The Delis-Kaplan executive function system (D-KEFS) trail-making test (TMT)

The TMT is a timed neuropsychological tool to assess visual, psychomotor, and executive functions, mainly the ability to shift cognitive sets on a visuomotor sequencing task^62,66. Examinees are asked to visually scan the target stimuli and follow five different conditions: (1) marking a target stimulus among letter and number distracters (i.e., Visual Scanning), (2) connecting numbers in ascending order among letter distracters (i.e., Number Sequencing), (3) connecting letters in alphabetical order among number distracters (i.e., Letter Sequencing), (4) alternating between numbers to letters in ascending and alphabetical order (i.e., Number-Letter Sequencing), and (5) drawing over a dotted line (i.e., Motor Speed). While conditions 1, 2, 3, and 5 rely more on basic attentional and motor abilities and pose relatively low cognitive demands (i.e., target identification and maintaining set), the fourth condition requires examinees to inhibit and shift sets (number-letter). The different conditions contextualize the performance on the fourth trial, as they represent the basic requirements to perform on it (with the exception of set-shifting). Several large-scale neuronal networks participate in TMT performance, mostly of prefrontal and parietal regions⁶⁷.

The main performance variables of the TMT are completion times of each of the five conditions. In the current study, we used the scaled scores (mean ± SD = 10 ± 3) of condition completion times. Higher scaled scores reflect better performance (i.e., faster completion times). See Table ​Table11 for means. Although the TMT is less sensitive to perseverative erroring, perseverating will result in slower completion time.