Thesis Seminars

Dennis Jung, MS - PhD Candidate, Neuroscience Graduate Program

Working memory (WM) enables temporary maintenance and manipulation of task-relevant information. One important role of WM is preventing information loss during distraction. While neural oscillations are known to support WM maintenance and distractor resistance, less is understood about how anticipation influences these processes. This thesis investigated neural oscillations in WM during distractor anticipation. To test this, we recorded local field potentials (LFP) in the lateral prefrontal cortex (LPFC), a key brain area for WM, and scalp electroencephalograms (EEG) from monkeys performing modified memory-guided saccade (MGS) tasks, with varying in distractor timing and item load. The first experiment tested how distractor anticipation influences brain oscillatory dynamics with fixed distractor timing during memory maintenance. We found widespread thetaband (4-8 Hz) EEG activity better encoded the memory item after, rather than before, the anticipated distractor time, regardless of whether the distractor appeared. However, theta-band LFP activity in the LPFC only encoded the item when the distractor was presented. These results suggest large-scale theta oscillations reflect WM dynamics associated with both maintenance and distractor anticipation, while small-scale theta oscillations in the LPFC specifically encode the stored item, ensuring stability. The second experiment varied distractor timing. We found greater behavioral impairment when the distractor appeared towards the end of the task. EEG theta activity continued encoding item—greater towards the end of maintenance, regardless of the presence of the distractor. Similar encoding was observed for the LFP theta activity only when the distractor was shown. These results suggest WM becomes more vulnerable to distraction over prolonged maintenance, but greater encoding of items may reduce deteriorating distractor effects. The third experiment explored effects of increased item load and internal selective attention on distractor anticipation. Selection increased encoding of an attended item in EEG and LFP theta-band activities. Post-cue distractors tended to increase behavioral errors compared to a single-item conditions in the previous experiments, suggesting increased task complexity and variability impairs distractor anticipation. Together, the results of these experiments demonstrate that the distractor anticipation influences the WM dynamics as reflected in both small- and large-scale oscillatory signals.

Event Flyer

 Jan 29, 2025 @ 1:00 p.m.

 Medical Center | Lower Adolph Aud. (1-7619)

Host: Advisor: Adam Snyder, PhD

Andrea Campbell - PhD Candidate, Neuroscience Graduate Program

Visual impairment affects over 2.2 billion people worldwide, with retinal diseases (RDs) like age-related macular degeneration (AMD) and retinitis pigmentosa (RP) as significant contributors to this impairment. These diseases lead to the degeneration of photoreceptor cells, which lack a natural regenerative capacity in humans. Current treatments primarily aim to slow disease progression, underscoring a critical need for regenerative strategies focused on restoring vision. Photoreceptor precursor cells (PRPCs) derived from human embryonic stem cells (hESCs) and induced pluripotent stem cells (iPSCs) are promising candidates for cell replacement therapies. However, immune-mediated rejection and inflammation remain significant barriers to their success. To address these challenges without relying on prolonged immune suppression, this study evaluates two complementary strategies: (1) short-term systemic immune suppression and (2) co-transplantation of PRPCs with regulatory T cells (T-regs).

Aim 1 evaluates the efficacy of short-term immune suppression in promoting PRPC survival. Prolonged immune suppression increases risks such as infections and systemic toxicity. Inspired by transient protocols in retinal pigment epithelium (RPE) transplantation, this study hypothesizes that a short-term immunosuppressive regimen can promote PRPC survival while minimizing adverse effects. Advanced adaptive optics scanning laser ophthalmoscopy (AOSLO) will facilitate non-invasive, longitudinal imaging of PRPC survival and host immune responses at cellular resolution.

Meeting ID: 944 0302 2429
Passcode: 903589

Aim 2 examines the co-transplantation of PRPCs with T-regs to locally modulate immune responses. T-regs play a key role in immune tolerance and may provide a localized, cellular alternative to pharmacological immune suppression. By dampening inflammation and inhibiting cytotoxic T-cell activity, T-regs could enhance PRPC survival. Using fluorescent reporters and high-resolution imaging, this study will track immune activity, T-reg function, and PRPC survival in real-time, assessing the potential of T-regs to mitigate rejection.

This research integrates cutting-edge imaging technologies, fluorescent reporters, and an NHP model that closely mimics human retinal anatomy, physiology, and immune responses. By leveraging these innovations, the study seeks to advance regenerative therapies for retinal diseases, providing insights into immune modulation and stem cell-based interventions. Success in these strategies could pave the way for safer and more effective treatments for RD patients, addressing an unmet medical need and establishing a framework for future cell-based therapies in ophthalmology.

 Jan 13, 2025 @ 11:00 a.m.

 Medical Center | K307 (3-6408)

Host: Advisor: Juliette E. McGregor, Ph.D.