Left-brain vs. right-brain hypothesis challenged but not overturned

3 Nov

A paper published in PLOS-one, argues that there is no neurophysiological basis for the claim that some people are left brained dominant while others are right brained dominant.

The researchers examined fMRI brain scans in publicly available data sets for 1011 individuals. In the video  Jeffrey S. Anderson, M.D., Ph.D. describes the work.

However, I do not believe that this definitively  refutes the notion of left brain versus right brain cognitive styles. First of all, some of the study results do not match the findings of other studies. For example:

“Similarly, we saw no differences in functional lateralization with gender. These results differ from prior studies in which significant gender differences in functional connectivity lateralization were reported . This may be due to differing methods between the two studies, including the use of short-range connectivity in one of the former reports and correction for structural asymmetries in this report. A prior study performing graph-theoretical analysis of resting state functional connectivity data using a predefined parcellation of the brain also found no significant effects of hemispheric asymmetry with gender, but reported that males tended to be more locally efficient in their right hemispheres and females tended to be more locally efficient in their left hemispheres.”

In addition, the study does acknowledge the existence of some lateralized functions:

“Our data is broadly consistent with previous studies regarding the spatial distribution of lateralization of functional connectivity. We find that brain regions showing consistently strong left-lateralization include classical language regions (Broca Area, Wernicke Area, lateral premotor, and anterior supplementary motor areas). MNI coordinates associated with greatest left-lateralization match closely those reported in task-based fMRI studies of language [32]. Broca and Wernicke Areas have been shown to comprise a distributed language network, predominantly left-lateralized, in their functional connections and include both adjacent cortical as well as subcortical regions”

Critically, the paper did not look at any of the behavioral correlates that are supposed to be related to left vs right brain dominance. Here is a paper that looked at EEG activity and found behavioral correlates to a psychometric measure of brain dominance.

And there are many other studies that do show  relationships between brain asymmetries and individual differences in behavior.

Thus, while we will many stories in coming days about left-right brain dominance being debunked, in my mind, the question is still open.

2 Responses to “Left-brain vs. right-brain hypothesis challenged but not overturned”

  1. TCY December 14, 2013 at 2:01 pm #

    can i know the 1st example is come from where ?? thank you=)

    • jecgenovese December 14, 2013 at 5:44 pm #

      I am sorry I don’t understand your question, could you rephrase it?

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