| Abstrakt: |
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. |
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