On Purpose

"When Henry Fawcett commented to Charles Darwin that some scientists found Darwin too theoretical and believed that he should just let the facts speak for themselves, Darwin responded: 'How odd it is that anyone should not see that all observation must be for or against some view if it is to be of any service.'³"

This quote is taken from a review in Science magazine of cognitive neuroscientist Paul Thagard's book: The Brain and the Meaning of Life^1,2. I found the review intriguing, particularly the section which comment's on Thagard's attempts to use a scientific point of view to answer the question: "What kind of government should countries have?"

However, I reproduced the quote, above, because it struck a chord in my mind. To my mind, Darwin's viewpoint discards the great utility and pleasure that one may find in observation for the sake of observation. That is, scientific exploration. It is not always possible to observe, to collect information with a hypothesis in mind, and such exploratory behavior can inspire hypotheses or new avenues of scientific discovery. How limiting to always approach a situation with a theory, a reason, a preconception.

In fact, I don't believe that Darwin was suggesting anything so strong as to eliminate exploration from one's methods, his own travels as a young man were likely not begun with a plan of attack to corroborate his grandfather Erasmus' evolutionary theory, though this was the end result. However, science in the present day is extraordinary goal oriented; every scientist must compete for funding and the drive to present completed work is thus ever present. There is something romantic and collaborative in the idea that some men of science in Darwin's age wanted the facts to "speak for themselves."

Collaboration is something that we can always use more of.

References
1. Shermer, M (2010) Meaning-Making Neurons. Science, 328: 693-694; DOI: 10.1126/science.1189752
2. Thagard, Paul. The Brain and the Meaning of Life. Priceton: Princeton University Press.
3. Letter, C. R. Darwin to H. Fawcett, 18 September 1861; www.darwinproject.ac.uk/entry-3257.

On Goals / (I'm back)

Freeman Dyson's piece on Steven Weinberg's recently published collection of writings was a beautiful and informative exploration of science, history, and politics^1,2. One quote, about the differing goals of the Russian and American space programs, struck me in particular. Perhaps I found it so intriguing because it highlights a an ever-present conflict in my own life: short-term vs. long-term goals. An excerpt:

"[American] unmanned missions to explore the planets and stars and galaxies have made us truly at home in the universe, while our manned missions after the Apollo program to land on the moon have been scientifically fruitless. Forty years after Apollo, the manned program is still stuck aimlessly in low orbit around the earth, while politicians debate what it should try to do next.

...In Russia you do not go into space to do science. You go into space because it is a part of human destiny... Konstantin Tsiolkovsky, the schoolteacher who worked out the mathematics of interplanetary rocketry in the nineteenth century, said, “The earth is the cradle of the mind, but we cannot live forever in a cradle.” It may take us a few centuries to get to the planets, but we are on our way. We will keep going, no matter how long it takes.

If you think as Americans do, on a time scale of decades, then unmanned missions succeed and manned missions fail. The grandest unmanned missions, such as the Cassini mission now exploring the satellites of Saturn, take about one decade to build and another decade to fly. The grandest manned mission, the Apollo moon landing, ended after a decade and could not be sustained. The time scale of a decade is fundamentally right for unmanned missions and wrong for manned missions. If you think as Russians do, on a time scale of centuries, then the situation is reversed. Russian space science activities have failed to achieve much because they did not concentrate their attention on immediate scientific objectives. Russian manned mission activities, driven not by science but by a belief in human destiny, keep moving quietly forward. There is room for both cultures in our future. Space is big enough for both." (my emphasis)

Here's to moving quietly forward.

References
1. Dyson, F. (2010) What Price Glory?, The New York Review of Books LVII-10: 8-12
2. Weinberg, Steven. Lake Views: This World and the Universe, Belknap Press/Harvard University Press.

On Snake Walking

(from reference 1)


Human beings transition between from one style of gait to another as they transition from walking to running (see figure, above). The act of walking is fundamentally one of transferring weight from one limb to another, while running is primarily an act of maintaing inertia. Furthermore, these two gaits apparently have their origin in the minimization of energy costs associated with moving at a particular speed¹.



(from reference 2)


Interestingly, it seems that snakes do not make any such transition in their locomotive behavior. A study appearing in the Proceedings of the National Academy of Sciences has used theoretical modeling, friction measurements, and slithering-observations to demonstrate that snakes simply "speed-walk" at high speeds ². Although they have no limbs, and thus no "gait" to speak of, at slow speeds, they do move about by transferring weight from one part of their body to another. In contrast to other animals, however, they do the same thing, only faster, at high speeds. It is unclear why speedwalking is not an undue energetic costs for these animals, perhaps there is simply no less-costly way to move about. Further work will be needed to more completely understand the energetics of snake locomotion.

References:
1. Srinivasan M, Ruina A. (2006) Computer optimization of a minimal biped model discovers walking and running. Nature. 439(7072): 72-75.
2. Hu DL, Nirody J, Scott T, Shelley MJ. (2009) The mechanics of slithering locomotion. Proc Natl Acad Sci U S A. [Epub ahead of print]
PMID: 19506255 [PubMed - as supplied by publisher]

On The Tree-for-the-Forest in Autism

One commonly reported feature of autism-spectrum-disorder (ASD) is the tendency to favor details over whole-object properties. That is, to notice the forest and not the trees. A study appearing in the journal Vision Research quantifies this effect experimentally¹.

The authors of this study relied on a concept known as "visual crowding." This term refers to a commonly experienced phenomenon in which objects that are spaced closely together are more difficult to individually attend to or resolve. For example, some have invoked this idea to explain why it is difficult to pick individual faces out of a crowd. It is important to note, that there is a spatial-scale, a threshold, associated with visual crowding, such that objects of a given size must be spaced within some distance limit to be considered within the crowding limit (although some objects are so large that they are immune to such effects).

from reference 1

Interestingly, the authors found that children with ASD had much lower thresholds for visual crowding than those without the disorder (see figure, above). That is: those with ASD were able to resolve and report the properties of more densely packed objects than those without ASD. Furthermore, children with ASD out-performed non-ASD children in the employed task within the crowding limit (as defined by the threshold for non-ASD children) while underperforming outside this limit.

Such a finding suggests structural irregularities in the visual-corticies of these children; while this is nothing special in and of itself, there are many different cortical areas which are affected by ASD, which leads to the intriguing possibility (suggested by many) that the disorder might be a generalized structural deficit of the cerebral cortex.

References:
1. Baldassi S, Pei F, Megna N, Recupero G, Viespoli M, Igliozzi R, Tancredi R, Muratori F, Cioni G, Search superiority in autism within, but not outside the crowding regime, Vision Research, In Press, DOI: 10.1016/j.visres.2009.06.007.

On Leanness

Although many acknowledge that some people are inherently (perhaps genetically) leaner than others, it remains unclear what the biological basis for the body's "set-point" might be. A study appearing in the open-access journal PLoS One suggests one possible factor¹.


from reference 1

Both rat and human data were collected in this work, which concludes that "the lean phenotype is characterized by high endurance capacity and high activity and may stem from altered skeletal muscle energetics." These researchers gathered data from a population of people who they categorized as non-exercisers (less than 1 hour per week of activity exceeding 4 METS). They subjected these individuals to a treadmill test to determine their endurance (as assessed by oxygen consumption during exercise) and kept track of their average daily activity over a period of 10 days; finding that there was a significant relationship between endurance and leanness, as well as average daily activity and leanness. Furthermore, they found that there was no significant difference in the amount of food consumed by lean versus non-lean rats, and fascinatingly, that the skeletal muscle tissue of lean rats has significantly higher levels of the enzyme PEPCK-C.

Of course, it is not surprising that those individuals with higher daily activity are leaner in general, rather, this study is suggesting that there may be a fundamental, biological reason why certain individuals are more active: they simply have a greater capacity for activity. Indeed, if one fatigues more easily, it wouldn't be surprising if they were less active; it is also conceivable that reduced activity could feed-back on behavior in the sense that an individual with lower endurance might progressively reduce the amount of physical activity they engage in so as to reserve energy for other tasks. This is especially true in contemporary society, where mental activity is often the basis for work and play.

It is unclear as yet, however, whether the differential muscle-properties found in rats extend to humans; further work will be required to clarify what the molecular-biological basis for increased human endurance might be.

References
1. Novak CM, Escande C, Gerber SM, Chini EN, Zhang M, et al. (2009) Endurance Capacity, Not Body Size, Determines Physical Activity Levels: Role of Skeletal Muscle PEPCK. PLoS ONE 4(6): e5869. doi:10.1371/journal.pone.0005869

On Feedback

One of the most fascinating questions in neuroscience, is how "high-level" cognitive properties of mind like attention feed back on and affect our biology. For example, it is known that video-game players have better visual acuity than non-video game players¹. Another example of this phenomenon can be found in the result (described below) from Lee et. al., published in the Journal of Neuroscience².


from reference 2

The authors of this study found differences in the responses of the auditory brainstems of musicians as compared to non-musicians. Specifically, these two groups (musicians and non-musicians) were presented with pairs of consonant and dissonant tones; it was found that musicians showed larger response magnitudes to certain components of consonant tones than did non-musicians (see figure, above).

The hypothesized reason for this difference is that a musician's heightened attention to consonant tones (and their makeup or properties) leads to changes in his or her neurobiology, such that the neurons of the auditory brainstem eventually respond more strongly to certain aspects of these auditory signals. This is especially fascinating because the area of the brain that was measured was not the cortex (usually associated with consciousness and "high-level" cognitive activity), but the brainstem (the area of the brain that is evolutionarily much older; bearing greater resemblance to animal brains ).

How the conscious act of focusing on one aspect of a stimulus can lead to an enhancement of the responses of brain-regions devoted to their representation is an open question, and one with wide-ranging implications. Further research will be required to understand its basis.

References:
1. Green CS, Bavelier D. (2007) Action-video-game experience alters the spatial resolution of vision. Psychol Sci. 18(1):88-94. PMID: 17362383
2. Lee KM, Skoe E, Kraus N, Ashley R. (2009) Selective subcortical enhancement of musical intervals in musicians.
J Neurosci. 29(18):5832-40. PMID: 19420250

On Prefrontal Guilt

The field of Neuroeconomics has become quite popular in recent years. There are several reasons for this surge in interest; amongst these are: (1) the inevitable intrigue generated by scientific considerations of currency, (2) the utility of studying behaviors contingent on well defined rewards and punishments (losses), and (3) the value of scientifically exploring a human behavior that has been studied and theorized about for hundreds of years (namely by economists and others not specifically interested in the neurological bases of these behaviors).

One particularly rewarding research tactic has been the employment of economic games (a subset of those falling under the heading of game theory, widely associated with the mathematician John Nash). One example of such a game is the following: I (the "house") flip a coin. If it's heads, I pay you a dollar. If it's tails, I flip it again. If it's heads on the second toss, I give you 2 dollars. If it's tails, I flip it again. If it's heads on this second toss, I give you 4 dollars, et cetera. Thus, if you get a head on the nth roll, you receive $2ⁿ. The question is: how much would you be willing to pay initially to be a player in this game? Most people are only willing to pay perhaps $10-20 for the privilege, however, statistically (on average), the earnings in this game are infinite. If you play enough times, you will earn an infinite amount of money. This concept was quoted hundreds of years ago to give credence to the notion that when it comes to estimation of value, we operate far from optimally.

This sort of heuristic - describing performance in a prescribed setting - can be rendered quantitative in such a way that an individual's decision making in a particular game can be used to estimate parameters about their over-all behavior: how risk-averse they are, how benevolent, and even how likely they are to feel guilty.




A paper appearing in the Journal of Neuroscience addresses this last point in the context of relevant brain areas and brain damage. Krajbich et al compared the performance of individuals with certain types of brain damage (along with normal controls) in an economic game. As can be seen in the table above (from their paper), they concluded that those with damage to the prefrontal cortex (PFC) are far less likely to experience feelings of guilt¹.



Those familiar with the story of Phineas Gage may hear the ring of truth in this result. Phineas Gage was a railroad worker responsible for tamping down explosives into holes drilled in pieces of rock, using a long metal rod. During one such episode, the explosives went off, and the rod entered his head below the left eye socket, exiting through the top of the skull and destroying most of his PFC (see image, above). Amazingly, he survived, but with the intriguing effect that his personality changed completely. Before the accident, he was described by his employers as "a great favorite" and "the most efficient and capable foreman in their employ." After the accident, he was so changed that they subsequently "considered the change in his mind so marked that they could not give him his place again." He was furthermore said to be a "braggadocio,and "manifesting but little deference for his fellows, impatient of restraint or advice when it conflicts with his desires, at times pertinaciously obstinate, yet capricious and vacillating.²"

It is likely that the experience of guilt is not the only function of the PFC; it is associated with planning functions and reasoning in general. However, this type of exploration and estimation of the parameters of human behavior is quite novel and powerful, and its utility will only increase as the complexity of our models and understanding of the parameters relevant to the generation of such behaviors increases.

References:
1. Krajbich I, Adolphs R, Tranel D, Denburg NL, Camerer CF. Economic Games Quantify Diminished Sense of Guilt in Patients with Damage to the Prefrontal Cortex. J Neurosci 29: 2188-2192, 2009.
2. Harlow JM. Recovery from the Passage of an Iron Bar through the Head. Pubs Mass Med Soc 2: 327-347, 1868.