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  • 1
    Electronic Resource
    Electronic Resource
    Role of primary visual cortex in the binocular integration of plaid motion perception (2005)
    Oxford, UK : Blackwell Science Ltd
    European journal of neuroscience 21 (2005), S. 0 
    Details
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: This study assessed the early mechanisms underlying perception of plaid motion. Thus, two superimposed gratings drifting in a rightward direction composed plaid stimuli whose global motion direction was perceived as the vector sum of the two components. The first experiment was aimed at comparing the perception of plaid motion when both components were presented to both eyes (dioptic) or separately to each eye (dichoptic). When components of the patterns had identical spatial frequencies, coherent motion was correctly perceived under dioptic and dichoptic viewing condition. However, the perceived direction deviated from the predicted direction when spatial frequency differences were introduced between components in both conditions. The results suggest that motion integration follows similar rules for dioptic and dichoptic plaids even though performance under dichoptic viewing did not reach dioptic levels. In the second experiment, the role of early cortical areas in the processing of both plaids was examined. As convergence of monocular inputs is needed for dichoptic perception, we tested the hypothesis that primary visual cortex (V1) is required for dichoptic plaid processing by delivering repetitive transcranial magnetic stimulation to this area. Ten minutes of magnetic stimulation disrupted subsequent dichoptic perception for approximately 15 min, whereas no significant changes were observed for dioptic plaid perception. Taken together, these findings suggest that V1 is not crucial for the processing of dioptic plaids but it is necessary for the binocular integration underlying dichoptic plaid motion perception.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-9568.2005.03914.x
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  • 2
    Electronic Resource
    Electronic Resource
    Cellular response to texture and form defined by motion in area 19 of the cat (2000)
    Oxford, UK : Blackwell Science Ltd
    European journal of neuroscience 12 (2000), S. 0 
    Details
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The present study examined the neuronal sensitivity in area 19 of the cat to a motion-defined bar and to texture. Sensitivity was tested in normal, lesioned (areas 17–18) and split-chiasm cats using a kinematogram, as well as a textured bar drifting on a uniform light background and a light bar drifting on a stationary textured background. Texture density was varied. The results indicate that almost all cells of area 19 recorded in the three groups of cats responded to a motion-defined bar or to its edges. Texture density influenced the responses in that the discharge rate increased as density decreased. However, the majority of cells were sensitive to the highest texture density kinematogram. Moreover, the neural responses of all cats were either independent of the density of the textured bar or background, or were modulated by it. These results show that cells in area 19 can signal the presence of a kinetic bar and that the density of either the textured bar, the background or both can influence figure–ground detection. The results are interpreted with respect to how various inputs influence the function of area 19.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-9568.2000.00046.x
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  • 3
    Electronic Resource
    Electronic Resource
    Spatial Resolution and Contrast Sensitivity of Single Neurons in Area 19 of Split-chiasm Cats: A Comparison With Primary Visual Cortex (1997)
    Oxford, UK : Blackwell Publishing Ltd
    European journal of neuroscience 9 (1997), S. 0 
    Details
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Electrophysiological recordings were carried out in the callosal recipient zone of area 19 in normal and split-chiasm cats and, for comparison purposes, at the border of areas 17 and 18 of split-chiasm cats. The influences of retinothalamic and callosal inputs on a single cortical neurons were thereby evaluated. Extracellular recordings of single cells were made in anaesthetized and paralysed cats in the zone representing the central visual field. Receptive field properties were assessed using sine wave gratings drifting in optimal directions. Results showed that in area 19 and areas 17/18 one-third of the cells were binocularly driven after section of the optic chiasm. In area 19, the spatial resolution and contrast sensitivity of cells driven via the dominant eye were similar in the normal and split-chiasm groups. In areas 17/18 and area 19 of split-chiasm cats, binocular cells showed significant interocular matching of their receptive field properties (spatial resolution and contrast threshold), although small differences were observed. These small interocular differences were related to the cell's Ocular dominance rather than to the signal transmission route (thalamic or callosal).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-9568.1997.tb00760.x
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  • 4
    Electronic Resource
    Electronic Resource
    Inter-hemispheric competition during postnatal development (1981)
    [s.l.] : Nature Publishing Group
    Nature 290 (1981), S. 139-140 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The preparation used is shown in Fig. 1a. Four kittens were reared normally from birth until 21 days of age, when they were subjected to surgical section of the optic chiasm and at the same time the left eyelid was sutured shut5,6. The kittens then received visual exposure in a normally lit ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/290139a0
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  • 5
    Electronic Resource
    Electronic Resource
    Binocular interaction and disparity coding at the 17–18 border: contribution of the corpus callosum (1992)
    Springer
    Experimental brain research 90 (1992), S. 129-140 
    Details
    ISSN: 1432-1106
    Keywords: Disparity coding ; Binocular interaction ; Corpus callosum ; Split-chiasm ; Areas 17–18 ; Cats
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Binocular disparity, resulting from the projection of a three-dimensional object on the two spatially separated retinae, constitutes one of the fundamental cues for stereoscopic perception. The binocularity of cells in one hemisphere stems from two sources: i) from the ipsilateral ganglion cells in the temporal retina which converge with inputs coming from the contralateral nasal retina; the latter axons cross at the chiasma; ii) from inputs originating in the opposite hemisphere which cross in the corpus callosum. The objective of this study was to demonstrate that interactions from both types of inputs can result in the formation of disparity sensitive neurons and presumably that either type could mediate stereoperception based on disparity cues. Two types of disparity sensitive neurons were found in the normal cat: one type, showing maximal interactive effects around zero disparity responded with strong excitation or inhibition when the stimuli were in register. These neurons are presumed to signal stimuli situated about the fixation plane. The other type, also made up of two subtypes of opposed valencies, gave maximum responses at one set of disparities and inhibitory responses to the other set. These were presumed to signal stimuli situated in front of or behind the fixation plane. In the split-chiasm cat, whose cortical binocularity is presumably assured by converging ipsilateral and callosal inputs, three of the four subtypes of disparity sensitive neurons were found, the uncrossed disparity cells being absent in these animals. Moreover, stimulating each eye individually indicated that nearly 80% of the cells in normal and about 40% in split-chiasm cats were binocularly driven. However, both these figures underestimated the amount of binocular interaction in the callosal recipient zone, since stimulating both eyes simultaneously showed that a proportionately larger number of cells were binocularly driven. Disparity sensitive cells also varied as a function of ocular dominance, i.e., cells signaling the fixation plane tended to have balanced dominance whereas units preferring stimuli situated in front of or behind the fixation plane were dominated by the ipsilateral and contralateral eyes, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00229264
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  • 6
    Electronic Resource
    Electronic Resource
    Loss of stereopsis following lesions of cortical areas 17–18 in the cat (1992)
    Springer
    Experimental brain research 89 (1992), S. 521-530 
    Details
    ISSN: 1432-1106
    Keywords: Pattern discrimination ; Stereopsis ; Juleszstereograms ; Vernier acuity ; Areas 17–18 ; Lesions ; Cats
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The effects of bilateral removal of cortical areas 17–18 were investigated in the cat; these areas represent the central portion of the visual field and the effect of their removal was evaluated with reference to the perception of Julesz random-dot stereograms. Animals were trained in a two-choice discrimination box to choose between two stereotargets made out of random dots. When appropriately viewed, one produced a vertical rectangle and the other an horizontal one, which appeared to float out in space (crossed stereopsis). The results indicated that all normal cats could solve the random-dot task. Following the cortical lesions, stereoscopic perception was abolished. We also tested for the possibility that this inability to solve the random-dot problem was due to a more general acuity loss. Verniertype acuity comparing a continuous to a disjointed line showed this to be within the animals' discriminative ability. Offset acuity of the lines was better than that of the stereodot patterns. On the other hand, the ability to determine the preoperatively acquired brightness and pattern discriminations was preserved, although some retraining was necessary for the more difficult patterns. It is therefore suggested that the primary visual cortex, at least in the cat, is involved in the perception of global stereopsis independently of its implication in the discrimination of bidimensional patterns.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00229877
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  • 7
    Electronic Resource
    Electronic Resource
    Binocular interaction and disparity coding in area 19 of visual cortex in normal and split-chiasm cats (1993)
    Springer
    Experimental brain research 94 (1993), S. 405-417 
    Details
    ISSN: 1432-1106
    Keywords: Area 19 ; Corpus callosum ; Split chiasm ; Spatial disparity ; Binocular interaction ; Cats
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Binocular disparity, resulting from the projection of a three-dimensional object on the two spatially separated retinae, constitutes one of the principal cues for stereoscopic perception. The binocularity of cells in one hemisphere stems from two sources: (1) the ganglion cells in the homonymous temporal and nasal hemiretinae and (2) the contralateral hemisphere via the corpus callosum (CC). The objectives of this study were, on one hand, to determine whether disparity-sensitive cells are present in a “higher order” area, namely area 19 of the visual cortex, of the cat and, on the other hand, to ascertain whether the CC contributes to the formation of these cells. As in areas 17–18, two types of disparity-sensitive neurons were found: one type, showing maximal interactive effects around zero disparity, responded with strong excitation or inhibition when the stimuli presented independently to the two eyes were in register. These neurons are presumed to signal stimuli situated about the fixation plane. The other type, also made up of two subtypes of opposed valencies, gave maximum responses at one set of disparities and inhibitory responses to the other set. These are presumed to signal stimuli situated in front of or behind the fixation plane. Unlike areas 17–18, however, disparity-sensitive cells in area 19 of the normal cat were less finely tuned and their proportion was lower. In the split-chiasm animal, very few cells were sensitive to disparity. These results, when coupled with behavioral data obtained with destriate animals, indicate that (1) area 19 is probably less involved in the analysis of disparity information than area 17, (2) the disparity-sensitive neurons that are sensitive to disparity are not involved in the resolution of very fine three-dimensional spatial detail, and (3) the CC only determines a limited number of these cells in the absence of normal binocular input.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00230199
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  • 8
    Electronic Resource
    Electronic Resource
    Sensory modality distribution in the anterior ectosylvian cortex (AEC) of cats (1994)
    Springer
    Experimental brain research 97 (1994), S. 404-414 
    Details
    ISSN: 1432-1106
    Keywords: Anterior ectosylvian cortex ; Vision ; Audition ; Somesthesis ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Modality specificity of neuronal responses to visual, somesthetic and auditory stimuli was investigated in the anterior ectosylvian cortex (AEC) of cats, using single-unit recording techniques. Seven classes of neurons were found, and according to their responsiveness to sensory stimuli regrouped into three categories: unimodal, bimodal and trimodal. Unimodal cells that responded to only one of the three stimulus modalities formed 59% of the units; 30.2% were bimodal, in that they showed a clear increase of neuronal discharges to two of the three stimulus types; 10.8% were defined as trimodal because they responded to all three stimulus modalities. Although the different categories of cells were intermingled within the AEC, indicating a certain degree of overlap between sensory modalities, some clustering of cell types was nonetheless evident. Thus, the somatosensory responsive cells were mainly located in the anterior two-thirds of the dorsal bank of the anterior ectosylvian sulcus. Visually responsive cells were concentrated on the ventral bank of the sulcus, whereas neurons with an auditory response occupied the banks and fundus of the posterior three-quarters of the sulcus. The histological distribution and physiological properties of AEC neurons suggest that this cortical region is a higher-order associative area whose function may be to integrate information from different sensory modalities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00241534
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  • 9
    Electronic Resource
    Electronic Resource
    Binaural noise stimulation of auditory callosal fibers of the cat: responses to interaural time delays (1995)
    Springer
    Experimental brain research 104 (1995), S. 30-40 
    Details
    ISSN: 1432-1106
    Keywords: Corpus callosum ; Sound localization ; Interaural time delays ; Midline fusion ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The corpus callosum, the principal neocortical commissure, allows for the interhemispheric transfer of lateralized information between the hemispheres. The aim of the present experiment was to study callosal transfer of auditory information in the cat, with particular reference to its contribution to sound localization. The corpus callosum was approached under direct visual control, and axonic responses were recorded under light anesthesia using glass micro-pipettes. Results showed that auditory information is transmitted in the posterior portion of the callosum. Diotic presentations, in which interaural time delay was manipulated, indicated that, for a large number of fibers, the largest excitatory or inhibitory interactions were obtained at null interaural time delay, a condition which supports the notion of a callosal contribution to auditory midline fusion. However, an important number of callosal fibers was also found to be excited maximally at specific, non-zero interaural time delays, suggesting that they preferred sounds situated at spatial locations other than the midline. The results are discussed in relation to those obtained electrophysiologically for the visual and somesthesic modalities and in terms of results obtained in human and animal behavioral experiments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00229853
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  • 10
    Electronic Resource
    Electronic Resource
    Binocular interactions and spatial disparity sensitivity in the superior colliculus of the siamese cat (1999)
    Springer
    Experimental brain research 124 (1999), S. 181-192 
    Details
    ISSN: 1432-1106
    Keywords: Key words Binocular vision ; Electrophysiology ; Ocular dominance ; Stereopsis ; Strabismus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  In Siamese cats, a genetically determined massive misrouting of retinal ganglion cells toward the contralateral hemisphere, as well as an accompanying strabismus, is believed to underlie the extreme paucity of binocular cells in the primary visual cortex. However, binocular cells have been shown to be present in more important numbers at the collicular level. The present study aims at investigating binocular interactions and sensitivity to spatial disparity in the superior colliculus of the Siamese cat. The activity of single units was recorded in the superficial layers of paralyzed and anesthetized Siamese cats. Although most collicular cells were monocularly driven, a significant proportion could be driven through both eyes (34/216 or 16%). Upon isolation of a binocular cell, the receptive fields were separated, then simultaneously stimulated with two light bars. A temporal delay was introduced between the arrival of the bars in the receptive fields to generate spatial disparities (–3° to +3°, in 0.5° or 1° steps). Results showed that some binocular cells presented disparity tuning profiles similar to the tuned excitatory (12/34), tuned inhibitory (2/34), near (2/34) and far (3/34) cells found at various cortical levels in the normal cat. These interactions might allow for coarse binocular fusion as well as play a role in the initiation of vergence and the fixation of the eyes upon the appropriate plane of vision.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002210050613
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