Interaction of right- and left-edge prosodic boundaries in syntactic parsing

Cortical thickness and surface area of left anterior temporal areas affects processing of phonological cues to morphosyntax

Lack of methods to experimentally assess the perceptual processing of sound features and allow one to measure differences in phonological proficiency has been a limitation for speech processing studies in native speakers. Tonal features associated with Swedish word-stems, word accents, which cue grammatical suffixes, constitute, however, such sound features that can be exploited to generate measures of reliance on morphosyntactically relevant phonological information during word processing. Specifically, there is a natural variance between native speakers in response time (RT) difference between phonologically valid and invalid word accent-suffix combinations that can be used to quantify perceptual phonological proficiency. This study uses ultra-high field magnetic resonance imaging (MRI) to investigate word accents as phonological cues to morphosyntactic meaning. The study adds to the understanding of the neural basis for both morphosyntactically relevant phonological cues by reporting correlations between differences in listeners' RT for validly and invalidly cued suffixes and cortical thickness in left anterior and middle temporal gyrus, and the left anterior superior temporal sulcus as well as cortical surface area in the left middle and inferior temporal gyri. The cortical areas studied are known constituents of the ventral speech processing stream, necessary for word and phrase recognition.

Rapid syntactic pre-activation in Broca's area: Concurrent electrophysiological and haemodynamic recordings

Listeners are constantly trying to predict what the speaker will say next. We concurrently measured the electrophysiological and haemodynamic correlates of syntactic pre-activation, investigating when and where the brain processes speech melody cues to upcoming word order structure. Pre-activation of syntactic structure was reflected in a left-lateralised pre-activation negativity (PrAN), which was subserved by Broca's area in the left inferior frontal gyrus, as well as the contiguous left anterior insula.

Prosodic phrasing in the presence of unambiguous verb information--ERP evidence from German

In spoken language, prosodic boundaries contribute to the way we understand sentences on-line. The present experiment used ERPs to investigate whether the informativity of prosodic boundaries depends on the availability of other linguistic cues. To this end, we examined the interplay between verb information, case and prosody in German verb-second structures. Unlike previous studies, unambiguous verb information signaled transitivity (a two-argument structure) before reaching potential arguments. Participants listened to sentences containing a succession of two noun phrases (NPs) that were either temporarily ambiguous or unambiguous. Ambiguous NPs were locally compatible with both an argument reading and a modifier reading. Sentences were presented with an early prosodic boundary typical of an argument reading or a late prosodic boundary typical of a modifier reading. Our findings suggest that the brain considers multiple cues for determining the argument status of an NP. In the presence of unambiguous cues like case or verb information, prosodic information plays a relatively minor role than when prosody is the only unambiguous cue. Contrary to previous studies, a mismatch between prosody and argument status was reflected by a late positive complex (LPC) without a preceding N400. Thus, unlike in previous studies, prosody did not affect early processing phases of argument integration, but a later well-formedness evaluation. For ambiguous sentences, prosodic boundaries triggered reanalysis processes reflected by the LPC. Our results suggest that cognitive processes related to prosody can be modulated by the availability of other linguistic information types, thus paving the way for neurolinguistic investigations of cross-linguistic differences in prosodic effects on sentence comprehension.

Prosodic cues enhance rule learning by changing speech segmentation mechanisms

Prosody has been claimed to have a critical role in the acquisition of grammatical information from speech. The exact mechanisms by which prosodic cues enhance learning are fully unknown. Rules from language often require the extraction of non-adjacent dependencies (e.g., he plays, he sings, he speaks). It has been proposed that pauses enhance learning because they allow computing non-adjacent relations helping word segmentation by removing the need to compute adjacent computations. So far only indirect evidence from behavioral and electrophysiological measures comparing learning effects after exposure to speech with and without pauses support this claim. By recording event-related potentials during the acquisition process of artificial languages with and without pauses between words with embedded non-adjacent rules we provide direct evidence on how the presence of pauses modifies the way speech is processed during learning to enhance segmentation and rule generalization. The electrophysiological results indicate that pauses as short as 25 ms attenuated the N1 component irrespective of whether learning was possible or not. In addition, a P2 enhancement was present only when learning of non-adjacent dependencies was possible. The overall results support the claim that the simple presence of subtle pauses changed the segmentation mechanism used reflected in an exogenously driven N1 component attenuation and improving segmentation at the behavioral level. This effect can be dissociated from the endogenous P2 enhancement that is observed irrespective of the presence of pauses whenever non-adjacent dependencies are learned.

Using event-related potentials to measure phrase boundary perception in English

Background

The closure positive shift (CPS) event related potential (ERP) is commonly used as a neural measure of phrase boundary perception in speech. The present study investigated whether the CPS was elicited by acoustic cues at phrase boundaries in English. ERPs were recorded when participants listened passively to sentences with either early or late phrase boundaries.

Results

The closure positive shift (CPS) ERP was elicited at both early and late phrase boundaries. However, the latency, amplitude, and scalp distribution of these passive CPS ERPs in English sentences differed to active CPS ERPs measured in non-English sentences in previous studies.

Conclusions

These results show that acoustic cues at the phrase boundaries in English are sufficient to elicit the CPS, and suggest that different processes might be involved in the generation of the CPS in active and passive conditions.

Time-driven effects on parsing during reading

The phonological trace of perceived words starts fading away in short-term memory after a few seconds. Spoken utterances are usually 2-3s long, possibly to allow the listener to parse the words into coherent prosodic phrases while they still have a clear representation. Results from this brain potential study suggest that even during silent reading, words are organized into 2-3s long 'implicit' prosodic phrases. Participants read the same sentences word by word at different presentation rates. Clause-final words occurring at multiples of 2-3s from sentence onset yielded increased positivity, irrespective of presentation rate. The effect was interpreted as a closure positive shift (CPS), reflecting insertion of implicit prosodic phrase boundaries every 2-3s. Additionally, in participants with low working memory span, clauses over 3s long produced a negativity, possibly indicating increased working memory load.