PASAT Performance Research Articles

P.139 Random Neural Network Features in Patients with Aggressive Multiple Sclerosis Undergoing Autologous Hematopoietic Stem Cell Transplant

Background: Objective markers of disease progression are needed for patients with multiple sclerosis (MS). Increased randomness in neural networks is hypothesized to be an important cause of morbidity that can be objectified using graph theory. Methods: We use voxel-based structural similarity determined from T1-weighted MRI scans of 23 patients with MS receiving autologous stem cell transplant (ASCT) to compute cortical covariance network parameters. We examine associations between measures of cortical integration or segregation and biochemical/clinical measures of cortical health or function using Spearman correlation coefficients. P<0.05 was considered significant. Results: Path length increase was associated with markers of greater inflammation (ρ=0.56,P<.046) at baseline and reduced Naa/Cr ratio (P<.041) at 12 months. Reduced lambda was associated with markers of greater grey matter atrophy (ρ=0.55,P<.019) after 12 months and lower cognition (ρ=0.56,P<.008) at 12 months. Reduced clustering was associated with higher neurofilament (ρ=-0.68,P<.010) at baseline, greater white matter atrophy (ρ=0.62,P<.006) after 12 months, lower 2-second PASAT performance (ρ=0.56,P<.011) at baseline, and reduced Naa/Cr ratio (P<.001) at 12 months. Conclusions: Reduced cortical integration and segregation (random network features) co-occur with unfavourable markers of cortical health and function in patients with MS receiving ASCT. Network features show promise as important longitudinal markers of patient status and progression.

Regional Cerebellar Volume Loss Predicts Future Disability in Multiple Sclerosis Patients

Cerebellar symptoms in multiple sclerosis (MS) are well described; however, the exact contribution of cerebellar damage to MS disability has not been fully explored. Longer-term observational periods are necessary to better understand the dynamics of pathological changes within the cerebellum and their clinical consequences. Cerebellar lobe and single lobule volumes were automatically segmented on 664 3D-T1-weighted MPRAGE scans (acquired at a single 1.5 T scanner) of 163 MS patients (111 women; mean age: 47.1 years; 125 relapsing–remitting (RR) and 38 secondary progressive (SP) MS, median EDSS: 3.0) imaged annually over 4 years. Clinical scores (EDSS, 9HPT, 25FWT, PASAT, SDMT) were determined per patient per year with a maximum clinical follow-up of 11 years. Linear mixed-effect models were applied to assess the association between cerebellar volumes and clinical scores and whether cerebellar atrophy measures may predict future disability progression. SPMS patients exhibited faster posterior superior lobe volume loss over time compared to RRMS, which was related to increase of EDSS over time. In RRMS, cerebellar volumes were significant predictors of motor scores (e.g. average EDSS, T25FWT and 9HPT) and SDMT. Atrophy of motor-associated lobules (IV-VI + VIII) was a significant predictor of future deterioration of the 9HPT of the non-dominant hand. In SPMS, the atrophy rate of the posterior superior lobe (VI + Crus I) was a significant predictor of future PASAT performance deterioration. Regional cerebellar volume reduction is associated with motor and cognitive disability in MS and may serve as a predictor for future disease progression, especially of dexterity and impaired processing speed.

A-017 Lifestyle activity engagement and cognition: Findings in healthy controls across the lifespan

Abstract Objective Engagement in physical and intellectual activity has been found to exert an impact on processing speed and executive functioning. One critical issue that remains unclear is at what point in the lifespan self-reported lifestyle factors impact cognition. Method A community sample of nondepressed adults aged 18–74 (N = 176) was administered measures assessing activity engagement (Cognitive Health Questionnaire), processing speed (SDMT), and executive functioning (PASAT, Oral Trails B). Very physically and intellectually active (over 3 instances/week of activity) participants were compared to those reporting less activity across three age ranges: young adults (YA; age 18–29), middle-aged adults (MA; age 30–55), and older adults (OA; age 56–74). Results MA participants who frequently engaged in moderate or vigorous physical activity showed better SDMT performance than less active participants (p < .05). YA participants frequently engaging in mild physical activity showed a nonsignificant trend toward better PASAT and SDMT performance than those who were less active. YA and MA participants who reported high use of daily cognitive strategies showed stronger Oral Trails B (p < .05) and SDMT (p = .06) performance, respectively. Very intellectually active YA participants showed better PASAT performance than less active participants (p = .06). While OA participant group comparisons were not significant, small sample sizes for some analyses may have impacted results. Conclusions We found that individuals with strong lifestyle activity engagement showed better processing speed and executive functioning than less active participants. These findings are consistent with previous research indicating that more robust activity engagement is associated with better cognition.

F148. tDCS-enhanced working memory training in subjective cognitive decline

Introduction Subjective cognitive decline (SCD) is defined as worsening of cognitive abilities, although examination fails to reveal objective evidence of this decline. SCD is increasingly acknowledged as a risk factor for the development of Alzheimer’s disease and is therefore considered a stage particularly accessible for interventional strategies. However, studies evaluating the efficacy of therapeutic interventions in this condition are scarce. Of note, SCD has been particularly linked with deficient cognitive control (CC) functions. Anodal transcranial direct current stimulation (tDCS) to the left dorsolateral prefrontal cortex (dlPFC) can significantly enhance CC. Specifically, this has been demonstrated by means of a challenging and frustrating continuous performance task (Paced Auditory Serial Addition Task; PASAT). This randomized, sham-controlled study aims at providing evidence for the efficacy of a tDCS-enhanced CC training (PASAT) in participants with SCD. Methods 30 subjects with SCD (age > 60 years) participated in a four weeks training (12 sessions). Half of them received 2 mA anodal tDCS for 20 min applied to the left dlPFC, a major hub of the cognitive control network; the other half received sham stimulation. Eligibility criteria were examined by means of neuropsychological tests (CERAD-Plus, M.I.N.I.). The amount of concerns regarding memory impairment, which was quantified by means of a 10-point Likert scale, was obtained before and after the tDCS-enhanced training (pre- and post-session) and served as the primary outcome measure. Event-related potentials were measured with EEG as neurophysiological signatures of cognitive control. Near and far transfer were assessed by a Verbal 2-back Task and the Trail Making Test A & B. Together with changes of PASAT performance these measures were obtained before and after the tDCS-enhanced training. A follow-up session was conducted 3 months after end of training to control the sustainability of the training effects. Results A one-way repeated measures ANOVA showed that, compared to sham stimulation, anodal tDCS during PASAT training significantly reduced the amount of concerns regarding memory impairment ( F (1, 28) = 6.48, p = 0.017, η p 2 = 0.18). This effect was maintained at follow-up ( F (1, 28) = 4.33, p = 0.047, η p 2 = 0.13). Performance in the PASAT task was improved by training (t(324) = 8.84, p Conclusion In summary, the current study suggests that anodal tDCS-enhanced Cognitive Control Training in subjects with SCD results in reduction in the amount of worries regarding memory impairment, which persists for up to 3 months. This proof of concept could provide a basis for potential interventional approaches in SCD. Further studies are needed to replicate these results on a larger scale.

Factor Structure and Construct Validity of the Behavioral Dyscontrol Scale-II

The Behavioral Dyscontrol Scale-II (BDS-II) was developed as an improved scoring method to the original BDS, which was designed to evaluate the capacity for independent regulation of behavior and attention. The purpose of this study was to evaluate the factor structure and construct validity of the BDS-II, which had not been adequately re-examined since the development of the new scoring system. In a sample of 164 Veterans with a mean age of 35 years, exploratory factor analysis was used to evaluate BDS-II latent factor structure. Correlations and regressions were used to explore validity against 22 psychometrically sound neurocognitive measures across seven neurocognitive domains of sensation, motor output, processing speed, attention, visual-spatial reasoning, memory, and executive functions. Factor analysis found a two-factor solution for this sample which explained 41% of the variance in the model. Validity analyses found significant correlations among the BDS-II scores and all other cognitive domains except sensation and language (which was not evaluated). Hierarchical regressions revealed that PASAT performance was strongly associated with all three BDS-II scores; dominant hand Finger Tapping Test was also associated with the Total score and Factor 1, and CPT-II Commissions was also associated with Factor 2. These results suggest the BDS-II is both a general test of cerebral functioning, and a more specific test of working memory, motor output, and impulsivity. The BDS-II may therefore show utility with younger populations for measuring frontal lobe abilities and might be very sensitive to neurological injury.

Contribution of cortical and white matter lesions to cognitive impairment in multiple sclerosis

Background: Cortical lesions (CLs) have been reported to be a better predictor for cognitive impairment than white matter (WM) lesions in relapsing–remitting multiple sclerosis (RRMS). Objectives: The objectives of this article are to investigate the contribution of CLs and WM lesions to cognitive impairment in 91 patients with MS and clinically isolated syndrome, and to test potential associations of CLs and WM lesions with fatigue and depression. Methods: Lesions were scored and segmented on 3D double inversion recovery sequences, according to their location (cortical, WM). Normalised grey matter volume was also determined. Cognitive performance was assessed with the SDMT and PASAT-3, fatigue with the FSMC and depression with the German version of the CES-D. Results: CL volume did not correlate with fatigue or depression, but correlated significantly with both neuropsychological outcome measures: PASAT-3 (r = −0.275, p = 0.009) and SDMT (r = −0.377, p < 0.001). Multiple regression analyses with age, WM lesions, CLs and GM volume as independent variables, however, did not reveal CL volume as a significant predictor of neuropsychological outcomes, whereas WM lesion volume significantly predicted SDMT and by trend PASAT performance. Conclusions: These findings suggest a role of WM lesions in the development of cognitive deficits, especially information-processing speed, which may be higher than previously assumed. Abbreviations: CES-D: Center for Epidemiologic Studies Depression scale (ADS-L: Allgemeine Depressions Skala-L, German version of CES-D), CIS: clinically isolated syndrome, CL: cortical lesion, DIR: double inversion recovery, EDSS: Expanded Disability Status Scale, FSMC: fatigue scale for motor and cognitive functions, GM: grey matter, MRI: magnetic resonance imaging, MS: multiple sclerosis, PASAT-3: paced auditory serial addition test 3s, PPMS: primary progressive multiple sclerosis, RRMS: relapsing–remitting multiple sclerosis, SDMT: symbol digit modalities test, SPM: statistical parametric mapping, SPMS: secondary progressive multiple sclerosis, WM: white matter

Cognitive rehabilitation correlates with the functional connectivity of the anterior cingulate cortex in patients with multiple sclerosis

We investigated how resting state (RS) functional connectivity (FC) of the anterior cingulate cortex (ACC) correlates with cognitive rehabilitation in relapsing remitting multiple sclerosis (RRMS) patients. A neuropsychological assessment and RS fMRI at baseline and after 12weeks were obtained from 20 RRMS patients, who were assigned randomly to undergo treatment (n = 10) (treatment group-TG), which entailed computer-assisted cognitive rehabilitation of attention/information processing and executive functions for 3days/week, or not to receive any cognitive rehabilitation (n = 10) (control group-CG). Voxel-wise changes of ACC RS FC were assessed using SPM8. In both groups, at the two study time points, ACC activity was correlated with the bilateral middle and inferior frontal gyrus, basal ganglia, posterior cingulate cortex, cerebellum, precuneus, middle temporal gyrus, and inferior parietal lobule (IPL). At follow up, compared to baseline, the TG showed an increased FC of the ACC with the right middle frontal gyrus (MFG) and right IPL, while the CG showed a decreased FC of the ACC with the right cerebellum and right inferior temporal gyrus (ITG). A significant "treatment × time" interaction was found for the increased FC of the right IPL and for the decreased FC of the right ITG. In the TG only, significant correlations (p < 0.001) were found between improvement of PASAT performance and RS FC of the ACC with the right MFG (r = 0.88) and right IPL (r = 0.76). In MS, cognitive rehabilitation correlates with changes in RS FC of brain regions subserving the trained functions. fMRI might be useful to monitor rehabilitative strategies in MS.

Change in PASAT performance correlates with change in P3 ERP amplitude over a 12-month period in multiple sclerosis patients

Objective To examine the correlation between the change in PASAT and the change in P3 event-related potentials (ERPs) over a 12-month period in multiple sclerosis (MS) patients, and to compare the 12-month change in the P3 ERP between MS patients and controls. Methods Forty-four subjects (27 MS patients, 17 controls) completed visual and auditory two-stimulus oddball and three-stimulus oddball tasks at Month 0 and Month 12. Data were recorded from a 128-scalp channel electroencephalography array. Data from scalp channels were converted into continuous interpolated images (incorporating the entire scalp and time). Amplitude, topographical differences and correlations were then tested using statistical parametric mapping. Results The change in visual and auditory P3a correlated significantly with the change in PASAT score (r = 0.56, p < 0.001 and r = 0.48, p = 0.003, respectively). Visual P3b and P3a showed greater decrease in 12 months in MS patients relative to controls. Visual P3b, auditory P3b and auditory P3a amplitudes had significantly decreased in MS patients after 12-month period. Conclusions Change in visual and auditory P3a ERP amplitudes correlate with change in PASAT scores in MS patients. Visual modality is more sensitive to changes in P3 ERP amplitudes over 12-month period. Significance P3 ERPs may have utility in monitoring the change in cognitive functioning in MS.

Study of Neurobehavioral Symptoms and Impairments in Breast Cancer Patients Receiving Adjuvant Aromatase Inhibitor Therapy.

Abstract Background: Whether treatment with aromatase inhibitors (AI) may be associated with the development of cognitive or other mental impairments is under debate. Few studies have carefully assessed AI-associated changes in cognitive function, and none have assessed differences between the three third-generation AIs – anastrozole, letrozole, and exemestane. We initiated a prospective clinical trial to compare baseline and 1-year change in neurophysiological testing in women initiating adjuvant AI.Patients and Methods: Women with a hormone receptor-positive stage 0-III breast cancer who were about to begin AI treatment were eligible for enrollment. We compared intra-individual neurophysiological testing results at baseline (Session I) and following one year of AI (Session II). Cognitive/behavioral assessment included standardized tests sensitive to 8 neuropsychological domains: General Intelligence, Attention, Perceptual-motor Performance, Working Memory, Visual Long-term Memory, Verbal Long-term Memory, Language, and Executive Functioning. Scoring was based upon age- and education-adjusted normative data. In addition, participants completed several subjective reports of cognitive, physical, and emotional functioning.Results: To date, 53 subjects enrolled in Session I, and 30 completed Session II. Analysis of the 30 women who completed both sessions revealed statistically significant differences (with the significance level set at p=0.05, test-wise), including: impairment from Session I to Session II on the PASAT Trial I (p=0.005) and improvement from Session I to Session II on the following tests: FAS Total (p&amp;lt;0.001); Animal Naming (p=0.025); RAVLT I-V, B, Delay, and Immediate (p&amp;lt;0.001 for all); RAVLT 5-1 (p=0.017); RAVLT % (p=0.022); Logical Memory I (p=0.005) and II (p&amp;lt;0.001); WMS-Faces I &amp; II (p&amp;lt;0.001 for both); WAIS-Picture Completion (p=0.027); and WAIS-Vocabulary (p&amp;lt;0.001).Discussion: Only a few studies have examined the effect of AI treatment on cognitive functioning. Findings from the present study suggest that, following the administration of AI for 1 year, women as a group appear to exhibit impairments in attention (as evidenced by PASAT performance) and possibly in executive functioning. However, there was also improved performance in the areas of language, verbal long-term memory, and visual long-term memory. These preliminary results suggest a need to be sensitive to the possibility that AI treatment may have mixed effects on cognitive and related behavioral functions. Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 4084.

Differential SPECT Activation Patterns Associated with PASAT Performance May Indicate Frontocerebellar Functional Dissociation in Chronic Mild Traumatic Brain Injury

Patients with mild traumatic brain injury (TBI) often complain of cognitive fatigue during the chronic recovery phase. The Paced Auditory Serial Addition Test (PASAT) is a complex psychologic measure that may demonstrate subtle deficiencies in higher cognitive functions. The purpose of this study was to investigate the brain activation of regional cerebral blood flow (rCBF) with PASAT in patients with mild TBI to explore mechanisms for the cognitive fatigue. Two groups consisting of 15 patients with mild TBI and 15 healthy control subjects underwent (99m)Tc-ethylene cysteine dimer SPECT at rest and during PASAT on a separate day. Cortical rCBF was extracted using a 3-dimensional stereotactic surface projection and statistically analyzed to identify areas of activation, which were compared with PASAT performance scores. Image analysis demonstrated a difference in the pattern of activation between patients with mild TBI and healthy control subjects. Healthy control subjects activated the superior temporal cortex (Brodmann area [BA] 22) bilaterally, the precentral gyrus (BA 9) on the left, and the precentral gyrus (BA 6) and cerebellum bilaterally. Patients with mild TBI demonstrated a larger area of supratentorial activation (BAs 9, 10, 13, and 46) but a smaller area of activation in the cerebellum, indicating frontocerebellar dissociation. Patients with mild TBI and cognitive fatigue demonstrated a different pattern of activation during PASAT. Frontocerebellar dissociation may explain cognitive impairment and cognitive fatigue in the chronic recovery phase of mild traumatic brain injury.

Distinct mechanisms of altered brain activation in patients with multiple sclerosis

Cerebral reorganization may limit the effects of central nervous system tissue damage on cognition in patients with multiple sclerosis (MS). This study investigated fMRI activation patterns in patients with relapsing-remitting MS and healthy control subjects during performance of a delayed recognition task. As intended, fMRI task performance was similar in the MS and the control group, whereas neuropsychological testing revealed reduced performance in the patient group on the Paced Serial Addition Test, a reference task for the assessment of cognitive function in MS. Patients overall showed more activation in left posterior parietal cortex than healthy control subjects.Global gray matter atrophy in the patient group was associated with low PASAT scores. In a multiple regression analysis including white matter lesion load and gray matter atrophy as covariates, PASAT performance correlated with activation in left posterior parietal cortex and right anterior midfrontal gyrus, indicating a reallocation of neuronal resources to help preserve function. Global gray matter atrophy correlated with activation in bilateral prefrontal cortex, dorsal ACC and left posterior parietal cortex and, furthermore, was associated with a low degree of deactivation in rostral ACC, suggesting neural inefficiency and consistent with a reduced capacity to modulate between frontoparietal task-associated activation and ‘default network’ activity. The current study provides evidence that altered brain activation in MS patients has two distinct components, one related to compensatory processes and one to neural inefficiency associated with tissue damage.

PASAT in Detecting Cognitive Impairment in Relapsing-Remitting MS

The PASAT, as a part of the Multiple Sclerosis Functional Composite, is used as a sole measure of cognition in multiple sclerosis (MS) clinical trials. In the present study, we evaluated the frequency and characteristics of cognitive impairment among relapsing-remitting MS patients. Using a comprehensive neuropsychological examination as the “golden standard,” we assessed PASAT's sensitivity and specificity in MS-related cognitive impairment as well as factors possibly confounding PASAT performance. Forty-five relapsing-remitting MS patients and 48 healthy controls were studied using PASAT and a comprehensive neuropsychological examination. The frequency of cognitive dysfunction among MS patients was 42%. Cognitive impairment in MS was heterogeneous in nature but characterized, especially, by reduced information-processing ability and memory deficits. PASAT's sensitivity for patients' cognitive impairment was 74% and specificity 65%. Misclassification of cognitive impairment seemed to be associated with self-reported nervousness and poor arithmetic skills. Although PASAT offers satisfactory sensitivity in detecting the presence of cognitive impairment, its specificity may be limited by confounding factors.

Localized grey matter damage in early primary progressive multiple sclerosis contributes to disability

Disability in primary progressive multiple sclerosis (PPMS) has been correlated with damage to the normal appearing brain tissues. Magnetization transfer ratio (MTR) and volume changes indicate that much of this damage occurs in the normal appearing grey matter, but the clinical significance of this remains uncertain. We aimed to localize these changes to distinct grey matter regions, and investigate the clinical impact of the MTR changes. 46 patients with early PPMS and 23 controls underwent MT and high-resolution T1-weighted imaging. Patients were scored on the Expanded Disability Status Scale (EDSS), Multiple Sclerosis Functional Composite and subtests (Nine-Hole Peg Test, Timed Walk Test, Paced Auditory Serial Addition Test [PASAT]). Grey matter volume and MTR were compared between patients and controls, adjusting for age. Mean MTR for significant regions within the motor network and in areas relevant to PASAT performance were correlated with appropriate clinical scores, adjusting for grey matter volume. Patients showed reduced MTR and atrophy in the right pre- and left post-central gyri, right middle frontal gyrus, left insula, and thalamus bilaterally. Reduced MTR without significant atrophy occurred in the left pre-central gyrus, left superior frontal gyri, bilateral superior temporal gyri, right insula and visual cortex. Higher EDSS correlated with lower MTR in the right primary motor cortex (BA 4). In conclusion, localized grey matter damage occurs in early PPMS, and MTR change is more widespread than atrophy. Damage demonstrated by reduced MTR is clinically eloquent.

Short‐term effects of aerobic exercise on executive processes and emotional reactivity

The effect of individual bouts of aerobic exercise on young adults’ performance of an executive processing task (The Paced Auditory Serial Addition Test, PASAT) and on ratings of emotion and workload (NASA‐Task Load Index, TLX) was assessed in two experiments. In Experiment 1, nine men completed two test sessions during which the PASAT and the TLX were administered prior to and following a 40‐minute bout of cycling. A cold medication (Phenergan VC) was administered prior to exercise in one session; a placebo was given in the other session. PASAT performance increased following exercise, both after the ingestion of the cold medication and following the placebo. TLX ratings changed with practice but were not influenced by exercise. In Experiment 2, 10 women performed the PASAT and provided TLX ratings prior to and following four 120‐minute sessions of cycling and a control session. Participants were given one of three carbohydrate electrolyte drinks or a placebo drink prior to, during, and following cycling. PASAT performance improved significantly following exercise regardless of the type of drink ingested. Exercise did not influence TLX ratings. The results of these experiments add to a growing literature that demonstrates the facilitative effects of acute aerobic exercise on working memory and attentional processes.

Concurrent Validity of the PASAT and Adjusting-PSAT in Patients with Multiple Sclerosis

Impaired information processing speed (IPS) is common in multiple sclerosis (MS). Performance on the Paced Auditory Serial Addition Test (PSAT)—the measure recommended by the United States National MS Society Task Force to track changes in IPS—does not indicate the precise speed at which IPS breaks down. A newer version of the task, the Adjusted Paced Serial Addition Test (A-PSAT), provides such an index. This study examined the relationship between PASAT and A-PSAT performance in a sample of 52 individuals with MS. Those with relapsing-remitting MS (RRMS) were significantly younger and had significantly lower EDSS scores than those with chronic progressive MS (CPMS). Though performance indicators for both the PASAT and A-PSAT were better for patients with RRMS, differences in performance between MS groups were not significant (P &amp;gt;.05). Results of comparisons between the A-PSAT and PASAT support concurrent validity of the A-PSAT. In addition, performance on the APSAT—but not the PASAT—was significantly related to functional status as measured by the EDSS. Although these findings need to be replicated, they indicate that the A-PSAT may be a viable alternative to the existing PASAT.

Information processing speed deficits may be better correlated with the extent of white matter sclerotic lesions in multiple sclerosis than previously suspected

Despite frequent use of the Paced Auditory Serial Addition Test (PASAT; Gronwall, 1977) for examining information processing speed (IPS) deficits in multiple sclerosis (MS), prior literature on the relationship between PASAT performance and severity of brain disease has been contradictory. In the present study, we found that PASAT performance is moderately well correlated with the total area of sclerotic brain lesions in MS patients only if a modified scoring method (mean "dyad" score; Snyder et al., 1993), but not the standard scoring method, is applied. We conclude that the PASAT remains a useful measure of IPS in MS, if a flaw in the typical scoring technique for this test is corrected. In our sample of 41 MS patients, for every one point decrease in mean dyad score, total lesion area increased by 364.08 mm2 on average, after controlling for age, sex, and education. IPS deficits are more severe for patients with greater brain disease, due to increased disruption of the white matter pathways that likely support the parallel distributed processing of complex information by geographically distant brain regions.

The Effects of Fatigue on Neuropsychological Performance in Patients With Chronic Fatigue Syndrome, Multiple Sclerosis, and Depression

The effects of fatigue on neuropsychological performance were examined in patients with fatiguing illnesses. Repeated testing with the Paced Auditory Serial Addition Test (PASAT; Gronwall, 1977) was employed over the course of a demanding neuropsychological testing session. It was hypothesized that if fatigue affects performance, one would expect to observe "blunting" of the PASAT practice effect. Fifteen of the study participants live with chronic fatigue syndrome (CFS), 15 with multiple sclerosis (MS), 14 with depression (DEP), and 15 are healthy, sedentary controls. Overall PASAT performance was significantly reduced for CFS and DEP participants compared to controls, whereas mean performance did not differ across the three fatiguing illness groups. Degree of improvement across trials (i.e., practice effect) for the groups did not differ from controls'. Neither subjective fatigue or DEP were significantly related to PASAT performance. These findings suggest that fatigue does not universally impair performance during neuropsychological assessment even in groups in which fatigue is a prominent symptom.

Validity of the paced auditory serial addition test (pasat) in adults referred for neuropsychological assessment after head injury

The goal of this study was to evaluate the construct and criterion-related validity of the PASAT in 441 adults referred for evaluation of possible closed-head injury (mean age of 32.7 years, SD = 12.4). Convergent evidence for the construct validity of the PASAT as an attention test was stronger than divergent evidence. Although the PASAT correlated with several measures of attention, tests tapping mathematical knowledge accounted for a substantial amount of variance in PASAT scores. Further, other tests measuring conceptually unrelated abilities, such as verbal ability, academic achievement, verbal memory, and complex motor skills were also moderately correlated with PASAT performance. The slower PASAT presentation rate was also related to one test of visual memory and to one test of visual-spatial ability. These results suggest that PASAT performance is related to several cognitive abilities other than attention and processing speed. PASAT scores were not related to criterion-related indices of head injury severity. Limitations regarding construct validity are discussed, as are preliminary clinical guidelines for interpretation of the PASAT.

Which abilities does the PASAT test?

The relationships between PASAT test scores and intelligence, memory and information processing abilities were examined in ninety-four healthy young adult patients with type 1 (insulin-dependent) diabetes. PASAT scores correlated significantly with all WAIS-R subtests. Factor analysis revealed that PASAT performance loaded on the 1st principal component (the ‘general intelligence’ factor) at about the same level as some WAIS-R performance subtests. Varimax rotation showed that PASAT scores had very low loadings on verbal and performance factors, but had high loadings on the third rotated factor, which was tentatively identified as the ‘freedom from distraction’ factor found in recent factor analyses of the WAIS-R. Scores from the 4 second PASAT presentation correlated better than 2 second PASAT scores with indices derived from the Rey auditory verbal learning test, whereas the faster PASAT test correlated at higher levels with test of Inspection Time and Reaction Time. The PASAT test was developed to measure attention and concentration but, while this appears to have been realised to some extent, general intellectual ability is also tapped by the test. Different speeds of presentation might index other abilities to different degrees, but this finding might be explained by order effects which cannot be excluded by the present study.