Hi, my name is Jesse Cao, I am a second year medical student at PCOM Georgia, and today I will be talking about my study investigating the thalamic neuronal activity change in reaching behavior pre and post TDCS in mice. So osteopathic medicine is built on the principle that the body's structure and function are interconnected and that the body has an ability to restore itself when these systems are imbalanced. And our study really aligns with this principle by understanding how transcranial direct stimulation or TDCS, which is a non-invasive neuromodulating technique, can restore the cerebellothalamocerebral pathway, which is essential for motor coordination. In spinal cerebellar ataxia, this pathway is disrupted, leading to motor dysfunction and loss of motor coordination. By applying TDCS, we aim to study its effect on thalamic firing rate and how this would potentially restore the function of the thalamus. It is hypothesized that a change in thalamic neuronal activity occurs pre-TDCS and post-TDCS during the reaching behavior in mice. So for the methods, we had two normal mice acclimated to water restriction. This was used to elicit a reaching behavior where we can have a recording electrode down into the thalamus to obtain an electrophysiology recording during this reaching behavior. And prior to the acclimation to water restriction, we performed a head-plated surgery so that the mice can be mounted on a head-fixed apparatus to study the reaching behavior as well. In figure 1a, we can see the experimental setup. And in 1b, here is a thalamus with the ventral medial and ventral lateral nucleus in the thalamus highlighted. This is where we will lower the recording electrode and obtain our electrophysiology recording. In figure 1c, this is a schematic drawing of the reaching behavior where the mouse is reaching for the water as shown by the water apparatus. And here is a recording electrode. And here is the head plate. So for the reaching behavior, we used a markerless post-estimation software called DeepLabCut or DLC. And this was used to analyze the reaching behavior of the mice during this electrophysiology recording. For the background of spinal cerebellar ataxia, this is a progressive neurodegenerative disease that is inherited in an autosomal dominant manner. Clinically, patients diagnosed with SCA exhibit dysmetria, dysthytokinesia, abnormal gait, and visual motor deficits. Looking at figure 2, this is a 2D output of DeepLabCut or DLC. So reaching behaviors were recorded for 10 seconds with each second having 100 frames. So in total, it would be 1,000 frames. By using DeepLabCut, we were able to manually locate the reaching paw. And with its convoluted neural network and machine learning skills, DeepLabCut was able to take our manual input and apply this to all 1,000 frames. For example, if we had 10 trials, then it would be 10,000 frames. So here, each blue dot represents one frame. So we would have 1,000 frames for this one trial. And basically, DeepLabCut was able to estimate and predict where the paw would be at a specific point in time while the mouse was reaching for the water droplet shown in red here. The light blue represents the resting bar, and the green represents the reflection of the reaching paw. With this, we were able to use MATLAB and generate an x displacement versus time. So we can see that between 4 and 6 seconds, this is when the reaching behavior occurred. With the recording electrode, we were able to generate an e-fizz recording that showed our thalamic activity during this reaching behavior. So by setting a bandpass filter of 300 to 10,000 hertz, we were able to filter out the multi-unit spike potential from this raw data, which is shown here. And using a Gaussian distribution, we were able to smooth out this multi-unit spike potential and generate a graph that showed our thalamic neuron firing rate change. In terms of the results, each different color line represents a different trial. So we had 10 trials pre- and post-TDCS. This solid black line here represents the average thalamic neuron firing rate change, as was this black line over here. So just by looking at these two graphs, we can already see that TDCS does have a modulating effect on the thalamic neuron firing rate. Given the p-value is less than 0.05, this change is statistically significant, showing that TDCS does have an effect on thalamic neuron firing rate. So in the future, we want to have more recordings with improved qualities, and we want to also collect data using ataxic mice. So in conclusion, thalamic neuron activity change occurred pre- and post-TDCS, indicating a potential therapeutic effect of transcranial stimulation for spinal cerebellar ataxic patients. Thank you so much.

thalamic neuronal activity

transcranial direct stimulation

spinal cerebellar ataxia

motor coordination pathways

DeepLabCut software