Meeting Summary: In this second working group on the brain we shall build on some of the foundational discussions raised in the first meeting. These included significant debate around the merits of correlation vs. causation, indicators or indices of the loss of function, and the relationship among levels required to explain failure - from the genetic and cellular to the cognitive and behavioral (including states such as sleep and anesthesia). Mechanisms of loss of function discussed will range from cell to network drop-out. We shall return to some of the key questions that motivated the first meeting with a better sense of the limitations of data sets and tools of analysis. This includes the synthesis and integration of neurology with several areas of complexity science to include adaptation and robustness in system aging, early network-based indicators for risk factors, the application of criticality and related tipping point to regime shifts, the measurement of long-range order and disorder across the brain, and methods for analyzing collective dynamics in the aging and diseased brain.