James Zhuang
BME PhD Proposal Presentation

Date: 2025-09-10
Time: 3:30 PM - 5:00 PM
Location / Meeting Link: Location/ Meeting Link: EBB 4029 ; https://gatech.zoom.us/j/8140108680?pwd=Q3Azc2VhWGFJMXRLWGdOZHFoV09iZz09&omn=98087746917

Committee Members:
Bilal Haider, Ph.D. (Advisor); Mark H. Histed, Ph.D.; Garrett B. Stanley, Ph.D.; Ming-fai Fong, Ph.D.; Hannah Choi, Ph.D. 


Title: Modifying visual perception by activating layer 4 (L4) excitatory neurons in mouse primary visual cortex (V1)

Abstract:
We use visual perception to guide our everyday decisions. The process of visual perception begins when light enters the eye and is converted into neural activity by the retina. This neural activity is eventually transmitted to the primary visual cortex (V1) and then to higher visual areas in the form of spikes. Neural recordings in V1 during visual detection tasks have established that neurons in V1 play a critical role in driving visual perception: generally, the stronger the spiking of V1 excitatory neurons, the more likely the subject is to perceive a stimulus. The overall goal of this proposal is to understand how excitatory neurons in layer 4 (L4), the first stage of cortical visual processing, contributes to visual perception. We hypothesized that increasing activity in L4 excitatory neurons can modify visual perception by improving the detection of visual stimuli. We tested this hypothesis in transgenic mice expressing a light-sensitive protein in V1 L4 excitatory neurons by directly activating these neurons with blue laser light while mice perform a visual detection task. We expect mice to detect visual stimuli more frequently on laser trials compared to trials without laser. Laser trials showed significantly enhanced visual detection in 3 mice (p<0.05) but strikingly 7 mice exhibited significantly suppressed visual detection (p<0.05). Recordings in V1 revealed neural activity differences underlying these disparate behavioral effects: during laser trials enhanced mice had greater increases of spike rate than suppressed mice (p<0.05). Additionally, the magnitude of this change in spike rate was significantly correlated to the change in the stimulus detection rate on laser trials for each individual neural recording (r = 0.344, p = 0.035; n = 10 mice, 30 neural recordings). Next, we propose to investigate the consequences of these differences of neural activity on higher visual areas downstream from V1. We propose to perform the same experiments described above while simultaneously recording neural activity from V1 and its downstream higher visual area LM. Together, this proposal reveals that the very first stage of cortical visual processing, L4, plays a powerful role in modifying perception of the visual world.