Scatter plot of selectivity index and cortical distance.

<p>Each dot represents selectivity index (SI) for each stimulus condition and anatomical distance between the centers of S1 and S2 for that condition. Mariginal histograms are also shown. The cortical distance was estimated from the cortical magnification factor <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0047543#pone.0047543-Horton1" target="_blank">[31]</a>. Data are combined single and multiple unit data obtained from 227 stimulus conditions (i.e., S1 positions) for 105 recording sites in 2 monkeys. Black dots and bars indicate significant <i>SIs</i> (69 of 227 cases, 30.40%, p<0.05), as evaluated with a bootstrapping method. The proportion was also consistent for single units alone (23 of 92 stimulus conditions, 25%) and multiple unit activitiy (46 of 135 stimulus conditions, 34.07%).The proportion of significant <i>SI</i> decreased with the cortical distance between S1 and S2.