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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 60 (1985), S. 151-158 
    ISSN: 1432-1106
    Keywords: Striate simple cells ; Static-field plots ; Receptive field subregions ; Moving light bar responses ; Hand and quantitative methods
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Cells in the simple family respond to a moving light bar with an average response histogram that is most commonly unimodal (single peak: encounter frequency, 64%) and less commonly bimodal (33%) or trimodal (3%). The mean width of the principal response peak given by hypercomplex I cells is narrower than that of simple cells and they have a lower mean optimal stimulus velocity. In a series of 74 cells (simple, 47; hypercomplex I, 27), detailed comparison of the spatial relations between the response peaks to the moving bar and the subregions to the stationary flashing bar led to the concept of a boundary response. The term “boundary response” refers to an isolated response peak occurring as a moving light bar leaves an OFF subregion that is the last in the sequence of subregions traversed by the bar. The presence of a boundary response leads to an apparent discrepancy between the number of response peaks to a moving light bar and the number of ON subregions in the static-field plot. The boundary response is necessarily completely direction selective. A detailed comparison of the properties of cells as revealed by hand and quantitative methods showed a very good agreement between the two methods in respect to the assignment of cells to the simple, B- and complex cell families. There were, however, serious discrepancies in respect to the receptive field organization of cells in the simple family. In particular, many cells that either failed to respond adequately to hand stimulation by a stationary flashing bar or exhibited only a single receptive field “subregion”, all responded with two or more subregions when examined quantitatively by the same kind of stationary stimulus.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 57 (1985), S. 512-522 
    ISSN: 1432-1106
    Keywords: Striate simple cells ; Direction selectivity ; Static-field plots ; Moving edge responses
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Quantitative estimates of the direction selectivities of 118 simple cells in response to moving light bars were expressed as a percentage calculated from the ratio of the response peaks: (preferred minus nonpreferred)/preferred. Virtually all simple cells were direction selective to some degree (mean direction selectivity 73.6%). Static-field plots to a stationary flashing bar were prepared from 74 of the 118 cells. Particular attention was given to the 42 cells with only two subregions in their static-field plot, one subregion responding at light on and the other at light off. It was concluded that interactive effects between subregions, whether synergistic or antagonistic, have little if any influence on the direction selective mechanism when the stimulus is a narrow light bar. Eighty two of the 118 cells were also tested with moving light and dark edges and of these 53 had response profiles with only two response peaks, one to the light edge and the other to the dark edge. Forty one of the 53 cells were each not only direction selective for both a light edge and a dark edge but also had a preferred direction for both edges that was the same as that for a light bar. Only two cells had preferred directions for both light and dark edges that were opposite to the direction preferred by the light bar. With one possible exception, every cell with two response peaks to moving edges and two subregions in the static-field plot showed a one-to-one correspondence between the ordinal sequence of the response peaks and the ordinal sequence of the subregions. Depending upon the polarity of the moving edge and the ordinal sequence of the subregions, the mean level of the direction selectivity to a moving edge was significantly below that to a narrow moving light bar. This reduction in the degree of the direction selectivity appears to be due to an interaction between the subregions leading to a reduction in the amplitude of the response in the preferred direction rather than a suppression of the direction selective mechanism that operates in the nonpreferred direction. Moving edges cause a weak interactive effect between the subregions that seems always to reduce the degree of the direction selectivity, never increasing it.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-1106
    Keywords: Striate simple cells ; Static-field plots ; Receptive field subregions ; Moving edge responses
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary For each of 74 simple striate cells a quantitative analysis was made of the width dimensions and spatial arrangements of the subregions responding either at light on (ON subregion) or at light off (OFF subregion). It was concluded that every cell has at least two and no more than four subregions. Cells with two subregions (57%) were much more commonly encountered than those with three (32%) or four (11%). For most cells adjacent subregions were significantly overlapped, the region of overlap responding both at light on and at light off. In the case of cells with two subregions, the overlap averaged 32% of the overall width of the two subregions. Despite the degree of the overlap, there was, on this basis, still a large measure of discrimination between cells in the simple family and those in the B-cell and complex families. In general the receptive field profiles of cells with three and four subregions were only marginally wider than those with only two subregions. In any given receptive field, the subregions tend to be roughly equal in width so that, in cells with four subregions, the subregions are, on the average, distinctly narrower than they are in cells with only two. Hypercomplex I cells tend to have receptive fields with three and four subregions much more commonly than simple cells and these cells are encountered much more frequently in cortical cell laminae 2, 3 and 4 than in lamina 6. In lamina 6 most of the cells in the simple family have receptive fields with only two subregions. The width dimensions and spatial sequences of the response peaks to moving light and dark edges were quantitatively analyzed in response profiles prepared from 82 cells. In general, for any given receptive field, the response peaks to moving edges have a one-to-one correspondence with the subregions to a stationary flashing bar. When this is not the case, the tendency is for the number of response peaks to edges to be less than the number of subregions rather than more.
    Type of Medium: Electronic Resource
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