laterality

Right-Brain/Left-Brain

Are you right-brained or left-brained?

One of the dumber questions around.

I think it’s safe to say that if you only had one hemisphere of your brain, you wouldn’t be functioning.

Of course, that’s not the point. But the real point is little more sensible. The whole idea of right brain vs left brain did come out of scientific research, but as is so often the case, the myth that developed is light years away from the considerably duller scientific truths that spawned it.

It is true that, for most of us, language is processed predominantly in the left hemisphere. But what is becoming increasingly more evident is that even the most specialized tasks activate areas across the brain.

In any case, I don’t think the real meaning behind this simplistic dichotomy of right-brain / left-brain has much to do with the physical nature of the brain. People hope by rooting the concept in something that is physically real, that they will thereby make the concept real. Well, I’m sorry, but the supposed scientific foundation for the concept doesn’t exist. However, what we can ask is, is the concept valid? Are some people logical, analytical, sequential thinkers? Are others holistic, intuitive, creative thinkers?

Yes, of course. This is news?

But I don’t like dichotomies. It should never be forgotten that people aren’t either/or. Attributes invariably belong on a continuum, and we are all capable of responding in ways that differ as a function of the task we are confronted with, and the context in which it appears (especially, for example, the way something is phrased). Rather than saying a person is an analytical thinker, we should say, does a person tend to approach most problems in an analytical manner? This is not simply a matter of semantics; there’s an important distinction here.

But there are other personal attributes of importance in learning and problem-solving. For example, working memory capacity, imagery ability, anxiety level, extraversion / introversion, self-esteem (in this case, meaning assessment of one’s own abilities), field-dependence / field-independence (field dependence represents the tendency to perceive and adhere to an existing, externally imposed framework while field independence represents the tendency to restructure perceived information into a different framework). Which attributes are most important? Is this in fact a meaningful question?

The fact is, different personal attributes interact with different task and situational variables in different ways. While it’s probably always good to have a high working memory capacity (the capacity to hold more items in conscious memory at one time), it’s more important in some situations than others. To be a “high-imagery” person may sound a good thing, but if you realize it’s measured on a verbal-imagery continuum, you can see that it’s a trade-off. Personally, I’ve never found being high-verbal, low-imagery a drawback!

The point is, of course, that different styles lend themselves to different tasks (by which I mean, different ways of doing different tasks). It’s not so much what you are, as that you recognize what your strengths and weaknesses are, and realize, too, the pluses and minuses of those abilities / conditions.

For example, a study of 13-year olds investigated the question of interaction between working memory capacity and cognitive style, measured on two dimensions, Wholist-Analytic, and Verbaliser - Imager. They found working memory capacity made a marked difference for Analytics but had little effect for Wholists, and similarly, Verbalisers were affected but not Imagers [1].

Thus, if your working memory capacity is low, in demanding tasks you might find yourself better to approach it holistically – looking at the big picture, rather than focusing on the details.

Once you recognize your strengths and weaknesses, you can consciously apply strategies that work for you, and approach tasks in ways that are better for you. You can also work on your weaknesses. An interesting recent study that I believe has wider applicability than the elderly population who participated in it, found elderly people who draw on both sides of the brain seem to do better at some mental tasks than those who use just one side [2].

Web resources

Cognitive style

There’s an article about cognitive style from a business perspective:
http://www.elsinnet.org.uk/abstracts/aom/sad-aom.htm

If you’re really interested in cognitive style, the Wholist-Analytic, Verbal-Imager inventory was constructed by R.J. Riding, and he’s written a, fairly scholarly, book, entitled “Cognitive Styles and Learning Strategies: Understanding Style Differences in Learning and Behaviour”
http://tinyurl.com/6gpu8

Left-brain / Right-brain

You can also read an essay by William H. Calvin, an affiliate professor at the University of Washington School of Medicine in Seattle, Washington: Left Brain, Right Brain: Science or the New Phrenology?
http://williamcalvin.com/bk2/bk2ch10.htm

And an article first published in the New Scientist on 'Right Brain' or 'Left Brain' - Myth Or Reality? by John McCrone.
http://www.rense.com/general2/rb.htm

This article originally appeared in the January 2005 newsletter.

References: 

  1. Riding. R.J., Grimley, M., Dahraei, H. & Banner, G. 2003. Cognitive style, working memory and learning behaviour and attainment in school subjects. British Journal of Educational Psychology, 73 (2), 149–169.
  2. Cabeza, R., Anderson, N.D., Locantore, J.K. & McIntosh, A.R. 2002. Aging Gracefully: Compensatory Brain Activity in High-Performing Older Adults. NeuroImage, 17(3), 1394-1402.

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Cognitive recovery after brain damage more complex than realized

January, 2011

Two new studies show us that recovery after brain damage is not as simple as one region ‘taking over’ for another, and that some regions are more easily helped than others.

When stroke or brain injury damages a part of the brain controlling movement or sensation or language, other parts of the brain can learn to compensate for this damage. It’s been thought that this is a case of one region taking over the lost function. Two new studies show us the story is not so simple, and help us understand the limits of this plasticity.

In the first study, six stroke patients who have lost partial function in their prefrontal cortex, and six controls, were briefly shown a series of pictures to test the ability to remember images for a brief time (visual working memory) while electrodes recorded their EEGs. When the images were shown to the eye connected to the damaged hemisphere, the intact prefrontal cortex (that is, the one not in the hemisphere directly receiving that visual input) responded within 300 to 600 milliseconds.

Visual working memory involves a network of brain regions, of which the prefrontal cortex is one important element, and the basal ganglia, deep within the brain, are another. In the second study, the researchers extended the experiment to patients with damage not only to the prefrontal cortex, but also to the basal ganglia. Those with basal ganglia damage had problems with visual working memory no matter which part of the visual field was shown the image.

In other words, basal ganglia lesions caused a more broad network deficit, while prefrontal cortex lesions resulted in a more limited, and recoverable, deficit. The findings help us understand the different roles these brain regions play in attention, and emphasize how memory and attention are held in networks. They also show us that the plasticity compensating for brain damage is more dynamic and flexible than we realized, with intact regions stepping in on a case by case basis, very quickly, but only when the usual region fails.

Reference: 

[2034] Voytek, B., Davis M., Yago E., Barcel F., Vogel E. K., & Knight R. T.
(2010).  Dynamic Neuroplasticity after Human Prefrontal Cortex Damage.
Neuron. 68(3), 401 - 408.

[2033] Voytek, B., & Knight R. T.
(2010).  Prefrontal cortex and basal ganglia contributions to visual working memory.
Proceedings of the National Academy of Sciences. 107(42), 18167 - 18172.

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Link between handedness and dyslexia

January, 2011

A genome study has found a gene variant that leads to greater right-hand skill in dyslexics, but not others. The gene is implicated in embryonic development.

While brain laterality exists widely among animal species, the strong dominance of right-handedness in humans is something of an anomaly. As this implies a left-hemisphere dominance for motor function, it’s been suggested that the evolution of language (also mainly a function of the left hemisphere) may be behind the right-handed bias, leading to a search for a connection between hand preference and language disorders. To date, no convincing evidence has been found.

However, a genetic study of 192 dyslexic children has now revealed a strong link between a variant of a gene called PCSK6 and relative hand skill in these children. Specifically, those who carried the variant in PCSK6 were, on average, more skilled with their right hand compared to the left than those not carrying the variant. However, among the general population, this gene variant is associated with less right-hand skill.

The findings provide evidence for a link between brain lateralization and dyslexia. The gene’s protein is known to interact with another protein (NODAL) that plays a key role in establishing left-right asymmetry early in embryonic development, suggesting that the gene may affect the initial left-right patterning of the embryo, with consequences for cerebral lateralization.

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Autism study reveals how a genetic variant rewires the brain

December, 2010

An imaging study has revealed how one of the many genes implicated in autism is associated with an atypical pattern of connectivity between the hemispheres and within and from the frontal lobe.

Many genes have been implicated in autism; one of them is the CNTNAP2 gene. This gene (which is also implicated in specific language disorder) is most active during brain development in the frontal lobe. An imaging study involving 32 children, half of whom had autism, has revealed that regardless of their diagnosis, the children carrying the risk variant showed communication problems within and with the frontal lobe. The frontal lobe was over-connected to itself and poorly connected to the rest of the brain, particularly the back of the brain.

There were also differences in connectivity between the left and right sides of the brain — in those with the non-risk gene, communication pathways in the frontal lobe linked more strongly to the left side of the brain (which is more strongly involved in language), but in those with the risk variant, the communications pathways connected more broadly to both sides of the brain.

The findings could lead to earlier detection of autism, and new interventions to strengthen connections between the frontal lobe and left side of the brain. But it should be emphasized that the autistic spectrum disorders probably encompass a number of different genetic patterns associated with different variants of ASD.

It should also be emphasized that this gene variant, although it increases the risk of various neurodevelopmental disorders (such as specific language impairment, which has also been associated with this gene), is found among a third of the population. So the pattern of connectivity, although not ‘normal’ (i.e., the majority position), is not abnormal. It would be interesting to explore whether other, more subtle, cognitive differences correlate with this genetic difference.

Reference: 

Scott-Van Zeeland., A.A. et al. 2010. Altered Functional Connectivity in Frontal Lobe Circuits Is Associated with Variation in the Autism Risk Gene CNTNAP2. Science Translational Medicine, 2 (56), DOI: 10.1126/scitranslmed.3001344 http://stm.sciencemag.org/content/2/56/56ra80.abstract

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Face coding varies by gender, sexual orientation, & handedness

July, 2010

Why are women better at recognizing faces? Apparently it has to do with using both sides of your brain, and homosexual men tend to do it too.

Why do women tend to be better than men at recognizing faces? Two recent studies give a clue, and also explain inconsistencies in previous research, some of which has found that face recognition mainly happens in the right hemisphere part of the face fusiform area, and some that face recognition occurs bilaterally. One study found that, while men tended to process face recognition in the right hemisphere only, women tended to process the information in both hemispheres. Another study found that both women and gay men tended to use both sides of the brain to process faces (making them faster at retrieving faces), while heterosexual men tended to use only the right. It also found that homosexual males have better face recognition memory than heterosexual males and homosexual women, and that women have better face processing than men. Additionally, left-handed heterosexual participants had better face recognition abilities than left-handed homosexuals, and also tended to be better than right-handed heterosexuals. In other words, bilaterality (using both sides of your brain) seems to make you faster and more accurate at recognizing people, and bilaterality is less likely in right-handers and heterosexual males (and perhaps homosexual women). Previous research has shown that homosexual individuals are 39% more likely to be left-handed.

Reference: 

Proverbio AM, Riva F, Martin E, Zani A (2010) Face Coding Is Bilateral in the Female Brain. PLoS ONE 5(6): e11242. doi:10.1371/journal.pone.0011242

[1611] Brewster, P. W. H., Mullin C. R., Dobrin R. A., & Steeves J. K. E.
(2010).  Sex differences in face processing are mediated by handedness and sexual orientation.
Laterality: Asymmetries of Body, Brain and Cognition.

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