Final data from DA-PASAT

The Paced Auditory Serial Addition Test (PASAT) is widely used to evaluate
processing speed and executive function in patients with multiple sclerosis,
traumatic brain injury, and other neuropsychiatric disorders. In the PASAT, subjects
listen to sequences of digits while continuously reporting the sum of the last
two digits presented. Four different stimulus onset asynchronies (SOAs) are
usually tested, with difficulty increasing as SOAs are reduced. Ceiling effects
are common at long SOAs. In contrast, the digit delivery rate often exceeds the
subject’s processing capacity at short SOAs, resulting in frustration and causing
some subjects to stop performing altogether. In addition, subjects may adopt an
“alternate answer” strategy at short SOAs, which reduces the test’s demands on working-memory
and processing speed. Consequently, studies have shown that the number of dyads
(consecutive correct answers) is a more sensitive measure of PASAT performance than
the overall number of correct sums. Here, we describe a 2.5-minute computerized
test, the Dyad-Adaptive PASAT (DA-PASAT), where stimulus onset asynchronies
(SOAs) are adjusted based on successive pairs of correct responses and processing
capacity is reflected in the minimum SOA (minSOA) achieved in 54 trials. Experiment
1 gathered normative data in two large populations: 1617 subjects in New
Zealand ranging in age from 18 to 65 years, and 214 Californians ranging in age
from 18 to 82 years. Minimum SOAs were influenced by age, education, and daily
hours of computer-use. Minimum SOA z-scores, calculated after factoring out the
influence of these factors, were virtually identical in the two control groups,
as were response times (RTs) and dyad ratios (the proportion of hits occurring
in dyads). Experiment 2 measured the test-retest reliability of the DA-PASAT in
44 young subjects who underwent three test sessions at weekly intervals. High
intraclass correlation coefficients (ICCs) were found for minSOAs (0.87), response
times (0.76), and dyad ratios (0.87). Performance improved across test sessions
for all measures. Experiment 3 investigated the effects of simulated
malingering in 50 subjects: 42% of simulated malingerers produced abnormal
(p< 0.05) minSOA z-scores. Simulated malingerers with abnormal scores were
distinguished with 87% sensitivity and 69% specificity from control subjects
with abnormal scores by excessive differences between training performance and
during the actual test. Experiment 4 investigated patients with traumatic brain
injury (TBI): patients with mild TBI performed within the normal range while patients
with severe TBI showed deficits. The DA-PASAT reduces the time and stress of
PASAT assessment while gathering sensitive measures of dyad processing that reveal
the effects of aging, malingering, and traumatic brain injury on performance.

节奏听觉连续加法测试（Paced Auditory Serial Addition Test, PASAT）被广泛用于评估多发性硬化、创伤性脑损伤及其他神经精神疾病患者的信息处理速度与执行功能。在该测试中，受试者需聆听一系列数字，并持续播报当前呈现数字与前一数字的和。通常会设置四种不同的刺激呈现起始间隔（Stimulus Onset Asynchrony, SOA），测试难度随SOA缩短而提升。长SOA条件下易出现天花板效应；反之，当SOA较短时，数字呈现速率往往超出受试者的信息处理能力，引发挫败感，甚至导致部分受试者直接终止测试。此外，受试者在短SOA条件下可能采用"交替作答"策略，这会降低测试对工作记忆与信息处理速度的要求。因此，已有研究表明，连续正确作答组（dyads，即连续答对的题目数）的数量，相较于总正确作答数，是更为敏感的PASAT表现评估指标。本研究介绍了一款时长2.5分钟的计算机化测试——双对自适应节奏听觉连续加法测试（Dyad-Adaptive PASAT, DA-PASAT），该测试可根据连续两道正确作答的情况调整刺激呈现起始间隔（SOA），并以54次试次中达成的最小刺激呈现起始间隔（minimum SOA, minSOA）反映受试者的信息处理能力。实验1采集了两大人群的常模数据：分别为1617名年龄18~65岁的新西兰受试者，以及214名年龄18~82岁的加利福尼亚州受试者。最小刺激呈现起始间隔（minSOA）会受到年龄、受教育程度及每日电脑使用时长的影响。在剔除上述因素的影响后计算得到的minSOA Z分数，在两个对照组中几乎一致；反应时（response times, RT）与双对作答比率（dyad ratios，即连续正确作答组中正确命中题目的占比）的结果亦如此。实验2对44名年轻受试者进行了重测信度评估，该群体每周接受一次测试，共完成3次测试环节。结果显示，minSOA、反应时与双对作答比率的组内相关系数（intraclass correlation coefficient, ICC）分别为0.87、0.76与0.87，数值均较高。所有评估指标的得分均随测试次数增加而提升。实验3探究了伪装诈病对测试表现的影响，共纳入50名受试者：其中42%的伪装诈病者的minSOA Z分数呈异常水平（p<0.05）。通过对比训练阶段与正式测试阶段的表现差异，可将得分异常的伪装诈病者与得分异常的对照组受试者区分开来，该区分的灵敏度为87%，特异度为69%。实验4针对创伤性脑损伤（traumatic brain injury, TBI）患者展开研究：轻度TBI患者的测试表现处于正常范围，而重度TBI患者则表现出认知功能缺损。DA-PASAT不仅缩短了传统PASAT评估的时长与应激程度，还可通过采集双对信息处理的敏感指标，揭示衰老、伪装诈病及创伤性脑损伤对受试者表现的影响。