Zoltán Bánréti

Recursion in Aphasia.

This study investigates how aphasic impairment impinges on syntactic and/or semantic recursivity of human language. A series of tests has been conducted with the participation of five Hungarian speaking aphasic subjects and 10 control subjects. Photographs representing simple situations were presented to subjects and questions were asked about them. The responses are supposed to involve formal structural recursion, but they contain semantic-pragmatic operations instead, with ‘theory of mind’ type embeddings. Aphasic individuals tend to exploit the parallel between ‘theory of mind’ embeddings and syntactic-structural embeddings in order to avoid formal structural recursion. Formal structural recursion may be more impaired in Brocas aphasia and semantic recursivity may remain selectively unimpaired in this type of aphasia.

ERP correlates of prosody and syntax interaction in case of embedded sentences

Abstract Understanding spoken language depends on processing the delicate combination of grammatical structure, meaning and prosody of utterances. Previous studies have established that prosody influences the processing of sentences when the grammatical structure is ambiguous, however it is unclear how closely prosody and syntax are related when there is no ambiguity. In an event-related brain potential (ERP) study, we investigated the processing of embedded normal and pseudosentences in which all function and content words were replaced by meaningless words. Sentences could have either natural prosodic structure or incongruent prosodic structure, where the prosody deviated from the one expected based on the syntactic structure, but otherwise the sentences were unambiguous. The resulting ERP components (CPS) showed that the construction of prosodic structure was similar in normal and pseudosentences, thus suggesting that prosody has an abstract, recursive representation, independent of other linguistic information. Moreover, we found evidence that the incongruent prosody was not only detected (shown by the RAN), but it induced neural reintegration processes (shown by the P600) in spite of the syntactic structure of sentences being intact. These results suggest that the prosodic structure is a mandatory constituent of sentence structure building whenever it is present.

Multiple lexical selection and parallelism in Hungarian VP ellipsis

We propose that forward and backward ellipsis should both be regardedas the non-insertion of the phonological form under the terminal nodes offully specied lexical-figrammatical feature matrices. We conceive of the creationof structures with VP ellipsis as the multiple selection from the lexiconof the lexical items relevant for the licensing and execution of ellipsisand enumerating them at the syntactic input in such away that they can satisfythe constraints of structural and referential parallelism. It is in this casethat the option of not inserting the phonological form may be chosen.

A speech recognition-based solution for the automatic detection of mild cognitive impairment from spontaneous speech

Background: Even today the reliable diagnosis of the prodromal stages of Alzheimer’s disease (AD) remains a great challenge. Our research focuses on the earliest detectable indicators of cognitive de-cline in mild cognitive impairment (MCI). Since the presence of language impairment has been reported even in the mild stage of AD, the aim of this study is to develop a sensitive neuropsychological screening method which is based on the analysis of spontaneous speech production during performing a memory task. In the future, this can form the basis of an Internet-based interactive screening software for the recognition of MCI. Methods: Participants were 38 healthy controls and 48 clinically diagnosed MCI patients. The provoked spontaneous speech by asking the patients to recall the content of 2 short black and white films (one direct, one delayed), and by answering one question. Acoustic parameters (hesitation ratio, speech tempo, length and number of silent and filled pauses, length of utterance) were extracted from the recorded speech sig-nals, first manually (using the Praat software), and then automatically, with an automatic speech recogni-tion (ASR) based tool. First, the extracted parameters were statistically analyzed. Then we applied machine learning algorithms to see whether the MCI and the control group can be discriminated automatically based on the acoustic features. Results: The statistical analysis showed significant differences for most of the acoustic parameters (speech tempo, articulation rate, silent pause, hesitation ratio, length of utterance, pause-per-utterance ratio). The most significant differences between the two groups were found in the speech tempo in the delayed recall task, and in the number of pauses for the question-answering task. The fully automated version of the analysis process – that is, using the ASR-based features in combination with machine learning - was able to separate the two classes with an F1-score of 78.8%. Conclusion: The temporal analysis of spontaneous speech can be exploited in implementing a new, auto-matic detection-based tool for screening MCI for the community.

Detecting mild cognitive impairment by exploiting linguistic information from transcripts

Here we seek to automatically identify Hungarian patients suffering from mild cognitive impairment (MCI) based on linguistic features collected from their speech transcripts. Our system uses machine learning techniques and is based on several linguistic features like characteristics of spontaneous speech as well as features exploiting morphological and syntactic parsing. Our results suggest that it is primarily morphological and speechbased features that help distinguish MCI patients from healthy controls.

Lexical Recursion in Aphasia: Case Studies

The processes of lexical recursion is examined by word-picture matching tests requiring the recursive construction of compound words. We used productive endocentric compounds whose rightmost constituent is a deverbal noun involving the affix -o/-ő. Such heads take left-hand dependents in the role of complements, for instance: viz-tisztito-szerelő-oktato ‘water-cleaner-fitter-instructor’. Normal and aphasic subjects participated in the word-picture matching tests. Aphasics fell into two groups in terms of their patterns of responses. Anomic aphasics exhibited severe impairment in lexical recursion. They attempted compensatory strategies involving “exit to syntax” as a substitute for constructing the target compound words: they produced sentences or syntactic phrases rather than complex compounds. In this group lexical recursive operations turned out to be more impaired than sentence recursion. The compensation strategy involves a switch from the impaired subsystem to the unimpaired or less impaired subsystem. The other aphasic group involved Broca’s and conduction aphasics. They reacted to tasks requiring lexical recursion by the strategy of lexical search: they preferred the use of very simplex synonyms or hyperonyms to constructing the target compounds. Their recursive lexical operations showed a deficit and their recursive syntactic operations were also limited. There was no linguistic compensation strategy available for them.