There is considerable support for the hypothesis that perception of heading in the presence of rotation is mediated by instantaneous optic flow. This hypothesis, however, has never been tested. We introduce a method, termed "nonvarying phase motion," for generating a stimulus that conveys a single instantaneous optic flow field, even though the stimulus is presented for an extended period of time. In this experiment, observers viewed stimulus videos and performed a forced-choice heading discrimination task. For nonvarying phase motion, observers made large errors in heading judgments. This suggests that instantaneous optic flow is insufficient for heading perception in the presence of rotation. These errors were mostly eliminated when the velocity of phase motion was varied over time to convey the evolving sequence of optic flow fields corresponding to a particular heading. This demonstrates that heading perception in the presence of rotation relies on the time-varying evolution of optic flow. We hypothesize that the visual system accurately computes heading, despite rotation, based on optic acceleration, the temporal derivative of optic flow.
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http://dx.doi.org/10.1073/pnas.2022984117 | DOI Listing |
Cornea
January 2025
Department of Ophthalmology, Massachusetts Eye and Ear, Harvard Medical School, Boston, MA.
Purpose: To report on optical coherence tomography angiography (OCTA) in patients with a type 1 Boston keratoprosthesis (KPro) and determine its feasibility through assessment of imaging artifacts.
Methods: KPro and non-KPro subjects were matched for age, gender, and glaucoma diagnosis. OCTA images of the peripapillary optic nerve were obtained, reviewed by 2 readers masked to the diagnosis for artifacts and usability, and used for microvascular measurements.
J Exp Biol
January 2025
Independent researcher, 74 Eccleston Square, London, UK.
The function of zebra stripes has long puzzled biologists: contrasted and conspicuous colours are unusual in mammals. The puzzle appears solved: two lines of evidence indicate that they evolved as a protection against biting flies, the geographical coincidence of stripes and exposure to trypanosomiasis in Africa and field experiments showing flies struggling to navigate near zebras. A logical mechanistic explanation would be that stripes interfere with flies' analysis of the optic flow; however, both spatio-temporal aliasing and the aperture effect seem ruled out following recent experiments showing that randomly checked patterns also interfere with flies' capacity to navigate near zebras.
View Article and Find Full Text PDFPhotodiagnosis Photodyn Ther
January 2025
Istanbul Medeniyet University, Faculty of Medicine, Department of Ophthalmology, Istanbul, Turkey. Electronic address:
Objective: Imaging techniques have demonstrated changes in the choroid and retina in acute central serous chorioretinopathy (CSCR), but the effects on the optic nerve head (ONH) remain unclear. This study investigates ONH structural changes in acute CSCR using enhanced deep imaging optic coherence tomography (EDI-OCT).
Methods: A prospective cohort study included 51 acute CSCR patients and 51 healthy controls aged 18-65 years.
Cell Rep
January 2025
Department of Clinical and Molecular Medicine, Norwegian University of Science and Technology, Erling Skjalgssons Gate 1, 7491 Trondheim, Norway; Kavli Institute for Systems Neuroscience and Centre for Algorithms in the Cortex, Norwegian University of Science and Technology, Olav Kyrres Gate 9, 7030 Trondheim, Norway. Electronic address:
The brain uses a specialized system to transport cerebrospinal fluid (CSF), consisting of interconnected ventricles lined by motile ciliated ependymal cells. These cells act jointly with CSF secretion and cardiac pressure gradients to regulate CSF dynamics. To date, the link between cilia-mediated CSF flow and brain function is poorly understood.
View Article and Find Full Text PDFUrolithiasis
January 2025
Department of Urology, University of Michigan, 1500 E. Medical Center Drive, Ann Arbor, MI, 48109-5330, USA.
Understanding renal pelvis pressure (P) during ureteroscopy (URS) has become increasingly important. High irrigation rates, desirable to maintain visualization and limit thermal dose, can increase P. Use of a multi-channel ureteroscope (m-ureteroscope) with a dedicated drainage channel is one strategy that may facilitate simultaneous low P and high flowrate.
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