Do we trust our eyes or our ears?

Interesting Angier article on our visual versus sound time resolution, and how situations with conflicting visual and auditory stimuli are resolved. You can hear 20 clicks per second, but twenty visual frames per second is a movie.

Models of life's origins - great videos

Check out Wade's article that has, and links to, some great videos illustrating how a synthetic cell might be made by getting a protocell formed of lipids and a genetic molecule to grow and divide in parallel, with the molecules being encapsulated in the cell. If the molecules gave the cell a survival advantage over other cells, the outcome would be a sustainable, autonomously replicating system, capable of Darwinian evolution.

Gene for depression debunked...

Benedict Carey writes on how a compelling study showing a correlation between a particular variant of a gene involved in Serotonin regulation and the probability of sinking into depression after a stressful event has not been replicated. A coalition of researchers identified 14 studies that gathered the same kinds of data as the original study. They reanalyzed the data and found no evidence of an association between the serotonin gene and the risk of depression, no matter what people’s life experience was.

Zap your brain to enhance your planning ability

Enhancement of Planning Ability by Transcranial Direct Current Stimulation.

Prayer in devoutly religious people recruits social cognition brain areas.

Schjoedt et al. suggest that praying to God is an intersubjective experience comparable to ‘normal’ interpersonal interaction.

Back from vacation - A new variety of MindBlog post....reader poll.

Back from vacation...I had thought that a sudden halt in the daily habits surrounding blog production might cause some withdrawal symptoms. But no... nothing, zip. Now I face a very long accumulated list of potential post topics, which brings home the point that my ritual of doing two blog posts per day forces me to choose only a fraction of the articles that I find interesting as I scan the tables of contents of a number of journals. Among those discarded articles are many that I am sure a subset of MindBlog readers would like to be aware of, even if only given a minimal description of content along with the link to the journal. So, for the next week or two at least, I am going to experiment with sprinkling in more tiny posts, in much the same way that Andrew Sullivan's blog does. The reason for making each a separate post is that the titles then appear in the list presented by RSS readers. (On a typical weekday there are ~200-250 significant post viewings, out of ~1,150 RSS feed subscribers.)

I can think of arguments against doing this (overload, spamming), so I would be grateful for feedback on whether readers think this is a good or bad idea. How many topics/day would you find most useful?

Stress triggers our habitual behaviors

Schwabe and Wolf at Ruhr University in Bochum show that stress promotes habits at the expense of goal-directed performance in humans. Converging lines of evidence show that stress and the glucocorticoid stress hormones (mainly cortisol in humans) released from the adrenal cortex can operate as a switch between "cognitive" (mediated by prefrontal cortex) and "habit" (mediated by striatum)learning systems.

You want to know the truth? Then don't mimic!

We usually feel that expressing empathy by mimicking another person's face and body movements facilitates our understanding of their true emotions. Not so, apparently, if they are lying. Stel et al. have done experiments with two interacting people as follows:

...targets either lied or told the truth, while observers mimicked or did not mimic the targets' facial and behavioral movements. Detection of deception was measured directly by observers' judgments of the extent to which they thought the targets were telling the truth and indirectly by observers' assessment of targets' emotions. The results demonstrated that nonmimickers were more accurate than mimickers in their estimations of targets' truthfulness and of targets' experienced emotions. The results contradict the view that mimicry facilitates the understanding of people's felt emotions. In the case of deceptive messages, mimicry hinders this emotional understanding.

Economy still at the brink

I found this article by two professional Wall Street traders (one out of prison, pardoned by Clinton), to be fascinating.

Brain Music

Wu et al. transform EEG signals during REM sleep and slow wave sleep into musical 'melodies' that induce in listeners (so they say) happy emotions (REM) or drowsy peaceful feelings (SWS). Click on the audio links in the article to judge for yourself.

MindBlog is taking a vacation

For the next 10 days I will be in Amsterdam and Munich on vacation with my daughter Sarah. I think I will suspend blog posting for about two weeks. I have been doing regular weekday postings continuously since February of 2006, and I'm curious to see what life is like in their absence!

The genetics of musical aptitude

Ukkola et al. attempt to understand the neurobiological basis of music in human evolution and communication, motivated by the idea that a main function of music is human social communication. They find a correlation between variations in groups of genes associated with social bonding and cognitive functions and musical aptitude and creativity. They suggest that the neurobiology of music perception and production is likely to be related to the pathways affecting intrinsic attachment behavior. (By the way, in the same issue of PLoS ONE, Israel et al. correlate variations the vasopressin 1a receptor gene (AVPR1a) also monitored by Ukkola et al. with prosocial behavior in several game tasks).

Language influence on color perception.

Here is an interesting bit of work that shows that our brain's language regions can exert a top down influence on early color processing in the visual cortex. The experiments show that colors from different linguistic categories presented to the right visual field (which projects to the left linguistic cortex) caused much stronger activation of visual areas 2 and 3 than stimuli presented to the left visual field (which projects to the right hemisphere). Here is the abstract:

The effect of language on the categorical perception of color is stronger for stimuli in the right visual field (RVF) than in the left visual field, but the neural correlates of the behavioral RVF advantage are unknown. Here we present brain activation maps revealing how language is differentially engaged in the discrimination of colored stimuli presented in either visual hemifield. In a rapid, event-related functional MRI study, we measured subjects' brain activity while they performed a visual search task. Compared with colors from the same lexical category, discrimination of colors from different linguistic categories provoked stronger and faster responses in the left hemisphere language regions, particularly when the colors were presented in the RVF. In addition, activation of visual areas 2/3, responsible for color perception, was much stronger for RVF stimuli from different linguistic categories than for stimuli from the same linguistic category. Notably, the enhanced activity of visual areas 2/3 coincided with the enhanced activity of the left posterior temporoparietal language region, suggesting that this language region may serve as a top-down control source that modulates the activation of the visual cortex. These findings shed light on the brain mechanisms that underlie the hemifield- dependent effect of language on visual perception.

Cognitive Illusions

My son Jon pointed me to this engaging TED talk on cognitive illusions by Dan Ariely.

Genes to cognition

Here is an educational site you might enjoy checking out, supported by the Cold Spring Harbor Laboratory.

Attention training and attention state training

Tang and Posner (PDF here) examine two different approaches that have been shown to improve attention and self-regulation: computer based exercises in children and adults (attention training, AT); and exposure to nature, mindfulness and integrative body-mind training (IBMT, or attention state training, AST). Here is their summary of the characteristics of these two approaches:

AT
• Trains executive attention networks
• Requires directed attention and effortful control
• Targets non-autonomic control systems
• Produces mental fatigue easily
• Training transfers to other cognitive abilities

AST
• Produces changes of body-mind state
• Requires effortful control (early stage) and effortless exercise (later)
• Involves the autonomic system
• Aims at achieving a relaxed and balanced state
• Training transfers to cognition, emotion and social behaviors

Activation of the anterior cingulate cortex appears to be central with both approaches, with AT involving involving changes in anterior cingulate and lateral prefrontal areas, perhaps mainly through increased connectivity between the two. AST involves increased interaction between anterior cingulate cortex and the autonomic nervous system. Increase in activity in the ACC in AST is similar to what is found in AT during task performance and could account for the improved executive attention with both methods.

It is worth noting that both aerobic exercise (A.F. Kramer and K.I. Erickson, Capitalizing on cortical plasticity: influence of physical activity on cognition and brain function, Trends Cogn. Sci. 11 (2007), pp. 342–348) and music education (E.G. Schellenberg, Music and cognitive abilities, Psychol. Sci. 14 (2004), pp. 317–320.) have also been shown to enhance cognitive processes

Lucid old age.

Want to live past 90 without dementia? Check out this article by Benedict Carey describing a retirement community in Los Angeles.

Empathy Marketing 101

I pass on this interesting review on "neuromarketing" that Gary Ohlson has just emailed to me.

Stress pathways that impair prefrontal cortex.

Arnsten offers a focus article (one among several) in Nature Reviews Neuroscience that describes how stress impairs the top-down cognitive control functions of the prefrontal cortex, and enhances bottom-up amygdala-limbic emotional influences. I'm passing on the abstract and a summary figure with its text that might be useful for teaching:

The prefrontal cortex (PFC) — the most evolved brain region — subserves our highest-order cognitive abilities. However, it is also the brain region that is most sensitive to the detrimental effects of stress exposure. Even quite mild acute uncontrollable stress can cause a rapid and dramatic loss of prefrontal cognitive abilities, and more prolonged stress exposure causes architectural changes in prefrontal dendrites. Recent research has begun to reveal the intracellular signalling pathways that mediate the effects of stress on the PFC. This research has provided clues as to why genetic or environmental insults that disinhibit stress signalling pathways can lead to symptoms of profound prefrontal cortical dysfunction in mental illness.


The prefrontal cortex (PFC) has extensive connections with other cortical and subcortical regions that are organized in a topographical manner, such that regions that regulate emotion are situated ventrally and medially (green area in part a of the figure) and regions that regulate thought and action are situated more dorsally and laterally (blue and blue–green areas in part a). The dorsolateral PFC (DLPFC) has extensive connections with sensory and motor cortices and is key for regulating attention, thought and action1. In humans, the right inferior PFC (rIPFC) seems to be specialized for inhibiting inappropriate motor responses. By contrast, the ventromedial PFC (VMPFC) has extensive connections with subcortical structures (such as the amygdala, the nucleus accumbens and the hypothalamus) that generate emotional responses and habits and is thus able to regulate emotional responses. Finally, the dorsomedial PFC (DMPFC) has been associated with error monitoring9 and, in human functional MRI studies, reality testing. These PFC regions extensively interconnect to regulate higher-order decision making and to plan and organize for the future. Under non-stress conditions (see part a of the figure), the extensive connections of the PFC orchestrate the brain's activity for intelligent regulation of behaviour, thought and emotion. The PFCalso has direct and indirect connections to monoamine cell bodies in the brainstem, such as the locus coeruleus (LC) (where noradrenaline projections arise) and the substantia nigra (SN) and ventral tegmental area (VTA) (where the major dopamine projections originate), and thus can regulate its own catecholamine inputs. Optimal levels of catecholamine release in turn enhance PFC regulation, thus creating a 'delicious cycle'. Under conditions of psychological stress (see part b of the figure) the amygdala activates stress pathways in the hypothalamus and brainstem, which evokes high levels of noradrenaline (NA) and dopamine (DA) release. This impairs PFC regulation but strengthens amygdala function, thus setting up a 'vicious cycle'. For example, high levels of catecholamines, such as occur during stress, strengthen fear conditioning mediated by the amygdala. By contrast, stress impairs higher-order PFC abilities such as working memory and attention regulation. Thus, attention regulation switches from thoughtful 'top-down' control by the PFC that is based on what is most relevant to the task at hand to 'bottom-up' control by the sensory cortices, whereby the salience of the stimulus (for example, whether it is brightly coloured, loud or moving) captures our attention5. The amygdala also biases us towards habitual motor responding rather than flexible, spatial navigation. Thus, during stress, orchestration of the brain's response patterns switches from slow, thoughtful PFC regulation to the reflexive and rapid emotional responses of the amygdala and related subcortical structures.

Parietal brain neurons tuned to fractions

Interesting work from Jacob and Nieder:

Although the concept of whole numbers is intuitive and well suited for counting and ordering, it is with the invention of fractions that the number system gained precision and flexibility. Absolute magnitude is encoded by single neurons that discharge maximally to specific numbers. However, it is unknown how the ratio of two numbers is represented, whether by processing numerator and denominator in separation, or by extending the analog magnitude code to relative quantity. Using functional MRI adaptation, we now show that populations of neurons in human fronto-parietal cortex are tuned to preferred fractions, generalizing across the format of presentation. After blood oxygen level-dependent signal adaptation to constant fractions, signal recovery to deviant fractions was modulated parametrically as a function of numerical distance between the deviant and adaptation fraction. The distance effect was invariant to changes in notation from number to word fractions and strongest in the anterior intraparietal sulcus, a key region for the processing of whole numbers. These findings demonstrate that the human brain uses the same analog magnitude code to represent both absolute and relative quantity. Our results have implications for mathematical education, which may be tailored to better harness our ability to access automatically a composite quantitative measure.