TABLE 2.

Cognitive outcome variables employed to create a composite cognitive score to assess disease‐related brain‐function relationships

Task	Computerized/paper & pencil	Description	Outcome variable	Cognitive domain assessed
N‐back (Kirchner, 1958)	Computerized	Participants were presented with a series of letters, 3 s apart, and asked to judge whether the current letter matched the previous letter (one‐back condition) or the letter presented two letters back (two‐back condition). The one‐back and two‐back conditions were presented separately in 20 randomly ordered trials. Participants made responses manually by pressing on the letter “A” on the keyboard. No responses were required for nontargets.	Percentage of correct responses in the one‐back and two‐back condition	Encoding, temporary storage and updating of stored information with new upcoming information, inhibition of irrelevant items
Digit span test from the WAIS‐R (Wechsler, 1997)	Computerized	Participants were presented with a series of numbers that appeared on the screen one after another. They were required to recall the sequence of numbers by entering them on the keyboard. If the participant could successfully reproduce the series of numbers, they were then presented with a longer series of numbers. Participants continued to receive longer series of numbers until they could no longer repeat them back correctly. The starting list length was 3, and the longest list length possible was 10. The discontinuation criterion was two wrong responses.	Maximum span of digits recalled	Verbal working memory capacity
Visual patterns test (Della Sala, Gray, & Baddeley, 1997)	Paper and pencil	Participants were shown a checkerboard‐like grid, with the squares in the grid each randomly colored. This pattern was displayed for 3 s and is then removed. Subjects were then shown a blank grid and were asked to reproduce each grid. The number of items was sequentially increased. Participants were given unlimited time to reproduce the shapes being viewed.	Maximum grid size recalled correctly	Spatial working memory capacity
Speeded finger tapping task (Reitan & Davison, 1974)	Computerized	Participants were instructed to form a fist shape with their dominant hand, with their fingernails touching down in front of the keyboard space bar. They were then instructed to extend their index finger in order to contact the “space” bar on the keyboard, and to move only their index finger to tap the space bar as quickly as possible.	Mean number of taps over three trials	Motor speed
Stroop interference, word Reading and color naming (Kieburtz, Penney, Corno, et al., 2001; Movement Disorders, 1996; Siesling, Van Vugt, Zwinderman, Kieburtz, & Roos, 1998)	Paper and pencil	For the Stroop Reading and color naming, participants had to name colors (e.g., red, green, blue) and read the words for colors in black ink. For the Stroop interference, participants had to read words of colors (e.g., red, green blue) where the word color was written in a different color ink (Stroop interference).	Number of correct responses	Ability to inhibit cognitive interference, selective attention capacity and skills, processing speed, motor control
Phonetic and category verbal fluency (Kieburtz et al., 2001; Movement Disorders, 1996; Siesling et al., 1998)	Paper and pencil	In the phonetic verbal fluency task participants had to spontaneously produce words orally within a fixed time span (60 s), beginning with a certain letter. In the category verbal fluency, words had to be produced according to semantic constraints (e.g., animals, fruits, vegetables).	Number of correctly generated words within 60 s	Working memory, cognitive inhibition, switching ability and language ability including lexical knowledge and lexical retrieval ability
Trail making (part A & part B) (Kieburtz et al., 2001; Movement Disorders, 1996; Siesling et al., 1998)	Paper and pencil	In part A, participants were asked to connect 25 randomly arrayed dots in numerical order, whereas in part B they were asked to connect dots alternating between numbers and letters in alphabetical order.	Time needed to complete the task	Visual attention, task switching, speed of processing, mental flexibility
Symbol digit modality (Kieburtz et al., 2001; Movement Disorders, 1996; Siesling et al., 1998)	Paper and pencil	Using a reference key, participant had 90 s to pair specific numbers with given geometric figures.	Number of correct responses achieved in 90 s	Attention, perceptual speed, motor speed, and visual scanning

Note: Tasks descriptions are provided, outcome variables and cognitive domains assessed are summarized.