The right cerebral hemisphere can "take over" language functions if the left hemisphere is damaged during early development, according to a new study (François et al., 2019) by researchers from the University of Barcelona. Their paper, "Right Structural and Functional Reorganization in 4-Year-Old Children with Perinatal Arterial Ischemic Stroke Predict Language Production," was published on Aug. 5 in the journal eNeuro.

As you can see in the brain images below, these findings offer fresh insights and breathtaking photos of how a child's brain can reshape itself via neuroplasticity in response to .

Source: François et al., eNeuro 2019 DOI: 10.1523/ENEURO.0447-18.2019

Hemispheric specialization refers to the lateralization of function between the left and right cerebral hemispheres. Typically, language functions primarily occur in the left hemisphere. Colloquially, the left and right hemispheres are referred to as "left brain- ."

When an adult has a stroke that causes damage to language areas in the left cerebral hemisphere, the injury often results in speech aphasia. However, children who have a similar type of stroke—and experience damage to language regions in their left brain—don't usually suffer the same degree of speech problems. Until now, neuroscientists didn't understand precisely why children and adults tend to have a different response to language-center stroke damage.

For this recent study on the hemispheric flexibility of language development, Clément François and colleagues used advanced neuroimaging techniques to identify white-matter fiber tracts that connect different language-processing regions in the brain.

As an example of brain reconfiguration in action, the white-matter fiber bundles that connect language-processing brain regions were more robust in the right hemisphere of childhood stroke patients. Notably, the researchers found that after a stroke had damaged the left hemisphere, children who did well on language tests had more brain volume in the "right brain."

This recent study (2019) on brain reorganization provides more evidence that "inter-hemispheric plasticity" between the left brain and right brain makes it possible for language functions that are typically associated with the left side of the brain to function from the other side.

How Do These Findings Fit into a Timeline of Split-Brain Models and Maps?

In the 1960s, legendary , Roger Sperry (1913-1994) conducted pioneering research on functional differences between the left and right cerebral hemispheres. Sperry's work on hemispheric specialization focused on the dominant functions of each hemisphere.

One of Sperry's most significant discoveries was that the so-called "left brain" tends to be the seat of language functions and linguistic ability. In 1981, Sperry received a Nobel Prize for his revolutionary split-brain models. As might be expected, Sperry's well-publicized work on lateralized functions piqued the curiosity of the general public and "left brain-right brain" became part of our everyday vernacular.

Source: Pixabay

The pop-psychology interpretation of Sperry's split-brain model was that the "right brain" specialized in nonverbal, visual, and creative processes while the "left brain" was solely responsible for language, logic, and more analytic information processing. Today, this oversimplified representation of how the brain works—and the notion that some people are more "left-brained" and others more "right-brained"—is considered a myth.

Although Sperry's work is often misinterpreted, during his lifetime, he was prudent about framing preliminary hemispheric lateralization research findings as a work in progress. Sperry made it clear to anyone listening closely that his hypotheses about left brain-right brain lateralization would most likely evolve over time.

In a 1967 lecture, "Language Following Surgical Disconnection of the Hemispheres," Roger Sperry explains the ever-changing nature of brain lateralization research with a and a healthy dose of caution. Wisely, he warns listeners in the audience not to make any "set-in-stone" conclusions based on his team's earliest discoveries:

"Our testing program is in full swing and, overall, the picture continues to change from month to month. Just as our working picture is rather different from that of a year or two ago, that of [the future] may also be different. I suspect just a word of caution may be in order here in regard to any attempt to apply this current view to interpretations of clinical material or the global value judgments regarding historical developments in this field. I am not sure we really have the definitive picture even at this moment that would enable one to pass the proper long-term judgment."

My late father, Richard Bergland (1932-2007) was a neuroscientist and neurosurgeon who idolized Roger Sperry. For better or worse, my dad contributed to making "left brain-right brain" lateralization part of the mainstream in his general audience book The Fabric of Mind. Based on the Hebbian theory (1949) of synaptic plasticity from The Organization of Behavior, he also advanced the notion that brain plasticity makes reconfiguration possible and that the human brain reshapes and rewires itself to streamline whole-brain functions.

By the early-21st century, my father was convinced that optimizing white matter functional connectivity and structural gray matter volume in all four brain hemispheres via neuroplasticity and neurogenesis (the birth of new neurons) was of paramount importance. In the final years of his life, Dad was eager to put the interplay between both hemispheres of the cerebrum and both hemispheres of the cerebellum (Latin for "little brain") in the spotlight.

Luckily, in 2007 (just before my father died), I was able to publish his nonconformist ideas about hemispheric lateralization and our split-brain model in The Athlete's Way. Although it may sound grammatically incorrect, my father and I called this paradigm "up brain-down brain," which is a direct and cogent response to "left brain-right brain." (See, The Split-Brain: An Ever-Changing Hypothesis)

Source: Photo and illustration by Christopher Bergland (circa 2009)

I drew this rudimentary "Super 8" brain map (above) in 2009 as a way to illustrate the importance of optimizing the functional connectivity of white matter tracts (represented by the bidirectional yellow and green pathways) and gray matter volume of all four brain hemispheres across a lifespan.

The latest research (Clément François et al., 2019) on left brain-right brain reconfiguration in four-year-olds reaffirms that brain plasticity is especially robust in children. That said, a growing body of evidence also suggests that neuroplasticity and neurogenesis make brain reconfiguration to varying degrees possible at any age.

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