Brain potentials in a phonological matching task using Chinese characters

An ERP Study on the Role of Phonological Processing in Reading Two-Character Compound Chinese Words of High and Low Frequency

Unlike in English, the role of phonology in word recognition in Chinese is unclear. In this event-related potential experiment, we investigated the role of phonology in reading both high- and low-frequency two-character compound Chinese words. Participants executed semantic and homophone judgment tasks of the same precede-target pairs. Each pair of either high- or low-frequency words were either unrelated (control condition) or related semantically or phonologically (homophones). The induced P200 component was greater for low- than for high-frequency word-pairs both in semantic and phonological tasks. Homophones in the semantic judgment task and semantically-related words in the phonology task both elicited a smaller N400 than the control condition, word frequency-independently. However, for low-frequency words in the phonological judgment task, it was found that the semantically related pairs released a significantly larger P200 than the control condition. Thus, the semantic activation of both high- and low-frequency words may be no later than phonological activation.

Seriality of semantic and phonological processes during overt speech in Mandarin as revealed by event-related brain potentials

How is information transmitted across semantic and phonological levels in spoken word production? Recent evidence from speakers of Western languages such as English and Dutch suggests non-discrete transmission, but it is not clear whether this view can be generalized to other languages such as Mandarin, given potential differences in phonological encoding across languages. The present study used Mandarin speakers and combined a behavioral picture-word interference task with event-related potentials. The design factorially crossed semantic and phonological relatedness. Results showed semantic and phonological effects both in behavioral and electrophysiological measurements, with statistical additivity in latencies, and discrete time signatures (250-450 ms and 450-600 ms after picture onset for the semantic and phonological condition, respectively). Overall, results suggest that in Mandarin spoken production, information is transmitted from semantic to phonological levels in a sequential fashion. Hence, temporal signatures associated with spoken word production might differ depending on target language.

An ERP study of Chinese speakers' rhyme judgments to Chinese and English words

Event-related potential studies of rhyme judgments in alphabetic languages show that nonrhyming word pairs elicit a larger negative-going wave peaking at 450 ms after stimulus onset than rhyming word pairs. We use Chinese characters to explore the extent to which this N450 rhyming effect reflects phonological processing. Using Chinese characters provides an advantage over alphabetic scripts because rhyming characters can have nonoverlapping orthographic forms, something not possible in alphabetic scripts. We recorded event-related potentials when the Chinese speakers made rhyme judgments to Chinese and English words. An N450 effect was observed in both the languages. Moreover, the N450 effects exhibited in the two languages were correlated. The results support the phonological account of the N450 effect and indicate that similar phonological operations are involved in different languages.

P200 and phonological processing in Chinese word recognition

The present study examined the relationship between P200 and phonological processing in Chinese word recognition. Participants did a semantic judgment task on pairs of words. The critical pairs were all semantically unrelated in one of three conditions: homophonic, rhyme, or phonologically unrelated. Noting the possibility that P200 may be affected by phonological similarity and orthographic similarity and that literature studies may not have assessed such effects separately, the present study used visually dissimilar word pairs sharing no phonetic radicals. Relative to the control pairs, both the homophonic and rhyme pairs elicited a significantly larger P200 with a scalp distribution centering at the centro-parietal areas. The results present strong evidence that P200 can be modulated by lexical phonology alone, independent of sub-lexical phonology, or lexical or sub-lexical orthography. P200 effects were comparable in amplitude and topography between the homophonic and the rhyme conditions, suggesting that P200 is sensitive to phonology at both the syllabic and the sub-syllabic levels.

Assessing effects of viewing distance on normal Chinese reading: some methodological and theoretical implications

Viewing distance determines a range of factors affecting reading performance. Previous studies of Chinese-character reading have shown considerable disagreement and inconsistency in their choice of viewing distances, however, with obvious implications for research in this area. The present study aimed to resolve this issue by determining the optimal viewing distance for studies of normal Chinese reading. Stimuli were pages of text that were composed of a standard Chinese typeface (Song) that was presented in a standard size (10.5 pt). Forty reading distances were used, ranging from 2.5 to 100.0 cm. Distances within the range of 7.5-55.0 cm produced faster reading rates than did the distances at either end of the continuum, and a regression model showed that 35 cm was the optimal viewing distance. These findings indicate an optimal range of retinal image sizes between 2.0 degrees and 0.3 degrees per character. The implications of these findings for understanding the processes that are involved in Chinese reading and for the appropriate presentation of Chinese stimuli in experiments are discussed.

An ERP study on the time course of phonological and semantic activation in Chinese word recognition

With the event-related potential (ERP) technique, we examined the time course of phonological and semantic activation in Chinese word recognition. Participants did a semantic judgment task and a homophone judgment task over the same set of word pairs. Each pair was of either high or low word frequency and the two words were either unrelated or related semantically or phonologically, i.e., being homophones. For high-frequency words, both the semantically related pairs in the homophone task and the homophonic pairs in the semantic task elicited ERP responses different from the unrelated control pairs in the N400 component but not any component earlier, suggesting a similar time course for semantic and phonological activation. For low-frequency words, the semantically related pairs in the homophone task were associated with a similar modulation of N400. However, compared to the unrelated controls, the homophonic pairs in the semantic task elicited a larger P200, a component implicated in phonological processing in the literature, and thus demonstrated a phonological activation earlier than semantic activation. The results showed that word frequency affects the time course of semantic and phonological activation suggesting that phonology is not invariably activated before semantics in Chinese word recognition.

Orthographic and phonological processing in Chinese dyslexic children: An ERP study on sentence reading

An event-related potential (ERP) experiment was conducted to explore the differences between Chinese-speaking dyslexic children and normal school children in orthographic and phonological processing during Chinese sentence reading. Participants were visually presented with sentences, word-by-word and were asked to judge whether the sentences were semantically acceptable. The crucial manipulation was on the sentence-final two-character compound words, which were either correct or incorrect. For the incorrect compounds, the second characters of the base words were replaced by homophonic or orthographically similar characters. It was found that, for the normal controls, the orthographic and phonological mismatches elicited more negative ERP responses, relative to the baseline, over a relatively long time course (including the time windows for P200 and N400) at the central-posterior scalp regions. In contrast, the dyslexic children in general showed no differences between experimental conditions for P200 and N400, although the more detailed time course analyses did reveal some weak effects for the N400 component between experimental conditions. In addition, the mean amplitude of N400 in the homophonic condition was less negative-going for the dyslexics than for the controls. These findings suggest that Chinese dyslexic children have deficits in processing orthographic and phonological information conveyed by characters and, compared with normal children, they rely more on phonological information to access lexical semantics in sentence reading.

Interplay between computational models and cognitive electrophysiology in visual word recognition

In this article, we discuss the relevance of electrophysiological data to the enterprise of analyzing and understanding the reading process. Specifically, we detail how the event-related brain potential (ERP) technique (and its magnetic counterpart) can aid in development of models of visual word recognition. Any viable and accurate account of reading must take into account the temporal and anatomical constraints imposed by the fact that reading is a human brain function. We believe that neurophysiological (especially, although not limited to electrophysiological) data can serve an essential reference in the development of biologically realistic models of reading. We assess just how well extant electrophysiological data comport with specific predictions of existing computational models and offer some suggestions for the kinds of research that can address some of the remaining open questions.

Electrophysiological correlates of grapheme-phoneme conversion

The cortical processes underlying grapheme-phoneme conversion were investigated by event-related potentials (ERPs). The task consisted of silent reading or vowel-matching of three Japanese hiragana characters, each representing a consonant-vowel syllable. At earlier latencies, typical components of the visual ERP, namely, P1 (110 ms), N1 (170 ms) and P2 (300 ms), were elicited in the temporo-occipital area for both tasks as well as control task (observing the orthographic shapes of three Korean characters). Following these earlier components, two sustained negativities were identified. The earlier sustained negativity, referred here to as SN1, was found in both the silent-reading and vowel-matching task but not in the control task. The scalp distribution of SN1 was over the left occipito-temporal area, with maximum amplitude over O1. The amplitude of SN1 was larger in the vowel-matching task compared to the silent-reading task, consistent with previous reports that ERP amplitude correlates with task difficulty. SN2, the later sustained negativity, was only observed in the vowel-matching task. The scalp distribution of SN2 was over the midsagittal centro-parietal area with maximum amplitude over Cz. Elicitation of SN2 in the vowel-matching task suggested that the vowel-matching task requires a wider range of neural activities exceeding the established conventional area of language processing.

Different scalp topography of brain potentials related to expression and identity matching of faces

Event-related potentials (ERPs) and behavioral data were recorded while subjects performed two tasks on the same set of faces (presented in pairs). One task was identity matching and the other expression matching. Two groups of subjects participated, one familiar and the other unfamiliar with the faces. Subjects were less accurate in matching expressions than identity. Familiarity facilitated identity but not expression matching. ERPs to mismatches in both tasks elicited a negativity around 400 ms, which was similar in latency and amplitude in the two tasks, but differed in scalp topography. Whereas the mismatch negativity had the same landscape over the left hemisphere for both tasks, the component related to expression had larger amplitudes over the right-temporal regions. Familiarity had no effect on these negativities, although it affected a late positivity (LP). These results support the idea of distinct neural systems subserving face processing, and agree with a role of the right hemisphere for the processing of emotional expressions.

Phonological and orthographic processing of Hebrew words: electrophysiological aspects

Brain activity among 15 male, college-level, normal readers in Israel was examined during phonological and orthographic word-recognition tasks. Both electrophysiological (event-related potentials, or ERPs) and behavioral measures were obtained. Data indicated that (a) behavioral accuracy was almost perfect for all the experimental tasks, and (b) although P200 and N400 ERP components were elicited in the experimental tasks, the latencies of those components were significantly longer and their amplitudes significantly higher in the phonological task. Variations in vowel information had no effect on word recognition in either type of task. The results suggest that among skilled readers of Hebrew, phonological processing during word recognition may be more effortful and may demand greater cognitive resources than orthographic processing. Furthermore, the additional phonological information represented in vowels appears to contribute little to word recognition in this population. These findings support earlier research on skilled reading in Hebrew as well as current theoretical models of reading.