Wednesday, April 16, 2014

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.

Tuesday, April 15, 2014

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.

Monday, April 14, 2014

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.

Friday, April 11, 2014

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.

Thursday, April 10, 2014

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.

Wednesday, April 09, 2014

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.

Tuesday, April 08, 2014

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.

Monday, April 07, 2014

Using imagination or memory to increase prosocial behavior.

Gaesser and Schacter test two simple techniques for altering empathy towards the suffering of others, useful perhaps at the scale of individuals, but not obviously useful for large groups in opposition.

Empathy plays an important role in human social interaction. A multifaceted construct, empathy includes a prosocial motivation or intention to help others in need. Although humans are often willing to help others in need, at times (e.g., during intergroup conflict), empathic responses are diminished or absent. Research examining the cognitive mechanisms underlying prosocial tendencies has focused on the facilitating roles of perspective taking and emotion sharing but has not previously elucidated the contributions of episodic simulation and memory to facilitating prosocial intentions. Here, we investigated whether humans’ ability to construct episodes by vividly imagining (episodic simulation) or remembering (episodic memory) specific events also supports a willingness to help others. Three experiments provide evidence that, when participants were presented with a situation depicting another person’s plight, the act of imagining an event of helping the person or remembering a related past event of helping others increased prosocial intentions to help the present person in need, compared with various control conditions. We also report evidence suggesting that the vividness of constructed episodes—rather than simply heightened emotional reactions or degree of perspective taking—supports this effect. Our results shed light on a role that episodic simulation and memory can play in fostering empathy and begin to offer insight into the underlying mechanisms.

Friday, April 04, 2014

Exercise protects retinas.

Gretchen Reynolds points to an article by Lawson et al. showing that the increase in blood levels of brain-derived neurotrophic factors (B.N.D.F.), known to promote neuron health and growth, apparently also raises BNDF levels in the retina. In a mouse model for retinal degeneration (vaguely analogous to human macular degeneration), exercise that raises BNDF levels inhibits the retinal deterioration caused by brief (4 hour) exposure to very bright lights.

Aerobic exercise is a common intervention for rehabilitation of motor, and more recently, cognitive function. While the underlying mechanisms are complex, BDNF may mediate much of the beneficial effects of exercise to these neurons. We studied the effects of aerobic exercise on retinal neurons undergoing degeneration. We exercised wild-type BALB/c mice on a treadmill (10 m/min for 1 h) for 5 d/week or placed control mice on static treadmills. After 2 weeks of exercise, mice were exposed to either toxic bright light (10,000 lux) for 4 h to induce photoreceptor degeneration or maintenance dim light (25 lux). Bright light caused 75% loss of both retinal function and photoreceptor numbers. However, exercised mice exposed to bright light had 2 times greater retinal function and photoreceptor nuclei than inactive mice exposed to bright light. In addition, exercise increased retinal BDNF protein levels by 20% compared with inactive mice. Systemic injections of a BDNF tropomyosin-receptor-kinase (TrkB) receptor antagonist reduced retinal function and photoreceptor nuclei counts in exercised mice to inactive levels, effectively blocking the protective effects seen with aerobic exercise. The data suggest that aerobic exercise is neuroprotective for retinal degeneration and that this effect is mediated by BDNF signaling.

Thursday, April 03, 2014

Another demonstration of the gender gap.

The observations of Brooks et al. are quite clear-cut:

We identify a profound and consistent gender gap in entrepreneurship, a central path to job creation, economic growth, and prosperity. Across a field setting (three entrepreneurial pitch competitions in the United States) and two controlled experiments, we find that investors prefer entrepreneurial pitches presented by male entrepreneurs compared with pitches presented by female entrepreneurs, even when the content of the pitch is the same. This effect is moderated by male physical attractiveness: attractive males are particularly persuasive, whereas physical attractiveness does not matter among female entrepreneurs. These findings fundamentally advance the science related to gender, physical attractiveness, psychological persuasion, bias, role expectations, and entrepreneurship.

Wednesday, April 02, 2014

Can body language be read more reliably by computers than by humans?

This post continues the thread started in my March 20 post "A debate on what faces can tell us." Enormous effort and expense has gone into training security screeners to read body language in an effort to detect possible terrorists. John Tierney notes that there is no evidence that this effort at airports has accomplished much beyond inconveniencing tens of thousands of passengers a year. He points to more than 200 studies in which:

...people correctly identified liars only 47 percent of the time, less than chance. Their accuracy rate was higher, 61 percent, when it came to spotting truth tellers, but that still left their overall average, 54 percent, only slightly better than chance. Their accuracy was even lower in experiments when they couldn’t hear what was being said, and had to make a judgment based solely on watching the person’s body language.
A comment on the March 20 post noted work by UC San Diego researchers who have developed software that appears to be more successful than human decoders of facial movements because it more effectively follows dynamics of facial movements that are markers for voluntary versus involuntary underlying nerve mechanisms. Here are highlights and summary from Bartlett et al.:

Highlights
-Untrained human observers cannot differentiate faked from genuine pain expressions
-With training, human performance is above chance but remains poor
-A computer vision system distinguishes faked from genuine pain better than humans
-The system detected distinctive dynamic features of expression missed by humans

Summary
In highly social species such as humans, faces have evolved to convey rich information for social interaction, including expressions of emotions and pain. Two motor pathways control facial movement: a subcortical extrapyramidal motor system drives spontaneous facial expressions of felt emotions, and a cortical pyramidal motor system controls voluntary facial expressions. The pyramidal system enables humans to simulate facial expressions of emotions not actually experienced. Their simulation is so successful that they can deceive most observers. However, machine vision may be able to distinguish deceptive facial signals from genuine facial signals by identifying the subtle differences between pyramidally and extrapyramidally driven movements. Here, we show that human observers could not discriminate real expressions of pain from faked expressions of pain better than chance, and after training human observers, we improved accuracy to a modest 55%. However, a computer vision system that automatically measures facial movements and performs pattern recognition on those movements attained 85% accuracy. The machine system’s superiority is attributable to its ability to differentiate the dynamics of genuine expressions from faked expressions. Thus, by revealing the dynamics of facial action through machine vision systems, our approach has the potential to elucidate behavioral fingerprints of neural control systems involved in emotional signaling. In highly social species such as humans, faces have evolved to convey rich information for social interaction, including expressions of emotions and pain. Two motor pathways control facial movement: a subcortical extrapyramidal motor system drives spontaneous facial expressions of felt emotions, and a cortical pyramidal motor system controls voluntary facial expressions. The pyramidal system enables humans to simulate facial expressions of emotions not actually experienced. Their simulation is so successful that they can deceive most observers. However, machine vision may be able to distinguish deceptive facial signals from genuine facial signals by identifying the subtle differences between pyramidally and extrapyramidally driven movements. Here, we show that human observers could not discriminate real expressions of pain from faked expressions of pain better than chance, and after training human observers, we improved accuracy to a modest 55%. However, a computer vision system that automatically measures facial movements and performs pattern recognition on those movements attained 85% accuracy. The machine system’s superiority is attributable to its ability to differentiate the dynamics of genuine expressions from faked expressions. Thus, by revealing the dynamics of facial action through machine vision systems, our approach has the potential to elucidate behavioral fingerprints of neural control systems involved in emotional signaling.

Tuesday, April 01, 2014

Evolved music specific brain reward systems.

Perhaps the most plausible suggestion for why music is universal in human societies is that it plays a central role in emotional social signaling that could have promoted group cohesion. Clark et al. comment on new work by Mas-Herrero et al. who have now documented a group of healthy people who, while responding to typical rewarding stimuli, appear to have a specific musical anhedonia, deriving no pleasure from music even though perceiving it normally. They cannot experience the intensely pleasurable shivers down the spine or ‘chills’ that are specific to and reliably triggered by particular musical features like the resolution of tonal ambiguity. These active a distributed brain network including phylogenetically ancient limbic, stratal and midbrain structures also engaged by cocaine and sex. Clips from Clark et al.:

The musical anhedonia found by Mas-Herreo et al. is specific for musical reward assignment, rather than attributable to any deficiency in perceiving or recognising music or musical emotions. It is rooted in reduced autonomic reactivity rather than simply cognitive mislabelling. Moreover, it is not attributable to more general hedonic blunting, because musically anhedonic individuals show typical responses to other sources of biological and non-biological (monetary) reward. The most parsimonious interpretation of the new findings is that there are music-specific brain reward systems to which individuals show different levels of access….specific brain substrates for music coding … implies that these evolved in response to some biological imperative. But what might that have been?
The answer may lie in the kinds of puzzles that music helped our hominid ancestors to solve. Arguably the most complex, ambiguous and puzzling patterns we are routinely required to analyse are the mental states and motivations of other people, with clear implications for individual success in the social milieu. Music can model emotional mental states and failure to deduce such musical mental states correlates with catastrophic inter-personal disintegration in the paradigmatic acquired disorder of the human social brain, frontotemporal dementia …Furthermore, this music cognition deficit implicates cortical areas engaged in processing both musical reward and ‘theory of mind’ (our ability to infer the mental states of other people). Our hominid ancestors may have coded surrogate mental states in the socially relevant form of vocal sound patterns. By allowing social routines to be abstracted, rehearsed and potentially modified without the substantial cost of enacting the corresponding scenarios, such coding may have provided an evolutionary mechanism by which specific brain linkages assigned biological reward value to precursors of music.
These new insights into musical anhedonia raise many intriguing further questions. What is its neuroanatomical basis? The strong prediction would lie with mesolimbic dopaminergic circuitry, but functional neuroimaging support is sorely needed.
Here is the summary from the Mas-Herrero paper:
Music has been present in all human cultures since prehistory, although it is not associated with any apparent biological advantages (such as food, sex, etc.) or utility value (such as money). Nevertheless, music is ranked among the highest sources of pleasure, and its important role in our society and culture has led to the assumption that the ability of music to induce pleasure is universal. However, this assumption has never been empirically tested. In the present report, we identified a group of healthy individuals without depression or generalized anhedonia who showed reduced behavioral pleasure ratings and no autonomic responses to pleasurable music, despite having normal musical perception capacities. These persons showed preserved behavioral and physiological responses to monetary reward, indicating that the low sensitivity to music was not due to a global hypofunction of the reward network. These results point to the existence of specific musical anhedonia and suggest that there may be individual differences in access to the reward system.

Monday, March 31, 2014

Mechanism of muscle decay on aging, and its reversal.

Humans in their 70's and 80's experience a loss of skeletal muscle mass and strength (sarcopenia) that correlates with an increase in mortality in older populations. One reason this loss occurs is because the regenerative capacity of muscle stem cells (called satellite cells) declines with age as they switch from a quiescent state (from which they can emerge to generate new muscle progenitor cells) to a senescent-like state, which impairs the regeneration process, including activation, proliferation and self-renewal. Sousa-Victor et al. report, in experiments on aging mice, that this switch is caused by derepression of the gene encoding p16INK4a, a regulator of cellular senescence.  They find that genetically silencing p16INK4a in geriatric satellite cells restores quiescence and muscle regenerative functions, suggesting a possible clinical strategy for rejuvenating satellite cells.  I pass on this graphical summary of their results from the review by Li and Belmonte, followed by the abstract of their article.



Legend:
a. Satellite cells, a type of muscle stem cell, remain quiescent under normal conditions. After muscle damage, satellite cells become activated and re-enter the cell cycle to produce muscle progenitor cells that regenerate new muscle fibres. They also self-renew to replenish the stem-cell population. b, Sousa-Victor et al.3 report that during ageing, geriatric satellite cells lose their reversible quiescent state owing to derepression of the gene encoding p16INK4a, a regulator of cellular senescence. Instead, they adopt a senescent-like state (becoming pre-senescent cells), which impairs the regeneration process, including activation, proliferation and self-renewal.
Abstract:
Regeneration of skeletal muscle depends on a population of adult stem cells (satellite cells) that remain quiescent throughout life. Satellite cell regenerative functions decline with ageing. Here we report that geriatric satellite cells are incapable of maintaining their normal quiescent state in muscle homeostatic conditions, and that this irreversibly affects their intrinsic regenerative and self-renewal capacities. In geriatric mice, resting satellite cells lose reversible quiescence by switching to an irreversible pre-senescence state, caused by derepression of p16INK4a (also called Cdkn2a). On injury, these cells fail to activate and expand, undergoing accelerated entry into a full senescence state (geroconversion), even in a youthful environment. p16INK4a silencing in geriatric satellite cells restores quiescence and muscle regenerative functions. Our results demonstrate that maintenance of quiescence in adult life depends on the active repression of senescence pathways. As p16INK4a is dysregulated in human geriatric satellite cells, these findings provide the basis for stem-cell rejuvenation in sarcopenic muscles.

Friday, March 28, 2014

Our lives are a concept, not a reality.

It is useful to occasionally be reminded of our essential strangeness, something I attempted in my "I-Illusion" web/lecture some years ago. Associate Scientific American editor Ferris Jabr engages this strangeness in his brief essay "Why nothing is truly alive". He notes the amazing life-like moving sculptures of Dutch artist Theo Jansen (see video), and points out how attempts to define life - as NASA has tried in defining the goal of what a search for extra-terrestrial life would look for - have floundered, the simple point being that while the concept of life sometimes has its pragmatic value for our particular human purposes, it does not reflect the reality of the universe outside the mind. Life is a concept, not a reality.

To better understand this argument, it’s helpful to distinguish between mental models and pure concepts. Sometimes the brain creates a representation of a thing: light bounces off a pine tree and into our eyes; molecules waft from its needles and ping neurons in our nose; the brain instantly weaves together these sensations with our memories to create a mental model of that tree. Other times the brain develops a pure concept based on observations — a useful way of thinking about the world. Our idealized notion of “a tree” is a pure concept. There is no such thing as “a tree” in the world outside the mind...Likewise, “life” is an idea. We find it useful to think of some things as alive and others as inanimate, but this division exists only in our heads.
Recognizing life as a concept is, in many ways, liberating. We do not need to recoil from our impulse to endow Mr. Jansen’s sculptures with “life” because they move on their own. The real reason Strandbeest enchant us is the same reason that any so-called “living thing” fascinates us: not because it is “alive,” but because it is so complex and, in its complexity, beautiful.

Thursday, March 27, 2014

Restoring mitochondrial dysfunction associated with aging.

The aging of our bodies is by definition cellular aging, and it is hard to keep track with all the theories on why cells age. One of the most venerable models is that increasing damage to energy producing mitochondria in cells is a fundamental cause of cell decay and death. Mitochondrial energy production is accompanied by a low level of the aberrant production of reactive oxygen species (ROS) that damage mitochondria DNA and proteins. Another model suggested by Sinclair and colleagues is that alterations in nuclear gene expression due to reduced activity of the deacetylase SIRT1 may be the culprit. (SIRT1 is the enzyme linked to the anti-aging activity of resveratrol). Increasing this activity by increasing NAD+ (the energy coenzyme Nicotine Adenine Dinucleotide) levels can reverse age-dependent mitochondrial dysfunction. Here are highlights and the summary of their article.

Highlights
-A specific decline in mitochondrially encoded genes occurs during aging in muscle
-Nuclear NAD+ levels regulate mitochondrial homeostasis independently of PGC-1α/β
-Declining NAD+ during aging causes pseudohypoxia, which disrupts OXPHOS function
-Raising nuclear NAD+ in old mice reverses pseudohypoxia and metabolic dysfunction

Summary
Ever since eukaryotes subsumed the bacterial ancestor of mitochondria, the nuclear and mitochondrial genomes have had to closely coordinate their activities, as each encode different subunits of the oxidative phosphorylation (OXPHOS) system. Mitochondrial dysfunction is a hallmark of aging, but its causes are debated. We show that, during aging, there is a specific loss of mitochondrial, but not nuclear, encoded OXPHOS subunits. We trace the cause to an alternate PGC-1α/β-independent pathway of nuclear-mitochondrial communication that is induced by a decline in nuclear NAD+ and the accumulation of HIF-1α under normoxic conditions, with parallels to Warburg reprogramming. Deleting SIRT1 accelerates this process, whereas raising NAD+ levels in old mice restores mitochondrial function to that of a young mouse in a SIRT1-dependent manner. Thus, a pseudohypoxic state that disrupts PGC-1α/β-independent nuclear-mitochondrial communication contributes to the decline in mitochondrial function with age, a process that is apparently reversible.

Wednesday, March 26, 2014

Out of Sight, Out of Mind

It has been a common supposition that suppressing conscious recall of unpleasant or traumatic memories doesn't prevent their stealthly emotionally damaging unconscious effects. Assuming this, various talk therapies attempt to elicit recall, "working through", and desensitization to, the trauma. Gagnepain at al. use now provide direct evidence that a frontal, top-down, inhibition suppresses both explicit and implicit visual cortex activities that correlate with the memories. They found that suppressing visual memories made it harder for people to later see the suppressed object compared to other recently seen objects. (Brain activity was recorded using functional magnetic resonance imaging (fMRI) while participants either thought of the object image when given its reminder word, or instead tried to stop the memory of the picture from entering their mind.) Here is their abstract:

Suppressing retrieval of unwanted memories reduces their later conscious recall. It is widely believed, however, that suppressed memories can continue to exert strong unconscious effects that may compromise mental health. Here we show that excluding memories from awareness not only modulates medial temporal lobe regions involved in explicit retention, but also neocortical areas underlying unconscious expressions of memory. Using repetition priming in visual perception as a model task, we found that excluding memories of visual objects from consciousness reduced their later indirect influence on perception, literally making the content of suppressed memories harder for participants to see. Critically, effective connectivity and pattern similarity analysis revealed that suppression mechanisms mediated by the right middle frontal gyrus reduced activity in neocortical areas involved in perceiving objects and targeted the neural populations most activated by reminders. The degree of inhibitory modulation of the visual cortex while people were suppressing visual memories predicted, in a later perception test, the disruption in the neural markers of sensory memory. These findings suggest a neurobiological model of how motivated forgetting affects the unconscious expression of memory that may be generalized to other types of memory content. More generally, they suggest that the century-old assumption that suppression leaves unconscious memories intact should be reconsidered.

Tuesday, March 25, 2014

Clash of 'grand theories' of consciousness??

In what strikes me in the most unlikely venue, The Huffington Post, new age guru (also savvy businessman and marketer) Deepak Chopra offers what seems to an equivalent to the "teach the controversy" arguments of the creationists. The title "'Collision Course' in the Science of Consciousness: Grand Theories to Clash at Tucson Conference" suggests that there are two grand theories when in fact there are not. Massive evidence supports the idea that consciousness is accounted for by complex interactions between nerve cells, and Chopra does a nice summary of two central researchers taking this approach:

Christof Koch now teams with psychiatrist and neuroscientist Giulio Tononi in applying principles of integrated information, computation and complexity to the brain's neuronal and network-level electrochemical activities. In their view, consciousness depends on a system's ability to integrate complex information, to compute particular states from among possible states according to algorithms. Deriving a measure of complex integration from EEG signals termed 'phi', they correlate consciousness with critically complex levels of 'phi'.
Regarding the 'hard problem', Koch, Tononi and their physicist colleague Max Tegmark have embraced a form of panpsychism in which consciousness is a property of matter. Simple particles are conscious in a simple way, whereas such particles, when integrated in complex computation, become fully conscious (the 'combination problem' in panpsychism philosophy). Tegmark has termed conscious matter 'perceptronium', and his alliance with Koch and Tononi is Crick's legacy and a major force in the present-day science of consciousness. Their view of neurons as fundamental units whose complex synaptic interactions account for consciousness, also supports widely-publicized, and well-funded 'connectome' and 'brain mapping' projects hoping to capture brain function in neuronal network architecture.
I can see absolutely nothing but gibberish in the vague array alternatives to this sort of approach mentioned by Chopra, Penrose, Hameroff and others: non-computational, quantum superpositional, connected to spacetime geometry, involving coherent cellular microtubule states. Elegant hand waving perhaps, but where is the model? How is it to be tested?

Monday, March 24, 2014

Shaping memory accuracy by TCDS

Here is yet another example, from Zwissler et al., of how different brain processes, in this case memory, can be tweaked by trans-cranial direct current stimulation (DCTS) - passing very weak currents between electrodes places on our scalps. In most of these reports, there are suggestions of possible future therapeutic applications. The abstract:

Human memory is dynamic and flexible but is also susceptible to distortions arising from adaptive as well as pathological processes. Both accurate and false memory formation require executive control that is critically mediated by the left prefrontal cortex (PFC). Transcranial direct current stimulation (tDCS) enables noninvasive modulation of cortical activity and associated behavior. The present study reports that tDCS applied to the left dorsolateral PFC (dlPFC) shaped accuracy of episodic memory via polaritiy-specific modulation of false recognition. When applied during encoding of pictures, anodal tDCS increased whereas cathodal stimulation reduced the number of false alarms to lure pictures in subsequent recognition memory testing. These data suggest that the enhancement of excitability in the dlPFC by anodal tDCS can be associated with blurred detail memory. In contrast, activity-reducing cathodal tDCS apparently acted as a noise filter inhibiting the development of imprecise memory traces and reducing the false memory rate. Consistently, the largest effect was found in the most active condition (i.e., for stimuli cued to be remembered). This first evidence for a polarity-specific, activity-dependent effect of tDCS on false memory opens new vistas for the understanding and potential treatment of disturbed memory control.

Friday, March 21, 2014

Do brain workouts work?

I've done numerous posts on brain training websites, and have ended up enjoying returning to the one started up by Michael Merzenich, Posit Science. I want to pass on this link to the latest article I've seen discussing the usefulness of brain training regimes. The article points out that the science has not kept up with the hype. But, one study has suggested that games engaging attention, speed of processing, and short term memory improve general cognitive skills for as long as 5-10 years. Here is a clip:

In January, the largest randomized controlled trial of cognitive training in healthy older adults found that gains in reasoning and speed through brain training lasted as long as 10 years. Financed by the National Institutes of Health, the Active study (Advanced Cognitive Training for Independent and Vital Elderly) recruited 2,832 volunteers with an average age of 74.
The participants were divided into three training groups for memory, reasoning and speed of processing, as well as one control group. The groups took part in 10 sessions of 60 to 75 minutes over five to six weeks, and researchers measured the effect of training five times over the next 10 years. Five years after training, all three groups still demonstrated improvements in the skills in which they had trained. Notably, the gains did not carry over into other areas. After 10 years, only the reasoning and speed-of-processing groups continued to show improvement...The researchers also found that people in the reasoning and speed-of-mental-processing groups had 50 percent fewer car accidents than those in the control group.

Thursday, March 20, 2014

A debate on what faces can tell us.

Security agencies are developing facial emotion profiling software for use at checkpoints, while Apple and Google are working on using your laptop camera to tell them what kind of mood you are in while shopping online. Such approaches are based on the assumption that a basic set of facial emotions are invariant across cultures and universally understood. A large body of work, starting with Charles Darwin and especially since the 1960's done by Paul Ekman and others has substantiated this idea.

In yet another New York Times Op-Ed advertisement wanting to raise the visibility of some basic research, Barrett and collaborators make the heretical claim that this assumption is wrong and point to their articles questioning Ekman's original research protocol of asking individuals in cultures isolated from outside contact for many centuries to match photographs of faces with a preselected set of emotion words. They suspected that providing subjects with a preselected set of emotion words might inadvertently prime the subjects, in effect hinting at the answer, and thus skew the results. In one set of experiments subjects not given any clues and asked to freely describe the emotion on a face or state whether emotions of two faces were the same or different performed less well. When further steps were taken to prevent priming, performance fell further.

A rejoinder from Paul Ekman and Dacher Keltner points out that a number of studies supporting Charles Darwin's original observations suggesting that facial movements are evolved behaviors have avoided the issues raised by Barrett et al. by simply measuring spontaneous facial expressions in different cultures, along with the physiological activity that differed when various universal facial expressions occurred.  It seems reasonable that a universal facial emotional repertoire might in practice be skewed by culturally relative linguistic conventions,  thus helping to explain Barrett et al's observations.