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  • 1
    Electronic Resource
    Electronic Resource
    Changes in the circuitry of the kitten visual cortex are gated by postsynaptic activity (1979)
    [s.l.] : Nature Publishing Group
    Nature 280 (1979), S. 58-60 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Three kittens were dark reared until the age of 5 weeks and then, with one eye closed, exposed to a normal environment for 9 consecutive days. Control experiments and a number of previous studies have shown that by this time most cortical cells have become dominated by the open eye and display ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/280058a0
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  • 2
    Electronic Resource
    Electronic Resource
    Unusually large receptive fields in cats with restricted visual experience (1976)
    Springer
    Experimental brain research 26 (1976), S. 171-184 
    Details
    ISSN: 1432-1106
    Keywords: Cat striate cortex ; Spatial interactions ; Selective visual experience ; Plasticity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The receptive fields of striate cortex neurons were analyzed in cats which had restricted or no visual experience. Two groups of animals were investigated: 1. cats which were deprived from contour vision over variable periods of time up to 1 year and 2. kittens whose visual experience was restricted to vertically oriented gratings of constant spatial frequency which moved unidirectionally at a fixed distance in front of the restrained animals. In both preparations exceedingly large receptive fields (up to 20° in diameter) were encountered, especially in cells located in supragranular layers. These large receptive fields never extended over more than 2° into the ipsilateral hemifield. Their sensitivity profile was frequently asymmetric and contained discontinuities. Many of these large receptive fields consisted of several excitatory subregions which were separated from each other by as much as 15°. Often but not always the most sensitive area was located where the retinotopic map predicted the receptive field center. The orientation and direction selectivity and also the angular separation of such multiple excitatory bands often matched precisely the orientation, direction and spatial frequency of the experienced moving grating. In other fields with multiple excitatory subregions such a correspondence could not be established; the various subregions could even have different orientation and direction selectivities. From these unconventional receptive fields it is concluded that the function of cat striate cortex is not confined to a point by point analysis of the visual field in retinotopically organized and functionally isolated columns.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00238281
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  • 3
    Electronic Resource
    Electronic Resource
    Subcortical control of visual thresholds in humans: Evidence for modality specific and retinotopically organized mechanisms of selective attention (1977)
    Springer
    Experimental brain research 29 (1977), S. 173-190 
    Details
    ISSN: 1432-1106
    Keywords: Subcortical vision ; Selective attention
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The present experiments were designed to study the control of visual thresholds in relation to selective attention and goal directed saccadic eye movements in human subjects. The results demonstrate that visual thresholds increase by about 0.5–1 log unit when targets are repeatedly presented in the periphery of the visual field while the subjects are fixating. The diameter of the adapted area and the amplitude of the threshold elevation increase with retinal eccentricity but do not depend on other stimulus parameters such as target size or target luminosity. Irrespective of target size the diameter of the adapted field is in the range of 5 ° close to the fovea and reaches up to 20 ° in the visual field periphery. This elevation of detection thresholds can be reset either by adapting a mirror symmetric area in the contralateral visual field or by directing a saccadic eye movement towards a target which is presented in an area mirror symmetric to the adapted field. When saccades are performed in the absence of the target stimulus or when they are directed towards targets outside the mirror symmetric area no resetting occurs. Adaptation is further prevented when the subject is allowed to saccade towards the adapting target. Measurements in patients with cortical hemianopia indicate, that these phenomena are mediated by subcortical visual centers since they can be influenced by stimulation in the blind hemifield. Participation of subcortical centers, especially of the tectum, is further suggested by the numerous correlations between the present psychophysical observations and the available neurophysiological data on subcortical visual pathways. It is concluded that it is one of the functions of the retino-tectal system to determine detection thresholds in a retinotopically organized way and to guide visual attention towards particular areas within the visual field. The observations in hemianopic patients suggest that these operations are accomplished in parallel to cortical analysis and remain functional after striatal lesions. They are, however, inaccessible to conscious experience.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00237040
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  • 4
    Electronic Resource
    Electronic Resource
    Prominent excitatory pathways in the cat visual cortex (A 17 and A 18): A current source density analysis of electrically evoked potentials (1978)
    Springer
    Experimental brain research 33 (1978), S. 371-394 
    Details
    ISSN: 1432-1106
    Keywords: Visual cortex ; Current source density analysis ; Field potentials ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The current source density (CSD) method in its one-dimensional approximation is used to analyze the field potentials in visual areas 18 and 17 of the cat, which were elicited by stimulating electrodes in the optic chiasm (OX), the optic radiation (OR) or in the respective cortical area itself. The CSD analysis reveals the basic pattern of excitatory postsynaptic activity. 1. In both visual areas the basic specific excitatory activity flows along three different intracortical pathways, all starting in layer IV: The first pathway relays activity from layer IV to supragranular pyramidal cells via strong, local connections to layer III and from there through long-distance connections to layer II. The second pathway conveys activity from layer IV to layer V, where it mainly contacts apical dendrites of layer VI pyramidal cells. This infragranular polysynaptic activity is not clearly resolvable into separate components, suggesting that it is conveyed by various groups of axons, among them long-distance horizontal connections. The third pathway has one synaptic relay within layer IV and then conveys activity to layer III. In addition, monosynaptic activity is revealed in layers VI and I. 2. In A 18 one coherent, fast-conducting group of afferents induces this basic activity pattern. In A 17 no such fast conducting input is resolvable; the supragranular activity is induced by a small group of afferents with intermediate conduction velocity, which terminate in the upper part of layer IV. The infragranular activity is induced by afferents with slower and widely scattered conduction velocities, which terminate in the lower part of layer IV. The layer VI input is very prominent in A 17 and also has a wide latency scatter. 3. The supragranular activity is more prominent in A 18 than in A 17 and the respective layers appear thicker, in accordance with anatomy. In A 17 the infragranular activity prevails and layers IV and VI appear very broad, again in accordance with anatomy. 4. Comparison of the CSDs with the original evoked potentials shows that the surface evoked potentials over A 18 reflect the three dipolar sink/source distributions of the coherent monosynaptic activity in layer IV and of the two prominent polysynaptic activities in layers III and II. The widely scattered activity in the lower part of layer IV in A 17 and all infragranular activities in both areas generate smaller, partly closed-field potentials; those are not discernible from the strong far-field potentials which originate from the supragranular activity and — especially in A 17 —from farther distant events.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00235560
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  • 5
    Electronic Resource
    Electronic Resource
    The role of binocular neurons in the cat striate cortex in combining information from the two eyes (1979)
    Springer
    Experimental brain research 34 (1979), S. 133-142 
    Details
    ISSN: 1432-1106
    Keywords: Binocular vision ; Cat striate cortex
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Cats were raised under conditions of daily alternating monocular exposure, so that each eye received normal input, but the animals were never allowed to use both eyes simultaneously. With single cell recording techniques it could be shown that this led to a severe disturbance of the normal binocularity of cortical neurons. The cats were trained by operant techniques in a two-choice box to discriminate with each eye non-retinotopic stimulus pairs. To test the ability to combine binocular signals it was tested whether the learned discrimination would transfer to red/green colored stimuli which were viewed dichoptically through appropriately colored contact lenses. The arrangement was such that the positive stimulus could be distinguished from the negative stimuli only when the signals from both eyes were combined and used simultaneously. All cats showed immediate transfer, from the monocularly learned discrimination task to the dichoptic paradigm. This indicates that the presence of a normal population of binocular cortical cells in area 17 is not a prerequisite for the ability to use binocular cues for the solution of a pattern discrimination task.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00238346
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  • 6
    Electronic Resource
    Electronic Resource
    Functional amblyopia in kittens with unilateral exotropia (1980)
    Springer
    Experimental brain research 40 (1980), S. 294-304 
    Details
    ISSN: 1432-1106
    Keywords: Squint amblyopia ; Visual cortex ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In two cats in which surgically induced, unilateral divergent strabismus had led to behaviourally determined amblyopia, a variety of electrophysiological parameters were determined in search of neuronal correlates of squint amblyopia. Tests that assess global neuronal excitability along the pathways from the two eyes to the visual cortex (areas 17 and 18) failed to reflect the functional inferiority of the squinting eye: retinographic responses and cortical evoked potentials elicited by Ganzfeld-stimulation and by stimulation of the optic nerves were identical for the two eyes. The ocular dominance distribution of neurons in area 17 showed the expected disruption of binocularity but failed to provide clear evidence for a functional inferiority of the squinting eye. At other levels of analysis, however, a clear difference between the two eyes was apparent: 1. Responses to optimally aligned light stimuli tended to be more sluggish and the under-representation of neurons with vertically oriented receptive fields was more pronounced in neurons driven from the deviated eye than in cells dominated by the normal one. 2. Interocular inhibition as assessed from electrically evoked potentials was found to be asymmetric; responses evoked from the amblyopic eye were suppressed more readily and over longer periods by conditioning shocks applied to the normal nerve than vice versa. 3. Numerous abnormalities reflecting the functional inferiority of the squinting eye became apparent in cortical potentials evoked by phase reversal of gratings of variable spatial frequency and contrast. A laminar analysis of these field potentials suggests impaired transmission along the intracortical pathways which relay activity to supragranular layers as a major cause for abnormal responses from the squinting eye. It is concluded that squint amblyopia is associated with a variety of neuronal changes at various levels of the visual system, the present data providing evidence for alterations at the cortical level.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00237794
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  • 7
    Electronic Resource
    Electronic Resource
    Correlative ultrastructural morphometry of human prolactin-producing adenomas (1980)
    Springer
    Acta neurochirurgica 53 (1980), S. 217-225 
    Details
    ISSN: 0942-0940
    Keywords: Adenoma ; morphometry ; prolactin ; pituitary
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Ultrastructural morphometry was applied to 24 surgically removed human sparsely granulated prolactin cell adenomas in an attempt to correlate the measurements with blood prolactin levels, size of tumour, and age and sex of patient. No correlation was apparent. However, further evaluation revealed that correlation existed between size of tumour and blood prolactin levels, indicating that tumour mass, and not subcellular morphology, was related to the amount of prolactin released.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02074794
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  • 8
    Electronic Resource
    Electronic Resource
    Proprioceptive signals from extraocular muscles gate experience-dependent modifications of receptive fields in the kitten visual cortex (1983)
    Springer
    Experimental brain research 51 (1983), S. 443-450 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00237881
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  • 9
    Electronic Resource
    Electronic Resource
    Ultrastructure and synaptic relations of neural elements containing glutamic acid decarboxylase (GAD) in the perigeniculate nucleus of the cat (1984)
    Springer
    Experimental brain research 56 (1984), S. 115-125 
    Details
    ISSN: 1432-1106
    Keywords: Visual system ; Perigeniculate nucleus ; GAD ; Immunocytochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The perigeniculate nucleus of the cat (PGN) was examined at light and electron microscopic levels after immunocytochemical labeling for the gamma-aminobutyric acid (GABA) synthesizing enzyme, glutamic acid decarboxylase (GAD). In light microscopic sections, virtually all perikarya were found to be labeled (GAD+), as well as proximal dendrites, fibres and punctiform elements. Cells in the thalamic reticular nucleus (TRN) dorsal to PGN were also labeled. Ultrastructural analysis of PGN showed immunoreactivity in all somata, in dendrites and in the following vesicle containing profiles: 1.) F1 terminals, which are characterized by large size, dark mitochondria, and pleomorphic vesicles. These terminals form symmetrical synaptic contacts with somata, somatic spines and with dendrites of GAD+ PGN cells. 2.) F2 terminals, which are smaller than F1 terminals, contain also pleomorphic vesicles and frequently make serial synapses of the symmetric type with other F2 terminals. Presumably, F1 terminals are formed by collaterals of PGN-cell axons and F2 terminals by vesicle containing dendrites of PGN cells. Terminals devoid of immunoreactivity included: 1.) RLD terminals characterized by large size, round vesicles, dark mitochondria, and by asymmetric synaptic contacts with somata, especially with somatic spines, and with dendrites of GAD+ perigeniculate neurons; 2.) RSD terminals, characterized by small size, round vesicles and dark mitochondria, which make asymmetric synapses with GAD+ dendrites of medium and small size; 3.) Multivesicular (MV) terminals with variably shaped vesicles including dense core vesicles synapsing on GAD+ dendrites. There are reasons to believe that RSD terminals belong to corticofugal axons and RLD terminals to collateral axons of LGN relay cells. The origin of MV terminals remains to be determined. The GABAergic nature of the PGN cells conforms with the presumed function of these cells as mediators of inhibition of LGN relay cells. The complex synaptic relations observed between GAD+ elements in the PGN would allow for reciprocal inhibition between perigeniculate cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00237447
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  • 10
    Electronic Resource
    Electronic Resource
    Reticular facilitation of cat visual cortical responses is mediated by nicotinic and muscarinic cholinergic mechanisms (1983)
    Springer
    Experimental brain research 96 (1983), S. 1-7 
    Details
    ISSN: 1432-1106
    Keywords: Acetylcholine ; Receptor antagonists ; Area 17 ; Mesencephalic reticular formation ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Stimulation of the mesencephalic reticular formation facilitates responses in the visual cortex elicited from the optic radiation. Using intraveneous administration of cholinergic antagonists we investigated in adult cats and two kittens whether this effect is mediated by cholinergic mechanisms. When administered alone the muscarinic antagonists atropine and scopolamine and the nicotinic antagonist mecamylamine failed to block reticular facilitation and sometimes even enhanced the effects of reticular stimulation. However, when administered in combination muscarinic and nicotinic antagonists eliminated or significantly reduced the facilitation. This was even true when the two antagonists were administered with a time lag of several hours. These results support the notion that reticular facilitation of cortical responses is mediated by cholinergic mechanisms and suggest that this effect is mediated either by a receptor with a mixed pharmacological property or by two independent pathways acting via nicotinic and muscarinic receptors. This hypothesis is discussed in the context of recent evidence on cholinergic transmission and earlier data on the pharmacology of reticular arousal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00230433
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