Finding Molecules That Shape Memory
Modern neurobiology has confirmed what many suspected: experience rewires the brain. Consider this:
- In 1949, a Canadian psychologist Donald Hebb theorized that certain experiences caused particular neurons to fire together, forming a network that strengthened each time the experience was repeated.
- In 1984, researchers Michael Greenberg and Edward Ziff demonstrated that experience also alters changes within cells, thereby regulating which genes were expressed. Their discovery is known as activity-driven gene expression opened the door to understanding how experience leaves a biological imprint on the brain.
- Fast forward to today, Simon Pieraut, Ph.D., assistant professor of psychology in Florida Atlantic University’s Charles E. Schmidt College of Science, is following that thread even deeper and studying how these activity-driven molecules reshape neural circuits in a process known as structural plasticity — essentially, the brain’s ability to rewire itself.
In his lab at FAU, Pieraut, who is also a member of the Stiles-Nicholson Brain Institute, focuses on inhibitory neurons in circuits associated with memory and learning. As their name implies, inhibitory neurons control the activity of nearby cells. Depending on what experience the inhibitory neuron is exposed to, it may form a new synapse or eliminate one. It may connect to another cell’s dendrite, axon or cell body.
In 2023, the National Science Foundation (NSF) awarded Pieraut’s lab an $800,000, five-year grant to study how memory formation in the hippocampus is controlled by inhibitory neurons that form a “basket” of synapses around the bodies of excitatory neurons. The hippocampus is responsible for memory formation and retrieval.
The grant builds on research Pieraut’s lab reported in Journal of Neuroscience in 2021 and Molecular Brain in 2022. Experimenting with mice, the 2021 paper found that a stimulating environment guided basket cells to form more synapses on the bodies of excitatory cells in the dentate gyrus, thereby increasing the control of their firing rate. The dentate gyrus filters the information that goes into the hippocampus. It also enables discrimination between two objects that are nearly identical.
The 2022 paper found that the same stimulating environment, by enhancing the mice’s early social, physical, and sensory activity, modified how the incoming signals were filtered in the dentate gyrus. Taken together, the papers suggest that structural plasticity induced by experience may affect information processing.
From an early age, Pieraut has been fascinated by psychology and psychiatry. His research dives directly into biological mechanisms that have been shown to be impacted in mental health disorders. Clinical and animal model studies show that symptoms in nearly all mental illnesses, including depression, schizophrenia and autism, are, at least in part a direct consequence of disrupted or maladaptive plasticity in neural circuits.
“By understanding these mechanisms, we hope to find ways to alleviate some of these symptoms,” Pieraut said. “Even better, maybe we can find new targets for pharmacological treatment.”