Models of cognitive control in prefrontal cortex.

In the May issue of Trends in Cognitive Sciences David Badre reviews different models of the cognitive controls in our prefrontal cortex that support flexible behavior by selecting actions that are consistent with our goals and appropriate for our environment. I thought I would pass on two nice graphics from the papers, showing the structures and models involved. They do make the point that we have a long way to go before figuring out how the system works.

Figure (click to enlarge). Schematic of major anatomical sub-divisions in the frontal lobes. Boundaries and Brodmann areas (BA) are only approximate. Arrows indicate anatomical directions of anterior/rostral (front) versus posterior/caudal (back) and dorsal (up) versus ventral (down). From caudal to rostral, labeled areas include motor cortex, dorsal (PMd) and ventral premotor cortex, dorsal (pre-PMd) and ventral aspects of anterior premotor cortex, ventro- (VLPFC) and dorsolateral PFC (DLPFC), and lateral frontal polar cortex (FPC).


Figure: (Click to enlarge) Theoretical accounts of the rostro–caudal gradient in the PFC. (a) From a working memory perspective, rostral and caudal PFC can be distinguished on the basis of processing domain general versus specific representations. Hierarchical versions of this perspective propose that domain-specific posterior frontal regions can be modulated by the maintenance domain general rules in anterior DLPFC and FPC. (b) Relational complexity proposes a gradient in the PFC with respect to evaluation of simple stimulus properties, first-order relationships among the properties, and second-order relationships among relationships. (c) The cascade model proposes four levels of control that are distinguished by temporally disparate control signals, either sensory, context, episodic or branching. (d) Abstract representational hierarchy proposes that regions of the PFC are distinguished by the level of abstraction at which representations compete in a hierarchy of action representations.

Music becoming a monoculture...

David Huron writes an interesting essay in the May 22 issue of Nature noting the fact that as millions of musical recordings have become available over the web, there has been a

...collapse in the diversity of musical minds. A Nigerian group might sing in Yoruba, but the harmonies are thoroughly Western. Native American Navajo singers make valiant efforts to preserve their traditions, but to the trained musicologist, their singing bears the unmistakable imprint of Western scales. The casual listener hears a wealth of variety; the musicologist detects a rapidly spreading monoculture — albeit expressed in many forms.
...Linguists know how fast languages disappear. Musical cultures may be an order of magnitude more fragile. It will be many centuries before the whole world speaks Mandarin. Meanwhile Western music has swept the globe faster than aspirin. Robust musical cultures remain in China, India, Indonesia and the Arab world, but even in these regions, most people are thoroughly acquainted with Western music through film and television. Less robust musical cultures are disappearing rapidly or are showing deep infiltration by Western musical foundations. Many have already disappeared. There remain only a few isolated pockets, such as the highlands of Papua New Guinea and Irian Jaya.

What and Where pathways in auditory brain

The visual cortex has parallel processing streams that deal mainly either with the location of an image (the dorsal stream) or its identity (the ventral stream). It now appears that auditory cortex (in cats) has similar parallel processing of the location and identity of sounds. Here is the abstract from Lomber and Malhotra and a graphic from the summary by Sumner and Moore.

Studies of cortical connections or neuronal function in different cerebral areas support the hypothesis that parallel cortical processing streams, similar to those identified in visual cortex, may exist in the auditory system. However, this model has not yet been behaviorally tested. We used reversible cooling deactivation to investigate whether the individual regions in cat nonprimary auditory cortex that are responsible for processing the pattern of an acoustic stimulus or localizing a sound in space could be doubly dissociated in the same animal. We found that bilateral deactivation of the posterior auditory field resulted in deficits in a sound-localization task, whereas bilateral deactivation of the anterior auditory field resulted in deficits in a pattern-discrimination task, but not vice versa. These findings support a model of cortical organization that proposes that identifying an acoustic stimulus ('what') and its spatial location ('where') are processed in separate streams in auditory cortex.

Legend: The effects of cooling posterior and anterior regions of auditory cortex are doubly disassociated, with anterior regions being important for discriminating between sounds and posterior parts being important for localizing them.

Meeting George Bush versus Meeting Cinderella

The rest of the title of this article by von Cramon and Schubotz is "The Neural Response When Telling Apart What is Real from What is Fictional in the Context of Our Reality." Our ability to distinguish fact from fiction emerges early during our development, and by the age of 5, we not only differentiate reality from fiction but can also distinguish between different fictional worlds. The neural correlates underlying this ability are unknown. The authors obtain fMRI images showing significant difference in brain activity while processing real versus fictional conditions. The graphic is from the paper just to include a pretty picture, I'll spare you the details, because they really don't add all that much to the bottom line:

The processing of real and fictional scenarios activated a common set of regions including medial-temporal lobe structures. When the scenarios involved real people, brain regions associated with episodic memory retrieval and self-referential thinking, the anterior prefrontal cortex and the precuneus/posterior cingulate, were more active. In contrast, areas along the left lateral inferior frontal gyrus (shown in the graphic), associated with semantic memory retrieval, were implicated for scenarios with fictional characters. This implies that there is a fine distinction in the manner in which conceptual information concerning real persons in contrast to fictional characters is represented. In general terms, the findings suggest that fiction relative to reality tends to be represented in more factual terms, whereas our representations of reality relative to fiction are colored by personal subjectivity. What modulates our understanding of the relative difference between reality and fiction seems to be whether such character-type information is coded in self-relevant terms or not.

The authors note their agreement with the statement of William James: "In the relative sense, then, the sense in which we contrast reality with simple unreality, ... reality means simply relation to our emotional and active life

Older adults have a broader attention span

An article by Reistad-Long describes studies suggesting that a broader attention span may enable older adults to ultimately know more about a situation and the indirect message of what’s going on than their younger peers. For example, older people take longer to read passages that are interrupted with unexpected words or phrases, but are more likely to be successful at answering questions for which the out-of-place words might be answers. This might yield advantages in the real world, where it is not always clear what information is important, or will become important. Maybe we think of older people as wiser because they take in more information from a situation, and are able to combine it with a comparatively greater store of general knowledge.

Lotus therapy

Yet another article on benefits of mindfulness meditation in this morning's NYTimes science section.

Blogging as self-medication

Maybe I've found one of the reasons I do this blog (other than to keep me off the streets): An article by Jessica Wapner in the June issue of Scientific American discusses studies on the therapeutic value of blogging. Blogging is claimed to provide physiological benefits similar to those that have been shown for expressive writing (serving as a stress-coping mechanism, improving memory and sleep, and boosting immune cell activity.) Blogging may act as a "placebo for getting satisfied." The blogosphere offers an antidote to social isolation. (Checking out my 'mdbownds' YouTube video postings reveals that the Debussy Reverie video has been viewed 98,739 times and 157 comments made; this mindblog gets 500-600 visitors each day. While this is social connection, I totally don't know any of you people, except for a handful of friends.) I find fleeting virtual world contacts a pallid substitute for real life huggable friends, and sometimes fret that my time spent hunkering over a keyboard provides too convenient an excuse for the harder work of being a robust member of real (versus virtual) social groups.

Another reason for being gay?

Ever alert for the latest speculation on a possible biological basis for why I might be gay, I come across this little gem on fruitflies: genetic manipulation that enhances dopamine levels in males makes them more likely to court with other males.

A Chopin Nocturne...

Chopin Nocturne Op. 27 No. 2, recorded on my Steinway B at Twin Valley.

For your memorial day holiday hangover

Check out this article by Joan Acocella in the May 26 issue of The New Yorker, "A Few Too Many - Is there any hope for the hung over?"

Tones of Ancient Greece

I found this brief commentary from "Random Samples" in the May 16 issue of Science so interesting that I wanted to pass it on in its entirety:

The strings of a helikon, a gadget invented by Ptolemy to probe musical scales, sounded last week for the first time in almost 2 millennia at the University of Cambridge in the U.K....Andrew Barker, a musicologist at the University of Birmingham, U.K., built the instrument from a description in Harmonics, Ptolemy's 2nd century treatise on the mathematics of music. Ancient scholars considered the study of harmonics vital in understanding the mathematical rules that they believed governed the universe. He unveiled it as part of Cambridge's Science of Musical Sound Project.

Barker says the 1-meter-long wooden instrument with eight metal strings allows scientists to test "complete scales constructed on the basis of mathematical principles." The helikon creates different pitches with a calibrated sliding bridge, which can be inserted diagonally to shorten strings to different lengths. Strings can also be moved crosswise to raise or lower the range of pitches. Barker, who showed how the adjustments produce different intervals when the gadget is plucked, admits that it's not designed for musicmaking. Still, he says he was delighted that it worked at all.

Cambridge historian Torben Rees, a professional jazz singer, called Barker's presentation "a fascinating account of ancient thinking concerning harmonics." Music, he says, was regarded as "the sensible expression of the order of the cosmos. This conception of the universe … was essentially the birth of mathematical physics."

Most popular consciousness papers

Here is the list of the five most downloaded papers from the ASSC archive for April, 2008:

1. Destrebecqz, Arnaud and Peigneux, Philippe (2005) Methods for studying
unconscious learning. In: Progress in Brain Research. Elsevier, pp. 69-80.
1877 downloads from 23 countries. http://eprints.assc.caltech.edu/170/
2. Koriat, A. (2006) Metacognition and Consciousness. In: Cambridge handbook
of consciousness. Cambridge University Press, New York, USA. 1297 downloads
from 23 countries. http://eprints.assc.caltech.edu/175/
3. Dehaene, Stanislas and Changeux, Jean-Pierre and Naccache, Lionel and
Sackur, Jérôme and Sergent, Claire (2006) Conscious, preconscious, and
subliminal processing: a testable taxonomy. Trends in Cognitive Science, 10
(5). pp. 204-211. 880 downloads from 16 countries.
http://eprints.assc.caltech.edu/20/
4. Sagiv, Noam and Ward, Jamie (2006) Crossmodal interactions: lessons from
synesthesia. In: Visual Perception, Part 2 - Fundamentals of Awareness:
Multi-Sensory Integration and High-Order Perception. Progress in Brain
Research, Volume 155. Elsevier, pp. 259-271. 868 downloads from 13
countries. http://eprints.assc.caltech.edu/224/
5. Tsuchiya, Naotsugu and Koch, Christof (2005) Continuous flash suppression
reduces negative afterimages. Nature Neuroscience, 8 (8). pp. 1096-1101. 762
downloads from 13 countries. http://eprints.assc.caltech.edu/35/

Are you a morning person? - mood and body clocks

From from PJH at editor's choice, Science Magazine.

Some neurotransmitters, such as dopamine, have been implicated in adjusting a person's mood. The circadian clock mechanisms, meanwhile, keep the organism's physiology tuned for appropriate responses to day or night. Hampp et al. have demonstrated how the molecular signaling pathways for circadian rhythms might intersect with the brain's establishment of general mood. They found that the promoter of the gene encoding monoamine oxidase A (Maoa), which stabilizes some aspects of mood and breaks down dopamine and serotonin, contains binding sites for several clock proteins and showed that circadian oscillation was driven by the Maoa promoter in neuroblastoma cells. Mice lacking Per2, a gene that stabilizes circadian rhythms, showed damped expression from the Maoa promoter. Observations of the Per2 mutant mice in response to an unavoidable problematic situation--taken as a proxy for despair in humans--showed correlations with disorders of mood.

Tranquility...

A MindBlog reader suggests that I pass along this link on "50+ Simple 30-Second Ways to Bring Tranquility To Your Life"... Hmmmm, good luck.

Brain imaging of belief, disbelief, and uncertainty

A fascinating fMRI study by Sam Harris and colleagues has used functional magnetic resonance imaging (fMRI) to study the brains of 14 adults while they judged written statements to be true (belief), false (disbelief), or undecidable (uncertainty). (Yes, this is the same Sam Harris who wrote "The End of Faith" and "Letter to a Christian Nation."). To characterize belief, disbelief, and uncertainty in a content-independent manner, they included statements from a wide range of categories: autobiographical, mathematical, geographical, religious, ethical, semantic, and factual. They show that belief, disbelief, and uncertainty are mediated primarily by regions in the medial PFC, the anterior insula, the superior parietal lobule, and the caudate. The acceptance and rejection of propositional truth-claims appear to be governed, in part, by the same regions that judge the pleasantness of tastes and odors.

...the final acceptance of a statement as true or its rejection as false appears to rely on more primitive, hedonic processing in the medial prefrontal cortex and the anterior insula. Truth may be beauty, and beauty truth, in more than a metaphorical sense, and false propositions may actually disgust us.
...When compared with both belief and uncertainty, disbelief was associated in our study with bilateral activation of the anterior insula..., a primary region for the sensation of taste. The anterior insula has been regularly linked to pain perception and even to the perception of pain in others. This region, together with left frontal operculum (also active in the contrast disbelief - belief), appears to mediate negatively valenced feelings such as disgust. Studies of olfaction have shown that the left frontal operculum is engaged when subjects are required to make active judgments about the unpleasantness of odors. Thus, regions that have been regularly implicated in the hedonic appraisal of stimuli, often negative, appeared in our study to respond preferentially when subjects rejected written statements as false. Our results appear to make sense of the emotional tone of disbelief, placing it on a continuum with other modes of stimulus appraisal and rejection.
...Several psychological studies appear to support Spinoza’s conjecture that the mere comprehension of a statement entails the tacit acceptance of its being true, whereas disbelief requires a subsequent process of rejection...Understanding a proposition may be analogous to perceiving an object in physical space: We seem to accept appearances as reality until they prove otherwise...subjects assessed true statements as believable faster than they judged them as unbelievable or undecidable. Further, because the brain appears to process false or uncertain statements in regions linked to pain and disgust, especially in judging tastes and odors, this study gives new meaning to a claim passing the “taste test” or the “smell test.”

MindBlog becomes a drop-out student at a brain enhancement site

When the folks at happy-neuron.com offered me a free log in to check out their brain enhancement/preservation exercises I said "Sure, I'll try it out and do a review." The site offers a brief discussion of the science of brain fitness is offered, and the scientific contributors have reasonable credentials. Several have associations with gerontology and aging programs, as is the case with other brain enhancements sites. The single study I was pointed to testing the effects of the happy-neuron exercises was a pilot effort carried out by Robert Bender, a geriatrics and family practice physician in Des Moines, Iowa. He did not respond to my email requesting information on the study.

Well.... to do a proper review one really has to get into it, and I tried, but simply was unable to do this. One could just pick directly from ~ 35 classic style tests (of memory, attention, language, executive function, and visual spatial skills) with a thin video game veneer, or let a "coach" present you with 20 minutes worth of exercises. I chose the "coach" option which chooses exercises for you, monitors your progress, strengths and weaknesses, etc. (It didn't tell me what my strengths and weaknesses were, but perhaps I didn't stick with it long enough for it to get back to me...) The exercises were mildly engaging and indeed left me feeling 'brain tired' after 20 minutes. I did get a bit tired of variations on the towers of Hanoi game (classic form, then basket balls in hoops, then bells in cathedral towers, etc.) I found the 'exit' or 'next' buttons sometimes blanked out or froze the browser window.

I found it difficult to get hooked on the system in a daily basis (I came along before the video game revolution on which my kids were raised). The exercises soon took on an "eat your spinach" aspect. I suspect my motivation might have been greater to pursue them if had been accumulating more striking evidence of my own impending cognitive decline.

I did find it very interesting to pursue the exercises to the point of brain fatigue, which my brain was clearly saying "enough of this, dammit, I'm tired." However, I have not found exercise to the point of fatigue useful or relevant in the daily gym routine to which I am addicted (varying combinations of running, swimming, weights at the Univ. of Wisconsin gym). I feel it would take a similar sort of addiction process to bind me to the routine performance of games like these, and I did not get reinforcement from the "coach" that might have nudged me in that direction ("Hey, you're doing great on executive function and rotating visual images, but your short term memory sucks...")

I may continue to putter with this as well as other brain exercise sites, and if lightning strikes and I get enthusiastic, I'll report back to you.

An aging guide...

Check out the guided tour provided by the NY Times Well.

MRI - the new phrenology

Having just done a posting on MRI, I thought it appropriate to point to a discussion by Michael Shermer in his "Skeptic" column in the Scientific American on the misuse and over-interpretation of MRI data.

It is a reminder that seeing scans with highlighted (usually in red) areas where your brain “lights up” when thinking about X (money, sex, God, and so on) should not seduce us into buying the Swiss Army knife model of the brain, with specialized modules for vision, language, facial recognition, cheating detection, risk taking, spirituality and even God. There is the minor problem of reversing the causal inference:

...where people see some activity in a brain area and then conclude that this part of the brain is where X happens. We can show that if I put you into a state of fear, your amygdala lights up, but that doesn’t mean that every time your amygdala lights up you are experiencing fear. Every brain area lights up under lots of different states. We just don’t have the data to tell us how selectively active an area is.

As Patricia Churchland points out:

Mental modules are complete nonsense. There are no modules that are encapsulated and just send information into a central processor. There are areas of specialization, yes, and networks maybe, but these are not always dedicated to a particular task.” Instead of mental module metaphors, let us use neural networks.

The MRI of morality?

Greg Miller reviews research on the nature of human morality which continues to probe the debate between the views of of David Hume - that emotions drive moral judgments - and Immanuel Kant - who argued that reason should be the driving force. He includes reference to a recent study by Hsu, Anen, and Quartz on equity and efficiency. Some clips, from from the Miller review, and then the Hsu et al paper:

One research group:

...asked dozens of college students to consider several morally charged situations. In one, a friend lies on his résumé to land a job; in another, survivors of a plane crash consider cannibalizing an injured boy to avoid starvation. Students who pondered these hypothetical scenarios while sitting at a filthy desk with sticky stains and a chewed-up pen rated them as more immoral than did students who sat at a pristine desk. In another version of the experiment, a nearby trash can doused with novelty fart spray had a similar effect. The findings...demonstrate that emotions such as disgust exert a powerful influence on moral judgments, even when they are triggered by something unrelated to the moral issue.

Hsu et al. consider distributive justice, illustrated by the following example:

Imagine driving a truck with 100 kg of food to a famine stricken region. The time it would take you to deliver food to everyone would cause 20 kg of food to spoil. If you delivered food to only half the population you would lose only 5 kg. Do you deliver the food to only half the population to maximize the total amount of food, or do you sacrifice 15 kg to help everyone and achieve a more equitable distribution?

They examine the the tradeoff between equity and efficiency, finding:

...that the putamen responds to efficiency, whereas the insula encodes inequity, and the caudate/septal subgenual region encodes a unified measure of efficiency and inequity (utility). Strikingly, individual differences in inequity aversion correlate with activity in inequity and utility regions. Against utilitarianism, our results support the deontological intuition that a sense of fairness is fundamental to distributive justice, but, as suggested by moral sentimentalists, is rooted in emotional processing. More generally, emotional responses related to norm violations may underlie individual differences in equity
considerations and adherence to ethical rules.

Neuroimaging studies have linked several brain regions to moral cognition. Disruptions to the right temporoparietal junction (brown), which is involved in understanding intentions, or the ventromedial prefrontal cortex (green), which processes emotion, have been found to alter moral judgments... activity in the anterior cingulate cortex (pink) may signal conflict between emotion, reflected by activity in the medial frontal gyrus (blue) and other areas (orange, brown), and "cold" cognition, reflected by activity in dorsolateral prefrontal cortex (yellow).

Some Chopin to start the week...

I'm warming up to do some recordings this spring and summer.... this is Chopin's Nocture Op. 9 No. 1