My Stroke of Insight: A Brain Scientist's Personal Journey

Jill Bolte Taylor grew up in Indiana with older brothers, one of whom demonstrated signs of psychosis as a young man and was diagnosed with schizophrenia as an adult. During her childhood, Taylor observed significant personality differences between herself and her brother. She was particularly struck by how they could interpret the same events differently. These experiences prompted her to become interested in the science of the brain, and she went on to pursue psychology and human biology at Indiana University. In the 1970s, neuroscience was not offered as a specialization and was considered a fairly new field of research. She then worked as a lab technician, where she was fascinated by human dissections, and then completed her doctorate in Life Science.

Taylor became a medical school professor and taught subjects such as Human Neuroanatomy, Human Gross Anatomy, and Histology. During this time, her brother was diagnosed with schizophrenia, inspiring Taylor to research the illness and gain more understanding into how the brain functions. Taylor accepted a position as a post-doctoral researcher at Harvard Medical School and soon began researching how the brain’s visual cortex helps people’s eyes track movement. She then transferred to the Department of Psychiatry to assist with post-mortem investigations into the brains of schizophrenic people.

The author recounts how she attended a conference with the National Alliance on Mental Illness, which supports and advocates for mentally ill people. Taylor felt a close connection to the families she met at this conference who, like her, wanted to help their mentally ill family members recover and enjoy a good quality of life. This experience deepened Taylor’s conviction to find better treatments for schizophrenia. Taylor then began working at McLean Hospital with Dr. Francine Benes, where she was responsible for performing more post-mortem research on the brains of schizophrenic people. However, she was disheartened to learn that her research was at risk of being defunded due to a lack of donated tissue. Determined to fix the problem, the National Alliance on Mental Illness board of directors elected Taylor to advocate for more tissue donations in order to accelerate research into schizophrenia. During her talks, Taylor noticed that the subject of brain tissue donation often made her audiences uncomfortable, so she traveled with her guitar and used humor and song to lighten the mood and continue to spread the word about the role of tissue donation in medical research.

Taylor continued collaborating with Dr. Francine Benes to understand the microcircuitry of the brain and its cells' relationships with each other and with chemical responses (10). The author recalls enjoying her work and fondly remembers winning the Mysell Award from the Harvard Medical School Department of Psychiatry. It was in the middle of her thirties that her “promising future evaporated” when she suddenly experienced a massive stroke that left her unable to talk, walk, read, or write (11).

Taylor notes that in order for people to communicate, we have to have virtually identical nervous systems that interpret reality in the same way (12). Like it does in the rest of our bodies, our genetic code directs our nervous systems , which consist of the same four nucleotides as every other living thing on earth. As with other animals and life forms, humans continue to evolve, and our brains can change rapidly.

While most cells in our bodies have short life cycles and are replaced frequently, our neurons, the foundational cells in our nervous systems, rarely multiply. The long lives of these cells help us retain a similar mindset over the course of our lives.

Taylor describes the human nervous system as “wonderfully dynamic” (13), with over one trillion cells at work, out of over fifty trillion cells in our bodies in total. Over the course of our evolution, even seemingly small changes to our DNA sequences can “result in major evolutionary transformations” (14).

For example, humans and our primate relatives the chimpanzee share 99.4% of our DNA sequence, with all of our differences depending on the remaining 0.6% of DNA (14).

Human brains are different from other mammals’ due to our outer undulated and cerebral cortex, which is twice as large as other animals.’ The cerebral cortex consists of the right hemisphere and left hemisphere, which are joined by the corpus callosum, which Taylor compares to an information highway that shares messages across the hemispheres (15). Our brains are basically identical, and it is only the differences in “intricate microscopic anatomy” that result in differences in personality, behavior and ability level amongst people (16).

Our hemispheres are kept functioning by blood vessels which are also identical in all people, and injury to these arteries can severely impair the brain’s hemispheres from working healthily. If the middle cerebral branch of these blood vessels were damaged, it would compromise someone’s ability to communicate with language and use abstract thinking. The cells in this brain region are considered “uniquely human” (18), as they enable us to perform skills that other animals cannot.

The author explains the basics of the limbic system, which is also called the reptilian brain or emotional brain since other mammals also share this brain region (18). The limbic system imbues information with an affect or emotion, which can become integrated with the rest of our brain’s systems (18). Taylor claims that while people often consider humans as “thinking creatures that feel,” we would be more accurately described as “feeling creatures that think” (19).

Humans’ ability to navigate our environments begins at the sensory level, where cells pass along information to other groups of cells, and each set “further defines and refines the message” (20). This creates the possibility that people may perceive the same environment or situation differently depending on their cells’ ability to function. For example, one person may perceive letters or numbers the way they have been written on the page, while a person with dyslexia perceives them as upside down or flipped. Taylor shares that each person is born with innate differences in how sensitive we are to different kinds of stimuli, which contributes to our different preferences, skills, and life experiences (22).

Our human-specific outer layers of the cerebral cortex are more vulnerable to illness than other areas of the brain, causing strokes to be a leading disabler in American society (22). Strokes occur when the blood vessels that transport oxygen to the brain do not function properly. Strokes can be either ischemic, which constitute 83% of strokes, or hemorrhagic, which constitute the remaining 17%. Ischemic strokes occur when blood clots travel through the arteries until they cannot pass through the narrow blood vessels. Here, they block blood from flowing further down the artery, so all the cells beyond the blood clot lose oxygen and die off. These neurons usually cannot regenerate, and if other neurons do not “adapt over time” to perform those tasks, then the patient loses those cells’ function (23).

A hemorrhagic stroke occurs when blood bursts out of the arteries and leaks onto the brain directly. This type of stroke is particularly dangerous since it is often fatal. An arteriovenous malformation or AVM, which is the kind of stroke Taylor suffered, is a rare type of hemorrhagic stroke, which is caused by a congenital malformation of their arteries. AVM puts undue stress on veins which eventually burst under the pressure, causing blood to leak into the brain.

All strokes will affect survivors differently depending on that person’s brain function and the exact type and location of stroke they suffered. Taylor lists the warning signs of stroke: S for speech and speaking problems, T for tingling or numbness, R for remember and memory issues, O for off balance, K for killer headache, and E for eyes and problems seeing. If someone experiences these symptoms, they may be having a stroke and should  call 911.