Connectivity among semantic associates: an fMRI study of semantic priming

Semantic priming refers to a reduction in the reaction time to identify or make a judgment about a stimulus that has been immediately preceded by a semantically related word or picture and is thought to result from a partial overlap in the semantic associates of the two words. A semantic priming lexical decision task using spoken words was presented in event-related fMRI and behavioral paradigms. Word pairs varied in terms of semantic relatedness and the connectivity between associates. Thirteen right-handed subjects underwent fMRI imaging and 10 additional subjects were tested in a behavioral version of the semantic priming task. It was hypothesized priming would be greatest, reaction time fastest, and cortical activation reduced the most for related word pairs of high connectivity, followed by related word pairs of low connectivity, and then by unrelated word pairs. Behavioral and fMRI results confirmed these predictions. fMRI activity located primarily in bilateral posterior superior and middle temporal regions showed modulation by connectivity and relatedness. The results suggest that these regions are involved in semantic processing.     

Attention and semantic processing during speech: an fMRI study

This fMRI study was conducted to investigate whether language semantics is processed even when attention is not explicitly directed to word meanings. In the “unattended” condition, the subjects performed a visual detection task while hearing semantically related and unrelated word pairs. In the “phoneme” condition, the subjects made phoneme judgements between prime and target words, and in the “word” condition, they indicated whether the words in each word pair were semantically related or unrelated. In the word condition, stronger activity was obtained for unrelated than related words in the superior temporal gyrus/sulcus (STG/STS), lingual/fusiform gyri and cuneus, whereas in the phoneme condition no such effect was observed. However, during the unattended condition, stronger activity was found in the right STG. Our results suggest that both semantic judgement of word pairs and their passive hearing activate the same neural networks but this activation is more restricted in the passive hearing.     

Sex differences in semantic language processing: a functional MRI study

Predictions based on two models of sex differences in cerebral organization of language were compared by examining fMRI patterns of 10 females and 9 males during a semantic processing task. Both groups displayed activation of left inferior frontal gyrus (IFG), left superior temporal gyrus (STG), and cingulate. Females, but not males, showed bilateral IFG and STG activation. Further analyses revealed females had less diffuse left activation and greater right posterior temporal and insula region activation than males. Results support both an interhemispheric and an intrahemispheric model of sex differences in language, suggesting that the models may not be mutually exclusive.     

Lexical retrieval constrained by sound structure: the role of the left inferior frontal gyrus

Positron emission tomography was used to investigate two competing hypotheses about the role of the left inferior frontal gyrus (IFG) in word generation. One proposes a domain-specific organization, with neural activation dependent on the type of information being processed, i.e., surface sound structure or semantic. The other proposes a process-specific organization, with activation dependent on processing demands, such as the amount of selection needed to decide between competing lexical alternatives. In a novel word retrieval task, word reconstruction (WR), subjects generated real words from heard non-words by the substitution of either a vowel or consonant. Both types of lexical retrieval, informed by sound structure alone, produced activation within anterior and posterior left IFG regions. Within these regions there was greater activity for consonant WR, which is more difficult and imposes greater processing demands. These results support a process-specific organization of the anterior left IFG.     

Semantic priming in visual word recognition: Activation blocking and domains of processing

The fact that letter search on a prime eliminates the typically robust semantic priming effect in lexical decision is often attributed to the “shallowness” of the prime-processing task. In three experiments we investigated this claim by using two different “shallow” prime-processing tasks: letter search and color identification. Consistent with previous reports, lexical decisions to semantically related targets were not facilitated when subjects searched the prime for a probe letter. In contrast, semantic priming was observed following a color discrimination task on the prime. We suggest that a levels-of-processing interpretation is not an adequate framework for understanding these data. Instead, a domain-specific processing account is offered in which explicit processing at the letter level (as in letter search) makes demands on resources (e.g., activation) that drives processing at the semantic level. This competition is resolved by establishing a temporary activation block at the lexical-semantic interface, which results in the elimination or attenuation of semantic priming. In contrast, global judgment of color is viewed as a domain that does not make demands on the resources that drive the visual word recognition machinery. There is therefore no need for an activation block, and semantic priming is not prevented.     

Pre- and postlexical loci of contextual effects on word recognition

The context in which a word occurs could influence either the actual decoding of the word or a postrecognition judgment of the relatedness of word and context. In this research, we investigated the loci of contextual effects that occur in lexical priming, when prime and target words are related along different dimensions. Both lexical decision and naming tasks were used because previous research had suggested that they are differentially sensitive to postlexical processing. Semantic and associative priming occurred with both tasks. Other facilitative contextual effects, due to syntactic relations between words, backward associations, or changes in the proportion of related items, occurred only with the lexical decision task. The results indicate that only associative and semantic priming facilitate the decoding of a target; the other effects are postlexical. The results are related to the different demands of the naming and lexical decision tasks, and to current models of word recognition.     

语音在维——汉双语者汉字识别中的作用

采用语音启动技术,以第二语言为汉语的46名维吾尔族大学生为研究对象,考查了语音在维-汉双语者汉字识别中的作用.结果发现,维吾尔族被试在命名任务和词汇判断任务中都获得了语音启动效应,语义启动效应只出现在词汇判断任务中.结论:语音在维吾尔族大学生汉字识别中是自动激活的,而且语音的自动激活参与了语义通达.     

An event-related brain potential analysis of visual word priming effects

Two experiments are reported that provide evidence on task-induced effects during visual lexical processing in a prime-target semantic priming paradigm. The research focuses on target expectancy effects by manipulating the proportion of semantically related and unrelated word pairs. In Experiment 1, a lexical decision task was used and reaction times (RTs) and event-related brain potentials (ERPs) were obtained. In Experiment 2, subjects silently read the stimuli, without any additional task demands, and ERPs were recorded. The RT and ERP results of Experiment 1 demonstrate that an expectancy mechanism contributed to the priming effect when a high proportion of related word pairs was presented. The ERP results of Experiment 2 show that in the absence of extraneous task requirements, an expectancy mechanism is not active. However, a standard ERP semantic priming effect was obtained in Experiment 2. The combined results show that priming effects due to relatedness proportion are induced by task demands and are not a standard aspect of online lexical processing.     

Semantic priming is affected by real-time phonological competition: Evidence for continuous cascading systems

Lexical-semantic access is affected by the phonological structure of the lexicon. What is less clear is whether such effects are the result of continuous activation between lexical form and semantic processing or whether they arise from a more modular system in which the timing of accessing lexical form determines the timing of semantic activation. This study examined this issue using the visual world paradigm by investigating the time course of semantic priming as a function of the number of phonological competitors. Critical trials consisted of high or low density auditory targets (e.g., horse) and a visual display containing a target, a semantically related object (e.g., saddle), and two phonologically and semantically unrelated objects (e.g., chimney, bikini). Results showed greater magnitude of priming for semantically related objects of low than of high density words, and no differences for high and low density word targets in the time course of looks to the word semantically related to the target. This pattern of results is consistent with models of cascading activation, which predict that lexical activation has continuous effects on the level of semantic activation, with no delays in the onset of semantic activation for phonologically competing words.     

Auditory context effects in picture naming investigated with event-related fMRI

Naming an object entails a number of processing stages, including retrieval of a target lexical concept and encoding of its phonological word form. We investigated these stages using the picture-word interference task in an fMRI experiment. Participants named target pictures in the presence of auditorily presented semantically related, phonologically related, or unrelated distractor words or in isolation. We observed BOLD signal changes in left-hemisphere regions associated with lexical-conceptual and phonological processing, including the midto-posterior lateral temporal cortex. However, these BOLD responses manifested as signal reductions for all distractor conditions relative to naming alone. Compared with unrelated words, phonologically related distractors showed further signal reductions, whereas only the pars orbitalis of the left inferior frontal cortex showed a selective reduction in response in the semantic condition. We interpret these findings as indicating that the word forms of lexical competitors are phonologically encoded and that competition during lexical selection is reduced by phonologically related distractors. Since the extended nature of auditory presentation requires a large portion of a word to be presented before its meaning is accessed, we attribute the BOLD signal reductions observed for semantically related and unrelated words to lateral inhibition mechanisms engaged after target name selection has occurred, as has been proposed in some production models.     

On obtaining episodic priming in a lexical decision task following paired-associate learning

In four experiments, subjects made lexical (word-nonword) decisions to target letter strings after studying paired associates. In this lexical decision test, word targets previously studied as response terms in the paired associates were preceded at a 150-ms and/or 950-ms stimulus onset asynchrony (SOA) by one of various subsets of the following six types of primes: a neutral (XXX or ready) prime, a semantically unrelated word prime episodically related to the target through its having been previously studied in the same pair, a semantically related word prime previously studied in a pair with some other unrelated word, a semantically unrelated word prime previously studied in a pair with some other unrelated word, a nonstudied semantically related word prime, and a nonstudied semantically unrelated word prime. At the 950-ms SOA, facilitation of lexical decisions produced by the episodically related primes was greater in test lists in which there were no 150-ms SOA trials intermixed, no previously studied semantically related primes, and no studied nonword targets. At the 150-ms SOA, facilitation from episodic priming was greater in test lists in which there were no semantically related primes and all studied word targets and no studied nonword targets. Facilitation effects from semantically related primes were small in magnitude and occurred inconsistently. Discussion focused on the implications these results have for the episodic-semantic memory distinction and the automaticity of episodic and semantic priming effects.     

Semantic priming in the pronunciation task: The role of prospective prime-generated expectancies

In the relatedness proportion effect, semantic priming increases with an increase in the probability that a word prime will be followed by a semantically related word target. This effect has frequently been obtained in the lexical decision task but not in a pronunciation task. In the present experiment, relatedness proportion was manipulated in two pronunciation tasks, one with and one without nonword targets, using category names as primes. In both tasks, a relatedness proportion effect occurred for high-dominance category exemplars but not for low-dominance category exemplars. These results converge with recent lexical decision results in suggesting that semantic priming in pronunciation is affected by a prospective prime-generated expectancy that is modulated by the relatedness proportion.     

How semantic is automatic semantic priming?

Priming for semantically related concepts was investigated using a lexical decision task designed to reveal automatic semantic priming. Two experiments provided further evidence that priming in a single presentation lexical decision task (McNamara & Altarriba, 1988) derives from automatic processes. Mediated priming, but no inhibition or backward priming was found in this type of lexical decision task. Experiments 3 and 4 demonstrated that automatic priming was found only for associated word pairs, as determined by word association norms, and not for word pairs that are semantically related but not associated. It is argued that automatic priming in the lexical decision task occurs at a lexical level not at a semantic level.     

Relation between pronunciation and recognition of printed words in deep and shallow orthographies

The processes responsible for recognition and pronunciation of printed words were studied by means of lexical decision and naming experiments. Two languages were examined: English, which has a complex and deep correspondence between spelling and speech, and Serbo-Croatian, in which the correspondence is simple and direct. It was hypothesized that reliance on articulatory coding (instead of on mediation by the internal lexicon) would be greater for Serbo-Croatian because its shallow orthography would allow more efficient use of spelling-to-speech correspondences. Each target stimulus was preceded by a word that was either related or unrelated semantically. Semantic priming of target words facilitated performance in both lexical decision and naming for English, results suggesting an influence of the internal lexicon on both processes. In contrast, semantic priming facilitated only lexical decision for Serbo-Croatian, which suggests that naming, at least in that language, is not strongly influenced by the internal lexicon. Further, in Serbo-Croatian, lexical decision and naming latencies were correlated when both tasks were not semantically primed and were uncorrelated when either or both tasks received semantic priming. This suggested that articulatory coding is used in lexical decision, at least under conditions in which contextual semantic facilitation is absent. In contrast, in English, lexical decision and naming were correlated uniformly whether semantic facilitation was present or not, which, when considered with the effect of semantic facilitation on naming, suggested a stronger influence of the internal lexicon on both recognition and pronunciation.     

中文词汇加工过程中的无关言语效应

通过两个词汇识别任务,考察词汇加工过程中的无关言语效应。实验1采用真假词判断任务,考察有意义言语、无意义言语、白噪音和安静的背景声音对不同具体性的词汇识别的影响。结果发现,仅有意义言语干扰了词汇识别,且主要体现在对低具体性词汇判断的反应时显著增加。实验2采用了语义范畴判断任务,同样发现有意义言语条件下被试的反应时显著大于其他声音条件。结果表明,中文词汇加工过程中存在无关言语效应,且当任务强调语义加工时,干扰主要源于无关言语的语义成分,支持了语义干扰假说。     

Measuring lexical access during sentence processing

The results from “on-line” investigations of sentence comprehension are often difficult to interpret since it is not always apparent what component processes are reflected in the response measure. The results of two experiments reported here indicate that response latencies from phoneme-triggered lexical decision (PTLD) reflect the time needed for lexical access during sentence processing. Listeners were presented with sentences and were asked to make a word/nonword judgment for items beginning with a particular word-initial target phoneme. Speed of lexical access was manipulated by varying the semantic predictability of the target-bearing word. WORD judgments were faster for words that were preceded by semantically related verbs than were WORD judgments for words that were preceded by neutral verbs. The present results are consistent with other studies showing semantic facilitation of lexical access during the processing of fluent speech. It is argued that the phoneme-triggered lexical-decision task is a more suitable measure of lexical access during sentence processing than phoneme monitoring (Foss, 1969) or word monitoring (Marslen-Wilson & Tyler, 19751. In addition, it is pointed out that the phoneme-triggered lexical-decision task lends itself to modifications which should enable investigators to study various aspects of on-line sentence processing.     

Behavioral and fMRI evidence that cognitive ability modulates the effect of semantic context on speech intelligibility

Text cues facilitate the perception of spoken sentences to which they are semantically related (Zekveld, Rudner, et al., 2011). In this study, semantically related and unrelated cues preceding sentences evoked more activation in middle temporal gyrus (MTG) and inferior frontal gyrus (IFG) than nonword cues, regardless of acoustic quality (speech in noise or speech in quiet). Larger verbal working memory (WM) capacity (reading span) was associated with greater intelligibility benefit obtained from related cues, with less speech-related activation in the left superior temporal gyrus and left anterior IFG, and with more activation in right medial frontal cortex for related versus unrelated cues. Better ability to comprehend masked text was associated with greater ability to disregard unrelated cues, and with more activation in left angular gyrus (AG). We conclude that individual differences in cognitive abilities are related to activation in a speech-sensitive network including left MTG, IFG and AG during cued speech perception.     

Phonological, Semantic, and Mediated Priming in Aphasia

An auditory lexical decision task was conducted to examine rhyme, semantic, and mediated priming in nonfluent and fluent aphasic patients and normal controls. Overall, monosyllabic word targets were responded to faster when preceded by rhyming word and nonword primes than unrelated primes. Similarly, semantically related primes facilitated lexical decisions to word targets. No evidence of mediated priming emerged. Results for individual subjects suggest differences in patterns across the subject groups. Implications of the findings for the integrity of lexical access in aphasic patients are considered.     

图词间隔时间影响口语词汇产生中语义效应的机制：图词干扰范式研究

口语词汇产生过程中存在语义抑制和语义促进效应, 可能发生在概念准备和词汇选择或者后词汇水平阶段。本研究采用图画-词汇干扰实验任务, 变化图画与词汇出现点之间的时间间隔(stimulus onset asynchrony, SOA), 运用脑电技术考察口语词汇产生中语义效应发生的时间进程。结果显示, 当SOA为0 ms时表现出语义抑制效应, 语义效应发生在词汇选择阶段(344~418 ms); 当SOA为-400 ms时, 语义效应发生在概念准备阶段(0~76 ms)和词汇选择阶段(274~390 ms); 460~594 ms时间窗口内的语义效应可能表明讲话者对语义信息的自我监测。词汇产生中存在语义促进效应和抑制效应的权衡, 影响了行为结果中语义效应的方向, 上述发现支持了口语词汇产生的词汇竞争假说。     

The role of syntactic context in word recognition

This study examines the role of syntactic information in word recognition. Subjects made a word-nonword decision regarding a target string that was preceded by a syntactically appropriate word, a semantically related word, or an unrelated word. In Experiment 1, with syntactic and semantic trials assigned to separate blocks, syntactically and semantically appropriate context significantly reduced lexical decision for subsequent target words, compared with unrelated contexts. In Experiment 2, the syntactically and semantically primed trials were either blocked separately or mixed within the same block. Significant syntactic and semantic effects were both observed in the blocked condition, but only the semantic effect was obtained in the mixed condition