Conceptual elaboration versus direct lexical access in WAIS-similarities: differential effects of white-matter lesions and gray matter volumes

ABSTRACT

Wechsler Adult Intelligence Scale (WAIS) subscale Similarities have been classified as a test of either verbal comprehension or of inductive reasoning. The reason may be that items divide into two categories. We tested the hypothesis of heterogeneity of items in WAIS-Similarities. Consecutive patients at a memory clinic and healthy controls participated in the study. White-matter hyperintensities (WMHs) and normalized temporal lobe volumes were measured based on Magnetic resonance Imaging (MRI), and tests of verbal memory and attention were used in addition to WAIS-Similarities to collect behavioural data. Factor analysis supported the hypothesis that two factors are involved in the performance of WAIS-similarities: (1) semiautomatic lexical access and (2) conceptual elaboration. These factors were highly correlated but provided discriminative diagnostic information: In logistic regression analyses, scores of the lexical access factor and of the conceptual elaboration factor discriminated patients with mild cognitive impairment from Alzheimer’s disease patients and from healthy controls, respectively. High scores of WMH, indicating periventricular white-matter lesions, predicted factor scores of direct lexical access but not those of conceptual elaboration, which were predicted only by medial and lateral temporal lobe volumes.

KEYWORDS:

• WAIS-similarities
• conceptual elaboration
• lexical access
• white-matter lesions
• gray matter volumes

Acknowledgments

We thank Lena Bronge for the white-matter lesion measurements, Per Julin for the volumetric measurements, Lars-Olof Wahlund for encouraging supervision, Ove Almkvist for neuropsychological expertise, and Bengt Winblad for general support. We also thank Per Östberg at the Division of Speech and Language Pathology, Department of Clinical Sciences, Intervention and Technology, Karolinska Institutet, Stockholm, for encouraging theoretical discussions.

Disclosure statement

No potential conflict of interest was reported by the authors.