A new chemical fix for chronic depression??

Maybe, for mice. With the results possibly relevant to us. There is evidence, obtained from both post-mortem human brains and from animal experiments, that persistent depression may involve long term chemical changes in gene-protein complexes called chromatin. Covington et al find that chronic social defeat stress in mice causes a transient decrease, followed by a persistent increase, in levels of acetylated histone H3 (a chromatin protein) in the nucleus accumbens, an important limbic brain region. They then find that infusion into this region of inhibitors of the enzyme that removes acetate groups lessens behavioral symptoms of depression and also reverses the effects of chronic defeat stress on global patterns of gene expression in the nucleus accumbens.

Out of Africa

The Sept. 22 issue of P.N.A.S. has a special section of articles on human evolution. The abstract of Ian Tattersall's introductory to this section has a nice summary:

Our species, Homo sapiens, is highly autapomorphic (uniquely derived) among hominids in the structure of its skull and postcranial skeleton. It is also sharply distinguished from other organisms by its unique symbolic mode of cognition. The fossil and archaeological records combine to show fairly clearly that our physical and cognitive attributes both first appeared in Africa, but at different times. Essentially modern bony conformation was established in that continent by the 200–150 Ka range (a dating in good agreement with dates for the origin of H. sapiens derived from modern molecular diversity). The event concerned was apparently short-term because it is essentially unanticipated in the fossil record. In contrast, the first convincing stirrings of symbolic behavior are not currently detectable until (possibly well) after 100 Ka. The radical reorganization of gene expression that underwrote the distinctive physical appearance of H. sapiens was probably also responsible for the neural substrate that permits symbolic cognition. This exaptively acquired potential lay unexploited until it was “discovered” via a cultural stimulus, plausibly the invention of language. Modern humans appear to have definitively exited Africa to populate the rest of the globe only after both their physical and cognitive peculiarities had been acquired within that continent.

Nutrition and Violence

In the Sept. 25 issue of Science John Bohannon describes work of Oxford's Bernard Gesch and others studying prison populations for evidence of links between nutrition and violent behavior. Two previous studies have shown that prisoners given nutritional supplements committed ~35% fewer violent incidences than those given a placebo, and a more ambitious study of over 1,000 prisoners in three U.K. prisons started this spring. The article offers a summary table which I pass on here:

How would you control eight legs?

It's a problem, if you are an octopus, because you have the challenge of controlling eight appendages that can assume an almost limitless number of positions. Zulio et al. (the paper has a neat video) show that the octopus brain takes a very different tack from our own. Instead of having a specific body part controlled by a specific area of the the brain (as in our brains), the control of complex, coordinated movements is consolidated into specific areas of the nervous system. They placed 35 electrodes to micro-stimulate higher motor centers (in the basal lobes)in free moving animals. Low-voltage stimulation of different areas evokes simple responses, such as a change in skin colour or small eyelid movements. Higher voltages elicit more complex responses, such as inking and jet-propelled swimming. Discrete and complex components have no central topographical organization but are distributed over wide regions. They found no stimulation site where movements of a single arm or body part could be elicited.

The Mind and LIfe Institute

Here is the link to download the Autumn 2009 Newsletter of the Mind and Life Institute. It describes the Mind and Life Education and Research Network, a multidisciplinary intellectual forum dedicated to investigating issues at the intersection of mind, brain, education and contemplative practice.

Size matters...

I work out every day in the university gym, where in the shower room it is obvious that the large more macho males subtly (or not so subtly) check out the 'packages' of their shower mates. Here's the payoff in another species, illustrated by Kahn et al.'s study showing that female mate preference in mosquitofish is influenced by size of male genitalia. The tested female preference for males that had had their genitalia considerably reduced in size by surgery compared with those with only a minor reduction (see figure). They found that females spent, on average, around one-and-a-half times longer associating with the better-endowed males. This preference was, however, only expressed when females chose between two large males; for small males, there was no effect of genital size on female association time.

Representative G. holbrooki showing the difference between wild-type (not used in trials) and treatment male gonopodia. (a) Wild-type; (b) minor reduction; (c) major reduction. Scale bar 1 mm.

Watch those shots of booze!

I've always been curious about the attraction that shots of sugar and alcohol (peppermint schnaps, etc.) have for adolescent drinkers. Now we have a possible animal model for this behavior: Rats fed tasty 'jelly shots' containing alcohol during adolescence became bigger risk-takers than teetotaller rats when presented with a lever game designed by Bernstein et. al. When the adult rats were faced with a choice between pressing a lever for a guaranteed two sugar pills or a lever that could give them either nothing or four sugar pills, the individuals exposed to alcohol in adolescence tended to gamble more often. This effect on behavior could still be seen three months after the alcohol was discontinued. The results indicate that the risk-taking behavior is caused by the alcohol. Here is the abstract of the work:

Individuals who abused alcohol at an early age show decision-making impairments. However, the question of whether maladaptive choice constitutes a predisposing factor to, or a consequence resulting from, alcohol exposure remains open. To examine whether a causal link exists between voluntary alcohol consumption during adolescence and adult decision making the present studies used a rodent model. High levels of voluntary alcohol intake were promoted by providing adolescent rats with access to alcohol in a palatable gel matrix under nondeprivation conditions. A probability-discounting instrumental response task offered a choice between large but uncertain rewards and small but certain rewards to assess risk-based choice in adulthood either 3 weeks or 3 months following alcohol exposure. While control animals' performance on this task closely conformed to a predictive model of risk-neutral value matching, rats that consumed high levels of alcohol during adolescence violated this model, demonstrating greater risk preference. Evidence of significant risk bias was still present when choice was assessed 3 months following discontinuation of alcohol access. These findings provide evidence that adolescent alcohol exposure may lead to altered decision making during adulthood and this model offers a promising approach to the investigation of the neurobiological underpinnings of this link.

Acting against our real self interest to preserve our self image

Here is a fascinating bit of game playing from Yamagishi et al. :

In a series of experiments, we demonstrate that certain players of an economic game reject unfair offers even when this behavior increases rather than decreases inequity. A substantial proportion (30–40%, compared with 60–70% in the standard ultimatum game) of those who responded rejected unfair offers even when rejection reduced only their own earnings to 0, while not affecting the earnings of the person who proposed the unfair split (in an impunity game). Furthermore, even when the responders were not able to communicate their anger to the proposers by rejecting unfair offers in a private impunity game, a similar rate of rejection was observed. The rejection of unfair offers that increases inequity cannot be explained by the social preference for inequity aversion or reciprocity; however, it does provide support for the model of emotion as a commitment device. In this view, emotions such as anger or moral disgust lead people to disregard the immediate consequences of their behavior, committing them to behave consistently to preserve integrity and maintain a reputation over time as someone who is reliably committed to this behavior.

Mindblog backlog...

Here is my second offering of links to a few bits of work that I find interesting, but that are so far down my list of potential blog postings that they are unlikely to make it into a regular post, and might be of interest to some MindBlog readers.

Cognitive fitness of cost-efficient brain functional networks

Superior task performance was positively correlated with global cost efficiency of the β-band network (15-30 Hz) and specifically with cost efficiency of nodes in left lateral parietal and frontal areas. These results are consistent with biophysical models highlighting the importance of β-band oscillations for long-distance functional connections in brain networks and with pathophysiological models of schizophrenia as a dysconnection syndrome. More generally, they echo the saying that “less is more”: The information processing performance of a network can be enhanced by a sparse or low-cost configuration with disproportionately high efficiency.

Do we really need vision? How blind people "see" the actions of others.

Our mirror neuron system develops in the absence of sight.

A 35,000 year old flute.

Fragments of ancient flutes reveal that music was well established in Europe by about 40,000 years ago.

Keeping in Touch with One's Self: Multisensory Mechanisms of Self-Consciousness

More from the laboratory that brought you the full body illusion.

Two related papers:

Neural Substrates of Mounting Temporal Expectation

Ready…Go: Amplitude of the fMRI Signal Encodes Expectation of Cue Arrival Time

A new positive psychology website

You might want to check out the launch of a new self help website happiness.com. It has the support of gurus in the happiness field such as Martin Seligman, and offers its own particular set of happiness exercises and plans. It's hard to find fault with the simple exercises and suggestions offered; and indeed, whenever I take the attention space to spend some time doing common exercises in the field, like feeling or expressing gratitude or kindness, savoring small joys, forgiving, avoiding over thinking and social comparison, etc. it lightens me up considerably. However, one of the features of these sites that kind of gets to me is their Pollyanna aura, with the apparent goal of being 100% happy 100% of the time - of making 'sad' just go away....it seems to me that the spice of life is having robust highs and lows. I enjoy my lighter moments and I also savor my basically curmudgeonly nature.

Observing the brain pathway that lowers anxiety

Kim and Whalen publish an interesting study in the Journal of Neuroscience using diffusion tensor imaging to show that the structural integrity, or strength, of a pathway between the prefrontal cortex and the amygdala correlates with lower trait anxiety in individual subjects (the idea being that this pathway allows prefrontal cortex to inhibit amygdala reactivity to anxiety provoking stimuli). The abstract:

Here, we used diffusion tensor imaging (DTI) and showed that the strength of an axonal pathway identified between the amygdala and prefrontal cortex predicted individual differences in trait anxiety. A functional magnetic resonance imaging (fMRI) functional localizer that has been shown to produce reliable amygdala activation was collected in 20 psychiatrically healthy subjects. Voxelwise regression analyses using this fMRI amygdala reactivity as a regressor were performed on fractional anisotropy images derived from DTI. This analysis identified a white matter pathway between the amygdala and ventromedial prefrontal cortex. Individual differences in the structural integrity of this putative amygdala–prefrontal pathway were inversely correlated with trait anxiety levels (i.e., higher pathway strength predicted lower anxiety). More generally, this study illustrates a strategy for combining fMRI and DTI to identify individual differences in structural pathways that predict behavioral outcomes.

A unique area for tool use in human versus monkey brains

Peeters et al. observe an activation in the left inferior parietal lobule when humans observe tool use, absent in monkeys doing the same observation, which they suggest is related to our capacity to understand the causal relationship between tools and the result of their use.

Though other species of primates also use tools, humans appear unique in their capacity to understand the causal relationship between tools and the result of their use. In a comparative fMRI study, we scanned a large cohort of human volunteers and untrained monkeys, as well as two monkeys trained to use tools, while they observed hand actions and actions performed using simple tools. In both species, the observation of an action, regardless of how performed, activated occipitotemporal, intraparietal, and ventral premotor cortex, bilaterally. In humans, the observation of actions done with simple tools yielded an additional, specific activation of a rostral sector of the left inferior parietal lobule (IPL). This latter site was considered human-specific, as it was not observed in monkey IPL for any of the tool videos presented, even after monkeys had become proficient in using a rake or pliers through extensive training. In conclusion, while the observation of a grasping hand activated similar regions in humans and monkeys, an additional specific sector of IPL devoted to tool use has evolved in Homo sapiens, although tool-specific neurons might reside in the monkey grasping regions. These results shed new light on the changes of the hominid brain during evolution.

More on Brain Boosters

Gary Stix has written a review article for the Oct. 2009 issue of the Scientific American titled "Turbocharging the Brain", a topic that has been the subject of several previous mindblog posts. Here are two simple summary figures on effects and risks (click on figure to enlarge):


and on potential new drugs:

Bird brains get even more clever.

New Caledonian crows, already known for clever tool-making in the wild and in the lab, are now shown to be able of using three tools in the correct order to bag a treat. Such sequential tool use has never been observed in any other untrained nonhuman animal. In the wild, the crows (Corvus moneduloides) regularly fashion barbs and hooks from leaves and twigs to extract grubs from holes and crevices. In the new experiments, each of seven crows was given a test tube stuffed with a tasty piece of meat that could be pried out only with a particular stick. To get at the meat, the birds had to do three things in the right order: pick up a short stick, available on the cage floor, and use it to pull a longer stick out of a second test tube; use that stick to extract an even longer stick from a third test tube; and then use this longest stick to get the prize. Four crows were successful. It seems unlikely that they were selecting sticks at random, because they usually swapped sticks for longer ones.

Societal trend of media multitasking is changing our cognitive control

Lin reviews some interesting work of Ophir et al. showing:

...that heavy media multitaskers (HMMs) performed worse on task switching than light media multitaskers (LMMs), likely because of HMMs' reduced ability to filter out interference from irrelevant stimuli and representations in memory. Their findings are surprising in that, intuitively, HMMs should be better at task switching (i.e., multitasking) because they frequently switch between tasks, a habit or expertise (if so) that should have helped them to be better multitaskers (task switchers). However, the findings are also not surprising in that...HMMs tend to be breadth-biased in their behaviors and are inclined to pay attention to a larger scope of information instead of focusing on a particular piece of information. Such a behavior or habit has conditioned them to be less selective when it comes to filtering information and tasks in front of them. In other words, HMMs may have developed a habit of treating all of the information in front of them with equal (or almost equal) amounts of attention instead of focusing their attention steadily on a particular task. As a result, they performed worse than LMMs did when they were asked to focus attention on selective pieces.

Mood elevating endorphine release greater with social than with solitary exercise

The Research Highlights section of the Sept. 17 issue of Nature points to work by Cohen et al.:

Coordinated social activity, such as dancing or team sports, stimulates the brain to release high levels of mood-elevating endorphins that are believed to have a role in social bonding. But how can this be distinguished from the normal release of endorphins during exercise?...Emma Cohen of the University of Oxford, UK, and her colleagues looked at rowers training alone or with teammates on stationary rowing machines. Because measuring endorphins directly would require a spinal tap, the researchers instead used pain tolerance to gauge endorphin release after workouts. They found that rowers had greater increases in pain threshold after operating as a crew than when going solo.

Cohen et al. suggest that enhanced endorphin release from synchronized activity may explain the sense of euphoria experienced in social activities like laughter, music-making, and dancing that are involved in social bonding in humans (and possibly other vertebrates.)

MRI of emotions in a dead fish...

Even though this gem is making the rounds of the blogosphere it is worth pointing to again here. (This reminds me of my grandmother's answer to my "what do the people do here?" question as we were driving through small Texas towns. Her reply: "They take in each other's laundry." )

Bennett et. al. present a hilarious yet serious abstract showing different brain MRI responses as a dead salmon views pictures of people with different emotional expressions. It is a demonstration of the "multiple comparisons problem" - the fact that if you do a lot of different statistical tests, some of them will, just by chance, give interesting results. A multiple comparisons corrections can be applied, but many fMRI publications still report "uncorrected" results.

Will there ever be a "healthy" diet?

Darn.... here I've been religiously avoiding potatoes, pasta, bread, etc in my diet, and now Rosenzweig and his Harvard colleagues find evidence that low carbohydrate diets are linked to atherosclerosis and impaired blood vessel growth. They find that mice placed on a 12-week low-carbohydrate/high-protein diet showed a significant increase in atherosclerosis, a buildup of plaque in the heart’s arteries and a leading cause of heart attack and stroke. The findings also showed that the diet led to an impaired ability to form new blood vessels in tissues deprived of blood flow, as might occur during a heart attack.

Rewards work better than punishment in enhancing cooperation

Rand and colleagues have examined cooperation among 192 participants in a public goods game probing the fundamental tension between the interests of an individual and a group. In more than 50 rounds of interaction, each of four participants in a group would decide how much to contribute toward a common pool that benefited all four equally. Each participant was then able — at a cost to himself or herself — to either reward or punish each of the three other subjects for their contributions to the group, or lack thereof. Here is their abstract:

The public goods game is the classic laboratory paradigm for studying collective action problems. Each participant chooses how much to contribute to a common pool that returns benefits to all participants equally. The ideal outcome occurs if everybody contributes the maximum amount, but the self-interested strategy is not to contribute anything. Most previous studies have found punishment to be more effective than reward for maintaining cooperation in public goods games. The typical design of these studies, however, represses future consequences for today’s actions. In an experimental setting, we compare public goods games followed by punishment, reward, or both in the setting of truly repeated games, in which player identities persist from round to round. We show that reward is as effective as punishment for maintaining public cooperation and leads to higher total earnings. Moreover, when both options are available, reward leads to increased contributions and payoff, whereas punishment has no effect on contributions and leads to lower payoff. We conclude that reward outperforms punishment in repeated public goods games and that human cooperation in such repeated settings is best supported by positive interactions with others.

Friendship networks revealed by cell phone data.

Lazer and colleagues have compared data gathered through self-reporting versus data gathered through cell phone usage to determine whether such information can prove reliable in predicting friendships and job satisfaction. The study followed 94 subjects over the course of nine months.

Data collected from mobile phones have the potential to provide insight into the relational dynamics of individuals. This paper compares observational data from mobile phones with standard self-report survey data. We find that the information from these two data sources is overlapping but distinct. For example, self-reports of physical proximity deviate from mobile phone records depending on the recency and salience of the interactions. We also demonstrate that it is possible to accurately infer 95% of friendships based on the observational data alone, where friend dyads demonstrate distinctive temporal and spatial patterns in their physical proximity and calling patterns. These behavioral patterns, in turn, allow the prediction of individual-level outcomes such as job satisfaction.