We present a quantitative phase microscopy scheme that simultaneously acquires two phase images at different wavelengths. The simultaneous dual-wavelength measurement was performed with a diffraction phase microscope (DPM) based on a transmission grating and a spatial filter that form a common-path imaging interferometer. With a combined laser source that generates two-color light continuously, a different diffraction order of the grating was utilized for each wavelength component so that the dual-wavelength interference pattern could be distinguished by the distinct fringe frequencies. Our dual-wavelength phase imaging allowed us to extract information on the physical thickness and the refractive index for a specimen immersed in a highly dispersive surrounding medium. We found that our dual-wavelength DPM (DW-DPM) provides an accurate measurement of the volume and the refractive index of a microscopy sample with good measurement stability that results from the common-path geometry.
19The hippocampus is thought to guide navigation by forming a cognitive map of space. 20However, the behavioral demands for such a map can vary depending on particular 21features of a given environment. For example, an environment rich in cues may require 22 a finer resolution map than an open space. It is unclear how the hippocampal cognitive 23 map adjusts to meet these distinct behavioral demands. To address this issue, we 24 examined the spatial coding characteristics of hippocampal neurons in mice and rats 25 navigating different environments. We found that CA1 place cells located in the 26 superficial sublayer were more active in cue-poor environments, and preferentially used 27 a firing rate code driven by intra-hippocampal inputs. In contrast, place cells located in 28the deep sublayer were more active in cue-rich environments and expressed a phase 29 code driven by entorhinal inputs. Switching between these two spatial coding modes 30was supported by the interaction between excitatory gamma inputs and local inhibition. 31 3
Purpose
Growing evidence suggests that dendrite retraction or degeneration in a subpopulation of the retinal ganglion cells (RGCs) may precede detectable soma abnormalities and RGC death in glaucoma. Visualization of the lamellar structure of the inner plexiform layer (IPL) could advance clinical management and fundamental understanding of glaucoma. We investigated whether visible-light optical coherence tomography (vis-OCT) could detect the difference in the IPL sublayer thicknesses between small cohorts of healthy and glaucomatous subjects.
Method
We imaged nine healthy and five glaucomatous subjects with vis-OCT. Four of the healthy subjects were scanned three times each in two separate visits, and five healthy and five glaucoma subjects were scanned three times during a single visit. IPL sublayers were manually segmented using averaged A-line profiles.
Results
The mean ages of glaucoma and healthy subjects are 59.6 ± 13.4 and 45.4 ± 14.4 years (
P
= 0.02.) The visual field mean deviations (MDs) are −26.4 to −7.7 dB in glaucoma patients and −1.6 to 1.1 dB in healthy subjects (
P
= 0.002). Median coefficients of variation (CVs) of intrasession repeatability for the entire IPL and three sublayers are 3.1%, 5.6%, 6.9%, and 5.6% in healthy subjects and 1.8%, 6.0%, 7.7%, and 6.2% in glaucoma patients, respectively. The mean IPL thicknesses are 36.2 ± 1.5 µm in glaucomatous and 40.1 ± 1.7 µm in healthy eyes (
P
= 0.003).
Conclusions
IPL sublayer analysis revealed that the middle sublayer could be responsible for the majority of IPL thinning in glaucoma. Vis-OCT quantified IPL sublayers with good repeatability in both glaucoma and healthy subjects.
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