Hi, my name is Angad Gogia and I am a medical student at the Keck School of Medicine of USC, and the title of my talk is Beta-Band Modulation in the Human Amygdala During a Conflict Response Task. We'll start with some background. The human amygdala is a complex set of temporal lobe nuclei with known roles in fear response, reward-based behavior, and processing emotional conflict. However, the amygdala's role in processing non-emotional conflict is not well known. And that's what we're going to focus on here today. The objective of my talk is to investigate the role of the human amygdala in processing non-emotional conflict. Here's a quick overview of the methods of our investigation. So we conducted our study on phase 2 epilepsy patients, phase 2 meaning that they were implanted with intracranial depth electrodes for seizure localization. We had a total of 5 patients aged between 20 and 61, and they spent a week in the epilepsy monitoring unit after intracranial implantation, and it was during this time we conducted our study. We sampled local field potential data from the macrocontacts at about 2000 Hz, which gave us high temporal and spatial resolution. And we conducted a modified Stroop task, and we'll go a little bit more in depth on the later slides into what exactly that means. On the left here, you can see what one of these intracranial electrodes actually look like. They're about three and a half centimeters long with six cylindrical macrocontacts about five millimeters apart. On the right here is one of our resident neurosurgeons at our institution implanting this electrode for seizure monitoring. Before we do analysis for the local field potential data, we need to actually verify that the electrode contacts are where we think they are. On the right here, you can see a merged postoperative CT scan with a preoperative MRI. And the electrode contact circled in red is located in amygdala gray matter, so we know that that is a contact from which we would want to actually record and analyze the data. Once we get the raw neural signal, we can deconstruct it into its characteristic frequency band, and that's what you see here. The second row from the top is the beta band, and that represents frequencies between 13 and 30 Hz, which is the frequency range that we studied in our investigation. And the reason that we did that is, although the beta band is best known for its role in cortical motor control, there is evidence that in neighboring structures to the amygdala, such as the septal amycnucleus, the beta band plays a role in processing non-emotional conflict. And to be clear, these neural tracings here are not from our patients, but just to characterize the breaking up of the raw neural signal into its characteristic frequency bands. Here is a depiction of the Stroop task, which is actually the non-emotional conflict processing task that these patients will be running while they are in the neuro-ICU. Where I want to bring your attention is to the bottom right, where you see the word red written in the color red, that's the congruent condition, and where you see the word red written in the color blue, which would be the incongruent condition. So these are the two task conditions that we focused on in this study. And the reason that this lets us study non-emotional conflict processing was because in the case where the color matches the word in the congruent case, the patient can say what the normal response that they would want to say is. But in the incongruent condition, where the word red is written in the color blue, it actually requires the patient to suppress the urge to say the word red and actually tell us that the word red is written in the color blue. So just to be clear, in this case, the incongruent condition, the correct response for the bottom line would be to say the word blue, because that is the color in which the word is written. And we compared the incongruent and congruent condition while directly recording the neural signal and looking to see at what power changes there were in the beta band. Here are the spectrogram results for all five patients in our study. Just to orient you, each row is a different patient. The first column is the incongruent condition, so where the text and the color of the words did not match. The second column is the congruent condition, where the text and the color of the words did match. And the last column is isolating beta band power in 13 to 30 hertz for both the incongruent and congruent conditions. So we can zoom in a little bit on the areas of interest. And just to orient you on the spectrograms for each patient, the x-axis is time. The y-axis is frequency. The color red means an increase in power. The color blue is a decrease in power. And the blue polygons encapsulate regions of significant beta band power increase. So at a high level, what you can see here is in the first column, the incongruent condition, for patients 29, 33, and 41, we see significant regions of beta band power increase during the incongruent condition that we don't see during the congruent condition. And the way that that manifests itself in the last column for specifically beta band power is you can see a separation of the red lines in patient 29, 33, and 41 from the blue lines. So that shows that the 95% confidence intervals for beta band power in the incongruent condition were greater than and did not overlap with the congruent condition. And what this represents to us is a statistically significant increase in beta band power in the human amygdala for three out of the five patients during non-emotional conflict processing. This is something that we are really excited about because, to the best of our knowledge, it's a novel finding that the amygdala plays a role in processing non-emotional conflict, which does make sense because it builds directly upon the previously known role of the amygdala in processing emotional conflict. This is also among the first reports of the beta band playing a modulatory role in the amygdala in any capacity. And in this case, that role of the beta band is consistent with previous research that shows that it plays a role in processing non-emotional conflict in the septal amygdala nucleus. Some limitations of our study was that this finding was only seen in three out of five patients. Patients with epilepsy are also known to have changes in their amygdala compared to non-epileptic patients, so it's unclear if this finding would be reproduced in patients without epilepsy. We also had a limited number of failure trials in this study, so most examples that we were able to look at were examples of successful conflict processing, and it's not sure what we would see in the cases where the patients got the answer incorrect. Neural data recording is also inherently noisy, so that may explain why in two of these patients we did not see any modulatory effect, but this is definitely something to look at. Some possible future areas of study include exploring the temporal and functional relationship between different brain areas. For example, the hippocampus and the orbitofrontal cortex are also known to play a role in processing non-emotional conflict, but their relationship to the amygdala in this process has not been well studied. We would also probably benefit from increasing the number of patients and potentially increasing the difficulty of the task to include a higher number of failure trials. It also may be an important area of future study to actually see how noise in the neural recording data can be better filtered, so we can actually have clear neural data to look at. I also just want to take a moment to acknowledge the entire Lee Lab for their contributions to this research, especially my mentor, Dr. Brian Lee, whose support has really been instrumental in my career so far. I look forward to continuing to work with him. This is also just an acknowledgement of a support for our study, and I wanted to thank you all for listening to my talk today.

beta-band modulation

human amygdala

non-emotional conflict processing

intracranial depth electrodes

amygdala's involvement