How Burnt Toast Mapped The Human Brian
Despite only weighing 3 pounds, the brain has the capacity to control all sensation and action of our entire bodies! But how do we know which areas of the brain control which areas of the body? Revolutionary and unconventional experiments, carried out by Wilder Penfield in the 1930s, unlocked this information. Penfield was a Canadian neurosurgeon who was intrigued by the mechanisms and dysfunction of the brain, particularly in illnesses such as epilepsy. Through studying surgical techniques alongside the causes of epilepsy, Penfield was equipped with skills and knowledge that would produce a profound foundation for future neuroanatomists.
A Wild-er Experiment:
Wilder Penfield established and fundraised the Montreal Neurological Institute, in an attempt to collate knowledge from all neurologists – from scientists to surgeons. It was here that the “Montreal procedure” was born. This procedure used epileptic patients as experiments to map out the control of body parts on the brain. Epileptic patients were used as they were already undergoing surgery to identify the area of their brain that was causing sporadic seizures, so that this region of cortex could be removed. The procedure required patients to undergo brain surgery whilst awake. Penfield would apply an electrical shock, carried by a probe, to different brain regions. A colleague would then ask the patient what they could feel in response, as this would indicate the effect of the stimulated cortex. For example, an electric shock at the top of the central brain may cause a tickling feeling in one’s foot!
One patient of Penfield was a woman who would smell burnt toast before every seizure she had, even if there was no burning toast to be smelt! Through the Montreal procedure, Penfield was able to pinpoint the area of her brain that was causing the seizures by passing an electrical current through her brain, until she could smell burnt toast! This region was removed and successfully eradicated the woman’s epilepsy.
Although Penfield’s work is highly illegal now, at the time he was considered “the greatest living Canadian”. Luckily in today’s society, rather than opening a subject’s head, we use much less invasive imaging techniques to visualise the brain. For example, functional magnetic resonance imagining (fMRI) are used to show changes in blood supply in response to neuronal activity, as the blood will shunt to areas of the brain that the subject needs to perform an action. Penfield’s work has made massive contributions in producing the topographic map of the brain.
The topographic map of the brain describes how sensation of body parts are represented on the cortex of the brain and is produced by organised collections of neurones. The map is not perfect – certain areas of the body have more representation on the brain than others. For example, lips, fingertips and the tongue have large areas of representation and therefore are far more sensitive than other body parts such as your inner wrists and shoulders – hence these are ideal places for tattoos as you won’t feel so much pain!
Follow My Blog! Get new content delivered directly to your inbox!
Chronicles of Science 