Professor researches neurotransmitters to find out what makes humans differ from primates, other animals

When Mary Ann Raghanti, then a graduate student interested in primates and primate behavior, was studying what drives behavior and how behavior affects the physiology of the animals, she realized just how powerful the brain was.

“No matter what I was looking at, no matter what question I was asking, it was always controlled by the brain. Then I finally gave up and decided to focus on that,” said Raghanti, now an anthropology professor at Kent State.

Since then, Raghanti has been studying neurotransmitters, which are chemical agents involved in sending messages between neurons and the brain that play an important role in behavior, cognition and emotion.

Neurotransmitters support higher cognitive functions such as learning, memory and language and a reduction in neurotransmitters results in a decrease of these cognitive functions.

In August, the National Science Foundation awarded Raghanti’s research proposal “The Role of Cortical Neurotransmitter Systems in Human and Nonhuman Primate Brain Evolution” with a $289,872 grant. The NSF also awarded 18 other Kent State researchers in 2009.

The award was funded under the American Recovery and Reinvestment Act of 2009, the economic stimulus package signed in February which includes, among others, domestic spending in education.

Raghanti compares dopamine, serotonin, acetylcholine and norepinephrine neurotransmitters densities in human and primate brains, in which she analyzes language and other association areas important to the cognitive and emotional processes.

To measure brain density, Raghanti and Greg Golden, her assistant, cut and compare humans’ and animals’ brains in sections, work that requires attention and precision.

The brains are cut in sections as thin as eight micrometers (0.000314 inch). A small brain may generate as many as 600 sections.

After they are cut, the sections are immersed in a preparation liquid and stored in tubes. Some of the sections are used in the research while others are stored for later use.

After mathematically deciding which section to use (usually the 10th section), the slice of brain will be removed from the tubes and placed on a plate where it will be later analyzed and compared to different brains.

Neurotransmitters, because of their role in the brain, might be directly related to the evolution of the human brain in comparison with other primates’ brains, Raghanti said. This demonstrates how human and animal brains differ.

“We know that our brain is larger than most, but what makes the human brain unique, we really don’t know that yet,” Raghanti said.

If neurotransmitters indeed contributed to the human brain evolution, Raghanti would be able to see a higher density of neurotransmitter axons in the brain’s regions involved in advanced cognitive functions, Raghanti said.

“What may be different, what might have been a huge push in the evolution of human cognition, is how the different cells are talking to one another and what they are saying,” Raghanti said.

While the human brain, with the help of neurotransmitters, performs essential cognitive functions not always performed by other primates, it is also vulnerable to diseases that don’t affect other primates.

Diseases such as Alzheimer’s, Parkinson’s and schizophrenia, which only affect human beings, are associated with a decrease in the density of neurotransmitters. In her research, which can take up to three years to be completed, Raghanti hopes to find what could be the causes for such diseases.

“If I can identify the places where humans differ from other primates species, we can identify the areas where neurotransmissions are particularly important for cognition, so this would be an important way to target or define places for an intervention,” Raghanti said.

Contact College of Arts and Sciences reporter Mariana Silva at [email protected].