Structural Correlates of Speech Biomarkers in Alzheimer’s Disease and Mild Cognitive Impairment

Abstract

AbstractBackgroundIn the present study, we aimed to confirm the association between speech characteristics of individuals with Alzheimer’s disease (AD) and amnestic mild cognitive impairment (MCI) and brain regions, and to investigate the neurobiological basis of speech‐based AD detection.MethodIndividuals with MCI (n = 13, age = 78.3), mild‐to‐moderate AD (n = 12, age = 77.8) underwent a structural MRI scan and engaged in three speech tasks: an interview, sentence repetition, and paragraph recall. From the speech samples, we extracted frequency‐related, intensity‐related, and temporal features which were found to be altered in the course of AD and MCI pathology. We selected nine regions of interest (ROI) which were found to be involved in speech production and reduced in MCI and AD pathology; the Inferior Frontal Gyrus (IFG), the Medial Frontal Gyrus (MFG), the Precuneus, the Inferior Parietal Lobe (IPL), Inferior Temporal Gyrus (ITG), Medial Temporal Gyrus (MTG), the Superior Temporal Gyrus (STG), the Fusiform Gyrus (FFG), and the Cerebellum. The linear mixed‐effect analysis was used to identify the associations between speech features and regional brain volumes.ResultThe Left IPL (χ2 (1) = 7.69, corrected P = 0.033), the Right ITG (χ2 (1) = 11.5, corrected P = 0.0128) the Right FFG (χ2 (1) = 9.35, corrected P = 0.0198) reduced the pitch of voice by about 0.887 ± 0.292, 1.368 ± 0.329, and 1.69 ± 0.429 respectively. The associations between the Right FFG (χ2 (1) = 4.58, corrected P = 0.0900), Left FFG (χ2 (1) = 5.87, corrected P = 0.0675) and loudness were marginally significant, with the reduction of volumes in the Right FFG and Left FFG decreasing the loudness by 0.096 ± 0.041, and 0.1165 ± 0.0454. The marginally significant associations were observed between the Right IPL (χ2 (1) = 4.75, corrected P = 0.0900), the Left FFG (χ2 (1) = 0.39, corrected P = 0.53) and the speech rate, and the atrophy of brain regions decreased the speech rate by 0.0824 ± 0.0363, 0.0535 ± 0.0079.ConclusionThe present study identified the associations between speech biomarkers and regional brain volumes providing clinical validity for the speech‐based Alzheimer’s disease detection.