Within-Person Test Score Distributions: How Typical Is "Normal"?

We evaluated within-person variability across a cognitive test battery by analyzing the shape of the distribution of each individual's scores within a battery of tests. We hypothesized that most healthy adults would produce test scores that are normally distributed around their own personal battery-wide, within-person (wp) mean. Using cross-sectional data from 327 neurologically healthy adults, we computed each person's mean, standard deviation, skew, and kurtosis for 30 neuropsychological measures. Raw scores were converted to T-scores using three degrees of calibration: (a) none, (b) age, and (c) age, sex, race, education, and estimated premorbid IQ. Regardless of calibration, no participant showed abnormal within-person skew (wpskew) and only 10 (3.1%) to 16 (4.9%) showed wpkurtosis greater than 2. If replicated in other samples and measures, these findings could illuminate how healthy individuals are endowed with different cognitive abilities and provide the foundation for a new method of inference in clinical neuropsychology.

Embedded performance validity tests within the Hopkins Verbal Learning Test - Revised and the Brief Visuospatial Memory Test - Revised.

OBJECTIVE: Various research studies and neuropsychology practice organizations have reiterated the importance of developing embedded performance validity tests (PVTs) to detect potentially invalid neurocognitive test data. This study investigated whether measures within the Hopkins Verbal Learning Test - Revised (HVLT-R) and the Brief Visuospatial Memory Test - Revised (BVMT-R) could accurately classify individuals who fail two or more PVTs during routine clinical assessment. METHOD: The present sample of 109 United States military veterans (Mean age = 52.4, SD = 13.3), all consisted of clinically referred patients and received a battery of neuropsychological tests. Based on performance validity findings, veterans were assigned to valid (n = 86) or invalid (n = 23) groups. Of the 109 patients in the overall sample, 77 were administered the HLVT-R and 75 were administered the BVMT-R, which were examined for classification accuracy. RESULTS: The HVLT-R Recognition Discrimination Index and the BVMT-R Retention Percentage showed good to adequate discrimination with an area under the curve of .78 and .70, respectively. The HVLT-R Recognition Discrimination Index showed sensitivity of .53 with specificity of .93. The BVMT-R Retention Percentage demonstrated sensitivity of .31 with specificity of .92. CONCLUSIONS: When used in conjunction with other PVTs, these new embedded PVTs may be effective in the detection of invalid test data, although they are not intended for use in patients with dementia.

Overlap between dissociation and other psychological characteristics in patients with psychogenic nonepileptic seizures.

Patients with psychogenic nonepileptic seizures (PNES) often report symptoms of dissociation. However, it is unclear how these symptoms relate to psychotherapeutic treatment, for example, with cognitive-behavioral therapy (CBT). Here, we investigated the degree of overlap between symptoms of dissociation and other psychiatric features that are more traditional targets for CBT. We used a hierarchical linear regression to measure the variance associated with dissociative symptoms (as assessed by the Dissociative Experiences Scale - DES) among 46 individuals with PNESs. The regression predictor variables are indices of participants' self-rated mood, self-efficacy, quality of life, locus of control, and life outlook (e.g., optimism). Results revealed that 70.2% of the variance associated with DES score was explained by psychological distress and locus of control. The other factors examined did not make a significant contribution to the regression model. These results suggest that traditional CBT targets - mood symptoms, mood distress, and dysfunctional beliefs about locus of control - overlap substantially with self-reported dissociative symptoms.

Stressful life event appraisal and coping in patients with psychogenic seizures and those with epilepsy.

Understanding stress and coping among individuals with psychogenic nonepileptic seizures (PNES) may have important treatment implications. 40 patients with PNES, 20 with epilepsy (EPIL), and 40 healthy control (HC) participants reported the frequency of various stressful life events (both positive and negative) and appraised the distress these events induced. They also described their habitual coping behaviors. PNES patients reported no more frequent stressful life events than EPIL patients or HC. In addition, the stressors they experienced are not objectively more severe. However, they reported more severe distress due to negative life events, especially in the domains of work, social functioning, legal matters, and health. PNES patients also engaged in less planning and active coping than HC. Neither of these two coping behaviors was associated with distress ratings. The PNES group did not engage in more denial than either group. However, greater denial among PNES patients was associated with greater perceived distress. Coping in PNES is characterized by elevated levels of perceived distress and fewer action strategies than are normally employed to reduce the impact of a stressor. These findings may inform cognitive behavioral therapy of PNES patients.

Personality Assessment Inventory among patients with psychogenic seizures and those with epilepsy.

The Personality Assessment Inventory (PAI) is a widely used self-report questionnaire designed to detect and quantify dimensions of adult psychopathology. Previous studies that examined the ability of the PAI to differentiate between patients with psychogenic nonepileptic seizures (PNES) and those with epilepsy (EPIL) have yielded inconsistent results. We compared the full PAI profiles of 62 patients with PNES, 55 with EPIL, and 45 normal control (NC) participants to determine the diagnostic accuracy of the PAI. We also sought to highlight psychopathologic symptoms that may inform psychological treatment of patients with PNES or epilepsy. PNES and EPIL patients reported more somatic concerns and symptoms of anxiety and depression than did NC persons. PNES patients reported more unusual somatic symptoms, as well as greater physical symptoms of anxiety and depression than did patients with EPIL. Classification accuracy of the "NES Indicator" was not much better than chance, whereas the Conversion subscale alone had reasonable sensitivity (74%) and specificity (67%). Overall, the PAI demonstrated only moderate classification accuracy in an epilepsy monitoring unit sample. However, the inventory appears to identify specific psychopathological symptoms that may be targets of psychological/psychiatric intervention.

Do patients with psychogenic nonepileptic seizures have positive covert attitudes toward sickness?

Some individuals with psychogenic nonepileptic seizures (PNES) are seen as having adopted a "sick role" that relinquishes them of responsibility for meeting stressful life demands. Thus, patients with PNES may have positive, albeit unrecognized, attitudes toward seizures, or perhaps illness in general. Because such covert attitudes may not be amendable to self-report, the current study used the Implicit Association Test (IAT), a methodology by which attitudes toward illness and disability can be inferred from performance on an ostensibly neutral task. Individuals with PNES did not have a reduced interference effect when responding to sickness-related and pleasant words on the same response key. Exploratory analyses revealed that a pronounced somatic focus and higher extraversion were associated with more neutral attitudes toward illness among patients with PNES. This IAT methodology found little support for the notion that patients with PNES harbor positive attitudes toward illness. Limitations of the IAT methodology are reviewed and recommendations are provided.

The utility of regression-based norms in interpreting the minimal assessment of cognitive function in multiple sclerosis (MACFIMS).

The Minimal Assessment of Cognitive Function in Multiple Sclerosis (MACFIMS) is a consensus neuropsychological battery with established reliability and validity. One of the difficulties in implementing the MACFIMS in clinical settings is the reliance on manualized norms from disparate sources. In this study, we derived regression-based norms for the MACFIMS, using a unique data set to control for standard demographic variables (i.e., age, age2, sex, education). Multiple sclerosis (MS) patients (n = 395) and healthy volunteers (n = 100) did not differ in age, level of education, sex, or race. Multiple regression analyses were conducted on the performance of the healthy adults, and the resulting models were used to predict MS performance on the MACFIMS battery. This regression-based approach identified higher rates of impairment than manualized norms for many of the MACFIMS measures. These findings suggest that there are advantages to developing new norms from a single sample using the regression-based approach. We conclude that the regression-based norms presented here provide a valid alternative to identifying cognitive impairment as measured by the MACFIMS.

Accounting for estimated IQ in neuropsychological test performance with regression-based techniques.

Regression-based normative techniques account for variability in test performance associated with multiple predictor variables and generate expected scores based on algebraic equations. Using this approach, we show that estimated IQ, based on oral word reading, accounts for 1-9% of the variability beyond that explained by individual differences in age, sex, race, and years of education for most cognitive measures. These results confirm that adding estimated "premorbid" IQ to demographic predictors in multiple regression models can incrementally improve the accuracy with which regression-based norms (RBNs) benchmark expected neuropsychological test performance in healthy adults. It remains to be seen whether the incremental variance in test performance explained by estimated "premorbid" IQ translates to improved diagnostic accuracy in patient samples. We describe these methods, and illustrate the step-by-step application of RBNs with two cases. We also discuss the rationale, assumptions, and caveats of this approach. More broadly, we note that adjusting test scores for age and other characteristics might actually decrease the accuracy with which test performance predicts absolute criteria, such as the ability to drive or live independently.

Development, psychometric properties, and validity of the hopkins adult reading test (HART).

We describe the development of a 35-item, oral word-reading test with two equivalent forms (HART-A and HART-B) designed to estimate premorbid abilities. Both forms show excellent internal consistency (coefficients alpha>.91) and test-retest reliability (Pearson rs >.90). HART performance was combined with demographic variables to generate regression equations that predict IQ scores obtained concurrently and 4-8 years earlier. The resulting models explained 61% of full scale IQ (FSIQ) variability in 327 healthy adults. The FSIQs that can be estimated range from below 73 to above 131. Combined with demographic variables, these two brief word reading tests accurately predict a broader range of IQs than Blair and Spreen's (1989) longer version. Equivalent forms make it especially useful for longitudinal studies.

Stimulus type affects Wada memory performance.

The effects of amytal injection side, seizure focus laterality, and stimulus type (real and line-drawn objects, printed words, and faces) on recognition memory were studied during the Wada procedure. To-be-remembered stimuli were presented during cerebral anesthesia to 35 patients with left temporal lobe epilepsy (LTLE) and 28 patients with right temporal lobe epilepsy (RTLE), all with left hemisphere language dominance. In both groups, recognition of real and line-drawn objects was best after anesthetization of the lesional hemisphere. Recognition of faces was poor after either injection in patients with RTLE, but only after right injection in patients with LTLE. Conversely, recognition of words by patients with LTLE was impaired equally after either injection, but more so after left than right injection in patients with RTLE. The findings suggest that (1) real and line-drawn objects are "dually encoded" and memory accuracy depends on seizure focus laterality, and (2) accuracy in recognition of words and faces is related to seizure focus laterality, but may also depend on the language dominance of the hemisphere being assessed.

Frequency and bases of abnormal performance by healthy adults on neuropsychological testing.

The frequency and determinants of abnormal test performance by normal individuals are critically important to clinical inference. Here we compare two approaches to predicting rates of abnormal test performance among healthy individuals with the rates actually shown by 327 neurologically normal adults aged 18-92 years. We counted how many participants produced abnormal scores, defined by three different cutoffs with test batteries of varied length, and the number of abnormal scores they produced. Observed rates generally were closer to predictions based on a series of Monte Carlo simulations than on the binomial model. They increased with the number of tests administered, decreased as more stringent cutoffs were used to identify abnormality, varied with the degree of correlation among test scores, and depended on individual differences in age, education, race, sex, and estimated premorbid IQ. Adjusting scores for demographic variables and premorbid IQ did not reduce rates of abnormal performance. However, it eliminated the contribution of these variables to rates of abnormal test performance. These findings raise fundamental questions about the nature and interpretation of abnormal test performance by normal, healthy adults.

Neuropsychological impairment in deficit vs. non-deficit schizophrenia.

This study aimed to assess the severity and specificity of cognitive impairments that affect individuals with deficit versus non-deficit schizophrenia. We compared 26 patients with the deficit subtype of schizophrenia (SZ-D) and 79 with non-deficit schizophrenia (SZ-ND) to 316 healthy adults (NC). All study participants completed a battery with 19 individual cognitive measures. After adjusting their test performance for age, sex, race, education and estimated premorbid IQ, we derived regression-based T-scores for each measure and the six derived cognitive domains including attention, psychomotor speed, executive function, verbal fluency, visual memory, and verbal memory. Multivariate analyses of variance revealed significant group effects for every individual measure and domain of cognitive functioning (all ps<0.001). Post hoc comparisons revealed that patients with SZ-D performed significantly worse than NCs in every cognitive domain. They also produced lower scores than the SZ-ND group in every domain, but only the difference for verbal fluency reached statistical significance. The correlations of the effect sizes shown by the SZ-D and SZ-ND patients were of intermediate magnitude for the individual tests (r=0.56, p<0.01) and higher, but not statistically significant for the cognitive domains (r=0.79, p=0.06). Patients with SZ-D demonstrate cognitive deficits that are both common and distinct from those shown by patients with SZ-ND. Their impairment of verbal fluency is consistent with the observation that poverty of speech is a clinically significant feature of patients with SZ-D.

Mood, personality, and health-related quality of life in epileptic and psychogenic seizure disorders.

PURPOSE: Patients with psychogenic nonepileptic seizures (PNES) rate their health-related quality of life (HRQOL) more poorly than those with epileptic seizures (ES). This has been explained in part by mood state. We sought to investigate whether HRQOL differences between diagnostic groups (PNES vs. ES) can be explained by additional, perhaps chronic, aspects of mood and personality. An understanding of these relationships may inform treatment designed to improve HRQOL in ES or PNES. METHODS: One-hundred fourteen individuals (69 ES and 45 PNES) completed the quality of life in Epilepsy-89. The profile of mood states (POMS) and the Minnesota Multiphasic Personality Inventory-2 (MMPI-2) were employed to measure current and chronic mood symptoms, respectively. Multiple regression analyses determined the contribution of chronic mood symptoms to HRQOL beyond the variance accounted for by current mood state and seizure diagnosis. RESULTS: Similar to previous reports, individuals with PNES reported poorer HRQOL than those with ES. Current mood state was strongly related to HRQOL and appeared to moderate the relationship between seizure diagnosis and HRQOL. However, when more chronic psychological symptoms, such as somatization and emotional distress, were included in a model, the moderating role of mood state was not significant. CONCLUSION: Analyzed independently, mood state is related to HRQOL, but when chronic indicators of psychological symptoms are included in a model mood is related to HRQOL, but, the moderating effect of mood is no longer significant. Treatments designed to improve HRQOL among individuals with intractable seizures should also address chronic psychological distress and symptoms associated with high levels of somatization.

Neuropsychological functioning in bipolar disorder and schizophrenia.

BACKGROUND: Some patients with bipolar disorder (BD) demonstrate neuropsychological deficits even when stable. However, it remains unclear whether these differ qualitatively from those seen in schizophrenia (SZ). METHODS: We compared the nature and severity of cognitive deficits shown by 106 patients with SZ and 66 patients with BD to 316 healthy adults (NC). All participants completed a cognitive battery with 19 individual measures. After adjusting their test performance for age, sex, race, education, and estimated premorbid IQ, we derived regression-based T-scores for each measure and the six cognitive domains. RESULTS: Both patient groups performed significantly worse than NCs on most (BD) or all (SZ) cognitive tests and domains. The resulting effect sizes ranged from .37 to 1.32 (mean=.97) across tests for SZ patients and from .23 to .87 (mean=.59) for BD patients. The Pearson correlation of these effect sizes was .71 (p<.001). CONCLUSIONS: Patients with bipolar disorder suffer from cognitive deficits that are milder but qualitatively similar to those of patients with schizophrenia. These findings support the notion that schizophrenia and bipolar disorder show greater phenotypic similarity in terms of the nature than severity of their neuropsychological deficits.

Neurocognitive sequelae of a giant arachnoid cyst: case study.

We conducted a comprehensive neuropsychological evaluation of a normally functioning man with a giant arachnoid cyst encompassing much of the space normally occupied by the left hemisphere. Although of solidly average intellectual ability, the patient demonstrated neurocognitive deficits only revealed upon neuropsychological assessment. Despite the remarkable left hemisphere lesion, the pattern of cognitive dysfunction suggested right hemisphere pathology. We review the arachnoid cyst literature and discuss the possibility of a crowding phenomenon by which language function relocates to the more viable hemisphere. This case illustrates striking preservation of higher cognition in the presence of substantial structural abnormality.

Accuracy of self-reported neuropsychological functioning in individuals with epileptic or psychogenic nonepileptic seizures.

The aim of this study was to determine the degree to which subjective ratings of neurocognitive ability accurately reflect objectively measured neuropsychological functioning in patients diagnosed with epileptic (ES, n = 45) or psychogenic nonepileptic (PNES; n = 37) seizures. Patients received a battery of neuropsychological tests, measures of current mood state, and the Quality of Life In Epilepsy-89 questionnaire. Results indicated that subjective ratings of neuropsychological functioning were only partially accurate within each group. Patients with ES accurately rated their memory function, but overestimated language and attention abilities. Patients with PNES accurately rated attention, but underestimated memory and overestimated language. In both groups, poorer self-reported neurocognitive functioning was strongly related to poorer mood state; however, mood state did not predict objectively measured neurocognitive abilities. Given the inaccuracies that exist in patient self-report, results highlight the importance of a comprehensive neuropsychological assessment when evaluating the neurocognitive status of individuals with seizures.

Warrington's recognition memory for faces: interpretive strategy and diagnostic utility in temporal lobe epilepsy.

Performance on Warrington's Recognition Memory Test for Faces (RMF) is thought to rely largely on the integrity of the right temporal lobe. Epilepsy research, however, has been mixed with respect to the diagnostic utility of the RMF. Based on the psychometric properties of the RMF, we investigated the moderating role of intelligence on test classification accuracy in 53 presurgical patients with temporal lobe epilepsy. Classification accuracy rates were poor for the entire sample, but when the sample was divided based on IQ, classification statistics showed a strong degree of diagnostic utility for the RMF among patients with lower IQ levels versus those with higher IQ levels. These findings support the diagnostic utility of the RMF in epilepsy and underscore the moderating role of intelligence on RMF performance.

Preoperative assessment of confrontation naming ability and interictal paraphasia production in unilateral temporal lobe epilepsy.

The present study examined the diagnostic utility of confrontation naming tasks and phonemic paraphasia production in lateralizing the epileptogenic region in patients with temporal lobe epilepsy (TLE). Further, the role of intelligence in moderating the diagnostic utility of confrontation naming tasks was assessed. Eighty patients with medically intractable complex partial seizures (40 left TLE, 40 right TLE) received the Boston Naming Test (BNT) and the Visual Naming subtest (VNT) of the Multilingual Aphasia Examination. The BNT was diagnostically more sensitive than the VNT in identifying left TLE (77.5% vs 17.5%, respectively). The utility of BNT performance and paraphasias was maximal in patients with Full Scale IQs >or=90 who were 6.8 times more likely to have left TLE than patients without paraphasias. Preoperative assessment of confrontation naming ability and phonemic paraphasia production using the BNT provided diagnostically useful information in lateralizing the epileptogenic region in left TLE.

What does the family pictures subtest of the Wechsler Memory Scale-III measure? Insight gained from patients evaluated for epilepsy surgery.

The Family Pictures (FP) task is a new subtest of the Wechsler Memory Scale Version III (WMS-III) used to assess visual memory and learning. This study assessed the extent to which different cognitive abilities contribute to performance on the FP task in 125 patients evaluated for epilepsy surgery. Results indicated that the FP task relies heavily on auditory-verbal based cognitive abilities, as well as visual memory, and may better represent a general measure of memory performance. These results raise questions about the appropriateness of including FP task performance in the calculations of the WMS-III Visual Index scores.