Japanese Gardens

This picture from a stroll yesterday in the Morikami Japanese Gardens in Boca Raton, Florida. An iguana is on the lawn to the right of the tree trunk, a heron to its right on the bank, the flat object on the grass to the right of the heron is a water turtle, and the orange spots in the water are Koi. (click on the picture to enlarge).

Our optimism bias - brain correlates

Sharot et al. examine the tendency of most of us to imagine more optimistic outcomes than can be justified by sober appraisal. A moderate amount of optimistic illusion has been related to mental and physical health, and the general idea is that it is adaptive and useful because it motivates us towards future goals. Their abstract, and a figure showing the relevant brain regions:

Humans expect positive events in the future even when there is no evidence to support such expectations. For example, people expect to live longer and be healthier than average, they underestimate their likelihood of getting a divorce, and overestimate their prospects for success on the job market. We examined how the brain generates this pervasive optimism bias. Here we report that this tendency was related specifically to enhanced activation in the amygdala and in the rostral anterior cingulate cortex when imagining positive future events relative to negative ones, suggesting a key role for areas involved in monitoring emotional salience in mediating the optimism bias. These are the same regions that show irregularities in depression, which has been related to pessimism. Across individuals, activity in the rostral anterior cingulate cortex was correlated with trait optimism. The current study highlights how the brain may generate the tendency to engage in the projection of positive future events, suggesting that the effective integration and regulation of emotional and autobiographical information supports the projection of positive future events in healthy individuals, and is related to optimism.

The authors collected functional magnetic resonance imaging (fMRI) data while participants thought of autobiographical events related to a description of a life episode (for example, 'winning an award' or 'the end of a romantic relationship'). The word 'past' or 'future' indicated if they should think of an event that occurred in the past or one that might occur in the future. Trials were classified into positive, negative and neutral according to participants' ratings. They found that future positive events were rated as more positive than past positive events, and were imagined to be closer in temporal proximity then future negative events and all past events. (Click on image to enlarge it)

Impairment of action chains in autism.

When we observe the start of an action sequence that can end in two possible ways (in the figure shown a piece of food is placed in the mouth or in a container on the shoulder) appropriate sympathetic muscle EMG signals are detected at the start of the sequence. Thus, if the sequence will end in food to the mouth, activity is observed in the mouth-opening mylohyoid (MH) muscle at the onset. Rizzolatti and collaborators find that typically developing children show an activation of their MH muscle already when they observe the experimenter's initial motor act, food reaching. This activation reflects their understanding of the final goal of the observed action. In children with autism this action-understanding motor activation is lacking. Further, when typically developing children actually perform the observed action, MH muscle activation is observed at the very beginning of the sequence, while in children with autism, the activation is not observed until immediately before the muscle is actually used.

Figure - Schematic representation of the tasks. (Upper) The individual reaches for a piece of food located on a touch-sensitive plate, grasps it, brings it to the mouth, and finally eats it. (Lower) The individual reaches for a piece of a paper located on the same plate, grasps it, and puts into a container placed on the shoulder.

They suggest that high-functioning autistic children may understand the intentions of others cognitively but lack the mechanism for understanding them experientially because they lack the chains of action-constrained neurons that code specific motor acts (e.g., grasping) according to the final goal of the action in which the motor act is embedded.

Distinguishing true versus illusory memories with brain imaging.

Kim and Cabeza show that true versus illusory memories held with high certainty depend on different neural mechanisms. Here is their abstract and one figure from the paper:

Although memory confidence and accuracy tend to be positively correlated, people sometimes remember with high confidence events that never happened. How can confidence correlate with accuracy but apply also to illusory memories? One possible explanation is that high confidence in veridical versus illusory memories depends on different neural mechanisms. The present study investigated this possibility using functional magnetic resonance imaging and a modified version of the Deese-Roediger-McDermott false-memory paradigm. Participants read short lists of categorized words, and brain activity was measured while they performed a recognition test with confidence rating. The study yielded three main findings. First, compared with low-confidence responses, high-confidence responses were associated with medial temporal lobe (MTL) activity in the case of true recognition but with frontoparietal activity in the case of false recognition. Second, these regions showed significant confidence-by-veridicality interactions. Finally, only MTL regions showed greater activity for high-confidence true recognition than for high-confidence false recognition, and only frontoparietal regions showed greater activity for high-confidence false recognition than for high-confidence true recognition. These findings indicate that confidence in true recognition is mediated primarily by a recollection-related MTL mechanism, whereas confidence in false recognition reflects mainly a familiarity-related frontoparietal mechanism. This account is consistent with the fuzzy trace theory of false recognition. Correlation analyses revealed that MTL and frontoparietal regions play complementary roles during episodic retrieval. In sum, the present study shows that when one focuses exclusively on high-confidence responses, the neural correlates of true and false memory are clearly different.

Figure: Activity within medial temporal lobes (A) was greater for high-confidence true recognition (HC-TR) than for high-confidence false recognition (HC-FR). Activity within a frontoparietal network (B) was greater for high-confidence false recognition than for high-confidence true recognition.

The moment of recognition...

Ploran et al. use fMRI to observe brain activity leading up to recognition of a perceptual object's identity. Here is their abstract, followed by a composite graphic extracted from figures in the paper.

Decision making can be conceptualized as the culmination of an integrative process in which evidence supporting different response options accumulates gradually over time. We used functional magnetic resonance imaging to investigate brain activity leading up to and during decisions about perceptual object identity. Pictures were revealed gradually and subjects signaled the time of recognition (TR) with a button press. We examined the time course of TR-dependent activity to determine how brain regions tracked the timing of recognition. In several occipital regions, activity increased primarily as stimulus information increased, suggesting a role in lower-level sensory processing. In inferior temporal, frontal, and parietal regions, a gradual buildup in activity peaking in correspondence with TR suggested that these regions participated in the accumulation of evidence supporting object identity. In medial frontal cortex, anterior insula/frontal operculum, and thalamus, activity remained near baseline until TR, suggesting a relation to the moment of recognition or the decision itself. The findings dissociate neural processes that function in concert during perceptual recognition decisions.

Composite extracted from figures in paper (click on graphic to enlarge and see labels): From interpolation analyzes, the top row shows brain regions of interest for initial sensory processing, the second row regions active in accumulation, and the bottom row regions active when recognition of the stimulus is signalled.

Drug enhancement of athletic performance - with no drugs!

Given the gnashing of teeth in the sports world over role models outed for their drug use, this bit from an Italian group is fascinating. It turns out that after only a few administrations of a pain killer (morphine), a placebo or sham injection on the day of the athletic event has the same effect as taking the real drug! Does this count as illegal drug use before an athletic performance? Here is the abstract from Benedetti et al.:

The neurobiological investigation of the placebo effect has shown that placebos can activate the endogenous opioid systems in some conditions. So far, the impact of this finding has been within the context of the clinical setting. Here we present an experiment that simulates a sport competition, a situation in which opioids are considered to be illegal drugs. After repeated administrations of morphine in the precompetition training phase, its replacement with a placebo on the day of competition induced an opioid-mediated increase of pain endurance and physical performance, although no illegal drug was administered. The placebo analgesic responses were obtained after two morphine administrations that were separated as long as 1 week from each other. These long time intervals indicate that the pharmacological conditioning procedure has long-lasting effects and that opioid-mediated placebo responses may have practical implications and applications. For example, in the context of the present sport simulation, athletes can be preconditioned with morphine and then a placebo can be given just before competition, thus avoiding administration of the illegal drug on the competition day. However, these morphine-like effects of placebos raise the important question whether opioid-mediated placebo responses are ethically acceptable in sport competitions or whether they have to be considered a doping procedure in all respects.

The instinct to swarm

Groups of social animals whose individual members follow simple sets of rules do surprising things. This NY Times article by Carl Zimmer in the Nov. 13 science section quotes Ian Couzin, a mathematical biologist at Princeton: “No matter how much you look at an individual army ant...you will never get a sense that when you put 1.5 million of them together, they form these bridges and columns. You just cannot know that.” The article notes the simple models that predict swarming behavior by setting the population density that which individuals switch from going their own way to following others. It also describes experiments using human subjects to test Couzin's models.

Many take our brains to be a more massive and complex version of the "hive minds" displayed by groups of bees, ants, birds and fish. Brain modelers assign relatively simple properties to their model neurons and then watch amazing patterns emerge when their whole society of neurons is fired up to interact.

Exercise on the Brain

Aamodt and Wang contribute an Op-Ed piece with the title of this post in the Nov. 8 New York Times. Their main message is that all of the 'brain exercise' programs that are marketed to counter the cognitive decline associated with aging are more expensive, complicated, and vastly less effective than vigorous daily exercise (not to suggest that these are competing alternatives, it is certainly best to do both). They note that while activities like solving puzzles or remembering lists can induce lasting changes in these specialized areas, physical exercise improves “executive function,” the set of abilities that allows you to select behavior that’s appropriate to the situation, inhibit inappropriate behavior and focus on the job at hand in spite of distractions. Executive function includes basic functions like processing speed, response speed and working memory, the type used to remember a house number while walking from the car to a party. They also note studies showing the numerous theraputic effects of exercise, such as delaying both the onset of dementia and the shrinking of the frontal cortex that occurs with age.

A hormone boost to generosity...

Yet another bit of work on the magic hormone, oxytocin, that makes us more affiliative, gentle, and trusting...the abstract from Zak et al. :

Human beings routinely help strangers at costs to themselves. Sometimes the help offered is generous—offering more than the other expects. The proximate mechanisms supporting generosity are not well-understood, but several lines of research suggest a role for empathy. In this study, participants were infused with 40 IU oxytocin (OT) or placebo and engaged in a blinded, one-shot decision on how to split a sum of money with a stranger that could be rejected. Those on OT were 80% more generous than those given a placebo. OT had no effect on a unilateral monetary transfer task dissociating generosity from altruism. OT and altruism together predicted almost half the interpersonal variation in generosity. Notably, OT had twofold larger impact on generosity compared to altruism. This indicates that generosity is associated with both altruism as well as an emotional identification with another person.

Conductors’ Ears and Eyes Stay Equally Alert

Here is an interesting tidbit that makes perfect sense to me as a pianist, from Eric Nagourney reporting in the NY Times on the Society for Neuroscience Meetings:

To concentrate on a difficult task that involves listening, people tend to unconsciously divert their attention from what they are seeing. But music conductors, a new study reports, are not as apt to be distracted in this way....The researchers, who presented their findings at a recent conference of the Society for Neuroscience, used magnetic resonance imaging to compare how 20 conductors and 20 nonmusicians handled complex auditory tasks...The researchers were from Wake Forest University Baptist Medical Center and the University of North Carolina at Greensboro. They were especially interested in learning whether their subjects would continue shifting resources as the demands of listening became more complex, said the lead author, Dr. W. David Hairston of Wake Forest...The volunteers were placed in an M.R.I. scanner and asked to listen to different notes over headphones while keeping their eyes open. As the notes were played closer and closer together, they were asked to say which they heard first...In both groups, activity in the parts of the brain involved with seeing decreased, but as the task became more difficult, only the nonmusicians turned off more of their visual processing...Part of the explanation may lie in the need for conductors to make extensive use of both their eyes and ears, to read the score and “to keep track of who’s playing what,” Dr. Hairston said.

This is Your Brain on Politics

Marco Iacoboni, whose work I have mentioned before, has together with several collaborators performed brain imaging experiments on 20 swing voters who indicate willingness to vote for a candidate from either party in the Nov. 2008 presidential elections. They summarize their findings in an Op-Ed piece in the Nov. 11 New York Times. There is a slide show you might like to watch. While insiders in the imaging business go apoplectic over simplistic interpretations of averaged data taken from a small number of subjects using ambiguous protocols with dubious controls, some correlations do emerge that "make sense." (See these comments on the article as 'junk science'.) For example: anterior cingulate (conflict resolution) associates with Hillary Clinton; or amygdala (anxiety) and insula (disgust) correlates with viewing the words "Democrat" or "Republican" but not "independent". One bit I found interesting: "Barack Obama and John McCain have work to do. The scans taken while subjects viewed the first set of photos and the videos of Mr. McCain and Mr. Obama indicated a notable lack of any powerful reactions, positive or negative."

Slide 2
Photos of Hillary Clinton elicited increased activity in the anterior cingulate cortex, a part of the brain that processes conflicting impulses, in swing voters who reported having an unfavorable opinion of her.

Society for Neuroscience meeting: news from the front lines

You might like to check out the Society for Neuroscience website, which offers very accessible information for general public, press, and educators. The site contains links to these topics from the recent annual meeting:

* Antidepressant Drugs, Exercise, Young Age, Even Food Intake, Frequency, and Type, Affect Generation of New Brain Cells

* Research Sheds Light on Brain Differences in Adolescents, Understanding their Impulsive, Risk-Taking Behavior

* Training, Sensory Substitution, Thought-Reading Computers, Sleep, and Molecular Imaging Advance Stroke Research

* Thoughts, Not Arms and Hands, Can Operate Machines: New Devices May Soon Improve Lives or Physically Handicapped

* New Research Explores Dietary Effects on Amyloid in Search for Ways To Prevent, Treat Alzheimer's Disease

* New Studies Find Potential Biomarker for PTSD, Make Gains in Understanding Disorder and Why it is Difficult To Treat

The brain in glorious color - "Brainbows"

Benedict Carey describes the work of Harvard researchers:

The scientists bred mice so their brain cells had genetic inserts containing genes for three colors of fluorescent protein, red, green and blue. They prompted each insert to randomly express one color, using a genetic trigger. Because there were multiple copies of the three-gene insert in each cell, the cell itself expressed a random mixture of the three colors, some 90 shades in all. What emerged was a kind of beaded rainbow belt of neurons, with the fluorescent glow radiating out through each cell’s neural branches. The researchers called the technique “Brainbow.”

Scientists can use this technique in animals, whose brain systems work in ways similar to those of humans, to see exactly where each cell begins and ends, both within the brain and out through the spine and the limbs — and what happens in between.

“I take a view that this is like the Hubble telescope,” said Dr. Jeff Lichtman, a professor of molecular and cellular biology at Harvard who is the paper’s senior author. “We’ve never been able to look at the brain this way before. Why not just start looking and see what we observe?”

Rationalizing our choices - an early evolutionary origin

When we humans make a choice, we protect our self esteem by rationalizing that it was the correct one, even in the face of evidence to the contrary. It turns out Capuchin monkeys do the same thing. In a kind of "why didn't someone think of trying this before?" experiment, a group of Yale psychologists offered the monkeys several different colors of M&M candies. Once a monkey was observed to show an equal preference for three colors of M&M’s — say, red, blue and green — he was given a choice between two of them. If he chose red over blue, his preference changed and he downgraded blue. When he was subsequently given a choice between blue and green, it was no longer an even contest — he was now much more likely to reject the blue. Thus the monkeys are dealing with cognitive dissonance ('should I choose the blue or the green?') by downgrading or eliminating one of the options. They performed a similar experiment with little children, obtaining similar results. The fact that children and primates show the same behavior as adults suggests that this rationalization behavior is largely unconscious, and may have appeared in evolution earlier than previously thought.

MindBlog's winter home...

Internet is now up and running at the Fort Lauderdale condo, in spite of Comcast.

Susceptibility and Resistance to Social Defeat: Molecular Correlates

The research highlights section of the Nov. 1 issue of Nature points to an interesting article from Nester's group on a strain of mice susceptible to social stress. A description excerpted from a review by Hymen:

...mice are exposed to 10 bouts of social defeat in which c57bl/6 test mice are forced to intrude into space occupied by mice of a larger and more aggressive strain, leading to subordination of the test mice. Following this repeated stress, a subset of mice develop significant avoidance of social contact with mice of the same strain and exhibit other signs that are reminiscent of symptoms of human depression, including weight loss and loss of hedonic (pleasure) responses to sucrose. A strength of the social defeat stress model is that, at least in this mouse strain, the stressor convincingly separates the mice into two groups, a group that the authors designate “Susceptible,” which develop social avoidance, and a group described as “Unsusceptible,” which continue to interact with other mice at the same rate as never stressed controls. The model has other strengths. Repeated social defeat would appear to be a good model for some adverse human experience. Moreover, the traits that emerge in susceptible mice reverse only with chronic antidepressant treatment, which mirrors the requirements for treatment of depression and anxiety disorders with these drugs in humans.

Figure 1. Neural Circuits Regulating Responses to Social Defeat

The mesolimbic dopamine pathway comprises a projection from the ventral tegmental area (VTA) of the midbrain to the nucleus accumbens (NAc) and to other forebrain structure, such as the amygdala and prefrontal cortex (PFC). These dopamine projections, which act as the neural substrates of the rewarding properties of food, mating behaviors, and addictive drugs, are now shown by Krishnan et al. (2007) to mediate the response of mice to social defeat. In mice susceptible to social defeat, expression of brain-derived neurotrophic factor (BDNF) increases in the VTA. The NAc is the recipient of increased BDNF release and shows enhanced downstream signaling via the BDNF receptor.

Single cells in monkey brain trained to associate numbers with their symbols

An interesting study from Diester and Nieder showing single nerve cell activity that might be the primitive cognitive precursor that ultimately has given rise to symbolic thinking in linguistic humans. Their abstract:

The utilization of symbols such as words and numbers as mental tools endows humans with unrivalled cognitive flexibility. In the number domain, a fundamental first step for the acquisition of numerical symbols is the semantic association of signs with cardinalities. We explored the primitives of such a semantic mapping process by recording single-cell activity in the monkey prefrontal and parietal cortices, brain structures critically involved in numerical cognition. Monkeys were trained to associate visual shapes with varying numbers of items in a matching task. After this long-term learning process, we found that the responses of many prefrontal neurons to the visual shapes reflected the associated numerical value in a behaviorally relevant way. In contrast, such association neurons were rarely found in the parietal lobe. These findings suggest a cardinal role of the prefrontal cortex in establishing semantic associations between signs and abstract categories, a cognitive precursor that may ultimately give rise to symbolic thinking in linguistic humans.

Coevolution of Parochial Altruism and War

Choi and Bowles offer an interesting game theoretic analysis that suggests why the combination of loyalty towards one's own group and hostility towards outsiders seems to be such a fixed constant of human societies. Here is their abstract:

Altruism—benefiting fellow group members at a cost to oneself—and parochialism—hostility toward individuals not of one's own ethnic, racial, or other group—are common human behaviors. The intersection of the two—which we term "parochial altruism"—is puzzling from an evolutionary perspective because altruistic or parochial behavior reduces one's payoffs by comparison to what one would gain by eschewing these behaviors. But parochial altruism could have evolved if parochialism promoted intergroup hostilities and the combination of altruism and parochialism contributed to success in these conflicts. Our game-theoretic analysis and agent-based simulations show that under conditions likely to have been experienced by late Pleistocene and early Holocene humans, neither parochialism nor altruism would have been viable singly, but by promoting group conflict, they could have evolved jointly.

A review by Arrow explains the simulation:

In Choi and Bowles' simulation, 20 small groups of agents interact over thousands of generations. Agents have two genes, each with two alleles. They are either tolerant (T) or parochial (P) and either altruistic (A) or not (N). Offspring inherit their parents'traits, with occasional random mutations. Altruists help fellow group members at a personal cost; non-altruists do not. Tolerant agents have lucrative exchanges with outsiders; parochial agents do not. A high proportion of parochials in groups restricts trading opportunities for all....The societies that evolve are stable in two conditions: when either selfish traders (TN) or generous warriors (PA) are the dominant type. A few PN bullies and even fewer TA philanthropists can coexist within trader or warrior regimes. The trading regime is peaceful. Standoffs and wars are more common in the warrior regime, but even infrequent war--10 to 20% of encounters--can maintain high levels of parochial altruism. Similar findings for the impact of intermittent war on the evolution of heroism (6) suggest that war need not be "constant" to act as a powerful selective force...The convergence of altruism and parochialism in Choi and Bowles' simulation is consistent with links between the two found in behavioral studies. Selfish choices in social dilemma experiments, for example, diminish markedly when the game is embedded in an intergroup context.

The Undiscovered Planet

Harvard Magazine has an outstanding article with nice graphics on the astounding diversity of microbial life.

In terms of gene content, humans and potatoes are more closely related than these two bacteria are to each other—one measure of bacterial diversity. On the left, Vibrio cholerae; on the right, Mycobacterium tuberculosis.


The anthropocentric five-kingdom system classified all unicellular organisms lacking nuclei (archaea and bacteria) as Monera. The nucleated eukaryotes comprising plants, animals, and fungi were thought to represent the bulk of biological diversity. All other nucleated eukaryotes were grouped in a grab-bag classification known as Protista.


The modern “tree of life,” based on genetic analysis, shows that the bulk of Earth’s biodiversity resides among the Archaea, Bacteria, and that portion of the Eukarya that does not include plants, animals, and fungi.

Decision, Decisions

A recent Science Magazine issue has a special section on the underlying processes of decision-making. Here is Peter Stern's introduction to the section:

Who hasn't agonized over a major decision in life, whether to accept a job offer, move house, or perhaps switch research fields? We are confronted with a multitude of decisions on a daily basis. Many decisions are trivial and can be dealt with in seconds. However, others may have wider ramifications and can be excruciatingly complicated. In the past few years, our understanding of the underlying processes of decision-making has progressed markedly. This neuroscience special issue highlights some of the most exciting developments in this area.

Koechlin and Hyafil review recent experimental studies that provide new insights into the function and connectivity of the anterior prefrontal cortex, which forms the apex of the executive system underlying decision-making. The authors propose an original model of the anterior prefrontal function and provide a theoretical framework for addressing major unresolved issues and guiding future research on decision-making and higher cognition.

Human beings are highly social animals. Many of our decisions make sense only within a social environment. Sanfey outlines the advantages that can be gained by combining tasks and formal mathematical models from game theory with modern neuroimaging methods to characterize the processes that underlie social decision-making. He also summarizes recent research that offers good examples of how this neuroeconomic approach has already begun to illuminate our knowledge of this process.

Sometimes things can also go wrong in this complicated and well-balanced interplay between several brain regions. Paulus proposes that decision-making in psychiatric populations cannot be viewed simply as an alteration of the preference structure or the way individuals experience the outcome of the decision. Instead, it must be understood from the homeostatic balance perspective of the individual. Increased risk-taking behavior in drug addicts, for example, although maladaptive in the generic sense, may actually be adaptive for the substance user in a complex, highly unpredictable environment while attempting to respond to internal urges and cravings.

Decision theory has boomed in the past decade. Körding gives an overview of how decision theory, including normative/Bayesian approaches, can lead us to better understand the functions of the nervous system.

Mozart vs. James Bond

This is a hoot, if you are in for a moment of comic relief.

A Ramachandran lecture...

In this excellent and engaging talk, Vilayanur Ramachandran discusses how brain damage can reveal the connection between internal structures of the brain and corresponding functions of the mind. Focus is on phantom limb pain, synesthesia (when people hear color or smell sounds), and the Capgras delusion (when brain-damaged people believe their closest friends and family have been replaced with imposters.)

Thinking like a genius

Here is a stimulating stumble.

MindBlog on the road

Congress Avenue, Austin Texas
I drove from Madison, WI to Austin, Texas this past weekend, to visit my son and his wife. They now live in the family house I where I grew up. Tomorrow I hit the road again to drive to Ft. Lauderdale, MindBlog's winter home. The timing turns out to have been perfect, it is 24 degrees fahrenheit with light snow flurries in Madison right now .

Blog postings might be a bit flakey this week.

Drug craving? - Just zap your insula!

An important factor that contributes to drug-seeking in addicted individuals is the negative feelings that result from abstinence. Such mood states are monitored by the interoceptive sensory system, and particularly by a brain area called the insular cortex, known to process emotional information. Thus this abstract from Contreras et al. is of interest:

Addiction profoundly alters motivational circuits so that drugs become powerful reinforcers of behavior. The interoceptive system continuously updates homeostatic and emotional information that are important elements in motivational decisions. We tested the idea that interoceptive information is essential in drug craving and in the behavioral signs of malaise. We inactivated the primary interoceptive cortex in amphetamine-experienced rats, which prevented the urge to seek amphetamine in a place preference task. Interoceptive insula inactivation also blunted the signs of malaise induced by acute lithium administration. Drug-seeking and malaise both induced Fos expression, a marker of neuronal activation, in the insula. We conclude that the insular cortex is a key structure in the perception of bodily needs that provides direction to motivated behaviors.

The therapeutic intervention was an injection of 2% lidocaine (a sodium channel blocker to inhibit nerve activity) into the left and right insula to cause a transient shutdown of insular nerve activity (injecting adjacent cortex was not effective). Although this is a sledgehammer approach with possible dire side effects, it suggests that therapeutic interventions in the insula may help to alleviate drug cravings, .

Music and Dancing

Daniel Levitin has offered this brief essay in the New York Times Op-Ed section.

Less SAD with more sun and serotonin

Welberg offers a summary and review of work by Willeit et al. on the role of serotonin, and a serotonin transporter, in seasonal affective disorder. Here is an portion of the review:

Short, dark winter days put most of us in a gloomy mood, but in people with seasonal affective disorder (SAD), they can cause severe clinical depression. Fortunately, this depression can be treated with bright-light therapy (BLT), and it disappears altogether in summer. Willeit et al. now show that these changes in mood are associated with alterations in the efficiency of the serotonin (5-hydroxytryptamine) transporter (5-HTT) in the patients' blood platelets.

One theory of depression posits that impaired functioning of monoamine neurotransmitters, such as serotonin, causes the disorder, but it is unknown how this impairment might arise. Serotonin levels in the synapse are controlled by the 5-HTT, and Willeit and colleagues therefore investigated whether alterations in 5-HTT functioning might underlie depression in SAD.

The authors compared people with SAD with healthy volunteers, and assessed 5-HTT functioning in winter, after 4 weeks of BLT and in summer. They did this by measuring 5-HTT-mediated inward and outward transport in blood platelets (which are easily obtainable). In winter, both inward transport rate and outward transport were enhanced in the platelets of SAD patients compared with healthy controls. Importantly, these differences in platelet 5-HTT functioning disappeared after 4 weeks of BLT and were absent in summer. The number of 5-HTTs and their affinity for serotonin did not change with BLT or with the seasons, indicating that the increased 5-HTT inward transport that was found in SAD patients was due to increased efficiency of the transporter.

The authors also assessed the patients' depression levels at the three time points, using a structured interview. They found that post-treatment, both inward transport rate and outward transport correlated with depression scores in SAD patients. Moreover, patients whose depression did not decrease after treatment did not show a change in 5-HTT-mediated outward transport after treatment.

Are we having fun?

This is an engaging bit of fluff, be happy! (if the Strauss waltz repeated in a loop doesn't drive you crazy.)

Short-term meditation training improves attention and self-regulation

An interesting study from Tang et al. showing that even short term meditation training can influence attention and self-regulation. The integrative meditation method used:

...stresses no effort to control thoughts, but instead a state of restful alertness that allows a high degree of awareness of body, breathing, and external instructions from a compact disc. It stresses a balanced state of relaxation while focusing attention. Thought control is achieved gradually through posture and relaxation, body–mind harmony, and balance with the help of the coach rather than by making the trainee attempt an internal struggle to control thoughts in accordance with instruction.

Their abstract:

Recent studies suggest that months to years of intensive and systematic meditation training can improve attention. However, the lengthy training required has made it difficult to use random assignment of participants to conditions to confirm these findings. This article shows that a group randomly assigned to 5 days of meditation practice with the integrative body–mind training method shows significantly better attention and control of stress than a similarly chosen control group given relaxation training. The training method comes from traditional Chinese medicine and incorporates aspects of other meditation and mindfulness training. Compared with the control group, the experimental group of 40 undergraduate Chinese students given 5 days of 20-min integrative training showed greater improvement in conflict scores on the Attention Network Test, lower anxiety, depression, anger, and fatigue, and higher vigor on the Profile of Mood States scale, a significant decrease in stress-related cortisol, and an increase in immunoreactivity. These results provide a convenient method for studying the influence of meditation training by using experimental and control methods similar to those used to test drugs or other interventions.

Another window into the minds of chimps and humans

Rilling et al. compare resting-state brain activity in humans and chimpanzees:

In humans, the wakeful resting condition is characterized by a default mode of brain function involving high levels of activity within a functionally connected network of brain regions. This network has recently been implicated in mental self-projection into the past, the future, or another individual's perspective. Here we use [18F]-fluorodeoxyglucose positron emission tomography imaging to assess resting-state brain activity in our closest living relative, the chimpanzee, as a potential window onto their mental world and compare these results with those of a human sample. We find that, like humans, chimpanzees show high levels of activity within default mode areas, including medial prefrontal and medial parietal cortex. Chimpanzees differ from our human sample in showing higher levels of activity in ventromedial prefrontal cortex and lower levels of activity in left-sided cortical areas involved in language and conceptual processing in humans. Our results raise the possibility that the resting state of chimpanzees involves emotionally laden episodic memory retrieval and some level of mental self-projection, albeit in the absence of language and conceptual processing.

Our Brains on Music, and Musicophilia

Steven Pinker has called music useless, with no adaptive value. Oliver Sacks and Daniel Levitin beg to differ. I'm currently reading and enjoying Oliver Sacks' new book: Musicophilia: Tales of Music and the Brain. I'm linking you to a review of this book by Laura Garwin in the current issue of Nature that notes that our brains seem to be finely tuned to music, and asks of what use are our musical powers and passions? She also reviews Levitin's "This is Your Brain on Music: Understanding a Human Obsession." I also thoroughly enjoyed reading this book this past spring, it has a very accessible introduction of the fundamentals of music structure and brain mechanisms associated with music processing.

The hash realities

Murray et al. offer an interesting history and analysis of Cannabis use, with several interesting graphics (PDF here):

Cannabis has been known for at least 4,000 years to have profound effects on the mind — effects that have provoked dramatically divergent attitudes towards it. Some societies have regarded cannabis as a sacred boon for mankind that offers respite from the tribulations of everyday life, whereas others have demonized it as inevitably leading to 'reefer madness'. The debate between the protagonists and prohibitionists has recently been re-ignited, but unfortunately this debate continues mainly in ignorance of our new understanding of the effects of cannabis on the brain and of studies that have quantified the extent of the risks of long-term use.

A Consciousness Debate

Christof Koch and Susan Greenfield offer a written version of their Oxford University Debate in the summer of 2006 in the Oct. 2007 issue of Scientific American. While they make a point of contrasting their models of the neuronal correlates of consciousness, I think a blending of the two may most closely approach the real situation.

What happens in your brain when you see a dog, hear a voice, suddenly feel sad or have any other subjective experience?

KOCH'S MODEL
A coalition of pyramidal neurons linking the back and front of the cortex fires in a unique way. Different coalitions activate to represent different stimuli from the senses (left). In a mouse cortex (right) these pyramidal cells (green) lie in brain layer 5, surrounded by nonneuronal cells (blue).


GREENFIELD'S MODEL
Neurons across the brain fire in synchrony (green) and prevail until a second stimulus prompts a different assembly to arise (orange). Various assemblies coalesce and disband moment to moment, while incorporating feedback from the body. In a rat brain (bottom), an assembly in the cortex forms (a, b), peaks (c), then decays (d) within 0.35 second after the thalamus is electrically stimulated.

Christof Koch is professor of cognitive and behavioral biology at the California Institute of Technology, where he teaches and has conducted research on the neuronal basis of visual attention and consciousness for more than two decades.

Susan Greenfield is professor of pharmacology at the University of Oxford, director of the Royal Institution of Great Britain and member of the British Parliament's House of Lords. Her research focuses on novel brain mechanisms, including those underlying neurodegenerative diseases.

A new consiousness and philosophy of mind bibliography

David Chalmers and David Bourget are offering a more extensive online service, outlined in this message from ASSC (Assoc. for Sci.Stud. Cons.):

We are pleased to announce the launch of MindPapers, a new website
with a bibliography covering around 18000 published papers and online
papers in the philosophy of mind and the science of consciousness.
This site grew out of a combination of David Chalmers' bibliography in
philosophy of mind and his page of online papers on consciousness, but
it is much larger and has many new capacities, programmed by David
Bourget. The site address is:

http://consc.net/mindpapers/

There is also a separate front end for "Online Papers on
Consciousness". Where MindPapers now combines both offline published
papers and online papers from free and commercial sites, Online Papers
on Consciousness is devoted to free online papers (currently around
4700). It is based on the same database as MindPapers, but is
organized in a way to emphasize issues concerning consciousness and
cognitive science rather than the philosophy of mind. The address is

http://consc.net/online/

The MindPapers database contains 2773 papers on the philosophy of
consciousness (under 59 topics and subtopics) and 3917 papers on the
science of consciousness (under 71 topics and subtopics), as well as
thousands of papers on such related topics as perception,
intentionality, the philosophy of AI, and the philosophy of cognitive
science.

Capacities include (i) links and citation information throughout, (ii)
flexible navigation, display, and search options, (iii) the ability to
submit and edit entries, (iv) the capacity for automated off-campus
proxy access to commercial sites, and (v) a wealth of statistical
information.

We encourage everyone to try these sites to submit any relevant
material that we are missing (for a start, try searching on your own
name). There are tools on the site for submitting entries, as well as
for correcting entries and notifying us of any bugs and suggestions.

--David Chalmers and David Bourget
chalmers@anu.edu.au; david.bourget@anu.edu.au

Sleep deprivation diminishes recall of neutral and positive, but not of negative, events.

We remember emotional events, particularly negative ones, better than neutral events. Sterpenich et al. show that while consolidation of neutral and posititive memories is diminished by sleep deprivation, recall of negative events is less compromised. They show that after sleep deprivation, recollection of negative, potentially dangerous, memories recruits an alternate amygdalo-cortical network, which would keep track of emotional information despite sleep deprivation. Here is their description of the work:

Declarative memories, which can be consciously and verbally retrieved, are initially critically dependent on the hippocampus. However, reliable retrieval of long-term memory depends on a process of consolidation, which partly occurs during sleep, when memories are thought to be progressively transferred to long-term cortical stores. Because people tend to remember emotional memories better than neutral ones, we wondered whether the emotional significance of a memory would enhance its consolidation in a sleep-dependent manner. During a first session, participants viewed pictures with neutral and emotional content without realizing that their memory of the pictures and their content would be tested later (called incidental encoding). Three days later, during a functional MRI scanning session, subjects indicated whether they recognized previously viewed and new pictures. Half of the subjects were totally sleep deprived during the first post-encoding night, but all subjects slept as usual during the second and third post-encoding nights. We show here that the recollection of emotional stimuli elicited larger responses in the hippocampus and various cortical areas in the well-rested group than in the sleep-deprived group, suggesting that emotional significance boosts memory consolidation of the information during sleep. Interestingly, in sleep-deprived subjects, recollection of negative items recruited another network including the amygdala, as if an alternate consolidation process allowed them to keep track of negative, potentially dangerous, information despite the cognitive aftermath of sleep deprivation.

Biology and Health Inequality

PLoS Biology has ventured beyond its usual fare to publish several articles focusing on poverty, human development, and the environment. This article is from Eric Brunner. He points out several studies that demonstrate a direct psychosocial pathway to disease. It's precis: "Intriguing parallels between civil servant and nonhuman primate hierarchies suggest that highly stratified societies foster health inequalities. Determining how social differences translate into chronic disease remains a challenge, but neuroendocrine pathways appear to play a role."

Silent Minds

I want to point you to an excellent article by Jerome Groopman, with the title of this post, that appeared in a recent New Yorker Magazine. It describes recent work showing that brain imaging of some vegetative patients reveals responses to faces, and other visual and auditory inputs, that are indistinguishable from those of normal subjects (note: there are approximately 35,000 Americans in a vegetative state and another 280,000 in a minimally conscious state). Responses during various mental tasks, such as resolving ambiguous sentences or imagining playing a tennis game, can also be normal. This shows that an assumption held by doctors for decades - that vegetative patients lack capacity for conscious thought - is incorrect. Other vegetative patients (such as Terri Schiavo), in contrast, can show almost no cortical activity.

This all suggests a better medical definition of consciousness is required - such as the ability to report to ourselves or others the content of the representations in our brains, to sustain these representations over time and broadcast them broadly within the brain.

Evolution - with feeling....

A recent issue of American Scientist has a review by Robert Pennock of two books that attempt to show that a mechanistic Darwinian view of the world does not have to lead to a nihilistic ennui, but rather can satisfy our need to feel richness, purpose, and meaning.

With the familiar references to the "uncaring" Darwinian struggle, and the "mechanical" and "pitiless" action of natural selection, evolutionary biology has long been the obvious whipping boy for those who are uncomfortable with scientific naturalism. It is not just fundamentalist religious beliefs that motivate creationists' attacks on evolution; they are also driven by a deep existential angst—a fear that evolution renders the world pointless, emptying it of purpose, meaning and morality.

In "Darwin Loves You:Natural Selection and the Re-enchantment of the World" George Levine argues that evolution

if properly portrayed, is not only perfectly compatible with meaningfulness but provides a new basis for it...He makes the important point that at the same time that evolution pulls the rug out from under anthropocentrism (which is not only a smug but ultimately a dangerous attitude), it provides a foundation for a justifiable form of anthropomorphism. Darwin showed that humans are not the apex of creation but are one with the rest of the biological world, related to all living things through our common ancestors. This discovery allows us to find common ground with other animals without denigrating our humanness, Levine argues, permitting us to legitimately attribute human characteristics (albeit in simpler or incipient forms) to them. This provides an avenue to the re-enchantment of the world, for it shows we are not wrong to find in it a recognizably human notion of meaningfulness. It is wrong to see nature as cold and unfeeling; for those who understand evolutionary processes and relationships, the biological world becomes a warm and caring network of mutual interactions that are suffused with meaning. Levine is a romantic, but not a naive one; he does not close his eyes to those aspects of nature that are "red in tooth and claw," but shows how these need not negate the positive vision.

In "Evolution for Everyone: How Darwin's Theory Can Change the Way We Think about Our Lives" David Sloan Wilson, in the service of finding harmony between evolution and religion:

...discusses some of the evidence for his evolutionary hypothesis that religions are adaptive at the group level, providing practical benefits relating to the specific conditions the group is confronted with...Given the central importance of evolution in biology, the most extraordinary thing about the public's view, Wilson points out, is not that 50 percent don't believe it, but that nearly 100 percent haven't connected it to anything of importance in their lives. One of Wilson's chief goals—one he accomplishes admirably—is to demonstrate the relevance and value of evolutionary biology not just to scientists but to ordinary people. In story after engaging story, he conveys not only the sweep and the power of evolutionary thinking but the grandeur, as Darwin put it, of this view of life. By the end of the book, the reader understands Wilson's metaphor that evolution is an artist that has helped fashion the sculpture that is the living world.

The Outsourced Brain

I can't resist passing on this clever NY Times Op-Ed piece by David Brooks - on the subject of the dissolution of our individual intelligences into the mush of the infosphere.

Different takes on the social brain.

Gobbini et al. show that different types of mentalizing engage different brain regions. The abstract and a summary figure:

We compared two tasks that are widely used in research on mentalizing—false belief stories and animations of rigid geometric shapes that depict social interactions—to investigate whether the neural systems that mediate the representation of others' mental states are consistent across these tasks. Whereas false belief stories activated primarily the anterior paracingulate cortex (APC), the posterior cingulate cortex/precuneus (PCC/PC), and the temporo-parietal junction (TPJ)—components of the distributed neural system for theory of mind (ToM)—the social animations activated an extensive region along nearly the full extent of the superior temporal sulcus, including a locus in the posterior superior temporal sulcus (pSTS), as well as the frontal operculum and inferior parietal lobule (IPL)—components of the distributed neural system for action understanding—and the fusiform gyrus. These results suggest that the representation of covert mental states that may predict behavior and the representation of intentions that are implied by perceived actions involve distinct neural systems. These results show that the TPJ and the pSTS play dissociable roles in mentalizing and are parts of different distributed neural systems. Because the social animations do not depict articulated body movements, these results also highlight that the perception of the kinematics of actions is not necessary to activate the mirror neuron system, suggesting that this system plays a general role in the representation of intentions and goals of actions. Furthermore, these results suggest that the fusiform gyrus plays a general role in the representation of visual stimuli that signify agency, independent of visual form.

Figure - Locations of loci of activations associated with ToM, social animation, and biological motion tasks, projected onto the left and right lateral surfaces of the brain.

Brain changes after rehabilitation of congenital prosopagnosia

Another article on faces...Degutis et al. show MRI changes correlating with a recovery of enhanced amplitude of the N170 ERP (electroencephalogram event related potential)component in response to faces compared to objects after training of a subject with congenital prosopagnosia (face blindness).

We used functional magnetic resonance imaging (fMRI) and electroencephalography (EEG) to measure neural changes associated with training configural processing in congenital prosopagnosia, a condition in which face identification abilities are not properly developed in the absence of brain injury or visual problems. We designed a task that required discriminating faces by their spatial configuration and, after extensive training, prosopagnosic MZ significantly improved at face identification. Event-related potential results revealed that although the N170 was not selective for faces before training, its selectivity after training was normal. fMRI demonstrated increased functional connectivity between ventral occipital temporal face-selective regions (right occipital face area and right fusiform face area) that accompanied improvement in face recognition. Several other regions showed fMRI activity changes with training; the majority of these regions increased connectivity with face-selective regions. Together, the neural mechanisms associated with face recognition improvements involved strengthening early face-selective mechanisms and increased coordination between face-selective and nonselective regions, particularly in the right hemisphere.

The male chill-out after sex: role for brain oxytocin

Here is an intriguing account from Waldherr and Neumann:

Sexual activity and mating are accompanied by a high level of arousal, whereas anecdotal and experimental evidence demonstrate that sedation and calmness are common phenomena in the postcoital period in humans. These remarkable behavioral consequences of sexual activity contribute to a general feeling of well being, but underlying neurobiological mechanisms are largely unknown. Here, we demonstrate that sexual activity and mating with a receptive female reduce the level of anxiety and increase risk-taking behavior in male rats for several hours. The neuropeptide oxytocin has been shown to exert multiple functions in male and female reproduction, and to play a key role in the regulation of emotionality after its peripheral and central release, respectively. In the present study, we reveal that oxytocin is released within the brain, specifically within the hypothalamic paraventricular nucleus, of male rats during mating with a receptive female. Furthermore, blockade of the activated brain oxytocin system by central administration of an oxytocin receptor antagonist immediately after mating prevents the anxiolytic effect of mating, while having no effect in nonmated males. These findings provide direct evidence for an essential role of an activated brain oxytocin system mediating the anxiolytic effect of mating in males.

It's in the Eyes!

Another curious bit on our brain's specialization for recognizing faces, noting the central role of the eyes. The abstract and a figure:

Unlike most other objects that are processed analytically, faces are processed configurally. This configural processing is reflected early in visual processing following face inversion and contrast reversal, as an increase in the N170 amplitude, a scalp-recorded event-related potential. Here, we show that these face-specific effects are mediated by the eye region. That is, they occurred only when the eyes were present, but not when eyes were removed from the face. The N170 recorded to inverted and negative faces likely reflects the processing of the eyes. We propose a neural model of face processing in which face- and eye-selective neurons situated in the superior temporal sulcus region of the human brain respond differently to the face configuration and to the eyes depending on the face context. This dynamic response modulation accounts for the N170 variations reported in the literature. The eyes may be central to what makes faces so special.

Figure - Simplified neural model of early face processing. Three sources are simultaneously active around 170 msec poststimulus onset. One source in the superior temporal sulcus (STS) region with a radial orientation generates the ERP N170 component. The combination of tangential sources in the fusiform gyrus (FG) and middle occipital gyrus (MOG) generates the MEG M170. The dynamic response modulation of eye- and face-selective neurons within the STS accounts for inversion and CR effects on the face N170 amplitude and for the other existing ERP data on the N170. The + signs represent the amount of activation of the neurons. The absence of + signs signifies that the neurons are not responding.

Our visual system is tuned to animals.

New et al. argue that the human attention system evolved category-specific selection criteria to monitor animals (including humans) in the environment. Ohman gives a nice commentary that puts the work in perspective (PDF here) Below is the abstract and a figure from New et.al. (PDF of article here):

Visual attention mechanisms are known to select information to process based on current goals, personal relevance, and lower-level features. Here we present evidence that human visual attention also includes a high-level category-specialized system that monitors animals in an ongoing manner. Exposed to alternations between complex natural scenes and duplicates with a single change (a change-detection paradigm), subjects are substantially faster and more accurate at detecting changes in animals relative to changes in all tested categories of inanimate objects, even vehicles, which they have been trained for years to monitor for sudden life-or-death changes in trajectory. This animate monitoring bias could not be accounted for by differences in lower-level visual characteristics, how interesting the target objects were, experience, or expertise, implicating mechanisms that evolved to direct attention differentially to objects by virtue of their membership in ancestrally important categories, regardless of their current utility.

Sample stimuli with targets circled. Although they are small (measured in pixels), peripheral, and blend into the background, the human (A) and elephant (E) were detected 100% of the time, and the hit rate for the tiny pigeon (B) was 91%. In contrast, average hit rates were 76% for the silo (C) and 67% for the high-contrast mug in the foreground (F), yet both are substantially larger in pixels than the elephant and pigeon. The simple comparison between the elephant and the minivan (D) is equally instructive. They occur in a similar visual background, yet changes to the high-contrast red minivan were detected only 72% of the time (compared with the smaller low-contrast elephant's 100% detection rate).

Brain location of verbal information storage varies between people

A group at Wisconsin has made the interesting observation that group averaged analyses of the sort frequently reported in brain imaging studies may give misleading results if the brain location of the process being studied varies from one individual to the next. Here is their abstract:

What are the precise brain regions supporting the short-term retention of verbal information? A previous functional magnetic resonance imaging (fMRI) study suggested that they may be topographically variable across individuals, occurring, in most, in regions posterior to prefrontal cortex (PFC), and that detection of these regions may be best suited to a single-subject (SS) approach to fMRI analysis. In contrast, other studies using spatially normalized group-averaged (SNGA) analyses have localized storage-related activity to PFC. To evaluate the necessity of the regions identified by these two methods, we applied repetitive transcranial magnetic stimulation (rTMS) to SS- and SNGA-identified regions throughout the retention period of a delayed letter-recognition task. Results indicated that rTMS targeting SS analysis-identified regions of left perisylvian and sensorimotor cortex impaired performance, whereas rTMS targeting the SNGA-identified region of left caudal PFC had no effect on performance. Our results support the view that the short-term retention of verbal information can be supported by regions associated with acoustic, lexical, phonological, and speech-based representation of information. They also suggest that the brain bases of some cognitive functions may be better detected by SS than by SNGA approaches to fMRI data analysis.

Figure: Example from subject 7 of SS and SNGA rTMS targets (orange markers; anterior, SNGA; posterior, SS). White blobs on the brain are load-sensitive regions identified by the SS analysis, which have been merged onto this subject's high-resolution T1-weighted anatomical scan, and are visible at this depth of scalp "peeling."

Reverie

I'm incredulous that over 38,000 people have viewed a recording of Debussy's Reverie that I put on YouTube, and 79 people have made comments (which led me to record a second version). There was also a video response that I thought I would pass on, another video titled "Reverie":

Origin of language from cortical motor systems - evidence from fMRI imaging

Meister and Iacoboni offer some interesting observations supporting the idea that language evolved as an exaptation from motor cortical systems. Here is some of their text and a central figure from the paper.

It has been suggested that cortical neural systems for language evolved from motor cortical systems, in particular from those fronto-parietal systems responding also to action observation. While previous studies have shown shared cortical systems for action – or action observation - and language, they did not address the question of whether linguistic processing of visual stimuli occurs only within a subset of fronto-parietal areas responding to action observation. If this is true, the hypothesis that language evolved from fronto-parietal systems matching action execution and action observation would be strongly reinforced

...functional magnetic resonance imaging (fMRI) was used while subjects watched video stimuli of hand-object-interactions and control photo stimuli of the objects and performed linguistic (conceptual and phonological), and perceptual tasks. Since stimuli were identical for linguistic and perceptual tasks, differential activations had to be related to task demands. The results revealed that the linguistic tasks activated left inferior frontal areas that were subsets of a large bilateral fronto-parietal network activated during action perception. Not a single cortical area demonstrated exclusive – or even simply higher - activation for the linguistic tasks compared to the action perception task.

The results show that linguistic tasks do not only share common neural representations but essentially activate a subset of the action observation network if identical stimuli are used. Our findings strongly support the evolutionary hypothesis that fronto-parietal systems matching action execution and observation were co-opted for language, a process known as exaptation.

Figure 3. a) cortical networks activated by the decision task relating to action observation vs rest (Vd-Perc vs rest, red) and action observation vs perceptual decisions on photos of the same objects (Vd-Perc vs Ph-Perc, blue). The large bihemispheric networks found for both contrasts were very similar, suggesting that the fMRI activations found here mainly were related to action observation and not to processes of decision making or object perception required during these tasks, as well. b) Cortical networks activated during the phonological (blue) and the conceptual decision task (red) on photos of manipulable objects. The networks activated by these two linguistic tasks were entirely part of the action observation network depicted in Fig. 3a, in accordance with the hypothesis that development of language out of the mirror neuron system was driven by a process of exaptation.

How potential reward biases our attention

Our eyes dart about (make saccades) rapidly as we view a visual scene - without these small rapid movements we are blind. Milsteen and Doris have made the fascinating observation that how rapidly we make these small movements can be influenced by the potential reward value of the visual target. Here is the work, in abstract-speak:

Basing higher-order decisions on expected value (reward probability x reward magnitude) maximizes an agent's accruement of reward over time. The goal of this study was to determine whether the advanced preparation of simple actions reflected the expected value of the potential outcomes. Human subjects were required to direct a saccadic eye movement to a visual target that was presented either to the left or right of a central fixation point on each trial. Expected value was manipulated by adjusting the probability of presenting each target and their associated magnitude of monetary reward across 15 blocks of trials. We found that saccadic reaction times (SRTs) were negatively correlated to the relative expected value of the targets. Occasionally, an irrelevant visual distractor was presented before the target to probe the spatial allocation of saccadic preparation. Distractor-directed errors (oculomotor captures) varied as a function of the relative expected value of, and the distance of distractors from, the potential valued targets. SRTs and oculomotor captures were better correlated to the relative expected value of actions than to reward probability, reward magnitude, or overall motivation. Together, our results suggest that the level and spatial distribution of competitive dynamic neural fields representing saccadic preparation reflect the relative expected value of the potential actions.

Language Evolution: An invisible hand.

A slightly edited "Editor's Summary" from the Oct. 11 Nature:

As a language evolves, grammatical rules emerge and exceptions die out. Lieberman et al. have calculated the rate at which a language grows more regular, based on 1,200 years of English usage. Of 177 irregular verbs, 79 became regular in the last millennium. And the trend follows a simple rule: a verb's half-life scales as the square root of its frequency. Irregular verbs that are 100 times as rare regularize 10 times faster. The emergence of a rule (such as adding –ed for the past tense) spells death for exceptional forms...In a separate study, Pagel et al. looked at changing word meanings. Across the Indo-European languages, words like 'tail' or 'bird' evolve rapidly and are expressed by many unrelated words. Others, like 'two', are expressed by closely related word forms across the whole language family. Data from over 80 modern languages show that the more a word is used, the less it changes.

And, from Fitch's review of the two papers:

The words of language are not inherited biologically, but are passed on culturally through learning. This process of 'cultural evolution' generates a hierarchical tree of relationships among languages, here illustrated by the Indo-European family. Just as descent with modification in biological evolution (phylogeny) leads to phylogenetic trees, so the analogous process in language change (glossogeny) can lead to glossogenetic trees.

Where should we look to gain a deeper understanding of the invisible hand in the cultural evolution of language? A promising future direction is provided by recent attempts to fuse theoretical models of cultural evolution to experimental investigations of social learning in the laboratory. Experimental investigations of 'iterated learning' — similar to the game of Chinese whispers, where one participant's output serves as input for the next — can provide empirical data to inspire, and constrain, our theories. Sophisticated new theoretical models enable language-learning 'agents' to have both innate biases (in the form of so-called bayesian priors) and powerful statistical learning systems capable of discovering and using environmental regularities. Such models demonstrate the possibility of a very indirect and sometimes non-intuitive relationship between the regularities emerging at the level of a whole population and the underlying generating forces. These forces are individual behaviour and learning (social usage) and innate constraints (in Chomsky's terms, a 'language acquisition device', often called universal grammar).

..some of the most persistent 'cultural replicators' — memes — evolve as slowly as some genes. By documenting and quantifying such effects, this work opens the door to a diverse range of theoretical and empirical investigations. If there is ever to be a science of memetics o rival that of genetics, it should proceed along these lines: combining careful quantitative analysis of well-documented linguistic changes with sophisticated theoretical models capable of taking into account the multilayered complexity of cultural evolution.

Emotional enhancement of memory and learning - a molecular mechanism.

Hu et al. have performed an interesting study of how the rush of noradrenaline during an emotional experience might enhance our ability to recall that experience. It causes a long term enhancement of the activity of nerve synapses using the neurotransmitter glutamate by stimulating the phosphorylation of a particular type of glutamate receptor. I'm afraid the molecular details will only make sense to those of you who know something about the chemistry of nerve transmission, but here they are, as outlined in the article's abstract:

Emotion enhances our ability to form vivid memories of even trivial events. Norepinephrine (NE), a neuromodulator released during emotional arousal, plays a central role in the emotional regulation of memory. However, the underlying molecular mechanism remains elusive. Toward this aim, we have examined the role of NE in contextual memory formation and in the synaptic delivery of GluR1-containing α-amino-3-hydroxy-5-methyl-4-isoxazoleproprionic acid (AMPA)-type glutamate receptors during long-term potentiation (LTP), a candidate synaptic mechanism for learning. We found that NE, as well as emotional stress, induces phosphorylation of GluR1 at sites critical for its synaptic delivery. Phosphorylation at these sites is necessary and sufficient to lower the threshold for GluR1 synaptic incorporation during LTP. In behavioral experiments, NE can lower the threshold for memory formation in wild-type mice but not in mice carrying mutations in the GluR1 phosphorylation sites. Our results indicate that NE-driven phosphorylation of GluR1 facilitates the synaptic delivery of GluR1-containing AMPARs, lowering the threshold for LTP, thereby providing a molecular mechanism for how emotion enhances learning and memory.