Wednesday, May 31, 2006

Autistic children insensitive to emotional expressions in others also show decreased activity in their brain's 'mirror neuron' system.

Systems of mirror neurons in our brains are active during our actions and feelings and also when we observe those actions or feelings in others (see the Feb. 9 posting in this blog). Dapretto et al. now show that mirror neuron system activity during observation of emotional expressions in typically developing children is much greater than in autistic children. This suggests that a dysfunctional mirror neuron system may underlie the social deficits observed in autism.

Legend: Mirror neuron system activity during observation of emotional expressions. The right pars opercularis showed significantly greater activity in typically developing children than in children with ASD (t > 1.83, P < 0.05, small volume corrected). Credit: Nature Neuroscience

Tuesday, May 30, 2006

Why don't we choose what makes us happy?

Hsee and Hastie provide an interesting review of this issue in Trends in Cognitive Sciences. Numerous studies prove that people systematically fail to predict or choose what maximizes their happiness. This casts doubt on the validity of social policies that assume that people can act in their own best interest in choosing between health providers, retirement plans, public offices, multiple commercial products, etc.

There are two central reasons for this failure: predictions biases and failures to follow predictions. Prediction biases occur because predictors do not full appreciate the differences between the state of prediction and the state of experience. One might be more or less hungry, rested, or sexually aroused while predicting versus experiencing (projection bias). Memory, beliefs, number of distinctions being made can also lead to bias errors. Failures to follow predictions of what will generate the greatest overall happiness can occur when instead the choice is made with the greatest immediate appeal (impulsivity), that is easy to justify (lay rationalism), that yields the greatest token reward such as money (medium maximization), or that fits choice rules (lay rationalism).

Friday, May 26, 2006

Cooperation, Punishment, and the Evolution of Human Institutions

This is the title of a review by Henrich of studies on how human cooperations and sanctions might have evolved, which specifically cites a paper by Gurerk et al in Science. People are offered the choice of two institutions in which individuals make voluntary contributions with the total then being equally distributed among all. Participants know what was contributed by others. In the first, individuals who do not contribute still receive an equal share of the total collected but no sanctions are applied to poor contributors. In the second, participants can choose to penalize slackers at some cost to themselves. The authors show "that a sanctioning institution is the undisputed winner in a competition with a sanction-free institution. Despite initial aversion, the entire population migrates successively to the sanctioning institution and strongly cooperates, whereas the sanction-free society becomes fully depopulated. The findings demonstrate the competitive advantage of sanctioning institutions and exemplify the emergence and manifestation of social order driven by institutional selection."

Thursday, May 25, 2006

Stressing out or Chilling out changes how our genes are expressed in an immediate and dynamic way.

Bittman et al., in "Recreational music-making modulates the stress response and alters individual gene expression," have followed the expression of 45 genes associated with stress, immune, and inflammation responses after one hour of a stress induction protocol (solving a 500 piece puzzle while being told at 10 minute intervals that other subjects were doing better). Subjects were then split into three groups for a further hour: one continued the stressful situation, the second read a newspaper, and the third participated in a recreational music making session (the clavinova connection). In the latter group 19 genes expression changes caused by stress were significantly reversed. None were reversed in the group continuing the stress test and 6 reversed in the group just reading a newspaper.

Wednesday, May 24, 2006

The brain finds pleasure in novelty.......

Humans are informavores, and derive pleasure from novel auditory and visual stimulation. Biederman and Vessel note that novel visual images rated most highly by observed also cause stronger activation of the parahippocampal gyrus, where they are interpreted in the context of stored memories, and this activation fades as the same image is repeated and becomes more familiar. This area is also rich in mu-opioid receptors (involved in pleasure and reward, and activated by morphine and endogenous morphine-like substances - endomorphins - in the brain). They suggest that the rate of endomorphin release in the parahippocampal cortex partially underlies our human preference for experiences that are both novel and richly interpretable.

Legend: Visual information flows from the primary visual cortex (bottom, orange) towards parahippocampal regions where it is interpreted (middle, purple). Credit: American Scientist.

Tuesday, May 23, 2006

Religion as a Natural Phenomenon - More on Dennett's Book "Breaking the Spell"

This book has now received extensive and varying reviews in both popular (New York Times Book Review, The New Yorker) and scientific (Science, Nature) magazines. Dennett and others argue that religion appeared because groups of humans that developed religious rituals replicated themselves more successfully than those that did not. The fact that human brains developed both self awareness and awareness that others are aware may have led us to have hyperactive agent detection capabilities that not only protect us, but also lead us to believe that rocks and trees are imbued with intentional minds or spirits. This is animism, which led to polytheism, and eventually monotheism. The values of religion to evolutionary fitness could include (from Shermer's review in Science) mythmaking (to explain the dangers and meaning of the natural world), morality (to regulate pro- and anti-social behavior), sociality (within-group amity and between-group enmity), and redemption and resurrection (forgiveness in this life and immortality in the next life). Dennett points out how US mega-churches cater to people's needs - they have a product that opens the wallets of their members as well as moral and social values "that lead to anti-abortion fanaticism, capital punishment, excoriation of gays and lesbians, and dangerous military excursions in the Near East." (from Ruse's Nature review). The religion "meme" continues to grow in the vast majority of humans alive today. (The term "meme" , coined by Richard Dawkins, refers to thoughts, songs, or rituals that replicate and propagate from one human mind to another. The idea is that memes underlie cultural evolution just as genes underlie biological evolution.)

Monday, May 22, 2006

The pleasures and pains of information about the future.

Berns et al show that regions of the brain activated by pain are also activated by the anticipation of pain, and that some experimental subjects choose to receive an anticipated electrical shock sooner rather than later, to "get it over with," even when told the shock will be larger than the anticipated one.

It is also known that brain regions activated by pleasure are also activated by anticipation of pleasure, and subjects will frequently defer a desired outcome to prolong the pleasure of anticipation. These real behaviors are the exact opposite of those in many economic models, which assume that people will defer negative outcomes and accelerated desired ones.

A review by Loewenstein highlights varied studies on the utility of information, and how emotional factors lead people to desire or avoid it.

Friday, May 19, 2006

Two ways of knowing the minds of others

Mitchell's laboratory at Harvard has shed light on two traditionally opposed hypotheses about how we infer the mental states of others. Simulation theory posits that we use our own experience to infer the experience of others. It is known that when we observe actions and emotions in others, regions in our own brain that would generate those actions or emotions become active and mirror what we are observing. Theory of mind, on the other hand, holds that we use abstract rules about how people behave to infer the mental states of others.

Mitchell et al used functional neuroimaging to examine how perceivers make mental state inferences when such self-other overlap can be assumed (when the other is similar to oneself) and when it cannot (when the other is dissimilar from oneself). "We observed a double dissociation such that mentalizing about a similar other engaged a region of ventral mPFC (medial prefrontal cortex) linked to self-referential thought, whereas mentalizing about a dissimilar other engaged a more dorsal subregion of mPFC. "

Legend: Division of labor. Different regions of prefrontal cortex fire up when people ponder the mental states of others perceived as similar (blue) or dissimilar (red) to themselves. Credit: Jason Mitchell.

"The overlap between judgments of self and similar others suggests the plausibility of "simulation" accounts of social cognition, which posit that perceivers can use knowledge about themselves to infer the mental states of others." And, the activation of dorsal mPFC during thinking about dissimilar others might correspond to more rule bound theory of mind operations.

Thursday, May 18, 2006

The good, the bad and the amygdala

This is the title of a brief review by Ruth Williams in Nature Reviews Neuroscience pointing out an article by Paton et al. that demonstrates that in monkeys the values associated with visual stimuli are represented in the amygdala, a structure involved in reinforcement learning. Individual amygdala neurons apparently code for either "good" or "bad" . When a visual stimulus that was initially paired with a positive reward was switched to being paired with a negative reward, more that half of the responding amygdala neurons showed a switch in activity that correlated with changes in behavior, and some individual neurons showed value-specific activity. This work further confirms that the amygdala is a key brain structure in the representation of the learned value of visual stimuli.

Wednesday, May 17, 2006

Dolphins have discovered "names" of the sort we use.

It has been known since the 1960s that dolphins develop individually distinctive signature whistles that they use to maintain group cohesion. Now Janik et al have shown that dolphins extract identity information from signature whistles even after all voice features have been removed from the signal. The synthesized whistles retained the distinct variation in frequency over time of an individual's signal, but removed other characteristics like harmonics, dynamics, and extraneous noises such as the clicking sounds that dolphins can also make. When exposed to the artificial whistle modeled after that of a related group member, other dolphins turned towards the sound. Excerpts from Henry Fountain's comments on this work in the New York Times: "To draw an analogy to humans, the frequency modulation pattern is the "language," and the dolphins could identify it regardless of the whistle's "voice." And a quote from Janik: "Most other animals appear to rely on the sound of the voice, rather than any coded information, for recognition. But parrots may have similar "signature" calls, which shows that you can do this if you have a huge brain, but you can also do this if you have a small one."

Tuesday, May 16, 2006

Men and Women react differently to sniffing a social hormone - aggressively versus friendly

Thompson et al have found that a peptide influencing social behaviors in numerous species, Arginine vasopressin (AVP), causes different behaviors in men and women when administered intranasally with an inhaler. In men, AVP stimulates agonistic (i.e. combative) facial motor patterns in response to the faces of unfamiliar men and decreases perceptions of the friendliness of those faces. In contrast, in women, AVP stimulates affiliative facial motor patterns in response to the faces of unfamiliar women and increases perceptions of the friendliness of those faces. AVP also affected autonomic responsiveness to threatening faces and increased anxiety, which may underlie which may underlie the peptide's sex-specific effects on social communication by promoting different social strategies in response to stress in the sexes. The authors note; "Because intranasal AVP administration crosses the blood-brain barrier and, at the dose we used, directly affects central processes, whereas peripheral elevations do not, we argue that the effects we observed were likely centrally mediated, either through CSF-signaling mechanisms or by means of diffusion into discrete brain areas. Thus, our results support the hypothesis that central AVP's ability to influence social communication processes, a conserved trait of AVT and AVP in vertebrates, has been retained in humans."

Monday, May 15, 2006

Recursion in vocalization not unique to humans

Several years ago Marc Hauser, Noam Chomsky and Tecumseh Fitch published an influential paper that speculated that recursion, or self embedding, might be the one aspect of language that is clearly unique to humans. Gentner et al have now shown that the European starling can be trained to recognize complex recursive grammars. A review by Marcus suggest that "the abstract computational capacity of language may consist not so much of a single innovation as a novel evolutionary reconfiguration of many.. ancestral cognitive components, genetically rejigged into a new whole. Contemporary research suggests that the human brain contains few if any unique neuronal types, and few if any genes lack a significant ancestral precedent."

Wednesday, May 10, 2006

Stumbling on Happiness

This is the title of a new book by Harvard psychologist Daniel Gilbert. One quote from the N.Y. Times review by Scott Stossel in the May 7 book review section: "When we have an experience..on successive occasions, we quickly begin to adapt to it, and the experience yields less pleasure each time...Psychologists call this habituation, economists call it declining marginal utility, and the rest of us call it marriage."

His basic theme is that humans are very bad at predicting what will make them happy. Things we expect to give us joy make us less happy than we think; and things that we dread make us less unhappy, especially after some time has passed. There is a "psychological immune system" that starts up after big negative events.

From the book: "How do we manage to think of ourselves as great drivers, talented lovers and brilliant chefs when the facts of our lives include a pathetic parade of dented cars, disappointed partners and deflated souffles?...The answer is simple: We cook the facts." What gets us through life is just the right amount of delusion, enough to fool us into feeling relatively good about ourselves. Interestingly, the clinically depressed seem less susceptible to these basic cognitive errors.