缺盆穴的解剖结构和针刺深度

方法：随机抽样取57具较新鲜的成年人尸体,其中男尸24具,女尸33具,要用解剖断面法和解剖层次法,研究缺盆穴的解剖结构和针刺深度。结果：向下直刺的解剖结构依此是皮肤、浅筋膜、劲筋膜浅层,肩胛舌骨肌下腹、臂丛、肋间外肌、是内肌;向下直刺的平均危险深度是38．34mm。结论：为了安全,建议向下直刺的深度控制在26．83mm之间。     

FT-IR photoacoustic depth profiling spectroscopy of enamel

Photoacoustic Fourier transform infrared (PA-FT-IR) depth profiling spectra of the enamel of an intact human tooth are obtained in a completely nondestructive fashion. The compositional and structural changes in the tissue are probed from the enamel surface to a depth of about 200 m. These changes reflect the state of tissue development. The subsurface carbonate gradient in the enamel could be observed over the range of about 10–100 m. The carbonate-to-phosphate ratio increases in the depth profile. The depth profile also reveals changes in the substitutional distribution of carbonate ions. Type A carbonates (hydroxyl substituted) increase relative to type B carbonates (phosphate substituted) with increasing thermal diffusion length. In addition to the changes in the carbonate ion distribution and content, the PA-FT-IR depth profile clearly indicates a dramatic increase in the protein content relative to the phosphate content with increased depth. The changes in the carbonate content and distribution, along with the changes in the protein content, may be responsible for the changes observed in the apatitic structure in the depth profile of the enamel.     

Dorsal stream development in motion and structure-from-motion perception

Little is known about the neural development underlying high order visual perception. For example, in detection of structures by coherently moving dots, motion information must interact with shape-based information to enable object recognition. Tasks involving these different motion-based discriminations are known to activate distinct specialized brain areas in adults. Here, we investigate neural development of normally developing children using functional magnetic resonance imaging (fMRI) during perception of randomly moving point-light dots (RM), coherently moving dots that formed a 3D rotating object (SFM) and static dots. Perception of RM enhanced neural activity as compared with static dots in motion processing-related visual areas, including visual area 3a (V3a), and middle temporal area (hMT+) in 10 adults (age 20-30 years). Children (age 5-6 years) showed less pronounced activity in area V3a than adults. Perception of SFM induced enhanced neural activity as compared to RM in adults in the left parietal shape area (PSA), whereas children increased neural activity within dorsal (V3a) and ventral brain areas (lingual gyrus) of the occipital cortex. These findings provide evidence of neural development within the dorsal pathway. First, maturation was associated with enhanced activity in specialized areas within the dorsal pathway during RM perception (V3a) and SFM perception (PSA). Secondly, high order visual perception-related neural development was associated with a shift in neural activity from low level shape and motion specialized areas in children, including partially immature area V3a, to high order areas in the parietal lobule (PSA) in adults.     

Optical aberrations in the mouse eye

PURPOSE: The mouse eye is a widely used model for retinal disease and has potential to become a model for myopia. Studies of retinal disease will benefit from imaging the fundus in vivo. Experimental models of myopia often rely on manipulation of the visual experience. In both cases, knowledge of the optical quality of the eye, and in particular, the retinal image quality degradation imposed by the ocular aberrations is essential. In this study, we measured the ocular aberrations in the wild type mouse. METHODS: Twelve eyes from six four-week old black C57BL/6 wild type mice were studied. Measurements were done on awake animals, one being also measured under anesthesia for comparative purposes. Ocular aberrations were measured using a custom-built Hartmann-Shack system (using 680-nm illumination). Wave aberrations are reported up to fourth order Zernike polynomials. Spherical equivalent and astigmatism were obtained from the 2nd order Zernike terms. Modulation Transfer Functions (MTF) were estimated for the best focus, and through-focus, to estimate depth-of-focus. All reported data were for 1.5-mm pupils. RESULTS: Hartmann-Shack refractions were consistently hyperopic (10.12+/-1.41 D, mean and standard deviation) and astigmatism was present in many of the eyes (3.64+/-3.70 D, on average). Spherical aberration was positive in all eyes (0.15+/-0.07 microm) and coma terms RMS were significantly high compared to other Zernike terms (0.10+/-0.03 microm). MTFs estimated from wave aberrations show a modulation of 0.4 at 2c/deg, for best focus (and 0.15 without cancelling the measured defocus). For that spatial frequency, depth-of-focus estimated from through-focus modulation data using the Rayleigh criterion was 6D. Aberrations in the eye of one anesthetized mouse were higher than in the same eye of the awake animal. CONCLUSIONS: Hyperopic refractions in the mouse eye are consistent with previous retinoscopic data. The optics of the mouse eye is far from being diffraction-limited at 1.5-mm pupil, with significant amounts of spherical aberration and coma. However, estimates of MTFs from wave aberrations are higher than previously reported using a double-pass technique, resulting in smaller depth-of-field predictions. Despite the large degradation imposed by the aberrations these are lower than the amount of aberrations typically corrected by available correction techniques (i.e., adaptive optics). On the other hand, aberrations do not seem to be the limiting factor in the mouse spatial resolution. While the mouse optics are much more degraded than in other experimental models of myopia, its tolerance to large amounts of defocus does not seem to be determined entirely by the ocular aberrations.     

Stereoscopic depth discrimination with contrast windowed stimuli

Depth discrimination with a shifted contrast window was compared to that with a fixed contrast window. Stereoscopic performance with the fixed window was limited to small disparities and varied with spatial frequency. Performance with the shifted window extended to larger disparities and was more similar for low and high spatial frequencies. The results depended upon window shape, indicating that edge blur is an important factor. Stereoscopic performance with shifted patterns was supported at disparities larger than a phase disparity model might predict, suggesting that a combination of position and phase disparity computations are used for the perception of stereoscopic depth.     

Evidence for elongated receptive field structure for mechanisms subserving stereopsis

To study the spatial extent and shape of the binocular disparity mechanisms subserving depth perception, we employ the spatial summation paradigm of contrast threshold for front/back depth discrimination at a fixed binocular disparity. The stimuli were Gabor patches with disparity set at either 4 or 8 arcmin and spatial frequency set at an optimal value of 4 cy/deg. Contrast threshold was measured as a function of length and width of the Gabor patches to determine the aspect ratio of greatest efficiency. The space constant of the Gaussian envelope varied between 0.0375 degrees and 0.9 degrees in either vertical or horizontal directions, or both simultaneously. For vertical elongation of the Gabor patches, discrimination sensitivity improved by 4-6 dB for a doubling of the length of the Gabor patches, then reduced more slowly as the length further increased. However, extending the Gabor patches horizontally across cycles produced little or no sensitivity improvement. Instead, discrimination performance collapsed in a fashion that is incompatible with many models of disparity processing. The results imply that the main mechanisms subserving stereoscopic depth discrimination are vertically elongated for vertical-bar Gabors and encounter special difficulties integrating horizontal disparity information. Disparity discrimination sensitivity for very small targets was also much greater than predicted by the single-mechanism fit, implying the presence of a second, independent mechanism with a very small summation field, which may underlie the fine stereoscopic processing system.     

The visual perception of plane tilt from motion in small field and large field: psychophysics and theory

Subjects indicated the tilt of dotted planes rotating in depth, in monocular viewing, under perspective projection. The responses depended on the FOV (field of view) and on the angle W between the tilt and frontal translation (orthogonal to the rotation axis). Response accuracy increased with the FOV, and decreased with W. Our results support the processing of the second-order optic flow in all cases, but indicate that this flow is quantitatively small in small-field, leading to tilt ambiguities. We examine computational models based on the affine components of the optic flow to interpret our results.     

Neural correlates of monocular and binocular depth cues based on natural images: a LORETA analysis

Functional imaging studies investigating perception of depth rely solely on one type of depth cue based on non-natural stimulus material. To overcome these limitations and to provide a more realistic and complete set of depth cues natural stereoscopic images were used in this study. Using slow cortical potentials and source localization we aimed to identify the neural correlates of monocular and binocular depth cues. This study confirms and extends functional imaging studies, showing that natural images provide a good, reliable, and more realistic alternative to artificial stimuli, and demonstrates the possibility to separate the processing of different depth cues.     

Quantitative perceived depth from sequential monocular decamouflage

We present a novel binocular stimulus without conventional disparity cues whose presence and depth are revealed by sequential monocular stimulation (delay > or = 80 ms). Vertical white lines were occluded as they passed behind an otherwise camouflaged black rectangular target. The location (and instant) of the occlusion event, decamouflaging the target's edges, differed in the two eyes. Probe settings to match the depth of the black rectangular target showed a monotonic increase with simulated depth. Control tests discounted the possibility of subjects integrating retinal disparities over an extended temporal window or using temporal disparity. Sequential monocular decamouflage was found to be as precise and accurate as conventional simultaneous stereopsis with equivalent depths and exposure durations.     

3D shape discrimination using relative disparity derivatives

Three-dimensional (3D) shape discrimination could be achieved using relative disparity signals or it could be achieved using a higher-order disparity derivative detector. Two 3D shape discrimination tasks were used to distinguish between these possibilities: a within-shape task and a between-shape task. Disparity thresholds were larger when discriminating within the same shape than when discriminating between shapes. More importantly, within-shape discriminations were dependent on the pedestal disparity (distance from fixation) whereas between-shape discriminations were not. The results suggest that a mechanism sensitive to higher-order disparity derivatives can achieve discrimination between different 3D shapes.