e., more feedforward than feedback interactions). To quantify these impressions across the population, for each CCG, we computed an asymmetry index [ASI = (R − L)/(R + L), where R and L are the numbers

of interactions to the right and left of zero, respectively]. This index ranges from −1 to 1, with larger numbers indicating greater asymmetry, where a value of 0.33 indicates that the distribution to the right of zero is twice that to the left NVP-BEZ235 in vitro of zero. This index indicates the directionality of the population of coincidences within a CCG and is not the same as peak position. For both same-digit (Figure 7E, blue) and adjacent-digit (Figure 7E, red) populations of A3b-A1 pairs, the distributions of ASI of individual CCGs were significantly

shifted to the right (Wilcoxon signed-rank tests, p < 0.001; same-digit pairs, median value = 0.07, n = 160 pairs; adjacent-digit pairs: median = 0.06, Cisplatin n = 153 pairs), suggesting an overall feedforward direction from area 3b to area 1. There were no significant differences in ASI distribution between same-digit (blue) and adjacent-digit (red) interareal pairs (Figure 7E, p > 0.1). Thus, although the strongest interactions appear to be due to common input (i.e., correlograms are centered on zero), for coincidences slightly weaker in strength (i.e., away from 0), more occur with positive than with negative latency. This population bias is consistent with a predominance of feedforward interactions. We also examined directionality in the intra-areal A3b-A3b population. All of these pairings were between adjacent digits. For all 3b-3b pairs, we defined all asymmetries as positive (biased to the right, because there is no expected difference between, e.g., D2-D3 versus D3-D2 pairs) and combined all

pairs into a single histogram (Figure 7F). We found that the ASI distributions exhibited a strong positive bias (p < 0.001, n = 63 pairs of A3b-A3b, median value 0.20). What is interesting here is that we did not obtain symmetric peaks, which suggests that 3b-3b interactions are less likely to be due to common input and that a large Dipeptidyl peptidase portion of the interactions are directional (from one digit to the adjacent digit). Furthermore, the fact that this intra-areal asymmetry is so prominent, significantly more so than that between 3b-1 interactions (Figure 7E, p < 0.001) suggests a strong lateral flow of intra-areal information. In summary, these neuronal interactions are consistent with and extend the interpretation of anatomical and resting-state connectivity patterns. The functional connectivity patterns within and between areas 3b and 1 are consistent with the strongly mediolateral and anteroposterior axes of anatomical labeling and resting-state connectivity patterns. Previous studies have suggested that global resting-state connectivity is anchored by anatomical connectivity.