Source recognition discriminability impairment in Huntington's versus Alzheimer's disease: Evidence from the CVLT-3.

Research suggests that individuals with Huntington's disease (HD) perform better than individuals with Alzheimer's disease (AD) on the California Verbal Learning Test (CVLT) Yes/No Recognition trial. However, those with HD have been shown to have deficits comparable to those with AD on the Source Recognition Discriminability (RD) index (which assesses the ability to distinguish between List A targets and List B distractors), suggesting that HD may involve selective impairment in aspects of yes/no recognition that rely on source memory. However, whether individuals with HD and AD show comparable deficits on Source RD across stages of dementia severity has not been adequately investigated. We examined performance on the CVLT-3 List A vs. List B RD index in individuals with HD or AD and mild or moderate dementia. Among individuals with mild dementia, scores were higher in the HD versus AD group, whereas among individuals with moderate dementia, scores were comparable between the HD and AD groups; this corresponded to differential performance across dementia stages among individuals with HD, but not AD. The present findings suggest that, relative to AD, HD may be associated with disproportionate decline in aspects of yes/no recognition that rely on source memory.

Revisiting total recognition discriminability in Huntington's and Alzheimer's disease: New insights from the CVLT-3.

The original and second editions of the California Verbal Learning Test (CVLT) used nonparametric and parametric methods, respectively, to assess Total Recognition Discriminability (RD). In a previous study, we found evidence that the nonparametric formula may be more sensitive than the parametric formula to high false positive (FP) rates and provide more accurate assessments of yes/no recognition in neurodegenerative populations prone to high FP rates, including Alzheimer's disease (AD). In the present study, we extended our investigation to examine the utility of CVLT-3 nonparametric and parametric Total RD indices in the assessment and comparison of yes/no recognition in individuals with Huntington's disease (HD) and AD in mild and moderate stages of dementia. Findings suggested that the CVLT-3 nonparametric Total RD index was more sensitive than the parametric index to HD and AD differences in yes/no recognition across mild and moderate stages of dementia. Additionally, group differences on total FP errors were more closely mirrored by group differences on the nonparametric Total RD index. The present results bolster our previous findings and highlight the utility of examining nonparametric (in addition to parametric) Total RD on the CVLT-3 in assessments of yes/no recognition involving clinical populations prone to high FP rates.

Cohort differences on the CVLT-II and CVLT3: Evidence of a negative Flynn effect on the attention/working memory and learning trials.

OBJECTIVE: Although cohort effects on IQ measures have been investigated extensively, studies exploring cohort differences on verbal memory tests, and the extent to which they are influenced by socioenvironmental changes across decades (e.g. educational attainment; ethnic makeup), have been limited. METHOD: We examined differences in performance between the normative samples of the CVLT-II from 1999 and the CVLT3 from 2016 to 2017 on the immediate- and delayed-recall trials, and we explored the degree to which verbal learning and memory skills might be influenced by the cohort year in which norms were collected versus demographic factors (e.g. education level). RESULTS: Multivariate analysis of variance tests and follow-up univariate tests yielded evidence for a negative cohort effect (also referred to as negative Flynn effect) on performance, controlling for demographic factors (p = .001). In particular, findings revealed evidence of a negative Flynn effect on the attention/working memory and learning trials (Trial 1, Trial 2, Trial 3, Trials 1-5 Total, List B; ps < .007), with no significant cohort differences found on the delayed-recall trials. As expected, education level, age group, and ethnicity were significant predictors of CVLT performance (ps < .01). Importantly, however, there were no interactions between cohort year of norms collection and education level, age group, or ethnicity on performance. CONCLUSIONS: The clinical implications of the present findings for using word list learning and memory tests like the CVLT, and the potential role of socioenvironmental factors on the observed negative Flynn effect on the attention/working memory and learning trials, are discussed.

Identification of Subtle Verbal Memory Deficits in Premanifest Huntington Disease Using the California Verbal Learning Test.

BACKGROUND: Verbal memory impairment in individuals with Huntington disease (HD) is well-documented; however, the nature and extent of verbal memory impairment in individuals with premanifest HD (pre-HD) are less understood. OBJECTIVE: To evaluate verbal memory function in individuals with pre-HD by comparing their performance on the California Verbal Learning Test to that of individuals with a clinical diagnosis of HD and that of a demographically similar group of adults with no family history of, or genetic risk for, HD, thereby reducing possible complications of psychiatric difficulties commonly experienced by individuals who are at risk for HD but are gene negative. METHODS: Participant groups included 77 adults with a diagnosis of HD, 23 premanifest gene carriers for HD (pre-HD), and 54 demographically similar, healthy adults. The California Verbal Learning Test-Second Edition (CVLT-II) was used to evaluate the participants' immediate and delayed recall, recognition, learning characteristics, errors, and memory retention. RESULTS: The pre-HD group performed significantly worse than the healthy group, yet significantly better than the HD group, on Short and Long Delay Recall (Free and Cued) and Recognition Discriminability. On Total Immediate Recall, Learning Slope, Semantic Clustering, and Intrusions, the pre-HD group performed similarly to the healthy group and significantly better than the HD group. None of the groups differed in their performance on Repetitions and a measure of retention. CONCLUSIONS: Subtle memory deficits can be observed during the premanifest stage of HD with use of a subset of indices from the CVLT-II.

Utility of the D-KEFS Color Word Interference Test as an embedded measure of performance validity.

Objective: The D-KEFS Color Word Interference Test (CWIT) is among the most commonly administered measures of verbally mediated processing speed and executive functioning. Previous research suggests that this test may also be sensitive to performance invalidity. We sought to develop new embedded measures of performance invalidity based on multi-condition performance on the CWIT and to evaluate previously proposed embedded measures for performance invalidity on this test.Method: Newly developed and previously proposed embedded measures were evaluated in three samples: a traumatic brain injury (TBI) sample (N = 224) classified into psychometrically-defined performance-valid and performance-invalid subgroups; the D-KEFS normative sample (N = 1,735); and a Parkinson's disease sample (N = 166). To explore the resilience of CWIT cutoffs to the effects of age and neurocognitive impairment, the D-KEFS normative sample was stratified into age groups of 8-19, 20-69, and 70-89 and the Parkinson's disease sample into normal cognition, mild cognitive impairment, and dementia groups.Results: Our newly developed embedded measures derived from within the TBI sample were largely resilient to the effects of age and neurocognitive impairment other than dementia. Overall, a cutoff of ≤18 on the sum of age-corrected scaled scores on all four conditions exhibited the strongest classification accuracy. In contrast, previously proposed cutoffs (Erdodi et al., 2018) produced unacceptable false-positive rates within the TBI sample and generally a high rate of potential false positives in the normative age and clinical groups.Conclusion: Scoring ≤18 on the sum of all conditions on the CWIT appears to be an optimal cutoff for performance invalidity detection in non-demented samples.

The emergence of age-related changes in recognition memory in healthy middle-aged adults using the CVLT-II.

Although age-related memory differences between young and older adults have been well documented, fewer studies have investigated memory changes in middle age. We examined the performance of healthy middle-aged adults (40-55 years of age; n = 32) in relation to healthy young (18-25 years of age; n = 57) and older adults (65+ years of age; n = 55) on variations of recognition discriminability (RD) indices derived from the California Verbal Learning Test-Second Edition (CVLT-II). Middle-aged adults performed significantly worse (ps < .05) than young adults on multiple RD indices that incorporate semantically related distractor items, suggesting memory changes in middle age may be associated with increased susceptibility to semantic interference. Moreover, middle-aged adults performed comparably to older adults across all RD indices, indicating the recognition profile of middle-aged adults on RD indices more closely resembles that of older adults than young adults.

Recall and Recognition Discriminability in Parkinson's Disease and Huntington's Disease.

BACKGROUND: Parkinson's disease (PD) and Huntington's disease (HD) are two neurodegenerative diseases affecting frontal-striatal function and memory ability. Studies using the original California Verbal Learning Test (CVLT) to examine recall and recognition abilities between these groups have produced mixed findings. Some found that individuals with HD demonstrate worse recall and recognition than those with PD, whereas others reported comparable performance. OBJECTIVE: We utilized multiple indices of recall and recognition discriminability, provided by the second and third editions of the CVLT (CVLT-II and CVLT-3, respectively), that allow for a more thorough assessment of more nuanced aspects of verbal memory function. METHODS: We examined differences between individuals with PD (n = 72) and those with HD (n = 77) on CVLT-II indices of recall discriminability (immediate, short delay free and cued, long delay free and cued) and recognition discriminability (total, source, semantic, and novel) using standardized scores while controlling for education and Dementia Rating Scale-2 scores. RESULTS: The HD group performed significantly worse than the PD group on all measures of recall and recognition discriminability (ps < 0.05), and group differences were associated with large Cohen's d effect sizes. CONCLUSIONS: Our findings suggest that individuals with HD are more impaired than individuals with PD in more nuanced aspects of recall and recognition memory function. These CVLT indices yield more thorough assessments of recall and recognition memory function and have the potential to improve efforts to characterize and distinguish profiles of memory loss in different neurodegenerative populations, including PD and HD.

New Intrusion Analyses on the CVLT-3: Utility in Distinguishing the Memory Disorders of Alzheimer's versus Huntington's Disease.

OBJECTIVES: Research has shown that analyzing intrusion errors generated on verbal learning and memory measures is helpful for distinguishing between the memory disorders associated with Alzheimer's disease (AD) and other neurological disorders, including Huntington's disease (HD). Moreover, preliminary evidence suggests that certain clinical populations may be prone to exhibit different types of intrusion errors. METHODS: We examined the prevalence of two new California Verbal Learning Test-3 (CVLT-3) intrusion subtypes - across-trial novel intrusions and across/within trial repeated intrusions - in individuals with AD or HD. We hypothesized that the encoding/storage impairment associated with medial-temporal involvement in AD would result in a greater number of novel intrusions on the delayed recall trials of the CVLT-3, whereas the executive dysfunction associated with subcortical-frontal involvement in HD would result in a greater number of repeated intrusions across trials. RESULTS: The AD group generated significantly more across-trial novel intrusions than across/within trial repeated intrusions on the delayed cued-recall trials, whereas the HD group showed the opposite pattern on the delayed free-recall trials. CONCLUSIONS: These new intrusion subtypes, combined with traditional memory analyses (e.g., recall versus recognition performance), promise to enhance our ability to distinguish between the memory disorders associated with primarily medial-temporal versus subcortical-frontal involvement.

New Yes/No Recognition Memory Analysis on the California Verbal Learning Test-3: Clinical Utility in Alzheimer's and Huntington's Disease.

OBJECTIVES: The third edition of the California Verbal Learning Test (CVLT-3) includes a new index termed List A versus Novel/Unrelated recognition discriminability (RD) on the Yes/No Recognition trial. Whereas the Total RD index incorporates false positive (FP) errors associated with all distractors (including List B and semantically related items), the new List A versus Novel/Unrelated RD index incorporates only FP errors associated with novel, semantically unrelated distractors. Thus, in minimizing levels of source and semantic interference, the List A versus Novel/Unrelated RD index may yield purer assessments of yes/no recognition memory independent of vulnerability to source memory difficulties or semantic confusion, both of which are often seen in individuals with primarily frontal-system dysfunction (e.g., early Huntington's disease [HD]). METHODS: We compared the performance of individuals with Alzheimer's disease (AD) and HD in mild and moderate stages of dementia on CVLT-3 indices of Total RD and List A versus Novel/Unrelated RD. RESULTS: Although AD and HD subgroups exhibited deficits on both RD indices relative to healthy comparison groups, those with HD generally outperformed those with AD, and group differences were more robust on List A versus Novel/Unrelated RD than on Total RD. CONCLUSIONS: Our findings highlight the clinical utility of the new CVLT-3 List A versus Novel/Unrelated RD index, which (a) maximally assesses yes/no recognition memory independent of source and semantic interference; and (b) provides a greater differentiation between individuals whose memory disorder is primarily at the encoding/storage level (e.g., as in AD) versus at the retrieval level (e.g., as in early HD). (JINS, 2018, 24, 833-841).

Refining CVLT-II recognition discriminability indices to enhance the characterization of recognition memory changes in healthy aging.

The present study examined age-related differences on the four false-positive (FP) error subtypes found on the California Verbal Learning Test-Second Edition yes/no recognition memory trial and the influence of these subtypes on source and novel recognition discriminability (SoRD and NRD, respectively) index calculations. Healthy older (n = 55) adults generally made more FP errors than healthy young adults (n = 57). Accordingly, older adults performed worse than young adults on all SoRD and NRD indices. However, the manner in which FP error subtypes were incorporated into SoRD and NRD index calculations impacted the magnitudes of observed differences between and within the two age groups on SoRD and NRD indices. The present findings underline the importance of examining FP errors in assessments of recognition memory abilities, and using more refined indices of recognition discriminability to further elucidate the nature of age-related recognition memory impairment.

Effects of Age and Gender on Recall and Recognition Discriminability.

OBJECTIVE: Recall and recognition memory abilities are known to decline with increasing age, yet much of the evidence stems from studies that used simple measures of total target recall or recognition. The California Verbal Learning Test-Second Edition (CVLT-II) includes a new measure of recall discriminability that is analogous to recognition discriminability. These discriminability measures yield more thorough assessments of recall and recognition by accounting for intrusion and false positive errors, respectively. Research also has shown that women outperform men on verbal episodic memory tests. However, gender differences in recall and recognition discriminability and the age-by-gender interaction on these constructs have not been thoroughly examined. METHOD: Cognitively healthy adults (N = 223) 18-91 years in age completed the CVLT-II. Multiple regression analyses were conducted to examine effects of age, gender, and the age-by-gender interaction on CVLT-II subtypes of recall and recognition discriminability. RESULTS: Discriminability scores decreased with increasing age, and women outperformed men. There was an age-by-gender interaction on total, immediate, and free recall discriminability - the negative association between age and scores was stronger in men than in women. Exploratory analyses revealed an inverted U-shaped relationship between age and recall discriminability scores in women. CONCLUSIONS: The present findings support and expand upon the extant literature on aging, gender, and verbal episodic memory, plus describe a novel age-by-gender interaction intrinsic to subtypes of recall discriminability. The findings suggest that methods traditionally used to assess recognition memory function can be used to elucidate age- and gender-related changes in recall ability across the adult lifespan.

Mechanisms of Memory Dysfunction during High Altitude Hypoxia Training in Military Aircrew.

OBJECTIVES: Cognitive dysfunction from high altitude exposure is a major cause of civilian and military air disasters. Pilot training improves recognition of the early symptoms of altitude exposure so that countermeasures may be taken before loss of consciousness. Little is known regarding the nature of cognitive impairments manifesting within this critical window when life-saving measures may still be taken. Prior studies evaluating cognition during high altitude simulation have predominantly focused on measures of reaction time and other basic attention or motor processes. Memory encoding, retention, and retrieval represent critical cognitive functions that may be vulnerable to acute hypoxic/ischemic events and could play a major role in survival of air emergencies, yet these processes have not been studied in the context of high altitude simulation training. METHODS: In a series of experiments, military aircrew underwent neuropsychological testing before, during, and after brief (15 min) exposure to high altitude simulation (20,000 ft) in a pressure-controlled chamber. RESULTS: Acute exposure to high altitude simulation caused rapid impairment in learning and memory with relative preservation of basic visual and auditory attention. Memory dysfunction was predominantly characterized by deficiencies in memory encoding, as memory for information learned during high altitude exposure did not improve after washout at sea level. Retrieval and retention of memories learned shortly before altitude exposure were also impaired, suggesting further impairment in memory retention. CONCLUSIONS: Deficits in memory encoding and retention are rapidly induced upon exposure to high altitude, an effect that could impact life-saving situational awareness and response. (JINS, 2017, 23, 1-10).

Total recognition discriminability in Huntington's and Alzheimer's disease.

Both the original and second editions of the California Verbal Learning Test (CVLT) provide an index of total recognition discriminability (TRD) but respectively utilize nonparametric and parametric formulas to compute the index. However, the degree to which population differences in TRD may vary across applications of these nonparametric and parametric formulas has not been explored. We evaluated individuals with Huntington's disease (HD), individuals with Alzheimer's disease (AD), healthy middle-aged adults, and healthy older adults who were administered the CVLT-II. Yes/no recognition memory indices were generated, including raw nonparametric TRD scores (as used in CVLT-I) and raw and standardized parametric TRD scores (as used in CVLT-II), as well as false positive (FP) rates. Overall, the patient groups had significantly lower TRD scores than their comparison groups. The application of nonparametric and parametric formulas resulted in comparable effect sizes for all group comparisons on raw TRD scores. Relative to the HD group, the AD group showed comparable standardized parametric TRD scores (despite lower raw nonparametric and parametric TRD scores), whereas the previous CVLT literature has shown that standardized TRD scores are lower in AD than in HD. Possible explanations for the similarity in standardized parametric TRD scores in the HD and AD groups in the present study are discussed, with an emphasis on the importance of evaluating TRD scores in the context of other indices such as FP rates in an effort to fully capture recognition memory function using the CVLT-II.

CogSMART Compensatory Cognitive Training for Traumatic Brain Injury: Effects Over 1 Year.

OBJECTIVE: There are very few evidence-based treatments for individuals with mild to moderate traumatic brain injuries. We developed and tested a 12-week, manualized, compensatory cognitive training intervention, Cognitive Symptom Management and Rehabilitation Therapy (CogSMART), which targeted postconcussive symptom management, prospective memory, attention, learning/memory, and executive functioning. The intervention focused on psychoeducation and compensatory strategies such as calendar use, self-talk, note taking, and a 6-step problem-solving method. SETTING: VA Healthcare System. PARTICIPANTS: A total of 50 Veterans with mild to moderate traumatic brain injuries receiving supported employment. DESIGN: Twelve-month randomized controlled trial with participants assigned to receive CogSMART or additional supported employment sessions for the first 12 weeks. Outcome assessments were administered at baseline and 3, 6, and 12 months. MAIN MEASURES: Assessments measured postconcussive symptoms, neuropsychological performance, functional capacity, psychiatric symptom severity, quality of life, and weeks worked during the 12-month trial. RESULTS: Hierarchical linear modeling analyses using all 4 time points demonstrated significant CogSMART-associated reductions in postconcussive symptoms (r = -0.28, P = .026, d = 0.64) and improvements in prospective memory (r = 0.35, P = .031, d = 0.55) and quality of life (r = 0.34, P = .009, d = 1.0). The groups did not differ on weeks worked during the trial. CONCLUSION: CogSMART has the potential to improve postconcussive symptoms, cognitive performance, and self-rated quality of life in individuals with mild to moderate traumatic brain injuries.

Cognitive Symptom Management and Rehabilitation Therapy (CogSMART) for veterans with traumatic brain injury: pilot randomized controlled trial.

Traumatic brain injury (TBI) can result in cognitive impairments and persistent postconcussive symptoms that limit functional recovery, including return to work. We evaluated a 12 wk compensatory cognitive training intervention (Cognitive Symptom Management and Rehabilitation Therapy [CogSMART]) in the context of supported employment for Veterans with mild to moderate TBI. Participants were randomly assigned to receive 12 wk of supported employment plus CogSMART or enhanced supported employment that controlled for therapist attention (control). CogSMART sessions were delivered by the employment specialist and included psychoeducation regarding TBI; strategies to improve sleep, fatigue, headaches, and tension; and compensatory cognitive strategies in the domains of prospective memory, attention, learning and memory, and executive functioning. Compared with controls, those assigned to supported employment plus CogSMART demonstrated significant reductions in postconcussive symptoms (Cohen d = 0.97) and improvements in prospective memory functioning (Cohen d = 0.72). Effect sizes favoring CogSMART for posttraumatic stress disorder symptom severity, depressive symptom severity, and attainment of competitive work within 14 wk were in the small to medium range (Cohen d = 0.35-0.49). Those who received CogSMART rated the intervention highly. Results suggest that adding CogSMART to supported employment may improve postconcussive symptoms and prospective memory. These effects, as well as smaller effects on psychiatric symptoms and ability to return to work, warrant replication in a larger trial.

Yes/no versus forced-choice recognition memory in mild cognitive impairment and Alzheimer's disease: patterns of impairment and associations with dementia severity.

Memory tests are sensitive to early identification of Alzheimer's disease (AD) but less useful as the disease advances. However, assessing particular types of recognition memory may better characterize dementia severity in later stages of AD. We sought to examine patterns of recognition memory deficits in individuals with AD and mild cognitive impairment (MCI). Memory performance and global cognition data were collected from participants with AD (n = 37), MCI (n = 37), and cognitively intact older adults (normal controls, NC; n = 35). One-way analyses of variance (ANOVAs) examined differences between groups on yes/no and forced-choice recognition measures. Individuals with amnestic MCI performed worse than NC and nonamnestic MCI participants on yes/no recognition, but were comparable on forced-choice recognition. AD patients were more impaired across yes/no and forced-choice recognition tasks. Individuals with mild AD (≥120 Dementia Rating Scale, DRS) performed better than those with moderate-to-severe AD (<120 DRS) on forced-choice recognition, but were equally impaired on yes/no recognition. There were differences in the relationships between learning, recall, and recognition performance across groups. Although yes/no recognition testing may be sensitive to MCI, forced-choice procedures may provide utility in assessing severity of anterograde amnesia in later stages of AD. Implications for assessment of insufficient effort and malingering are also discussed.

Posterior cingulum white matter disruption and its associations with verbal memory and stroke risk in mild cognitive impairment.

Medial temporal lobe and temporoparietal brain regions are among the earliest neocortical sites to undergo pathophysiologic alterations in Alzheimer's disease (AD), although the underlying white matter changes in these regions is less well known. We employed diffusion tensor imaging to evaluate early alterations in regional white matter integrity in participants diagnosed with mild cognitive impairment (MCI). The following regions of interests (ROIs) were examined: 1) anterior cingulum (AC); 2) posterior cingulum (PC); 3) genu of the corpus callosum; 4) splenium of the corpus callosum; and 5) as a control site for comparison, posterior limb of the internal capsule. Forty nondemented participants were divided into demographically-similar groups based on cognitive status (MCI: n = 20; normal control: n = 20), and fractional anisotropy (FA) estimates of each ROI were obtained. MCI participants showed greater posterior white matter (i.e., PC, splenium) but not anterior white matter (i.e., AC, genu) changes, after adjusting for age, stroke risk, and whole brain volume. FA differences of the posterior white matter were best accounted for by changes in radial but not axial diffusivity. PC FA was also significantly positively correlated with hippocampal volume as well as with performance on tests of verbal memory, whereas stroke risk was significantly correlated with genu FA and was unrelated to PC FA. When investigating subtypes of our MCI population, amnestic MCI participants showed lower PC white matter integrity relative to those with non-amnestic MCI. Findings implicate involvement of posterior microstructural white matter degeneration in the development of MCI-related cognitive changes and suggest that reduced FA of the PC may be a candidate neuroimaging marker of AD risk.

Construct validity of the item-specific deficit approach to the California verbal learning test (2nd Ed) in HIV infection.

Impairment in list learning and recall is prevalent in HIV-infected individuals and is strongly predictive of everyday functioning outcomes. Consistent with its predominant frontostriatal pathology, the memory profile associated with HIV infection is best characterized as a mixed encoding/retrieval profile. The Item-Specific Deficit Approach (ISDA) was developed by Wright et al. (2009) to elicit indices of Encoding, Consolidation, and Retrieval from the well-validated California Verbal Learning Test (CVLT; Delis, Kramer, Kaplan, & Ober, 1987, 2000). The current study evaluated construct validity of the ISDA for the CVLT-II in 40 persons with HIV-associated neurocognitive disorders (HIV+/HAND+), 103 HIV-infected persons without HAND (HIV+/HAND-), and 43 seronegative comparison participants (HIV-). Results provided mixed support for the construct validity of ISDA indices. HIV+/HAND+ individuals performed significantly more poorly than persons in the HIV+/HAND- and HIV- groups on ISDA Encoding, Consolidation, and Retrieval deficit indices, which demonstrated adequate classification accuracy for diagnosing HIV+/HAND+ participants and evidence of both convergent (e.g., episodic memory) and divergent (e.g., motor skills) correlations in the HIV+/HAND+ participants. However, highly intercorrelated ISDA indices and traditional CVLT-II measures showed comparable between-groups effect sizes, classification accuracy, and correlations to other memory tests, thereby raising uncertainties about the incremental value of the ISDA approach in clinical neuroAIDS research.

Specific measures of executive function predict cognitive decline in older adults.

Decline in executive function has been noted in the prodromal stage of Alzheimer's disease (AD) and may presage more global cognitive declines. In this prospective longitudinal study, five measures of executive function were used to predict subsequent global cognitive decline in initially nondemented older adults. Of 71 participants, 15 demonstrated significant decline over a 1-year period on the Dementia Rating Scale (Mattis, 1988) and the remaining participants remained stable. In the year before decline, the decline group performed significantly worse than the no-decline group on two measures of executive function: the Color-Word Interference Test (CWIT; inhibition/switching condition) and Verbal Fluency (VF; switching condition). In contrast, decliners and non-decliners performed similarly on measures of spatial fluency (Design Fluency switching condition), spatial planning (Tower Test), and number-letter switching (Trail Making Test switching condition). Furthermore, the CWIT inhibition-switching measure significantly improved the prediction of decline and no-decline group classification beyond that of learning and memory measures. These findings suggest that some executive function measures requiring inhibition and switching provide predictive utility of subsequent global cognitive decline independent of episodic memory and may further facilitate early detection of dementia.

Dimensions of executive functioning in schizophrenia and their relationship with processing speed.

CONTEXT: The nature of executive dysfunction in schizophrenia is nebulous, due to inconsistencies in conceptualizing and operationalizing the construct, and the broader question of whether schizophrenia is best characterized in terms of specific vs generalized cognitive deficits. The current study aimed to determine whether executive functions represent unitary vs diverse constructs in schizophrenia. METHODS: Participants included 145 community-dwelling individuals with schizophrenia. Executive functions were measured with the Delis-Kaplan Executive Functioning System (D-KEFS). We conducted an exploratory factor analysis (EFA) with principal axis factoring, as well as parallel analyses to examine the latent constructs underlying the D-KEFS tasks, a second EFA on weighted residuals of the D-KEFS tasks (after accounting for processing speed measured with the Digit Symbol task), and bivariate correlations to examine relationships between the D-KEFS components and relevant demographic and clinical variables, crystallized verbal knowledge, and functional capacity. RESULTS: EFA of the D-KEFS tasks yielded 2 factors (cognitive flexibility/timed tests and abstraction). EFA of the processing speed-weighted D-KEFS residuals also yielded 2 factors (cognitive flexibility and abstraction). Cognitive flexibility was negatively correlated with psychopathology. Better abstraction was associated with higher education, shorter illness duration, and better functional capacity. Both factors were positively correlated with crystallized verbal knowledge. CONCLUSIONS: Executive functions in schizophrenia could be parsed into 2 partially related but separable subconstructs. Future efforts to elucidate functional outcomes as well as neurobiological underpinnings of schizophrenia may be facilitated by attending to the distinction between cognitive flexibility and abstraction.