Spread of Happiness - a network analysis.

A report by Fowler and Christakis, as noted by Belluck, is generating interest and controversy. In an analysis covering 20 years of the well known Framington Heart Study they find that happiness spreads like a contagion, that one's happiness is influence by the happiness of friends of friends. The issue is whether the study proved that people became happy because of their social contacts or some unrelated reason. In the same issue of the British Medical Journal, Cohen-Cole and Fletcher critique the work, showing that the statistical analysis used in network studies can detect implausible social network effects in acne, height, and headaches. Here is a summary graphic based on the work provided by the New York Times:

Cool Brain Trick....

I pass on this link to you because of my interest in music, a scale that always seems to be going down, but not getting much lower. It’s an auditory equivalent of an old-fashioned barber pole.

Compendium of brain blogs...

MindBlog reader Kelly points us to this recent posting of "101 Fascinating Brain Blogs"

Changing our body image can change pain perception.

Some remarkable observations by Moseley et al. :

The feeling that our body is ours, and is constantly there, is a fundamental aspect of self-awareness. Although it is often taken for granted, our physical self-awareness, or body image, is disrupted in many clinical conditions. One common disturbance of body image, in which one limb feels bigger than it really is, can also be induced in healthy volunteers by using local anaesthesia or cutaneous stimulation. Here we report that, in patients with chronic hand pain, magnifying their view of their own limb during movement significantly increases the pain and swelling evoked by movement. By contrast, minifying their view of the limb significantly decreases the pain and swelling evoked by movement. These results show a top-down effect of body image on body tissues, thus demonstrating that the link between body image and the tissues is bi-directional.

Larger hippocampus and superior pathfinding in the blind

From Fortin et al, work that confirms how unnecessary vision is for the construction of spatial concepts:

In the absence of visual input, the question arises as to how complex spatial abilities develop and how the brain adapts to the absence of this modality. We explored navigational skills in both early and late blind individuals and structural differences in the hippocampus, a brain region well known to be involved in spatial processing. Thirty-eight participants were divided into three groups: early blind individuals (n = 12; loss of vision before 5 years of age; mean age 33.8 years), late blind individuals (n = 7; loss of vision after 14 years of age; mean age 39.9 years) and 19 sighted, blindfolded matched controls. Subjects undertook route learning and pointing tasks in a maze and a spatial layout task. Anatomical data was collected by MRI. Remarkably, we not only show that blind individuals possess superior navigational skills than controls on the route learning task, but we also show for the first time a significant volume increase of the hippocampus in blind individuals [F(1,36) = 6.314; P ≤ 0.01; blind: mean = 4237.00 mm3, SE = 107.53; sighted: mean = 3905.74 mm3, SE = 76.27], irrespective of whether their blindness was congenital or acquired. Overall, our results shed new light not only on the construction of spatial concepts and the non-necessity of vision for its proper development, but also on the hippocampal plasticity observed in adult blind individuals who have to navigate in this space.

Neural mechanisms underlying memory failure in older adults

Here is a fascinating bit of work from Stevens et al. When failing to encode information older, but not younger, adults show increased activity in brain regions mediating distraction. This continues the developing consensus that aging brains (as I woefully note for mine) have increasing difficulty ignoring distracting information that is irrelevant to the task at hand :

Older adults have reduced memory, primarily for recall, but also for recognition, particularly for unfamiliar faces. Behavioral studies have shown that age-related memory declines are due in part to distraction from impaired inhibition of task-irrelevant input during encoding. Functional magnetic resonance imaging (fMRI) has been used to uncover the sources of memory deficits associated with aging. To date, this work has focused on successful encoding, while the neural correlates of unsuccessful encoding are unknown. Here, we provide novel evidence of a neural mechanism underlying memory failures exclusively affecting older adults. Whereas both younger and older adults showed reduced activation of brain regions important for encoding (e.g., hippocampus) during unsuccessful encoding, only older adults showed increased activity in brain regions mediating distraction (e.g., auditory cortex) and in left prefrontal cortex. Further, these regions were functionally connected with medial parietal areas, previously identified as default mode regions, which may reflect environmental monitoring. Our results suggest that increased distraction from task-irrelevant input (auditory in this case), associated with the unfamiliar and noisy fMRI environment, may increase environmental monitoring. This in turn could hinder suppression of default mode processing, resulting in memory failures in older adults. These findings provide novel evidence of a brain mechanism underlying the behavioral evidence that impaired inhibition of extraneous input during encoding leads to memory failure in older adults and may have implications for the ubiquitous use of fMRI for investigating neurocognitive aging.

Prefrontal regions mediating resistance versus vulnerability to depression.

Koenigs et al., in a study of humans with focal brain lesions, address the causality of depressive symptoms by showing that lesions to different parts of our prefrontal cortex can either enhance or decrease our expression of those symptoms:

The neuroanatomical correlates of depression remain unclear. Functional imaging data have associated depression with abnormal patterns of activity in prefrontal cortex (PFC), including the ventromedial (vmPFC) and dorsolateral (dlPFC) sectors. If vmPFC and dlPFC are critical neural substrates for the pathogenesis of depression, then damage to either area should affect the expression of depressive symptoms. Using patients with brain lesions we show that, relative to nonfrontal lesions, bilateral vmPFC lesions are associated with markedly low levels of depression, whereas bilateral dorsal PFC lesions (involving dorsomedial and dorsolateral areas in both hemispheres) are associated with substantially higher levels of depression. These findings demonstrate that vmPFC and dorsal PFC are critically and causally involved in depression, although with very different roles: vmPFC damage confers resistance to depression, whereas dorsal PFC damage confers vulnerability.

Degraded surroundings degrade behavior

Keizer et al. find support for the "Broken Windows Theory," that suggests that signs of disorderly and petty criminal behavior trigger more disorderly and petty criminal behavior, thus causing the behavior to spread. They find that if people see one norm or rule being violated (such as graffiti or a vehicle parked illegally), they're more likely to violate others--such as littering, or even stealing. Groningen citizens were given the opportunity to steal an envelope that obviously contained a 5 Euro note from a postbox. When the postbox was clean and tidy 13% took the bait; by contrast, 27% stole from a graffitied postbox and 25% from one with litter around it. Other tests showed that people are more likely to litter in the presence of graffiti or abandoned shopping trollies, and after hearing the crackle of illegal fireworks.

Does your cell phone signal damange your DNA? - round two

An exchange in the letters to the editor section of the Nov. 28 Science Magazine:

In her widely cited News of the Week story "Fraud charges cast doubt on claims of DNA damage from cell phone fields" (Science, 29 August, p. 1144), G. Vogel writes, "The only two peer-reviewed scientific papers showing that electromagnetic fields (EMFs) from cell phones can cause DNA breakage are at the center of a misconduct controversy at the Medical University of Vienna." Notwithstanding the allegations on both sides of the fence in this unresolved controversy, Vogel's opening comment and the title of her article are misleading. In fact, there are many other peer-reviewed papers from laboratories in at least seven countries, including the United States, showing that cell phone or similar low-intensity EMFs can break DNA or modulate it structurally [e.g., (1-9)].

Vini G. Khurana
Department of Neurosurgery
The Canberra Hospital
Australian National University
Canberra, ACT, Australia
E-mail: vgkhurana@gmail.com

References

1. R. J. Aitken, L. E. Bennetts, D. Sawyer, A. M. Wiklendt, B. V. King, Int. J. Androl. 28, 171 (2005).
2. W. Baohong et al., Toxicology 232, 311 (2007).
3. J. Y. Kim et al., Environ. Toxicol. 23, 319 (2008).
4. H. Lai, N. P. Singh, Int. J. Radiat. Biol. 69, 513 (1996).
5. S. Lixia et al., Mutat. Res. 602, 135 (2006).
6. R. Paulraj, J. Behari, Mutat. Res. 596, 76 (2006).
7. J. L. Phillips et al., Bioelectrochem. Bioenerget. 45, 103 (1998).
8. T. Nikolova et al., FASEB J. 19, 1686 (2005).
9. M. Mashevich et al., Bioelectromagnetics 24, 82 (2003).

Response
My intention was not to imply that there were only two papers showing any effects of EMFs. There are many publications that show effects of EMFs on DNA, but the citations listed here do not directly contradict the quoted sentence. Some see an effect in combination with other known agents that damage DNA. One finds an effect of microwaves, but in the range of microwave ovens and wireless LANs, not cell phones. Others look at DNA damage (for example, chromosome duplications), but not breakage. Several show mixed results: One finds a decrease in DNA breaks in three sets of exposed cells and an increase in one. Since the story was published, however, I have been made aware of a paper by Yao et al. (1), which also reported single-strand DNA breaks caused by EMFs equivalent to those from cell phones. I regret any misunderstanding the sentence caused.

Gretchen Vogel

Reference

1. K. Yao et al., Mol. Vision 14, 964 (2008).

MindBlog has moved south...

A personal note...I've spent the last week in transition between Madison Wisconsin (where it is 7 degrees farenheit right now) and Fort Lauderdale (where it is 72). I'll be here until mid-April. The picture is of one of my two Abyssinian kittens, looking out my condo window. The cats were great travelers in the car, watched the passing countryside as if they were dogs.

Foundations of neuroeconomics.

Clithero et al. offer an analysis and critique of the foundations of Neuroeconomics, the attempt to understand human economic behaviors in terms of underlying brain mechanisms.

Cyberchondria

An article by Markoff reminds me of the recent post on an example of the nocebo effect (Reading the drug side-effects label can make you sick). He describes a study by Microsoft suggesting that self-diagnosis by search engine frequently leads Web searchers to conclude the worst about what ails them.

They found that Web searches for things like headache and chest pain were just as likely or more likely to lead people to pages describing serious conditions as benign ones, even though the serious illnesses are much more rare...For example, there were just as many results that linked headaches with brain tumors as with caffeine withdrawal, although the chance of having a brain tumor is infinitesimally small.

Resveratrol promotes repair of DNA breaks that occur on aging

Nicholas Wade reports on work of Sinclair and collaborators (reported in Cell) that sirtulin, an enzyme activated by the red wine compound resveratrol, promotes the repair of breaks in DNA that occur on aging. (Ten previous MindBlog posts on resveratrol can be retrieved by entering "resveratrol" in the search box in the left column.) Resveratrol has many different effects, only some of which are exerted through sirtuin. While some people have been taking resveratrol with no apparent side effects, Mindblog's self-experiment found it causing arthritic symptoms, and that experience was reported by several who commented on that post.

Ventral and dorsal pathways for language

Finding an analogy to our visual system's partition of visual information into dorsal 'where' and ventral 'what' streams, Saur et al combine MRI and diffusion tensor imaging to provide support for a language processing model in which a dorsal stream is involved in mapping sound to articulation, and a ventral stream in mapping sound to meaning. Here is their abstract:

Built on an analogy between the visual and auditory systems, the following dual stream model for language processing was suggested recently: a dorsal stream is involved in mapping sound to articulation, and a ventral stream in mapping sound to meaning. The goal of the study presented here was to test the neuroanatomical basis of this model. Combining functional magnetic resonance imaging (fMRI) with a novel diffusion tensor imaging (DTI)-based tractography method we were able to identify the most probable anatomical pathways connecting brain regions activated during two prototypical language tasks. Sublexical repetition of speech is subserved by a dorsal pathway, connecting the superior temporal lobe and premotor cortices in the frontal lobe via the arcuate and superior longitudinal fascicle. In contrast, higher-level language comprehension is mediated by a ventral pathway connecting the middle temporal lobe and the ventrolateral prefrontal cortex via the extreme capsule. Thus, according to our findings, the function of the dorsal route, traditionally considered to be the major language pathway, is mainly restricted to sensory-motor mapping of sound to articulation, whereas linguistic processing of sound to meaning requires temporofrontal interaction transmitted via the ventral route.

Destroying memories to strengthen them

Lee reports work with rats showing that the core mechanisms that strengthen memories have more in common with the mechanisms that support memory reconsolidation than those that participate in initial memory storage. Memories are dynamic, rather than static, in nature. The reactivation of a memory through re-exposure to salient training stimuli results in its destabilization, necessitating a restabilization process known as reconsolidation, a disruption of which leads to amnesia. He finds that one normal function of hippocampal memory reconsolidation in rats is to modify the strength of a contextual-fear memory as a result of further learning.

A summary figure from Rudy's review of the article:

(a) The contextual-fear conditioning procedures that were used to study reconsolidation and memory strengthening are very similar. Note that the only difference between them is that the shock unconditioned stimulus was presented in phase II of the memory strengthening procedure, but the subject was only exposed to the context in the reconsolidation procedure. (b) Exposure to just a retrieval cue or a second conditioning trial will retrieve the established memory trace from long-term memory. This will result in the activation of the UPS, which will uncouple the synapses that support the trace, and the activation of Zip268 and the subsequent production of molecules, protein synthesis (PS), needed to rebuild or strengthen the trace.

The idea that retrieval can disrupt the synaptic basis of an established memory trace is counterintuitive. Nevertheless, the ubiquitin-proteasome system (UPS) has recently been identified as a key component of this process. Ubiquitin tags proteins for degradation and the proteasome degrades them. Retrieval of a contextual-fear memory is associated with polyubiquitinization of important postsynaptic density scaffolding proteins in the hippocampus.If proteolysis is prevented, then the memory trace should not degrade and would not have to be rebuilt from new protein.

Measuring the real-time chemistry of reward and aversion

fMRI studies suggest that nucleus accumbens (NAc) activation increases in response to stimuli of different hedonic valence, whereas physiological evidence suggests that NAc neurons show increases in activity for rewarding stimuli and pauses for aversive stimuli. Using cyclic voltammetry, Roitman et al. find that patterns of dopamine release and metabolic activity differentiate between rewarding and aversive stimuli. From their text:

It is controversial whether dopamine release in the NAc exclusively signals aspects of reward or serves a more broad purpose for signaling novelty or salience regardless of hedonic value...To dissociate salience or novelty from hedonic valence, we delivered brief intra-oral infusions of sucrose and quinine solutions to naive behaving rats and measured changes in dopamine concentration and pH in the NAc every 100 ms using fast-scan cyclic voltammetry. The pH measurements provide a measure of metabolic activity and thus an indirect measure of general neuronal activity.Appetitive (0.3 M sucrose) and aversive (0.001 M quinine) stimuli were delivered intra-orally to ensure equal exposure and transduction via the same sensory modality: the taste system. Each animal received both appetitive and aversive stimuli at unpredictable times to ensure comparable novelty and salience but opposing hedonic valence. This design elicited strong and consistent behavioral differences in hedonic expression with no evidence of anticipatory or conditioned responses. Voltammetric recordings permitted real-time detection of dopamine release and NAc activity, elucidating their role in signaling hedonic valence. The work makes clear that dopamine signaling and general activity in the NAc is exquisitely sensitive to both rewarding and aversive taste stimuli.

Teaching robots right from wrong

Cornelia Dean writes a brief article on people trying to develop intelligent battle robots that can behave more ethically in the battlefield than humans currently can. It focuses on the work of Ronald Arkin at Georgia Tech.

In the heat of battle, their minds clouded by fear, anger or vengefulness, even the best-trained soldiers can act in ways that violate the Geneva Conventions or battlefield rules of engagement. Now some researchers suggest that robots could do better...some of the potential benefits of autonomous fighting robots: For one thing, they can be designed without an instinct for self-preservation and, as a result, no tendency to lash out in fear. They can be built without anger or recklessness, Dr. Arkin wrote, and they can be made invulnerable to what he called “the psychological problem of ‘scenario fulfillment,’ ” which causes people to absorb new information more easily if it agrees with their pre-existing ideas.

Dr. Arkin’s approach involves creating a kind of intellectual landscape in which various kinds of action occur in particular “spaces.” In the landscape of all responses, there is a subspace of lethal responses. That lethal subspace is further divided into spaces for ethical actions, like firing a rocket at an attacking tank, and unethical actions, like firing a rocket at an ambulance....because rules like the Geneva Conventions are based on humane principles, building them into the machine’s mental architecture endows it with a kind of empathy. He added, though, that it would be difficult to design “perceptual algorithms” that could recognize when people were wounded or holding a white flag or otherwise “hors de combat.”

Noel Sharkey, a computer scientist at the University of Sheffield in Britain, has written that this is not a ‘Terminator’-style science fiction but grim reality. He would ban lethal autonomous robots until they demonstrate they will act ethically, a standard he said he believes they are unlikely to meet. Meanwhile, he said, he worries that advocates of the technology will exploit the ethics research to allay political opposition.

Daniel C. Dennett, a philosopher and cognitive scientist at Tufts University:

“If we talk about training a robot to make distinctions that track moral relevance, that’s not beyond the pale at all,” he said. But, he added, letting machines make ethical judgments is “a moral issue that people should think about.”

The Psychology of Transcending the Present

Liberman and Trope suggest an underlying similarity in all of our mental operations that are not dealing with the here and now:

People directly experience only themselves here and now but often consider, evaluate, and plan situations that are removed in time or space, that pertain to others' experiences, and that are hypothetical rather than real. People thus transcend the present and mentally traverse temporal distance, spatial distance, social distance, and hypotheticality. We argue that this is made possible by the human capacity for abstract processing of information. We review research showing that there is considerable similarity in the way people mentally traverse different distances, that the process of abstraction underlies traversing different distances, and that this process guides the way people predict, evaluate, and plan near and distant situations.

Here is one clip from the article on the interrelations among psychological distance dimensions:

Try to complete the sentence "A long time ago, in a ____ place." The tendency to complete it with "far away" rather than with "nearby" reflects not only a literary convention but also an automatic tendency of the human mind. Indeed, people use spatial metaphors to represent time in everyday language and reasoning. More generally, if psychological distance is reflected in different dimensions, then these dimensions should be mentally associated. Remote locations should bring to mind the distant rather than the near future, other people rather than oneself, and unlikely rather than likely events. Initial support for this hypothesis comes from a set of studies in which participants viewed landscape photographs containing an arrow that was pointing to either a proximal or a distal point on the landscape. Each arrow contained a word denoting either psychological proximity (e.g., tomorrow, we, sure) or psychological remoteness (e.g., year, others, maybe) (Figure below). Participants had to respond by pressing one of two keys as quickly and as accurately as possible. In one version of the task, they had to indicate whether the arrow pointed to a proximal or distal location. In another version, they had to identify the word printed in the arrow [Stroop task]. In both versions, participants responded faster to (i.e., processed more efficiently) distance-congruent stimuli (in which the spatially distant arrow contained a word that denoted large temporal distance, large social distance, or low likelihood and the spatially proximal arrow contained words that denoted temporal proximity, social proximity or high likelihood) than to distance-incongruent stimuli (in which spatially distal arrows contained words denoting proximity and spatially proximal arrows contained words denoting remoteness).

Figure: Two examples of incongruent visual stimuli: a word denoting social proximity, "us," located far from the observer, and a word denoting social remoteness, "them," located near the observer. Because spatial distance is associated with temporal distance, social distance, and hypotheticality, participants are slower to indicate the location of the arrow and to identify the word on it with incongruent stimuli than with congruent stimuli "us" located near the observer and "them" located far from the observer.

Superorganisms

Steve Jones writes an interesting review of E.O. Wilson's latest book, a collaboration with Bert Hölldobler: "THE SUPERORGANISM -The Beauty, Elegance, and Strangeness of Insect Societies"

Social insects have often been co-opted as models of human society. The right uses them to celebrate the power of hierarchy, the left that of community. Bees attract the liberal and optimistic (the spirit of the beehive), ants the conservative and the anything but (the city as ant heap).

Hölldobler and Wilson’s central conceit is that a colony is a single animal raised to a higher level. Each insect is a cell, its castes are organs, its queens are its genitals, the wasps that stung me are an equivalent of an immune system. In the same way, the foragers are eyes and ears, and the colony’s rules of development determine its shape and size. The hive has no brain, but the iron laws of cooperation give the impression of planning. Teamwork pays; in a survey of one piece of Amazonian rain forest, social insects accounted for 80 percent of the total biomass, with ants alone weighing four times as much as all its mammals, birds, lizards, snakes and frogs put together. The world holds as much ant flesh as it does that of humans.

A few simple rules produce what appears to be intelligence, but is in fact entirely mindless. Individuals are automatons. An ant stumbles on a tasty item and brings a piece back to the nest, wandering as it does and leaving a trail of scent. A second ant tracks that pathway back to the source, making random swerves of its own. A third, a fourth, and so on do the same, until soon the busy creatures converge on the shortest possible route, marked by a highway of pheromones. This phenomenon has some useful applications for the social animals who study it. Computer scientists fill their machines with virtual ants and task them with finding their way through a maze, leaving a coded signal as they pass until the fastest route emerges. That same logic helps plan efficient phone networks and the best use of the gates at J.F.K. In the phone system each message leaves a digital “pheromone” as it passes through a node, and the fastest track soon emerges. Swarm intelligence does wondrous things.

Neurotech

Virginia Gewin offers a report on the growing neurotechnology industry.

Last year, global neurotechnology industry revenues rose 8.3% to US$130.5 billion, says NeuroInsights, a market-analysis firm based in San Francisco, California. Its Neurotechnology Industry 2008 Report, which profiled 500 public and private companies, divided the industry into three sectors: neuropharmaceuticals, neurodevices and neurodiagnostics.

Medtronic in Minneapolis, Minnesota...is developing deep-brain stimulation devices, the latest ones for epilepsy and depression.

The budding area of neurogenesis research..has prompted drug companies to look to start-ups and academia for talent... the development of small molecules to encourage neurogenesis — in which endogenous stem cells mature into neurons — is a "breakthrough area". Swiss-based drug giant AstraZeneca announced last month that it will collaborate with Columbia University's René Hen to explore novel neurogenesis-related depression and anxiety treatments.