Errors on the Trail Making Test Are Associated with Right Hemispheric Frontal Lobe Damage in Stroke Patients

Abstract

Measures of performance on the Trail Making Test (TMT) are among the most popular neuropsychological assessment techniques. Completion time on TMT-A is considered to provide a measure of processing speed, whereas completion time on TMT-B is considered to constitute a behavioral measure of the ability to shift between cognitive sets (cognitive flexibility), commonly attributed to the frontal lobes. However, empirical evidence linking performance on the TMT-B to localized frontal lesions is mostly lacking. Here, we examined the association of frontal lesions following stroke with TMT-B performance measures (i.e., completion time and completion accuracy measures) using voxel-based lesion-behavior mapping, with a focus on right hemispheric frontal lobe lesions. Our results suggest that the number of errors, but not completion time on the TMT-B, is associated with right hemispheric frontal lesions. This finding contradicts common clinical practice-the use of completion time on the TMT-B to measure cognitive flexibility, and it underscores the need for additional research on the association between cognitive flexibility and the frontal lobes. Further work in a larger sample, including left frontal lobe damage and with more power to detect effects of right posterior brain injury, is necessary to determine whether our observation is specific for right frontal lesions.

Figure 1

Overlay lesion plots of all thirty patients in MNI space. Eight axial slices. The number of overlapping lesions is illustrated by color, from violet (N = 1) to red (N = 30). Maximum overlap occurred in the right frontal lobe. The area colored light blue indicates overlapping lesions in eleven patients (37% lesion overlap). Numbers indicate MINI coordinates.

Figure 2

Anatomical results obtained from the lesion subtraction analysis on the number of TMT-B total errors. (a) Overlay lesion plots for those patients who committed two or more total errors (Mdn = 1) on the TMT-B (N = 13). The number of overlapping lesions is illustrated by color, from violet (N = 1) to red (N = 13). (b) Overlay lesion plots for those patients who committed less than two total errors on the TMT-B (N = 17). The number of overlapping lesions is illustrated by color, from violet (N = 1) to red (N = 17). (c) Overlay plots of the subtracted superimposed lesions of the patients with two or more total errors on the TMT-B minus the patients with less than two total errors on the TMT-B. Colors code increasing frequencies from dark-red (difference from 1% to 20%) to white-yellow (difference from 81% to 100%), indicating regions damaged more frequently in patients who committed relatively many total errors on the TMT-B. The colors from dark-blue (difference from −1 to −20%) to light-green (difference from −81 to −100%) indicate regions damaged more frequently in patients who committed relatively few total errors on the TMT-B.

Figure 3

Anatomical results obtained from the voxel-based lesion-behavior mapping (a) on the number of TMT-B total errors, (b) on the number of TMT-B shifting errors (error type A + type B), and (c) on the number of TMT-B sequencing errors (error type C + type D). The location of voxels for which the voxel-based lesion-behavior mapping indicated that the observed Bz surpassed z _crit is shown. See text for details. Numbers indicate MNI coordinates.