RESUMEN
For over 50 years, cognitive psychologists and neuropsychologists have relied almost exclusively on a method for computing semantic clustering on list-learning tasks (recall-based formula) that was derived from an outdated assumption about how learning occurs. A new procedure for computing semantic clustering (list-based formula) was developed for the CVLT-II to correct the shortcomings of the traditional method. In the present study we compared the clinical utility of the traditional recall-based method versus the new list-based method using results from the original CVLT administered to 87 patients with Alzheimer's disease and 86 matched normal control participants. Logistic regression and score distribution analyses indicated that the new list-based method enhances the detection of differences in semantic-clustering ability between the groups.
Asunto(s)
Enfermedad de Alzheimer/fisiopatología , Análisis por Conglomerados , Recuerdo Mental/fisiología , Semántica , Aprendizaje Verbal/fisiología , Anciano , Anciano de 80 o más Años , Estudios de Casos y Controles , Femenino , Humanos , Masculino , Persona de Mediana Edad , Pruebas Neuropsicológicas , Análisis Numérico Asistido por ComputadorRESUMEN
Demonstrations of memory changes in those at risk for Alzheimer's disease by the presence of the APOE e4 allele have been inconsistent to date. The present study went beyond traditional analyses of central tendency (i.e., group differences on mean test scores) and also conducted distribution analyses to search for subtle cognitive differences in subgroups of normal-functioning elderly persons with the APOE e4 genotype. The results of the study revealed that (a) the e4 and non-e4 groups failed to differ in terms of their mean scores on tests of memory and verbal skills; and (b) relative to the non-e4 group, the e4 subjects had significantly greater heterogeneity of variance on the memory measures but not on fundamental verbal skills. Logistic regression analyses indicated that the discrepancy in scores on the memory measures was a significant predictor of genotype group membership (82% correct classification rate). Implications of these findings for the detection of a preclinical phase of AD are discussed.
Asunto(s)
Enfermedad de Alzheimer/fisiopatología , Memoria/fisiología , Riesgo , Aprendizaje Verbal/fisiología , Anciano , Anciano de 80 o más Años , Enfermedad de Alzheimer/genética , Análisis de Varianza , Apolipoproteína E4 , Apolipoproteínas E/genética , Distribución de Chi-Cuadrado , Femenino , Humanos , Masculino , Persona de Mediana Edad , Pruebas Neuropsicológicas , Valor Predictivo de las Pruebas , Estudios ProspectivosRESUMEN
This prospective study of nondemented older adults at genetic risk for AD and other types of dementia (i.e., APOE e4 allele) utilized a new Stroop test that includes a dual executive-function condition requiring both response inhibition and cognitive switching. Results indicated that, relative to non-e4 subjects, the e4 group committed more errors, but only on the new Inhibition/Switching condition. In addition, error-rate variance on this task was more heterogeneous for the e4 compared to the non-e4 group, and errors rates correlated significantly with global cognitive status (i.e., DRS scores) for the e4 group but not for the non-e4 group. These findings suggest that vulnerability to errors in response inhibition and cognitive flexibility is present in persons at risk for AD and may signal early emergence of executive dysfunction in preclinical AD. The association between these subtle executive-function deficits and the overall cognitive functioning of at-risk individuals provides further evidence of their utility as a possible preclinical marker of AD.
Asunto(s)
Apolipoproteínas E/genética , Inhibición Psicológica , Trastornos Mentales/genética , Trastornos Mentales/psicología , Anciano , Alelos , Apolipoproteína E4 , Cognición/fisiología , Percepción de Color/genética , Percepción de Color/fisiología , Femenino , Humanos , Masculino , Pruebas Neuropsicológicas , Estudios Prospectivos , Desempeño Psicomotor/fisiologíaRESUMEN
Recent studies have reported cognitive asymmetries in patients with Alzheimer's disease (AD) and in individuals with apolipoprotein E epsilon4 (APOE epsilon4) genotype who are in the preclinical phase of AD. This increased frequpncy of cognitive asymmetry, typically defined as a significant discrepancy (in either direction) between verbal and spatial abilities, often occurs despite an absence of differences on traditional measures of central tendency (i.e., mean test scores). We prospectively studied the relationship between APOE genotype and two modality-specific executive-function tasks: The Verbal Fluency and Design Fluency tests of the Delis-Kaplan Executive Function System (D-KEFS) in 52 normal functioning older adult participants who were grouped according to the presence (n=24) or absence (n=28) of the APOE e4 allele. Nondemented older adults with the APOE epsilon4 allele demonstrated a greater frequency of cognitive asymmetric profile on the new switching conditions of the Verbal and Design Fluency measures than the APOE non-epsilon4 individuals. This study further supports the utility of assessing cognitive asymmetry for the detection of subtle cognitive differences in individuals at-risk for AD, and suggests that dual-task executive function tests (i.e., fluency plus switching) may serve as a useful preclinical marker of AD.