Your Money and Your Brain

I thought I would pass on this brief commentary by Joe Nocera in the NY Times (PDF here), which emphasizes comments by Jason Zweig on how our emotional brains are not very well suited for making rational financial decisions.

A neural marker of consciousness

Here is the author's summary of an interesting article by Del Cul et al. in PlosBiology.

Understanding the neural mechanisms that distinguish between conscious and nonconscious processes is a crucial issue in cognitive neuroscience. In this study, we focused on the transition that causes a visual stimulus to cross the threshold to consciousness, i.e., visibility. We used a backward masking paradigm in which the visibility of a briefly presented stimulus (the “target”) is reduced by a second stimulus (the “mask”) presented shortly after this first stimulus. (Human participants report the visibility of the target.) When the delay between target and mask stimuli exceeds a threshold value, the masked stimulus becomes visible. Below this threshold, it remains nonvisible. During the task, we recorded electric brain activity from the scalp and reconstructed the cortical sources corresponding to this activity. Conscious perception of masked stimuli corresponded to activity in a broadly distributed fronto-parieto-temporal network, occurring from about 300 ms after stimulus presentation. We conclude that this late stage, which could be clearly separated from earlier neural events associated with subliminal processing and mask-target interactions, can be regarded as a marker of consciousness.


Figure: Top, depth of cortical processing: subliminal stimuli (left panel) should evoke a strong activation in extrastriate visual cortex, but their intensity should quickly decrease in higher visual areas; only conscious stimuli (right panel) should trigger a late surge of activation in a global prefronto-parietal network. Bottom, schematic time course of activation as a function of masking strength. Masking is expected to have little effect on early visual activation but to modulate the strength of activation in higher visual areas. Furthermore, there should be a nonlinear effect of masking strength in prefrontal cortex, with a similar late top-down activation peak occurring simultaneously in visual areas

Where the brain decides how much we are willing to pay.

Plassmann et al. show some brain correlates of our willingness to pay:

An essential component of every economic transaction is a willingness-to-pay (WTP) computation in which buyers calculate the maximum amount of financial resources that they are willing to give up in exchange for the object being sold. Despite its pervasiveness, little is known about how the brain makes this computation. We investigated the neural basis of the WTP computation by scanning hungry subjects' brains using functional magnetic resonance imaging while they placed real bids for the right to eat different foods. We found that activity in the medial orbitofrontal cortex and in the dorsolateral prefrontal cortex encodes subjects' WTP for the items. Our results support the hypothesis that the medial orbitofrontal cortex encodes the value of goals in decision making.
Neural correlates of WTP. A, B, Activity in the medial OFC and the DLPFC was positively correlated with WTP at the time of evaluation in the free trials more than in the forced trials.

What the F***?

An article by Steven Pinker on cursing.

Google's evil eye....

...thought I would link you to this interesting article.

Radiohead - the modern troubadours?

An article in the Arts section of today's NY Times temporarily stirred me out of my curmudgeonly old fart persona. Just as a federal jury in Minnesota last week decided that a mother found liable for copyright infringement for sharing music online should pay damages amounting to about $9,250 apiece for 24 songs, the British Rock group Radiohead has made their latest album "In Rainbows" available for download, letting their fans decide how much they want to pay for it. This has brought a new climax in the pricing pandemonium in the on-line music industry summed up by Radiohead manager Bryce Edge:

Digital technology has reintroduced the age of the troubadour. You are worth what people are prepared to give you in the digital age because they can get it for nothing.

In another departure from convention:

...the band declined to send out early copies of the music for reviewers and has not settled on a traditional single to push to radio stations. As a result, programmers are improvising. In San Francisco, for instance, the rock station KITS-FM, Live 105, has the entire album on its Web site (live105.com) and will let fans vote to determine which songs merit airplay.

I just checked out this site, and proceeded to buy and download the new album.

See-through frog...

Just the thing for a budding young scientist's holiday stocking...From the Oct. 3 issue of Nature Magazine:

Japanese biologists have created what they call the world's first see-through creature with four legs. (Some fish are naturally transparent.) The frogs started out as ordinary Japanese brown frogs (Rana japonica ), but crossing animals with recessive genes for light-coloured skin led to transparency. Internal organs, eggs and other normally concealed innards are all on full display in the new amphibian (pictured). Its creator, Masayuki Sumida of Hiroshima University, plans to seek a patent, according to the AFP news agency.

How we see over 10,000-fold changes in light intensity

The first 35 years of my professional life were spent studying the excitation and adaptation of photoreceptor cells. This motivates me to point out a beautiful piece of work by Dunn et al. showing how different circuits in the retina collaborate to let us see over an amazingly wide range of environmental light intensities. Here is their abstract, and figures from the paper showing the cells involved:

We see over an enormous range of mean light levels, greater than the range of output signals retinal neurons can produce. Even highlights and shadows within a single visual scene can differ approximately 10,000-fold in intensity—exceeding the range of distinct neural signals by a factor of approximately 100. The effectiveness of daylight vision under these conditions relies on at least two retinal mechanisms that adjust sensitivity in the approximately 200 ms intervals between saccades. One mechanism is in the cone photoreceptors (receptor adaptation)and the other is at a previously unknown location within the retinal circuitry that benefits from convergence of signals from multiple cones (post-receptor adaptation). Here we find that post-receptor adaptation occurs as signals are relayed from cone bipolar cells to ganglion cells. Furthermore, we find that the two adaptive mechanisms are essentially mutually exclusive: as light levels increase the main site of adaptation switches from the circuitry to the cones. These findings help explain how human cone vision encodes everyday scenes, and, more generally, how sensory systems handle the challenges posed by a diverse physical environment.

Figure 1: Midget and parasol ganglion cells adapt at lower backgrounds than L cones. Schematic of primate midget and parasol pathways with fluorescent images of cones in slice and ganglion cells in flat mount.

Figure 2: Post-receptor adaptation occurs in signal transfer from cone bipolar cells to ganglion cells. The figure shows fluorescent images of a midget cone bipolar cell (left panel) and a diffuse cone bipolar cell (right panel) in slice. OPL, outer plexiform layer; INL, inner nuclear layer; IPL, inner plexiform layer.

The wireless epidemic

Jon Kleinberg, best known for his work on web searching that paved the way for Google and the rest, writes on the threat posed by computer viruses and worms in our increasingly 'wireless' age, concluding that biological models of virus transmission are increasingly relevant for assessing the emerging threat. Here are a few clips:

Traditionally, computer viruses have propagated on networks that bear little resemblance to the networks of physical contact through which their biological counterparts spread. But a growing body of research shows that the increasing use of short-range wireless communication networks might cause the two models to converge....Diseases in plant populations, or animal diseases such as rabies, are heavily constrained by geographical proximity and the relatively fixed physical locations of the infected individuals. Models of these diseases have been extended using detailed data on patterns of travel within cities and by air worldwide in attempts to analyse disease outbreaks in human populations...Epidemics on the Internet are even more diverse. At the most general level, there is a distinction between computer viruses, which 'piggyback' on data exchanged between users, and computer worms, which more actively direct their own transmission through a network...

Very roughly.. one could view models of biological epidemics as rooted in spatial networks, and expanding into less spatial realms to model the technologies that have accelerated human travel. Meanwhile, research on cyber-epidemics has occupied the non-spatial end of the spectrum, with its diverse and far-flung connections, when modelling global communication technologies such as the Internet.

..the spread of short-range wireless communication technologies such as Bluetooth, and the emergence of worms that exploit these systems is disrupting this dichotomy by making possible computer-virus outbreaks whose progress closely tracks human mobility patterns. These types of wireless worm are designed to infect mobile devices such as cell phones, and then to continuously scan for other devices within a few tens of metres or less, looking for new targets. A computer virus thus becomes something you catch not necessarily from a compromised computer halfway around the world, but possibly from the person sitting next to you on a bus, or at a nearby table in a restaurant.

In assessing the risks of such attacks, and developing countermeasures against them, it is intriguing to contemplate how we might draw on expertise from the field of human epidemiology in understanding how contagion spreads...Analogies to biological epidemics can also be exploited for beneficial purposes, in the design of computer-network protocols. For mobile devices, epidemiology helps in dealing with the problem of intermittent connectivity: that the routing of traffic must conform to a dynamic and unpredictable network structure as the owners of mobile devices move around. The result is a growing interest in opportunistic routing, in which messages are passed between devices that come into physical proximity, with the goal of eventually reaching a specified recipient. The development of such protocols has drawn on detailed data concerning human mobility and contact patterns.

An acetylcholine receptor agonist improves cognition

The alpha-7 nicotinic acetylcholine receptor (nAChR) plays an important role in cognitive processes and may represent a drug target for treating cognitive deficits in neurodegenerative and psychiatric disorders. Bitner et al. study the effects of a particular AChR enhancer, or agonist, whose simple name is A-582941.

The figure shows the general structure of this class of molecules. A-582941 enhanced cognitive performance in behavioral assays including the monkey delayed matching-to-sample, rat social recognition, and mouse inhibitory avoidance models that capture domains of working memory, short-term recognition memory, and long-term memory consolidation, respectively. Their results demonstrate that alpha-7 nAChR agonism can lead to broad-spectrum efficacy in animal models at doses that enhance ERK1/2 (extracellular-signal regulated kinase) and CREB (cAMP response element-binding protein) phosphorylation/activation and may represent a mechanism that offers potential to improve cognitive deficits associated with neurodegenerative and psychiatric diseases, such as Alzheimer's disease and schizophrenia.

Most Viewed MindBlog posts...

I occasionally check Feedburner.com to observe web traffic to this blog, and pulled up the following list of most viewed posts. The left column indicates the number of views and the right indicates clicks on links in the post. Entering a few words of the title in the "Search MindBlog" box gets you to a given post...

Non-materialist neuroscience

Here is an discussion on what the authors call the latest installment of the war on science. From their introduction:

Non-materialist neuroscience is the latest front in the war on science. The battle has been a long time coming and it is surprising it has taken so long to get going. Modern neuroscience is rapidly reducing much of human thought, emotion and behavior into component pieces of neuronal interactions. The combination of computational modeling and non-invasive imaging of living brains has allowed researchers to begin describing how complex thought emerges from the firing patterns of neurons. In a way neuroscience is the death knell of dualism. When materialist causes become both necessary and sufficient to explain all of human thought then parsimony dictates that references to a soul or other supernatural entities can be tossed out.

Non-materialist neuroscience is a reaction to these discoveries, a rallying cry for dualism. Like creationism and intelligent design this "new" neuroscience is a reactionary movement against science. Rather than a hypothesis that leads to predictions and experiments, it is simply a catalog of things modern neuroscience supposedly cannot yet explain.

Unsurprisingly, the movement is spear-headed by intelligent design lackeys from the Discovery Institute and related affiliates. The primary proponents of the movement are Michael Egnor, a neurosurgeon and recent contributor to the Discovery Institute blog, Denyse O'Leary a Canadian "journalist" who runs her own blog dedicated to non-materialist neuroscience and likes to copy and paste these entries over on William Dembski's blog as well, and Mario Beauregard the author with O'Leary of a recent book on the subject of non-materialist neuroscience The Spiritual Brain: A Neuroscientist's Case for the Existence of the Soul.

Musicians have enhanced subcortical processing

Musical training is known to modify cortical organization. Musacchia et al. show that:

...such modifications extend to subcortical sensory structures and generalize to processing of speech. Musicians had earlier and larger brainstem responses than nonmusician controls to both speech and music stimuli presented in auditory and audiovisual conditions, evident as early as 10 ms after acoustic onset. Phase-locking to stimulus periodicity, which likely underlies perception of pitch, was enhanced in musicians and strongly correlated with length of musical practice. In addition, viewing videos of speech (lip-reading) and music (instrument being played) enhanced temporal and frequency encoding in the auditory brainstem, particularly in musicians. These findings demonstrate practice-related changes in the early sensory encoding of auditory and audiovisual information.

Do you need more hassles?

Try out this.

Some rambling on "Selves" and "Purpose"

The recent posts on Alwyn Scott and the Blakesless' book prompt me to this random walk....

Self conscious "Purpose" of the sort we humans experience, in the service of crafting new political movements or environments, is an evolved psychology that (sometimes) helps pass on our genes, and requires our distinctively human self reflective "I". Our behavior and that of other animals also reflects a kind of purpose that has been formed by our evolutionary and developmental history. In other animals such behaviors are acted out on the cusp of an eternal present - there is no evidence that they "know that they know" in the way that we can.

Both modern neuroscience (cf. the quote from the Blakesless' book) and Buddhist psychology inform us that the self and the purpose that each of us experiences is an illusion or confabulation of our brains - hopefully a useful one - whose utility is tested by how it enhances our energy and individual survival. This 'illusion' is a powerful instrument of downward causation, regulating our psychological, immune, neuro-endocrine robustness.

What is especially amazing is that our human body/brain can sometimes use meditative or other techniques to bootstrap to a level of metacognition that rests antecedent to - and can be the detached observer of - the generation of this illusion of a self and its purposes.

The maximum power of our self illusion, for most of us, goes with our heartfelt immersion and belief in it (i.e., our delusion). From such a immersion, it can be more difficult to discern or appreciate the different selves and purposes of other humans, and their cultures and historical eras.

Rich and Poor

San Paulo, Brazil.

Playing Action Video Games Reduces Gender Differences in Spatial Cognition

From Feng, Spence, and Pratt (PDF here):

We demonstrate a previously unknown gender difference in the distribution of spatial attention, a basic capacity that supports higher-level spatial cognition. More remarkably, we found that playing an action video game can virtually eliminate this gender difference in spatial attention and simultaneously decrease the gender disparity in mental rotation ability, a higher-level process in spatial cognition. After only 10 hr of training with an action video game, subjects realized substantial gains in both spatial attention and mental rotation, with women benefiting more than men. Control subjects who played a non-action game showed no improvement. Given that superior spatial skills are important in the mathematical and engineering sciences, these findings have practical implications for attracting men and women to these fields.

From their article:

The experimental group was trained using Medal of Honor: Pacific Assault, which was chosen because it is similar to the games typically played by players in Experiment 1 [note: which compared students based on their self reports of game use] and because it has been used before in attention training studies. This game is a 3-D first-person shooter game that requires intense visual monitoring and attentional resources. The control group played Ballance, a 3-D puzzle game that involves steering a ball through a hovering maze of paths and rails with obstacles such as seesaws, suspension bridges, and pendulums.

Plasticity and learning in the human mirror neuron system

I pass on a review by Welberg of an interesting study by Catmur et al. [Catmur, C., Walsh, V. & Heyes, C. Sensorimotor learning configures the human mirror system. Curr. Biol. 17, 1527–1531 (2007)]:

Neurons in the frontoparietal mirror system fire when one performs an action and when one observes someone else performing that same action. This system is thought to have a role in social cognition and, perhaps, in language acquisition. How the mirror neurons map sensory input onto its motor representation is unknown, but Catmur et al. demonstrate that these representations are not innate and can be altered by training.

The authors used transcranial magnetic stimulation (TMS) to stimulate the motor cortex of volunteers who were watching a video of a hand. When the volunteers watched the hand's index finger move, the TMS-induced motor-evoked potential (MEP) was greater in the abductor muscle of their own index finger than when they watched the little finger move; conversely, the MEP of their little finger's abductor muscle was greatest when they watched the little finger move. In other words, a muscle showed MEP enhancement when its owner watched a movement that is normally performed by that muscle; this 'mirror effect' is thought to reflect activity of the mirror neuron system.

Half of the volunteers then underwent incongruent training trials, in which they were asked to extend their little finger if the video showed a hand extending the index finger, and vice versa. People in congruent trials simply had to repeat the movement they saw in the video. The incongruent trials were assumed to train the mirror system to associate an observed finger movement with movement of a different finger of the volunteer's own hand.

Measuring TMS-induced MEPs after training, the authors found that volunteers who had undergone the incongruent training now showed greater MEPs in the muscle of one finger when watching the 'wrong' finger move in the video, indicating that a reversal of muscle-specific MEP enhancement during action observation had taken place.

This study shows that the 'mirror properties' of the mirror system are not innate. Rather, they can be trained, through sensorimotor experience, to transform observation into action. These findings imply that insufficient social interaction and consequent inadequate sensory experience might affect the development of the mirror neuron system, for example, in children with autism.

New research on ageing

Nature Magazine offers a special open access supplement with several excellent articles on recent research on ageing. Also, they offer to send a free print copy.

Striking Images....

Here are the first place winners of Science Magazine's 2007 Visualization Challenge, in which editors evaluate submissions that try to bring scientific data to life through images, illustrations, computer graphics, and animations. In the first, 182 thin CT "slices" are stacked together to create a 3D image looking upward at the sinuses from underneath the head. In the second, Irish ocean moss is spread out for photography.