​Graduate Students Seminar

Seminar | April 9 | 12-1 p.m. | 489 Minor Hall

 Stephanie Wan, UC Berkeley, Fleiszig Lab; Kathryn Bonnen, University of Texas at Austin, Huk Lab

 Neuroscience Institute, Helen Wills

Stephanie Wan’s Talk Title: Impact of contact lens wear and dry eye on the amicrobiomic status of the murine cornea

Abstract: Contrasting with the conjunctiva and other exposed body surfaces, the cornea does not host a stable bacterial population (amicrobiomic). Yet, the cornea and conjunctiva are not usually distinguished in ocular surface microbiome research. Additionally, commonly used sequencing technologies detect nucleic acid, not bacterial forms. Here, Fluorescence In-Situ Hybridization (FISH) with a universal bacterial 16S rRNA gene probe was used to visually determine if contact lens wear or dry eye disease facilitate exposure to environmental bacteria at the corneal surface. Bacteria were cultured from 9 out of 10 contact lenses examined. Corynebacterium and Coagulase-Negative Staphylococcus spp. were most commonly identified from the lenses. FISH showed significantly more bacteria residing on the posterior lens surface (3.72 +/- 4.22 bacteria/field of view) closest to the cornea compared to the anterior lens (2.436 +/- 6.33 bacteria/field of view) (P < 0.05. Mann-Whitney U-test). For EDE corneas, FISH showed few bacteria (4.55 +/- 5.27 bacteria/field of view), not significantly different from untreated controls (1.99 +/- 2.904 bacteria/field of view) (P > 0.05, Mann-Whitney U-test). Environmental bacteria can colonize the posterior surface of mouse contact lenses worn on an extended wear basis without corneal infection. Microbial forms are absent from mouse corneas with dry eye disease, suggesting the associated irritation/inflammation occurs without disruption to mechanisms that normally prevent bacterial colonization of the cornea.

Kathryn Bonnen’s Talk Title: Encoding and decoding 3D motion

Abstract: Much is known about how retinal stimulation is processed through later stages of the visual system. But understanding the meaning of these cortical activity patterns for making inferences about the dynamic three-dimensional environment is a distinct computational problem. We show that treating patterns of retinal stimulation as proxies for the visual world oversimplifies the problem of how neural activity can be read out to infer the properties of the environment. This is because the projection of the environment onto the two retinas fundamentally shapes the information available in the tuning and responses of cortical neurons. In the case of three-dimensional (3D) motion this environment-to-retinae perspective predicts non-canonical shapes of neuronal tuning functions. These non-canonical shapes are consistent with existing electrophysiological recordings in middle temporal area (MT) and explain unintuitive misperceptions of 3D motion in existing psychophysical data.