Oxytocin promotes group-serving dishonesty

Like Lewis Carroll's Wonderland, the oxytocin story gets curiouser and curiouser.... this from Shalvi and De Dreu:

To protect and promote the well-being of others, humans may bend the truth and behave unethically. Here we link such tendencies to oxytocin, a neuropeptide known to promote affiliation and cooperation with others. Using a simple coin-toss prediction task in which participants could dishonestly report their performance levels to benefit their group’s outcome, we tested the prediction that oxytocin increases group-serving dishonesty. A double-blind, placebo-controlled experiment allowing individuals to lie privately and anonymously to benefit themselves and fellow group members showed that healthy males (n = 60) receiving intranasal oxytocin, rather than placebo, lied more to benefit their group, and did so faster, yet did not necessarily do so because they expected reciprocal dishonesty from fellow group members. Treatment effects emerged when lying had financial consequences and money could be gained; when losses were at stake, individuals in placebo and oxytocin conditions lied to similar degrees. In a control condition (n = 60) in which dishonesty only benefited participants themselves, but not fellow group members, oxytocin did not influence lying. Together, these findings fit a functional perspective on morality revealing dishonesty to be plastic and rooted in evolved neurobiological circuitries, and align with work showing that oxytocin shifts the decision-maker’s focus from self to group interests. These findings highlight the role of bonding and cooperation in shaping dishonesty, providing insight into when and why collaboration turns into corruption.

Aesop's crow - evidence of causal understanding

Jelbert et al. show even further smarts in the New Caledonian Crow I've mentioned in several previous posts.

Understanding causal regularities in the world is a key feature of human cognition. However, the extent to which non-human animals are capable of causal understanding is not well understood. Here, we used the Aesop's fable paradigm – in which subjects drop stones into water to raise the water level and obtain an out of reach reward – to assess New Caledonian crows' causal understanding of water displacement. We found that crows preferentially dropped stones into a water-filled tube instead of a sand-filled tube; they dropped sinking objects rather than floating objects; solid objects rather than hollow objects, and they dropped objects into a tube with a high water level rather than a low one. However, they failed two more challenging tasks which required them to attend to the width of the tube, and to counter-intuitive causal cues in a U-shaped apparatus. Our results indicate that New Caledonian crows possess a sophisticated, but incomplete, understanding of the causal properties of displacement, rivaling that of 5–7 year old children.

A blood test for Alzheimers disease?

Mapstone et al. have identified a set of 10 lipids whose levels predict, with an accuracy of over 90%, whether or not an older individual will develop mild cognitive impairment or Alzheimer's disease within 2–3 years. If this work is confirmed by other independent and more extensive studies, we may be seeing a clinical test within a few years. Would this 72 year old take such a test? Probably so, because avoiding the possible bad news would mean I might be less likely to get financial, legal, personal stuff in order (things like planing for care and informing family.)

Alzheimer's disease causes a progressive dementia that currently affects over 35 million individuals worldwide and is expected to affect 115 million by 2050. There are no cures or disease-modifying therapies, and this may be due to our inability to detect the disease before it has progressed to produce evident memory loss and functional decline. Biomarkers of preclinical disease will be critical to the development of disease-modifying or even preventative therapies. Unfortunately, current biomarkers for early disease, including cerebrospinal fluid tau and amyloid-β levels, structural and functional magnetic resonance imaging and the recent use of brain amyloid imaging or inflammaging, are limited because they are either invasive, time-consuming or expensive. Blood-based biomarkers may be a more attractive option, but none can currently detect preclinical Alzheimer's disease with the required sensitivity and specificity. Herein, we describe our lipidomic approach to detecting preclinical Alzheimer's disease in a group of cognitively normal older adults. We discovered and validated a set of ten lipids from peripheral blood that predicted phenoconversion to either amnestic mild cognitive impairment or Alzheimer's disease within a 2–3 year timeframe with over 90% accuracy. This biomarker panel, reflecting cell membrane integrity, may be sensitive to early neurodegeneration of preclinical Alzheimer's disease.

Wave of the future - trusting machines that talk to us.

We're reading that in 10 years we might be able to buy autonomous cars that do the driving for us. Waytz et al. do an interesting study of the psychological consequence of endowing such vehicles with a voice. They monitor self report of emotions and fluctuations in heart rate while subjects either operate a driving simulator themselves, or become the passenger driven by an autonomous that does or doesn't speak to them. Not surprisingly, audio communication increases the sense of liking and trust. Also in the aftermath of a simulated collision programmed so as to be unavoidable, the vocal vehicle is more likely to be absolved of blame. The subjects have attributed human agency to a machine, which I was just doing while driving back to Madison WI from my winter nest in Fort Lauderdale, and found myself cursing the teutonic female voice of my GPS navigator. Here are their highlights and abstract:

Highlights
-Anthropomorphism of a car predicts trust in that car.
-Trust is reflected in behavioral, physiological, and self-report measures.
-Anthropomorphism also affects attributions of responsibility/punishment.  

Abstract 

Sophisticated technology is increasingly replacing human minds to perform complicated tasks in domains ranging from medicine to education to transportation. We investigated an important theoretical determinant of people's willingness to trust such technology to perform competently—the extent to which a nonhuman agent is anthropomorphized with a humanlike mind—in a domain of practical importance, autonomous driving. Participants using a driving simulator drove either a normal car, an autonomous vehicle able to control steering and speed, or a comparable autonomous vehicle augmented with additional anthropomorphic features—name, gender, and voice. Behavioral, physiological, and self-report measures revealed that participants trusted that the vehicle would perform more competently as it acquired more anthropomorphic features. Technology appears better able to perform its intended design when it seems to have a humanlike mind. These results suggest meaningful consequences of humanizing technology, and also offer insights into the inverse process of objectifying humans.

Brain abnormalities caused by marijuana use.

Numerous studies have shown that cannabis use is associated with impairments of cognitive functions, including learning and memory, attention, and decision-making. Animal studies show structural changes in brain regions underlying these functions after exposure to Δ9-tetrahydrocannabinol (THC). Now, a sobering bit of information on structural changes in human brains from Gilman et al.:

Marijuana is the most commonly used illicit drug in the United States, but little is known about its effects on the human brain, particularly on reward/aversion regions implicated in addiction, such as the nucleus accumbens and amygdala. Animal studies show structural changes in brain regions such as the nucleus accumbens after exposure to Δ9-tetrahydrocannabinol, but less is known about cannabis use and brain morphometry in these regions in humans. We collected high-resolution MRI scans on young adult recreational marijuana users and nonusing controls and conducted three independent analyses of morphometry in these structures: (1) gray matter density using voxel-based morphometry, (2) volume (total brain and regional volumes), and (3) shape (surface morphometry). Gray matter density analyses revealed greater gray matter density in marijuana users than in control participants in the left nucleus accumbens extending to subcallosal cortex, hypothalamus, sublenticular extended amygdala, and left amygdala, even after controlling for age, sex, alcohol use, and cigarette smoking. Trend-level effects were observed for a volume increase in the left nucleus accumbens only. Significant shape differences were detected in the left nucleus accumbens and right amygdala. The left nucleus accumbens showed salient exposure-dependent alterations across all three measures and an altered multimodal relationship across measures in the marijuana group. These data suggest that marijuana exposure, even in young recreational users, is associated with exposure-dependent alterations of the neural matrix of core reward structures and is consistent with animal studies of changes in dendritic arborization.

Brain activity underlying subjective awareness

Hill and He devise and interesting paradigm to distinguish brain activities directly contributing to conscious perception from brain activities that precede or follow it. They do this by examining trial by trial objective performance, subjective awareness, and the confidence level of subjective awareness. They find that widely distributed slow cortical potentials in the < 4 Hz (delta) range - i.e. brain activity waves taking longer than a quarter of a second - correlate with subjective awareness, even after the effects of objective performance and confidence (contributed by more transient brain activity) were both removed. Here is their abstract:

Despite intense recent research, the neural correlates of conscious visual perception remain elusive. The most established paradigm for studying brain mechanisms underlying conscious perception is to keep the physical sensory inputs constant and identify brain activities that correlate with the changing content of conscious awareness. However, such a contrast based on conscious content alone would not only reveal brain activities directly contributing to conscious perception, but also include brain activities that precede or follow it. To address this issue, we devised a paradigm whereby we collected, trial-by-trial, measures of objective performance, subjective awareness, and the confidence level of subjective awareness. Using magnetoencephalography recordings in healthy human volunteers, we dissociated brain activities underlying these different cognitive phenomena. Our results provide strong evidence that widely distributed slow cortical potentials (SCPs) correlate with subjective awareness, even after the effects of objective performance and confidence were both removed. The SCP correlate of conscious perception manifests strongly in its waveform, phase, and power. In contrast, objective performance and confidence were both contributed by relatively transient brain activity. These results shed new light on the brain mechanisms of conscious, unconscious, and metacognitive processing.

Blocking facial muscle movement compromizes detecting and having emotions

Rychlowska et al. show that blocking facial mimicry makes true and false smiles look the same:

Recent research suggests that facial mimicry underlies accurate interpretation of subtle facial expressions. In three experiments, we manipulated mimicry and tested its role in judgments of the genuineness of true and false smiles. A first experiment used facial EMG to show that a new mouthguard technique for blocking mimicry modifies both the amount and the time course of facial reactions. In two further experiments, participants rated true and false smiles either while wearing mouthguards or when allowed to freely mimic the smiles with or without additional distraction, namely holding a squeeze ball or wearing a finger-cuff heart rate monitor. Results showed that blocking mimicry compromised the decoding of true and false smiles such that they were judged as equally genuine. Together the experiments highlight the role of facial mimicry in judging subtle meanings of facial expressions.

And, Richard Friedman points to work showing that paralyzing the facial muscles central to frowning with Botox provides relief from depression. Information between brain and muscle clearly flows both ways.

In a study forthcoming in the Journal of Psychiatric Research, Eric Finzi, a cosmetic dermatologist, and Norman Rosenthal, a professor of psychiatry at Georgetown Medical School, randomly assigned a group of 74 patients with major depression to receive either Botox or saline injections in the forehead muscles whose contraction makes it possible to frown. Six weeks after the injection, 52 percent of the subjects who got Botox showed relief from depression, compared with only 15 percent of those who received the saline placebo.

Is it a Stradivarius?

I've published several posts on studies showing that panels of expert wine tasters can not distinguish cheap from expensive wines if their labels are covered, and note preference for the expensive wines only if they know the prices. Now several studies from the world of music make an equivalent finding with respect to the quality of new versus old violins. From Fritz et al.:

Many researchers have sought explanations for the purported tonal superiority of Old Italian violins by investigating varnish and wood properties, plate tuning systems, and the spectral balance of the radiated sound. Nevertheless, the fundamental premise of tonal superiority has been investigated scientifically only once very recently, and results showed a general preference for new violins and that players were unable to reliably distinguish new violins from old. The study was, however, relatively small in terms of the number of violins tested (six), the time allotted to each player (an hour), and the size of the test space (a hotel room). In this study, 10 renowned soloists each blind-tested six Old Italian violins (including five by Stradivari) and six new during two 75-min sessions—the first in a rehearsal room, the second in a 300-seat concert hall. When asked to choose a violin to replace their own for a hypothetical concert tour, 6 of the 10 soloists chose a new instrument. A single new violin was easily the most-preferred of the 12. On average, soloists rated their favorite new violins more highly than their favorite old for playability, articulation, and projection, and at least equal to old in terms of timbre. Soloists failed to distinguish new from old at better than chance levels. These results confirm and extend those of the earlier study and present a striking challenge to near-canonical beliefs about Old Italian violins.

Top Brain, Bottom Brain - a user's manual from Kosslyn and Miller

I thought I would point to a recent book authored by Kosslyn and Miller:  “Top Brain - Bottom Brain: Surprising Insights into How You Think.” They make a good effort to communicate (co-author Miller is a professional journalist/author), yet it is a tough slog at points.

Their basic simplification is to describe the top and the bottom parts of the brain as performing different sorts of tasks. The bottom-brain system classifies and interprets sensory information from the world, and the top-brain system formulates and executes plans. Here is the standard brain graphic from their introduction:

You can have four separate ways of arranging a set of opposites like top and bottom, and they make these into four personality types distinguished by different relative activities of the two.:

To do a disservice to their more balanced and extended presentation, I cut to the chase with an irreverent condensation:

The movers appear to be your winners, top brain action people who actually also use the bottom half to pay attention to the consequences of their actions and use the feedback.

The stimulator is more the ‘damn the cannons, full speed ahead’ kind of person, less inclined to attend to the consequences of their actions and know when enough is enough.

The Perceivers are mainly bottom brain perceivers and interpreters, but unlikely to initiate top brain detailed or complex plans.

Finally, the people with lazy top and bottom brains are ‘whatever…’ types, absorbed by local events and immediate imperatives, passively responsive to ongoing situations, i.e. the U.S. electorate.

Chapter 13 presents a test for the reader to determine his or her own individual style. They suggest that although you may not always rely on the same mode in every context, peoples' responses to the test indicate that they do operate in a single mode most of the time. You can take the test in the book, or take it online at www.TopBrainBottomBrain.com and have your score computed automatically.

Judging a man by the width of his face.

Valentine et al. make interesting observations in a speed-dating context. The effect of higher facial width-to-height ratio on short-term but not long-term relationships is compatible with the idea that more dominant men who are selected for mating because of their good health and prowess may also more likely to be less faithful and less investing as fathers:

Previous research has shown that men with higher facial width-to-height ratios (fWHRs) have higher testosterone and are more aggressive, more powerful, and more financially successful. We tested whether they are also more attractive to women in the ecologically valid mating context of speed dating. Men’s fWHR was positively associated with their perceived dominance, likelihood of being chosen for a second date, and attractiveness to women for short-term, but not long-term, relationships. Perceived dominance (by itself and through physical attractiveness) mediated the relationship between fWHR and attractiveness to women for short-term relationships. Furthermore, men’s perceptions of their own dominance showed patterns of association with mating desirability similar to those of fWHR. These results support the idea that fWHR is a physical marker of dominance. This is the first study to show that male dominance and higher fWHRs are attractive to women for short-term relationships in a controlled and interactive situation that could actually lead to mating and dating.

Over the hill at 24

Great....the continuous stream of papers documenting cognitive aging in adults and seniors, many noted in MindBlog, has how lowered the bar even further. Thompson et al. find a slowing of response times in a video game beginning at 24 years of age.

Typically studies of the effects of aging on cognitive-motor performance emphasize changes in elderly populations. Although some research is directly concerned with when age-related decline actually begins, studies are often based on relatively simple reaction time tasks, making it impossible to gauge the impact of experience in compensating for this decline in a real world task. The present study investigates age-related changes in cognitive motor performance through adolescence and adulthood in a complex real world task, the real-time strategy video game StarCraft 2. In this paper we analyze the influence of age on performance using a dataset of 3,305 players, aged 16-44, collected by Thompson, Blair, Chen & Henrey. Using a piecewise regression analysis, we find that age-related slowing of within-game, self-initiated response times begins at 24 years of age. We find no evidence for the common belief expertise should attenuate domain-specific cognitive decline. Domain-specific response time declines appear to persist regardless of skill level. A second analysis of dual-task performance finds no evidence of a corresponding age-related decline. Finally, an exploratory analyses of other age-related differences suggests that older participants may have been compensating for a loss in response speed through the use of game mechanics that reduce cognitive load.

Training emotions - a brief video from The Brain Club

I received an email recently from "The Brain Club" pointing me to the series of brief video presentations they are developing over time. I thought the presentation by Amit Etkin at Stanford Univ. was very effective. I'm including that video in this post. It describes the results of a meta-analysis of many papers that shows that in anxious and depressed individuals the brain's amygdala, insula, and cingulate are over-reactive while the prefrontal cortex is under-reactive. (i.e. the downstairs is over-riding the upstairs of our brains.) Cognitive training exercises available on the web that reinforce a positivity bias and enhance working memory lessen this upstairs/downstairs imbalance, and a brief review by Subramaniam and Vinogradov shows MRI data indicating that it is accompanied by enhancement of medial prefrontal activity.

 

Here is a slightly larger version of the figure from the meta-analysis paper showing the downstair (yellow) and upstairs (blue) regions whose activity changes with training.

A more through summary of cognitive training for impaired neural systems can be found in Vinogradov et al.

Attributing awareness to oneself and others.

Kelley et al. make some fascinating observations. I pass on their statement of the significance of the work and their abstract:

Significance

What is the relationship between your own private awareness of events and the awareness that you intuitively attribute to the people around you? In this study, a region of the human cerebral cortex was active when people attributed sensory awareness to someone else. Furthermore, when that region of cortex was temporarily disrupted, the person’s own sensory awareness was disrupted. The findings suggest a fundamental connection between private awareness and social cognition.

Abstract

This study tested the possible relationship between reported visual awareness (“I see a visual stimulus in front of me”) and the social attribution of awareness to someone else (“That person is aware of an object next to him”). Subjects were tested in two steps. First, in an fMRI experiment, subjects were asked to attribute states of awareness to a cartoon face. Activity associated with this task was found bilaterally within the temporoparietal junction (TPJ) among other areas. Second, the TPJ was transiently disrupted using single-pulse transcranial magnetic stimulation (TMS). When the TMS was targeted to the same cortical sites that had become active during the social attribution task, the subjects showed symptoms of visual neglect in that their detection of visual stimuli was significantly affected. In control trials, when TMS was targeted to nearby cortical sites that had not become active during the social attribution task, no significant effect on visual detection was found. These results suggest that there may be at least some partial overlap in brain mechanisms that participate in the social attribution of sensory awareness to other people and in attributing sensory awareness to oneself.

Poor people judge more harshly.

From Pitesa and Thau:

In the research presented here, we tested the idea that a lack of material resources (e.g., low income) causes people to make harsher moral judgments because a lack of material resources is associated with a lower ability to cope with the effects of others’ harmful behavior. Consistent with this idea, results from a large cross-cultural survey (Study 1) showed that both a chronic (due to low income) and a situational (due to inflation) lack of material resources were associated with harsher moral judgments. The effect of inflation was stronger for low-income individuals, whom inflation renders relatively more vulnerable. In a follow-up experiment (Study 2), we manipulated whether participants perceived themselves as lacking material resources by employing different anchors on the scale they used to report their income. The manipulation led participants in the material-resources-lacking condition to make harsher judgments of harmful, but not of nonharmful, transgressions, and this effect was explained by a sense of vulnerability. Alternative explanations were excluded. These results demonstrate a functional and contextually situated nature of moral psychology.

Memory reactivation in aging versus young brains.

Given my status as a senior aging person I always note the passing article that chronicles yet another way in which the equipment upstairs is losing it. Here is a bit from St-Laurent et al. that shows that the greater difficulty senior people have in recalling past experiences, replaying them, is not in the quality of their initial perceptions, but in fetching them up during recall attempts. (I've thought about preparing a longer written piece or talk on brain changes in aging, drawn mainly from MindBlog posts, but have decided I would rather go for more cheerful topics.)

We investigated how aging affects the neural specificity of mental replay, the act of conjuring up past experiences in one's mind. We used functional magnetic resonance imaging (fMRI) and multivariate pattern analysis to quantify the similarity between brain activity elicited by the perception and memory of complex multimodal stimuli. Young and older human adults viewed and mentally replayed short videos from long-term memory while undergoing fMRI. We identified a wide array of cortical regions involved in visual, auditory, and spatial processing that supported stimulus-specific representation at perception as well as during mental replay. Evidence of age-related dedifferentiation was subtle at perception but more salient during mental replay, and age differences at perception could not account for older adults' reduced neural reactivation specificity. Performance on a post-scan recognition task for video details correlated with neural reactivation in young but not in older adults, indicating that in-scan reactivation benefited post-scan recognition in young adults, but that some older adults may have benefited from alternative rehearsal strategies. Although young adults recalled more details about the video stimuli than older adults on a post-scan recall task, patterns of neural reactivation correlated with post-scan recall in both age groups. These results demonstrate that the mechanisms supporting recall and recollection are linked to accurate neural reactivation in both young and older adults, but that age affects how efficiently these mechanisms can support memory's representational specificity in a way that cannot simply be accounted for by degraded sensory processes.

Enhancing or lowering performance monitoring activity of our brains.

Wow, here is a fascinating observation. Small electrical currents applied to our medial frontal cortex can either enhance or abolish our brains' error detection and feedback adjustment activities:

Adaptive human behavior depends on the capacity to adjust cognitive processing after an error. Here we show that transcranial direct current stimulation of medial–frontal cortex provides causal control over the electrophysiological responses of the human brain to errors and feedback. Using one direction of current flow, we eliminated performance-monitoring activity, reduced behavioral adjustments after an error, and slowed learning. By reversing the current flow in the same subjects, we enhanced performance-monitoring activity, increased behavioral adjustments after an error, and sped learning. These beneficial effects fundamentally improved cognition for nearly 5 h after 20 min of noninvasive stimulation. The stimulation selectively influenced the potentials indexing error and feedback processing without changing potentials indexing mechanisms of perceptual or response processing. Our findings demonstrate that the functioning of mechanisms of cognitive control and learning can be up- or down-regulated using noninvasive stimulation of medial–frontal cortex in the human brain.

Caloric restriction and longevity.

I thought I would pass on this recent open access Nature article by the Univ. of Wisconsin group studying the effects of caloric restriction in Rhesus monkeys, studies meant to be more relevant to us humans that the mouse work showing increased health and longevity caused by dietary restriction. They suggest that a reason that an NIH study found less striking effects was that the controls in the NIH study were also effectively calorically restricted.

Caloric restriction (CR) without malnutrition increases longevity and delays the onset of age-associated disorders in short-lived species, from unicellular organisms to laboratory mice and rats. The value of CR as a tool to understand human ageing relies on translatability of CR’s effects in primates. Here we show that CR significantly improves age-related and all-cause survival in monkeys on a long-term ~30% restricted diet since young adulthood. These data contrast with observations in the 2012 NIA intramural study report, where a difference in survival was not detected between control-fed and CR monkeys. A comparison of body weight of control animals from both studies with each other, and against data collected in a multi-centred relational database of primate ageing, suggests that the NIA control monkeys were effectively undergoing CR. Our data indicate that the benefits of CR on ageing are conserved in primates.

Is consciousness in control? Does it matter?

I want to pass on a clip from SelfAwarePatterns that is as succinct a summary as I have seen (better than the one in my "I-Illusion" lecture) of the largely futile free will debate (the subject of many mindblog posts) that has persisted since Libet's original work showing motor cortex activity associated with a movement starts earlier than awareness of consciously willing that action.

Scenario 1: Consciousness controls actions:

You consciously decide what to do.
You do it.
You have conscious and unconscious knowledge of 2 and how it turned out.
Loop back to step 1.

Scenario 2: Consciousness does not control actions:

You unconsciously decide what to do.
You do it.
You have conscious knowledge (at least sometimes) of the results of 2.
The information in 3 is available to the unconscious parts of your brain.
Loop back to step 1.

I think most people agree that scenario 2 happens at all the time. For example, we usually don’t consciously think about walking or driving to work, or striking each key on a keyboard when writing an email. The question is whether scenario 1 ever happens.

But again my question is, does it matter? Look again at the sequences. What changes if scenario 1 or scenario 2 are happening? Isn’t consciousness still having a causal effect on actions in scenario 2, albeit a delayed one?

Maybe the real distinction is how often and how early step 3 in scenario 2 happens? I think there’s no question that it varies depending on the situation. I presented the scenarios above as two discrete possibilities, but I suspect the reality is more of a spectrum, with various actions arising with varying frequencies into consciousness.

An interesting pain suppression tactic.

Romano and Maravita report that magnifying the visual size of one׳s own hand modulates pain anticipation and perception, reducing experiened pain, a technique that might be exploited for practical use:

How to reduce pain is a fundamental clinical and experimental question. Acute pain is a complex experience which seems to emerge from the co-activation of two main processes, namely the nociceptive/discriminative analysis and the affective/cognitive evaluation of the painful stimulus.

Recently it has been found that pain threshold increases following the visual magnification of the body part targeted by the painful stimulation. This finding is compatible with the well-known notion that body representation and perceptual experience relay on complex, multisensory factors. However, the level of cognitive processing and the physiological mechanisms underlying this analgesic effect are still to be investigated.

In the present work we found that following the visual magnification of a body part, the Skin Conductance Responses (SCR), to an approaching painful stimulus increases before contact and decreases following the real stimulation, compared to the non-distorted view of the hand. By contrast, an unspecific SCR increase is found when the hand is visually shrunk. Moreover a reduction of subjective pain experience was found specifically for the magnified hand in explicit pain ratings.

These findings suggest that the visual increase of body size enhances the cognitive, anticipatory component of pain processing; such an anticipatory reaction reduces the response to the following contact with the noxious stimulus.

The present results support the idea that cognitive aspects of pain experience relay on the multisensory representation of the body, and that could be usefully exploited for inducing a significant reduction of subjective pain experience.

Practice and sleep form different aspects of skill.

Because I am a pianist I find this work by Song and Cohen totally fascinating. It conforms to my own experience in learning new note sequences in a piano composition (currently I'm working on Scriabin's Etude Op. 8 no. 12 D sharp minor). A fingering sequence that I find difficult I can discover to be playing in head during momentary waking during the night, and on the next day the notes come much more easily. Song and Cohen's distinction of transition and ordinal forms also matches with my experience of being able to verbalize (declarative memory) versus 'just knowing' (procedural memory) a passage.

Performance for skills such as a sequence of finger movements improves during sleep. This has widely been interpreted as evidence for a role of sleep in strengthening skill learning. Here we propose a different interpretation. We propose that practice and sleep form different aspects of skill. To show this, we train 80 subjects on a sequence of key-presses and test at different time points to determine the amount of skill stored in transition (that is, pressing ‘2’ after ‘3’ in ‘4-3-2-1’) and ordinal (that is, pressing ‘2’ in the third ordinal position in ‘4-3-2-1’) forms. We find transition representations improve with practice and ordinal representations improve during sleep. Further, whether subjects can verbalize the trained sequence affects the formation of ordinal but not transition representations. Verbal knowledge itself does not increase over sleep. Thus, sleep encodes different representations of memory than practice, and may mediate conversion of memories between declarative and procedural forms.