a Although we categorized Expert Opinion as a fully independent data source, it differs from other categories because it is not empirical (Zeller et al. 2012).
Twenty-two of the 34 studies that validated their current density (output) models (~65%) reported agreement between model predictions and validation data, while four (12%) found poor agreement between model results and validation data. The remaining eight (~24%) either reported mixed results or were inconclusive.
After an initial and substantial increase, the proportion of studies that specified the type of connectivity being modeled leveled off or even declined in recent years (Figure 2). Studies that implemented some form of SUA seem to have been slowly increasing, and there has been no clear trend through time in the proportion of studies validating connectivity models (Figure 2).