Kinematic principles of primate rotational vestibulo-ocular reflex. II. Gravity-dependent modulation of primary eye position

The kinematic constraints of three-dimensional eye positions were investigated in rhesus monkeys during passive head and body rotations relative to gravity. We studied fast and slow phase components of the vestibulo-ocular reflex (VOR) elicited by constant-velocity yaw rotations and sinusoidal oscillations about an earth-horizontal axis. We found that the spatial orientation of both fast and slow phase eye positions could be described locally by a planar surface with torsional variation of <2.0 +/- 0.4 degrees (displacement planes) that systematically rotated and/or shifted relative to Listing's plane. In supine/prone positions, displacement planes pitched forward/backward; in left/right ear-down positions, displacement planes were parallel shifted along the positive/negative torsional axis. Dynamically changing primary eye positions were computed from displacement planes. Torsional and vertical components of primary eye position modulated as a sinusoidal function of head orientation in space. The torsional component was maximal in ear-down positions and approximately zero in supine/prone orientations. The opposite was observed for the vertical component. Modulation of the horizontal component of primary eye position exhibited a more complex dependence. In contrast to the torsional component, which was relatively independent of rotational speed, modulation of the vertical and horizontal components of primary position depended strongly on the speed of head rotation (i.e., on the frequency of oscillation of the gravity vector component): the faster the head rotated relative to gravity, the larger was the modulation. Corresponding results were obtained when a model based on a sinusoidal dependence of instantaneous displacement planes (and primary eye position) on head orientation relative to gravity was fitted to VOR fast phase positions. When VOR fast phase positions were expressed relative to primary eye position estimated from the model fits, they were confined approximately to a single plane with a small torsional standard deviation ( approximately 1.4-2.6 degrees). This reduced torsional variation was in contrast to the large torsional spread (well >10-15 degrees ) of fast phase positions when expressed relative to Listing's plane. We conclude that primary eye position depends dynamically on head orientation relative to space rather than being fixed to the head. It defines a gravity-dependent coordinate system relative to which the torsional variability of eye positions is minimized even when the head is moved passively and vestibulo-ocular reflexes are evoked. In this general sense, Listing's law is preserved with respect to an otolith-controlled reference system that is defined dynamically by gravity.     

Predictive eye movements do not discriminate between dyslexic and control children

Pavlidis has suggested that predictive saccadic tracking eye movements distinguish between reading disabled and normal children. We have examined saccadic eye movement tracking in 34 dyslexic and 33 control subjects, between 10 and 12 yr old. The subjects were equivalent in performance IQ (WISC-R), with differences between verbal and performance IQ of less than 30 points. Children with neurological, visual or auditory deficits or histories of emotional problems and hyperactivity were excluded. There were no differences between the groups on the eye movement tracking task when scored objectively by computerized analysis of the eye movement records, or by ranking of the records by an experienced observer. Our results (and those of other recent studies) fail to support Pavlidis' contention that eye movements hold the key to dyslexia.     

The effect of eye position on auditory lateralization

The present study examines whether the direction of gaze can influence sound lateralization. For this purpose, dichotic stimuli with variable interaural level difference (ILD) were presented under different conditions of visual fixation. In experiment 1, subjects with their head fixed directed their gaze to a given target, simultaneously adjusting the ILD of continuous pure tone or noise stimuli so that their location was perceived in the median plane of the head. The auditory adjustments were significantly correlated with gaze direction. During eccentric fixation, the psychophysical adjustments to the median plane shifted slightly toward the direction of gaze. The magnitude of the shift was about 1-3 dB, over a range of fixation angles of 45 degrees to either side. The eye position effect, measured as a function of pure-tone frequency, was most pronounced at 2 kHz and showed a tendency to decrease at lower and higher frequencies. The effect still occurred, although weaker, even when the eyes were directed to eccentric positions in darkness and without a fixation target. In experiment 2, the adjustment method was replaced by a two-alternative forced-choice method. Subjects judged whether sound bursts, presented with variable ILDs, were perceived on the left or right of the median plane during fixation of targets in various directions. Corresponding to experiment 1, the psychometric functions shifted significantly with gaze direction. However, the shift was only about half as large as that found in experiment 1. The shift of the subjective auditory median plane in the direction of eccentric gaze, observed in both experiments, indicates that dichotic sound is localized slightly to the opposite side, i.e., to the left when the gaze is directed to the right and vice versa. The effect may be related to auditory neurons which exhibit spatially selective receptive fields that shift with eye position.     

Memory for position and identity across eye movements.

Used a "transsaccadic" partial report procedure to measure memory for position and identity information across saccades. Delaying the partial-report cue after the eye movement had little effect on report accuracy. Mask presentation hindered recall only at the shortest delay. Accuracy was much higher when the letter array contained 6 letters than when it contained 10 letters. Intra-array errors were much more frequent than extra-array errors. These results suggest that memory across eye movements decays slowly, has a limited capacity, is maskable for a brief time, and retains identity information better than position information. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Extreme eye position and Hering's law of equal innervation.

Tested E. Hering's (1968 [1977]) claim that extreme horizontal eye position varies as a function of viewing distance. This relationship between version and vergence was measured in 5 university students (aged 19–28 yrs), using both subjective and objective techniques. Results suggest that the extreme eye position difference observed by Hering may have been a function of eye elevation, not distance. With eye elevation held constant, no consistent difference in extreme eye position as a function of distance was observed. Differences in extreme eye position were observed when eye elevation covaried with distance and also when eye elevation varied within one distance. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

光电液伺服式带材纠偏与对中控制

本文介绍冶金部自动化研究院开发研制的带材边缘纠偏控制（ＥＰＣ）系统和对中控制（ＣＰＣ）系统的构成、特点，并作简要分析．文中还介绍了该系统在两个钢铁厂的实际应用情况。     

位置控制器在自动位置控制和物料跟踪中的应用

分析了位置控制器在位置控制中的作用，并对PLC实现坯料跟踪控制，做了详细的介绍。新系统改造后于1998年投入使用，为170无缝钢管公司达到设计产量，起到了不可替代的作用。     

Context-specific adaptation of vertical vergence to correlates of eye position

Vertical phoria (vertical vergence in the absence of binocular feedback) can be trained to vary with non-visual cues such as vertical conjugate eye position, horizontal conjugate eye position and horizontal vergence. These prior studies demonstrated a low-level association or coupling between vertical vergence and several oculomotor cues. As a test of the potential independence of multiple eye-position cues for vertical vergence, context-specific adaptation experiments were conducted in three orthogonal adapting planes (midsagittal, frontoparallel, and transverse). Four vertical disparities in each of these planes were associated with various combinations of two specific components of eye position. Vertical disparities in the plane were associated with horizontal vergence and vertical conjugate eye position; vertical disparities in the frontoparallel plane were associated with horizontal and vertical conjugate eye position; and vertical disparities in the transverse plane were associated with horizontal vergence and horizontal conjugate eye position. The results demonstrate that vertical vergence can be adapted to respond to specific combinations of two different sources of eye-position information. The results are modeled with an association matrix whose inputs are two classes of eye position and whose weighted output is vertical vergence.     

A single position in the third transmembrane domains of the human B1 and B2 bradykinin receptors is adjacent to and discriminates between the C-terminal residues of subtype-selective ligands

In order to identify agonist- and antagonist-binding epitopes in the human B1 and B2 bradykinin (BK) receptors, we exploited the ability of these receptors to discriminate between peptide ligands that differ only by the absence (B1) and presence (B2) of a C-terminal Arg. This was done by constructing chimeric proteins in which specific domains were exchanged between these receptors as recently described by us (Leeb, T., Mathis, S. A., and Leeb-Lundberg, L. M. F. (1997) J. Biol. Chem. 272, 311-317). The constructs were then expressed in HEK293 and A10 cells and assayed by radioligand binding and by agonist-stimulated inositol phospholipid hydrolysis and intracellular Ca2+ mobilization. Substitution of the third transmembrane domain (TM-III) of the B1 receptor in the B2 receptor (B2(B1III)) dramatically reduced the affinities of B2-selective peptide ligands including both the agonist BK and the antagonist NPC17731. High affinity binding of both ligands to B2(B1III) was fully regained when one residue, Lys111, in TM-III of this chimera was replaced with the corresponding wild-type (WT) B2 receptor residue, Ser (B2(B1IIIS111)). Replacement of Ser111 with Lys in the WT B2 receptor decreased the affinities of BK and NPC17731 and increased the affinity of the B1-selective des-Arg10 analog of NPC17731, NPC18565. The results show that the C-terminal residue of peptide agonists and antagonists when bound to the B2 receptor is adjacent to Ser111 in the receptor. A Lys at this position, as is the case in the WT B1 receptor, provides a positive charge that repels the C-terminal Arg in B2-selective peptides and attracts the negative charge of the C terminus of B1-selective peptides, which lack the C-terminal Arg. Therefore, the residues at this one single position are crucial in determining the peptide selectivity of B1 and B2 BK receptors.     

Development of Attentional and Oculomotor Control.

The present study was conducted to examine the development of attentional and oculomotor control. More specifically, the authors were interested in the development of the ability to inhibit an incorrect but prepotent response to a salient distractor. Participants, who ranged in age from 8 to 25 years, performed 3 different eye movement tasks: a prosaccade, an antisaccade, and an oculomotor capture task. The time required to initiate a saccade decreased with age across all 3 tasks. Consistent with previous reports, accuracy was relatively age invariant in the prosaccade task. Performance improved with age, asymptoting at 16 years in the antisaccade task. It is interesting to note that despite the superficial similarity of the antisaccade and oculomotor capture tasks, performance was relatively age invariant in the latter. These results are discussed in terms of developmental differences in the interaction of goal-directed and stimulus-driven processes in the control of attention and action. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Discrepancy between predicted and obtained WAIS–R IQ scores discriminates between traumatic brain injury and insufficient effort.

This study examines how well the discrepancy between predicted and obtained Wechsler Adult Intelligence Scale–Revised (WAIS–R) scores discriminate between insufficient effort (IE) and traumatic brain injury (TBI). The 27 IE patients performed significantly more poorly on the WAIS–R than the 48 moderate-severe TBI patients. Premorbid IQs were calculated with formulae that use demographics (Barona Index) or demographics and WAIS–R performance (Best-3 and the Oklahoma Premorbid Intelligence Estimation). Predictions were similar on the Barona, but IE patients' predicted IQs were lower than TBIs for measures with a performance component. IE patients demonstrated a greater discrepancy score (i.e., predicted IQ—obtained IQ) than TBIs; variable levels of sensitivity and specificity were obtained when discriminate functions were developed on these scores. The potential advantage of using discrepancy scores versus performance-based measures to detect insufficient effort is discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Lexical control of within-word eye movements.

Eye movements were recorded during the reading of long words, which were presented in isolation at their optimal viewing position. Refixations were found to be preferentially directed toward the region of the word that contained the critical letters for distinguishing it from its competitors. In Experiments 1 and 2, low-frequency stimulus words sharing all letters except the initial ones with a high-frequency stimulus word (critical letters at the beginning of the word) elicited more left refixations than low-frequency stimulus words sharing all letters except the final ones with a high-frequency stimulus word (critical letters at the end of the word). A similar result was found in Experiments 3 and 4, using an orthographic priming paradigm. These results suggest that refixations are linked to the selection stage of lexical access, aimed at isolating a single lexical entry among a set of candidates activated during the first fixation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Signals of eye position and velocity in the first-order afferents from pigeon extraocular muscles

Responses of first-order afferents from the extraocular muscles of the pigeon were studied by extracellular recording in the ophthalmic part of the trigeminal ganglion of decerebrate, paralysed pigeons. The afferents responded to both the amplitude and velocity of ramp displacements of the intact eye with amplitude sensitivities ranging from 0.9 to 8 impulses/s/deg of eye displacement beyond the response threshold. Once a new stable position had been reached, the afferent signal depended only upon the absolute position of the eye within the orbit. The responses adapted in seconds rather than minutes so these units would not provide a continuous signal of the position of an immobile eye; they are best described as signalling position and velocity in relation to eye movements.     

Contamination of diagnostic ophthalmic solutions in primary eye care settings

Pharmaceutical agents and irrigating solutions are widely used in both optometric and ophthalmologic practices. Contamination of these containers or solutions could possibly pose some risk of infection to a patient. We set out to investigate the possible contamination of a representative sample of these containers in small office practices. Representative bottles of two diagnostic pharmaceutical agents and an irrigating solution were obtained from primary care optometric and ophthalmologic practices in the San Francisco-Oakland Bay area. These bottles were tested to investigate the rate of contamination and to identify the types of microorganisms in the contaminated solutions. Sixty total samples (proparacaine, tropicamide, and an irrigating solution) were randomly cultured, and 11.7% of the samples showed contamination. Pseudomonas cepacia, Staphylococcus epidermidis, Pseudomonas putida, and Streptococcus species were the predominant organisms isolated from the contaminated bottles. In addition, 17 of the original 60 containers were further cultured for investigation of the dried residue particles around the threads of the containers. Of these 17 containers, 13 (76.5%) tested positive for Staphylococcus and Micrococcus species.     

MNLS inverse discriminates between neuronal activity on opposite walls of a simulated sulcus of the brain

The minimum-norm least-squares inverse for magnetic field measurements is applied to a representation of a sulcus of the human brain, where one or both walls have regions of neuronal activity. Simulations indicate that the magnetic source image (MSI) is largely confined to the appropriate wall of the sulcus, even for a depth of 4 cm where the distance between walls is only 3 mm. Two nearly oppositely oriented dipoles located 3 mm apart are found to be distinguished. Influences on the quality of the MSI by measurement noise and inaccuracy in determining the image surface are discussed in detail.     

A novel glutathione peroxidase in bovine eye. Sequence analysis, mRNA level, and translation

Bovine ciliary body contains a selenium-independent glutathione peroxidase (GPX) with a molecular mass of about 100 kDa that is composed of four identical subunits and exhibits no glutathione S-transferase activity. In this study, we isolated cDNA clones and determined the nucleotide sequence to deduce the primary structure of the enzyme. The cDNA contained 672 base pairs encoding a polypeptide with an estimated molecular mass of 25,064 Da. Translation of bovine ciliary mRNA produced a protein which was immunologically indistinguishable from GPX and showed high enzyme activity. The encoded amino acid sequence of the protein was 95% identical with that of a human keratinocyte gene product expressed in response to keratinocyte growth factor. It also showed sequence identity to bacterial alkyl hydroperoxide reductases and thiol specific antioxidant enzymes. GPX mRNA level was highest in the ciliary body, followed by the retina and iris. In various rat organs, the level of GPX mRNA was highest in the lung, followed by the muscle, liver, eye, heart, testis, thymus, kidney, and spleen. A very low level of mRNA was detected in the brain. Enzyme-linked immunosorbent assay with an antibody raised against the NH2-terminal sequence of GPX detected GPX protein in all rat tissues examined.     

英汉仿拟翻译中的修辞保留策略

由于仿拟修辞符合语言表达的经济性原则,因此在英汉语言中成为常见的修辞现象.要有效地将仿拟修辞表达在译文中呈现,传递给他民族的读者群体,就不得不观照表达与接受主体的社会性因素,包括受英语表音性和汉语表意性特点的影响而在仿拟过程中体现的不同语言使用偏好.仿拟翻译应顺应英汉民族社会性的语言使用偏好,采取优先保留仿拟修辞的策略,以实现源语文本跨语符的修辞交际功能.