Physical work capacity and effect of endurance training in visually handicapped boys and young male adults

Summary The purpose of the present study was to evaluate the relationship between several physical fitness parameters and eyesight divided into 3 grades in visually handicapped boys and young male adults, and to investigate the effect of mild exercise training on physical and psychic symptoms as well as cardiorespiratory fitness. Four subjects were totally blind (TB), 6 were semi-blind (SB) and 27 had amblyopia (AM). Physical fitness tests consisted of maximal oxygen uptake (V _{O 2max}), maximal pedalling speed and power, maximal stepping rate, and isometric knee extention strength. Compared with AM and SB groups, the TB group was inferior in all physical fitness parameters. Especially,V _{O 2max} in TB (26 ml · kg^–1 · min^–1) was about 56% of that in agematched Japanese sighted subjects and was significantly low compared with the AM and SB groups. Both muscle strength and maximal pedalling power corresponded to about 50% that of the age-matched sighted group. Six SB and 4 TB students (¯x=17.7 years) were trained for 6 weeks on a bicycle ergometer at an intensity of 50%V _{O 2max}. Training was undertaken for 3 days per week and maintained for 60 min per session. After training, physical and psychic symptoms determined by the Cornell Medical Index improved significantly. These results indicate that low physical work capacity in visually handicapped boys and young male adults is due to the lack of physical activity, and that mild endurance training is effective in improving physical and psychic symptoms as well as cardiorespiratory fitness.     

Stimulus dependence of ocular dominance of complex cells in area 17 of the feline visual cortex

Summary Stimulus dependence of ocular dominance of 31 deep-layer complex cells was assessed from detailed monocular directional tuning curves for motion of bar stimuli or fields of static visual noise, in area 17 of normal adult cats, lightly anaesthetised with N₂O/O₂ supplemented with pentobarbitone. Virtually all cells were binocularly driven, with the anticipated ocular dominance distribution. Interocular differences in directional bias and sharpness of directional tuning for noise were observed in eleven cells, whereas preferred direction and sharpness of tuning for bar stimuli were similar for each eye. In the majority of cells (20/31), any differences between noise and bar tuning in one eye were replicated in the other. Ocular dominance of about half the cells (17/31) for noise and for bar motion was similar, or marginally shifted by up to one ocular dominance group. Substantial shifts in ocular dominance were seen in 14 cells — by up to two ocular dominance groups in 12 cells and by up to three ocular dominance groups in two cells. In three cases these shifts involved a reversal of eye dominance. Notwithstanding these changes, there were no obvious trends in shifts of ocular dominance in favour of the ipsilateral or contralateral eye, nor was there any tendency towards increased binocularity for noise.     

How sensitive is hand transport to illusory context effects?

A recent report that hand transport was sensitive to a size-contrast illusion (SCI) implied that the distinction between visual processing for perception versus action might only affect visual information obtained late during reaching. In this study, the presence of a perceptual SCI did not affect reaction time, movement time, or movement amplitude. However, both perception and action became sensitive to the SCI with memory-based responses. It is concluded that the distinction between visual processing for perception versus action does extend to hand transport. Immediate action is entirely based on veridical visuo-motor representations, whereas even slightly delayed actions begin to reflect distorted perceptual representations.     

Dendritic spines in the visual cortex of the mouse: Introduction to a mathematical model

Summary The spines of apical dendrites of the layer V pyramidal cells of the area striata in the mouse represent a sequence of post-synaptic structures receiving a variety of contacts from terminal fibers derived fundamentally from short axon cells and superficial pyramidal cells. The study of Golgi preparations of mice 180 days old shows the existence of the most complicated terminal structures over portions of apical dendrites at the levels of layers III and IV. Observations on young mice reveals the terminations of the specific afferent fibers on the dendrites of short axon cells. A mathematical model which defines the distribution of spines along the apical dendrites is introduced. The principal equation of the model has been adjusted from the data processing of microscope countings through a series of programs written for an IBM 7070. The equation defines satisfactorily the different distributions of dendritic spines in mice 10–180 days old raised in normal conditions and in complete darkness. The equation defines also the distribution of dendritic spines in the visual cortex of mice enucleated at birth on one side, and the distribution along the apical dendrites of various cortical areas of the hamster, cat and man. The number of dendritic spines increases with the age of the subject and their distribution varies significantly according to the values of the parameters of the model.     

The influence of visual illusions on grasp position

 Visual size illusions have been shown to affect perceived object size but not the aperture of the hand when reaching to those same objects. Thus, vision for perception is said to be dissociated from vision for action. The present study examines the effect of visual-position and visual-shape illusions on both the visually perceived center of an object and the position of a grasp on that object when a balanced lift is required. The results for both experiments show that although the illusions influence both the perceived and the grasped estimates of the center position, the grasp position is more veridical. This partial dissociation is discussed in terms of its implications for streams of visual processing. Received: 17 November 1997 / Accepted: 11 September 1998     

Role of Der p 1–specific B cells in immune tolerance during 2 years of house dust mite–specific immunotherapy

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Directional asymmetry in smooth ocular tracking in the presence of visual background in young and adult primates

The smooth pursuit system moves the eyes in space accurately while compensating for visual inputs from the moving background and/or vestibular inputs during head movements. To understand the mechanisms underlying such interactions, we examined the influence of a stationary textured visual background on smooth pursuit tracking and compared the results in young and adult humans and monkeys. Six humans (three children, three adults) and six macaque monkeys (five young, one adult) were used. Human eye movements were recorded using infrared oculography and evoked by a sinusoidally moving target presented on a computer monitor. Scleral search coils were used for monkeys while they tracked a target presented on a tangent screen. The target moved in a sinusoidal or trapezoidal fashion with or without whole body rotation in the same plane. Two kinds of backgrounds, homogeneous and stationary textured, were used. Eye velocity gains (eye velocity/target velocity) were calculated in each condition to compare the influence of the textured background. Children showed asymmetric eye movements during vertical pursuit across the textured (but not the homogeneous) background; upward pursuit was severely impaired, and consisted mostly of catch-up saccades. In contrast, adults showed no asymmetry during pursuit across the different backgrounds. Monkeys behaved similarly; only slight effects were observed with the textured background in a mature monkey, whereas upward pursuit was severely impaired in young monkeys. In addition, VOR cancellation was severely impaired during upward eye and head movements, resulting in residual downward VOR in young monkeys. From these results, we conclude that the directional asymmetry observed in young primates may reflect a different neural organization of the vertical, particularly upward, pursuit system in the face of conflicting visual and vestibular inputs that can be associated with pursuit eye movements. Apparently, proper compensation matures later. Electronic Publication     

Changing patterns of binocular visual connections in the intertectal system during development of the frog,Xenopus laevis

Summary In the frog, Xenopus laevis, a system of intertectal connections underlies the visual projection from an eye to its ipsilateral tectal lobe and is involved in the topographic representation of binocular visual space. Rotation of one eye in early life may be followed by a radical rearrangement of the connections in this system. The modified pattern which later emerges is that which keeps the visual projection through the ipsilateral eye in topographic registration with the direct visual projection from the contralateral eye to the same tectal lobe. This plasticity requires visual experience.In this paper we describe the time-course and sequence of events by which this plasticity is effected. Following rotation of one eye in larval animals or in animals undergoing metamorphic climax, the earliest evidence of intertectal modification was found 3–4 weeks after metamorphosis. With increasing intervals after metamorphosis an increasing proportion of animals displayed modified intertectal systems. At intermediate intervals many animals showed partial modifications, which were interpreted as transitional stages in the modification process. Analysis of these transitional stages indicated that the sequence of events involved in the elaboration of a modified intertectal system following the experimental alteration of eye alignment exhibits features in common with rearrangements of the system that occur during normal development in response to growth-related alterations in eye alignment.     

Directional preponderance in human optokinetic nystagmus

Summary In afoveate animals, and in neonatal or cortically deficient foveate animals, monocular optokinetic nystagmus (OKN) is controlled by directly innervated subcortical nuclei and occurs only in response to temporonasal motion. In higher mammals, the subcortical nuclei receive direct inputs predominantly from the nasal hemiretinae and indirect inputs from the visual cortex. These indirect inputs counterbalance the directional asymmetry of the primitive mechanism. These facts lead to the prediction that the velocity of the slow phase of OKN in the normal human adult should be higher for stimuli moving centripetally rather than centrifugally in each monocular and binocular hemified. The predicted patterns of directional preponderance were found in both monocular and binocular hemifields. Directional asymmetries were still present in monocular hemifields when the central retina was occluded and were reduced when the stimulus was confined to a narrow central strip of the visual field. These results are discussed in terms of the contributions of the central and peripheral retina to directional preponderance.This study is part of DCIEM research contract 97711-3-7595/ 8SE83-00221 and was also supported by NSERC grant A0195     

Response properties of neurons in the visual cortex of the rat

Summary Response properties of neurons in the visual cortex, area 17, of Long Evans pigmented rats were investigated quantitatively with computer-controlled stimuli. Ninety percent of the cells recorded (296/327) were responsive to visual stimulation. The majority (95%, 281/296) responded to moving images and were classified as complex (44%), simple (27%), hypercomplex (13%) and non-oriented (16%) according to criteria previously established for cortical cells in the cat and monkey. The remaining 5% of the neurons responded only to stationary stimuli flashed on-off in their receptive field. Results of this study indicate that neurons of the rat visual cortex have properties similar to those of cells in the striate cortex of more visual mammals.Supported by grant EY02964, the Biological Humanics Foundation and the Bendix Corporation