The human brain has been the subject of fascination and study for centuries. The ancient Greek physician Hippocrates characterized the brain as “the analyst of the outside world, the interpreter of consciousness and the center of intelligence and willpower.”[1]

Here at Van Andel Institute, our scientists are exploring the brain in search of insights into diseases such as Parkinson’s and Alzheimer’s and psychiatric disorders such as depression.

Here are six facts about this complex organ, the history of its study and current brain research.

The first known written use of the word “brain” comes from an ancient Egyptian text.

The Edwin Smith surgical papyrus is a significant document in both the history of medicine and neuroscience. It was written around 1700 B.C. in ancient Egypt and is the earliest known medical text. The papyrus contains a number of notable firsts: the first known written use of the word “brain,” the first known descriptions of head injuries and the first known written description of cerebrospinal fluid. The document is named after American doctor Edwin Smith, who purchased it in the 19th century.[2]

Despite human knowledge of the brain spanning millennia, our understanding of its mechanisms is recent.

Humans have known about the brain and understood its basic functions for thousands of years, but it is only in recent decades that we have started understanding how it works. Thanks to rapid advancements in technology and strong support for biomedical research, our understanding of the brain — and how it’s affected by like Parkinson’s and Alzheimer’s and psychiatric disorders like depression — has greatly accelerated in a relatively short period of time.[3]

The human brain contains approximately 86 billion neurons (though the exact number has been hotly debated)[4]. The unnatural death of these cells gives rise to diseases like Parkinson’s and Alzheimer’s.

Neurons are specialized cells that transmit signals throughout the nervous system, which controls the body’s motor and sensory functions. A number of neurodegenerative diseases, such as Parkinson’s and Alzheimer’s, are believed to result from the unnatural death of neurons in the brain. Scientists in Van Andel Institute’s Department of Neurodegenerative Science are working to understand the different reasons for this cell death in the brain and how it gives rise to disease. The insights they uncover may lead to new ways to slow or stop disease progression, which is not possible with current treatments.

In 2020, VAI’s Dr. Rita Guerreiro, in collaboration with VAI’s Dr. José Brás and researchers in Portgual, began a five-year study into the genetic predisposition to Alzheimer’s in the Portuguese population. That same year, Brás, VAI’s Dr. Darren Moore and collaborators from University of Minnesota began a three-year study to define the molecular linkages between aging and Parkinson’s — an approach  for new treatment targets not yet explored by many researchers.

Related: Road to cell death mapped in the Alzheimer’s brain

Some diseases popularly thought to be brain-related may have origins elsewhere in the body.

Parkinson’s disease is generally viewed by most people as strictly brain-related because of its hallmark neurological symptoms, such as tremor and loss of voluntary movement. But growing evidence suggests that other parts of the body, such as the gut and nose, may also play important roles in Parkinson’s onset and progression.

In 2017, VAI Deputy Chief Scientific Officer Dr. Patrik Brundin co-authored a study that examined more than 500 scientific papers and found links between the sense of smell and Parkinson’s. Additional research from Dr. Brundin’s lab has shown the area of the brain that controls our sense of smell may be a starting point for Parkinson’s-related changes in the brain.

A 2018 study led by the late Dr. Viviane Labrie of VAI found that the appendix acts as a reservoir for Parkinson’s-related proteins called alpha-synuclein, and that removal of the appendix early in life corresponded with a reduced risk for Parkinson’s. Research suggests alpha-synuclein can travel to the brain from elsewhere in the body via the vagus nerve, one of the longest nerves in the body and a “superhighway” to the brain. 

The brain’s emotional center may hold clues to psychiatric symptoms in people with Parkinson’s.

The amygdala is the part of the brain that regulates our emotions and memories associated with emotions. It shows high levels of clumps of alpha-synuclein proteins in people with Parkinson’s; psychiatric symptoms such as depression, apathy and anxiety are common disease symptoms. VAI’s Dr. Hong-yuan Chu is probing the links between these alpha-synuclein clumps and psychiatric symptoms in people with Parkinson’s with support from a 2020 NARSAD Young Investigator grant from the Brain & Behavior Research Foundation. 

Chronic inflammation may have devastating consequences for the brain.

A growing body of research suggests that sustained inflammation in the body may cause a toxic imbalance that alters brain chemistry and elevates suicide risk. Inflammation is the body’s natural reaction to harmful stimuli, but when inflammation occurs longer than it should, it can have devastating consequences.

In 2019, Dr. Lena Brundin of VAI, Dr. Eric Achtyes of Pine Rest Christian Mental Health Services and Dr. J. John Mann of Columbia University embarked on a five-year study to search for biomarkers in the blood that may help identify the inflammatory mechanisms that give rise to depressive and suicidal symptoms, with the goal of developing ways to stop them.

If you or someone you know is experiencing suicidal ideation, the confidential National Suicide Prevention Lifeline is free and available 24/7 at 1-800-273-TALK (8255).

Scientists are unlocking the mysteries of how Alzheimer’s moves through the brain.

Tangled clumps of misfolded proteins called tau proteins have been found to “travel” through the brain, seeking vulnerabilities that may give rise to Alzheimer’s disease, according to new research from VAI’s Dr. Michael X. Henderson and University of Pennsylvania. The findings shed light on how these proteins move through the brain, which may help researchers determine new ways to clear or prevent them.

Funding notes

Dr. Guerreiro is supported by the National Institute on Aging of the National Institutes of Health under award no. R01AG067426 (Guerreiro). This content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.

Dr. Moore and Dr. Brás are supported by the Aligning Science Across Parkinson’s Initiative, an international collaborative research effort partnering with The Michael J. Fox Foundation for Parkinson’s Research to implement its funding.

Dr. Patrik Brundin was supported by The Michael J. Fox Foundation, National Institutes of Health, Cure Parkinson’s, TEVA Neuroscience, East Tennessee Foundation, KiMe Fund, and Campbell Foundation.

Dr. Lena Brundin is supported by the National Institute of Mental Health of the National Institutes of Health under award no. 1R01MH118221 (Brundin, Achtyes, Mann). This content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.


[1] Hippocrates: the forefather of neurology. National Library of Medicine. Accessed June 11, 2021.


[2] The Edwin Smith surgical papyrus: description and analysis of the earliest case of aphasia. National Library of Medicine. Accessed June 11, 2021.


[3] Decoding the brain through research — the future of brain health. The BMJ. Accessed June 11, 2021.


[4] Equal numbers of neuronal and nonneuronal cells make the human brain an isometrically scaled-up primate brain. National Library of Medicine. Accessed June 11, 2021.