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  • 1
    Digitale Medien
    Digitale Medien
    Monocular deprivation and the signal transmission by X- and Y-neurons of the cat lateral geniculate nucleus (1979)
    Springer
    Experimental brain research 34 (1979), S. 521-539 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Pattern deprivation ; Afferent visual system ; Flicker responses ; Optic nerve stimulation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary 1. In adult cats deprived monocularly from the second week of life, single neurons were recorded from the optic tract (OT), the lateral geniculate body (pars dorsalis, LGN) and the optic radiation (OR). The neurons were classified according to their visual response properties (Y/X) or their latencies to OT electrical stimulation (class I/II). 2. A close positive correlation (〉 95%) was found between the visual classification and the latency classification (Y = I, X = II). 3. The relative frequency of class I/Y-neurons was reduced in the group of pattern-deprived LGN neurons, but normal in the pattern-deprived OR neurons. 4. The ratio of the r1 and r2 wave amplitude of the OR-evoked potentials elicited by electrical stimulation of the normal or the deprived eye optic nerve was not affected by pattern deprivation. 5. The activity pattern of neurons recorded from the LGN or the OR did not differ in normal and pattern-deprived neurons belonging to the same class (on-center/off-center; Y/X). The same was true for the neuronal responses to electrical stimulation of the OT at different stimulus frequencies (1–200 stimuli/s). 6. The average maintained activity of pattern-deprived OT or OR neurons recorded while the eyelids of the deprived eye were still closed was either equal to or even somewhat higher than the average activity of the corresponding normal neurons. This was true when the patterned stimuli were presented stationary or were moved at random within the visual field simulating the effect of eye and head movements. The pattern deprivation effects found morphologically and physiologically in the visual cortex are, therefore, not induced by a diminished average activity of the input neurons from the deprived eye.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00239147
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  • 2
    Digitale Medien
    Digitale Medien
    Relative frequency and visual resolution of X- and Y-cells in the LGN of normal and monocularly deprived cats: Interlaminar differences (1979)
    Springer
    Experimental brain research 34 (1979), S. 591-603 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Cat LGN ; Monocular Deprivation ; Visual Acuity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The visual acuity (spatial resolving power) and the relative incidence of X- and Y-cells in laminae A and A1 of the dorsal lateral geniculate nucleus (LGN) with receptive fields within 10 ° visual angle to the area centralis have been determined in normal and monocularly deprived cats, using a square-wave grating with logarithmically varying spatial frequencies (0.05–8 c/deg). In the normal cat's LGN the incidence of Y-cells is 1.6 times higher in A1 (48% of the relay-cells) than in A (29%). The mean spatial resolution of all cells is 1.3 times higher in A (2.5 ± 1.2 c/deg) than in A1 (1.8 ± 1.0 c/deg). Mean acuity of Y-cells is equal in both laminae (1.1 ± 0.5 c/deg), but for X-cells it is higher in lamina A (2.9 ± 1.0 c/deg in A, vs. 2.5 ± 0.7 c/deg in A1). After early monocular deprivation, visual acuity is reduced in the deprived lamina A1 (X-cells: 1.7 ± 0.9 c/deg in A1 vs. 2.6 ± 0.7 c/deg in A; Y-cells: 0.9 ± 0.4 c/deg in A1 vs. 1.3 ± 0.4 c/deg in A). This confirms the results of Maffei and Fiorentini (1976). However, visual acuity of X-cells is still higher in the deprived lamina A (3.1 ± 1.0 c/deg) than in the non-deprived lamina A1 (2.7 ± 0.7 c/deg). For Y-cells, visual acuity is equal in both laminae (1.3 ± 0.5 c/deg). Thus the loss of visual acuity is only significant in lamina A1. This loss was equally strong in the area centralis and up to 10 ° eccentricity. Ipsilateral to the early deprived eye only 37% of all recorded Y-cells were located in the deprived lamina A1 (this is 1.7 times less than in the normal A1). Contralateral to the deprived eye 29% of the Y-cells were recorded in the deprived lamina A (1.3 times less than in the normal A). In conclusion, both the impairment of mean visual acuity and the reduction in the recording probability of Y-cells were more pronounced in lamina A1 (receiving uncrossed inputs from the deprived eye) than in lamina A (crossed inputs).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00239151
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  • 3
    Digitale Medien
    Digitale Medien
    A comparison of visual responses in two pretectal nuclei and in the superior colliculus of the cat (1979)
    Springer
    Experimental brain research 35 (1979), S. 495-510 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Pretectal nuclei ; Superior colliculus ; Visual response pattern ; Retinal input types ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Single unit recordings from 220 units were obtained from the nuclei praetectalis anterior (NPA) and posterior (NPP) of 30 immobilized, anesthetized cats. Quantitative analysis of pretectal (PT) visual activity was mainly based on recordings from the NPP. For comparison, 160 collicular (CS) neurons were studied. A strong sensitivity for moving objects was evident in both samples. The following main types of PT activity were categorized: (A) slow movement, direction-selective units (21%); (B) slow movement, nondirection-selective units (19%); (C) units nonselective for stimulus velocity and direction (24%); (D) jerk movement selective, nondirection-selective units (36%). Latency measurements following single shocks to optic chiasm (OX) and tract (OT) showed mainly slow conducting fiber input to the PT and CS which can be divided into two different groups by conduction properties and synaptic delay: direct W-input and delayed W-input. Fast Y-fiber input of both types, direct and indirect, was recorded at both sites, PT and CS.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00236767
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  • 4
    Digitale Medien
    Digitale Medien
    Analysis of neuronal networks in the visual system of the cat using statistical signals (1976)
    Springer
    Biological cybernetics 22 (1976), S. 7-20 
    Details
    ISSN: 1432-0770
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Informatik , Physik
    Notizen: Abstract If the input signals of the visual system in the cat are statistical patterns in space and time, a complete system analysis can be carried out. What counts here as a system are the neuronal networks between retina and recording site. In the case of linearity, one obtains the temporal impulse response functions at every point in the receptive field with the aid of correlation methods. The measuring time is about one minute. Some aspects of the procedure are explained in terms of examples. The method of measurement also makes it possible to determine the characteristic function of the system in time and space between different recording sites within the cortex. It is possible to specialize the procedure for analysing the stationary space dependent behaviour of neuronal networks. The extension of the analysis procedure allows a concise, relatively simple description for nonlinear systems in which linear and nonlinear subsystems can be separated. Besides this, there are no restrictions concerning the kind of nonlinearity. A second paper will present the detailed experimental application of these methods.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00340228
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  • 5
    Digitale Medien
    Digitale Medien
    Analysis of neuronal networks in the visual system of the cat using statistical signals — Simple and complex cells (1978)
    Springer
    Biological cybernetics 31 (1978), S. 175-185 
    Details
    ISSN: 1432-0770
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Informatik , Physik
    Notizen: Abstract Superimposing additively a two-dimensional noise process to deterministic input signals (bars) the neurons of area 17 show a class-specific reaction for the task of signal extraction. Moving both parts of the signals simultaneously and varying the signal to noise ratio (S/N) the simple cells achieve the same performance as resulted from the psychophysical experiment. Type I complex cells extract moving deterministic signals (i.e. bars) from the stationary noise, whereas in the answers of Type II complex cells the statistical parts of the signals predominate. Considering the different cell types each as a series of a linear and a nonlinear system one obtains the cell specific space-time frequency and the amplitude characteristics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00337004
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