Scientists train neurons in research on memory

In vitro study by Brazilian researcher affiliated with George Mason University was presented to 4th BRAINN Congress at the University of Campinas in São Paulo State.

By Karina Toledo, in Campinas  |  Agência FAPESP – Are laboratory-grown neurons capable of learning? Experiments conducted at George Mason University (GMU) in the United States suggest they are.

The neurons are “trained” by Nathalia Peixoto, a Brazilian-born professor in GMU’s Electrical and Computer Engineering Department and former recipient of a scholarship from FAPESP. The research is designed to develop a deeper understanding of how the brain works, especially with regard to memory, both in normal conditions and in the context of diseases such as Alzheimer’s and epilepsy.

Peixoto spoke about the research at the 4th BRAINN Congress held in late March 2017 at the University of Campinas (UNICAMP) in São Paulo State by the Brazilian Institute of Neuroscience & Neurotechnology (BRAINN), one of the Research, Innovation and Dissemination Centers (RIDCs) funded by FAPESP.

“Understanding the dynamics of the in vivo brain in normal and diseased states is one of the great challenges of modern science,” she said. “However, the overall complexity and dimension of the brain can make this problem intractable. For this reason, we have developed in vitro experimental and computational models in an effort to study these dynamics in a simpler and more controlled setting.”

In Peixoto’s lab, frontal cortex and spinal cord neurons taken from mouse embryos are cultured on a glass slide containing a microelectrode matrix. These devices record the electrical signals emitted by nerve cells (nervous impulses or action potentials) and stimulate them electrically when necessary.

The cells are incubated at 37°C and high humidity for about three weeks, after which they start organizing neural networks and exchanging information via chemical and electrical synapses. A few days later, training with electrical stimulation begins.

“At this stage, we have what’s known as a brain in a dish,” Peixoto said. “The cells are first stimulated with a low-frequency electrical field so that the response pattern can be recorded. Then, we apply a high-frequency training signal and observe a much more intense response from the neurons. When we resume the previous low-frequency stimulation pattern, we notice that the cells display heightened sensitivity as if they had a memory of the training signal.”

Tests are being performed to find out how well neurons cultured in the laboratory can recognize electrical stimulation patterns. One such test consists of activating microelectrodes in predetermined sequences to form different letters in order to see whether the neurons’ response varies based on each letter, following a certain pattern, almost as if they were having a conversation.

In another experiment, Peixoto’s group added amyloid beta protein, the hallmark of Alzheimer’s disease, to the cultured neurons and observed that this impaired their electrical activity.

“In a single day, the neurons stopped generating action potentials, and this made memory testing impossible,” Peixoto said. “We then looked deeper to see what kinds of beta amyloid most affect cultures and found that in general, they’re the kinds that form plaques in patients with Alzheimer’s.”

The researchers now plan to test alternatives believed capable of restoring electrical activity in the neurons.

“Data in the scientific literature indicate that a substance present in turmeric is effective at hindering the development of beta-amyloid plaques. There’s a hypothesis that it may be possible to restore normal activity in the brain if it’s protected against plaque formation. We plan to perform this test and hope to prove that memory capacity remains intact,” Peixoto said.

Her goal as an engineer (she graduated from the Politécnica, the University of São Paulo’s Engineering School) is to “repair what’s broken”, she went on. As a result, she designs in vitro models of diseases that affect the brain in order to try to reverse these pathological conditions by applying electrical or magnetic fields.

“In the case of Parkinson’s, symptoms like tremor can be controlled by electrical deep brain stimulation therapy, although it isn’t known exactly why,” she said. “We want to study the effects of electrical neuron stimulation more deeply and use this methodology to measure chemical substances in the brain, such as dopamine, ascorbic acid and uric acid.”

Another line of research led by Peixoto at GMU seeks to develop new types of electrode for use in Deep Brain Stimulation (DBS) equipment. DBS is being studied as a therapy for stroke and for Parkinson’s disease, as well as for patients with depression, chronic pain, and obsessive-compulsive disorder.

“DBS is traditionally done with electrodes made of platinum and iridium,” she said. “We’re testing carbon nanotubes in vitro, as well as a conductive polymer called PEDOT [poly(3,4- ethylenedioxythiophene)]. Our goal is to reduce the electrodes’ resistance in order to make the stimulation less aggressive to the cells and increase equipment battery life.”

Building bridges

In an interview with Agência FAPESP, Peixoto said her participation in the event held by BRAINN aroused considerable interest in collaborating with the UNICAMP research group.

According to Fernando Cendes, BRAINN’s coordinator, this is precisely one of the aims of the congress, which has been held at UNICAMP for the past four years.

“The event began as a workshop to make the projects performed under BRAINN’s aegis known to the entire community of the consortium, which is very large,” Cendes said. “We also invited outside researchers to show the progress being made in research areas covered by the RIDC and to build bridges in terms of communication and collaboration with researchers in other countries.”

Another guest speaker at the 4th Congress was Richard Frayne, a frequent collaborator with BRAINN and a professor at the University of Calgary in Canada. His group has used nuclear magnetic resonance techniques to analyze morphological and functional changes in small blood vessels in the brain in order to understand mechanisms linked to healthy aging and dementia.

“With exercise and diet, these functional changes in the small brain vessels are seen to decelerate,” Frayne said. “Unfortunately, we can’t stop the process, but there are many things that can be done to delay dementia and foster more dignified aging. From the vascular standpoint, everything that’s bad for the heart – smoking, alcohol, sedentarism, and the western diet – is also a risk factor for brain health.”