Giordana Grossi

Phonological Processing in Visual Rhyming: A Developmental ERP Study

We employed a visual rhyming priming paradigm to characterize the development of brain systems important for phonological processing in reading. We studied 109 right-handed, native English speakers within eight age groups: 7-8, 9-10, 11-12, 13-14, 15-16, 17-18, 19-20, and 21-23. Participants decided whether two written words (prime-target) rhymed (JUICE-MOOSE) or not (CHAIR-MOOSE). In similar studies of adults, two main event-related potential (ERP) effects have been described: a negative slow wave to primes, larger over anterior regions of the left hemisphere and hypothesized to index rehearsal of the primes, and a negative deflection to targets, peaking at 400-450 msec, maximal over right temporal-parietal regions, larger for nonrhyming than rhyming targets, and hypothesized to index phonological matching. In this study, these two ERP effects were observed in all age groups; however, the two effects showed different developmental timecourses. On the one hand, the frontal asymmetry to primes increased with age; moreover, this asymmetry was correlated with reading and spelling scores, even after controlling for age. On the other hand, the distribution and onset of the more posterior rhyming effect (RE) were stable across age groups, suggesting that phonological matching relied on similar neural systems across these ages. Behaviorally, both reaction times and accuracy improved with age. These results suggest that different aspects of phonological processing rely on different neural systems that have different developmental timecourses.

Representation of Change: Separate Electrophysiological Markers of Attention, Awareness, and Implicit Processing

Awareness of change within a visual scene only occurs in the presence of focused attention. When two versions of a complex scene are presented in alternating sequence separated by a blank mask, unattended changes usually remain undetected, although they may be represented implicitly. To test whether awareness of change and focused attention had the same or separable neurophysiological substrates, and to search for the neural substrates of implicit representation of change, we recorded event-related brain potentials (ERPs) during a change blindness task. Relative to active search, focusing attention in the absence of a change enhanced an ERP component over frontal sites around 100300 msec after stimulus onset, and in posterior sites at the 150300 msec window. Focusing attention to the location of a change that subjects were aware of replicated those attentional effects, but also produced a unique positive deflection in the 350600 msec window, broadly distributed with its epicenter in mediocentral areas. The unique topography and time course of this latter modulation, together with its dependence on the aware perception of change, distinguishes this awareness of change electrophysiological response from the electrophysiological effects of focused attention. Finally, implicit representation of change elicited a distinct electrophysiological event: Unaware changes triggered a positive deflection at the 240300 msec window, relative to trials with no change. Overall, the present data suggest that attention, awareness of change, and implicit representation of change may be mediated by separate underlying systems.

A developmental investigation of ERP auditory rhyming effects

In a simple auditory rhyming paradigm requiring a button-press response (rhyme/nonrhyme) to the second word (target) of each spoken stimulus pair, both the early (P50, N120, P200, N240) and late (CNV, N400, P300) components of the ERP waveform evidenced considerable change from middle childhood to adulthood. In addition, behavioral accuracy and reaction time improved with increasing age. In contrast, the size, distribution and latency of each of several rhyming effects (including the posterior N400 rhyming effect, a left hemisphere anterior rhyming effect, and early rhyming effects on P50 latency, N120 latency and P200 amplitude) remained constant from age 7 to adulthood. These results indicate that the neurocognitive networks involved in processing auditory rhyme information, as indexed by the present task, are well established and have an adult-like organization at least by the age of 7.

Brain systems mediating semantic and syntactic processing in deaf native signers: Biological invariance and modality specificity

Studies of written and spoken language suggest that nonidentical brain networks support semantic and syntactic processing. Event-related brain potential (ERP) studies of spoken and written languages show that semantic anomalies elicit a posterior bilateral N400, whereas syntactic anomalies elicit a left anterior negativity, followed by a broadly distributed late positivity. The present study assessed whether these ERP indicators index the activity of language systems specific for the processing of aural-oral language or if they index neural systems underlying any natural language, including sign language. The syntax of a signed language is mediated through space. Thus the question arises of whether the comprehension of a signed language requires neural systems specific for this kind of code. Deaf native users of American Sign Language (ASL) were presented signed sentences that were either correct or that contained either a semantic or a syntactic error (1 of 2 types of verb agreement errors). ASL sentences were presented at the natural rate of signing, while the electroencephalogram was recorded. As predicted on the basis of earlier studies, an N400 was elicited by semantic violations. In addition, signed syntactic violations elicited an early frontal negativity and a later posterior positivity. Crucially, the distribution of the anterior negativity varied as a function of the type of syntactic violation, suggesting a unique involvement of spatial processing in signed syntax. Together, these findings suggest that biological constraints and experience shape the development of neural systems important for language.

ERP Nonword Rhyming Effects in Children and Adults

In a simple primetarget auditory rhyming event-related potential (ERP) paradigm with adults and 6-, 7-, and 8-year-old children, nonword stimuli (e.g., ninrin, kedvoo) were used to investigate neurocognitive systems involved in rhyming and their development across the early school years. Even absent semantic content, the typical CNV to primes and late rhyming effect (RE) to targets were evident in all age groups. The RE consisted of a more negative response to nonrhyming targets as compared to rhyming targets over posterior sites, with a reversal of this pattern at lateral anterior sites. The hypothesis that the CNV indexes phonological memory processes was not well supported by correlation analyses conducted with the ERP measures and scores on standardized behavioral tests. However, the onset of the rhyming effect was later in those scoring lower on phonological awareness measures.

Visual detection is gated by attending for action: Evidence from hemispatial neglect

We report observations in patients with visual extinction demonstrating that detection of visual events is gated by attention at the level of processing at which a stimulus is selected for action. In one experiment, three patients reported the identity of numerical words and digits presented either in the ipsilesional field, the contralesional field, or both fields. On the critical bilateral trials, extinction was greater when the competing items shared the same meaning and response, regardless of whether the items were visually different (e.g., ONE + 1), or identical (e.g., 1 + 1). A fourth patient was tested in a second experiment in which the competing items on bilateral trials were either different (e.g., ONE + TWO), identical (e.g., ONE + ONE) or homophones that were visually and semantically different but shared the same response (e.g., ONE + WON). Homophones and identical items caused similar extinction with less extinction occurring on different item trials.

Hemispheric specialization for sign language

Most studies on sign lateralization provide inconclusive results about the role of the two hemispheres in sign language processing, whereas the cases reported in the clinical literature show sign language impairment only following left hemisphere damage, suggesting a similar neural organization to spoken languages. By discriminating different levels of processing, a tachistoscopic study found that in deaf subjects matches of sign language handshapes based on equivalence of meaning are processed faster in the right visual field, thus demonstrating a left hemisphere superiority.

Posterior N1 asymmetry to English and Welsh words in Early and Late English–Welsh bilinguals

We investigated the lateralization of the posterior event-related potential (ERP) component N1 (120-170 ms) to written words in two groups of bilinguals. Fourteen Early English-Welsh bilinguals and 14 late learners of Welsh performed a semantic categorization task on separate blocks of English and Welsh words. In both groups, the N1 was strongly lateralized over the left posterior sites for both languages. A robust correlation was found between N1 asymmetry for English and N1 asymmetry for Welsh words in both groups. Furthermore, in Late Bilinguals, the N1 asymmetry for Welsh words increased with years of experience in Welsh. These data suggest that, in Late Bilinguals, the lateralization of neural circuits involved in written word recognition for the second language is associated to the organization for the first language, and that increased experience with the second language is associated to a larger functional cerebral asymmetry in favor of the left hemisphere.

Electrophysiological cross-language neighborhood density effects in late and early english-welsh bilinguals.

Behavioral studies with proficient late bilinguals have revealed the existence of orthographic neighborhood density (ND) effects across languages when participants read either in their first (L1) or second (L2) language. Words with many cross-language (CL) neighbors have been found to elicit more negative event-related potentials (ERPs) than words with few CL neighbors (Midgley et al., 2008); the effect started earlier, and was larger, for L2 words. Here, 14 late and 14 early English-Welsh bilinguals performed a semantic categorization task on English and Welsh words presented in separate blocks. The pattern of CL activation was different for the two groups of bilinguals. In late bilinguals, words with high CLND elicited more negative ERP amplitudes than words with low CLND starting around 175 ms after word onset and lasting until 500 ms. This effect interacted with language in the 300–500 ms time window. A more complex pattern of early effects was revealed in early bilinguals and there were no effects in the N400 window. These results suggest that CL activation of orthographic neighbors is highly sensitive to the bilinguals’ learning experience of the two languages.

Word and pseudoword superiority effects in Italian-English bilinguals ∗

Two indices of automatic orthographic processing, the word and pseudoword superiority effects, were explored in native Italian speakers familiar with English (late learners) and native English-speaking controls unfamiliar with Italian. Participants performed a forced-choice letter identification task with five categories of words: Italian words and pseudowords, English words and pseudowords, and nonwords. Native Italian speakers showed superiority effects for both languages, whereas English-speaking controls showed superiority effects only for English. These results suggest that orthographic processing can become automatic with extensive training in late bilinguals.