Spatial language abilities and cognition across the adult-lifespan and in early Alzheimer's disease

Space constitutes one of the core framing structures of experience in the natural environment. Therefore, communicating spatial information with verbal means, such as locative relations between objects, is vital for numerous everyday activities and constitutes a core part of human linguistic communication. The present project aimed to 1) develop psychometrically sound measures assessing spatial language abilities, including naming static and dynamic spatial relations, memory for route- and survey-based descriptions, and comprehension of descriptions of locative relations under different spatial reference frames; 2) identify the trajectories of these spatial language abilities across the adult-lifespan and contrast them against trajectories of various (non-verbal) visuospatial and (non-spatial) verbal abilities; and 3) investigate spatial language abilities in individuals who are at an early stage of Alzheimer’s disease (AD), for the first time. Across a series of studies involving 160 adults aged between 18 and 85, we found comparable age-related declines in spatial language and visuospatial abilities, although their onset and magnitude depended on the type of subability examined. By contrast, verbal abilities remained well-preserved with increasing age. Moreover, performance in spatial language measures was found to discriminate mild AD patients and age-, education-, and gender-matched controls to a very high degree. The results of the present work have several theoretical and practical implications, as they 1) establish the test-retest reliability, and the concurrent, construct and discriminative validity of the newly-developed spatial language measures; 2) reveal a number of divergent and convergent domain-specific cognitive changes across the adult-lifespan; 3) extend the large existing literature on the detrimental (a)typical ageing effects on visuospatial cognition by demonstrating that spatial processing is also compromised when assessed through language; and 4) suggest that language- and perception-based representations of space are underpinned by comparable cognitive operations and supported by overlapping neural networks that are particularly sensitive to ageing effects.