradition of self-help and creative, market-minded spirituality. The 19th century brimmed with gurus ready to guide you to other dimensions and prophets of the path from rags to riches.

Humans seem to be wired to seek salvation; even if polls suggest that more and more Americans reject traditional notions of God and skip church, it’s appealing to think that the latest lifestyle trend could be your path to existential bliss. The podcasters urge their listeners to experiment with fitness routines, diets, non-Western medicine, meditation and other “biohacks” to think more clearly, sleep more soundly and achieve professional success — and to quit blaming other people or bad luck for their problems.

Underlying this taste for experimentation is a deeper interest in evolutionary biology and psychology: the genes that, some experts believe, leave us programmed for a brutal, tribal, even pre-human past despite the creature comforts of the present...Evolutionary psychology is the secular answer to the doctrine of original sin: a primordial explanation for the anxieties that haunt us even if we have a decent job and a functional family...This is the podcast bro ethos: Ditch your ideologically charged identity. Accept your evolutionary programming. Take responsibility for mastering it, and find a cosmic purpose...Many have a strong interest in spirituality, and see practices like Buddhist meditation or consuming hallucinogenic “plant medicine” as not just a way to improve daily performance, but a path to something deeper.

The common thread linking the podcasters’ interest in evolutionary psychology and their metaphysical dabbling is the quest to transcend the ego, and to overcome the idea that we are personally aggrieved by enemies wholly unlike ourselves. This means mistrusting ideology and identitarian politics...having a one-world tribe, a tribe of human beings, period, is really what’s going to heal us for our next stage of life as a species on this planet.

Is this a postmodern monastic order, passing on breakfast and shivering in the shower while pondering the next step in mastering the ego? These podcasters lead one of the largest quasi-spiritual self-help “denominations” in the United States. It is a far-flung virtual community that gives people solace, a regimen and a sense of like-mindedness at a time when churches and other old-fashioned institutions simultaneously seem to ask too much, yet also fail to provide many people with whatever they’re looking for. The podcasters’ rejection of culture-wars partisanship resonates at a time when many Americans have stopped participating in politics (every listener I spoke to avoids political media the way they avoid, well, non-kale smoothies).

Yet podcasts are not churches. They are not political parties. They don’t patch over the existential void so much as reveal how avidly we yearn to fill it...The podcasters may offer a lesson to politicians and activists: to build a following, find a way to provide the sense of affiliation, daily rhythm and ultimate purpose that humans crave. Slogans of victimhood and grievance may rile up the base. But most people yearn, instead, for a sense of belonging and a path to mastery — even if it starts with a cold shower.

Our weaponized social media

I pass on a few clips from a sobering NYTimes article by Kara Swisher, who quotes from a recent Facebook post:

We face determined, well-funded adversaries who will never give up and are constantly changing tactics. It’s an arms race and we need to constantly improve too.

Continuing,

Facebook, as well as Twitter and Google’s YouTube, have become the digital arms dealers of the modern age...by weaponizing pretty much everything that could be weaponized. They have mutated human communication, so that connecting people has too often become about pitting them against one another, and turbocharged that discord to an unprecedented and damaging volume...They have weaponized social media. They have weaponized the First Amendment. They have weaponized civic discourse. And they have weaponized, most of all, politics.

Swisher's concluding paragraphs:

“I mean, my emotion is feeling a deep sense of responsibility to try to fix the problem,” said Mr. Zuckerberg. “In running a company, if you want to be innovative and advance things forward, I think you have to be willing to get some things wrong. But I don’t think it is acceptable to get the same things wrong over and over again.”

It was a classic Silicon Valley engineer’s roll-up-your-sleeves answer, which leaves many cold when it comes to, say, the manipulation of democracy. Fending off bad actors like the Russians has been and will be increasingly expensive; it may even be impossible. But Facebook could have done much more than it did, and it certainly needs to do more than it’s doing.

Mr. Zuckerberg is now trying to fend off talk in Washington of regulating his company like the thing he once told me it was: a utility. He has also spent the last month meeting over dinners with a range of academic experts on free speech, propaganda and more to try to understand where to go from here.

Call it the education of Mark Zuckerberg and Silicon Valley, but on the world’s dime. How much that has — and will — cost is probably immeasurable.

How pupil mimicry promotes trust.

Prochazkova et al. show that pupil mimicry promotes trust through our theory of mind brain network:

Significance

Trusting others is central for cooperative endeavors to succeed. To decide whether to trust or not, people generally make eye contact. As pupils of interaction partners align, mimicking pupil size helps them to make well-informed trust decisions. How the brain integrates information from the partner and from their own bodily feedback to make such decisions was unknown because previous research investigated these processes separately. Herein, we take a multimethod approach and demonstrate that pupil mimicry is regulated by the theory-of-mind network, and informs decisions of trust by activating the precuneus. This evolutionary ancient neurophysiological mechanism that is active in human adults, infants, and chimpanzees promotes affiliation, bonding, and trust through mimicry.

Abstract

The human eye can provide powerful insights into the emotions and intentions of others; however, how pupillary changes influence observers’ behavior remains largely unknown. The present fMRI–pupillometry study revealed that when the pupils of interacting partners synchronously dilate, trust is promoted, which suggests that pupil mimicry affiliates people. Here we provide evidence that pupil mimicry modulates trust decisions through the activation of the theory-of-mind network (precuneus, temporo-parietal junction, superior temporal sulcus, and medial prefrontal cortex). This network was recruited during pupil-dilation mimicry compared with interactions without mimicry or compared with pupil-constriction mimicry. Furthermore, the level of theory-of-mind engagement was proportional to individual’s susceptibility to pupil-dilation mimicry. These data reveal a fundamental mechanism by which an individual’s pupils trigger neurophysiological responses within an observer: when interacting partners synchronously dilate their pupils, humans come to feel reflections of the inner states of others, which fosters trust formation.

Brain regions involved in compensating for lost body parts.

From Striem-Amit et al.:

Significance

What determines the role of brain regions and their plasticity when typical inputs or experience is not provided? To what extent can extreme compensatory use affect brain organization? We tested the reorganization of primary and association sensorimotor cortex hand-selective areas in people born without hands, who use their feet for everyday tasks. We found that their primary sensorimotor hand area is preferentially activated for nearby body parts that cannot serve as effectors. In contrast, foot-selective compensatory plasticity was found in the association cortex, in an area typically involved in manual tool use. This shows limitations of compensatory plasticity and experience in modifying brain organization of early topographical cortex, as compared with association cortices where function-based organization is the driving factor.

Abstract

What forces direct brain organization and its plasticity? When brain regions are deprived of their input, which regions reorganize based on compensation for the disability and experience, and which regions show topographically constrained plasticity? People born without hands activate their primary sensorimotor hand region while moving body parts used to compensate for this disability (e.g., their feet). This was taken to suggest a neural organization based on functions, such as performing manual-like dexterous actions, rather than on body parts, in primary sensorimotor cortex. We tested the selectivity for the compensatory body parts in the primary and association sensorimotor cortex of people born without hands (dysplasic individuals). Despite clear compensatory foot use, the primary sensorimotor hand area in the dysplasic subjects showed preference for adjacent body parts that are not compensatorily used as effectors. This suggests that function-based organization, proposed for congenital blindness and deafness, does not apply to the primary sensorimotor cortex deprivation in dysplasia. These findings stress the roles of neuroanatomical constraints like topographical proximity and connectivity in determining the functional development of primary cortex even in extreme, congenital deprivation. In contrast, increased and selective foot movement preference was found in dysplasics’ association cortex in the inferior parietal lobule. This suggests that the typical motor selectivity of this region for manual actions may correspond to high-level action representations that are effector-invariant. These findings reveal limitations to compensatory plasticity and experience in modifying brain organization of early topographical cortex compared with association cortices driven by function-based organization.

Residential isolation of disadvantaged groups is not mitigated by extensive urban mobility.

Wang et al. offer yet another approach to observing the intractability of racial segregation in large cities:

Significance

Living in disadvantaged neighborhoods is widely assumed to undermine life chances because residents are isolated from neighborhoods with greater resources. Yet, residential isolation may be mitigated by individuals spending much of their everyday lives outside their home neighborhoods, a possibility that has been difficult to assess on a large scale. Using new methods to analyze urban mobility in the 50 largest American cities, we find that residents of primarily black and Hispanic neighborhoods—whether poor or not—are far less exposed to either nonpoor or white middle-class neighborhoods than residents of primarily white neighborhoods. Although residents of disadvantaged neighborhoods regularly travel as far and to as many different neighborhoods as those from advantaged neighborhoods, their relative isolation and segregation persist.

Abstract

Influential research on the negative effects of living in a disadvantaged neighborhood assumes that its residents are socially isolated from nonpoor or “mainstream” neighborhoods, but the extent and nature of such isolation remain in question. We develop a test of neighborhood isolation that improves on static measures derived from commonly used census reports by leveraging fine-grained dynamic data on the everyday movement of residents in America’s 50 largest cities. We analyze 650 million geocoded Twitter messages to estimate the home locations and travel patterns of almost 400,000 residents over 18 mo. We find surprisingly high consistency across neighborhoods of different race and income characteristics in the average travel distance (radius) and number of neighborhoods traveled to (spread) in the metropolitan region; however, we uncover notable differences in the composition of the neighborhoods visited. Residents of primarily black and Hispanic neighborhoods—whether poor or not—are far less exposed to either nonpoor or white middle-class neighborhoods than residents of primarily white neighborhoods. These large racial differences are notable given recent declines in segregation and the increasing diversity of American cities. We also find that white poor neighborhoods are substantially isolated from nonpoor white neighborhoods. The results suggest that even though residents of disadvantaged neighborhoods travel far and wide, their relative isolation and segregation persist.

Chimps can psych out humans

Interesting work from Eckert et al. shows that chimps can use mental state information revealed by experimenters' biases in selecting food items.

Great apes have been shown to be intuitive statisticians: they can use proportional information within a population to make intuitive probability judgments about randomly drawn samples [unpublished data]. Humans, from early infancy onward, functionally integrate intuitive statistics with other cognitive domains to judge the randomness of an event. To date, nothing is known about such cross-domain integration in any nonhuman animal, leaving uncertainty about the origins of human statistical abilities. We investigated whether chimpanzees take into account information about psychological states of experimenters (their biases and visual access) when drawing statistical inferences. We tested 21 sanctuary-living chimpanzees in a previously established paradigm that required subjects to infer which of two mixed populations of preferred and non-preferred food items was more likely to lead to a desired outcome for the subject. In a series of three experiments, we found that chimpanzees chose based on proportional information alone when they had no information about experimenters’ preferences and (to a lesser extent) when experimenters had biases for certain food types but drew blindly. By contrast, when biased experimenters had visual access, subjects ignored statistical information and instead chose based on experimenters’ biases. Lastly, chimpanzees intuitively used a violation of statistical likelihoods as indication for biased sampling. Our results suggest that chimpanzees have a random sampling assumption that can be overridden under the appropriate circumstances and that they are able to use mental state information to judge whether this is necessary. This provides further evidence for a shared statistical inference mechanism in apes and humans.

Enhanced brain activity associated with highly superior memory.

Santangelo et al. show that people with superior memory have enhanced connectivity of their prefrontal cortex with their hippocampus and temporoparietal junction:

Significance

Recent research has identified human subjects who have highly superior autobiographical memory (HSAM). Here, we investigated, using fMRI, the neural activation induced by retrieval of autobiographical memories (AMs) and semantic memories (SMs) in subjects with HSAM and control subjects. While their brains were being scanned, subjects had to retrieve AMs as well as SMs (e.g., examples of animals). The subjects with HSAM displayed a superior ability to retrieve details of AMs, supported by enhanced activation of several brain regions, including the medial prefrontal cortex and temporoparietal junction, as well as increased connectivity of the prefrontal cortex with the hippocampus, a region well known to be involved in memory representation. These findings suggest that activation of these systems may play a critical role in enabling HSAM.

Abstract

Brain systems underlying human memory function have been classically investigated studying patients with selective memory impairments. The discovery of rare individuals who have highly superior autobiographical memory (HSAM) provides, instead, an opportunity to investigate the brain systems underlying enhanced memory. Here, we carried out an fMRI investigation of a group of subjects identified as having HSAM. During fMRI scanning, eight subjects with HSAM and 21 control subjects were asked to retrieve autobiographical memories (AMs) as well as non-AMs (e.g., examples of animals). Subjects were instructed to signal the “access” to an AM by a key press and to continue “reliving” it immediately after. Compared with controls, individuals with HSAM provided a richer AM recollection and were faster in accessing AMs. The access to AMs was associated with enhanced prefrontal/hippocampal functional connectivity. AM access also induced increased activity in the left temporoparietal junction and enhanced functional coupling with sensory cortices in subjects with HSAM compared with controls. In contrast, subjects with HSAM did not differ from controls in functional activity during the reliving phase. These findings, based on fMRI assessment, provide evidence of interaction of brain systems engaged in memory retrieval and suggest that enhanced activity of these systems is selectively involved in enabling more efficient access to past experiences in HSAM.