Supplemental Digital Content 2. Details of Neurocognitive tests.
National Adult Reading Test (NART; duration: ~ 5 minutes).1
The NART requires participants to read a list of 50 irregularly spelled words (e.g.
debt, psalm, and ache). A regression equation derived by Crawford, Parker 2,
𝐸𝑠𝑡𝑖𝑚𝑎𝑡𝑒𝑑 𝐼𝑄 = 128.50 − 0.84 ∗ (𝑁𝐴𝑅𝑇 𝑒𝑟𝑟𝑜𝑟𝑠)
was used in the current study to estimate pre-morbid full-scale IQ and was included as a
covariate (Estimated IQ) in the analysis of the neurocognitive measures.
Letter Number Sequencing (LNS; duration: ~ 5 minutes).3
LNS tests working memory capacity. The examiner reads aloud a string of numbers
and letters (e.g., V–1– J–5) and the participant must first recall the numbers in ascending
order and then the letters in alphabetical order (1–5–J–V). The test starts with a sequence of
two items (one number and one letter), and the span increases until the subject fails all three
sequences at a given length. The total number of correctly recalled sequences is recorded.
LNS examines the ability to simultaneously recall and organize stimuli of different and/ or
similar types. It has demonstrated high test-retest reliability and minimal practice effects
when tested over three sessions.4 The LNS test has also demonstrated criterion validity by
showing sensitivity in a clinical population with traumatic brain injury. 5
Cambridge Neuropsychological Test Automated Battery (CANTAB; duration: ~ 33 minutes).6
A selected set of CANTAB tests (Choice Reaction Time, Stop Signal Task and
Stockings of Cambridge) were administered on a Paceblade SlimbookTM 110 Series 12.1
tablet PC. One obligatory training test (i.e., Big/Little Circles [BLC], duration ~ 3 minutes)
was administered initially to introduce the participants to the test system.
Choice Reaction Time (CRT, duration ~ 7 minutes).
The CRT is a test of attention and psychomotor speed. An arrow-shaped stimulus is
displayed on the screen pointing to the right or the left. In response, the subject must press the
corresponding button on a response-pad. The participant has to respond as quickly as possible
without making mistakes. The outcome measure was mean CRT in ms (based on 100 trials).
Stop Signal Task (SST, duration ~ 20 minutes).
SST is a measure of inhibitory control. It requires participants to press one of two
buttons, left and right, to match left and right arrows displayed on a computer screen. Some
trials (25%) require response inhibition, signaled by an auditory tone presented at variable
intervals (the stop signal delay [SSD]) after the arrow stimuli. Participants are encouraged to
respond as quickly as possible to the left or right arrows but to inhibit their response on
hearing the stop signal. An adaptive algorithm modifies the delay of the auditory tone
throughout the test to ensure a 50% successful inhibition rate. The outcome variable is an
estimate of the stop signal reaction time (SSRT) in ms calculated by subtracting the SSD
from the median reaction time on GO trials (GoRT) and provides a measure of inhibition
speed.7 The default setting “last half”, which was used in this study, calculates SSRT from
the last half of the trials.8
Stockings of Cambridge (SOC, duration ~ 10 minutes).
SOC is a computerized version of the Tower of London task, which tests planning and
spatial working memory. The goal of the task is to rearrange a set of three balls in a minimum
number of moves to match a sample pattern. Therefore, participants have to plan their moves
before starting to move the balls. The assessed task has 12 trials (2 x 2 move, 2 x 3 move, 4 x
4 move and 4 x 5 move problems). The outcome variables included in this study are the
number of problems solved in minimum moves; the mean number of the moves spent in
solving an n-move problem (Mean n-Moves), n being 2, 3, 4 or 5; and mean initial thinking
time. The SOC was only administered at discharge due to evidence of substantial practice
effects on planning tasks.4
1.
Nelson HE, Willison J. National Adult Reading Test (NART): Test Manual. 2 ed.
Windsor, UK: NFER Nelson, 1991.
2.
Crawford JR, Parker DM, Stewart LE, et al. Prediction of WAIS IQ with the National
Adult Reading Test: Cross-validation and extension. British Journal of Clinical
Psychology 1989;28:267-273.
3.
Wechsler D. WAIS-III: Wechsler adult intelligence scale. San Antonio, TX: The
Psychological Corporation, 1997.
4.
Lemay S, Bedard MA, Rouleau I, et al. Practice effect and test-retest reliability of
attentional and executive tests in middle-aged to elderly subjects. Clinical
Neuropsychologist 2004;18:284-302.
5.
Donders J, Tulsky DS, Zhu JJ. Criterion validity of new WAIS-III subtest scores after
traumatic brain injury. Journal of the International Neuropsychological Society
2001;7:892-898.
6.
Cambridge Cognition. CANTAB eclipse version 3: Test administration guide.
Cambridge, UK: Cambridge Cognition Ltd.; 2006.
7.
Logan GD, Cowan WB, Davis KA. On the ability to inhibit simple and choice
reaction time responses: a model and a method. J Exp Psychol Hum Percept Perform
1984;10:276-291.
8.
Cambridge Cognition Limited. CANTABeclipseTM Test Administration Guide
Manual version 5.0.0. Cambridge: Cambridge Cognition Limited, 2012.