"Wanting" what was never "liked"

Work from Berridge and collaborators shows in rat experiments that pathways in the ventral pallidum that fire when a cue to a previously liked stimulus (such as sucrose) is presented - but do not fire with a cue of the previously "disliked" taste of intense salt - can suddenly become activated if the salt cue is encountered in a never-before-experienced state of physiological salt depletion. This means that dynamic recomputation of cue-triggered "wanting" signals can occur in real time at the moment of cue re-encounter by combining a previously learned Pavlovian associations with novel physiological information about a current state of specific appetite.

Long live quest gets respect? The 120 Club.

Nicholas Wade notes a recent meeting on aging at Harvard Medical School (Some of the participants belong to the "120 Club," whose members propose to live until they are 120). His article focuses on work of David Sinclair and Sirtris Pharmaceuticals .

...In mice, sirtuin activators are effective against lung and colon cancer, melanoma, lymphoma, Type 2 diabetes, cardiovascular disease and Alzheimer’s disease...SRT-501, the company’s special formulation of resveratrol, is being tested against two cancers, multiple myeloma and colon cancer that has spread to the liver. A chemical mimic of resveratrol, known as SRT-2104, is in a Phase 2 trial for Type 2 diabetes, and in a Phase 1 trial in elderly patients. (Phase 1 trials test for safety, Phase 2 for efficacy.)...unpublished tests in mice showed that another chemical mimic, SRT-1720, increased both health and lifespan; after two years, twice as many mice taking the drug were alive compared with the undosed animals. Resveratrol itself has not been shown to increase lifespan in normal mice, although it does so in obese mice, laboratory roundworms and flies.

Brain organization of our defensive fear system.

Mobbs et al. show that higher forebrain areas are involved in early-threat responses, including the assignment and control of fear, whereas imminent danger results in fast more "hard-wired" defensive reactions mediated by our midbrain.

Seeing our body reduces pain

An interesting report from Longo et al. :

Given previous reports of strong interactions between vision and somatic senses, we investigated whether vision of the body modulates pain perception. Participants looked into a mirror aligned with their body midline at either the reflection of their own left hand (creating the illusion that they were looking directly at their own right hand) or the reflection of a neutral object. We induced pain using an infrared laser and recorded nociceptive laser-evoked potentials (LEPs). We also collected subjective ratings of pain intensity and unpleasantness. Vision of the body produced clear analgesic effects on both subjective ratings of pain and the N2/P2 complex of LEPs. Similar results were found during direct vision of the hand, without the mirror. Furthermore, these effects were specific to vision of one's own hand and were absent when viewing another person's hand. These results demonstrate a novel analgesic effect of non-informative vision of the body.

When errors are rewarding

de Bruijn et al. show a clear distinction between error and reward processing in our brains:

For social beings like humans, detecting one's own and others' errors is essential for efficient goal-directed behavior. Although one's own errors are always negative events, errors from other persons may be negative or positive depending on the social context. We used neuroimaging to disentangle brain activations related to error and reward processing, by manipulating the social context (cooperation or competition). Activation in posterior medial frontal cortex (pMFC) was increased for all errors, independent of who made the error or the reward outcome. Conversely, activity in striatum was modulated by reward, independent of whether the action was erroneous or not. The results demonstrate a clear distinction between error and reward processing in the human brain. Importantly, the current study indicates that error detection in pMFC is independent of reward and generalizes beyond our own actions, highlighting its role in optimizing performance in both individual and joint action.

The anxious temperament.

There is an engaging article by Henig in yesterday's New York Times Magazine: "Understanding the anxious mind." It focuses on the famous work of Jerome Kagan at Harvard; who, along with others, has shown that some of us are born with a predisposition to be timid and anxious.

Memory consolidation - a shift from hippocampal to neocortical sites

Work from Takashima et al. confirms the idea that the retrieval network for memories shifts away from using the hippocampus as the memories grow older and are consolidated in the neocortex. They use MRI measurement to observe this shift:

The standard model of system-level consolidation posits that the hippocampus is part of a retrieval network for recent memories. According to this theory, the memories are gradually transferred to neocortical circuits with consolidation, where the connections within this circuit grow stronger and reorganized so that redundant and/or contextual details may be lost. Thus, remote memories are based on neocortical networks and can be retrieved independently of the hippocampus. To test this model, we measured regional brain activity and connectivity during retrieval with functional magnetic resonance imaging. Subjects were trained on two sets of face–location association and were tested with two different delays, 15 min and 24 h including a whole night of sleep. We hypothesized that memory traces of the locations associated with specific faces will be linked through the hippocampus for the retrieval of recently learned association, but with consolidation, the activity and the functional connectivity between the neocortical areas will increase. We show that posterior hippocampal activity related to high-confidence retrieval decreased and neocortical activity increased with consolidation. Moreover, the connectivity between the hippocampus and the neocortical regions decreased and in turn, cortico-cortical connectivity between the representational areas increased. The results provide mechanistic support for a two-level process of the declarative memory system, involving initial representation of new associations in a network including the hippocampus and subsequent consolidation into a predominantly neocortical network.

Mindblog backlog...

Another compilation of items that are potentially interesting to some MindBlog readers:

Two Blogs of interest: Body in Mind (self explanatory) and Phenomics (on more intelligent description of personality dysfunction based on underlying genetic heterogeneity, and how the the Diagnostic and Statistical Manual of Mental Disorders actually impedes research and understanding.)

The robot that breaks and reassembles itself.

Why we need God. From Robert Wright, author of “The Moral Animal,” “Nonzero” and, most recently, “The Evolution of God.”

Eyes Wide Shut - perceived emotionality of music, eye closure, and the amygdala.

Brain pathology in athletes appears at an unusually young age.

Numbers in the Blind's “Eye.” Both blind and sighted people represent numbers through a spatial code, but with different electrophysiological correlates corresponding to cognitive versus sensory processing.

Gates Puts Feynman Lectures Online. These famous lectures can show you that there really is joy in physics. I was overwhelmed when I first saw some of them in my college days.

Knowledge rewards. It turns out that the size of coming rewards is signalled by the same dopamine neurons that signal primitive rewards like sex and food. Two monkeys were trained to glance at one of two targets on a computer screen in order to receive a drink reward, which was randomly large or small. When one target included information about reward size the monkeys preferred to go for that target, rather than be surprised by a randomly sized reward. Neurons in the brain's 'reward' circuitry fired when the monkeys learned information about the future, suggesting that the act of prediction may be intrinsically rewarding.

Yet another theory on why we sleep ...suggestion that sleep evolved to optimize animals’ use of time, keeping them safe and hidden when the hunting, fishing or scavenging was scarce and perhaps risky. In that view, differences in sleep quality, up to and including periods of insomnia, need not be seen as problems but as adaptations to the demands of the environment.

How our brain remembers the consequences of our actions

A fundamental building block in shaping our behavior is the relationship between a sensory event, a chosen action and its consequences. Histed et al. now point to how the brain stores this information by showing that neurons in the monkey prefrontal cortex and basal ganglia display persistent activity that is related to the outcomes of previous actions. Seo and Lee review this work in Nature, noting in the figure the sort of stimulus, action, outcome sequence that is in question :


Basically, the data suggest that the prefrontal cortex and basal ganglia might be essential brain areas for storing information about action–outcome associations

Mindblindness in Asperger's syndrome

Recent work by Senju et al. is summarized in Science:

Placement of Asperger syndrome within the family of autism spectrum disorders (ASD) has always been a bit uneasy; although people with Asperger syndrome do exhibit the core impairments in social interaction and communication that are characteristic of ASD, they nevertheless perform well on tests that are thought to assess the ability to mentalize or to possess Theory of Mind skills. One of the classic tests of mentalizing ability is the false-belief task, in which subjects must be able to represent their own beliefs (true) and another's beliefs, which are false because they have not been given complete information, such as not having seen the transfer of a piece of candy from one drawer to another. People with Asperger syndrome succeed at the verbal form of the false-belief task, yet Senju et al. show that this is owing entirely to their having learned how to cope with an existing and still demonstrable deficit in an implicit version of the false-belief task. That is, the core impairment is present, but conscious and explicit learning allows them to compensate.

Here is the Senju et al. abstract:

Adults with Asperger syndrome can understand mental states such as desires and beliefs (mentalizing) when explicitly prompted to do so, despite having impairments in social communication. We directly tested the hypothesis that such individuals nevertheless fail to mentalize spontaneously. To this end, we used an eye-tracking task that has revealed the spontaneous ability to mentalize in typically developing infants. We showed that, like infants, neurotypical adults’ (n = 17 participants) eye movements anticipated an actor’s behavior on the basis of her false belief. This was not the case for individuals with Asperger syndrome (n = 19). Thus, these individuals do not attribute mental states spontaneously, but they may be able to do so in explicit tasks through compensatory learning.

Green Porno.

In the 25 Sept. issue of Science Magazine, the Gonzo Scientist points us to these humorous performances on the Sundance channel (worth checking out) by Isabella Rossellini. She offers a series of brief video performances, between 1 and 2 minutes long, in which she dresses in elaborate animal costumes to paint a miniportrait of several organisms, describing key features of their physiology and behavior - in particular their reproductive biology.

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