Mikael Roll

Word accents and morphology—ERPs of Swedish word processing

Results indicating that high stem tones realizing word accents activate a certain class of suffixes in online processing of Central Swedish are presented. This supports the view that high Swedish word accent tones are induced onto word stems by particular suffixes rather than being associated with words in the mental lexicon. Using event-related potentials, effects of mismatch between word accents and inflectional suffixes were compared with mismatches between stem and suffix in terms of declension class. Declensionally incorrect suffixes yielded an increase in the N400, indicating problems in lexical retrieval, as well as a P600 effect, showing reanalysis. Both declensionally correct and incorrect high tone-inducing (Accent 2) suffixes combined with a mismatching low tone (Accent 1) on the stems produced P600 effects, but did not increase the N400. Suffixes usually co-occurring with Accent 1 did not yield any effects in words realized with the nonmatching Accent 2, suggesting that Accent 1 is a default accent, lacking association with any particular suffix. High tones on Accent 2 words also produced an early anterior positivity, interpreted as a P200 effect reflecting preattentive processing of the tone.

Left-edge boundary tone and main clause verb effects on syntactic processing in embedded clauses - An ERP study

We examined the effects of main clause verb pragmatics and left-edge boundary tones on syntactic processing in Swedish embedded clauses, using listener judgments and Event-Related Potentials. When the syntactic structure did not match the expectation based on the occurrence of a left-edge boundary tone, the acceptance rate decreased significantly, and a biphasic positive effect with an early peak (P345) and a late peak (P600) showed increased processing load. A larger continuous positive effect (P600) was obtained by changing an assertive main clause verb to a nonassertive verb, thereby modifying the lexical pragmatic context of the embedded clause. Increased positivity was also seen at the left-edge boundary tone when it mismatched a preceding nonassertive verb. We conclude that left-edge boundary tones are used in addition to verb pragmatics to guide the syntactic processing of embedded clauses in Swedish, and that pragmatic and prosodic information is integrated immediately.

Activating without inhibiting: Left-edge boundary tones and syntactic processing

Right-edge boundary tones have earlier been found to restrict syntactic processing by closing a clause for further integration of incoming words. The role of left-edge intonation, however, has received little attention to date. We show that Swedish left-edge boundary tones selectively facilitate the on-line processing of main clauses, the syntactic structure they are associated with. In spoken Swedish, main clauses are produced with a left-edge boundary tone, which is absent in subordinate clauses. Main and subordinate clauses are further distinguished syntactically by word order when containing sentence adverbs. The effects of tone and word order on the processing of embedded main, subordinate, and neutral clauses (lacking sentence adverbs) were measured using ERPs. A posterior P600 in embedded main clauses and a smaller P600 in subordinate clauses indicated that embedded clauses with sentence adverbs were structurally less expected than neutral clauses and thus were reanalyzed. The tone functioned as a cue for main clause word order, selectively reducing the P600 in embedded main clauses, without affecting the processing of subordinate or neutral clauses. Its perception was reflected in a right frontal P200 effect. The left-edge boundary tone thus seems to activate a main clause structure, albeit without suppressing alternative structures. The P600 was also preceded by a short positive effect in cases where a left-edge boundary tone was absent.

Word-stem tones cue suffixes in the brain.

High and low tones on Swedish word stems are associated with different classes of suffixes. We tested the electrophysiological effects of high and low stem tones as well as tonally cued and uncued suffixes. Two different tasks were used involving either choosing the suffix-dependent meaning of the words, or pressing a button when the word ended. To determine whether effects were in fact due to association of tones with lexical material, delexicalized stimuli were also used. High tones in lexical items produced an increase in the P2 component in both tasks, interpreted as showing passive anticipatory attention allocated to the associated upcoming suffix. This effect was absent for delexicalized forms, where instead an N1 increase was found for high tones, indicating that the high pitch was unexpected in the absence of lexical material, and did not lead to anticipatory attention. A P600 effect was found for uncued high-associated suffixes in the semantic task, which was also where the largest increase was found in reaction times. This suggests that the tonal cues were most important when participants were required to process the meaning of the words.

A neurolinguistic study of South Swedish word accents : Electrical brain potentials in nouns and verbs

The brain response to words with correct and incorrect word accent–suffix combinations in South Swedish was investigated using electroencephalography (EEG). Accent 1 yielded an increased brain response (‘preactivation negativity’) that has previously been interpreted as reflecting preactivation of suffixes. Preactivation is greater for accent 1 due to its association with a limited set of suffixes, whereas accent 2 is default for compound words. The tonal realization of the word accent opposition in South Swedish is practically the mirror image of that in Central Swedish, where a similar preactivation negativity has been found. Therefore, the brain response is unlikely to result from a difference in acoustic features between the word accents. Invalidly cued suffixes yielded brain response pattern showing increased processing load of the unexpected suffix (negative electric potential) followed by its reprocessing (positivity ‘P600’). (Less)

Pre-Activation Negativity (PrAN) in Brain Potentials to Unfolding Words

We describe an event-related potential (ERP) effect termed the “pre-activation negativity” (PrAN), which is proposed to index the degree of pre-activation of upcoming word-internal morphemes in speech processing. Using lexical competition measures based on word-initial speech fragments (WIFs), as well as statistical analyses of ERP data from three experiments, it is shown that the PrAN is sensitive to lexical competition and that it reflects the degree of predictive certainty: the negativity is larger when there are fewer upcoming lexical competitors.

Predominance of caudate nucleus lesions in acute ischaemic stroke patients with impairment in language and speech

Whereas traditional views of language processing in the brain have assumed that the language function is concentrated to a limited number of cortical areas (Brocas and Wernickes areas), current knowledge points at a much more complex system of language and speech processing involving many brain areas, both cortical and subcortical. The purpose of the current study was to make an unbiased assessment of which cerebral areas are affected in first‐ever acute ischaemic stroke patients identified as having language and speech impairments according to the National Institutes of Health Stroke Scale (NIHSS).

Stem Tones Pre-activate Suffixes in the Brain

Results from the present event-related potentials (ERP) study show that tones on Swedish word stems can rapidly pre-activate upcoming suffixes, even when the word stem does not carry any lexical meaning. Results also show that listeners are able to rapidly restore suffixes which are replaced with a cough. Accuracy in restoring suffixes correlated positively with the amplitude of an anterior negative ERP elicited by stem tones. This effect is proposed to reflect suffix pre-activation. Suffixes that were cued by an incorrect tone elicited a left-anterior negativity and a P600, suggesting that the correct processing of the suffix is crucially tied to the activation of the preceding validly associated tone.

Forehearing words: Pre-activation of word endings at word onset

Occurring at rates up to 6-7 syllables per second, speech perception and understanding involves rapid identification of speech sounds and pre-activation of morphemes and words. Using event-related potentials (ERPs) and functional magnetic resonance imaging (fMRI), we investigated the time-course and neural sources of pre-activation of word endings as participants heard the beginning of unfolding words. ERPs showed a pre-activation negativity (PrAN) for word beginnings (first two segmental phonemes) with few possible completions. PrAN increased gradually as the number of possible completions of word onsets decreased and the lexical frequency of the completions increased. The early brain potential effect for few possible word completions was associated with a blood-oxygen-level-dependent (BOLD) contrast increase in Brocas area (pars opercularis of the left inferior frontal gyrus) and angular gyrus of the left parietal lobe. We suggest early involvement of the left prefrontal cortex in inhibiting irrelevant left parietal activation during lexical selection. The results further our understanding of the importance of Brocas area in rapid online pre-activation of words.

Sensory-specific anomic aphasia following left occipital lesions: Data from free oral descriptions of concrete word meanings

The present study investigated hierarchical lexical semantic structure in oral descriptions of concrete word meanings produced by a subject (ZZ) diagnosed with anomic aphasia due to left occipital lesions. The focus of the analysis was production of a) nouns at different levels of semantic specificity (e.g., “robin”–“bird”–“animal”) and b) words describing sensory or motor experiences (e.g., “blue,” “soft,” “fly”). Results show that in contrast to healthy and aphasic controls, who produced words at all levels of specificity and mainly vision-related sensory information, ZZ produced almost exclusively nouns at the most non-specific levels and words associated with sound and movement.