Discriminating nonfluent/agrammatic and logopenic PPA variants with automatically extracted morphosyntactic measures...

Area of Science:

• Neurolinguistics
• Computational Linguistics
• Neuroimaging

Background:

• Morphosyntactic assessment is crucial for diagnosing nonfluent/agrammatic variant primary progressive aphasia (nfvPPA).
• Current diagnostic tests for nfvPPA are prone to bias and struggle to differentiate it from logopenic variant PPA (lvPPA).
• The neural underpinnings of morphosyntactic deficits in nfvPPA require further investigation.

Purpose of the Study:

• To develop and validate an automated method using natural language processing (NLP) for analyzing morphosyntactic disturbances in nfvPPA.
• To identify specific morphosyntactic markers that can reliably differentiate nfvPPA from healthy controls (HC) and lvPPA.
• To explore the neuroanatomical correlates of the most significant morphosyntactic markers in nfvPPA.

Main Methods:

• Utilized NLP tools for part-of-speech tagging on picture descriptions from 35 nfvPPA patients, 10 HC, and 26 lvPPA patients.
• Extracted features including conjunctions, tense markers, and pronoun types.
• Employed gradient boosting machines for classification and feature importance analysis, followed by voxel-based morphometry for neuroimaging correlation.

Main Results:

• Individuals with nfvPPA exhibited significantly fewer morphosyntactic elements compared to lvPPA and HC groups.
• The automated analysis achieved high accuracy in discriminating nfvPPA from lvPPA (AUC = 0.95) and HC (AUC = 0.82).
• Subordinating conjunctions emerged as the most discriminative feature, correlating with cortical atrophy in the left posterior inferior frontal gyrus (p_FWE < 0.05).

Conclusions:

• Automated morphosyntactic analysis offers an efficient and objective method for distinguishing nfvPPA from lvPPA.
• Key morphosyntactic markers, particularly subordinating conjunction deficits, are associated with core brain atrophy regions in nfvPPA.
• This NLP-driven approach can significantly aid in the diagnostic challenges of primary progressive aphasia.