Scientist Profile – Professor Steve Ramirez
Decoding the Mechanisms of Memory
Steve Ramirez, Ph.D. – Associate Professor of Psychological & Brain Sciences
The Ramirez Group, led by Professor Steve Ramirez, investigates how we process and retrieve memories as well as how those memories might be artificially modulated to treat mental health disorders.
Professor Ramirez explained how studying mouse brains helps us learn about human brains, and how he makes activated memory cells visible (and vibrant). He also talked about boxing, running, and his unique approach to navigating stairs.
How would you describe your research and the goals of your lab?
We study the fundamental mechanisms of learning and memory by focusing on how these processes occur in mouse brains. One half of the questions we ask can be boiled down to: What is memory, and what does that look like in the brain? The other questions examine whether we can artificially tinker with memories in a way that improves the health and wellbeing of an organism—for example, by enhancing positive memories or suppressing negative ones to alleviate certain symptoms of psychiatric or neurodegenerative disorders.
What are some of the research projects underway in your lab?
One project involves predicting which brain cells will go on to hold a particular memory. We monitor the baseline activity of cells in the brains of mice to predict where that memory is going to go, days before the memory is created. We think there are some kinds of pathways, operating like roads and highways, where the “traffic” of memory flows.
Other projects examine how our brain makes decisions when faced with mixed emotional signals. For instance, say you have reservations at your favourite restaurant, but it’s a 10-minute walk and it’s raining outside, so you’re torn between excitement at the prospect of eating a great meal and peaceful joy at the thought of staying comfortably dry at home. How do you resolve that emotional conflict? Like humans, mice can also experience conflicting emotions when making a decision. We investigate how memories are used in the mouse’s decision-making process amid these competing emotions.
Many of our projects investigate how non-neuronal cells contribute to cognition and behaviour. Non-neuronal cells are cells other than neurons that primarily regulate brain health and provide structural integrity. For instance, one project explores the progression of brain cancer and how it affects cognition and behaviour in rodents. While I’m not a cancer biologist (yet!), I am a systems neuroscientist, and my group believes we can apply the tools we use to study learning and memory to investigate how the coordinated activity between neurons and non-neuronal cells makes the healthy brain possible. Then we can map how those underlying dynamics change as the brain deteriorates due to cancer.
Can you describe your research methodology?
Normally, the brain looks like an opaque pink custard, with little visible detail. In our research, we use a set of genetic techniques (or as I sometimes like to say, a bit of “genetic trickery”) to make individual brain cells glow in specific colors, like green and blue, allowing us to see which ones are involved in memory. We use a method called optogenetics—where light pulses are used to turn specific cells on and off—to make certain memory cells glow green when they are activated, which helps us see them amid a sea of non-activated blue cells and thus helps us pinpoint which cells are holding onto a particular memory. We then use specialized microscopes to track the activity of these cells while the animal performs tasks like turning, remembering, or even sleeping. This lets us measure and manipulate memory-bearing cell activity.
Why does research on rodent brains help us better understand human brains?
We study memory as this ubiquitous phenomenon that exists everywhere that life exists. By examining the biological correlates of memory in rodents, we create a rough framework to make predictions about human memory processes. This cross-species approach allows us to gain insights into how memories guide daily actions.
Optogenetics is too invasive for humans. Scientists who study human memory use less invasive approaches that build on principles learned from rodent models. Instead of using implanted optic fibres to activate memories like we do with rodents, researchers can activate memories in humans with simple cues, such as asking, “How was your dinner last week?” These memories can then be monitored using minimally invasive techniques like an EEG (electroencephalography), which measures large-scale electrical brain activity through the scalp, or fMRI (functional magnetic resonance imaging), which uses magnetic fields to capture images of blood flow activity in the brain.
I think of the mouse brain as a tricycle and the human brain as a Lamborghini. If the research question concerns how a sophisticated motor can make something travel 120 miles per hour, studying the tricycle won’t suffice, but as long as we frame questions in a way that fits with the biology of rodents, much of what we learn in neuroscience research can be translated between humans and rodents.
When did you first know that you wanted to study neuroscience?
I first became curious about the brain and its composition in middle school. I remember using an early version of Google to search “What is a brain made of?” and “What color are brain cells?” On family trips to El Salvador, I started carrying books on consciousness along with my comic books so I could balance diving into the adventures of Spider-Man with diving into the mysteries of the brain.
I entered BU as an undeclared major with many diverse interests, from music to natural and medicinal sciences. It wasn’t until my junior year that I met Paul Lipton (who was then the director of undergrad neuroscience at BU). I told him, “I like music, I like Shakespeare. I once thought I wanted to be a doctor, but now I don’t know what I want to do with my life.” Paul’s response was eye-opening: “Why not study the thing that gave us Beethoven’s Fifth, Hamlet, and Spider-Man—the thing that helped us travel to the moon?” That was the “aha” moment where I realised studying the brain would give me indirect access to everything else that interested me.
What’s your favourite thing about working at Boston University?
Everyone here is comfortable sharing success. In seven years, I haven’t had one conversation that revolved around claiming sole credit. My vision for neuroscientific research is like NASA’s rover landing—everyone cheering together. Solving the mysteries of brain won’t require one Einstein, but a whole team. Whether it’s a grant, a student’s success, or a new discovery, everyone contributes.
What are your favourite activities outside of science?
Running and boxing. I come from a running family—my dad, at 72, still runs eight miles a day. Boxing is a newer obsession. It really helps me to focus on the moment—especially when there’s someone trying to punch me!
What’s a fact about you that surprises people?
I never learned to walk down stairs properly as a kid. I have a memory of holding my mom’s hand and feeling convinced that, if I didn’t put my whole foot on the stair, I’d fall. So, I learned to walk down the stairs with my feet sideways. To this day, I take a second to get my footing before going down a staircase.
Interview conducted and edited by Tanvi Agrawal (CAS ’27) and Jim Cooney