Senior Project Week 2- Refining Methodology and Experimental Design for Neural Signal Propagation Experiments

This week focused on refining the experimental design for the project and continuing the literature review related to anesthetics, ion channels, and neural signal propagation. While the first week concentrated on building a broad understanding of the field, the goal this week was to translate that background knowledge into a concrete experimental methodology that can be implemented once the lab work begins.

A significant portion of the week involved identifying the specific experimental setup that will be used to measure neural signal propagation. After reviewing common electrophysiology methods used in nerve studies, we determined that the experiments will measure compound action potentials using multiple electrodes placed along an isolated nerve. Using more than one recording electrode will allow us to measure the latency between signals traveling along the nerve. From this delay, it will be possible to calculate conduction velocity and analyze how various compounds influence signal propagation.

Another important decision involved selecting the biological model system. Early experiments will use worm nerves, which are relatively accessible, as they fit well within the budget for large sample size and repeated trials, and thus allow for easier initial testing of the recording setup and experimental conditions. Once the methodology is well established and the system is producing reliable signals, later experiments will transition to lobster nerves. Lobster nerve preparations are commonly used in neurophysiology because they are larger and easier to manipulate experimentally, which can provide clearer electrophysiological recordings and allow for more precise measurements.

In addition to selecting the experimental model, I spent time reviewing physiological solutions that can maintain nerve viability outside the organism. Ringer’s solution will be used to bathe the isolated nerve during experiments, and identifying the correct ionic concentrations is critical. If the solution contains incorrect concentrations of sodium, potassium, calcium, or chloride ions, the nerve may lose excitability or die prematurely. Because of this, I reviewed several protocols describing Ringer’s solutions used in nerve physiology experiments to ensure the formulation we prepare will maintain stable neural activity.

Another focus this week was thinking carefully about experimental reliability and statistical validity. Increasing sample size and repeating trials are essential for ensuring that observed effects are real and not simply noise in the data. For each experimental condition, multiple trials will be conducted so that changes in conduction velocity or signal amplitude can be evaluated with greater confidence.

I also began identifying factors that could unintentionally influence the data. For example, different types of nerve fibers can conduct signals at different speeds depending on whether they are myelinated or unmyelinated. Although the early preparations are likely to involve primarily unmyelinated fibers, this variability still needs to be considered when interpreting results. Other potential issues include excitotoxicity, where excessive stimulation or chemical exposure damages the nerve, and errors in Ringer’s solution preparation that could alter ion concentrations and affect neural activity.

Carefully thinking through these potential confounding factors is important because electrophysiology experiments can be highly sensitive to small environmental changes. Temperature, solution composition, electrode placement, and stimulation intensity can all influence the recorded signals. By identifying these variables in advance, we can design experiments that minimize unwanted variation and produce more reliable measurements.

Next week the focus will shift from planning to validation of the experimental setup. Working with Dr. Joaquin Cury and Dr. Claus Peter Richter, we will begin testing the recording system by measuring compound action potentials in the nerve preparation. Lidocaine will be applied as a control compound to confirm that the electrodes are accurately detecting changes in signal propagation when sodium channels are blocked. Once the recording system is validated, we will continue optimizing the Ringer’s solution and experimental conditions needed to maintain nerve viability for extended periods.