Figure 9. The effect of anisotropy and jitter on elastic net map co-circularity.

To test whether true underlying co-circularity could be destroyed by uncorrected anisotropy or jitter, we added these to the elastic net maps in the same way as for the experimental maps (Fig. 5). In particular we investigated the case ε = 0, where the simulated maps display strong co-circularity with zero offset. A The maps were stretched or contracted in the x-direction by ratio ρ. As before we examined ρ = 0.75 and ρ = 1.3. The value of D_best was shifted when anisotropy was introduced. However, even under significant anisotropy the presence of co-circularity was reliably detected. Importantly, under all conditions for all the samples the measured value of τ_best was within 5° of the true origin (data not shown). This indicates that any anisotropy in the cat maps would not impede the detection of co-circularity or the origin τ_best. B We examined co-circularity with offset D_best and τ_best for maps when jitter was added to cortical positions. The jitter consisted of uniform random noise between [−1, 1) pixels. The jitter did not significantly affect measured co-circularity or the value of τ_best.