Who are "senior/key personnel" and how do they differ from "other significant contributors?"

Who are "senior/key personnel" and how do they differ from "other significant contributors?"

The NIH defines senior/key personnel as individuals who contribute substantially to the scientific development or execution of a project. For example, the program director/principal investigator (PD/PI) is always considered senior/key personnel. Furthermore, the PD/PI may designate additional senior/key personnel if they fit the definition. Biographical sketches, other support information, and level of effort greater than zero are all required of senior/key personnel named in the application.

Other significant contributors are those that are committed to contribute to the project, but without measurable effort (zero person months or "as needed"). Biographical sketches of other significant contributors are required, but other support information is not.

Source: NIH Extramural NEXUS, November 2007 issue