Emergence of representations through repeated training on pronouncing novel letter combinations leads to efficient reading.

Printed text can be decoded by utilizing different processing routes depending on the familiarity of the script. A predominant use of word-level decoding strategies can be expected in the case of a familiar script, and an almost exclusive use of letter-level decoding strategies for unfamiliar scripts. Behavioural studies have revealed that frequently occurring words are read more efficiently, suggesting that these words are read in a more holistic way at the word-level, than infrequent and unfamiliar words. To test whether repeated exposure to specific letter combinations leads to holistic reading, we monitored both behavioural and neural responses during novel script decoding and examined changes related to repeated exposure. We trained a group of Dutch university students to decode pseudowords written in an unfamiliar script, i.e., Korean Hangul characters. We compared behavioural and neural responses to pronouncing trained versus untrained two-character pseudowords (equivalent to two-syllable pseudowords). We tested once shortly after the initial training and again after a four days' delay that included another training session. We found that trained pseudowords were pronounced faster and more accurately than novel combinations of radicals (equivalent to letters). Imaging data revealed that pronunciation of trained pseudowords engaged the posterior temporo-parietal region, and engagement of this network was predictive of reading efficiency a month later. The results imply that repeated exposure to specific combinations of graphemes can lead to emergence of holistic representations that result in efficient reading. Furthermore, inter-individual differences revealed that good learners retained efficiency more than bad learners one month later.

Training-induced neural plasticity in visual-word decoding and the role of syllables.

To investigate the neural underpinnings of word decoding, and how it changes as a function of repeated exposure, we trained Dutch participants repeatedly over the course of a month of training to articulate a set of novel disyllabic input strings written in Greek script to avoid the use of familiar orthographic representations. The syllables in the input were phonotactically legal combinations but non-existent in the Dutch language, allowing us to assess their role in novel word decoding. Not only trained disyllabic pseudowords were tested but also pseudowords with recombined patterns of syllables to uncover the emergence of syllabic representations. We showed that with extensive training, articulation became faster and more accurate for the trained pseudowords. On the neural level, the initial stage of decoding was reflected by increased activity in visual attention areas of occipito-temporal and occipito-parietal cortices, and in motor coordination areas of the precentral gyrus and the inferior frontal gyrus. After one month of training, memory representations for holistic information (whole word unit) were established in areas encompassing the angular gyrus, the precuneus and the middle temporal gyrus. Syllabic representations also emerged through repeated training of disyllabic pseudowords, such that reading recombined syllables of the trained pseudowords showed similar brain activation to trained pseudowords and were articulated faster than novel combinations of letter strings used in the trained pseudowords.

Aberrant N400 responses to phonological overlap during rhyme judgements in children at risk for dyslexia.

It is widely accepted that dyslexia is associated with difficulties in phonological awareness and that rhyme awareness in young children can predict later reading success. However, little is known regarding the underlying phonological mechanisms of rhyme awareness in dyslexia, as rhyme awareness is typically assessed using explicit behavioural measures that represent only the endpoint of processing and often lack phonological distracters. We examined event-related potentials (ERPs) in response to auditory word pairs that differed in phonological overlap during a rhyme judgement task given to 6-year-old beginning readers who were at risk for dyslexia (n=30) and typical-reading age-matched controls (n=29). ERPs were recorded in response to word pairs with various types of phonological overlap, including rhyming (e.g., wall-ball), non-rhyming overlapping (e.g., bell-ball) and non-rhyming unrelated (e.g., sock-ball) word pairs. Both groups of participants exhibited N400 responses for basic rhyme judgements vs. unrelated targets. In the typical-reading controls, the neural responses also differed between the rhyming targets and the non-rhyming overlapping targets, whereas neural responses to these targets were similar in the group of children at risk for dyslexia, indicating difficulties in their ability to process similar-sounding, non-rhyming targets. These findings suggest that typical-reading children solve the rhyme judgement task using a more analytical approach, whereas children who are at risk for dyslexia base their judgments on a comparison of overall sound similarity.

The neural correlates of rhyme awareness in preliterate and literate children.

OBJECTIVE: Most rhyme awareness assessments do not encompass measures of the global similarity effect (i.e., children who are able to perform simple rhyme judgments get confused when presented with globally similar non-rhyming pairs). The present study examines the neural nature of this effect by studying the N450 rhyme effect. METHODS: Behavioral and electrophysiological responses of Dutch pre-literate kindergartners and literate second graders were recorded while they made rhyme judgments of word pairs in three conditions; phonologically rhyming (e.g., wijn-pijn), overlapping non-rhyming (e.g., pen-pijn) and unrelated non-rhyming pairs (e.g., boom-pijn). RESULTS: Behaviorally, both groups had difficulty judging overlapping but not rhyming and unrelated pairs. The neural data of second graders showed overlapping pairs were processed in a similar fashion as unrelated pairs; both showed a more negative deflection of the N450 component than rhyming items. Kindergartners did not show a typical N450 rhyme effect. However, some other interesting ERP differences were observed, indicating preliterates are sensitive to rhyme at a certain level. SIGNIFICANCE: Rhyme judgments of globally similar items rely on the same process as rhyme judgments of rhyming and unrelated items. Therefore, incorporating a globally similar condition in rhyme assessments may lead to a more in-depth measure of early phonological awareness skills.

The nature of rhyme processing in preliterate children.

BACKGROUND: Rhyme awareness is one of the earliest forms of phonological awareness to develop and is assessed in many developmental studies by means of a simple rhyme task. The influence of more demanding experimental paradigms on rhyme judgment performance is often neglected. Addressing this issue may also shed light on whether rhyme processing is more global or analytical in nature. AIMS: The aim of the present study was to examine whether lexical status and global similarity relations influenced rhyme judgments in kindergarten children and if so, if there is an interaction between these two factors. SAMPLE: Participants were 41 monolingual Dutch-speaking preliterate kindergartners (average age 6.0 years) who had not yet received any formal reading education. METHOD: To examine the effects of lexical status and phonological similarity processing, the kindergartners were asked to make rhyme judgements on (pseudo) word targets that rhymed, phonologically overlapped or were unrelated to (pseudo) word primes. RESULTS: Both a lexicality effect (pseudo-words were more difficult than words) and a global similarity effect (globally similar non-rhyming items were more difficult to reject than unrelated items) were observed. In addition, whereas in words the global similarity effect was only present in accuracy outcomes, in pseudo-words it was also observed in the response latencies. Furthermore, a large global similarity effect in pseudo-words correlated with a low score on short-term memory skills and grapheme knowledge. CONCLUSIONS: Increasing task demands led to a more detailed assessment of rhyme processing skills. Current assessment paradigms should therefore be extended with more demanding conditions. In light of the views on rhyme processing, we propose that a combination of global and analytical strategies is used to make a correct rhyme judgment.

A neurocognitive perspective on rhyme awareness: the N450 rhyme effect.

Rhyme processing is reflected in the electrophysiological signals of the brain as a negative deflection for non-rhyming as compared to rhyming stimuli around 450 ms after stimulus onset. Studies have shown that this N450 component is not solely sensitive to rhyme but also responds to other types of phonological overlap. In the present study, we examined whether the N450 component can be used to gain insight into the global similarity effect, indicating that rhyme judgment skills decrease when participants are presented with word pairs that share a phonological overlap but do not rhyme (e.g., bell-ball). We presented 20 adults with auditory rhyming, globally similar overlapping and unrelated word pairs. In addition to measuring behavioral responses by means of a yes/no button press, we also took EEG measures. The behavioral data showed a clear global similarity effect; participants judged overlapping pairs more slowly than unrelated pairs. However, the neural outcomes did not provide evidence that the N450 effect responds differentially to globally similar and unrelated word pairs, suggesting that globally similar and dissimilar non-rhyming pairs are processed in a similar fashion at the stage of early lexical access.

Neural representation of navigational relevance is rapidly induced and long lasting.

Successful navigation is facilitated by the presence of landmarks. Previous functional magnetic resonance imaging (fMRI) evidence indicated that the human parahippocampal gyrus automatically distinguishes between landmarks placed at navigationally relevant (decision points) and irrelevant locations (nondecision points). This storage of navigational relevance can provide a neural mechanism underlying successful navigation. However, an efficient wayfinding mechanism requires that important spatial information is learned quickly and maintained over time. The present study investigates whether the representation of navigational relevance is modulated by time and practice. Participants learned 2 film sequences through virtual mazes containing objects at decision and at nondecision points. One maze was shown one time, and the other maze was shown 3 times. Twenty-four hours after study, event-related fMRI data were acquired during recognition of the objects. The results showed that activity in the parahippocampal gyrus was increased for objects previously placed at decision points as compared with objects placed at nondecision points. The decision point effect was not modulated by the number of exposures to the mazes and independent of explicit memory functions. These findings suggest a persistent representation of navigationally relevant information, which is stable after only one exposure to an environment. These rapidly induced and long-lasting changes in object representation provide a basis for successful wayfinding.