Fig. 5. STA, STC, and STCL comparison: balanced ON-OFF RGC. Scatter plot of dimension-reduced spike-triggered stimuli (dots in A) showing two blobs, whose centers (red triangles in A) and covariances (red ellipses in A) are correctly identified by clustering analysis. In contrast, a classical STA (blue square in A) and STC (blue ellipse in A) treat the multi-modal spike-triggered stimuli as one chunk and fail to capture individual blobs. (B) Shown is a histogram of projections to the first eigenvector (v1) showing two distinctive peaks, which correspond to multiple RF groups. In temporal (C, left) and spatial (C, right) STA profiles, this cell’s RF is hardly identifiable. (D) The STC’s 10 largest eigenvalues (left column, inset) show the largest eigenvalue standing out from the others. The corresponding eigenvector shows two peaks with opposite signs at 300 ms and 200 ms before a spike in the temporal (D, left) and spatial (D, right) profiles. However, because of the scale ambiguity of eigenvectors, the polarity of RGC types cannot be determined from STC analysis. In contrast, the temporal (left) and spatial (right) profiles of stimulus cluster centers identified by STCL analysis clearly separate ON (E, top) and OFF (E, bottom) responses. (F) Shown are post-stimulus time histogram (PSTH) graphs of RGC response to full-field illumination of 4 s ON and 4 s OFF duration (time bin: 100 ms). The red horizontal line inside the PSTH graph indicates one-sided 95% confidence interval.
© Exp Neurobiol
