To remember or not to remember: How does the brain decide between the two?
By Janie Larocque and Rachel Nadeau
Special Guest Writers
Janie Larocque and Rachel Nadeau are 4th year Faculty of Medicine students in the Honours Bachelor of Science Program in Translational and Molecular Medicine. They wrote this story originally for their Science Communications course as part of a series profiling researchers at the Faculty of Medicine.
The brain is the most complex and least understood organ in the human body. It produces our every thought, action, memory, feeling and experience of the world. This three-pound, jelly-like mass of tissue containing a staggering one hundred billion nerve cells, or neurons, is where we produce and store our memories—but every so often our brains do let us down.
A particularly annoying example of this is the well-documented phenomenon of walking into a room and forgetting why you’re there. The big question is, “How do we remember, and why do we often forget?” Typical of biology, the answer is complicated and incomplete.
These questions drive Dr. Jean-Claude Béïque, professor in the Faculty of Medicine Department of Cellular and Molecular Medicine, who seeks to better understand the brain’s ability to learn. To achieve this goal, his research team is studying synapses, the contact points between neurons in the brain. These tiny structures are highly dynamic, meaning they can change and adapt to new information. The ability of these synapses to change within the network of neurons is called synaptic plasticity, and is thought to be the basis of learning and memory.
Synaptic plasticity dictates how effectively two neurons communicate with each other at a synapse. The strength of communication between two neurons can be compared to the volume of a conversation—some neurons whisper to each other, while others shout. The volume setting of the synapse, or the synaptic strength, is dynamic and can change in both the short term and long term.
There are several forms of synaptic plasticity, each with the ability to cause changes in synaptic strength; examples include Hebbian and homeostatic plasticity. Hebbian plasticity refers to changes in synaptic strength that occur in less than one second: a rapid increase or decrease of the volume that serves for learning and memory. Homeostatic plasticity lasts anywhere from minutes to days and helps determine how important the connection is to the ongoing conversation before adjusting the volume to maintain the conversation at “normal.”
Because synaptic plasticity is thought to contribute to learning and memory, it has since become one of the most intensively researched topics in neuroscience. Hebbian plasticity is widely considered the main model for how the brain stores information, but it also leads to unstable neuronal activity that requires adjustments by other processes. It is believed that homeostatic plasticity plays this role. However, “how these plasticity mechanisms interact and influence one another remains unclear,” said Dr. Béïque.
Last year Dr. Béïque and colleagues published a paper that shed some light on the problem. By altering the dynamics of rat synapses, they found that the homeostatic response to Hebbian processes can fine-tune the volume at synapses and regulate the communication between neurons. Although it’s a big leap from rat to human beings, these results show plenty of promise. At the very least, they demonstrate how synaptic plasticity affects the brain.
But the story doesn’t end there. These discoveries are a good starting point for identifying the “rules” that define how neurons communicate with each other at synapses. Dr. Béïque and his team are also hoping to understand how the features of these neurons are changed by memory loss (e.g., Alzheimer’s) and mood disorders.
As any brain scientist will tell you, there’s still a long way to go before ‘understanding the brain’ gets crossed off science’s to-do list. But there has been progress.
“Right now, we can do things in my lab that I would never have thought feasible 10 years ago,” said Dr. Béïque.
In this case, the brain holds all the answers.
The Science Communications course is designed and taught by Dr. Kristin Baetz, director of the Ottawa Institute of Systems Biology and professor in the Department of Biochemistry, Microbiology and Immunology, to foster in students the ability to convey complex science to a lay audience – an essential skill when making presentations, applying for grants, composing abstracts for research papers and generally communicating one’s work in the biomedical sciences.
MedPoint will be publishing profiles from this series throughout 2019.