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  • 1
    ISSN: 1432-1106
    Keywords: Development ; Electrophysiology ; Visual area 18 ; Kitten ; Normal and dark-rearing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The development of visual cell properties was studied in cortical Area 18 (A18) of normal (NRs) and dark-reared kittens (DRs), from 2 weeks of age to adulthood. In addition to the orientation selective (S) and non-selective (NS) cells, we describe a new type of non-selective cell with a peripheral zone (NSp), which could be either an intermediate form between NS and S cells and included in a sequential model or an immature form of the S cells whose responses are affected by peripheral stimulations. Using accurate coordinates for the area centralis position relative to the optic disc projection as a function of age, we show that: a) the extent of the visual field increases with age in DRs and NRs; b) the retinotopic organization is always present; c) receptive fields, large in the NS cells, reduce to the size of mature S cells as soon as the cells acquire orientation selectivity. This process can occur after only 6 h of visual experience; d) velocity preference shifts toward high velocities, though more so in NRs than in DRs. An interpretation of the development of these properties is proposed, taking into account eye growth, the growth of dendritic fields and the formation of new connections. A comparison with previous results obtained in Area 17 (A17) shows a similar time course of the specification (NRs) and of the despecification (DRs) processes, although the development of A18 is postponed by about 2 weeks. Moreover, the “adult-like” binocular distribution of ocular dominance depends upon visual experience in A18, while it does not in A17.
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  • 2
    ISSN: 1432-1106
    Keywords: Eye muscle receptors ; Ganglionic cells ; Central projection ; Vestibular nuclei ; WGA-HRP ; Double labelling ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The vestibular nuclei of adult cat were injected with retrogradely transported tracers, WGA-HRP or fluorescent Diamidino-Yellow. Labelled cells were found in the caudal half of the ipsilateral mesencephalic trigeminal nucleus, in the area where ganglionic cells of the sensory receptors in the extraocular muscles have previously been described. Double labelling experiments were carried out with Diamidino Yellow injected in vestibular nuclei and Fast Blue in extraocular muscles. Some cells in the mesencephalic trigeminal nucleus were found to contain both tracers, providing evidence that vestibular neurons do receive direct afferent signals from extraocular muscles. Therefore, this anatomical demonstration suggests a direct feed-back control between the extraocular muscle receptors and the vestibular nuclei.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 28 (1977), S. 421-425 
    ISSN: 1432-1106
    Keywords: Visual system ; Cat ; Proprioceptive receptors ; Extraocular muscles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Electrical stimulation of the intraorbital part of the motor branches of extraocular muscles, where proprioceptive fibers run, evokes responses in 25% of the units of the striate cortex of the cat. The latency ranges between 25 and 40 msec. Mechanical stretch of extraocular muscles evokes multiunit responses in the striate cortex. The response is abolished by injection of xylocaine into the stretched muscle. The suppression of the response is reversible.
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  • 4
    ISSN: 1432-1106
    Keywords: Visual cortex ; Development ; Proprioception
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We examined to what extent the proprioceptive signals from extraocular muscles control the vision dependent development of striate cortex functions. In six dark-reared, four-week old kittens we severed the ophthalmic branches of the Vth cranial nerves bilaterally in order to interrupt the proprioceptive afferent input from extraocular muscles. In addition, in order to induce experience-dependent modifications of binocularity we made three of the kittens strabismic by unilateral section of the rectus lateralis muscle and monocularly deprived the three other kittens by lid suture. After these interventions all kittens were raised on a normal day/night schedule. Eight weeks (n = 5) and one year (n = 1) after surgery we examined the receptive field properties of striate cortex neurons with single cell recording. In the strabismic and monocularly deprived kittens 81% and 73%, respectively, of the responsive cells had remained binocular. The ocular dominance distribution in the monocularly deprived kittens was biased only moderately towards the open eye. In both preparations a large fraction of the cells responded sluggishly to optimally aligned light stimuli and had abnormally low orientation selectivity. The few cells (about 20% in both preparations) with normal orientation selectivity responded also vigorously to light. Most of these cells had simple receptive fields and were monocular. The ocular dominance distribution of these mature cells was strongly biased towards the open eye in the monocularly deprived kittens and it was U-shaped in the strabismic kittens. In both preparations the orientation preferences of these mature cells were strongly biased towards vertical and horizontal. We conclude from these results that the abolition of proprioceptive signals from extraocular muscles impedes the experience dependent development of normal cortical receptive fields and prevents the vision dependent reorganization of binocular connectivity such as occurs in strabismic and monocularly deprived kittens. We propose that the control of cortical development by non-retinal, proprioceptive signals is indispensable if the vision dependent modifications of cortical connectivity serve to optimize binocular correspondence.
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  • 5
    ISSN: 1432-1106
    Keywords: Visual cortex ; Area 17 ; Eye blinks ; Cats
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Single units were recorded in area 17 of anesthetized and paralyzed cats. The discharges of cortical units, either spontaneous or driven by two dimensional visual drifting noise, were analyzed during unilateral tactile stimulation (air puffs or taps) of the skin around the eye. This stimulation evokes a blink response in the normal non-curarized animal. The activity in the branch of the facial nerve innervating the orbicularis oculi muscles responsible for the blink was also recorded on the stimulated side. Following the mechanical stimulation, the discharges of both simple and complex visual cells were strongly inhibited with a latency of 70–80 ms. Inhibition was sometimes preceded by a brief increase in firing rate. This typical response was present only when the cutaneous stimulus was effective in triggering a discharge in the motor nerve which drives the orbicularis oculi muscles. Moreover, when a visual response was evoked by a temporary masking of the visual stimulus, this response was suppressed by the association with a tap stimulation.
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  • 6
    ISSN: 1432-1106
    Keywords: Area 17 ; Orientation selectivity ; Neonatal enucleation ; Development
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The developmental properties of 573 neurones have been investigated in the primary visual cortex of eight binocularly intact and twelve unilaterally enucleated kittens. It is shown that removal of one eye at birth alters the development of orientation selectivity observed in the presence or absence of visual experience. In 6-week-old deprived kittens, there remain significantly more orientation selective cells in enucleated than in binocularly deprived kittens. These deprivation-resistant cells respond preferentially to horizontal or vertical orientations and are recorded mainly in the cortex contralateral to the remaining eye. In six-week-old kittens with visual experience, the process of tuning maturation appears to be unaffected by unilateral enucleation at birth. However, a larger over-representation of horizontal and vertical orientation preferences is observed in uniocular kittens than in binocularly intact kittens, suggesting that the development of oblique orientation preference depends upon the presence of binocular afferents in the visual pathway.
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  • 7
    ISSN: 1432-1106
    Keywords: Kitten ; Visual cortex ; Development ; Orientation selectivity ; Eye movement direction ; Extraocular proprioception
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary 1. Previous experiments have demonstrated that eye movements, acting through the extraocular muscle (EOM) proprioceptive afferents, are necessary for the development of orientation selectivity in the cells of the kitten visual cortex. New experiments were carried out to study the effect of the plane of eye movements on the preferred orientation acquired by the visual cortical cells. 2. Darkreared (DR) kittens were operated on at 5–6 weeks of age. In the first series of experiments, 4 out of the 6 EOMs were removed bilaterally in such a way that both eyes could only move in a single plane, either vertical or horizontal. In the second series of experiments, the same operation was performed on one eye which was also sutured shut and, on the other side, the EOM were deafferented by intracranial section of the ophthalmic branch of Vth nerve and the eye left open. 3. 1–4 days after surgery the kittens were given 6 h of visual experience and 12 h later were prepared for visual cell recording in Area 17. 4. In kittens of the first series: orientation selectivity developed in the majority (60–65%) of visual cells, most of which encoded horizontal orientations when the eyes had moved in the vertical plane and vertical orientations when the eyes had moved in the horizontal plane. These results show that the plane of eye movements during early visual experience influences the distribution of preferred orientations with an orthogonal relation. Ocular dominance histograms were “strabismic like”. 5. In kittens of the second series: orientation selectivity developed in 40–50% of cells, about half of which were tuned for the orientation orthogonal to the direction of movement of the occluded eye, as in experiment I. The seeing, deafferented eye, presumably would have sent normal visual inputs centrally, corresponding to displacements on the retina in every direction since the ocular motility of that eye had not been disturbed. However, proprioceptive information about its movements was suppressed. As only some of the EOMs of the occluded eye were still present and connected, the conclusion is that the observed influence of the plane of eye movements acts through the proprioceptive afferents. The ocular dominance histograms showed: 1) a powerful change in favour of the seeing eye after only 6 h of monocular visual experience; 2) a larger effect of monocular visual experience in the hemisphere contralateral to the seeing eye; 3) a linkage between acquisition of orientation selectivity and shift in ocular dominance. 6. Our results suggest that normal development of orientation selectivity in visual cortical cells results from the close association of visual and EOM afferent inputs. It is suggested that these two signals must occur with a precise temporal relationship.
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  • 8
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 272 (1978), S. 816-817 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] In the first series, six DR kittens (six weeks old) were exposed to a normal visual environment for six hours. For four of them (group a) the responses of cells in area 17 were studied electrophysiologically immediately after the period of active visual experience. Three types of visual cell were ...
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  • 9
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Allergy 28 (1973), S. 0 
    ISSN: 1398-9995
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
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  • 10
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    ISSN: 1365-2222
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Skin test materials vary in their potency and specificity. Although 3 mm reactions are often regarded as diagnostic of a type I allergy, a study based on 100 allergy clinic patients with food intolerance showed that thirteen out of fifteen patients with a 3 mm reaction to common inhalant allergens had no RAST-detectable allergen-specific IgE.Three millimetre reactions were significant for milk and egg extracts. Food intolerance was clinically demonstrable in six out of seven patients giving a 4 mm skin reaction and in ten out of thirteen with a 3 mm reaction. There was, however, a ‘clinically false positive’ reaction of 3 mm or more in 3.8% of allergy clinic patients for milk and 2.8% for egg.In fifteen out of nineteen patients with a clinical diagnosis of fish allergy, the diagnosis was supported by a skin test reaction of 5 mm or more. However, seven patients with no history of intolerance to fish gave a 4 mm reaction to the same extract. Reactions of less than 5 mm were thus unhelpful clinically.
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