All released and recycling fractions are expressed as percent of the total vesicle pool. Anatomically, the total number of vesicles at a synapse is correlated with bouton volume (Knott et al., 2006; Murthy et al., 2001). Vesicular release, on the other hand, is restricted to the active zone at the surface of the bouton. Linear scaling has been demonstrated between Pr and the number of surface-docked vesicles (Murthy et al., 2001). Therefore, the most straightforward assumption would be linear scaling between the number of released vesicles (R) and bouton surface area (A): R = k × A (with k being a proportionality factor), equivalent to a 2/3-power scaling with

bouton volume (V): R = k × V2/3. If all vesicles were functional, RG7420 mw V could be substituted with the total number of vesicles (ves) filling the selleck kinase inhibitor volume of the bouton. In this case, RF would be expected

to scale as RF = k × ves−1/3. As shown in Figure 3B (black curve), this surface-to-volume function fits our data well (RF = 172 × ves−1/3). Data are reported as mean ± SEM unless indicated otherwise. To test for significance between population means, we used the two-tailed Student’s t test. As nonparametric measures of absolute and relative dispersion of single bouton data, we use the interquartile range (IQR): Q75% − Q25% and the quartile coefficient of variation (QCV): (Q75% − Q25%) / (Q75% + Q25%), respectively. All correlations are expressed as squared Pearson’s correlation coefficients (R2). Statistical significance was assumed when p < 0.05. Boundaries used for assigning significance in figures: not significant (n.s.), p > 0.05; significant, p < 0.05 (∗), p < 0.01 (∗∗), and p < 0.001 (∗∗∗). This work was supported by the Novartis Research Foundation,

isothipendyl SystemsX.ch, and the Kavli Foundation. The authors thank Daniela Gerosa for excellent technical assistance; Yongling Zhu and Charles F. Stevens for the gift of sypHluorin-1X; Roger Y. Tsien for tdimer2; and Corette Wierenga, Volker Scheuss, and the members of the Oertner lab for critically reading the manuscript. “
“Determination of the functional significance of network modules such as columns and barrels in the mammalian brain has been an ongoing topic of research (Mountcastle, 1997). One of the primary research questions has centered around understanding the similarities and differences in the response properties of neurons within the modules (Linden and Markram, 2003). Due to difficulties in simultaneously capturing the morphologies, connectivities, and functional activities of individual neurons, it remains unclear how these neurons that are part of a module interact with each other and contribute to modular network outputs.