2. The left and right hemispheres

about the episode

The human brain is the result of millions of years of evolution, evolving from a simple nervous system in the form of a rope ladder to the complex structure we have today. The nervous system of a rope ladder is similar to that of a giant snail, and consists of two long threads with divisions. This model helps researchers in the field of the brain because it shows similarities with our own brain.

In evolution, the upper half of the nervous system folded like a ladder into today’s complex brain, while the lower half morphed into the spinal cord. During fetal development, the nervous system goes through a similar journey from a ladder model to the brain and spinal cord. During this development, a 180-degree rotation occurs, connecting the left side of the brain with the right half of the body. This explains why a left-hemispheric stroke can lead to problems controlling the right arm and leg, as well as problems with speaking.

The cerebrum consists of the cerebrum and cerebellum, which are connected by the cerebral cingulate, and the brainstem, which merges into the spinal cord.

Brain tape ensures that the two hemispheres of the brain are in constant contact with each other. Experiments in which the brain tape was cut in people with severe epilepsy showed that both hemispheres could function independently. However, there are few split-brain patients on Earth, so most people use both hemispheres for most tasks.

In this episode, Iris Sommer dispels misconceptions about the left and right hemispheres that are particularly prevalent in the field of coaching. What is the difference between the brains of men and women? Why do some twins have the opposite brain dominance?

About BNR in depth

After the success of Back to the Big Bang with Jovert Schilling, BNR In de Diepte returns with a new season and a new world. In five episodes, Iris Sommer, UMCG psychiatrist and neuroscientist and author, takes you on a journey through the brain. You will learn all about our senses, the left and right hemispheres, whether men have a different brain than women, and what effect your gut has on your personality.

On Iris Sommer

Iris studied medicine at VU in Amsterdam and became a psychiatrist at UMC Utrecht in 2004. In 2010 she became a professor of psychiatry at UU. There she founded the Voice Clinic, where people suffering from hallucinations could go. Her first popular science book was Hearing Voices. This was followed by the book “Haperende Brain” in 2016, which became a bestseller, as well as “The Brain of Women” in 2020.

Since 2017, Iris has been working at UMC Groningen, where she is Director of the Institute for Brain and Cognition Research. There she combines research, patient care and education. In 2021, she was nominated as a Nias Lorentz Distinguished Fellow and served as a fellow at the Netherlands Institute for Advanced Science (NIAS) in Amsterdam. And in 2022, she will be awarded the Huibregtsen Prize for Science and Society. In collaboration with the Hersenstichting Association, she wrote the cookbook Feed Your Brain, about the impact of healthy eating on the brain and behaviour. In August, she and her team will be at Lowlands Science with the theme “Shitty Science.” Her new book “de Bacterie en het Brein” will be published in November this year.