The left posterior sMMN: a marker of syntactic processing compensation in agrammatic aphasia

ABSTRACT

Background

Agrammatic aphasia poses challenges in assessing grammatical abilities due to language comprehension difficulties. The suitability of sMMN as an indicator of syntactic processing abilities in these individuals remains uncertain.

Aims

Two ERP experiments were conducted to investigate whether early syntactic mismatch negativity (sMMN) could assess the syntactic processing ability of Chinese-speaking individuals with agrammatic aphasia.

Methods & Procedures

Prior to the ERP experiments, the Western Aphasia Battery (WAB) and the Northwestern Assessment of Verbs and Sentences-Chinese (NAVS-C) were used to screen people with agrammatism. ERP data were collected for both the agrammatic group (AG) (n = 12) and the control group (CG) (n = 12). The first experiment (Experiment 1) involved a passive tone oddball task to control for the influence of primary sound perception. The second experiment (Experiment 2: experiment 2a and experiment 2b) investigated syntactic processing through a passive speech oddball task. Experiment 2a examined the processing of correct sentences and syntactic violation sentences in context. In contrast, Experiment 2b assessed well-formed sequences and ill-formed sequences out of context.

Outcomes & Results

The results revealed that frontocentral distributed acoustic MMNs were recorded for the CG between 176 - 196ms in Experiment 1, but not for the AG. In Experiment 2, during the 143 - 173ms window, the left anterior sMMN was exclusively observed for the CG, while the left posterior sMMN was specific to the AG. Furthermore, the amplitudes of the left posterior sMMN (143-173ms) were found to have a negative correlation with scores on sentence comprehension tests: the more negative the sMMN, the lower the scores of people with agrammatic aphasia. Notably, this left posterior MMN was absent in Experiment 1.

Conclusions

The early posterior sMMN, discovered for the first time in our study, appears to be more sensitive in detecting syntactic processing impairments in agrammatics compared to the early anterior sMMN. This finding has the potential to enhance the precision of aphasia assessment.

KEYWORDS:

• Agrammatic aphasia
• syntactic mismatch negativity (sMMN)
• syntactic processing
• Chinese
• event related potential (ERP)

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Disclosure statement

We have no known conflicts of interest to disclose.

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/02687038.2024.2318828

Data Availability Statement

All data included in this study are available upon request by contact with the corresponding author.

Notes

^1. Chinese, being a tonal language, employs a five-level notation system in phonetics to document the tones associated with syllables. In Mandarin Chinese, for instance, the notation “55” designates the first (level) tone, “35” signifies the second (rising) tone, “214” is indicative of the third (falling-rising) tone, and “51” represents the fourth (falling) tone.

Additional information

Funding

This research received support from grants provided by the National Social Science Foundation of China [18AYY009], Jiangsu Province Qinglan Project (2020), State Language Commission Foundation [ZDI145-13], and the Graduate Research and Innovation Projects in Jiangsu Province [KYCX18_2051].