When I first came to Caltech, one of the things I had no experience with was wet lab work. Pipetting, precise microscope handling, and even the idea of working with live neurons were completely foreign to me. My last two years at Caltech had been dedicated to computational research, so stepping into a wet lab was both daunting and exhilarating. This past term, I took NB/Bi/CNS 162: Cellular and Systems Neuroscience Laboratory, a course required for all Computation and Neural Systems (CNS) majors taught by Professor Daniel Wagenaar. It turned out to be my favorite class and the one I learned the most from, with hands-on experiences that challenged and inspired me every week.
Week 1: Circuits and Electrophysiology Basics
The first week introduced us to electrophysiology through the AxoClamp-2B system and virtual oscilloscope software, ESCOPE. We built simple circuits with resistors and capacitors to understand the fundamental principles of electrophysiology. While none of us had prior experience with circuits, the lab gave us a foundational understanding of how to record and interpret electrical signals—a skill crucial for future experiments. The steep learning curve of setting up circuits and grounding them properly was an initial challenge, but with guidance from professors and TAs, I became confident in handling the equipment and troubleshooting issues.
Week 2: Decoding Neural Responses in Cockroaches
In the second week, we moved from circuits to biology, recording neural responses from cockroach sensory neurons. Using mechanical stimuli applied to leg spines, we explored how neurons encode information about the intensity, direction, and identity of stimuli. It was fascinating to analyze firing rates, which revealed how the structure of sensory spines influences neural responses. Lateral movements, for instance, generated stronger responses due to optimal membrane deformation, highlighting the intricate relationship between physical stimuli and neural activity.
Week 3 and 4: Intracellular Recording in Leech Neurons
The third and fourth weeks introduced us to intracellular recording techniques in the segmental ganglia of medicinal leeches. By measuring resting membrane potentials and action potentials, we delved deeper into the electrophysiological properties of neurons. Leech neurons were an ideal model due to their size and accessibility. Successfully impaling a neuron with a sharp electrode and observing its electrical behavior was an immensely rewarding experience, requiring precision and patience.
Weeks 5-6: Immunohistochemistry and Brain Slicing
In these weeks, we learned the foundational techniques of immunohistochemistry, including brain slicing, antibody staining, and fluorescence imaging. These labs emphasized the meticulousness required in preparing and staining brain tissue to visualize proteins like AVP and neuronal markers. Mastering the vibratome for precise sectioning and using a fluorescence microscope for imaging were particularly challenging yet rewarding tasks. These skills allowed us to explore the structure and function of the brain at a cellular level, providing a new perspective on neuroscience research.
Week 7: Calcium Imaging in Drosophila Larvae
In the seventh week, we used calcium imaging techniques to observe real-time neuronal activity in Drosophila larvae. By stimulating genetically encoded calcium indicators (GCaMP) with blue light, we visualized activity in the mushroom bodies and ventral nerve cord. Analyzing the data with ImageJ/Fiji software helped us understand the spatial and functional differentiation of neural circuits involved in sensory processing and motor control.
Weeks 8-10: Final Project
For the final project, my group investigated the expression levels of the S6 kinase 1 (S6K1) protein in the hippocampus and prefrontal cortex of young mice under fasting, thirsting, and sated conditions. S6K1 is a key regulator of protein synthesis and growth through the mTORC1 pathway, and our goal was to understand how its expression varies with metabolic states. Using techniques such as vibratome slicing, immunohistochemical staining, confocal microscopy, and computational image analysis, we quantified S6K1 levels in specific hippocampal subregions (CA1 and CA3).
Our results revealed significant differences in S6K1 expression: fasting elicited the highest protein levels, while water deprivation led to the lowest. These findings highlight the dynamic responses of neuronal and non-neuronal cells to metabolic stress and their potential implications for brain function and energy regulation. This project was a culmination of the skills and concepts we had learned throughout the term, providing a comprehensive, hands-on exploration of neuroscience. Presenting our findings during the final class session was a rewarding conclusion to this transformative course.
Reflections
NB/Bi/CNS 162 taught me much more than experimental techniques. It showed me how to approach new challenges, troubleshoot issues in real time, and collaborate effectively with peers. The hands-on nature of the course made the learning process engaging and unforgettable. Before this class, I had little experience with wet lab work. By the end, I had not only learned a variety of neuroscience techniques but also developed an appreciation for the meticulousness and creativity required in experimental science.
This course was a defining experience in my journey as a CNS major, bridging my computational research background with practical neuroscience applications. If you’re considering a major in CNS or simply want to dive into the fascinating world of neuroscience, NB/Bi/CNS 162 is a class that will challenge and inspire you in equal measure.
