Author Archives: Megan Stone

Time Is Weird. Isn’t It?

You could tell me that the beginning of this program was 6 months ago or yesterday, and I would believe you.   It feels both like I’ve been here for forever and yet somehow just arrived.  While this may make the idea of hopping on a plane instead of the C1 shuttle seem odd, I wouldn’t rather it be any other way.  

On one hand, I’ve learned so much in these last 7 weeks.  Whether it be surgical procedures, data analysis code, or imaging techniques, it is crazy to think about how many skills I have acquired.  From this perspective, it feels like I’ve been in the lab forever.  Simply, the depth of exposure I have gained in the lab does not seem like it would have happened in such a short timeframe.  It’s been a wonderful experience to be fully immersed into the lab culture, and by becoming a part of the lab I feel as though it has also become a part of me.

On the contrary, where has the time gone?!?  I could have sworn that, just yesterday, I was picking up a pipette for the first time.  I guess people are not joking when they say “time flies when you’re having fun.”  Especially after a year of being virtual, I really enjoyed learning hands-on in the lab.  Moreover, I find the questions we’re asking fascinating, and getting to be a part of answering them has been incredibly rewarding.  The overall atmosphere is truly one where intellectual curiosity thrives.  I came into knowing that I would be challenged, and that is what made every day exciting. 

I am immensely appreciative of my mentors who made this such a wonderful experience.  I now have a more profound understanding and appreciation for research, but I know this is only the beginning. Although this program may be over, I know my time working in the lab is everything but.  I’m incredibly grateful that the Glickfeld lab has allowed me to continue working with them in the fall.  I can’t wait to see not only how projects I’ve been working on develop but also how I will continue to grow as a researcher.


Using DART for Cell-Type Specific Interneuronal Inhibition

Megan Stone

Mentors: Jennifer Li, Lindsey Glickfeld, Ph.D.

Department of Neurobiology

It has been thought that varying subtypes of interneurons have different roles in controlling the neuronal circuits that drive visual perception.  This has been primarily studied through the activation or inhibition of specific interneuron populations through the use of optogenetics (which has limited clinical applications) or non-selective pharmacology (which is prone to off-target effects).  This study aims to further understand the roles of parvalbumin (PV) and somatostatin (SST) expressing interneurons in the mouse primary visual cortex (V1).  This will be achieved by selectively inhibiting their activity through a recently developed technique: Drugs Acutely Restricted by Tethering (DART).  Unlike optogenetics or non-selective pharmacology, this technique will allow us to selectively inhibit specific interneuron populations in a clinically feasible manner.  Thus, we expect to see suppressed responses in PV and SST cells, following an electrical stimulus, in comparison to the control.  Overall, these findings will contribute to the overall understanding of the function of  PV and SST interneurons in neuronal circuits and add to the knowledge of mechanisms driving perception and visually guided behaviors.  Additionally, this study seeks to validate the use of DART as a technique to manipulate specific neuronal populations within V1.

Diversity in Future Directions

This week, I really enjoyed seeing what everyone was working on in their labs.  There was an impressive amount of variety, and everybody’s topics were incredibly interesting.  8 minutes is not a lot of time to capture one’s project, and while there are many people I would love to follow up with and learn more from, I found myself particularly drawn to the chalk talks that were most closely aligned with my own project.  In particular, listening to Bryan talk about the development of HaloTag.

Through my own project, I was aware that HaloTag technology was recently developed at Duke.  However, my focus has centered around the applications juxtaposed to the creation and engineering of the ligands.  Hearing Bryan talk about the development of multiple types of HaloTag, each with its own cell-specific applications, opened my eyes to how powerful this technology could be.  The notion that they could design a ligand to specifically bind to thereby manipulate any type of receptor is insane and has seemingly endless pharmacological applications!  The work he is doing in determining the optimal ligand-receptor pairs was incredibly interesting.  It made me realize the diversity in future directions of research which is exciting and one of the facets I love about it!

I can do surgery?!?!

Life in the lab varies from day to day, but most consist of at least one of the following: observing or doing surgery, slicing / imaging / recording from visual cortex (V1), or figuring out Matlab.  Performing surgeries on mice has definitely been the most surreal part of working in a lab.  There have been multiple times where I stop and ask myself “who let me do this?”  That said, it has also been the coolest part.  So far, I’ve learned how to do two surgeries (burr hole injections and perfusions) but I’ve done significantly more burr holes than perfusions.  Although I’ve only performed those two types of surgeries, I’ve observed others in the lab doing other kinds of surgery.  Everyone I’ve shadowed has been great in answering any questions I have about the surgery, and overall it’s been incredibly rewarding to witness.  So far, I’ve mainly done practice surgeries and have been injecting dye into V1 instead of the actual virus.  However, last week we began injecting the virus.  This is exciting because it means that we’re going to be able to start collecting data over the next couple of weeks.

We collect our data by slicing the brain and either imaging the slices or recording cellular activity. With the practice dye injections, I’ve only imaged under a microscope.  We were able to see where I injected the dye (and whether or not it was where I was supposed to inject it).  We got decent results, and it was nice to get some validation that the surgeries I was doing worked.  I’ve also enjoyed learning to use all the equipment because it makes me feel like I can be more independent.  Once we finish up the virus injections, and wait a couple of weeks to get it to express, we’ll begin recording from live cells.  I’m hopeful that we’ll see good results.

Finally, Matlab is the program we use to do our analysis.  For this project, we use it to create graphs of cellular activity (that we’ll collect from the recordings) across different conditions.  Given that I have zero prior coding experience, there is definitely a learning curve that I haven’t quite reached yet.  However, once I become more comfortable with Matlab, it will be cool to see our results and be able to tell whether our experiments worked.  

Overall, my time in the lab has had a healthy amount of variety.  It has been a good balance of building a repertoire of skills while focusing on perfecting the ones that are particularly relevant to the work I’m doing.  It’s crazy to think that I’m working towards the point of being able to carry out experiments with minimal help.  I love that I’ve been able to learn so much in such little time and that every day brings new opportunities to learn even more!


The Journey Ahead

Currently, Dr. Glickfeld’s work involves the organization of neural circuits in the visual cortex and how they drive behavior, but that wasn’t always her plan.  Although science had always been an interest of hers, she went into her undergraduate at Stanford planning to study genetics.  Actually, her transition into neuroscience was somewhat by accident.  In the first year, Dr. Glickfeld received and responded to an email about an open research position.  She initially thought the lab was studying genetics but, during the interviews, she quickly realized it was more neuroscience based – a field she had virtually no prior knowledge in.  She said that her mentor had to explain even the most basic neuroscientific principles, such as what an action potential is.  This resonated with me because I have also had to have many topics explained to me.  Particularly, I have never taken a physics class, so anything pertaining to electrophysiology (or electrical currents in general) is very new to me.  Nevertheless, Dr. Glickfeld liked the people and the lab environment, so she decided to give neuroscience a try.  She quickly fell in love with neuroscience, stayed in that lab for the remainder of her undergraduate, and has now devoted her career to the field.  

Dr. Glickfeld accredits her mentors to “how [she] thinks about science,” and it’s easy to see how her past experiences are reflected in the work she does today.  In her approach to studying neural circuits, she emphasizes both the microscopic connections at the level of individual synapses as well as a more macroscopic perspective of how the neurons form a network that drives behavior.  The lab she worked in during her undergraduate was primarily focused on mechanisms of synaptic transmission which emulates the former part of the work she’s doing now.  During graduate school at UCSD, there was a shift towards a more holistic approach and viewing neurons as a part of a larger network.  In her postdoc at Harvard, she began working particularly with the visual system.  Thus, it’s easy to see how her current work and interests are a culmination of her background.

I really enjoyed Dr. Glickfeld’s story because it helped me put things into perspective.  Like her, I’ve always known I want to go into science, but I’ve also gone back and forth as to what that actually means for me in terms of specific career paths.  At the end of our conversation, I asked her if she had any tips for upcoming scientists (aka me) and she said that her best advice is that if you’re doing the best science you can do and enjoy what you’re doing, the rest will work itself out.  For me, this was reassuring because it is both tangible and broad.  In a sense, I can create a mental checklist for myself and see that I am accomplishing those two things.  Yet, it still leaves for life to throw in the unexpected.  Also, hearing about how her mentors have influenced her and her career is comforting because it ensures me that research manifests an overall supportive environment where everyone is on their journeys together.  Overall, I’m very grateful to be able to have this experience and I hope that it will shape me in the way that Dr. Glickfeld’s background has shaped her.


A Game of D.A.R.T.s

One thing that I think is cool about the brain is that it’s the only organ that studies itself.  The brain operates through a series of complex networks composed of neurons.  The neurons transmit signals by sending electrical impulses to one another and releasing neurotransmitters.  Neurotransmitters are chemical proteins that bind to receptors to activate the systems responsible for our perception, behavior, and other bodily functions.  Different parts of the brain are connected by these circuits, and although we’ve learned a lot about how neural circuits work, there’s still much that remains unknown.  

This summer, I’ll be working to better understand the role of specific types of neurons (parvalbumin-expressing (PV) interneurons) in the neural circuits of a specific part of the brain (primary visual cortex (V1)).  We’re using a technique called Drugs Acutely Restricted Tethering (DART) to manipulate the activity of PV interneurons.  DART works by using a “buddy system” where the drug we’re using is paired with a DART protein.  The two proteins are linked together so that, when DART binds to a receptor, the drug is subsequently confined and can only bind to nearby receptors.  The type of receptor we’re studying is found all throughout the brain, so using this technique allows us to be more specific in what area of the brain we’re treating and minimize off-target effects. 

However, in order for this technique to work, the DART protein needs a specific receptor to bind to that is only expressed in the areas where we want DART to bind.  Thus, we are first injecting a virus that will facilitate the expression of the HaloTag receptor on the surface of PV interneurons.  Ultimately, HaloTag will serve as an anchor for DART which is connected to a drug that will in-turn be confined so that it can only bind to certain receptors so that we can manipulate the overall activity of the cells.  This will not only give us a better understanding of the role of PV interneurons in neural circuits but also validate the use of a new technique for interneuronal manipulation that could aid in the development of clinical therapies for neurological disorders. 

Part of Your World

Ever since I can remember, people have been asking me variations of the question “what do you want to do with your life?”  When I was as young as 4 years old, it manifested itself in the ever-so-popular “what do you want to be when you grow up?”  Now, it’s evolved into a more mature “what is your area of study?” or “future career path.”  Regardless of how it’s phrased, it’s all the same question.  When I was in kindergarten, I wanted to become a Disney princess.  13 years and some minor adjustments later,  I’m considering a career in research neuroscience.  But likewise, I have minimal experience actually doing it.  I was first introduced to the world of research and scientific literature in the latter part of high school and have since become somewhat well versed in the products of research.  I’ve also shadowed in the lab I’ll be working in for the last couple of months, so I’m starting to get a better idea of the process as well.  

This summer, I’m most looking forward to learning how to actually do research. Especially after a year of virtual learning, I’m eager to get some hands-on experience.  I’m excited to become familiar with various techniques and hopefully gain more independence.  The transition from discussing research to becoming a working member of the lab will teach me new skills that will be invaluable. I also hope that the experience will be rewarding and propel my desire to pursue a career in neuroscience.