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Effects of word form on brain processing of written Chinese.

Both logographic characters and alphabetic pinyins can be used to write words in Chinese. Here we use fMRI to address the question of whether the written form affects brain processing of a word. Fifteen healthy, right-handed, native Chinese-reading volunteers participated in our study and were asked to read silently either Chinese characters (8 subjects) or pinyins (7 subjects). The stimulus presentation rate was varied for both tasks to allow us to identify brain regions with word-load-dependent activation. Rate effects (fast minus slow presentations) for Chinese character reading were observed in striate and extrastriate visual cortex, superior parietal lobule, left posterior middle temporal gyrus, bilateral inferior temporal gyri, and bilateral superior frontal gyri. Rate effects for pinyin reading were observed in bilateral fusiform, lingual, and middle occipital gyri, bilateral superior parietal lobule/precuneus, left inferior parietal lobule, bilateral inferior temporal gyrus, left middle temporal gyrus, and left superior temporal gyrus. These results demonstrate that common regions of the brain are involved in reading both Chinese characters and pinyins, activated apparently independently of the surface form of the word. There also appear to be brain regions in which activation is dependent on word form. However, it is unlikely that these are entirely specific for a given word form; their activation more likely reflects relative functional specializations within broader networks for processing written language.

Adult↗

SPEAKERS' AND LISTENERS' PROCESSES IN A WORD-COMMUNICATION TASK.

A communication task was developed to investigate the processes by which a speaker selects verbal clues in order to distinguish one word (referent) from another (nonreferent) and the processes by which a listener identifies the speaker's referent word. Data from speakers and listeners in this task were linked to word-association norms by means of a stochastic model.

Auditory Perception↗

Neural basis of the non-attentional processing of briefly presented words.

The neural basis of the automatic activation of words was investigated in an fMRI study. In the study, words were presented briefly (51 or 151 msec) followed by a mask. To prevent attentional processing, subjects attended to the masks and not the words, and were required to make perceptual judgment about the masks. We found that a distributed neural network (including the frontal, temporal, occipital, parietal lobes, and the cerebellum) was activated during non-attentional processing of words in both exposure durations. A significant main effect of presentation duration was found in bilateral cerebellum and the right fusiform gyrus, suggesting their role in the later (151 msec) processing of words. In addition, a significant interaction between presentation duration and word frequency was obtained. When the presentation duration was 151 msec, no significant difference in activation was found between high- and low-frequency words. Alternatively, when the presentation duration was 51 msec, high-frequency words evoked significantly greater activation in bilateral fusiform gyri, cerebellum, right inferior parietal lobe, medial frontal gyrus (BA 45/46/9), and the right temporal-occipital junction (BA 21/37). These results suggest that these regions are sensitive to word frequency, and are related to both the attentional and non-attentional access of lexical representations.

Adolescent↗

Dissociation of conscious and unconscious repetition priming effect on event-related potentials.

Although the neural basis of the unconscious priming effect has previously been investigated, the results of these studies have possibly been contaminated by a conscious priming effect. The aim of the present study was to dissociate the effects of conscious and unconscious priming on event-related potential (ERP) by using the process-dissociation procedure. A prime word was presented briefly, followed by a word-stem, in each trial. Under the inclusion condition, subjects were instructed to complete the word-stem using the prime word, while under the exclusion condition subjects were asked to complete the word-stem with a word not seen as prime. The behavioral priming effect was obtained under both conditions, indicating that the prime words were processed unconsciously and influenced the word-stem completion task. We found that two ERP components were affected by repetition priming. First, the N400 amplitude was decreased by word repetition under the inclusion condition, but not under the exclusion condition. This result suggests that N400 would reflect conscious lexical processing, but not unconscious lexical activation. Second, the negativity at left front lateral region was enhanced by word repetition under the exclusion condition. We discuss this finding herein in relation to the activity of the left inferior prefrontal cortex with regard to word semantic processing.

Adolescent↗

A positron emission tomographic study of impaired word recognition and phonological processing in dyslexic men.

BACKGROUND: Developmental dyslexia is characterized by impaired word recognition, which is thought to result from deficits in phonological processing. Improvements during the course of development are thought to disproportionately involve orthographic components of reading; phonological deficits persist into adulthood. OBJECTIVE: To localize the neural correlates of impaired word recognition and phonological processing in men with developmental dyslexia. METHODS: Regional cerebral blood flow was measured with oxygen 15 positron emission tomography in 17 men with dyslexia and in 14 matched controls during the performance of phonological and orthographic tasks--pronunciation (reading aloud) and lexical decision making--designed to activate posterior and anterior perisylvian cortices, respectively. RESULTS: Altered patterns of activation (reduced activation, unusual deactivation) were seen in dyslexic men in mid- to posterior temporal cortex bilaterally and in inferior parietal cortex, predominantly on the left, during both pronunciation and decision making. In contrast, dyslexic men demonstrated essentially normal activation of left inferior frontal cortex during both phonological and orthographic decision making. CONCLUSION: These, along with prior findings, are compatible with a hypothesis of bilateral involvement of posterior temporal and parietal cortices in dyslexia.

Adolescent↗

Word and non-word reading: what role for the Visual Word Form Area?

The putative role of the so-called Visual Word Form Area (VWFA) during reading remains under debate. For some authors, this region is specifically involved in a pre-lexical processing of words and pseudowords, whereas such specificity is challenged by others given the VWFA involvement during both non-word reading and word listening. Here, we further investigated this issue, measuring BOLD variations and their lateralization with fMRI during word and non-word reading, in order to evaluate the lexicality effect, and during reading and listening of words, in order to evaluate the impact of stimulus delivery modality on word processing networks. Region of interest (ROI) analysis was first performed in three target areas: 1-VWFA as defined by a meta-analysis of the word reading literature, 2-a middle temporal area (T2) found co-activated by both word reading and listening, 3-an inferior occipital area (OI) belonging to the unimodal visual cortex of the inferior occipital gyrus. VWFA activity was found not different between word and non-word reading but was more leftward lateralized during word reading due to a reduction of activity in the VWFA right counterpart. A similar larger leftward lateralization during word reading was also uncovered in the T2 ROI but was related to a larger left side activity. Such a lexicality effect was not observed in the OI ROI. By contrast, BOLD increases during listening were restricted to the left VWFA and T2 ROIs. Voxel-based analysis (SPM99) showed that semantic areas were more active during word than non-word reading and co-activated by both reading and listening, exhibiting a left lateralized activity in all tasks. These results indicate that the left VWFA would be the place where visual and verbal representations bind under the control of left semantic areas.

Adolescent↗

Processing syntactic functions of words in normal and dyslexic readers.

Readers with dyslexia were compared with normal readers for the ability to identify the grammatical function of words in the course of sentence processing by means of electrophysiological measures along with behavior measures. Participants were 18 dyslexic and 18 normally reading, native Hebrew-speaking male university students, aged 18 to 27 years. Obtained results confirmed the hypothesis (Leikin & Breznitz, 1999) that Hebrew readers used lexical-morphological properties of words to identify their grammatical roles. However, the morphologically based strategy acquired full expression only in the presence of the verb, which in the Hebrew sentence fulfills the central role. Seemingly, readers use a few different procedures to identify the grammatical roles of words. Selection of a particular strategy seems to be influenced by diverse factors, including syntactic and lexical-morphological characteristics of the stimuli and level of reading skills. In addition, the results showed significant differences in sentence processing between normal and dyslexic readers, as reflected by ERP measures. These results are in line with the hypothesis, suggesting the existence of a syntactic processing 'wsteakness" in readers with dyslexia.

Adolescent↗

On the process of recognizing inverted words: does it rely only on orientation-invariant cues?

Following a demonstration by Parks (1983) of failure to notice the reflection of a letter of an inverted word, two experiments were conducted to test a hypothesis about the process of recognizing inverted words that is termed here invariant cues only (ICO)-a letter-by-letter identification process based only on orientation-invariant letter features. In Experiment 1, subjects were presented with whole strings-words and nonwords, either upright or inverted-in which either all the letters were normal or one of the letters was reflected, and they were asked to make lexical decisions. In Experiment 2, subjects made a reflection judgment about an upright or inverted letter within a string immediately after they had been presented with the other, nonreflected string letters, again either upright or inverted. The results do not support the ICO hypothesis: Lexical decisions were greatly affected by the reflection of a letter in upright and inverted stimuli alike. Reflection judgments were considerably facilitated by word context in the upright and the inverted modes alike. The results are accommodated better by the notion that recognition of disoriented words requires some correction used to restore orientation-sensitive features.

Attention↗

Linguistic processing in visual and modality-nonspecific brain areas: PET recordings during selective attention.

Positron emission tomography (PET) was used to investigate the neural basis of selective processing of linguistic material during concurrent presentation of multiple stimulus streams ("cocktail-party effect"). Fifteen healthy right-handed adult males were to attend to one of three simultaneously presented messages: one presented visually, one to the left ear, and one to the right ear. During the control condition, subjects attended to visually presented consonant letter strings and ignored auditory messages. This paper reports the modality-nonspecific language processing and visual word-form processing, whereas the auditory attention effects have been reported elsewhere [Cogn. Brain Res. 17 (2003) 201]. The left-hemisphere areas activated by both the selective processing of text and speech were as follows: the inferior prefrontal (Brodmann's area, BA 45, 47), anterior temporal (BA 38), posterior insular (BA 13), inferior (BA 20) and middle temporal (BA 21), occipital (BA 18/30) cortices, the caudate nucleus, and the amygdala. In addition, bilateral activations were observed in the medial occipito-temporal cortex and the cerebellum. Decreases of activation during both text and speech processing were found in the parietal (BA 7, 40), frontal (BA 6, 8, 44) and occipito-temporal (BA 37) regions of the right hemisphere. Furthermore, the present data suggest that the left occipito-temporal cortex (BA 18, 20, 37, 21) can be subdivided into three functionally distinct regions in the posterior-anterior direction on the basis of their activation during attentive processing of sublexical orthography, visual word form, and supramodal higher-level aspects of language.

Adolescent↗

Consequences of violating the assumption of independence in the process dissociation procedure: a word fragment completion study.

In three experiments that used levels of processing and study time manipulations as independent variables in a word fragment completion task, the validity of the assumption of independence between recollection and automatic influences of memory was assessed. This assumption underlies the use of the process dissociation procedure (Jacoby, 1991), a tool suggested for distinguishing the different contributions of recollection and automatic influences of memory. Overall, it appeared that semantic processing, as compared with physical processing at study, positively affected recollection but negatively affected automatic influences of memory in word fragment completion. This negative effect on the automatic influences was reduced when the available study time decreased. The incompatibility of these results with the assumption of independence between recollection and automatic influences of memory and their impact on the applicability of the process dissociation procedure are discussed.

Adult↗

Overlap and dissociation of semantic processing of Chinese characters, English words, and pictures: evidence from fMRI.

The functional anatomy of Chinese character processing was investigated using fMRI. Right-handed Mandarin-English bilingual participants made either semantic or perceptual size judgements with characters and pictures. Areas jointly activated by character and picture semantic tasks compared to size judgement tasks included the left prefrontal region (BA 9, 44, 45), left posterior temporal, left fusiform, and left parietal regions. Character processing produced greater activation than picture processing in the left mid and posterior temporal as well as left prefrontal regions. The lateral occipital regions were more active during picture semantic processing than character semantic processing. A similar pattern of activation and contrasts was observed when English words and pictures were compared in another set of bilingual participants. However, there was less contrast between word and picture semantic processing than between character and picture processing in the left prefrontal region. When character and word semantic processing were compared directly in a third group, the loci of activation peaks was similar in both languages but Chinese character semantic processing was associated with a larger MR signal change. The semantic processing of Chinese characters, English words, and pictures activates a common semantic system within which there are modality-specific differences. The semantic processing of Chinese characters more closely resembles English words than pictures.

Adult↗

Dynamics of letter string perception in the human occipitotemporal cortex.

The inferior occipitotemporal brain areas, especially in the left hemisphere, have been shown to be involved in the processing of written words and letter strings. This processing probably occurs within 200 ms after presentation of the letter string. It has also been suggested that this activation may differ between fluent and dyslexic readers. Using whole-head magnetoencephalography, we studied the spatiotemporal dynamics of brain processes evoked by visually presented letter strings in 12 healthy adult subjects. Our achromatic stimuli consisted of rectangular patches in which single letters, two-letter syllables, four-letter words, or symbol strings of equal length were embedded and to which variable noise was added. This manipulation dissociated three different response patterns. The first of these patterns took place approximately 100 ms after stimulus onset, originated in areas surrounding the V1 cortex and was distributed along the ventral visual stream, extending laterally as far as V4v. This response was systematically modulated by noise but was insensitive to the stimulus content, suggesting involvement in early visual analysis. The second pattern took place approximately 150 ms after stimulus onset and was concentrated in the inferior occipitotemporal region with left-hemisphere dominance. This activation showed a preference for letter strings, and its strength and timing correlated with the speed at which the subjects were able to read words aloud. The third pattern also occurred in the time window approximately 150 ms after stimulus onset, but originated mainly in the right occipital area. Like the second pattern, it was modulated by string length, but showed no preference for letters compared with symbols. The present data strongly support the special role of the left inferior occipitotemporal cortex in visual word processing within 200 ms after stimulus onset.

Adult↗

Unconscious processing of dichoptically masked words.

In three experiments, the subjects' task was to decide whether each of a series of words connoted something good (e.g., fame, comedy, rescue) or bad (stress, detest, malaria). One-half second before the presentation of each such target word, an evaluatively polarized priming word was presented briefly to the nondominant eye and was masked dichoptically by either the rapidly following (Experiment 1) or simultaneous (Experiments 2 and 3) presentation of a random letter-fragment pattern to the dominant eye. (The effectiveness of the masking procedure was demonstrated by the subjects' inability to discriminate the left vs. right position of a test series of words.) In all experiments, significant masked priming effects were obtained; evaluative decisions to congruent masked prime-target combinations (such as a positive masked prime followed by a positive target) were significantly faster than those to incongruent (e.g., negative prime/positive target) or noncongruent (e.g., neutral prime/positive target) combinations. Also, in two of the three experiments, when subjects were at chance accuracy in discriminating word position, their position judgments were nevertheless significantly influenced by the irrelevant semantic content (LEFT vs. RIGHT) of the masked position-varying words. The series of experiments demonstrated that two very different tasks--speeded judgment of evaluative meaning and nonspeeded judgment of word position--yielded statistically significant and replicable influences of the semantic content of apparently undetectable words. Coupled with previous research by others using the lexical decision task, these findings converge in establishing the reliability of the empirical phenomenon of semantic processing of words that are rendered undetectable by dichoptic pattern masking.

Adult↗

Assessing effects of stimulus orientation on perception of lateralized words and nonwords.

Numerous studies of the processes of visual word recognition in the left and right cerebral hemispheres have attempted to control for confounding differences in the retinal placement (and hence visual acuity) of the beginnings of words by re-orientating normally-horizontal words vertically. However, despite the popularity of this approach, little is known about the precise effects that vertically orientating normally-horizontal words exert on hemispheric processes of word recognition. In this study, we investigated perception of horizontal and vertical English words and nonwords in the left visual field (LVF) and right visual field (RVF). An eye-tracking device ensured central fixation and a 2AFC paradigm (Reicher-Wheeler task) suppressed influences of non-perceptual bias. Horizontal stimuli produced a strong right visual field advantage for words but not for nonwords, whereas, vertical stimuli produced no hemifield differences at all. Moreover, vertical stimuli produced an advantage for words over nonwords in both visual fields whereas horizontal stimuli produced this effect only in the right visual field. Implications of these findings for the sensitivity of processes of word perception to stimulus orientation in the two cerebral hemispheres are discussed.

Adolescent↗

Eye-fixation behavior, lexical storage, and visual word recognition in a split processing model.

Some of the implications of a model of visual word recognition in which processing is conditioned by the anatomical splitting of the visual field between the two hemispheres of the brain are explored. The authors investigate the optimal processing of visually presented words within such an architecture, and, for a realistically sized lexicon of English, characterize a computationally optimal fixation point in reading. They demonstrate that this approach motivates a range of behavior observed in reading isolated words and text, including the optimal viewing position and its relationship with the preferred viewing location, the failure to fixate smaller words, asymmetries in hemisphere-specific processing, and the priority given to the exterior letters of words. The authors also show that split architectures facilitate the uptake of all the letter-position information necessary for efficient word recognition and that this information may be less specific than is normally assumed. A split model of word recognition captures a range of behavior in reading that is greater than that covered by existing models of visual word recognition.

Brain↗

Imaginal, semantic, and surface-level processing of concrete and abstract words: an electrophysiological investigation.

Words representing concrete concepts are processed more quickly and efficiently than words representing abstract concepts. Concreteness effects have also been observed in studies using event-related brain potentials (ERPs). The aim of this study was to examine concrete and abstract words using both reaction time (RT) and ERP measurements to determine (1) at what point in the stream of cognitive processing concreteness effects emerge and (2) how different types of cognitive operations influence these concreteness effects. Three groups of subjects performed a sentence verification task in which the final word of each sentence was concrete or abstract. For each group the truthfulness judgment required either (1) image generation, (2) semantic decision, or (3) evaluation of surface characteristics. Concrete and abstract words produced similar RTs and ERPs in the surface task, suggesting that postlexical semantic processing is necessary to elicit concreteness effects. In both the semantic and imagery tasks, RTs were shorter for concrete than for abstract words. This difference was greatest in the imagery task. Also, in both of these tasks concrete words elicited more negative ERPs than abstract words between 300 and 550 msec (N400). This effect was widespread across the scalp and may reflect activation in a linguistic semantic system common to both concrete and abstract words. ERPs were also more negative for concrete than abstract words between 550 and 800 msec. This effect was more frontally distributed and was most evident in the imagery task. We propose that this later anterior effect represents a distinct ERP component (N700) that is sensitive to the use of mental imagery. The N700 may reflect the a access of specific characteristics of the imaged item or activation in a working memory system specific to mental imagery. These results also support the extended dual-coding hypothesis that superior associative connections and the use of mental imagery both contribute to processing advantages for concrete words over abstract words.

Adult↗

Semantic processing of unattended parafoveal words.

The influence that a context word presented either foveally or parafoveally, may exert on the processing of a subsequent target word was studied in a semantic decision task. Fourteen subjects participated in the experiment. They were presented with word-nonword pairs (prime). One member of the pair (which the subjects had to attend to) appeared centrally, the other parafoveally. The prime was followed by a target at two inter-stimulus intervals (ISI; 200 and 2000 msec). The word stimulus of the pair could be semantically related or unrelated to the target. The subjects' task was to classify the target as animal or not animal by pressing one of two buttons as quickly as possible. When the target word was semantically associated with the foveal (attended) word the reaction times were faster for both ISIs; when it was associated with the parafoveal (unattended) word in the prime pair, there were facilitatory effects only in the short ISI condition. A second experiment was run in order to evaluate the possibility that the obtained results were due to identification of the parafoveal stimulus. The same prime-target pairs of experiment 1 (without the target stimuli) were used. The prime-target pairs were presented to fourteen subjects who were requested to name the foveal (attended) stimulus and subsequently, if possible, the parafoveal (unattended) one. Even in this condition, percentage of identification of the unattended word was only 15%, suggesting that previous findings were not due to identification of unattended stimuli. Results are discussed in relation to Posner and Snyder's (1975) dual coding theory.

Adult↗

Effects of priming in word retrieval.

Three studies were carried out to investigate orthographic and semantic priming effects in word retrieval. In this paradigm a prime is presented prior to the definition of a target word. The task is to produce the target word. We view the process of word retrieval as requiring access from a conceptually organized semantic network to an orthographically and phonemically organized lexical network. Primes that were orthographically (and phonemically) related to the target words were found to facilitate word retrieval. Both semantically related and unrelated primes inhibited word retrieval. Inhibition from both of these sources is attributed in part to the orthographic unrelatedness of these primes. This explanation is shown to be consistent with data from several other word retrieval studies (Brown, 1979; Roediger, Neely, & Blaxton, 1983). The word retrieval task is contrasted with the lexical decision task. It is suggested that the differential effects of orthographic and semantic priming in word retrieval and lexical decision are due to differences in retrieval processing between the two tasks.

Cues↗