Tracking independence and merging of prosodic and phonemic processing across infancy.

Recent evidence suggests division of labor in phonological analysis underlying speech recognition. Adults and children appear to decompose the speech stream into phoneme-relevant information and into syllable stress. Here we investigate whether both speech processing streams develop from a common path in infancy, or whether there are two separate streams from early on. We presented stressed and unstressed syllables (spoken primes) followed by initially stressed early learned disyllabic German words (spoken targets). Stress overlap and phoneme overlap between the primes and the initial syllable of the targets varied orthogonally. We tested infants 3, 6 and 9 months after birth. Event-related potentials (ERPs) revealed stress priming without phoneme priming in the 3-month-olds; phoneme priming without stress priming in the 6-month-olds; and phoneme priming, stress priming as well as an interaction of both in 9-month-olds. In general the present findings reveal that infants start with separate processing streams related to syllable stress and to phoneme-relevant information; and that they need to learn to merge both aspects of speech processing. In particular the present results suggest (i) that phoneme-free prosodic processing dominates in early infancy; (ii) that prosody-free phoneme processing dominates in middle infancy; and (iii) that both types of processing are operating in parallel and can be merged in late infancy.

Ongoing Sign Processing Facilitates Written Word Recognition in Deaf Native Signing Children.

Signed and written languages are intimately related in proficient signing readers. Here, we tested whether deaf native signing beginning readers are able to make rapid use of ongoing sign language to facilitate recognition of written words. Deaf native signing children (mean 10 years, 7 months) received prime target pairs with sign word onsets as primes and written words as targets. In a control group of hearing children (matched in their reading abilities to the deaf children, mean 8 years, 8 months), spoken word onsets were instead used as primes. Targets (written German words) either were completions of the German signs or of the spoken word onsets. Task of the participants was to decide whether the target word was a possible German word. Sign onsets facilitated processing of written targets in deaf children similarly to spoken word onsets facilitating processing of written targets in hearing children. In both groups, priming elicited similar effects in the simultaneously recorded event related potentials (ERPs), starting as early as 200 ms after the onset of the written target. These results suggest that beginning readers can use ongoing lexical processing in their native language - be it signed or spoken - to facilitate written word recognition. We conclude that intimate interactions between sign and written language might in turn facilitate reading acquisition in deaf beginning readers.

No Evidence of Robust Noun-Referent Associations in German-Learning 6- to 14-Month-Olds.

Work with the looking-while-listening (LWL-) paradigm suggested that 6-month-old English-learning infants associated several labels for common nouns with pictures of their referents: While one distractor picture was present, infants systematically fixated the named target picture. However, recent work revealed constraints of infants' noun comprehension. The age at which these abilities can be obtained appears to relate to the infants' familiarity with the talker, the target language, and word frequency differences in target-distractor pairs. Here, we present further data to this newly established field of research. We tested 42 monolingual German-learning infants aged 6-14 months by means of the LWL-paradigm. Infants saw two pictures side-by-side on a screen, whilst an unfamiliar male talker named one of both. Overall, infants did not fixate the target picture more than the distractor picture. In line with previous results, infants' performance on the task was higher when target and distractor differed within their word frequency-as operationalized by the parental rating of word exposure. Together, our results add further evidence for constraints on early word learning. They point to cross-linguistic differences in early word learning and strengthen the view that infants might use extra-linguistic cues within the stimulus pairing, such as frequency imbalance, to disambiguate between two potential referents.

Phonemic Training Modulates Early Speech Processing in Pre-reading Children.

Phonemic awareness and rudimentary grapheme knowledge concurrently develop in pre-school age. In a training study, we tried to disentangle the role of both precursor functions of reading for spoken word recognition. Two groups of children exercised with phonemic materials, but only one of both groups learnt corresponding letters to trained phonemes. A control group exercised finger-number associations (non-linguistic training). After the training, we tested how sensitive children were to prime-target variation in word onset priming. A group of young adults took part in the same experiment to provide data from experienced readers. While decision latencies to the targets suggested fine-grained spoken word processing in all groups, event-related potentials (ERPs) indicated that both phonemic training groups processed phonemic variation in more detail than the non-linguistic training group and young adults at early stages of speech processing. Our results indicate temporal plasticity of implicit speech processing in pre-school age as a function of explicit phonemic training.

Activation of Literal Word Meanings in Idioms: Evidence from Eye-tracking and ERP Experiments.

How the language processing system handles formulaic language such as idioms is a matter of debate. We investigated the activation of constituent meanings by means of predictive processing in an eye-tracking experiment and in two ERP experiments (auditory and visual). In the eye-tracking experiment, German-speaking participants listened to idioms in which the final word was excised (Hannes let the cat out of the . . .). Well before the offset of these idiom fragments, participants fixated on the correct idiom completion (bag) more often than on unrelated distractors (stomach). Moreover, there was an early fixation bias towards semantic associates (basket) of the correct completion, which ended shortly after the offset of the fragment. In the ERP experiments, sentences (spoken or written) either contained complete idioms, or the final word of the idiom was replaced with a semantic associate or with an unrelated word. Across both modalities, ERPs reflected facilitated processing of correct completions across several regions of interest (ROIs) and time windows. Facilitation of semantic associates was only reliably evident in early components for auditory idiom processing. The ERP findings for spoken idioms compliment the eye-tracking data by pointing to early decompositional processing of idioms. It seems that in spoken idiom processing, holistic representations do not solely determine lexical processing.

Neurophysiological evidence for underspecified lexical representations: asymmetries with word initial variations.

How does the mental lexicon cope with phonetic variants in recognition of spoken words? Using a lexical decision task with and without fragment priming, the authors compared the processing of German words and pseudowords that differed only in the place of articulation of the initial consonant (place). Across both experiments, event-related brain potentials indicated that pseudowords with initial noncoronal place (e.g., *Brachen) activate words with initial coronal place (e.g., Drachen [dragon]). In contrast, coronal pseudowords (e.g., *Drenze) do not as effectively activate noncoronal words (e.g., Grenze [border]). Thus, certain word onset variations do not hamper the speech recognition system. The authors interpret this asymmetry as a consequence of underspecified coronal place of articulation in the mental lexicon.

What determines the speed of speech recognition? Evidence from congenitally blind adults.

It is a matter of debate, whether and how improved auditory discrimination abilities enable speeded speech comprehension in congenitally blind adults. Previous research has concentrated on semantic and syntactic aspects of processing. Here we investigated phonologically mediated spoken word access processes by means of word onset priming. Blind adults and age- and gender-matched sighted adults listened to spoken word onsets (primes) followed by complete words (targets). Phonological overlap between primes and targets varied. Blind participants made faster lexical decision responses than sighted participants, yet their speeded responses were not restricted to phonologically overlapping trials. Furthermore, timing of Event Related Potential (ERP) results did not differ between blind and sighted participants. Together these results suggest that blind and sighted listeners are equally fast in implicit phonological encoding and lexical matching mechanisms. It appears that blind adults' speeded speech processing emerges when phonological analysis makes promising word candidates available for further processing. As one possible interpretation, we speculate that lexical selection processes in blind adults do not need to wait for information from the visual domain, while auditory-visual integration mechanisms are mandatorily implemented in speech recognition routines of sighted adults.

ERP evidence for implicit L2 word stress knowledge in listeners of a fixed-stress language.

Languages with contrastive stress, such as English or German, distinguish some words only via the stress status of their syllables, such as "CONtent" and "conTENT" (capitals indicate a stressed syllable). Listeners with a fixed-stress native language, such as Hungarian, have difficulties in explicitly discriminating variation of the stress position in a second language (L2). However, Event-Related Potentials (ERPs) indicate that Hungarian listeners implicitly notice variation from their native fixed-stress pattern. Here we used ERPs to investigate Hungarian listeners' implicit L2 processing. In a cross-modal word fragment priming experiment, we presented spoken stressed and unstressed German word onsets (primes) followed by printed versions of initially stressed and initially unstressed German words (targets). ERPs reflected stress priming exerted by both prime types. This indicates that Hungarian listeners implicitly linked German words with the stress status of the primes. Thus, the formerly described explicit stress discrimination difficulty associated with a fixed-stress native language does not generalize to implicit aspects of L2 word stress processing.

Not every pseudoword disrupts word recognition: an ERP study.

BACKGROUND: If all available acoustic phonetic information of words is used during lexical access and consequently stored in the mental lexicon, then all pseudowords that deviate in a single acoustic feature from a word should hamper word recognition. By contrast, models assuming underspecification of redundant phonological information in the mental lexicon predict a differential disruption of word recognition dependent on the phonological structure of the pseudoword. Using neurophysiological measures, the present study tested the predicted asymmetric disruption by assuming that coronal place of articulation for consonants is redundant. METHODS: Event-related potentials (ERPs) were recorded during a lexical decision task. The focus of interest was on word medial consonants. The crucial pseudowords were created by replacing the place of articulation of the medial consonant in German disyllabic words. We analyzed the differential temporal characteristics of the N400 pseudoword effect. RESULTS: N400 amplitudes for pseudowords were enhanced compared to words. As the uniqueness and deviation points differ for coronal and non-coronal items, the ERPs had to be correspondingly adjusted. The adjusted ERPs revealed that the N400 pseudoword effect starts earlier for coronal than for non-coronal pseudoword variants. Thus, non-coronal variants are accepted as words longer than the coronal variants. CONCLUSION: Our results indicate that lexical representations of words containing medial coronal consonants are initially activated by their corresponding non-coronal pseudowords. The most plausible explanation for the asymmetric neuronal processing of coronal and non-coronal pseudoword variants is an underspecified coronal place of articulation in the mental lexicon.

Neurophysiological correlates of mismatch in lexical access.

BACKGROUND: In the present study neurophysiological correlates related to mismatching information in lexical access were investigated with a fragment priming paradigm. Event-related brain potentials were recorded for written words following spoken word onsets that either matched (e.g., kan - Kante [Engl. edge]), partially mismatched (e.g., kan - Konto [Engl. account]), or were unrelated (e.g., kan - Zunge [Engl. tongue]). Previous psycholinguistic research postulated the activation of multiple words in the listeners' mental lexicon which compete for recognition. Accordingly, matching words were assumed to be strongly activated competitors, which inhibit less strongly activated partially mismatching words. RESULTS: ERPs for matching and unrelated control words differed between 300 and 400 ms. Difference waves (unrelated control words - matching words) replicate a left-hemispheric P350 effect in this time window. Although smaller than for matching words, a P350 effect and behavioural facilitation was also found for partially mismatching words. Minimum norm solutions point to a left hemispheric centro-temporal source of the P350 effect in both conditions. The P350 is interpreted as a neurophysiological index for the activation of matching words in the listeners' mental lexicon. In contrast to the P350 and the behavioural responses, a brain potential ranging between 350 and 500 ms (N400) was found to be equally reduced for matching and partially mismatching words as compared to unrelated control words. This latter effect might be related to strategic mechanisms in the priming situation. CONCLUSION: A left-hemispheric neuronal network engaged in lexical access appears to be gradually activated by matching and partially mismatching words. Results suggest that neural processing of matching words does not inhibit processing of partially mismatching words during early stages of lexical identification. Furthermore, the present results indicate that neurophysiological correlates observed in fragment priming reflect different aspects of target processing that are cumulated in behavioural responses. Particularly the left-hemispheric P350 difference potential appears to be closely related to fine-grained activation differences of modality-independent representations in the listeners' mental lexicon. This neurophysiological index might guide future studies aimed at investigating neural aspects of lexical access.

How space-number associations may be created in preliterate children: six distinct mechanisms.

The directionality of space-number association (SNA) is shaped by cultural experiences. It usually follows the culturally dominant reading direction. Smaller numbers are generally associated with the starting side for reading (left side in Western cultures), while larger numbers are associated with the right endpoint side. However, SNAs consistent with cultural reading directions are present before children can actually read and write. Therefore, these SNAs cannot only be shaped by the direction of children's own reading/writing behavior. We propose six distinct processes - one biological and five cultural/educational - underlying directional SNAs before formal reading acquisition: (i) Brain lateralization, (ii) Monitoring adult reading behavior, (iii) Pretend reading and writing, and rudimentary reading and writing skills, (iv) Dominant attentional directional preferences in a society, not directly related to reading direction, (v) Direct spatial-numerical learning, (vi) Other spatial-directional processes independent of reading direction. In this mini-review, we will differentiate between these processes, elaborate when in development they might emerge, discuss how they may create the SNAs observed in preliterate children and propose how they can be studied in the future.

Pitch modulates lexical identification in spoken word recognition: ERP and behavioral evidence.

Event-related potentials (ERPs) were recorded in cross-modal word fragment priming (CMWP) to address the function of pitch for the identification of spoken words. In CMWP fragments of spoken words (e.g., re taken from Regal [Engl. shelves]) are immediately followed by visual targets. Together with reduced reaction times (RTs), an ERP deflection named P350 has been found to be reduced for targets, which match the primes (e.g., in the prime-target pair re-REGAL) as compared to unrelated targets (e.g., re-WIRBEL [Engl. burble]). The P350 has been related to facilitated lexical identification [Friedrich, Kotz, Friederici and Gunter (in press), ERPs reflect lexical identification in word fragment priming, JOCN]. In the present study, we presented syllable primes with different pitch contours. One version of each prime bore a stressed pitch contour (e.g., re_1), the other an unstressed pitch contour (e.g., re_2). Primes were combined with targets being either stressed on the first syllable (e.g., REgel [Engl. rule]) or on the second syllable (e.g., reGAL [Engl. shelves]). We found a reduced amplitude of the P350 and slightly faster reactions for targets with a stress pattern that matched the pitch of the primes (e.g., re_1-REgel) as compared to targets with a stress pattern that did not match the pitch of the primes (e.g., re_1-reGAL). The present study replicates the P350 effect with different material, and indicates that pitch is used for lexical identification in spoken word recognition.

Phoneme-free prosodic representations are involved in pre-lexical and lexical neurobiological mechanisms underlying spoken word processing.

Recently we reported that spoken stressed and unstressed primes differently modulate Event Related Potentials (ERPs) of spoken initially stressed targets. ERP stress priming was independent of prime-target phoneme overlap. Here we test whether phoneme-free ERP stress priming involves the lexicon. We used German target words with the same onset phonemes but different onset stress, such as MANdel ("almond") and manDAT ("mandate"; capital letters indicate stress). First syllables of those words served as primes. We orthogonally varied prime-target overlap in stress and phonemes. ERP stress priming did neither interact with phoneme priming nor with the stress pattern of the targets. However, polarity of ERP stress priming was reversed to that previously obtained. The present results are evidence for phoneme-free prosodic processing at the lexical level. Together with the previous results they reveal that phoneme-free prosodic representations at the pre-lexical and lexical level are recruited by neurobiological spoken word recognition.

ERP correlates of word onset priming in infants and young children.

Using word onset priming with early learned words, we tracked access to phonological representations and predictive phonological processing at 6, 12, 18, and 24 months after birth. Event-Related Potentials (ERPs) were recorded while participants heard German word onsets (primes) followed by disyllabic spoken words (targets). Primes and target onsets were either congruent or incongruent (ma - Mama vs. so - Mama [Engl. 'mommy']). For an adult control group, ERP differences were found for the N100 complex, which has been related to abstract auditory analysis; and for the P350 deflection, which has been related to lexical access. A combined analysis of all infants and young children revealed an immature instance of an N100 effect, suggesting adult-like abstract speech sound processing. A central negativity effect, which had formerly been obtained when adults or older children were engaged in a lexical decision task, suggests that adult-like predictive phonological processing is available early in infancy. However, the absence of a P350-like effect in the infant data suggests that adult-like access to phonological forms is not established in the first two years of life. Taken together, ERPs recorded in word onset priming proved useful in investigating early phonological processing without an explicit behavioral measure.

Processing of syllable stress is functionally different from phoneme processing and does not profit from literacy acquisition.

Speech is characterized by phonemes and prosody. Neurocognitive evidence supports the separate processing of each type of information. Therefore, one might suggest individual development of both pathways. In this study, we examine literacy acquisition in middle childhood. Children become aware of the phonemes in speech at that time and refine phoneme processing when they acquire an alphabetic writing system. We test whether an enhanced sensitivity to phonemes in middle childhood extends to other aspects of the speech signal, such as prosody. To investigate prosodic processing, we used stress priming. Spoken stressed and unstressed syllables (primes) preceded spoken German words with stress on the first syllable (targets). We orthogonally varied stress overlap and phoneme overlap between the primes and onsets of the targets. Lexical decisions and Event-Related Potentials (ERPs) for the targets were obtained for pre-reading preschoolers, reading pupils and adults. The behavioral and ERP results were largely comparable across all groups. The fastest responses were observed when the first syllable of the target word shared stress and phonemes with the preceding prime. ERP stress priming and ERP phoneme priming started 200 ms after the target word onset. Bilateral ERP stress priming was characterized by enhanced ERP amplitudes for stress overlap. Left-lateralized ERP phoneme priming replicates previously observed reduced ERP amplitudes for phoneme overlap. Groups differed in the strength of the behavioral phoneme priming and in the late ERP phoneme priming effect. The present results show that enhanced phonological processing in middle childhood is restricted to phonemes and does not extend to prosody. These results are indicative of two parallel processing systems for phonemes and prosody that might follow different developmental trajectories in middle childhood as a function of alphabetic literacy.

Activation of words with phonological overlap.

Multiple lexical representations overlapping with the input (cohort neighbors) are temporarily activated in the listener's mental lexicon when speech unfolds in time. Activation for cohort neighbors appears to rapidly decline as soon as there is mismatch with the input. However, it is a matter of debate whether or not they are completely excluded from further processing. We recorded behavioral data and event-related brain potentials (ERPs) in auditory-visual word onset priming during a lexical decision task. As primes we used the first two syllables of spoken German words. In a carrier word condition, the primes were extracted from spoken versions of the target words (ano-ANORAK "anorak"). In a cohort neighbor condition, the primes were taken from words that overlap with the target word up to the second nucleus (ana-taken from ANANAS "pineapple"). Relative to a control condition, where primes and targets were unrelated, lexical decision responses for cohort neighbors were delayed. This reveals that cohort neighbors are disfavored by the decision processes at the behavioral front end. In contrast, left-anterior ERPs reflected long-lasting facilitated processing of cohort neighbors. We interpret these results as evidence for extended parallel processing of cohort neighbors. That is, in parallel to the preparation and elicitation of delayed lexical decision responses to cohort neighbors, aspects of the processing system appear to keep track of those less efficient word candidates.

Learning to read shapes the activation of neural lexical representations in the speech recognition pathway.

It has been demonstrated that written and spoken language processing are tightly linked. Here we focus on the development of this relationship at the time children start reading and writing. We hypothesize that the newly acquired knowledge about graphemes shapes lexical access in neural spoken word recognition. A group of preliterate children (six years old) and two groups of beginning readers (six and eight years old) were tested in a spoken word identification task. Using word onset priming we compared behavioural and neural facilitation for target words in identical prime-target pairs (e.g., mon-monster) and in prime target pairs that varied in the first speech sound (e.g., non-monster, Variation condition). In both groups of beginning readers priming was less effective in the Variation condition than in the Identity condition. This was indexed by less behavioural facilitation and enhanced P350 amplitudes in the event related potentials (ERPs). In the group of preliterate children, by contrast, both conditions did not differ. Together these results reveal that lexical access in beginning readers is based on more acoustic detail than lexical access in preliterate children. The results are discussed in the light of bidirectional speech and print interactions in readers.

Neural correlates of cross-modally induced changes in tactile awareness.

When a single tactile stimulus is presented together with two tones, participants often report perceiving two touches. It is a matter of debate whether this cross-modal effect of audition on touch reflects the interplay between modalities at early perceptual or at later processing stages, and which brain processes determine what in the end is consciously perceived. Event-related brain potentials (ERPs) were recorded while rare single tactile stimuli accompanied by two tones (1T2A) were presented among frequent tactile double stimuli accompanied by two tones (2T2A). Although participants were instructed to ignore the tones and to respond to single tactile stimuli only, they often failed to respond to 1T2A stimuli ("illusory double touches," 1T2A(i)). ERPs to "illusory double touches" versus "real double touches" (2T2A) differed 50 msec after the (missing) second touch. This suggests that at an early sensory stage, illusory and real touches are processed differently. On the other hand, although similar stimuli elicited a tactile mismatch negativity (MMN) between 100 and 200 msec in a unisensory tactile experiment, no MMN was observed for the 1T2A(i) stimuli in the multisensory experiment. "Tactile awareness" was associated with a negativity at 250 msec, which was enhanced in response to correctly identified deviants as compared to physically identical deviants that elicited an illusion. Thus, auditory stimuli seem to alter neural mechanisms associated with automatic tactile deviant detection. The present findings contribute to the debate of which processing step in the brain determines what is consciously perceived.

Electrophysiological indices of word fragment priming allow characterizing neural stages of speech recognition.

Spoken word onset syllables (prime fragments) have been used to track neurophysiological processing of following written words (targets). Between 300 and 400 ms event-related potentials (ERPs) over the left hemisphere were more positive for targets that did not match their preceding prime fragments (e.g., hun-dragon) compared to matching targets (e.g., dra-dragon). This P350 effect has been related to the activation of modality independent neural word form representations. In the present experiment we set out to characterize neural word processing specific to the auditory domain. Spoken word onset syllables (prime fragments) were followed by spoken words (targets). Reduced amplitudes for matching targets were found for the N100 and the T-complex (100-300 ms), for the P350 (300-400 ms) and for a central negativity starting at 300 ms. The early potentials possibly index the priming of speech sound processing. The P350 replicates previous work with written words. This constitutes further evidence for shared neural word form representations in auditory and visual word recognition. The central negativity might be related to the rapid phonological matching of prime and target; or to the immediate testing of phonological expectations in speech recognition.

Event-related potential correlates of negation in a sentence-picture verification paradigm.

In a sentence-picture verification paradigm, participants were presented in a rapid-serial-visual-presentation paradigm with affirmative or negative sentences (e.g., "In the front of the tower there is a/no ghost") followed by a matching or mismatching picture. Response latencies and event-related potentials (ERPs) were measured during reading and verification. An enhanced negative shift in the ERPs for the subject noun (i.e., "ghost") in negative, compared to affirmative sentences, was found during reading. We relate this ERP deflection to enhanced processing demands required by the negative particle no. Although this effect suggests a direct impact of negation on language processing, results for picture processing reveal that negation is not immediately integrated into sentence meaning. When the delay of picture presentation was short (250 msec), verification latencies and ERPs evoked by the picture showed a priming effect independent of whether the sentence contained a negation. Unprimed pictures (foreground object not mentioned in the sentence) led to longer latencies and higher N400 amplitudes than primed pictures (foreground object mentioned in the sentence). Main effects of negation showed up only in a late positive-going ERP effect. In contrast, when the delay was long (1500 msec), we observed main effects of truth value and negation in addition to the priming effect already in the N400 time window, that is, negation is fully integrated into sentence meaning only at a later point in the comprehension process. When negation has not yet been integrated, verification decisions appear to be modulated by additional time-consuming reanalysis processes.