5000 Synapses in the Width of a Hair

5000 Synapses in the Width of a Hair

How much change in the brain makes a difference in the mind?

That’s the issue raised by a very interesting comment regarding my previous blog, “The Brain in a Bucket.”

So I’ve taken the liberty of posting the comment here (hoping that’s OK in blog etiquette; still learning as I go), and then responding. Here it is:

I was pondering your statement that long term meditators show a thickening in certain areas of the brain. As I understand it, the volume of the skull is fixed in adults. This would seem to require that if one part thickens, another part must be reduced. I am curious as to whether anyone has considered what the implications of a loss of volume in these other areas might be. I enjoyed your article, and look forward to more on the topic of neurology and meditation.

While the size of the skull is indeed fixed in adulthood, we can both lose gray matter volume due to the normal effects of aging and gain it through mental training of one kind or another.  For instance, one study showed that the hippocampus (really hippocampi, since there is one on each side of the brain, but convention is usually to refer to neural regions in the singular), of London taxi drivers is thicker after their training, which makes sense since the hippocampus is deeply involved with spatial memory.

But the size of these changes in volume is very small, so they do not “bump up against” the skull. For example, the increased thickness in the brains of meditators – seen in one of the cooler studies in this field – amounted – to about 1/200th of an inch. This may not seem like much but is a BIG change in the density of synaptic networks when you can fit about 5000 synapses in the width of a human hair.

The point is that small changes in daily activities – meditating instead of sleeping in, driving a cab instead of working in an office – can make changes in the brain that seem small but actually create big changes in the mind. And that fact opens the door to amazing opportunities.



Dr. Ramani Durvasula is a licensed clinical psychologist, author, and expert on the impact of toxic narcissism. She is a Professor of Psychology at California State University, Los Angeles, and also a Visiting Professor at the University of Johannesburg.

The focus of Dr. Ramani’s clinical, academic, and consultative work is the etiology and impact of narcissism and high-conflict, entitled, antagonistic personality styles on human relationships, mental health, and societal expectations. She has spoken on these issues to clinicians, educators, and researchers around the world.

She is the author of Should I Stay or Should I Go: Surviving a Relationship With a Narcissist, and Don't You Know Who I Am? How to Stay Sane in an Era of Narcissism, Entitlement, and Incivility. Her work has been featured at SxSW, TEDx, and on a wide range of media platforms including Red Table Talk, the Today Show, Oxygen, Investigation Discovery, and Bravo, and she is a featured expert on the digital media mental health platform MedCircle. Dr. Durvasula’s research on personality disorders has been funded by the National Institutes of Health and she is a Consulting Editor of the scientific journal Behavioral Medicine.

Dr. Stephen Porges is a Distinguished University Scientist at Indiana University, Professor of Psychiatry at the University of North Carolina, and Professor Emeritus at both the University of Illinois at Chicago and the University of Maryland. He is a former president of the Society for Psychophysiological Research and has been president of the Federation of Behavioral, Psychological, and Cognitive Sciences, which represents approximately twenty-thousand biobehavioral scientists. He’s led a number of other organizations and received a wide variety of professional awards.

In 1994 he proposed the Polyvagal Theory, a theory that links the evolution of the mammalian autonomic nervous system to social behavior and emphasizes the importance of physiological states in the expression of behavioral problems and psychiatric disorders. The theory is leading to innovative treatments based on insights into the mechanisms mediating symptoms observed in several behavioral, psychiatric, and physical disorders, and has had a major impact on the field of psychology.

Dr. Porges has published more than 300 peer-reviewed papers across a wide array of disciplines. He’s also the author of several books including The Polyvagal Theory: Neurophysiological foundations of Emotions, Attachment, Communication, and Self-regulation.

Dr. Bruce Perry is the Principal of the Neurosequential Network, Senior Fellow of The ChildTrauma Academy, and a Professor (Adjunct) in the Departments of Psychiatry and Behavioral Sciences at the Feinberg School of Medicine at Northwestern University in Chicago and the School of Allied Health at La Trobe University in Melbourne, Australia. From 1993 to 2001 he was the Thomas S. Trammell Research Professor of Psychiatry at Baylor College of Medicine and chief of psychiatry at Texas Children's Hospital.

He’s one of the world’s leading experts on the impact of trauma in childhood, and his work on the impact of abuse, neglect, and trauma on the developing brain has impacted clinical practice, programs, and policy across the world. His work has been instrumental in describing how traumatic events in childhood change the biology of the brain.

Dr. Perry's most recent book, What Happened to You? Conversations on Trauma, Resilience, and Healing, co-authored with Oprah Winfrey, was released earlier this year. Dr. Perry is also the author, with Maia Szalavitz, of The Boy Who Was Raised As A Dog, a bestselling book based on his work with maltreated children, and Born For Love: Why Empathy is Essential and Endangered. Additionally, he’s authored more than 300 journal articles and book chapters and has been the recipient of a variety of professional awards.

Dr. Allison Briscoe-Smith is a child clinical psychologist who specializes in trauma and issues of race. She earned her undergraduate degree from Harvard and then received her Ph.D. in clinical psychology from the University of California, Berkeley. She performed postdoctoral work at the University of California San Francisco/San Francisco General Hospital. She has combined her love of teaching and advocacy by serving as a professor and by directing mental health programs for children experiencing trauma, homelessness, or foster care.

Dr. Briscoe-Smith is also a senior fellow of Berkeley’s Greater Good Science Center and is both a professor and the Director of Diversity, Equity, and Inclusion at the Wright Institute. She provides consultation and training to nonprofits and schools on how to support trauma-informed practices and cultural accountability.

Sharon Salzberg is a world-renowned teacher and New York Times bestselling author. She is widely considered one of the most influential individuals in bringing mindfulness practices to the West, and co-founded the Insight Meditation Society in Barre, Massachusetts alongside Jack Kornfield and Joseph Goldstein. Sharon has been a student of Dipa Ma, Anagarika Munindra, and Sayadaw U Pandita alongside other masters.

Sharon has authored 10 books, and is the host of the fantastic Metta Hour podcast. She was a contributing editor of Oprah’s O Magazine, had her work featured in Time and on NPR, and contributed to panels alongside the Dalai Lama.

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