Development of DS in PMLS and V1. A, Side view of the ferret brain showing the locations of V1 (or area 17) and PMLS (or PSS). B, Responses of three PMLS neurons to drifting gratings, recorded at different ages (indicated above each plot). Grating direction is plotted relative to each neuron's preferred direction. Measures for DS (Ldir and DSI) are given for each neuron. C, Responses of three V1 neurons, following the same format as B. D, Development of Ldir on a per-animal basis for V1 and PMLS. Each circle indicates the mean Ldir across all visually responsive SUs in an animal, as a function of the animal's age. The circle size corresponds to the SEM for animals in which three or more neurons were recorded. Means based on <3 neurons are shown with squares. Note that the per-animal SEM is plotted using a separate scale from the y-axis to maintain visibility of all data points. The legend shows the scale for the SEM. The colored bands indicate the mean ± 1 SEM for animals 40 d and older. The dashed line at P30 indicates average age of eye opening in ferrets. E, Cumulative distribution of SU Ldir values recorded in PMLS for three age groups. The legend in the bottom-right corner indicates the outcome of rank-sum tests between the different groups (dashed line, p > 0.01; solid line, p < 0.01). F, Cumulative distribution of SU Ldir values for V1. Same format as E. G, Normalized Ldir as a function of age for V1 and PMLS. SU Ldir data were divided into 2 d age bins from P29 to 38 and one adult bin from P40 to 52. Data were normalized independently for each area so that the average normalized Ldir in the P29–30 group equals zero, and the average Ldir for P40–52 equals 1. The normalized data were then averaged within each age bin and are plotted as a function of the middle of each age bin. Error bars indicate SEM. H, I, SU firing rates evoked by the preferred direction for PMLS and V1. Same format as E and F. J, K, Distribution of responses evoked by the null direction for V1 and PMLS, same format as E and F.
