Right Brain and Left Brain Share Duties On "As Needed" Basis
Bilateral prefrontal cortex communication is key to episodic memory function.
Posted September 17, 2017
Fluid communication and coordination between the left and right hemispheres of the cerebral cortex (colloquially referred to as “left brain-right brain”) plays a fundamental role in optimizing cognition and episodic memory function across a human lifespan, according to a new study from Duke University. This paper, “Frequency-Specific Neuromodulation of Local and Distant Connectivity in Aging and Episodic Memory Function,” was published online September 8 in the journal Human Brain Mapping.
For this study, Simon Davis and colleagues at Duke used a neuromodulating device called “transcranial magnetic stimulation" (TMS) to temporarily alter normal brain activity in either the left or right prefrontal cortex of healthy older adults as each person performed a memory task. When TMS is applied to a specific localized brain region it temporarily inhibits the targeted area from functioning at full capacity.
Notably, as the researchers suppressed brain activity in a specific region of the left hemisphere they observed that communication activity with the exact same corresponding region in the right hemisphere skyrocketed, and vice versa. This suggests that the left and right hemisphere recruited similar brain regions in the opposite hemisphere for compensatory assistance to successfully complete an episodic memory task. The Duke neuroscientists believe this finding implies that “communication between the hemispheres is a deliberate process that occurs on an ‘as needed’ basis.”
The researchers also found that stronger white matter pathways between bilateral regions of the left and right cerebral hemispheres marked more robust structural neuroplasticity. Your brain's white matter is a complex labyrinth of myelin-covered axons that connect billions of neurons and carry signals between various brain regions. White matter integrity enables the brain to streamline its functional connectivity and work more efficiently.
Over the past decade, neuroscientists have been using advanced brain imaging "connectomics" techniques to identify and map the elaborate web of white matter that links gray matter (neural brain volume) throughout the entire human brain—including both hemispheres of the cerebrum (Latin for "brain") and both hemispheres of the cerebellum (Latin for “little brain”).
Interestingly, in 2016, researchers at Stanford University led by Manish Saggar reported that suppressing the executive-control centers of the cerebrum—and temporarily allowing the cerebellum to be the “controller"—increased spontaneous innovative solutions or "Aha!" moments. This paper “Changes in Brain Activation Associated with Spontaneous Improvisation and Figural Creativity After Design-Thinking-Based Training: A Longitudinal fMRI Study,” was published in the journal Cerebral Cortex.
Earlier this year, another international team of researchers discovered that people who scored in the top percentile of creative capacity had significantly more connections between the right and left hemispheres of their cerebral cortex. This empirical evidence linking highly creative people with more robust connectivity between the left and right hemispheres of the prefrontal cortex helps to debunk the myth that the “right brain” is the sole seat of creativity. These findings were published in the journal Bayesian Analysis.
This research is all part of the growing field of connectomics. Instead of focusing on how a singular brain region functions autonomously, connectomics and the Human Connectome Project (HCP) illuminate how the entire brain works in concert via finely coordinated communication to optimize cognitive functions and creative capacity.
In a statement, lead author of the new Duke study, Simon Davis, described his team's latest findings: "This study provides an explicit test of some controversial ideas about how the brain reorganizes as we age. These results suggest that the aging brain maintains healthy cognitive function by increasing bilateral communication. Good roads make for efficient travel, and the brain is no different. By taking advantage of available pathways, aging brains may find an alternate route to complete the neural computations necessary for functioning.”
The latest research on the importance of functional connectivity between brain hemispheres corroborates recent post-mortem findings on Albert Einstein's brain. In 2013, a study, "The Corpus Callosum of Albert Einstein's Brain: Another Clue to His High Intelligence," was published in the journal Brain by Dean Falk of Florida State University. This first-of-its-kind study reported that Einstein had significantly more white matter connectivity between the left and right hemisphere of his cerebral cortex when compared to both younger and older control groups.
Just as mindset is never fixed, white matter integrity and functional connectivity are never set in stone. As an example, a growing body of empirical evidence suggests that lifestyle choices such as aerobic physical activity or playing a musical instrument can improve white matter integrity and plasticity. In fact, a 2016 study by researchers at the University of Arizona reported that endurance running altered the functional connectivity of the brain in ways similar to practicing complex tasks such as playing a musical instrument.
Hopefully, future research will help us pinpoint a variety of ways to optimize functional connectivity and coordination between all of our brain hemispheres to boost cognitive function and creative capacity for people from all walks of life across their lifespan.
Davis, Simon W., Bruce Luber, David LK Murphy, Sarah H. Lisanby, and Roberto Cabeza. "Frequency‐specific neuromodulation of local and distant connectivity in aging and episodic memory function." Human Brain Mapping (2017). DOI: 10.1002/hbm.23803
Daniele Durante, David B. Dunson. Bayesian Inference and Testing of Group Differences in Brain Networks. Bayesian Analysis, 2016; DOI: 10.1214/16-BA1030
W. Men, D. Falk, T. Sun, W. Chen, J. Li, D. Yin, L. Zang, M. Fan. The corpus callosum of Albert Einstein's brain: another clue to his high intelligence? Brain, 2013; DOI: 10.1093/brain/awt252
Saggar, Manish, Eve-Marie Quintin, Nicholas T. Bott, Eliza Kienitz, Yin-hsuan Chien, Daniel WC Hong, Ning Liu, Adam Royalty, Grace Hawthorne, and Allan L. Reiss. "Changes in brain activation associated with spontaneous improvization and figural creativity after design-thinking-based training: a longitudinal fMRI study." Cerebral Cortex (2016). DOI: 10.1093/cercor/bhw171
David A. Raichlen, Pradyumna K. Bharadwaj, Megan C. Fitzhugh, Kari A. Haws, Gabrielle-Ann Torre, Theodore P. Trouard, Gene E. Alexander. Differences in Resting State Functional Connectivity between Young Adult Endurance Athletes and Healthy Controls. Frontiers in Human Neuroscience, 2016; 10 DOI: 10.3389/fnhum.2016.00610