Wednesday, February 25, 2009

Connections: White Matter and Learning

I became interested in the topic of literacy in children while working with a class of 5-6 year olds at the Early Childhood Center on Sarah Lawrence Campus. From the teaching standpoint, this is the age in which the foundations for literacy are laid. There is also evidence that this time is a critical period in brain development. At the ECC, teachers take a “developmental” approach to learning, believing that with encouragement and support children will learn to read at their own pace and in a natural way. Unfortunately, in our society much emphasis is placed on the speed rather than the quality of skills children acquire. As a result, many children who develop more slowly than others are quickly diagnosed with dyslexia or other disorders. How can our knowledge of the brain aid us in our understanding of how children attain literacy? Are there direct correlations between differences in the brain and level of ability? How can our growing knowledge of the structure of the brain influence the way we teach and diagnose children learning to read?
Below I hope to give a brief overview of a study headed by Brian Wandell, chair of the psychology department at Stanford University, which addresses some of these questions.

Previous studies have used brain imaging to establish the connection between the left temporo-parietal cortex and reading ability in adults. Wandell set out to find if this connection applied to children at an age where reading skills are growing rapidly. He and his team hypothesized that similar findings in the structure of white matter in the left temporo-parietal lobe of children would indicate that these neural pathways play integral role in how we develop fluent reading. An alternate hypothesis maintained that if the finding were found to be different between children and adults of varied ability, it could suggest that many years of differential reading experiences could be the cause of structural disparity in adults.

Simply: Does structure define ability? Or Does ability define structure?

Diffusion Tensor Imaging (DTI)
DTI, a form of magnetic resonance imaging, is a significant component of Wandell’s study. While an MRI can give us a good anatomical image in which we can differentiate gray and white matter in the brain, DTI allows researchers to look at the fine tissue structure of white matter. Technically speaking, this nueroimaging method measures the diffusion of water molecules in brain tissue. In simpler terms, DTI allows us to identify and examine different regions of white matter. The direction of the water diffusion gives us insight into the alignment of white matter axons in areas of the brain. Essentially, what we are looking for are the pathways in the brain areas already defined as being responsive during reading and phonological tasks in adults. We assume these pathways also exist in children, what we want to find is if they differ among children of varied reading abilities.

Areas of dense white matter were studied to obtain information about the direction of diffusion, indicating the fiber tracts of white matter demonstrating significant pathways. Fractional Anisotropy (FA) is a measure of direction within a given area or voxel. A high FA value within a voxel would indicate highly directional diffusion. Coherence Index (CI) is used to measure the overall direction of multiple adjacent voxels. High CI would reflect the agreement of fiber direction in neighboring voxels, demonstrating the existence of strong neural pathways.

For their study, the researchers chose 14 children between the ages of 7 and 13, who were by all accounts healthy and normal. These children were classified as either “normal” or “poor” readers based on a series verbal and performance related tests. Among the groups there were no significant differences in ages, genders, parental education of socioeconomic status. Subjects classified as “poor” readers had composite scores that placed them below the 30th percentile in reading. The children in this group had all been previously diagnosed with dyslexia by a psychologist, although it is interesting to note that they also presented varying degrees of deficits in all areas.
Each child received four 3 minute brain scans that were then averaged. Scans specifically focused on voxels in the temporo-parietal region. All reported differences between the two groups were limited to the white matter regions common to all brains.

Comparing data from both groups, researchers were able to conclude that there were significant differences in FA and CI in voxels in the temporo-parietal region of the brain. These differences indicate that there is a connection between the structure of white matter and a specific cognitive ability among healthy children. This further suggests, although it does not prove, that the difference may be the cause of poor reading development rather than the consequence.

In the end
So structure does in a way indicate ability. Where does that leave us? Wandell and his team may have found a discrepancy in the brains of “normal” and “poor” readers, but there are obviously many other factors involved that fall beyond the scope of this study. The researchers concluded that FA value could be more useful in predicting average or above reading scores rather than in diagnosis of reading disabilities.

0-2 years –rapid growth in axon diameter and myelin strength

3-6 years –significant change in the frontal networks

7-11 years- peak growth rates in fibers connecting sensory-reading cortex

In the years prior to puberty, the section of the corpus callosum which connects cortical region located in and around significant language processing areas can increase as much as 80%.

It is not known specifically how the brain continues to grow during adolescence and through adulthood, although there is indication that growth takes place.

It is clear that there is a relationship between the functional and anatomical development of our brain and the acquisition of skills such as reading.

A teacher at the Early Childhood Center told me recently that teaching a child to read is like teaching a baby to walk. You can hold an infant on its feet, show them how to move their legs, but you can’t force it. One day, it just clicks, and it is no coincidence that walking will occur at a point when the body has developed the muscles and abilities it needs to support itself.
The figures above indicate that we are moving toward a better understanding of how the brain grows and changes as we age. It strongly suggests a connection between this growth and the acquisition of knowledge. However, it does not tell us how each individual’s brain develops or show with authority how we can define differences in the way children learn. Certainly for every statistic we create there will be an exception.
If stages of brain development equip children with the various tools needed to attain literacy, then we can no sooner impose reading on a two year old than we can induce their brain to grow. How
then can we say that a child must conform to a specific timeline in their learning, how can we presume that if they do not perform up to a set standard within a restricted learning style that they are mentally deficient. There are undoubtedly children who do have disabilities related to learning, but we can’t afford to generalize when to do so would be to upset such an important foundation.

I can only conclude that children will learn in their own time and all we can do support them and surround them as many paths as possible on the road to knowledge. Hopefully, with time, there will be a point where “it just clicks.”

Bernard, Sara. “Wired for Reading: Brain Research May Point to Changes in Literacy Development.”

“Children’s Reading Performance is Correlated with Whit Matter Structure Measure by Diffusion Tensor
Imaging.” Deutsh, Gayle K., Robert F. Dougherty, Roland Bammer, Wai Ting Siok, John D.E. Gabrieli, and Brian Wandell. 2003. Department of Psychology, Department of Radiology, Stanford University, Stanford, CA

Ben-Schachar, Michal, Robert F. Dougherty, and Brian A. Wandell. “White Matter Pathways in Reading.”
Current Opinion in Neurobiology 2007, 17: 258-270. ScienceDirect.


Neurobiology researchers prove that the Neurotransmitter Oxytocin has a strong influence and effect on trust in animals and in humans. 

Thursday, February 12, 2009

Study Shows a Marked Difference Between Genders in Color Preference

However open minded Sarah Lawrence students may be, we've all heard it before. Pink is for girls, and blue is for boys. While some have staunchly opposed this concept as an externally induced societal norm, there may actually be some biological validity to the statement.

The Test
In 2007, Newcastle University collected a sample of 208 participants for their study on color preference. The main population were British Caucasian, with a sub-population of mainland Han Chinese participants who had come to the UK within the past year. This was to test whether culture or biology played a larger role. Participants were asked to select their preferred color, as rapidly as possible, from each of a series of pairs of small colored rectangles on an otherwise neutral screen. The shades of the rectangles were specifically chosen to highlight differences in hue, saturation (intensity), and lightness. The participants were each tested three different times, some spanning as much as a two week interval.

While saturation and lightness showed little effect on color preference, the preference in hue differed significantly between males and females. 

The graph shows how often each shade on the red-green spectrum was chosen as a favorite. "The average female preference rises steeply to a sustained peak in the reddish-purple region, and falls rapidly in the greenish-yellow region, whereas the male preference is shifted towards blue-green and less pronounced. The variance in preference over all hues is significantly greater for females versus males, and individual female preference curves are also more stable over time."

What does that mean?
It means that women have more of a variety when it comes to color preference, but when they find something they like, they stick with it. Men have more of a tendency to choose a different rectangle when shown the same pair a second time.

The Good Stuff
While both sexes showed an intense affinity for blue, females are significantly more likely to choose a reddish shade. "Girls' preference for pink may have evolved on top of a natural, universal preference for blue." The difference is so apparent that one can actually predict a person's gender based on their favorite color profile.

But Why?
The currently proposed explanation is that the difference comes out of evolutionary necessity. Based on the hunter-gatherer theory, females would need to be able to identify ripened fruit more than males would need such color specificity for hunting. This theory also accounts for why women responded with a more sustained certainty and stability in their choices. Another theory recognizes females as historically playing the role of care-givers and empathizers. This would require them to hone their recognition of subtle changes in skin color due to emotional states. Examining the data in this way may also explain why blue is favored by both sexes. Blue means good weather and a clean water source.

But... isn't it still possible that this is all society's doing?
Absolutely. Chinese culture promotes red as the color of good luck, and the Chinese participants were also slightly more likely to choose reddish hues than the ones born and raised in the UK, but not nearly to the same degree as females overall.

Cell Press (2007, August 22). Girls Prefer Pink, Or At Least A Redder Shade Of Blue. ScienceDaily. Retrieved February 12, 2009, from /releases/2007
Anya C. Hurlbert, Yazhu Ling, Biological components of sex differences in color preference, Current Biology, Volume 17, Issue 16, 21 August 2007, Pages R623-R625, ISSN 0960-9822, DOI: 10.1016/j.cub.2007.06.022.

Wednesday, February 11, 2009

Sense of Self in Magpies

In a paper published in PLoS Biology by Prior et al. in late 2008, research suggested that magpies have a rudimentary sense of self. This conclusion was supported by experiments that evaluated five magpies with mark and mirror tests. Three of the magpies showed self-recognition behavior rather than the social or aggressive behavior usually displayed by most animals except humans, primates, and a few other known exceptions.

Past Studies on Animal Sense of Self. In 1977, Gordon G. Gallup, Jr., published a pioneering study outlining an explicit test for self-recognition by exposing animals to mirrors. His original experiments yielded support that chimpanzees and orangutans show self-directed behavior; therefore, they display a sense of self. Up until this study, no other animals had displayed a sense of self except for humans (past infancy).

Reiss and Marino (2001) studied bottlenose dolphins and found similar results with two dolphins who were marked on parts of their body not visible without the aid of a reflective surface. Reiss also contributed to a study with Plotnik et al. (2006) that found similar results in Asian elephants using a mark and mirror test to determine if they could achieve mirror self-recognition. Recent research would suggest that these animals have self-awareness because their brains have developed to a point where they have learning and memory capabilities that, in conjunction with sensory input, leads to a sense of self. (Tannenbaum 2008).

Why Magpie?
Certain birds have shown the ability to use tools, have episodic-like memory, and use past experiences to predict behaviors in other birds of the same species. Although these traits are not indicators of a sense of self, they demonstrate birds’ intellectual capacities despite having diverged from primates 300 million years ago.

In particular, European magpies (Pica pica) were chosen because they:
1) hoard food and store it for future consumption, which illustrates their memory abilities.
2) have achieved the highest level of Piagetian object permanence, which surprisingly cannot be attained by monkeys.
3) demonstrate their social intelligence not only with food storage, but their general tendencies to be curious creatures.

The Task at Hand. Five magpies housed in two-compartment cages and exposed to four experimental conditions based on Gallup’s mirror tests conducted with chimpanzees.
1) The bird was marked with a bright color (yellow or red) and placed in a cage with a mirror.
2) The bird was marked with a bright color and placed in a cage with a non-reflective plate where the mirror would have been placed.
3) The bird was marked with a black mark on its throat, which has black feathers, and placed in the cage with mirror.
4) Surprise! The bird was marked with a black mark and placed in the cage with the plate.

Magpie mirror test video

The five birds, Gerti, Goldie, Harvey, Lilly, and Schatzi, were subjected to each of the four trials. When initially placed in front of the mirror, the magpies demonstrated typical social behaviors. Gerti, Goldie, and Schatzi all “showed at least one instance of spontaneous self-directed behavior” during the mark and mirror test. The figure to the left shows Gerti's activity towards the brightly colored mark (orange bar) and black mark (black bar) with and without a mirror present.

So... why does this matter? Sense of self does not simply appear in humans; rather, it is acquired along with other abilities as has been discussed by developmental theorists and outlined in detail with the use of experimental tasks (Bertenthal & Fischer 1978). Still, questions of consciousness and self-awareness, their necessity, and their origins are not completely clear. Studies on animal sense of self alter our view of their brains and capabilities despite evolving separately for millions of years. However, there are a number of issues that arise in the experimental procedure for testing sense of self with the mirror test. Many of the studies cited had small samples of only a handful of animals, especially the controversial studies on elephants, dolphins, and the birds discussed here. In the case of the magpies, two birds did not show self-recognizing behavior. To cement these findings, further studies must be conducted to produce generalizable results.

Bertenthal, B. I. & Fischer, K. W. (1978). Developmental of self-recognition in the infant. Developmental Psychology 14(1), 44-50.
Gallup, G. G. (1977). Self-recognition in primates: A comparative approach to the bidirectional properties of consciousness. American Psychologist, 329-338.
Plotnik, J. M., de Waal, F. B. M., & Reiss, D. (2006). Self-recognition in an Asian elephant. Proceedings of the National Academy of the Sciences 103(45), 17053-17057.
Prior, H., Schwarz, A., & Gunturkun, O. (2008). Mirror-induced behavior in the magpie (Pica pica): Evidence of self-recognition. PLoS Biology 6(8), 1642-1650.
Reiss, D. & Marino, L. (2001). Mirror self-recognition in the bottlenose dolphin: A case of cognitive convergence. Proceedings of the National Academy of the Sciences of the United States of America 98(10), 5937-5942.
Tannenbaum, E. (2008). Speculations on the emergence of self-awareness in big-brained organisms: The roles of associative memory and learning, existential and religious questions, and the emergence of tautologies. Consciousness and Cognition, 1-14.

Girls like pink... but we all like blue

Girls Prefer Pink, Or At Least A Redder Shade Of Blue

See you Thursday!


Sunday, February 8, 2009

Presentation on sense of self in animals

Here's the article I have chosen for my presentation.

Magpies Recognize Themselves in the Mirror


Presentation article: Can experiences be passed on to offspring?

Here is the article for my presentation on Thursday. I hope you all enjoy.

-Katie Bainbridge