Friday, January 30, 2015

Parallel brain systems regulate our pain.

Our subjective sensory experiences are regulated by defined brain areas subh visual cortex, auditory cortex,somatosensory cortex, etc., but there doesn't appear to be a "pain cortex" that directly codes our subjective perception of pain. Mano and Seymour, in a review of Woo et al., note the emerging concept that pain might emerge from the coordinated activity of an integrated brain network. Woo et al. provide evidence that distinct brain networks support the subjective changes in pain that result from nociceptive input and self-directed cognitive modulation. Their abstract, followed by a summary graphic from Mano and Seymour:
Cognitive self-regulation can strongly modulate pain and emotion. However, it is unclear whether self-regulation primarily influences primary nociceptive and affective processes or evaluative ones. In this study, participants engaged in self-regulation to increase or decrease pain while experiencing multiple levels of painful heat during functional magnetic resonance imaging (fMRI) imaging. Both heat intensity and self-regulation strongly influenced reported pain, but they did so via two distinct brain pathways. The effects of stimulus intensity were mediated by the neurologic pain signature (NPS), an a priori distributed brain network shown to predict physical pain with over 90% sensitivity and specificity across four studies. Self-regulation did not influence NPS responses; instead, its effects were mediated through functional connections between the nucleus accumbens and ventromedial prefrontal cortex. This pathway was unresponsive to noxious input, and has been broadly implicated in valuation, emotional appraisal, and functional outcomes in pain and other types of affective processes. These findings provide evidence that pain reports are associated with two dissociable functional systems: nociceptive/affective aspects mediated by the NPS, and evaluative/functional aspects mediated by a fronto-striatal system.

Distinct component to the subjective perception of pain. Core nociceptive nodes comprise a multivariate pattern (the neurological pain signature [NPS]), and fronto-striatal brain regions comprise an evaluative pathway sensitive to self-directed cognitive modulation.

Thursday, January 29, 2015

Power and your voice.

Margaret Thatcher did it, and so can you. She went through voice training that permitted her to exude a more authoritative powerful persona. Her voice became higher in pitch and loudness variability but lower in pitch variability, like playing a piano with a smaller number of notes, but varying their volume more. Ko et al. report a similar transformation in the usual cadre of college undergraduates recruited for an experiment. Here is a description of the experiments provided by an APS summary:
In the first experiment, they recorded 161 college students reading a passage aloud; this first recording captured baseline acoustics. The participants were then randomly assigned them to play a specific role in an ensuing negotiation exercise.
Students assigned to a “high” rank were told to go into the negotiation imagining that they either had a strong alternative offer, valuable inside information, or high status in the workplace, or they were asked to recall an experience in which they had power before the negotiation started. Low-rank students, on the other hand, were told to imagine they had either a weak offer, no inside information, or low workplace status, or they were asked to recall an experience in which they lacked power.
The students then read a second passage aloud, as if they were leading off negotiations with their imaginary adversary, and their voices were recorded. Everyone read the same opening, allowing the researchers to examine acoustics while holding the speech content constant across all participants.
Comparing the first and second recordings, the researchers found that the voices of students assigned to high-power roles tended to go up in pitch, become more monotone (less variable in pitch), and become more variable in loudness than the voices of students assigned low-power roles.
And the students’ vocal cues didn’t go unnoticed. A second experiment with a separate group of college students revealed that listeners, who had no knowledge of the first experiment, were able to pick up on these power-related vocal cues to determine who did and did not have power: Listeners ranked speakers who had been assigned to the high-rank group as more likely to engage in high-power behaviors, and they were able to categorize whether a speaker had high or low rank with considerable accuracy.
In line with the vocal changes observed in the first experiments, listeners tended to associate higher pitch and voices that varied in loudness with high-power behaviors. They also associated louder voices with higher power.

Wednesday, January 28, 2015

Musical training accelerates cortical thickness maturation.

Hudziak et al. have examined a database of MRI scans of 232 youths ranging from 6 to 18 years of age, obtained over a period of years. Their analysis revealed that music training was associated with an increased rate of cortical thickness maturation.  Clips from their discussion and a figure:
Music training was associated with the rate of cortical thickness maturation in a number of brain areas distributed throughout the right premotor and primary cortices, the left primary and supplementary motor cortices, bilateral parietal cortices, bilateral orbitofrontal cortices, as well as bilateral parahippocampal gyri. Our finding that music training was associated with cortical thickness development in the premotor and primary motor cortices is not surprising, given that both regions contribute to the control and execution of movement.
Music training was also found to influence cortical thickness maturation within aspects of the DLPFC. Myriad imaging and neuropsychological studies have implicated the DLPFC in aspects of executive functioning, including working memory, attentional control, as well as organization and planning for the future. Interestingly, developmental structural neuroimaging studies have shown that participants with quantitatively higher scores on attention problems exhibit delayed cortical thickness maturation in portions of the DLPFC as well as other cortical regions.

Brain areas where local cortical thickness is associated with the “Age × Years of Playing” interaction (N = 232; 334 time points)

Tuesday, January 27, 2015

Judging and adapting to norm violations engage different brain regions.

Gu et al. find that our insula is critical for learning to adapt when reality deviates from norm expectations, and the ventromedial prefrontal cortex is important for valuation of fairness during social exchange.
Social norms and their enforcement are fundamental to human societies. The ability to detect deviations from norms and to adapt to norms in a changing environment is therefore important to individuals' normal social functioning. Previous neuroimaging studies have highlighted the involvement of the insular and ventromedial prefrontal (vmPFC) cortices in representing norms. However, the necessity and dissociability of their involvement remain unclear. Using model-based computational modeling and neuropsychological lesion approaches, we examined the contributions of the insula and vmPFC to norm adaptation in seven human patients with focal insula lesions and six patients with focal vmPFC lesions, in comparison with forty neurologically intact controls and six brain-damaged controls. There were three computational signals of interest as participants played a fairness game (ultimatum game): sensitivity to the fairness of offers, sensitivity to deviations from expected norms, and the speed at which people adapt to norms. Significant group differences were assessed using bootstrapping methods. Patients with insula lesions displayed abnormally low adaptation speed to norms, yet detected norm violations with greater sensitivity than controls. Patients with vmPFC lesions did not have such abnormalities, but displayed reduced sensitivity to fairness and were more likely to accept the most unfair offers. These findings provide compelling computational and lesion evidence supporting the necessary, yet dissociable roles of the insula and vmPFC in norm adaptation in humans: the insula is critical for learning to adapt when reality deviates from norm expectations, and that the vmPFC is important for valuation of fairness during social exchange.

Monday, January 26, 2015

Subjective status shapes political preferences.

Brown-Iannuzzi et al. suggest that people's subjective perception of their socioeconomic status (SES) has a large influence on whether they support wealth redistribution as a remedy for increasing economic inequality in America. This is distinct from attitudes based on economic ideologies and economic self-interest. Here is their abstract, followed by their description of their studies:
Economic inequality in America is at historically high levels. Although most Americans indicate that they would prefer greater equality, redistributive policies aimed at reducing inequality are frequently unpopular. Traditional accounts posit that attitudes toward redistribution are driven by economic self-interest or ideological principles. From a social psychological perspective, however, we expected that subjective comparisons with other people may be a more relevant basis for self-interest than is material wealth. We hypothesized that participants would support redistribution more when they felt low than when they felt high in subjective status, even when actual resources and self-interest were held constant. Moreover, we predicted that people would legitimize these shifts in policy attitudes by appealing selectively to ideological principles concerning fairness. In four studies, we found correlational (Study 1) and experimental (Studies 2–4) evidence that subjective status motivates shifts in support for redistributive policies along with the ideological principles that justify them.
In Study 1, we measured subjective and objective SES and predicted that higher subjective SES would be associated with greater opposition to redistributive policies, independently of objective SES. In Study 2, we manipulated subjective SES, hypothesizing that participants induced to feel high status would be less supportive of redistribution and would endorse a more conservative ideology to justify that position than would participants induced to feel low status. In Study 3, we gained greater experimental control by creating an economic game in which players earned money and a portion of the profits of high earners were redistributed to low earners. We manipulated how well participants performed relative to other players, and we predicted that players who performed better would support less redistribution and would justify their preferences on the basis of ideological principles. In Study 4, we sought to replicate this finding and investigated whether the manipulation of subjective status led high-status participants to perceive other participants who disagreed with them as biased by self-interest. Together, these studies investigated whether subjective status may lead to political division.
[The results provide evidence] that perceptions of relative status can cause changes in political preferences. In Study 1, feeling higher in relative status was associated with lower support for redistribution. In Study 2, feeling higher in status caused reduced support for redistribution. In Study 3, we manipulated relative status in the context of an economic game and obtained similar results. Although participants could not profit from their recommendations, they recommended rule changes to reduce redistribution when they believed they had outperformed most other players. These changes were accompanied by shifts in construals of what counts as fair. Study 4 replicated these effects and showed that participants’ status affected their perceptions of bias in another player. High-status participants thought a player who recommended increased redistribution was more biased by self-interest than a player who recommended cutting redistribution. Together, these results suggest that subjective feelings of status can drive opinions toward redistribution, along with ideological views that justify those positions. An implication of the present work is that growing subjective perceptions of class differences may drive increased political polarization.

Friday, January 23, 2015

We can see in the infrared!

The major part of my professional life was spent doing research on how the rod cells in our retinas change light into a nerve signal. (I just got a request from ResearchGate, a site on which scientists list their work, suggesting that I upload another of my old vision articles, in this case one that appeared in Nature - in 1965 - 50 years ago! - titled "Reaction of the Rhodopsin Chromophore with Sodium Borohydride".) Even though for the past 20 years or so I have focused on the topics covered by MindBlog I occasionally see a vision article that takes me back to 'the old days'. A colleague from those days (Krzysztof Palczewski) and collaborators have recently done a nice piece of work demonstrating that we can actually expand our vision beyond the normal "visible" range of 400 (blue) to 720 (red) nanometer (nm) wavelengths into the higher frequency (lower energy) infrared regions emitted by infrared lasers. It turns out that the Rhodopsin Chromophore of my article above, retinal, which normally has its shape changed (isomerized) by absorbing one photon of visible light, can be activated by a two-photon chromophore isomerization, especially at wavelengths above 900 nm. From their significance and abstract statements:
This study resolves a long-standing question about the ability of humans to perceive near infrared radiation (IR) and identifies a mechanism driving human IR vision. A few previous reports and our expanded psychophysical studies here reveal that humans can detect IR at wavelengths longer than 1,000 nm and perceive it as visible light, a finding that has not received a satisfactory physical explanation. We show that IR light activates photoreceptors through a nonlinear optical process.
Vision relies on photoactivation of visual pigments in rod and cone photoreceptor cells of the retina. The human eye structure and the absorption spectra of pigments limit our visual perception of light. Our visual perception is most responsive to stimulating light in the 400- to 720-nm (visible) range. First, we demonstrate by psychophysical experiments that humans can perceive infrared laser emission as visible light. Moreover, we show that mammalian photoreceptors can be directly activated by near infrared light with a sensitivity that paradoxically increases at wavelengths above 900 nm, and display quadratic dependence on laser power, indicating a nonlinear optical process. Biochemical experiments with rhodopsin, cone visual pigments, and a chromophore model compound 11-cis-retinyl-propylamine Schiff base demonstrate the direct isomerization of visual chromophore by a two-photon chromophore isomerization. Indeed, quantum mechanics modeling indicates the feasibility of this mechanism. Together, these findings clearly show that human visual perception of near infrared light occurs by two-photon isomerization of visual pigments.

Thursday, January 22, 2015

Steven Pinker's "Sense of Style"

I've just read through Steven Pinker's new book "The Sense of Style: The Thinking Person's Guide to Writing in the 21st Century." It is a lucid exposition, and I wish that I were disciplined enough to heed its exhortations on substance and clarity. I can't resist passing on the following clips from Chapter 2, the second paragraph in particular grabs me.:
Writing is an unnatural act. As Charles Darwin observed, “Man has an instinctive tendency to speak, as we see in the babble of our young children, whereas no child has an instinctive tendency to bake, brew, or write.” The spoken word is older than our species, and the instinct for language allows children to engage in articulate conversation years before they enter a schoolhouse. But the written word is a recent invention that has left no trace in our genome and must be laboriously acquired throughout childhood and beyond.
At the time that we write, the reader exists only in our imaginations. Writing is above all an act of pretense. We have to visualize ourselves in some kind of conversation, or correspondence, or oration, or soliloquy, and put words into the mouth of the little avatar who represents us in this simulated world. The key to good style, far more than obeying any list of commandments , is to have a clear conception of the make-believe world in which you’re pretending to communicate.
Which simulation should a writer immerse himself in when composing a piece for a more generic readership, such as an essay, an article, a review, an editorial, a newsletter, or a blog post? The literary scholars Francis-Noël Thomas and Mark Turner have singled out one model of prose as an aspiration for such writers today. They call it classic style, and explain it in a wonderful little book called Clear and Simple as the Truth.
The guiding metaphor of classic style is seeing the world. The writer can see something that the reader has not yet noticed, and he orients the reader’s gaze so that she can see it for herself. The purpose of writing is presentation, and its motive is disinterested truth. It succeeds when it aligns language with the truth, the proof of success being clarity and simplicity. The truth can be known, and is not the same as the language that reveals it; prose is a window onto the world. The writer knows the truth before putting it into words; he is not using the occasion of writing to sort out what he thinks. Nor does the writer of classic prose have to argue for the truth; he just needs to present it. That is because the reader is competent and can recognize the truth when she sees it, as long as she is given an unobstructed view. The writer and the reader are equals, and the process of directing the reader’s gaze takes the form of a conversation.

Wednesday, January 21, 2015

The signature of consciousness in resting-state brain activity.

I've done a number of posts on attentional or salience versus default mode long-range connectivity networks in our brains (for a review see my lecture.) They correspond roughly to supporting outward task oriented processes versus inward processes such as daydreaming or imagining. Activity in these networks is thought to be a marker of consciousness, but this idea conflicts with observations that long-range functional connectivities persist even after loss of consciousness caused by anesthesia, or in vegetative state patients. This post is to point to recent work by Dehaene and collaborators showing clear difference in the behavior of long-range networks in awake and anesthetized monkeys. Their abstract and statement of significance, followed by a movie showing whole brain connectivity patterns at different time points in the awake monkey.
What are the origins of resting-state functional connectivity patterns? One dominating view is that they index ongoing cognitive processes. However, this conclusion is in conflict with studies showing that long-range functional connectivity persists after loss of consciousness, possibly reflecting structural connectivity maps. In this work we respond to this question showing that in fact both sources have a clear and separable contribution to resting-state patterns. We show that under anesthesia, the dominating functional configurations have low information capacity and lack negative correlations. Importantly, they are rigid, tied to the anatomical map. Conversely, wakefulness is characterized by the dynamical exploration of a rich, flexible repertoire of functional configurations. These dynamical properties constitute a signature of consciousness.
At rest, the brain is traversed by spontaneous functional connectivity patterns. Two hypotheses have been proposed for their origins: they may reflect a continuous stream of ongoing cognitive processes as well as random fluctuations shaped by a fixed anatomical connectivity matrix. Here we show that both sources contribute to the shaping of resting-state networks, yet with distinct contributions during consciousness and anesthesia. We measured dynamical functional connectivity with functional MRI during the resting state in awake and anesthetized monkeys. Under anesthesia, the more frequent functional connectivity patterns inherit the structure of anatomical connectivity, exhibit fewer small-world properties, and lack negative correlations. Conversely, wakefulness is characterized by the sequential exploration of a richer repertoire of functional configurations, often dissimilar to anatomical structure, and comprising positive and negative correlations among brain regions. These results reconcile theories of consciousness with observations of long-range correlation in the anesthetized brain and show that a rich functional dynamics might constitute a signature of consciousness, with potential clinical implications for the detection of awareness in anesthesia and brain-lesioned patients.
Dynamical connectivity matrix - red lines mark positive correlations, and blue lines mark negative correlations.

Tuesday, January 20, 2015

Body movements shape brain representation of musical rhythms.

Entraining our movement to music is a universal human behavior. The enhancement of social cohesion by group movements in synchrony with the rhythms of chants and songs could have had an adaptive value in human evolution. Chemin et al. have done the interesting experiment of recording EEG evoked potentials caused by study participants listening to an ambiguous rhythm, before and after a body-movement session designed to disambiguate the perception of this rhythm by favoring a specific meter (e.g., two beats per measure vs. three beats per measure). They found that the brain responses to the rhythm after body movement were significantly enhanced at frequencies related to the meter to which the participants had moved. Here is their abstract:
It is increasingly recognized that motor routines dynamically shape the processing of sensory inflow (e.g., when hand movements are used to feel a texture or identify an object). In the present research, we captured the shaping of auditory perception by movement in humans by taking advantage of a specific context: music. Participants listened to a repeated rhythmical sequence before and after moving their bodies to this rhythm in a specific meter. We found that the brain responses to the rhythm (as recorded with electroencephalography) after body movement were significantly enhanced at frequencies related to the meter to which the participants had moved. These results provide evidence that body movement can selectively shape the subsequent internal representation of auditory rhythms.

Monday, January 19, 2015

An Example of Publication Bias - Cognitive Advantage in Bilingualism

MindBlog has done several posts on experiments that reinforce what has become the conventional wisdom regarding bilingualism: that it enhances our executive control faculties. De Bruin et al., noting that they themselves had chosen to report positive results supporting this conclusion, but had not followed through on negative data (the file drawer effect), thought to do a systematic analysis of the publication fate of experiments with positive, mixed, or negative outcomes. They searched for conference abstracts on bilingualism and executive control in 169 conferences (31 different national and international meetings) organized between 1999 and 2012, and identified 128 abstracts (presented at 52 different conferences) that focused on bilingualism and executive control. Their result:
Sixty-eight percent of the studies that clearly found a bilingual advantage were published, compared with 50% of the studies that found mixed results supporting the bilingual-advantage theories, 39% of the studies that found mixed results partly challenging those theories, and 29% of the studies that found no differences between monolinguals and bilinguals or found a bilingual disadvantage. On the whole, 63% of the studies supporting the bilingual advantage were published, compared with only 36% of the studies that challenged it.
From the authors discussion:
This difference in publication percentage based on the outcomes of the study could be the result of a bias during several steps of the publication process: Authors, reviewers, and editors can decide to submit or accept only studies that showed positive results. In the first step of the publication process, the file-drawer problem could play an important role in the observed publication bias. Authors could decide not to publish studies with null or mixed results, or they could choose to submit their results only partially, for example, by leaving out tasks that did not show an effect of bilingualism. The article by Treccani et al. (2009)[Treccani is a co-author of the current paper] is an example of the file-drawer problem, as it excluded the experiments that did not show an effect of bilingualism.
On the next level, reviewers and editors might reject manuscripts reporting null, negative, or mixed results more often than manuscripts reporting positive effects. This rejection is often based on the argument that null effects are difficult to interpret, or the result of poor stimulus design... Mahoney (1977) asked journal reviewers to referee manuscripts reporting positive, negative, mixed, or null results with identical methodological procedures. Although the methodology was the same, reviewers scored the manuscripts reporting positive results as methodologically better than the manuscripts reporting negative or mixed results. For manuscripts with positive results, reviewers usually recommended acceptance with moderate revisions. For manuscripts with negative results, however, their usual recommendation was major revision or rejection. Manuscripts with mixed results were mostly rejected.

Friday, January 16, 2015

Watching brain oscillations drive perception.

Are the electrical oscillations observed in EEG recordings as we perceive images simply correlations, reflecting brain processes driving our visual experience, or are the oscillations themselves causal, driving the visual experience? Helfrich et al. address this basic question in a clever experiment in which they force brain oscillations of the left and right visual hemispheres into synchrony using transcranial alternating current stimulation. This causes human subjects to more often perceive an ambiguous figure in one of its perceptual instantiations, showing that the oscillations are driving the visual experience, not vice versa. Their summary:
Brain activity is profoundly rhythmic and exhibits seemingly random fluctuations across a very broad frequency range (less than 0.1 Hz to greater than 600 Hz). Recently, it has become evident that these brain rhythms are not just a generic sign of the brain-at-work, but actually reflect a highly flexible mechanism for information encoding and transfer. In particular, it has been suggested that oscillatory synchronization between different areas of the cortex underlies the establishment of task-relevant networks. Here, we investigated whether gamma-band synchronization (~40 Hz) is causally involved in the integration between the two brain hemispheres of alternating visual tokens into a coherent motion percept. We utilized transcranial alternating current stimulation (tACS), a novel non-invasive brain stimulation technique, which allows frequency-specific entrainment of cortical areas. In a combined tACS-electroencephalography study, we selectively up- and down-regulated interhemispheric coherence, resulting in a directed bias in apparent motion perception: Increased interhemispheric connectivity sustained the horizontal motion percept, while decreased connectivity reinforced the vertical percept. Thus, our data suggest that the level of interhemispheric gamma-band coherence directly influenced the instantaneous motion percept. From these results, we conclude that synchronized neuronal activity is essential for conscious perception and cognition.

Thursday, January 15, 2015

Perceived control promotes persistence and influences brain response to setbacks

From Bhanji et al:

•We report two distinct neural mechanisms for persistence through adversity 
•Perceiving control over setbacks increases persistence 
•Striatum activity relates to persisting after setbacks by correcting mistakes 
•Ventromedial prefrontal activity mediates effects of negative affect on persistence
How do people cope with setbacks and persist with their goals? We examine how perceiving control over setbacks alters neural processing in ways that increase persistence through adversity. For example, a student might retake a class if initial failure was due to controllable factors (e.g., studying) but give up if failure was uncontrollable (e.g., unfair exam questions). Participants persisted more when they perceived control over setbacks, and when they experienced increased negative affect to setbacks. Consistent with previous observations involving negative outcomes, ventral striatum and ventromedial prefrontal (VMPFC) activity was decreased in response to setbacks. Critically, these structures represented distinct neural mechanisms for persistence through adversity. Ventral striatum signal change to controllable setbacks correlated with greater persistence, whereas VMPFC signal change to uncontrollable setbacks mediated the relationship between increased negative affect and persistence. Taken together, the findings highlight how people process setbacks and adapt their behavior for future goal pursuit.
From Whalen and Kelly's review :
The vmPFC is necessary for regulating our emotional the present study, the negative affect change is the catalyst that kicks vmPFC into a higher gear and effects adaptive change (i.e., persistence)...when negative affect accompanies uncontrollable setbacks, as is often the case, the vmPFC activity is necessary to adapt to the emotional reaction and, in so doing, preserve persistence.
The ventral striatum on the other hand is important for signaling prediction errors when behavioral outcomes do not match our expectations...when we believe we have control over situations, the ventral striatum can use value signals to motivate future behavior...this striatal effect is problem focused compared to the prefrontal effect that is more emotion focused.
A fetching point about Paul Whalen's and William Kelley's review is that it starts with the example of two professors currently employed at Dartmouth College.
One applied, and he was hired on his very first try (we’ll call him Bill in this example). Imagine that the other; well, he needed more chances before his eventual hire (we’ll call him P.W. to protect his identity). What dictates whether someone will persist when they encounter a setback? Is it the person who remains calm in the moment, not letting this single event rattle her? Or is it the person who reacts strongly to defeat and heavily reinvests in the project, determined to change things the next time? To borrow from Shakespeare, tell us where is persistence bred, or in the heart, or in the head (The Merchant of Venice, 3.2)? ...Bhanji and Delgado (2014) provide clear evidence of the latter.
Guess who Bill and P.W. actually are!

Wednesday, January 14, 2015

Another magic anti-aging compound?

Riluzole is a drug used to treat amyotrophic lateral sclerosis, also studied for use in mood and anxiety disorders, depression and obsessive-compulsive disorder. It also can have some nasty side effects (nausea,weakness, decreased lung function).
Pereira et al. now show that it has a dramatic effect in preventing cognitive decline in aged rats:
The dementia of Alzheimer’s disease (AD) results primarily from degeneration of neurons that furnish glutamatergic corticocortical connections that subserve cognition. Although neuron death is minimal in the absence of AD, age-related cognitive decline does occur in animals as well as humans, and it decreases quality of life for elderly people. Age-related cognitive decline has been linked to synapse loss and/or alterations of synaptic proteins that impair function in regions such as the hippocampus and prefrontal cortex. These synaptic alterations are likely reversible, such that maintenance of synaptic health in the face of aging is a critically important therapeutic goal. Here, we show that riluzole can protect against some of the synaptic alterations in hippocampus that are linked to age-related memory loss in rats. Riluzole increases glutamate uptake through glial transporters and is thought to decrease glutamate spillover to extrasynaptic NMDA receptors while increasing synaptic glutamatergic activity. Treated aged rats were protected against age-related cognitive decline displayed in nontreated aged animals. Memory performance correlated with density of thin spines on apical dendrites in CA1, although not with mushroom spines. Furthermore, riluzole-treated rats had an increase in clustering of thin spines that correlated with memory performance and was specific to the apical, but not the basilar, dendrites of CA1. Clustering of synaptic inputs is thought to allow nonlinear summation of synaptic strength. These findings further elucidate neuroplastic changes in glutamatergic circuits with aging and advance therapeutic development to prevent and treat age-related cognitive decline.

Tuesday, January 13, 2015

Human children conform to peers' behavior, but apes do not.

Haun and collaborators make the interesting observation that two year old human children will change a learned problem solving strategy on observing peers performing an alternative strategy; apes do not show this behavior.
All primates learn things from conspecifics socially, but it is not clear whether they conform to the behavior of these conspecifics—if conformity is defined as overriding individually acquired behavioral tendencies in order to copy peers’ behavior. In the current study, chimpanzees, orangutans, and 2-year-old human children individually acquired a problem-solving strategy. They then watched several conspecific peers demonstrate an alternative strategy. The children switched to this new, socially demonstrated strategy in roughly half of all instances, whereas the other two great-ape species almost never adjusted their behavior to the majority’s. In a follow-up study, children switched much more when the peer demonstrators were still present than when they were absent, which suggests that their conformity arose at least in part from social motivations. These results demonstrate an important difference between the social learning of humans and great apes, a difference that might help to account for differences in human and nonhuman cultures.

Monday, January 12, 2015

Personality and Ideology

I've done a number of posts (for example, here) pointing to work suggesting that differences in basic partially inherited neurocognitive traits (such as flexibility and openness versus caution and rule following) might underlie liberal versus conservative personalities. Malka et al. have done a cross national test, analyzing responses from more than 70,000 people from 51 countries to ask how a conservative personality style actually relates to cultural and economic attitudes. From their review of the work:
...we found that people with a conservative personality did indeed tend to adopt culturally conservative attitudes on matters like abortion, homosexuality and immigration. On this count, the rigidity of the right model seems to be valid.
But when it came to economic matters related to social welfare policy and economic intervention — the central feature of the left-right divide in much of the world — the results were far different. People with a conservative personality tended to lean slightly to the left...a conservative personality might actually pull people in two directions with respect to their economic attitudes. Prioritizing order and stability will lead to a yearning for the security that left-wing economic policies aim to provide.
This left leaning tendency can be extinguished, however, among people who are highly attentive to politics in countries in which left-right conflict is prominent, by political messaging that binds together right wing cultural and economic views under a broad "conservative" banner. This has nothing to do with psychological predispositions, and suggests that changing the packaging or messaging could change behaviors.

Friday, January 09, 2015

Subliminal Strengthening

Levy et al. make the interesting observation that presenting subliminal positive age stereotypes to older people has a greater effect than similar explicit interventions:
Negative age stereotypes that older individuals assimilate from their culture predict detrimental outcomes, including worse physical function. We examined, for the first time, whether positive age stereotypes, presented subliminally across multiple sessions in the community, would lead to improved outcomes. Each of 100 older individuals (age = 61–99 years, M = 81) was randomly assigned to an implicit-positive-age-stereotype-intervention group, an explicit-positive-age-stereotype-intervention group, a combined implicit- and explicit-positive-age-stereotype-intervention group, or a control group. Interventions occurred at four 1-week intervals. The implicit intervention strengthened positive age stereotypes, which strengthened positive self-perceptions of aging, which, in turn, improved physical function. The improvement in these outcomes continued for 3 weeks after the last intervention session. Further, negative age stereotypes and negative self-perceptions of aging were weakened. For all outcomes, the implicit intervention’s impact was greater than the explicit intervention’s impact. The physical-function effect of the implicit intervention surpassed a previous study’s 6-month-exercise-intervention’s effect with participants of similar ages. The current study’s findings demonstrate the potential of directing implicit processes toward physical-function enhancement over time.
The study they cite as showing less effect of exercise than subliminal priming used the same standard "Short Physical Performance Battery" to assess changes in physical ability caused by the interventions. This test assesses strength, gait, and balance by examining (a) time to rise from a chair and return to the seated position five times, (b) time to walk 8 feet, and (c) ability to stand with feet together in the side-by-side, semi-tandem, and tandem positions for 10 s. Possible scores range from 0 to 12, with a higher score indicating better physical performance. Older individuals who receive lower scores on this measure have increased risk of disability, nursing-home placement, and mortality.

Thursday, January 08, 2015

Personality and immune system reactivity.

Vedhara et al. have examined the expression of inflammatory genes in 121 people who also took personality tests that rated the generally identified five major dimensions of human personality (Neuroticism, Extraversion, Openness to Experience, Agreeableness, and Conscientiousness). From the author's introduction:
...we hypothesized that pro-inflammatory gene expression would be up-regulated in extraverts and people with high levels of openness to experience (both of whom would be expected to experience elevated risk of injury/infection) and down-regulated in conscientious individuals with comparatively strong behavioural immune responses.
This is in fact what they found. From their discussion:
The present results identified systematic differences in leukocyte gene expression that correlate with individual differences on two major dimensions of human personality: Extraversion and Conscientiousness. Consistent with predictions from behavioural immune response theory, Extraversion was associated with up-regulated expression of pro-inflammatory genes, whereas Conscientiousness was associated with down-regulated expression of pro-inflammatory genes. These effects were independent of major health behavioural factors (BMI, smoking, alcohol consumption, physical activity); independent of variations in leukocyte subset prevalence; independent of negative affect; independent of minor physical symptoms and related medications; and independent of demographic characteristics as well as other major dimensions of human personality. In contrast, none of the major personality dimensions was significantly associated with differential expression of the other primary gene module involved in the CTRA profile – antiviral and antibody-related transcripts. In the context of previous data linking Extraversion and Conscientiousness to health and longevity, the present functional genomics findings may provide new insights into the molecular basis for such relationships.
Their results do not support the model of neuroticism and negative affect generating a 'disease-prone personality.' Numerous other studies have correlated the trait of conscientiousness with longevity.

Wednesday, January 07, 2015

The unforeseen costs of extraordinary experiences.

Daniel Gilbert and his collaborators at Harvard have come up with yet another fascinating nugget on our human behaviors:
People seek extraordinary experiences—from drinking rare wines and taking exotic vacations to jumping from airplanes and shaking hands with celebrities. But are such experiences worth having? We found that participants thoroughly enjoyed having experiences that were superior to those had by their peers, but that having had such experiences spoiled their subsequent social interactions and ultimately left them feeling worse than they would have felt if they had had an ordinary experience instead. Participants were able to predict the benefits of having an extraordinary experience but were unable to predict the costs. These studies suggest that people may pay a surprising price for the experiences they covet most.
A bit from the introduction:
More than 600 people have paid a minimum of $250,000 for a seat on the world’s first commercial spacecraft, soon to be launched by Virgin Galactic. Their journey will last a few hours, but they will talk about it for years to come...Floating weightless for several minutes while gazing down at Earth is an experience that falls somewhere between delightful and dazzling, which is why so many people are willing to pay so much money to have it. The less obvious consequence is that such experiences can make the people who have them strangers to everyone else on earth—and, as a rule, earthlings do not always treat strangers so nicely. At worst, people may be envious and resentful of those who have had an extraordinary experience, and at best, they may find themselves with little to talk about. Indeed, when people interact, they typically discuss the things they have in common and an afternoon in orbit typically is not one of them. Extraordinary experiences are both different from and better than the experiences that most other people have, and being both alien and enviable is an unlikely recipe for popularity.
In one experiment subjects in groups watched a video (17 groups of 4 participants, each watching in their own cubicle - afterwards they were escorted to a room for 5 min of unstructured conversation. One of the participants in each group watched a video that was superior to the video watched by the others. Participants who had watched the superior movie felt more enjoyment just after the film, but felt excluded during a subsequent social interaction, and this left them feeling worse than participants who had had an ordinary experience instead. A second experiment showed that participants correctly predicted that the extraordinary experience would leave them feeling better than the ordinary experience would before the interaction, but failed to realize that it would leave them feeling worse after the interaction. In a final study participants were asked to estimate how the actual participants in Study 1 felt. The result found was that they did not expect the extraordinary experiencer to be excluded from the interaction, and they expected the extraordinary experiencer to feel better—not worse—than the ordinary experiencers.

From the summary:
Pleasures come in two varieties: the social and the nonsocial. A hallmark of the nonsocial pleasures—whether the cool tingle of Dom Pérignon or the hot snarl of a new Maserati—is that people adapt to them quickly, which is why such experiences are typically best when they are novel or rare. The social pleasures have a different appeal. People crave acceptance, belonging, and camaraderie, and the hallmark of these pleasures is that they come more readily to those who fit in than to those who stand out. The two varieties of pleasure give rise to a pair of incompatible desires: to do what other people have not yet done and to be just like everyone else. Satisfying the first of these desires can frustrate the second. When extraordinary experiences separate a person from others, these experiences may ultimately reclaim more joy than they provide.

Tuesday, January 06, 2015


Todd May does a brief essay (coining the world “invulnerabilism”) that is yet another interesting take on an issue central to all our lives: Do what degree is it useful to psychologically armor ourselves from the ‘slings and arrows of outrageous fortune’ - to have a strong psychological immune system, or an emotionally invulnerable self construal? The meditative practices of several traditions offer us a route into our brain’s ‘basement’, a closer approach to and experience of the machinery that generates all the stuff upstairs, our emotionally reactive immersed selves and personas (Buddhism, for example, offering us an end to suffering if we abandon our desires.) May suggests:
..the way to think about these things has less to do with the invulnerability promoted by the official doctrines, and more to do with, one might say, using these doctrines to take the edge off of vulnerability, to allow one to experience life without becoming overwhelmed or depressed or resentful or bitter, except perhaps at the extremity of loss. There is some combination of embedding oneself in the world in a vulnerable way and not being completely undone by that vulnerability that is pointed at, if not directly endorsed, by the official doctrines.
It seems to me that Taoism, Buddhism, Stoicism, etc. work not by making one invulnerable but rather by allowing one to step back from the immediacy of the situation so that the experience of pain or suffering is seen for what it is, precisely as part of a contingent process, a process that could have yielded a very different present but just happened to yield this one.
Another point would be the evolution of our social brain has resulted in a built in bias towards feeling the sort of vulnerability and bonding that sustains and defends social group identity. A group of floating detached Taoists isn't all that useful in intergroup conflicts. Finally, disciplines that result in maintaining emotional distance from others can also let atrophy the evolved neuroendocrine chemistries that can vitalize our physiology and longevity.

Monday, January 05, 2015

Is there a reason for everything? - Teleological reasoning about life events

Banerjee and Bloom  explore the view that the tendency to develop teleological beliefs about life events is a byproduct of certain universal social-cognitive biases, a cognitive byproduct of humans’ natural tendency to view the world in terms of agency, purpose, and design. Their detailed descriptions of the three studies noted in the abstract below (in the journal "Cognition") are difficult to summarize in this brief post, so I pass on just the highlights and abstract. Motivated readers can request a copy of the article from me.

• We examine religious believers’ and non-believers’ belief in purpose in life events. 
• Mentalizing ability predicts the tendency to hold teleological beliefs about events. 
• Adults’ teleological beliefs about life events do not depend upon a belief in God. 
• The perception of purpose in events is rooted in universal social-cognitive biases.
People often believe that significant life events happen for a reason. In three studies, we examined evidence for the view that teleological beliefs reflect a general cognitive bias to view the world in terms of agency, purpose, and design. Consistent with this hypothesis, we found that individual differences in mentalizing ability predicted both the tendency to believe in fate (Study 1) and to infer purposeful causes of one’s own life events (Study 2). In addition, people’s perception of purpose in life events was correlated with their teleological beliefs about nature, but this relationship was driven primarily by individuals’ explicit religious and paranormal beliefs (Study 3). Across all three studies, we found that while people who believe in God hold stronger teleological beliefs than those who do not, there is nonetheless evidence of teleological beliefs among non-believers, confirming that the perception of purpose in life events does not rely on theistic belief. These findings suggest that the tendency to perceive design and purpose in life events—while moderated by theistic belief—is not solely a consequence of culturally transmitted religious ideas. Rather, this teleological bias has its roots in certain more general social propensities.

Friday, January 02, 2015

Biological explanations for psychopathology decrease clinician empathy.

Lebowitz and Ahn find that clinicians become less, not more, empathetic with patients whose mental disorder is known to have a biological basis:
Mental disorders are increasingly understood in terms of biological mechanisms. We examined how such biological explanations of patients’ symptoms would affect mental health clinicians’ empathy—a crucial component of the relationship between treatment-providers and patients—as well as their clinical judgments and recommendations. In a series of studies, US clinicians read descriptions of potential patients whose symptoms were explained using either biological or psychosocial information. Biological explanations have been thought to make patients appear less accountable for their disorders, which could increase clinicians’ empathy. To the contrary, biological explanations evoked significantly less empathy. These results are consistent with other research and theory that has suggested that biological accounts of psychopathology can exacerbate perceptions of patients as abnormal, distinct from the rest of the population, meriting social exclusion, and even less than fully human. Although the ongoing shift toward biomedical conceptualizations has many benefits, our results reveal unintended negative consequences.

Thursday, January 01, 2015

Cerebral coherence between communicators.

Stolk et al. have searched across the whole brain for a cerebral dynamics matching the behavioral dynamics of mutual understanding and note that brain activities in the right temporal lobes of individuals synchronize during communication in a way that reflects conceptualization of a signal's use apart from specific experiences of the signal:
How can we understand each other during communicative interactions? An influential suggestion holds that communicators are primed by each other’s behaviors, with associative mechanisms automatically coordinating the production of communicative signals and the comprehension of their meanings. An alternative suggestion posits that mutual understanding requires shared conceptualizations of a signal’s use, i.e., “conceptual pacts” that are abstracted away from specific experiences. Both accounts predict coherent neural dynamics across communicators, aligned either to the occurrence of a signal or to the dynamics of conceptual pacts. Using coherence spectral-density analysis of cerebral activity simultaneously measured in pairs of communicators, this study shows that establishing mutual understanding of novel signals synchronizes cerebral dynamics across communicators’ right temporal lobes. This interpersonal cerebral coherence occurred only within pairs with a shared communicative history, and at temporal scales independent from signals’ occurrences. These findings favor the notion that meaning emerges from shared conceptualizations of a signal’s use.