PhD & Post-doc Projects

Linguistic complexity as a tool for diagnosing Alzheimer’s dementia more precisely

Postdoc: Jurriaan Witteman
Supervisors: Niels O. Schiller, Wiesje van der Flier (Vrije Universiteit Medical Center in Amsterdam)

j witteman blog photo 347x132Alzheimer’s dementia (AD) is a progressive brain disease affecting about 1.5% of the population. AD is associated with a buildup of pathological proteins in brain cells that cause malfunctioning of these brain cells. Initially, only brain cells in non-vital brain areas are mildly affected, resulting in subtle cognitive deficits that are only detectable through standardized cognitive testing. As the disease progresses, however, malfunctioning increases and spreads to vital neural systems, ultimately causing death. Because life expectancy has been increasing and the chance of getting AD increases as we get older, the amount of people who will be suffering from AD is likely to increase drastically in the future. Therefore, there is a great need to improve diagnosis and treatment of AD. Early diagnosis of AD is important because earlier treatment can prolong and improve the course of the disease. Here linguistics could provide a helping hand.  

Recall that AD starts with subtle cognitive deficits that are only detectable through standardized cognitive testing. One cognitive ability that may be affected early in AD but has been overlooked so far are linguistic abilities. Utterances, particularly complex ones, tax the cognitive system extensively and hence the subtle cognitive disturbances induced by early AD may be detectable through the reduced ability of the cognitive system to produce complex utterances. But what do we mean with ‘linguistically complex’ precisely? This can be approached from various angles. For instance, syntactically, a sentence such as ‘The elephant that is large runs’ is more complex than ‘The large elephant runs’ and hence the former would tax our cognitive system more than the latter. Similarly, looking at semantics, utterances that contain a large number of different content words are more complex than utterances that contain only a small number of content words, and again may tax the cognitive system more than the latter.  Thus, the syntactic and semantic complexity of utterances may be reduced in early AD and may be used (together with other diagnostic instruments) to diagnose AD at an earlier stage than is currently possible.

Therefore, LUCL is currently running a study (under the supervision of Prof. Niels Schiller) in collaboration with the Alzheimer Center at the Vrije Universiteit Medical Center in Amsterdam (in the context of a research project directed by Prof. Wiesje van der Flier) to investigate whether linguistic complexity can be used to predict the onset of AD. From a large cohort of people who are admitted to the Alzheimer Centre with subjective memory complaints but without the first signs of AD, we record 5 minutes of spontaneous conversation by asking them to describe a picture in their own words. Furthermore, protein weighted brain scans are collected that can detect the build up of pathological proteins in the brain. A year later, all participants will return for a cognitive assessment and brain scans, and this time a significant proportion will have developed the first signs of AD (based on cognitive testing and brain scans). Using the utterances collected a year earlier, we will analyse whether the syntactic and semantic complexity of the utterances can predict the onset of the first AD symptoms.

Hopefully, this marriage between linguistics and neurology will be fruitful, allowing us to diagnose AD at an earlier stage.

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