Multimodal reference frame for the planning of vertical arms movements

In this study we investigated the reference frames used to plan arm movements. Specifically, we asked whether the body axis, visual cues and graviception can each play a role in defining "up" and "down" in the planning and execution of movements along the vertical axis. Horizontal and vertical pointing movements were tested in two postures (upright and reclined) and two visual conditions (with and without vision) to identify possible effects of each of these cues on kinematics of movement. Movements were recorded using an optical 3D tracking system and analysis was conducted on velocity profiles of the hand. Despite a major effect of gravity, our analysis shows an effect of the movement direction with respect to the body axis when subjects were reclined with eyes closed. These results suggest that our CNS takes into account multimodal information about vertical in order to compute an optimal motor command that anticipates the effects of gravity.     

Target selection for reaching and saccades share a similar behavioral reference frame in the macaque

The selection of one of two visual stimuli as a target for a motor action may depend on external as well as internal variables. We examined whether the preference to select a leftward or rightward target depends on the action that is performed (eye or arm movement) and to what extent the choice is influenced by the target location. Two targets were presented at the same distance to the left and right of a fixation position and the stimulus onset asynchrony (SOA) was adjusted until both targets were selected equally often. This balanced SOA time is then a quantitative measure of selection preference. In two macaque monkeys tested, we found the balanced SOA shifted to the left side for left-arm movements and to the right side for right-arm movements. Target selection strongly depended on the horizontal target location. By varying eye, head, and trunk position, we found this dependency embedded in a head-centered behavioral reference frame for saccade targets and, somewhat counter-intuitively, for reach targets as well. Target selection for reach movements was influenced by the eye position, while saccade target selection was unaffected by the arm position. These findings suggest that the neural processes underlying target selection for a reaching movement are to a large extent independent of the coordinate frame ultimately used to make the limb movement, but are instead closely linked to the coordinate frame used to plan a saccade to that target. This similarity may be indicative of a common spatial framework for hand-eye coordination.     

Force encoding in stick insect legs delineates a reference frame for motor control

The regulation of forces is integral to motor control. However, it is unclear how information from sense organs that detect forces at individual muscles or joints is incorporated into a frame of reference for motor control. Campaniform sensilla are receptors that monitor forces by cuticular strains. We studied how loads and muscle forces are encoded by trochanteral campaniform sensilla in stick insects. Forces were applied to the middle leg to emulate loading and/or muscle contractions. Selective sensory ablations limited activities recorded in the main leg nerve to specific receptor groups. The trochanteral campaniform sensilla consist of four discrete groups. We found that the dorsal groups (Groups 3 and 4) encoded force increases and decreases in the plane of movement of the coxo-trochanteral joint. Group 3 receptors discharged to increases in dorsal loading and decreases in ventral load. Group 4 showed the reverse directional sensitivities. Vigorous, directional responses also occurred to contractions of the trochanteral depressor muscle and to forces applied at the muscle insertion. All sensory discharges encoded the amplitude and rate of loading or muscle force. Stimulation of the receptors produced reflex effects in the depressor motoneurons that could reverse in sign during active movements. These data, in conjunction with findings of previous studies, support a model in which the trochanteral receptors function as an array that can detect forces in all directions relative to the intrinsic plane of leg movement. The array could provide requisite information about forces and simplify the control and adaptation of posture and walking.     

Development of the amphibian oculomotor complex: Evidences for migration of oculomotor motoneurons across the midline

Summary The development of the oculomotor nucleus in five species of salamanders and one anuran species was investigated with tracing techniques. The data presented support the hypothesis that oculomotor motoneurons innervating the superior rectus muscle migrate across the midline. In the salamander Pleurodeles waltl, only ipsilateral oculomotor motoneurons are labeled in early development. Later, these neurons extend dendrites toward the contralateral side into the ventral tegmental neuropil, after which there is displacement of their nuclei (neuronal somata) across the midline. Cell bodies can be observed directly at the midline. In adult Salamandra salamandra, motoneurons innervating the superior rectus muscle are seen occasionally at the midline and on the ipsilateral side, with dendrites toward the contralateral side. Motoneurons on the ipsilateral side do not display these features. In Pleurodeles, developmental brain processes are slowed down, and the sequence of development of the contralateral subnucleus, which can be clearly observed, supports the migration hypothesis. In Xenopus laevis and most other species of salamanders this process is accelerated.     

Print 3-D Fingerprints for Better Biometrics

To test the accuracy of a new fingerprint scanner, researchers typically run millions of known fingerprint images through the system＇s matching software. But this testing procedure can＇t quite mimic real operating conditions, as a 2-D image fed into a program is fundamentally different than a 3-D finger pressed to a sensor.     

Generation and use of measurement-based 3-D dose distributions for 3-D dose calculation verification.

A 3-D radiation therapy treatment planning system calculates dose to an entire volume of points and therefore requires a 3-D distribution of measured dose values for quality assurance and dose calculation verification. To measure such a volumetric distribution with a scanning ion chamber is prohibitively time consuming. A method is presented for the generation of a 3-D grid of dose values based on beam's-eye-view (BEV) film dosimetry. For each field configuration of interest, a set of BEV films at different depths is obtained and digitized, and the optical densities are converted to dose. To reduce inaccuracies associated with film measurement of megavoltage photon depth doses, doses on the different planes are normalized using an ion-chamber measurement of the depth dose. A 3-D grid of dose values is created by interpolation between BEV planes along divergent beam rays. This matrix of measurement-based dose values can then be compared to calculations over the entire volume of interest. This method is demonstrated for three different field configurations. Accuracy of the film-measured dose values is determined by 1-D and 2-D comparisons with ion chamber measurements. Film and ion chamber measurements agree within 2% in the central field regions and within 2.0 mm in the penumbral regions.     

角膜基质细胞的表型转化及其分子机制

角膜瘢痕是继发于多种角膜疾病的病理性改变,是许多角膜疾病造成视力不同程度损害甚至丧失的直接原因,也是影响角膜屈光手术效果的重要因素.对于角膜损伤愈合后的角膜瘢痕,目前临床上主要治疗方法是穿透性或者板层角膜移植术,但因为角膜供体材料缺乏和经济原因,大量的患者无法得到手术治疗而最终丧失视力.     

Population-based hematologic and immunologic reference values for a healthy Ugandan population

To assess the validity of the reference values for hematologic and immunologic indices currently used in Africa, we evaluated blood samples from 3,311 human immunodeficiency virus (HIV)-negative Ugandans aged 1 week to 92 years. Erythrocyte, hemoglobin, and hematocrit levels and mean corpuscular volume all significantly increased with age (P < 0.001) and were independent of gender until the age of 13 years, after which the levels were higher in males than in females (P < 0.001). White blood cell, neutrophil, lymphocyte, basophil, and monocyte counts significantly declined with age until the age of 13 years (P < 0.001), with no differences by gender, while platelet counts declined with age (P < 0.001) and showed differences by gender only among adults older than age 24 years. CD4+- and CD8+-cell counts declined with age until the age of 18 years; thereafter, females had higher counts than males. The absolute values for many of these parameters differed from those reported for populations outside Africa, suggesting that it may be necessary to develop tables of reference values for hematologic and immunologic indices specific for the African population. This may be particularly important with regard to CD4+-cell counts among children because significant differences in absolute and percent CD4+-cell counts exist between the values for Western populations and the values for the population evaluated in our study. These differences could influence the decision to initiate antiretroviral therapy among children infected with HIV.     

Radioautographic study of 3H-GABA uptake in the oculomotor nucleus of the cat

Summary The uptake of tritiated -aminobutyric acid (³H-GABA) in the oculomotor nucleus of the cat was studied, using light and electron microscopic examination of radioautograms after intracerebral in vivo administration of the amino-acid. A glial uptake by oligodendrocytes was seen together with a neuronal uptake of the tracer in a certain type of axon terminals found in synaptic contact with both dendrites and soma, some of them exhibiting all the ultrastructural features of motoneurons. Previous neurochemical, electrophysiological and immunocytochemical studies indicate that GABA might well be the inhibitory neurotransmitter in the vestibuloocular reflex arc. The present results show that a morphological substrate exists for the presumed postsynaptic GABAergic inhibition of ocular motoneurons, at least in the oculomotor nucleus of the cat.Supported by grant ATP 3650 from the Centre National de la Recherche Scientifique     

Neck input modifies the reference frame for coding labyrinthine signals in the cerebellar vermis: a cellular analysis.

The activity of 68 neurons, mainly Purkinje cells, was recorded from the cerebellar anterior vermis of decerebrate cats during wobble of the whole animal (at 0.156 Hz, 5 degrees), a mixture of tilt and rotation, leading to stimulation of labyrinth receptors. Most of the neurons (65/68) were affected by both clockwise and counterclockwise rotations. Twenty-four units showing responses of comparable amplitude to these stimuli (narrowly tuned cells) were represented by a single vector (Smax), whose preferred direction corresponded to the direction of stimulation giving rise to the maximal response. The remaining 41 units, however, showed different amplitude responses to these rotations (broadly tuned cells) and were characterized by two spatially and temporally orthogonal vectors (Smax and Smin), suggesting that labyrinthine signals with different spatial and temporal properties converged on these cells. All these units were tested while the body was aligned with the head (control position), as well as after static displacement of the body under a fixed head by 15 degrees and/or 30 degrees around a vertical axis passing through C1-C2, thus leading to stimulation of neck receptors. The orientation component of the response vector of the Purkinje cells to vestibular stimulation changed following body-to-head displacement. Moreover, the amplitude of vector rotation corresponded, on the average, to that of body rotation. Changes in temporal phase, gain and tuning ratio of the responses were also observed. We propose that information from neck receptors regulates the convergence of labyrinthine signals with different spatial and temporal properties on corticocerebellar units. Due to their strict relationship with the motor system, these units may give rise to appropriate responses in the limb musculature, by modifying the spatial organization of the vestibulospinal reflexes according to the requirements of body stability. The cerebellar vermis may thus represent an important structure, where frames of reference can be altered to account for changes in position of trunk, head and neck.     

Opportunity for natural selection with special reference to population structural measures among the Vadde

Crow's indices of opportunity for natural selection have been studied among the Vadde, a fishing community of Kolleru Lake, Andhra Pradesh, India. The sample comes from 15 of the 60 fishing villages. The indices were computed both at the level of village and population units. A village sample of Palle, another fishing group in the area, has also been analysed for the purpose of comparison. An attempt has been made to explain variation in selection indices among the villages using population structural measures. A wide variation is found in both the fertility and mortality indices between the villages. The values were compatible with those found for other fishing groups studied previously, and in the middle of the range observed for the Indian populations (about 100) studied so far. Population structural measures are found to explain a significant amount of variation in Im and It but not in the fertility index.     

The azimuth projection for the display of 3-D EEG data

Electroencephalogram (EEG) is a scalp record of the neural electric activities of the brain. There are many kinds of methods to display the EEG data, such as a projective plane or the realistic head surface. In this work, one of the atlas projection methods, azimuth conformal projection, was tested and recommended as a new way of a planar EEG display. The method details are given and numerically compared with the normal projective plane display. The results indicate that the azimuth projection has many advantages: the transform is simple, convenient, and it can keep all the information. It shows all the information in the 3-D data within a projective plane without distinct shape change. Therefore, it can help to analyze the data effectively.