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Abstract
Choice reaction time (CRT), the time required to discriminate and respond appropriately to different stimuli, is a basic measure of attention and processing speed. Here, we describe the reliability and clinical sensitivity of a new CRT test that presents lateralized visual stimuli and adaptively adjusts stimulus onset asynchronies using a staircase procedure. Experiment 1 investigated the test–retest reliability in three test sessions performed at weekly intervals. Performance in the first test session was accurately predicted from age and computer-use regression functions obtained in a previously studied normative cohort. Central processing time (CentPT), the difference between the CRTs and simple reaction time latencies measured in a separate experiment, accounted for 55% of CRT latency and more than 85% of CRT latency variance. Performance improved significantly across the three test sessions. High intraclass correlation coefficients were seen for CRTs (0.90), CentPTs (0.87), and an omnibus performance measure (0.81) that combined CRT and minimal SOA z-scores. Experiment 2 investigated performance in the same participants when instructed to feign symptoms of traumatic brain injury (TBI): 87% produced abnormal omnibus z-scores. Simulated malingerers showed greater elevations in simple reaction times than CRTs, and hence reduced CentPTs. Latency-consistency z-scores, based on the difference between the CRTs obtained and those predicted based on CentPT latencies, discriminated malingering participants from controls with high sensitivity and specificity. Experiment 3 investigated CRT test performance in military veterans who had suffered combat-related TBI and symptoms of post-traumatic stress disorder, and revealed small but significant deficits in performance in the TBI population. The results indicate that the new CRT test shows high test–retest reliability, can assist in detecting participants performing with suboptimal effort, and is sensitive to the effects of TBI on the speed and accuracy of visual processing.
Highlights
Choice reaction times (CRTs) have been widely used to quantify attention and processing speed in clinical populations, including patients with head injury (Stuss et al, 1989b; Bashore and Ridderinkhof, 2002; Iverson et al, 2005), post-traumatic stress disorder (PTSD; Ponsford et al, 2012), multiple sclerosis (Snyder et al, 2001), Parkinson’s disease (Papapetropoulos et al, 2010), and schizophrenia (Pellizzer and Stephane, 2007)
intraclass correlation coefficients (ICCs) were high for CRT z-scores (0.89), Central processing time (CentPT) z-scores (0.86), and omnibus z-scores (0.81), while they were somewhat lower for log-minimum SOA (mSOA) z-scores (0.72), and considerably reduced for measures of trial-by-trial CRT variance (0.41) and the CV (0.27)
In Experiment 3, we evaluated the sensitivity of the CRT test in a mixed population of chronic mild TBI (mTBI) and severe TBI (sTBI) patients, with the hypothesis that we would observe more severe deficits following sTBI than mTBI
Summary
Choice reaction times (CRTs) have been widely used to quantify attention and processing speed in clinical populations, including patients with head injury (Stuss et al, 1989b; Bashore and Ridderinkhof, 2002; Iverson et al, 2005), post-traumatic stress disorder (PTSD; Ponsford et al, 2012), multiple sclerosis (Snyder et al, 2001), Parkinson’s disease (Papapetropoulos et al, 2010), and schizophrenia (Pellizzer and Stephane, 2007). In Experiment 1, we describe the reliability and precision of a new CRT test (Woods et al, 2015c); in Experiment 2, we investigate its sensitivity in detecting participants feigning cognitive impairments; and in Experiment 3, we investigate its sensitivity in detecting processing-speed deficits among patients with combat-related traumatic brain injury (TBI) and PTSD. The CRT test incorporates a rapid serial visual featureconjunction task in which participants press one mouse button in response to a target letter (blue P) and press the other mouse button to respond to non-target letters that share color (blue F), shape (orange P), or neither target feature (orange F; see Figure 1). Latencies are reduced when stimuli and responses are spatially compatible, i.e., when the mouse button used for responding is ipsilateral to the hemifield of stimulus presentation (Klein and Ivanoff, 2011)
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