Oxyopia Postdoctoral Researcher Seminar

Seminar | September 11 | 12 p.m. | 489 Minor Hall

 Adrien Chopin; Brian Schmidt

 Neuroscience Institute, Helen Wills

Adrien Chopin, PhD
Postdoctoral Researcher, Vision Science Program

Title: Bringing completely-stereoblind amblyopes to stereo-recovery
Abstract: Stereoscopic perception is an important component of a normal binocular life. Amblyopic patients often experience a disrupted binocular vision and may benefit from stereopsis recovery. Stereovision is usually tested with clinical stereotests. First, we demonstrate the presence of monocular but also binocular non stereoscopic cues in all parts of the Randot and Butterfly stereotests. Despite the validity of the Randot test, it cannot be used to accurately detect stereoblindness or stereo-impairment. Second, we used psychophysical stereotests to document complete stereoblindness of some of our patients with amblyopia. Then, we applied a recently developed training for stereorecovery of strabismic non-amblyopes (Ding & Levi, 2011: PNAS, 108(37), E733-41) to completely-stereoblind patients with different types of amblyopia. We obtained high stereo-recovery rates but the training was not associated with any acuity improvement. Finally, we document the initial patient traits predicting stereo-recovery from training.

Brian Schmidt, PhD
Postdoctoral Researcher, Vision Science Program

Title: Blue sensations in the absence of S-cones
Abstract: Textbook accounts of color vision maintain that short wavelength sensitive (S) cones are the sole mediators of blue sensations, though it has long been recognized that under certain conditions middle wavelength sensitive (M)-cones participate, as well. We investigated the rules that dictate when M-cones signal blue by targeting individual cones with tiny spots of light, smaller than the diameter of a cone, using adaptive optics together with precise eye-tracking. Subjects reported the color of each spot, which were presented against a short wavelength background that desensitized Scones. A majority of long (L) and M-cones consistently gave rise to the sensation of white, while a smaller group of L- and M-cones repeatedly elicited hue sensations. When blue sensations were reported they were more likely mediated by M- than L-cones. An M cone adjacent to an S-cone was equally likely to signal blue as one far away and, in one subject, proximity to S-cones increased the probability of blue reports. These observations indicate that the visual system does not treat L/Mcones homogeneously: some are apparently reliable informants of hue, while others are less so. Finally, by comparing these results to prior work it is apparent that the activity in neighboring, and sometimes distant, cones can lead to a dramatic change in the hue produced by otherwise identical activation of an individual cone.