My family recently lost our matriarch, my Yiayia (grandmother in Greek) Nicoletta. It was at her funeral that I came to the realization that I had already grieved for her. I had already mourned. She was now at peace and I was grateful.
Yiayia was diagnosed with Alzheimer’s dementia 6 years before her death. Her symptoms varied day-to-day. She had good days and bad days. Slowly the former became fewer. Her struggle inspired me to pursue a doctorate in biology studying learning and memory.
We are a summation of our past, or at least our own interpretation of that past. We can change and grow, but even growth is dependent on previous experience. To lose your past is to lose who you are. Learning and memory are two sides of the same coin.
If this sounds complicated, that’s because it is complicated. Studying the tens of billions of neurons in the brain is equivalent to space exploration. Neurons are cells that specialize in communication. Think of them as your body's version of the internet, only more complicated.
Currently, researchers have a thorough understanding of the psychology of learning and memory. We know there are different types of memory; and that memory involves distinct stages of encoding, storage, and retrieval. We even have a decent grasp of the mechanics. Certain brain regions, like the hippocampus and amygdala, are necessary for learning and memory to occur.
But how do all the pieces come together to make a memory? How could my Yiayia Nicoletta still sing Christmas hymns after she lost her ability to talk to us? Many insights in human psychology came from studying individuals who had lost a specific brain function. After a workplace accident in 1884 Phineas Gage sustained brain damage and his personality changed. His injury is still being studied today. In addition to clinical studies, modern technology like fMRI and other brain imaging techniques have improved our study of the human brain. However, these techniques do not measure the activity of neurons directly.
To dive deeper, scientists turn to animal models. You may have heard of Ivan Pavlov and his dogs who laid the foundation for modern behavioral experimentation. If you are a pet owner you’ve likely used Pavlov’s classical conditioning techniques to train your furry friends.
You may be less familiar with research done using the humble fruit fly (Drosophila melanogaster). Scientists have been studying flies for over 150 years, providing an incredible understanding of fly genetics, neuroscience, and biology. Researchers can manipulate the expression of genes using the GAL4/UAS system. These genetic tools allow us to compare the biology of flies with our own.
If you were to take a glance at a fly you probably wouldn’t guess that we share approximately 75 percent of the genes responsible for human genetic diseases. Even the genes essential for human development are shared with flies. This similarity extends to learning and memory. Where we have a hippocampus that serves this function, the fly has a brain region known as the mushroom body.
Mutations of two genes, rutabaga and dunce, prevent flies from forming memories. These genes led to the discovery of their protein products (adenylyl cyclase and cyclic AMP respectively) which are essential components of memory formation. More pieces of the memory puzzle fall into place.
I study Drosophila larvae. The most frequent question I receive about my work is, “but… why maggots?” Other animal models may seem more intuitive. Rats are mammals; they are more closely related to us. However, larvae provide researchers a unique set of benefits. Similar to their adult counterparts they possess a mushroom body and unrivaled genetic toolkit. They have even fewer neurons in their brains (~9,000) than adults (~214,000). Larvae are also transparent which allows researchers to view neural circuits one cell at a time without harming the animal. By combining all of these tools, researchers have discovered a neural circuit that is responsible for memorizing different smells. Researchers now have an extensive understanding of how larvae process odors. However, memory is multi-sensory and the next steps in larval research involve understanding how different senses integrate during learning and memory.
Overall, researchers continue to find memory difficult to pin down. Memories seem to exist as patterns of interactions between neurons, and complex systems are more difficult to troubleshoot. So, who knows, maybe the key to slowing dementia can be found in the mind of a maggot.
Nikolaos Polizos is a graduate student in the College of Arts and Sciences at the University of Miami. Read more about the inaugural “Op-ed Challenge.”
