Massive reorganization of visual cortex at the level of dendritic spines..

Keck et al. do elegant experiments to directly observe spine replacement in individual apical dendritic tufts of layer-5 pyramidal neurons, replacement that correlates with functional recovery over a period of months after lesioning the retinal input:

The cerebral cortex has the ability to adapt to altered sensory inputs. In the visual cortex, a small lesion to the retina causes the deprived cortical region to become responsive to adjacent parts of the visual field. This extensive topographic remapping is assumed to be mediated by the rewiring of intracortical connections, but the dynamics of this reorganization process remain unknown. We used repeated intrinsic signal and two-photon imaging to monitor functional and structural alterations in adult mouse visual cortex over a period of months following a retinal lesion. The rate at which dendritic spines were lost and gained increased threefold after a small retinal lesion, leading to an almost complete replacement of spines in the deafferented cortex within 2 months. Because this massive remodeling of synaptic structures did not occur when all visual input was removed, it likely reflects the activity-dependent establishment of new cortical circuits that serve the recovery of visual responses.

A novel theory of mental disorders

Benedict Carey writes a useful article on a radical new theory for explaining the psychotic spectrum:

...that an evolutionary tug of war between genes from the father’s sperm and the mother’s egg can, in effect, tip brain development in one of two ways. A strong bias toward the father pushes a developing brain along the autistic spectrum, toward a fascination with objects, patterns, mechanical systems, at the expense of social development. A bias toward the mother moves the growing brain along what the researchers call the psychotic spectrum, toward hypersensitivity to mood, their own and others’. This, according to the theory, increases a child’s risk of developing schizophrenia later on, as well as mood problems like bipolar disorder and depression.

In short: autism and schizophrenia represent opposite ends of a spectrum that includes most, if not all, psychiatric and developmental brain disorders. The theory has no use for psychiatry’s many separate categories for disorders, and it would give genetic findings an entirely new dimension.

The theory leans heavily on the work of David Haig of Harvard. It was Dr. Haig who argued in the 1990s that pregnancy was in part a biological struggle for resources between the mother and unborn child. On one side, natural selection should favor mothers who limit the nutritional costs of pregnancy and have more offspring; on the other, it should also favor fathers whose offspring maximize the nutrients they receive during gestation, setting up a direct conflict.

I strongly recommend that you read the article, which goes on to give a lucid explanation of how gene imprinting regulates this competition.

Language evolution embedded in cooperative social context

Another installment in the Nature series "Being Human" is offered by Szathmáry and Számadó , who put the case that language evolved in a highly social, cooperative context as one of a suite of uniquely human traits, meriting special status because of the opportunities that it opened up.

The subliminal power of logos

An interesting article by Rob Walker in the New York Times Magazine: "The Brand-ness of Strangers."

In one study, each subject was shown 20 photographs of people in various situations and instructed to focus on facial expressions. Afterward, each subject was offered a bottle of water from a selection of four brands. The experiment had nothing to do with facial expressions and everything to do with which kind of water they chose: the subjects had been divided into groups, based on how many of the photos they viewed incidentally included a bottle of Dasani water. Among those who looked at Dasani-free pictures, about 17 percent chose that brand. But about 40 percent of those who viewed a group of pictures that included 12 with a Dasani presence made the brand their pick. Since subjects who actually noticed the brand in the pictures were eliminated from the results, that spike in popularity evidently came from exposure that the subjects weren’t even aware of.

He discusses the very successful Ralph Lauren logo

Needless to say, a successful logo like Polo’s isn’t easy to create. But having attained and maintained such a level of familiarity, that logo may now be as effective as any of Ralph Lauren’s seductive ads — and for exactly the opposite reason: Not because it catches our attention, but because it doesn’t.

Is the financial meltdown a guy thing?

Dobrzynski asks whether traders have become prisoners of their endocrine systems — ruled by testosterone, the elixir of male aggressiveness, during a bull market; and by cortisol, a steroid that helps the body deal with stress, when the bears take over.

From Genes to Social Behavior

The Nov. 7 issue of Science Magazine is a gold mine of articles on genetics and behavior. I'm giving you here a clip from from the introduction to this special issue by Jasny et al. that contains links to the individual articles.

When it comes to behavior, we have moved beyond genetic determinism. Our genes do not lock us into certain ways of acting; rather, genetic influences are complicated and mutable and are only one of many factors affecting behavior. In their editorial, Landis and Insel (p. 821) elaborate on this idea, explaining that proteins encoded by genes direct the formation of multicomponent neural circuits, which are the true substrates of behavior, as these circuits respond to internal and outside stimuli.

Why do we study the genetic underpinnings of behavior? One reason is to understand how certain behaviors evolve. Conserved neural pathways can be tied to the evolution of social behaviors (Robinson et al., p. 896), and the conserved peptides oxytocin and vasopressin regulate social cognition and reproductive behaviors in many species (Donaldson and Young, p. 900). In a News story, Pennisi focuses on a region of chromosome 17 that has a complicated pattern of evolution in humans and other primates and is linked in unexpected ways to various disorders, including mental retardation, learning disabilities, and dementias.

Genetics can help us understand why identical circumstances can elicit different behavioral responses among individuals. Genetic differences are reflected in variations in behavior; activation of distinct versions of a hormone receptor gene, an example Donaldson and Young present, results in monogamous behavior in one species of vole but not in another. Conversely, as Robinson et al. describe, insights from recent work show that perceiving social information--such as bird songs or dominance behavior from cichlid fish--from another individual of the same species can itself alter gene expression in the brain, with downstream effects on physiology and behavior.

The potent genetic tools available for Drosophila have uncovered many genes that, when deleted, disrupt behaviors. This, in turn, has allowed dissection of the neural circuits that control essential behaviors. One of the best understood is a social activity necessary for reproduction--stereotypical mating behavior--as outlined by Dickson (p. 904). Genetic methods have also led to the understanding of another class of behaviors: those driven by the circadian clock. The genetic basis of the clock was elegantly worked out in Drosophila, followed by a similar achievement in mice. The reasons for these successes are outlined by Takahashi in his Perspective (p. 909), in which he also explains what tools will be needed to attain similar advances for other behaviors in mice.

Humans are not as genetically tractable as mice or flies, and human behavior is not as stereotypical. Holden's News story on the strengths and shortcomings of genetic studies of personality illustrates this point (p. 892). So do Cotton and some members of the Human Variome Project community in a Policy Forum (p. 861) that describes how the genes and loci associated with disorders of the nervous system are a particular challenge to geneticists and clinical neurologists in need of reliable diagnostic tests. And in a Perspective on a critical human social activity--politics--Fowler and Schreiber (p. 912) argue that genetics and neurobiology have much to teach us about how our leaders are chosen.

Some believe that psychology is the last frontier of genetic analysis. This special section provides a sampling of our early explorations.

Suffering Souls

A fascinating article in The New Yorker by John Seabrook on the search for the roots of psychopathy, the condition of moral emptiness that affects between fifteen to twenty-five per cent of the North American prison population, and is believed by some psychologists to exist in one per cent of the general adult male population. (Female psychopaths are thought to be much rarer.) Psychopaths don’t exhibit the manias, hysterias, and neuroses that are present in other types of mental illness. Their main defect, what psychologists call “severe emotional detachment”—a total lack of empathy and remorse—is concealed, and harder to describe than the symptoms of schizophrenia or bipolar disorder. It focuses on the work of Kent Kiehl, who has installed an fMRI scanner in a New Mexico prison. His theory, published in Psychiatry Research, in 2006, is that psychopathy is caused by a defect in what he calls “the paralimbic system,” a network of brain regions, stretching from the orbital frontal cortex to the posterior cingulate cortex, that are involved in processing emotion, inhibition, and attentional control.

Most popular MindBlog posts...

I sometimes glance at several of the free services that offer to monitor activity on one's blog (Feedburner, Google Analytics, Quantcast, etc). I thought this compilation of the most widely read posts on this blog was interesting. You can find any of them by entering a few words of the title in the search box in the left column.


And, in this vein, here is the history of subscribers to the RSS feed of this blog:

Sleep loss produces false memories.

From Diekelmann et al. :

People sometimes claim with high confidence to remember events that in fact never happened, typically due to strong semantic associations with actually encoded events. Sleep is known to provide optimal neurobiological conditions for consolidation of memories for long-term storage, whereas sleep deprivation acutely impairs retrieval of stored memories. Here, focusing on the role of sleep-related memory processes, we tested whether false memories can be created (a) as enduring memory representations due to a consolidation-associated reorganization of new memory representations during post-learning sleep and/or (b) as an acute retrieval-related phenomenon induced by sleep deprivation at memory testing. According to the Deese, Roediger, McDermott (DRM) false memory paradigm, subjects learned lists of semantically associated words (e.g., “night”, “dark”, “coal”,…), lacking the strongest common associate or theme word (here: “black”). Subjects either slept or stayed awake immediately after learning, and they were either sleep deprived or not at recognition testing 9, 33, or 44 hours after learning. Sleep deprivation at retrieval, but not sleep following learning, critically enhanced false memories of theme words. This effect was abolished by caffeine administration prior to retrieval, indicating that adenosinergic mechanisms can contribute to the generation of false memories associated with sleep loss.

Undoing cocaine's consequences.

In animal experiments stressful and aversive conditions can enhance drug-seeking and drug intake, while stress-reducing manipulations and nondrug rewards can reduce such behaviors. The acquisition of addiction-related behaviors such as sensitization and drug self-administration is attenuated in animals housed in enriched environments containing novel toys, food, and conspecifics with which to interact, compared with those housed in standard laboratory conditions. But, how is this relevant to treating drug-addicted humans, who present for treatment only after drug use is acquired? Recent work by Solinas et al. now suggests that environmental enrichment can still exert its beneficial effects on addiction-related behaviors even after they are established. Their abstract:

Environmental conditions can dramatically influence the behavioral and neurochemical effects of drugs of abuse. For example, stress increases the reinforcing effects of drugs and plays an important role in determining the vulnerability to develop drug addiction. On the other hand, positive conditions, such as environmental enrichment, can reduce the reinforcing effects of psychostimulants and may provide protection against the development of drug addiction. However, whether environmental enrichment can be used to “treat” drug addiction has not been investigated. In this study, we first exposed mice to drugs and induced addiction-related behaviors and only afterward exposed them to enriched environments. We found that 30 days of environmental enrichment completely eliminates behavioral sensitization and conditioned place preference to cocaine. In addition, housing mice in enriched environments after the development of conditioned place preference prevents cocaine-induced reinstatement of conditioned place preference and reduces activation of the brain circuitry involved in cocaine-induced reinstatement. Altogether, these results demonstrate that environmental enrichment can eliminate already established addiction-related behaviors in mice and suggest that environmental stimulation may be a fundamental factor in facilitating abstinence and preventing relapse to cocaine addiction.

During learning - competition between two memory systems.

An interesting bit of work from Lee et al.:

The multiple memory systems framework proposes that distinct circuits process and store different sorts of information; for example, spatial information is processed by a circuit that includes the hippocampus, whereas certain forms of instrumental conditioning depend on the striatum. Disruption of hippocampal function can enhance striatum-dependent learning in some paradigms, which has been interpreted as evidence that these systems can compete with one another in an intact animal. However, it remains unclear whether such competition can occur in the opposite direction, as suggested by the multiple memory systems framework, or is unidirectional. We addressed this question using lesions and genetic manipulations in mice. Impairment of dorsal striatal function with either excitotoxic lesions or transgenic inhibition of the transcription factor cAMP response element-binding protein, which disrupts striatal synaptic plasticity, impaired striatum-dependent cued learning but enhanced hippocampus-dependent spatial learning. Conversely, excitotoxic lesions of the dorsal hippocampus disrupted spatial learning and enhanced cued learning. This double dissociation demonstrates bidirectional competition that constitutes strong evidence for the parallel operation of distinct memory systems.

Enhanced logical consistency in autism.

Dolan's group has an interesting open access article in J. Neuroscience showing:

behavioral evidence that autism spectrum disorder (ASD) subjects show a reduced susceptibility to the framing effect and psycho-physiological evidence that they fail to incorporate emotional context into the decision-making process.

From their introduction:

Logical consistency across decisions, regardless of how choices are presented, is a central tenet of rational choice theory and the cornerstone of modern economic and political science. Empirical data challenge this perspective by showing that humans are highly susceptible to the manner or context in which options are cast, resulting in a decision bias termed the "framing effect". We have previously shown that the amygdala mediates this framing bias, a finding that highlights the importance of incorporating emotional processes within models of human decision making. An ability to integrate emotional contextual information into the decision process provides a useful heuristic in decision making under uncertainty. This is a factor that is likely to assume considerable importance during social interactions in which information about others is often incomplete, ambiguous, and not easily amenable to standard inferential reasoning processes.

In this study, we investigated the effect of contextual frame on choice behavior of individuals with autistic spectrum disorder (ASD). Autism is a neurodevelopmental disorder characterized by deficits in social interaction, qualitative impairments in communication, and repetitive and stereotyped patterns of behavior, interests, and activities. From Kanner's earliest description, it has been recognized that individuals with ASD have a strong tendency to focus on parts rather than global aspects of objects of interest and are unable to integrate disparate information into a meaningful whole (weak central coherence theory).

We previously proposed that susceptibility to a framing bias reflects the operation of an affect heuristic. Here, we show that individuals with ASD, a condition characterized by marked behavioral inflexibility, demonstrate a decreased susceptibility to framing resulting in an unusual enhancement in logical consistency that is paradoxically more in line with the normative prescriptions of rationality at the core of the current economics theory. Furthermore, insensitivity in these subjects to a contextual framing bias was associated with a failure to express a differential autonomic response to contextual cues as indexed in skin conductance responses (SCRs), a standard measure of emotional processing. Our findings suggest that a more consistent pattern of choice in the ASD group reflects a failure to incorporate emotional cues into the decision process, an enhanced economic "rationality" that may come at a cost of reduced behavioral flexibility.

Using both sides of your brain.

Schmidt writes a review article on specializations of the two hemispheres, which are seen in all vertebrates. He gives several examples of interhemispheric switching, and then focuses on the example of song production in passerine birds.

Chill-out...

From the "Random Samples" section of the Oct. 31 Science Magazine:

Psychologists at the University of Hertfordshire, U.K., last week unveiled what they are billing as "the world's most relaxing room." The 160-square-meter space, bathed in green lights with an artificially lit blue sky, is furnished with soft mats and lavender-scented pillows "to create a relaxing environment with no sense of threat," explains the project's mastermind Richard Wiseman.

The design is based on research on the effects of light, scent, and music in relaxation. "Cold colors such as blue and green tend to be perceived as calming, whereas warm colors can be perceived as arousing," explains Birgitta Gatersleben, an environmental psychologist from the University of Surrey in Guildford, U.K. Lavender is said to reduce anxiety and induce sleep by lowering the levels of the stress hormone cortisol. The room also features specially composed music with a slow, steady beat and low-frequency tones.

So far, the room's 200 visitors have given it mixed reviews. "Some people absolutely love it and can't have enough of it," Wiseman says. "But people who thrive on and need stress to work absolutely hate it."

The project was designed to be easy to replicate in offices and other real-life environments. "I would like to see relaxation rooms in public spaces," Wiseman adds. "If we pay 20p to use a toilet in King's Cross train station, why not pay for 20 minutes of peace?"

Symbolic markers, cultural groups, and ingroup favoritism

A 'This week in Science' section of Science Magazine points to the work of Efferson et al. :

In human social interactions, it is not uncommon to draw inferences about hidden characteristics (attitudes, beliefs, or behavioral norms) on the basis of observable markers that may bear no fundamental connection to the underlying quantity but have become associated with specific groups over time. For instance, individuals sporting insignia of the Boston Red Sox or Manchester United may be classified as friends (or foes, if one should happen to be a New York Yankees or Chelsea fan). Although much research has been devoted to how a member of one cultural or ethnic group views other in-group and out-group members, less is known about the process by which symbolic markers come to be used as signals to define group membership. Efferson et al. have designed a laboratory-based economic game in which subjects were free to associate arbitrary markers with varying payoffs. Cultural groups (those in which members had adopted the same marker) and consequent ingroup favoritism developed only when the marker was both predictive of behavior in the game as well as changeable over time.

The abstract from Efferson et al.:

Cultural boundaries have often been the basis for discrimination, nationalism, religious wars, and genocide. Little is known, however, about how cultural groups form or the evolutionary forces behind group affiliation and ingroup favoritism. Hence, we examine these forces experimentally and show that arbitrary symbolic markers, though initially meaningless, evolve to play a key role in cultural group formation and ingroup favoritism because they enable a population of heterogeneous individuals to solve important coordination problems. This process requires that individuals differ in some critical but unobservable way and that their markers be freely and flexibly chosen. If these conditions are met, markers become accurate predictors of behavior. The resulting social environment includes strong incentives to bias interactions toward others with the same marker, and subjects accordingly show strong ingroup favoritism. When markers do not acquire meaning as accurate predictors of behavior, players show a markedly reduced taste for ingroup favoritism. Our results support the prominent evolutionary hypothesis that cultural processes can reshape the selective pressures facing individuals and so favor the evolution of behavioral traits not previously advantaged.

Values of early music training.

Forgeard et al. show that children who receive at least three years of instrumental music training outperform their control counterparts on auditory discrimination abilities and fine motor skills, as well as vocabulary and nonverbal reasoning skills. They did not confirm a suggestion from previous research that music training enhances heightened spatial skills, phonemic awareness, or mathematical abilities.

The creationists go to war over the brain.

A Zoology colleague of mine pointed out an article by Amander Gefter (PDF here) in The New Scientist on a group of "non-materialist neuroscientists" that is trying to resurrect Cartesian Dualism. It is particularly sad that one of these is Jeffrey Schwartz, who has done classic work showing how cognitive therapy can amelioate obsessive compulsive disorder.

Schwartz used scanning technology to look at the neural patterns thought to be responsible for OCD. Then he had patients use "mindful attention" to actively change their thought processes, and this showed up in the brain scans: patients could alter their patterns of neural firing at will. From such experiments, Schwartz and others argue that since the mind can change the brain, the mind must be something other than the brain, something non-material. In fact, these experiments are entirely consistent with mainstream neurology - the material brain is changing the material brain.

Clearly, while there is a genuine attempt to appropriate neuroscience, it will not influence US laws or education in the way that anti-evolution campaigns can because neuroscience is not taught as part of the core curriculum in state-funded schools. But as Andy Clark, professor of logic and metaphysics at the University of Edinburgh, UK, emphasises: "This is real and dangerous and coming our way." He and others worry because scientists have yet to crack the great mystery of how consciousness could emerge from firing neurons. "Progress in science is slow on many fronts," says John Searle, a philosopher at the University of California, Berkeley. "We don't yet have a cure for cancer, but that doesn't mean cancer has spiritual causes." And for Patricia Churchland, a philosopher of neuroscience at the University of California, San Diego, "it is an argument from ignorance. The fact something isn't currently explained doesn't mean it will never be explained or that we need to completely change not only our neuroscience but our physics." The attack on materialism proposes to do just that, but it all turns on definitions. "At one time it looked like all physical causation was push/pull Newtonianism," says Owen Flanagan, professor of philosophy and neurobiology at Duke University, North Carolina. "Now we have a new understanding of physics. What counts as material has changed. Some respectable philosophers think that we might have to posit sentience as a fundamental force of nature or use quantum gravity to understand consciousness. These stretch beyond the bounds of what we today call 'material', and we haven't discovered everything about nature yet. But what we do discover will be natural, not supernatural."

And as Clark observes: "This is an especially nasty mind-virus because it piggybacks on some otherwise reasonable thoughts and worries. Proponents make such potentially reasonable points as 'Oh look, we can change our brains just by changing our minds,' but then leap to the claim that mind must be distinct and not materially based. That doesn't follow at all. There's nothing odd about minds changing brains if mental states are brain states: that's just brains changing brains."

A conference on "Happiness and its Causes."

There is a "Happiness and its Causes" conference in San Francisco Nov. 24-25, with very flashy marketing and quite a cast of stars: Paul Ekman, Robert Sapolsky, Anne Harrington and others.

Our brain's large scale functional architecture.

He et al. have published an important study that shows correlations between spontaneous fluctuations in slow cortical potentials recorded by electrocorticography and fMRI BOLD signals are maintained across wakefulness, slow-wave sleep, and rapid-eye-movement sleep. Balduzzi et al. note in their review of the work that the study

... makes it clear that both BOLD and ECoG fluctuations display a pattern of regional correlations, or functional connectivity, which closely reflects those regions' anatomical connectivity. Inverting a well known adagio, what wires together, fires together. Indeed, it seems that it could not be otherwise. If neurons are connected in a certain way, and if they are spontaneously active, functional connectivity is bound to reflect anatomical connectivity, just like traffic patterns must reflect the underlying roadmap.

The reviewers also give a nice description of alternative ideas about what the brain's spontaneous or background activity might be for:

The steady depolarization and firing of neurons, even when the brain is supposedly “at rest,” also called the “default mode” of activity, consumes approximately two-thirds of the brain's already disproportionate energy budget, so it better do something useful. For instance, spontaneous activity may be important for the brain's trillions of synapses, perhaps by keeping them exercised or consolidating and renormalizing their strength. Another notion is that spontaneous activity may be necessary to maintain a fluid state of readiness that allows the cortex to rapidly enter any of a number of available states or firing patterns—a kind of metastability. Theoretical work suggests that the repertoire of available states is maximal under moderate spontaneous activity, and shrinks dramatically with either complete inactivity or hyperactivity. But what kind of neural states? One possibility is that the cortex is like a sea undulating gently, and that evoked or task-related responses would be like small ripples on its surface. This possibility is consistent with fMRI studies, because spontaneous slow fluctuations in BOLD are as large or larger than those evoked by stimuli. Also, it would fit nicely with the trial-to-trial variability of behavioral responses. Another possibility is that there are distinct modes of neuronal activity, such as a READY mode and a GO mode (and possibly an inhibited, STOP mode). Spontaneous activity would then be the READY mode of neuronal firing signaling the absence of preferred stimuli (an ongoing, low-level buzz). By contrast, in the GO mode, neurons, or local populations of neurons, would signal the presence of a preferred stimulus by firing at much higher rates for short periods of time (a brief and loud shout). Unit recording studies have provided plenty of evidence that neurons respond strongly and distinctly to specific stimuli. In this view, the cortex would be more like a sea pierced by sharp islands. On the other hand, the slow hemodynamic response function underlying the BOLD signal may make fMRI partly blind to the distinction between slow, low-amplitude fluctuations in firing and fast, high-amplitude bursts of activity. If there are two modes of neural activity, it bears keeping in mind that neurons in the READY mode would be as necessary as neurons in the GO mode in specifying different cognitive states, just as the background is as necessary as the foreground.

The belt of enlightenment...

A map, via Andrew Sullivan's blog, of the counties, mainly in Arkansas through Appalachia, in which more people voted republican in 2008 than in 2004. Overlaps with maps of ignorance, racism and poverty. Not many MindBlog readers in this region!