No systematic effect of overlap on coupling strength. Two examples that illustrate the lack of a systematic effect of summation field overlap on signal coupling. (A) Cross-correlation of MUA, monkey K. (B) Cross-correlation of LFP, monkey K. Pairs of recording sites were divided in three groups with small, medium and large residual from the fit of the summation field overlap (red, orange and green dots, see text for details). Signal coupling showed a pronounced dependency on distance of the recording sites. The analysis of residuals revealed a significant negative correlation of overlap and cross-correlation strength of MUA and a positive correlation of overlap and coherence of LFP for monkey K. However, as is evident from the plots, these effects are unsystematic and small. Data from the coherence measure and from the other monkey also fail to reveal a systematic effect of overlap on coupling strength.