First direct evidence for human sex pheromones.

Here is a clever experiment by Zhou et al., who digitally morph the gender of moving point light displays of walking from male to female while subjects are exposed to two human steroids that they can not discriminate. Here is their summary and abstract:

•Human steroid androstadienone conveys masculinity to straight women and gay men
•Human steroid estratetraenol conveys femininity to straight men
•The effects take place in the absence of awareness
•Human gender perception draws on subconscious chemosensory biological cues

Recent studies have suggested the existence of human sex pheromones, with particular interest in two human steroids: androstadienone (androsta-4,16,-dien-3-one) and estratetraenol (estra-1,3,5(10),16-tetraen-3-ol). The current study takes a critical step to test the qualification of the two steroids as sex pheromones by examining whether they communicate gender information in a sex-specific manner. By using dynamic point-light displays that portray the gaits of walkers whose gender is digitally morphed from male to female, we show that smelling androstadienone systematically biases heterosexual females, but not males, toward perceiving the walkers as more masculine. By contrast, smelling estratetraenol systematically biases heterosexual males, but not females, toward perceiving the walkers as more feminine. Homosexual males exhibit a response pattern akin to that of heterosexual females, whereas bisexual or homosexual females fall in between heterosexual males and females. These effects are obtained despite that the olfactory stimuli are not explicitly discriminable. The results provide the first direct evidence that the two human steroids communicate opposite gender information that is differentially effective to the two sex groups based on their sexual orientation. Moreover, they demonstrate that human visual gender perception draws on subconscious chemosensory biological cues, an effect that has been hitherto unsuspected.

Social attention and our ventromedial prefrontal cortex.

Ralph Adolphs points to an interesting article by Wolf et al. showing that bilateral ventromedial prefrontal cortex damage impairs visual attention to the eye regions of faces, particularly for fearful faces. From Adolphs summary:

Failing to look at the eyes. Shown in each image are the regions of a face at which different groups of subjects look, as measured using eye-tracking. The hottest colours (red regions) denote those regions of the face where people look the most. Whereas this corresponds to the eye region of the face in healthy controls (far left), it is abnormal in certain clinical populations, including individuals with lesions of the vmPFC (top right) or amygdala (bottom right) and individuals with autism spectrum disorder (bottom centre) Top row: from Wolf et al. 2014. Bottom row: data from Michael Spezio, Daniel Kennedy, Ralph Adolphs. All images represent spatially smoothed data averaged across multiple fixations, multiple stimuli and multiple subjects within the indicated group.

Blue Mind - looking at water improves your health and calm

I just spend three days this past weekend in a guesthouse cabin in Door County, Wisconsin - three days of seeing mainly gorgeous green forests and the blue expanses of Lake Michigan on both sides of the Door County peninsula. Over those days, just looking at the water, I could feel a calm growing that quieted my normally chattering mind. Now, back in my university office, what do I stumble across but an article (on stress) that mentions this calming effect of water, a review by Michael Gross titled "Chronic stress means we’re always on the hunt", which first notes that one relief described for chronic stress (dubbed "Red Mind") is to give the stress system some real exercise (doing something like sky diving) to put the more mundane stresses of daily life in perspective. But then, in a second portion of his article, he points to work of Wallace J. Nichols and others who use the phrase "Blue mind" to describe the interface between our psychology and natural environment, particularly water, the largest feature of that environment. Gross notes that Nichols has put his ideas

...in a new book, called Blue Mind: How Water Makes You Happier, More Connected, and Better at What You Do, which is due to appear in June. In his book, Nichols discusses a spate of recent psychology papers showing that the proximity of “blue nature” can improve people’s physical and mental health and counterbalance the damaging effects of the chronic stress and the permanent engagement of the red mind. While the opportunity to exercise plays a part, several studies have shown that the positive effect of being near water can be separated from that aspect.

Crowdsourcing our brain’s wiring.

You too can be be a neuroscientist! I have to join in the general chorus of press pointing to the efforts of Sebastian Seung, now moving from MIT to Princeton Univ. Detailed analysis of serial ultra-thin electron microscope sections of brain neurons is extremely laborious - tracing one cells takes about 50 hours. Seung has asked for help from the general public ("citizen neuroscientists") in doing this with neurons in the mouse retina. The data on how bipolar cells connect to amacrine motion detecting cells in the retina has suggested a model for motion detection. This animation of their results is a treat to watch:

The science of inequality.

The May 23 issue of Science Magazine has a large section devoted the origins and analysis of economic inequality. And, the general gist of virtually all the articles is that inequality is here to stay, predicted by social and also simple physical models of exchange. A weekly chaos and complexity discussion group that I attend just this past Tuesday discussed the economic Yard-Sale Model of wealth redistribution, in which power-law-like distributions result even when all individuals are identical and playing by the same rules. In a previous post, I have passed on a simple model illustrated by Clint Sprott, organizer of the seminars.

The monkey business illusion.

Many people have by now viewed the famous "Gorilla Video" made by Daniel Simons over fifteen years ago, in which most viewers asked to count how many times students are passing a basketball to each other completely miss the fact that a gorilla walks through the middle of the scene halfway through the exercise. I'm passing on Simons' update of his original demonstration, which shows further how we see what we want or expect to see. It has been viewed over 4 million times, and gives links to his other work and publications. (The video is public on youtube, but copyrighted, so I hope Mr. Simons doesn't mind this advertisement for his work.)

 

How social equality is represented in the brain.

Interesting work from Aoki, Adolphs, and collaborators:

A distinct aspect of the sense of fairness in humans is that we care not only about equality in material rewards but also about equality in nonmaterial values. One such value is the opportunity to choose freely among many options, often regarded as a fundamental right to economic freedom. In modern developed societies, equal opportunities in work, living, and lifestyle are enforced by antidiscrimination laws. Despite the widespread endorsement of equal opportunity, no studies have explored how people assign value to it. We used functional magnetic resonance imaging to identify the neural substrates for subjective valuation of equality in choice opportunity. Participants performed a two-person choice task in which the number of choices available was varied across trials independently of choice outcomes. By using this procedure, we manipulated the degree of equality in choice opportunity between players and dissociated it from the value of reward outcomes and their equality. We found that activation in the ventromedial prefrontal cortex (vmPFC) tracked the degree to which the number of options between the two players was equal. In contrast, activation in the ventral striatum tracked the number of options available to participants themselves but not the equality between players. Our results demonstrate that the vmPFC, a key brain region previously implicated in the processing of social values, is also involved in valuation of equality in choice opportunity between individuals. These findings may provide valuable insight into the human ability to value equal opportunity, a characteristic long emphasized in politics, economics, and philosophy.

Note: The same issue of Journal of Neuroscience has a related article by Matthew Apps and Ramnani showing that activity in the anterior cingulate gyrus covaries with the net value of rewards that someone else will receive when that person is required to exert effort for the reward.

Brain correlates of expertise in musical improvisation

Pihno et al. show that expertise in musical improvisation is associated with increased connectivity between premotor and prefrontal areas, suggesting that the ability to produce novel output can be automated by training:

Musicians have been used extensively to study neural correlates of long-term practice, but no studies have investigated the specific effects of training musical creativity. Here, we used human functional MRI to measure brain activity during improvisation in a sample of 39 professional pianists with varying backgrounds in classical and jazz piano playing. We found total hours of improvisation experience to be negatively associated with activity in frontoparietal executive cortical areas. In contrast, improvisation training was positively associated with functional connectivity of the bilateral dorsolateral prefrontal cortices, dorsal premotor cortices, and presupplementary areas. The effects were significant when controlling for hours of classical piano practice and age. These results indicate that even neural mechanisms involved in creative behaviors, which require a flexible online generation of novel and meaningful output, can be automated by training. Second, improvisational musical training can influence functional brain properties at a network level. We show that the greater functional connectivity seen in experienced improvisers may reflect a more efficient exchange of information within associative networks of importance for musical creativity.

Brain correlates of "the good life" ??

Lewis et al. offer another example of the class of experiments correlating the volume of a specific brain area with a specific behavior, in this case eudaimonic well-being, which is positively correlated with volume in the right insular cortex. Eudaimonia is fundamentally linked to notions of agency, and recent work has identified insular cortex as a source of agentic control. The insula has also been linked to facilitation of self-awareness, as well as to the regulation of bodily states and modulation of decision making based on interoceptive information about these bodily states.

Whether the behavior causes the larger insular volume or vice versa can’t be determined. These particular experiments did not control for simple subjective (hedonic) well-being, so the observed volume increase in the insula may not be a unique correlate of eudaimonia. Here is their abstract, and the entire text of the article is open source.

Eudaimonic well-being reflects traits concerned with personal growth, self-acceptance, purpose in life and autonomy (among others) and is a substantial predictor of life events, including health. Although interest in the aetiology of eudaimonic well-being has blossomed in recent years, little is known of the underlying neural substrates of this construct. To address this gap in our knowledge, here we examined whether regional gray matter (GM) volume was associated with eudaimonic well-being. Structural magnetic resonance images from 70 young, healthy adults who also completed Ryff’s 42-item measure of the six core facets of eudaimonia, were analysed with voxel-based morphometry techniques. We found that eudaimonic well-being was positively associated with right insular cortex GM volume. This association was also reflected in three of the sub-scales of eudaimonia: personal growth, positive relations and purpose in life. Positive relations also showed a significant association with left insula volume. No other significant associations were observed, although personal growth was marginally associated with left insula, and purpose in life exhibited a marginally significant negative association with middle temporal gyrus GM volume. These findings are the first to our knowledge linking eudaimonic well-being with regional brain structure.

Stress can protect from Alzheimer's disease

Yanker and his collaborators have found that levels of a neuro-protective protein called REST (repressor element 1-silencing transcription factor) are increased in the brain by any form of cellular stress (oxidative, immune, etc.) It acts by repressing genes involved in cell death and Alzheimer's dementia. REST levels in prefrontal cortical neurons are positively correlated with a measure of global cognition, and also separate measures of episodic, semantic and working memory. Measurements of autopsied brains of elderly people who have died of Alzheimer's are three times lower than in the brains of people the same age without dementia. Here is their abstract:

Human neurons are functional over an entire lifetime, yet the mechanisms that preserve function and protect against neurodegeneration during ageing are unknown. Here we show that induction of the repressor element 1-silencing transcription factor (REST; also known as neuron-restrictive silencer factor, NRSF) is a universal feature of normal ageing in human cortical and hippocampal neurons. REST is lost, however, in mild cognitive impairment and Alzheimer’s disease. Chromatin immunoprecipitation with deep sequencing and expression analysis show that REST represses genes that promote cell death and Alzheimer’s disease pathology, and induces the expression of stress response genes. Moreover, REST potently protects neurons from oxidative stress and amyloid β-protein toxicity, and conditional deletion of REST in the mouse brain leads to age-related neurodegeneration. A functional orthologue of REST, Caenorhabditis elegans SPR-4, also protects against oxidative stress and amyloid β-protein toxicity. During normal ageing, REST is induced in part by cell non-autonomous Wnt signalling. However, in Alzheimer’s disease, frontotemporal dementia and dementia with Lewy bodies, REST is lost from the nucleus and appears in autophagosomes together with pathological misfolded proteins. Finally, REST levels during ageing are closely correlated with cognitive preservation and longevity. Thus, the activation state of REST may distinguish neuroprotection from neurodegeneration in the ageing brain.

Fear detection depends on phase of our heartbeats.

Here's a fascinating piece of work:

Cognitions and emotions can be influenced by bodily physiology. Here, we investigated whether the processing of brief fear stimuli is selectively gated by their timing in relation to individual heartbeats. Emotional and neutral faces were presented to human volunteers at cardiac systole, when ejection of blood from the heart causes arterial baroreceptors to signal centrally the strength and timing of each heartbeat, and at diastole, the period between heartbeats when baroreceptors are quiescent. Participants performed behavioral and neuroimaging tasks to determine whether these interoceptive signals influence the detection of emotional stimuli at the threshold of conscious awareness and alter judgments of emotionality of fearful and neutral faces. Our results show that fearful faces were detected more easily and were rated as more intense at systole than at diastole. Correspondingly, amygdala responses were greater to fearful faces presented at systole relative to diastole. These novel findings highlight a major channel by which short-term interoceptive fluctuations enhance perceptual and evaluative processes specifically related to the processing of fear and threat and counter the view that baroreceptor afferent signaling is always inhibitory to sensory perception.

Correlation between prosocial behavior and computer game playing

Here's what seems to me a a slightly counter-intuitive result. Numerous studies have a noted a correlation between playing violent computer games and less prosocial behavior, and studies of games involving cooperation correlate with more prosocial behaviors. Most of these studies have observed behaviors immediately after palying the games. Mengel takes a more neutral approach and simply asks whether there is a correlation between average daily time spent playing any sort of computer game and prosocial behavior assayed with the Prisoner's dilemma game over 10 different periods, with participating students also reporting on their daily computer use. They find the average cooperation rate is positively correlated with the self-reported amount of time participants spend playing computer games. None of the other computer time use variables (including time spent on social media, browsing internet, working etc.) are significantly related to cooperation rates.  (So...either cooperative students are more likely to spend a lot of time on computer games, or computer games enhance cooperative behavior... or... neither of the above.)

What drives collective versus individualistic behaviors?

Talheim et al. offer a strikingly simple explanation for why collective versus individualistic behaviors may arise in a given cultural group. Rather than the usual comparison of Western and Asian cultures as a whole, they look at large-scale psychological differences with China, and find that they correlate with the different behavioral requirements of rice versus wheat agriculture:

Cross-cultural psychologists have mostly contrasted East Asia with the West. However, this study shows that there are major psychological differences within China. We propose that a history of farming rice makes cultures more interdependent, whereas farming wheat makes cultures more independent, and these agricultural legacies continue to affect people in the modern world. We tested 1162 Han Chinese participants in six sites and found that rice-growing southern China is more interdependent and holistic-thinking than the wheat-growing north. To control for confounds like climate, we tested people from neighboring counties along the rice-wheat border and found differences that were just as large. We also find that modernization and pathogen prevalence theories do not fit the data.

From Henrich's description of their methods:

To investigate the individualism and analytical thinking in participants from different agricultural regions in China, Talhelm et al. used three tests. They measured analytical thinking with a series of triads. Participants were given a target object, such as a rabbit, and asked which of two other objects it goes with. Analytic thinkers tend to match on categories, so rabbits and dogs go together. Holistic thinkers tend to match on relationships, so rabbits eat carrots. The authors also measured individualism in two ways. First, they asked participants to draw a sociogram, with labeled circles representing themselves and their friends. In this test, individualism is measured implicitly by how much bigger the “self” circle is relative to the average “friends” circle. Second, they assessed the nepotism (in-group loyalty) of participants by asking them about hypothetical scenarios in which they could reward or punish friends and strangers for helpful or harmful action.

Morality and perception speed

Here is an interesting nugget... We are more likely to see a word flashed for a very brief interval if it has moral valence. Words related to morality can be identified after a 40-millisecond peek, but nonmoral words needed an extra 10 ms of exposure. From Gantman and Bavel:

Highlights

• We examined whether moral concerns shape awareness of ambiguous stimuli.
• Participants saw moral and non-moral words in a lexical decision task.
• Moral and non-moral words were matched on length, and frequency in lexicon.
• Participants correctly identified moral words more frequently than non-moral words.
• This experiments suggest that moral values may shape perceptual awareness.

Abstract

People perceive religious and moral iconography in ambiguous objects, ranging from grilled cheese to bird feces. In the current research, we examined whether moral concerns can shape awareness of perceptually ambiguous stimuli. In three experiments, we presented masked moral and non-moral words around the threshold for conscious awareness as part of a lexical decision task. Participants correctly identified moral words more frequently than non-moral words—a phenomenon we term the moral pop-out effect. The moral pop-out effect was only evident when stimuli were presented at durations that made them perceptually ambiguous, but not when the stimuli were presented too quickly to perceive or slowly enough to easily perceive. The moral pop-out effect was not moderated by exposure to harm and cannot be explained by differences in arousal, valence, or extremity. Although most models of moral psychology assume the initial perception of moral stimuli, our research suggests that moral beliefs and values may shape perceptual awareness.

Sluggish cognitive tempo, a new diagnosis du jour?

The drug companies may be finding a new profit center, having maxed out their ability to push pills on the more than 6 million American children who have received a diagnosis of A.D.H.D. (attention deficit hyperactivity disorder, which in my son’s case was evaluated by a sane pediatric psychiatrist who wisely said “Chill, he’s just acting like a kid.”) The new syndrome, summarized by Schwartz, is called sluggish cognitive tempo and said to be characterized by lethargy, daydreaming and slow mental processing. It is the subject of the entire January issue of The Journal of Abnormal Child Psychology.

Papers have proposed that a recognition of sluggish cognitive tempo could help resolve some longstanding confusion about A.D.H.D., which despite having hyperactivity in its name includes about two million children who are not hyperactive, merely inattentive. Some researchers propose that about half of those children would be better classified as having sluggish cognitive tempo, with perhaps one million additional children, who do not meet A.D.H.D.’s criteria now, having the new disorder, too.

The syndrome is not well defined, and many researchers refuse to discuss it, or their financial interests in the condition’s acceptance.

The description I find most intriguing and plausible is of a syndrome that involves extreme mind wandering, perhaps of a brain that is chronically in the “default” mode (described in a number of MindBlog posts) and unable to (or unwilling or too lazy to) activate the “attentional” or goal oriented, direct experiential focus, task positive network appropriately.  (Think about the teenagers behind fast-food counters completely unable to do simple addition and subtraction!). The best therapy for this syndrome would seem to be cognitive or behavioral (i.e. "SHAPE UP!"), rather than another pill to pop.

Drug treatments of this or other behavioral syndromes such as depression have the risk of diminishing personal agency and responsibility, as Iarovici notes:

We walk a thinning line between diagnosing illness and teaching our youth to view any emotional upset as pathological. We need a greater focus on building resilience in emerging adults. We need more scientific studies — spanning years, not months — on the risks and benefits of maintenance treatment in emerging adults.

Formation of new brain cells can erase old memories

Over the past ten years it has been established that generation of new nerve cells in the dentate gyrus portion of our brains' hippocampus is required for hippocampus dependent learning and memory recall. Akers et al. now show that this neurogenesis may also promote forgetting. So, it would appear that while not enough neurogenesis inhibits learning and enhanced neurogenesis enhances it, the ongoing circuit remodeling caused by higher neurogenesis can also make the memories more laible. Thus, there may be a compromise “trade-off” level of neurogenesis that allows good performance for both memory acquisition and retention. The abstract:

Throughout life, new neurons are continuously added to the dentate gyrus. As this continuous addition remodels hippocampal circuits, computational models predict that neurogenesis leads to degradation or forgetting of established memories. Consistent with this, increasing neurogenesis after the formation of a memory was sufficient to induce forgetting in adult mice. By contrast, during infancy, when hippocampal neurogenesis levels are high and freshly generated memories tend to be rapidly forgotten (infantile amnesia), decreasing neurogenesis after memory formation mitigated forgetting. In precocial species, including guinea pigs and degus, most granule cells are generated prenatally. Consistent with reduced levels of postnatal hippocampal neurogenesis, infant guinea pigs and degus did not exhibit forgetting. However, increasing neurogenesis after memory formation induced infantile amnesia in these species.

Nonconscious emotions and first impressions - role for conscious awareness

I just came across this interesting article from Davidson and collaborators at Wisconsin:

Emotions can color people’s attitudes toward unrelated objects in the environment. Existing evidence suggests that such emotional coloring is particularly strong when emotion-triggering information escapes conscious awareness. But is emotional reactivity stronger after nonconscious emotional provocation than after conscious emotional provocation, or does conscious processing specifically change the association between emotional reactivity and evaluations of unrelated objects? In this study, we independently indexed emotional reactivity and coloring as a function of emotional-stimulus awareness to disentangle these accounts. Specifically, we recorded skin-conductance responses to spiders and fearful faces, along with subsequent preferences for novel neutral faces during visually aware and unaware states. Fearful faces increased skin-conductance responses comparably in both stimulus-aware and stimulus-unaware conditions. Yet only when visual awareness was precluded did skin-conductance responses to fearful faces predict decreased likability of neutral faces. These findings suggest a regulatory role for conscious awareness in breaking otherwise automatic associations between physiological reactivity and evaluative emotional responses.

Language universals at birth.

Fascinating observations from Gómez et al. showing that human babies are born with linguistic biases concerning syllable structure:

The evolution of human languages is driven both by primitive biases present in the human sensorimotor systems and by cultural transmission among speakers. However, whether the design of the language faculty is further shaped by linguistic biological biases remains controversial. To address this question, we used near-infrared spectroscopy to examine whether the brain activity of neonates is sensitive to a putatively universal phonological constraint. Across languages, syllables like blif are preferred to both lbif and bdif. Newborn infants (2–5 d old) listening to these three types of syllables displayed distinct hemodynamic responses in temporal-perisylvian areas of their left hemisphere. Moreover, the oxyhemoglobin concentration changes elicited by a syllable type mirrored both the degree of its preference across languages and behavioral linguistic preferences documented experimentally in adulthood. These findings suggest that humans possess early, experience-independent, linguistic biases concerning syllable structure that shape language perception and acquisition.

GABA predicts time perception.

Individuals can vary widely in their ability to detect sub-second visual stimuli, and most cognitive training and exercise regimes have exercises designed to enhance detection of shorter (50-200 millisecond) intervals. Terhune et al. make the interesting observation that this variability correlates with the resting state levels of the inhibitory transmitter GABA (gamma-amino butyric acid)in our visual cortex, such that elevated GABA is associated with underestimating the duration of subsecond visual intervals:

Our perception of time constrains our experience of the world and exerts a pivotal influence over a myriad array of cognitive and motor functions. There is emerging evidence that the perceived duration of subsecond intervals is driven by sensory-specific neural activity in human and nonhuman animals, but the mechanisms underlying individual differences in time perception remain elusive. We tested the hypothesis that elevated visual cortex GABA impairs the coding of particular visual stimuli, resulting in a dampening of visual processing and concomitant positive time-order error (relative underestimation) in the perceived duration of subsecond visual intervals. Participants completed psychophysical tasks measuring visual interval discrimination and temporal reproduction and we measured in vivo resting state GABA in visual cortex using magnetic resonance spectroscopy. Time-order error selectively correlated with GABA concentrations in visual cortex, with elevated GABA associated with a rightward horizontal shift in psychometric functions, reflecting a positive time-order error (relative underestimation). These results demonstrate anatomical, neurochemical, and task specificity and suggest that visual cortex GABA contributes to individual differences in time perception.

More on the rejuvenating power of young blood...

Since my "fountain of youth" post in 2011 there has been a burst of research showing that factors in the blood of younger animals can actually reverse the aging process in older ones. Carl Zimmer points to several of the studies. Wagers and collaborators find that restoring levels of a circulating protein growth differentiation factor 11 (GDF11), a skeletal muscle rejuvenating factor whose levels normally decline with age, reverses muscle dysfunction by increased stength and endurance exercise capacity. Further, GDF11 alone can improve the cerebral vasculature and enhance neurogenesis. Villeda et al find that structural and cognitive enhancements elicited by exposure to young blood are mediated, in part, by activation of the cyclic AMP response element binding protein (Creb) in the aged hippocampus.

So, should we all be rushing out to shoot ourselves up with injections of GDF!!? Maybe not... waking up too many stem cells to start multiplying might increase the incidence of cancer.