Figure 6.

Various aspects of formed OSM at the end of Phase 1 including orientation gradients, orientation selectivity, and orientation preferences of neurons are shown here. (A) The oriented bar stimuli are provided as input to the LGN neurons and the raw firing rates of the E neurons in layer 4 are measured (“Materials and Methods”). (B) The smoothed responses (see “Materials and Methods”) of orientation preferences is computed and plotted in color. The oriented bars on the right provide the cyclic color code ranging from 0° to 180°. (C) Orientation selectivity of each E neuron is indicated using a grayscale map. The brighter colors indicate high selectivity where those E neurons in layer 4 respond sharply to a very narrow range of orientations and vice versa. The color scale shows the magnitudes of responses in a relative fashion. For example, neurons in the neighborhood of neuron at (110, 100) show strong selectivity (score of 110) to only 120° but not to other orientations while a neuron at (80, 50) shows a weak selectivity (score of 8) to all orientations including its preferred orientation of 150°. (D) The absolute magnitude of the orientation gradients at each E neuron is shown here. Here lighter values indicate high gradients (closer to 90°) while black indicates there neighborhoods have similar orientation preferences and thus no gradient at all. Orientation selectivity and orientation gradients are linked such that regions of high selectivity typically have low gradients while regions of low selectivity have high gradients in a manner qualitatively consistent with the data from the Blasdel paper. The discontinuous changes either occur alone (singularities), or they group together along lines (fractures). While there are many lines of fracture in this phase, there are no singularities, linear zones or pinwheels.