Upcoming Events

April 1, 2024
3:30 p.m., Goergen 101 and on Zoom

Optics Colloquium: Guillaume Baffou, CNRS researcher at Institut Fresnel, Marseille (France)

High-Resolution Wavefront Microscopy for Applications in Bio-Imaging, Nanophotonics and Micro-Scale Thermometry

Cross-grating wavefront microscopy (CGM) is an optical technique capable of mapping the wavefront distortion of objects lying at the sample plane of a microscope, with a diffraction limited resolution. CGM is based on the use of a 2D diffraction grating placed at the vicinity of a camera sensor. In this presentation, I will introduce the CGM technique, and detail the applications we recently tackled in bio-imaging and nanophotonics. In particular, I will explain how CGM can be used as a temperature microscopy technique, in particular for applications involving laser heating of plasmonic nanoparticles. I will show how CGM can measure biomass density and single-cell growth rate in bacteria populations, and neurons in culture. I will finally explain how CGM can be used as an ideal metrology tool in nanophotonics, by measuring the complex optical polarizability of nanoparticles, the complex refractive index map of 2D materials, and the wavefront distortion of metasurfaces.

Biography: Guillaume Baffou is a CNRS researcher working at the Institut Fresnel, Marseille (France). He is a graduate of the École Normale Supérieure de Cachan (ENS Cachan, recently renamed ENS Paris-Saclay). He passed the 'agrégation' in physics in 2003 and received his master's degree in solid states physics in 2004, from Université Paris XI. After a Ph.D. degree in Nanoscience at the Université Paris XI in 2007, he moved to the ICFO, Castelldefels (Barcelona) for a 3-year-long postdoc on plasmonics and associated photothermal effects, under the supervision of Prof. Romain Quidant. In 2010, he was appointed CNRS researcher at the Institut Fresnel, Marseille (France) in the Mosaic group.

Guillaume Baffou was awarded the Bronze Medal of the CNRS in 2015. In 2018, he obtained an ERC Consolidator grant to lead research activities at the interface between physics and biology at small scales. In 2023, he was awarded a Fulbright grant to work in the biological sciences department at Columbia University, NY, for a year.


April 3, 2024
12:00 p.m., Kresge Room, 269 Meliora Hall

BCS Lunch Talk: Howard Li, BCS Graduate Student, Advisor: Michele Rucci

Tuning visual sensitivity via eye movements

What determines spatial selectivity in the visual system? Standard views rely on the assumption that spatial tuning, along with information about space in general, is directly inherited by the relative position of photoreceptors and shaped by the static patterns of neuronal connectivity. However, the human eyes are always in motion, so that retinal neurons, which are highly sensitive to input fluctuations, receive temporal modulations that depend on the interaction of the spatial structure of the stimulus with eye movements. It has long been hypothesized that these modulations might contribute to spatial encoding, a proposal supported by several recent observations. A fundamental, yet untested, consequence of this encoding strategy is that spatial selectivity is not hard-wired in the visual system, but critically depends on how the motion of the eye shapes the temporal structure of the signals impinging onto the retina. Using high-resolution techniques for gaze-contingent display control, here we quantitatively test this prediction in two parallel experiments.

In Experiment 1, we focused on sensitivity during fixation. We manipulated the spatiotemporal stimulus on the retina to replicate the effects of various amounts of fixational motion. We show that contrast sensitivity varies with retinal motion in proportion to the strength of the luminance modulations delivered within a narrow temporal bandwidth. Furthermore, physiological variability in fixational control affects visual performance, as predicted by spontaneous trial-to-trial changes in the structure of the visual input flow. In Experiment 2, we measured visibility following saccades. We show that the perceived contrast of low spatial frequency targets is enhanced with larger saccades, consistent with the difference in input strength delivered by different saccade amplitudes.

By identifying a key role for oculomotor activity in spatial selectivity, these findings have important implications for the perceptual consequences of abnormal eye movements, the sources of inter- and intra-subject perceptual variability, and the function of oculomotor control.


April 5, 2024
1:00 p.m., URMC 2.6408 (K207 Auditorium) & Zoom

FEI Basic Science Seminar: Machelle T. Pardue, Georgia Tech & Emory University

Investigating mechanisms of myopia using mouse models

Prevalence of myopia continues to increase with a predicted 50% of the world’s population having myopia by 2050. While environmental factors have been implicated, our understanding of the mechanisms controlling myopic eye growth are limited. I will discuss our work to investigate the specific retinal pathways that may be involved in refractive eye growth using a mouse model of myopia. I will focus on the influence of different ambient light conditions, the contribution of photoreceptor pathways, and the potential molecular candidates in retinoscleral signaling.


April 10, 2024
3:00 p.m., Rm 2-6408, K207 Auditorium (in-person only)

Boynton Colloquium: Trent Watkins, UC San Francisco

The Double‐Edged Sword of Stress Signaling in Optic Axons

Developing new therapies to preserve and restore vision in glaucoma and after traumatic optic nerve injury will require an improved understanding of the mechanisms that underlie retinal ganglion cell (RGC) neurodegeneration and limit repair. In our studies, we seek to decipher the transcriptional programs that are activated in response to RGC axonal insults, as these play critical roles in determining the fates of these neurons in disease and injury. Our efforts have helped to define the function of the axonal stress-responsive Dual Leucine-zipper Kinase (DLK) in engaging multiple response pathways with broad impacts on the RGC gene expression. Importantly, blockade of DLK is neuroprotective in models of glaucoma and injury, though we have found that inhibition of this stress response also limits RGC axon regrowth enabled by an experimental regenerative intervention. We’ve further identified the Activating Transcription Factor-4 (ATF4) as an essential mediator of these pro-regenerative and proapoptotic responses in conjunction with the parallel activation of the transcription factor c-Jun. Capitalizing on the coordinated stimulation of ATF4 and c-Jun by DLK signaling, we’ve developed a strategy for augmenting the axonal stress response, finding that, under normal, regeneration-refractory conditions, amplifying DLK activity accelerates RGC loss but, when combined with a regenerative intervention, enhances axon regrowth. Our studies therefore suggest that the coordinated transcriptional programs that drive neurodegeneration might instead be harnessed as part of efforts to restore function in the CNS.


April 24, 2024
3:00 p.m., Rm 2-6408, K207 Auditorium

Boynton Colloquium: W. Martin Usrey, UC Davis

Feedforward and Feedback Interactions between Thalamus and Cortex for Vision

The thalamus and cerebral cortex are interconnected by a dense network of feedforward and feedback circuits. In the visual system, the response properties of neurons in the lateral geniculate nucleus (LGN) of the thalamus and primary visual cortex (V1) are governed by the anatomical organization of these connections and the temporal patterns of impulse arrival. Results will be presented from experiments using multielectrode recordings and optogenetic manipulation to examine the specificity of neuronal connections and the role of spike timing and behavioral modulation in the reciprocal exchange of information between the LGN and V1 in the alert macaque monkey. These results reveal a striking relationship between the parallel feedforward and feedback processing streams, as well as the biophysical properties that govern spike transfer and the encoding of visual information in neuronal spike trains.


July 11-12, 2024

Consortium for Vision and Oculomics in Psychiatry

We are excited to announce that the first annual meeting of the Consortium for Vision and Oculomics in Psychiatry (CVOP) will be held in Rochester, NY on Thursday, July 11 and Friday, July 12, 2024.

The online submission portal is now open. Proposals for presentation at the meeting will be accepted via the submission portal through February 28th, 2024 at 5:00pm Mountain Time (MT). Access the submission portal online. Submissions must come from CVOP members. All members (Full, Associate, Student) are encouraged to submit. Membership is free, and you can submit an application online.

Download the Call for Abstracts. Please review carefully for detailed information on submission types, formats, and guidelines.

Additional information about conference registration is coming soon and will be posted to the CVOP website and announced on the listserv.

For questions not addressed in the Call for Abstracts or in the information above, you may contact Steve Silverstein at .

Please feel free to share this announcement with your labs and colleagues—we hope to see you there!

Sincerely,
2024 Program Committee, Steven Silverstein (Chair), Sonia Bansal, Deepthi Bannai, Paulo Lizano, Michel Maziade, Robert Reinhart, Katy Thakkar, Bilge Turkozer, Siegfried Wagner