This study evaluated cognitive set-shifting in 12 patients with focal
lesions in the lateral prefrontal cortex (LPC) by examining their
performance on the Trail Making Test from the Delis-Kaplan Executive
Function System (D-KEFS). Patients with LPC lesions performed
significantly worse than controls on the D-KEFS Trail Making Test on the
Letter Sequencing, Number-Letter Switching (set-shifting), and Motor Speed
conditions. Patients with LPC lesions performed significantly more slowly
on the Number-Letter Switching condition even after controlling for
performance on the four baseline conditions of the test. In addition,
patients with LPC lesions exhibited significantly elevated error rates on
the Number-Letter Switching condition. Results suggest that LPC lesions
can lead to impaired cognitive set-shifting on a visual-motor sequencing
task. (JINS, 2007, 13, 704–709.)