Fig. 3.

Schematic illustration of the measurement of disconnection. Both of the tract images that we consider are a single, connected object. Tracts are considered to be disconnected if a lesion either disconnects one part of the tract from another (Lesion A), or completely destroys one end of the tract (Lesion B). To make the latter measurement, we place a ‘bookend’ at each extreme of the tract, and search for instances where one bookend is separated from the others, after subtracting a given patient's lesion. Since both of the tracts that we consider here have two anterior projections from one posterior source, we add three bookends to each image before making our measurements. Disconnection occurs if, after subtracting a lesion, and of those three bookends are isolated from the others; in the figure, Lesion B disconnects bookend 2 from the others.