Figure 7. Construction of DS complex cells by pooling over inputs from typical DS simple cells.

A. A complex cell model is constructed from a population of typical simple cell models having multiple excitatory and suppressive filters themselves. The family of simple cells is created by spatially shifting all filters of a prototypical simple cell model (see Fig. 6A) over a spatial envelope representing the complex cell receptive field. These inputs are summed and processed by a spiking nonlinearity to generate a firing rate prediction, and a Poisson spike generator then produces simulated data for further analysis. B. Upper panel: the STC filters for the simulated complex cell display a range of different spatiotemporal frequencies and opposing DS for excitatory and suppressive directions, as observed for all complex cells in this study (e.g., Fig. 1E). Lower panel: The localized features inferred from these STC directions comprise a set of homogeneous, spatially shifted units, which closely resemble the dominant excitatory and suppressive directions from the first-order model (Fig. 6A).