Fig. 6.

Effect of the PSF on column mapping. a illustrates the intensity distribution that would be measured from a 1D response to a single stimulus that elicits a signal intensity increase of 1 between 2 and 3 mm and 0 everywhere else (blue line) when sampled with a function with a Gaussian PSF (full-width half-maxima) of 0.7, 1.6, and 2 mm. The response is equivalent to what would be seen in “single-condition” mapping of a single-element “column”. b shows the plots of the case when there are two such responses between 2 and 3 mm and between 3 and 4 mm for two different stimuli and when these responses are mapped as a difference (i.e., as in differential imaging). c shows the results when there are repeated alternating responses to the two different stimuli and when the response is imaged as a difference for the three different PSFs. In this case, the alternating columnar structure extended beyond 0 (in the negative direction) and 8 mm in the positive direction but only the 0- to 8-mm region is illustrated to avoid the edge effects.