Electrophysiological correlates of cross-linguistic semantic integration in hearing signers:. N400 and LPC

We explored semantic integration mechanisms in native and non-native hearing users of sign language and non-signing controls. Event-related brain potentials (ERPs) were recorded while participants performed a semantic decision task for priming lexeme pairs. Pairs were presented either within speech or across speech and sign language. Target-related ERP responses were subjected to principal component analyses (PCA), and neurocognitive basis of semantic integration processes were assessed by analyzing the N400 and the late positive complex (LPC) components in response to spoken (auditory) and signed (visual) antonymic and unrelated targets. Semantically-related effects triggered across modalities would indicate a similar tight interconnection between the signers&#39; two languages like that described for spoken language bilinguals. Remarkable structural similarity of the N400 and LPC components with varying group differences between the spoken and signed targets were found. The LPC was the dominant response. The controls&#39; LPC differed from the LPC of the two signing groups. It was reduced to the auditory unrelated targets and was less frontal for all the visual targets. The visual LPC was more broadly distributed in native than non-native signers and was left-lateralized for the unrelated targets in the native hearing signers only. Semantic priming effects were found for the auditory N400 in all groups, but only native hearing signers revealed a clear N400 effect to the visual targets. Surprisingly, the non-native signers revealed no semantically-related processing effect to the visual targets reflected in the N400 or the LPC; instead they appeared to rely more on visual post-lexical analyzing stages than native signers. We conclude that native and non-native signers employed different processing strategies to integrate signed and spoken semantic content. It appeared that the signers&#39; semantic processing system was affected by group-specific factors like language background and/or usage.</p

Precursors to Natural Grammar Learning: Preliminary Evidence from 4-Month-Old Infants

When learning a new language, grammar—although difficult—is very important, as grammatical rules determine the relations between the words in a sentence. There is evidence that very young infants can detect rules determining the relation between neighbouring syllables in short syllable sequences. A critical feature of all natural languages, however, is that many grammatical rules concern the dependency relation between non-neighbouring words or elements in a sentence i.e. between an auxiliary and verb inflection as in is singing. Thus, the issue of when and how children begin to recognize such non-adjacent dependencies is fundamental to our understanding of language acquisition. Here, we use brain potential measures to demonstrate that the ability to recognize dependencies between non-adjacent elements in a novel natural language is observable by the age of 4 months. Brain responses indicate that 4-month-old German infants discriminate between grammatical and ungrammatical dependencies in auditorily presented Italian sentences after only brief exposure to correct sentences of the same type. As the grammatical dependencies are realized by phonologically distinct syllables the present data most likely reflect phonologically based implicit learning mechanisms which can serve as a precursor to later grammar learning

Sensory theories of developmental dyslexia: three challenges for research.

Recent years have seen the publication of a range of new theories suggesting that the basis of dyslexia might be sensory dysfunction. In this Opinion article, the evidence for and against several prominent sensory theories of dyslexia is closely scrutinized. Contrary to the causal claims being made, my analysis suggests that many proposed sensory deficits might result from the effects of reduced reading experience on the dyslexic brain. I therefore suggest that longitudinal studies of sensory processing, beginning in infancy, are required to successfully identify the neural basis of developmental dyslexia. Such studies could have a powerful impact on remediation.This is the accepted manuscript. The final version is available from NPG at http://www.nature.com/nrn/journal/v16/n1/abs/nrn3836.html

Auditory event-related potentials show altered hemispheric responses in dyslexia

Dyslexia is characterized by deficits in phonological processing abilities. However, it is unclear what the underlying factors for poor phonological abilities or speech sound representations are. One hypothesis suggests that individuals with dyslexia have problems in basic acoustic perception which in turn can also cause problems in speech perception. Here basic auditory processing was assessed by auditory event-related potentials recorded for paired tones presented in an oddball paradigm in 9-year-old children with dyslexia and a familial background of dyslexia, typically reading children at familial risk for dyslexia and control children without risk for dyslexia. The tone pairs elicited a P1-N250 complex with emerging N1-P2 complex. Control children showed larger responses over the left-than-right hemisphere at the P1 and P2 time windows for both short and long within-pair intervals (WPI; 10 and 255 ms) whereas children with dyslexia showed this pattern only for the tone pairs with the long WPI. The response for the pairs with the short WPI showed equal amplitudes over both hemispheres in children with dyslexia. The findings indicate that individuals with dyslexia process basic auditory information differently when the tones are within the temporal window of integration. (C) 2011 Elsevier Ireland Ltd. All rights reserved

The Comprehensive Test of Phonological Processing: examiner&apos;s manual

BACKGROUND Categorical perception for speech sounds has been demonstrated as early as infancy METHODS • Subjects • Thirty-one typically developing, right-handed, monolingual, English speaking children with normal hearing. • Neuropsychological Testing • • The phonemic (P) items consist of an 8-token continuum from /ba/ to /da/. The anchor points were synthesized using pitch, intensity, formant bandwidth and formant center frequency parameters derived from natural utterances of the syllables. The F2 transition varies continuously from a low initial value and rising slope characteristic of /ba/ continuously to a high initial value and falling slope characteristic of /da/. • The anchor points of the nonphonemic (N) continuum were created by spectrally inverting the first formants of the anchor points of the P continuum in order to disrupt their phonetic value without altering their general spectrotemporal characteristics. The spectra of the transition segment of F1 and of the steady state segment of F1 were rotated each around their mean frequency and then the segments were reconnected by lowering the rotated steady-state segment by 100 Hz. • FMRI Task • The task involves a 2-alternative forced-choice AX discrimination. The distance in acoustic space between the tokens in each pair is identical, but, for P items, two token-pairs fall within a phonemic category (1-3, 5-7) and one crosses the phonemic category boundary (3-5). • P and N stimuli were presented in alternating runs. Each run contained five discrimination pairs. Children aged 7-9 years completed four runs and those aged 10-12 completed six runs. • Categorical Perception Index (CPI) • The average percentage of within-category P items perceived as different was subtracted from the percentage of across-category P items perceived as different. The sample was divided into a Low CPI group (&lt;70; n=14) and a High CPI group (&gt;75; n=17). • Image Acquisition Functional Data Anatomical Data 3T GE Signa scanner, T2*-weighted GE-EPI 3D SPGR, T1-weighted 36 axial slices with 0.5 mm gap 106 axial slices TE=25ms, voxels=3.44 x 3.44 x 3.0(+0.5mm gap) voxels=0.9x1.0x1.2mm 3 Clustered Acquisition, TR=7s, Acquisition Time=2s AX discrimination performance as shown in The Low and High CPI groups did not significantly differ with regard to age, sex, or neuropsychological performance. Spearman&apos;s rho correlations between the CPI and the neuropsychological measures were not significant for the full group or the High CPI group. In the Low CPI group, the CPI was significantly correlated with reading performance (ρ =.60, p&lt;.05), and the correlation between this index and Elision (a measure of phonological awareness approached significance (ρ=.52, p&lt;.06). FMRI Results For the full sample, P compared with rest was associated with strong activation along the left STG/STS, with a smaller focus seen in the homologous right region. In addition, significant activation was seen in the left middle frontal gyrus (MFG), bilateral inferior frontal gyrus (IFG; L&gt;R), and bilateral pre-and postcentral gyri (R&gt;L). For the N condition contrasted with rest, the IFG, STG/STS, and pre-and post-central gyri activation was significantly greater on the right. Right MFG and posterior MTG activation was also observed. The direct contrast of the P and NP conditions revealed multiple areas of greater activation during P in the left prefrontal cortex and left STG and several areas of greater activation in the right posterior cortex during NP. DISCUSSION Similar to previous findings in adults A novel and unexpected finding was the greater right lateralization with nonphonemic sounds than observed in previous studies with adults. The extent of this lateralization differed depending on the degree of categorical discrimination exhibited for phonemic sounds. Specifically, the group of Low CPI subjects exhibited more activation of left frontotemporal regions during nonphonemic perception than the High CPI group. The High CPI group activated these same regions predominantly during speech perception. These results suggest that, in childhood, greater specialization of this left frontotemporal network for the categorical perception of speech sounds may be important for the appropriate refinement of this ability. Importantly, the pattern of performance on the AX task observed in the Low CPI group is highly similar to that frequently reported in dyslexi

The Comprehensive Test of Phonological Processing: examiner&apos;s manual

BACKGROUND Categorical perception for speech sounds has been demonstrated as early as infancy METHODS • Subjects • Thirty-one typically developing, right-handed, monolingual, English speaking children with normal hearing. • Neuropsychological Testing • • The phonemic (P) items consist of an 8-token continuum from /ba/ to /da/. The anchor points were synthesized using pitch, intensity, formant bandwidth and formant center frequency parameters derived from natural utterances of the syllables. The F2 transition varies continuously from a low initial value and rising slope characteristic of /ba/ continuously to a high initial value and falling slope characteristic of /da/. • The anchor points of the nonphonemic (N) continuum were created by spectrally inverting the first formants of the anchor points of the P continuum in order to disrupt their phonetic value without altering their general spectrotemporal characteristics. The spectra of the transition segment of F1 and of the steady state segment of F1 were rotated each around their mean frequency and then the segments were reconnected by lowering the rotated steady-state segment by 100 Hz. • FMRI Task • The task involves a 2-alternative forced-choice AX discrimination. The distance in acoustic space between the tokens in each pair is identical, but, for P items, two token-pairs fall within a phonemic category (1-3, 5-7) and one crosses the phonemic category boundary (3-5). • P and N stimuli were presented in alternating runs. Each run contained five discrimination pairs. Children aged 7-9 years completed four runs and those aged 10-12 completed six runs. • Categorical Perception Index (CPI) • The average percentage of within-category P items perceived as different was subtracted from the percentage of across-category P items perceived as different. The sample was divided into a Low CPI group (&lt;70; n=14) and a High CPI group (&gt;75; n=17). • Image Acquisition Functional Data Anatomical Data 3T GE Signa scanner, T2*-weighted GE-EPI 3D SPGR, T1-weighted 36 axial slices with 0.5 mm gap 106 axial slices TE=25ms, voxels=3.44 x 3.44 x 3.0(+0.5mm gap) voxels=0.9x1.0x1.2mm 3 Clustered Acquisition, TR=7s, Acquisition Time=2s AX discrimination performance as shown in The Low and High CPI groups did not significantly differ with regard to age, sex, or neuropsychological performance. Spearman&apos;s rho correlations between the CPI and the neuropsychological measures were not significant for the full group or the High CPI group. In the Low CPI group, the CPI was significantly correlated with reading performance (ρ =.60, p&lt;.05), and the correlation between this index and Elision (a measure of phonological awareness approached significance (ρ=.52, p&lt;.06). FMRI Results For the full sample, P compared with rest was associated with strong activation along the left STG/STS, with a smaller focus seen in the homologous right region. In addition, significant activation was seen in the left middle frontal gyrus (MFG), bilateral inferior frontal gyrus (IFG; L&gt;R), and bilateral pre-and postcentral gyri (R&gt;L). For the N condition contrasted with rest, the IFG, STG/STS, and pre-and post-central gyri activation was significantly greater on the right. Right MFG and posterior MTG activation was also observed. The direct contrast of the P and NP conditions revealed multiple areas of greater activation during P in the left prefrontal cortex and left STG and several areas of greater activation in the right posterior cortex during NP. DISCUSSION Similar to previous findings in adults A novel and unexpected finding was the greater right lateralization with nonphonemic sounds than observed in previous studies with adults. The extent of this lateralization differed depending on the degree of categorical discrimination exhibited for phonemic sounds. Specifically, the group of Low CPI subjects exhibited more activation of left frontotemporal regions during nonphonemic perception than the High CPI group. The High CPI group activated these same regions predominantly during speech perception. These results suggest that, in childhood, greater specialization of this left frontotemporal network for the categorical perception of speech sounds may be important for the appropriate refinement of this ability. Importantly, the pattern of performance on the AX task observed in the Low CPI group is highly similar to that frequently reported in dyslexi