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PubMed1998

Semantic, repetition and rime priming between spoken words: behavioral and electrophysiological evidence.

Semantic, phonological and repetition priming for auditorily presented words were examined, using both behavioral reaction times (RTs) and electrophysiological event-related potentials (ERPs) measures. On critical trials, a word prime was followed by a word target that was semantically or phonologically related (rime) or not related (control) to the prime. Pairs of word-pseudoword items served as fillers. Participants were asked to respond to word targets in the RT experiment and to pseudowords in the ERP experiment. In each experiment stimuli were presented once and then repeated in the very same way. RTs were found to be fastest for semantic, intermediate for rime and slowest for control targets; large repetition effects occurred for all targets. ERPs results showed that both semantic and phonological priming influenced the same component, namely the N400, whose amplitude was smallest to semantic, intermediate to rime and largest to control targets; repetition effects were only found for semantic trials.

Acoustic Stimulation↗

PubMed2002

Cortical brain responses to semantic incongruity and syntactic violation in Italian language: an event-related potential study.

The present experiment investigated cortical responses of native Italian subjects during reading of short sentences including semantic or morphosyntactic violations. Given the specificity of the Italian language in which the sequencing of words is relatively more free than in English or other languages, we investigated whether syntactic and semantic violations were able to elicit event-related potential (ERP) components similar to those found in other languages. Cortical potentials evoked by the anomalous target word were recorded at frontal, central and parietal electrodes. Results showed that, in Italian, semantic anomaly elicited a negative wave (N400) in the 400-500 ms time-window and syntactic error evoked a slower positive wave (P600) in the 500-700 ms time-window. Syntactic error also evoked a significant left anterior negativity in the 350-450 ms time-window, supporting the view that syntactic processes precedes semantic analysis. Thus, Italian language, notwithstanding its specificity, shows ERPs responses to semantic and syntactic violations, with effects, scalp distribution and latency similar to those found in German, Dutch and English. Results point to a cross-linguistic consistency of the semantic and syntactic ERP components associated with the detection of linguistic anomalies.

Adolescent↗

PubMed2002

Lexical decision tasks in depressive patients: semantic priming before and after clinical improvement.

This study was designed to evaluate the effect of semantic priming with a lexical decision task in 22 depressed patients (DSM-III-R, 1987) and 30 control subjects. These patients were evaluated twice: first when they arrived at the hospital, and secondly, after clinical improvement. Clinical improvement was evaluated using standard depression rating scales. A lexical decision task involving semantic relations (related vs. unrelated, e.g., apple-pear) was used to evaluate the processing of semantic information. The results showed that, for the first evaluation, the depressives presented similar semantic priming to control subjects. When we compared semantic priming in the first and the second passes, we observed that its amplitude was identical. The sole difference between the two passes concerns the global reaction time in the depressive group. This last result suggested that, with clinical improvement, the characteristic psychomotor retardation declines. One of the major results concerns the fact that severe depressive patients (first pass) exhibit normal semantic priming in a lexical decision task. These results indicate, in this clinical population, the preservation of controlled processes implicated in this lexical decision task.

Adult↗

PubMed2000

Neural correlates of semantic associative encoding in episodic memory.

Associations between individual items are the basic building blocks of learning and memory. Functional neuroimaging has now made it possible to study neural correlates of such associations. The present PET study examined three associative encoding conditions differing in the number of words (0, 1, or 2) semantically related to a third word representing the name of a semantic category. A recall task consisting in the presentation of the category names as cues for retrieving the other two members of the triads followed each encoding condition. As expected, retrieval performance increased as the number of semantic exemplars at encoding increased (10%, 43%, 70% items recalled, respectively). A first analysis (partial least squares, PLS) of the PET data identified task-related patterns of activity for associative encoding and cued-recall tasks. A second analysis identified brain regions whose activity was modulated by the number of semantic exemplars at encoding. Some of the task-related brain regions also showed modulated activity by semantic relatedness and consisted in the left inferior prefrontal cortex, right medial temporal lobe, fusiform gyrus and inferior temporal gyrus bilaterally. Some of these regions showed greater activity when words in a triad were unrelated, whereas others did so when the three words were semantically related. These regions have been consistently reported in previous functional neuroimaging studies of associative encoding and may constitute key structures in association formation.

Adult↗

PubMed2003

Functional MRI study of semantic and phonological language processing in bilingual subjects: preliminary findings.

The objective of the study was to explore differences in regional fMRI activation topography and lateralization between semantic and phonological tasks performed in English and Spanish in bilingual individuals. Eight bilingual (primary Spanish and secondary English-speaking) individuals performed fMRI noun-verb association and rhyming tasks in both Spanish and English. Functional dataset analysis within Statistical Parametric Mapping (SPM99) with overlay on T1-weighted anatomic images was performed. Significantly higher laterality indices were noted in the semantic tasks as compared with the phonological tasks in the anterior regions of interest comprising the frontal and superior temporal lobes. A task subtraction analysis demonstrated right hemispheric (inferior frontal gyrus and supramarginal gyrus) foci of significantly increased activation in the combined language phonological tasks compared to the combined language semantic tasks; similarly prominent right hemispheric activation was seen in the English phonological-English semantic subtraction, but the analogous Spanish task subtraction revealed no task-related differences. This divergence in activation topography between semantic and phonological tasks performed in the nonnative language, but not in the primary language, suggests that neural networks utilized for phonological and semantic language processing in the nonnative language may not be as similar as those in the primary language.

Adult↗

PubMed2002

Manual semantic tagging to improve access to information in narrative electronic medical records.

OBJECTIVE: To assess effectiveness of information retrieval from narrative patient records utilizing manually supplied semantic tags. DESIGN: Retrospective evaluation of narrative electronic record notes with respect to consistency of manually supplied semantic tags. Assessment of retrieval effectiveness using string matching methods and methods based on structural characteristics of data. SETTING: Department of Neurology in a Norwegian university hospital using a document based electronic patient record system offering template assisted manual semantic indexing of textual record notes. MEASUREMENTS: Proportion of consistently tagged information. Retrieval effectiveness expressed as recall (sensitivity) and precision (positive predictive value). RESULTS: Seventy-five percent of the content was consistently tagged. Retrieval models based on simple string matching performed better than models based on semantic tags alone with respect to best mean recall and mean precision at high recall-levels. Models combining both simple string matching and semantic tagging performed better than separate models with respect to best mean recall (0.95) and mean precision at high levels of recall. CONCLUSION: Although template assisted semantic indexing of narrative electronic patient record notes showed suboptimal consistency, it significantly improved retrieval effectiveness with respect to best mean recall obtained by individual strategies and with respect to precision at any recall level.

Abstracting and Indexing↗

PubMed2005

Formal thought disorder in schizophrenia: an executive or a semantic deficit?

BACKGROUND: It has been hypothesized that the schizophrenic symptom of formal thought disorder is linked to both executive and semantic dysfunction. METHOD: Intellectually preserved schizophrenic patients with (n = 15) and without (n = 16) formal thought disorder, plus matched normal controls (n = 17) were administered four executive and four semantic tests. Tests of verbal fluency and comprehension of grammar were also given. RESULTS: The patients with formal thought disorder were significantly impaired on all four executive tests compared to the patients without the symptom. They were only impaired compared to non-thought-disordered patients on 1 of 4 semantic tests, which probed semantic associations between concepts. Naming performance did not distinguish the two groups, nor did a previously used measure of semantic fluency controlling for phonological fluency. CONCLUSIONS: The results provide support for a dysexecutive hypothesis of formal thought disorder in schizophrenia, and, in line with other studies, suggest that there may be a restricted 'higher-order' semantic deficit which spares naming.

Adult↗

PubMed1999

Effects of semantic predictability on children's preservation of a phonemic voice contrast.

We investigated the effects of semantic predictability on children's preservation of the /t/-/d/ phonemic voice contrast in American English. In Experiment 1, a total of 36 seven-, nine-, and twelve-year-olds produced minimal pairs differing in intervocalic /t/ and /d/ in semantically biasing and semantically neutral passages. The seven-year-olds preserved the phonemic contrast in both passage types. However, for the nine- and twelve-year-olds, total word duration and preceding vowel duration preserved the /t/-/d/ contrast, but this interacted with semantic predictability. The contrast was preserved in the biasing and not in the neutral passages. The production results from the older children replicated previous findings from adults, demonstrating that semantic predictability influences speech production at both a lexical and a segmental level. In Experiment 2, listeners identified the tokens produced in Experiment 1. The identification results suggested that differences produced by speakers may not necessarily have a functional role for listeners. An interactive activation framework is proposed to account for the semantic effects on older children's and adults' production. For the youngest children, however, we suggest that pragmatic compensation and task demands interact with the effects of interactive activation.

Child↗

PubMed2003

Is there disproportionate impairment in semantic or phonemic fluency in schizophrenia?

Phonemic and semantic fluency involve the capacity to generate words beginning with particular letters or belonging to particular categories, respectively. The former has been associated with frontal lobe function and the latter with temporoparietal function, but neuroimaging studies indicate overlap of underlying neural networks. Schizophrenia patients may experience disproportionate semantic fluency impairment owing to abnormal semantic organization; however, executive dysfunction in schizophrenia suggests possible disproportionate phonemic fluency impairment. Moreover, little is known about the diagnostic specificity of either verbal fluency deficit to schizophrenia or their stability over time. We examined 83 schizophrenia patients, 15 bipolar disorder patients, and 83 normal controls. Both fluency types were impaired in schizophrenia patients. Schizophrenia patients as a whole manifested disproportionate semantic fluency impairment relative to bipolar disorder patients, but only a subset of schizophrenia patients manifested disproportionate semantic fluency impairment relative to controls. Few characteristics, except to some extent paranoid-nonparanoid subtype, meaningfully differentiated schizophrenia patients with and without this disproportionate impairment. Verbal fluency measures were moderately stable over a 4-year period in schizophrenia patients and controls (.48 < rs < .79). These results mirror a literature that overall suggests a small degree of disproportionate semantic fluency impairment in schizophrenia, but also some heterogeneity in fluency deficits.

Adult↗

PubMed2004

Dopamine and semantic activation: an investigation of masked direct and indirect priming.

To investigate the effects of dopamine on the dynamics of semantic activation, 39 healthy volunteers were randomly assigned to ingest either a placebo (n = 24) or a levodopa (n = 16) capsule. Participants then performed a lexical decision task that implemented a masked priming paradigm. Direct and indirect semantic priming was measured across stimulus onset asynchronies (SOAs) of 250, 500 and 1200 ms. The results revealed significant direct and indirect semantic priming effects for the placebo group at SOAs of 250 ms and 500 ms, but no significant direct or indirect priming effects at the 1200 ms SOA. In contrast, the levodopa group showed significant direct and indirect semantic priming effects at the 250 ms SOA, while no significant direct or indirect priming effects were evident at the SOAs of 500 ms or 1200 ms. These results suggest that dopamine has a role in modulating both automatic and attentional aspects of semantic activation according to a specific time course. The implications of these results for current theories of dopaminergic modulation of semantic activation are discussed.

Adult↗

PubMed1999

Object identification deficits in dementia of the Alzheimer type: combined effects of semantic and visual proximity.

Identification deficits in dementia of the Alzheimer Type (DAT) often target specific classes of objects, sparing others. Using line drawings to uncover the etiology of such category-specific deficits may be untenable because the underlying shape primitives used to differentiate one line drawing from another are unspecified, and object form is yoked to object meaning. We used computer generated stimuli with empirically specifiable properties in a paradigm that decoupled form and meaning. In Experiment 1 visually similar or distinct blobs were paired with semantically close or disparate labels, and participants attempted to learn these pairings. By having the same blobs stand for semantically close and disparate objects and looking at shape-label confusion rates for each type of set, form and meaning were independently assessed. Overall, visual similarity of shapes and semantic similarity of labels each exacerbated object confusions. For controls, the effects were small but significant. For DAT patients more substantial visual and semantic proximity effects were obtained. Experiment 2 demonstrated that even small changes in semantic proximity could effect significant changes in DAT task performance. Labeling 3 blobs with "lion," "tiger," and "leopard" significantly elevated DAT confusion rates compared to exactly the same blobs labeled with "lion," "tiger," and "zebra." In conclusion both visual similarity and semantic proximity contributed to the identification errors of DAT patients.

Aged↗

PubMed1999

Neuroanatomic substrates of semantic memory impairment in Alzheimer's disease: patterns of functional MRI activation.

Impairment in semantic processing occurs early in Alzheimer's disease (AD) and differential impact on subtypes of semantic relations have been reported, yet there is little data on the neuroanatomic basis of these deficits. Patients with mild AD and healthy controls underwent 3 functional MRI auditory stimulation tasks requiring semantic or phonological decisions (match-mismatch) about word pairs (category-exemplar, category-function, pseudoword). Patients showed a significant performance deficit only on the exemplar task. On voxel-based fMRI activation analyses, controls showed a clear activation focus in the left superior temporal gyrus for the phonological task; patients showed additional foci in the left dorsolateral prefrontal and bilateral cingulate areas. On the semantic tasks, predominant activation foci were seen in the inferior and middle frontal gyrus (left greater than right) in both groups but patients showed additional activation suggesting compensatory recruitment of locally expanded foci and remote regions, for example, right frontal activation during the exemplar task. Covariance analyses indicated that exemplar task performance was strongly related to signal increase in bilateral medial prefrontal cortex. The authors conclude that fMRI can reveal similarities and differences in functional neuroanatomical processing of semantic and phonological information in mild AD compared to healthy elderly, and can help to bridge cognitive and neural investigations of the integrity of semantic networks in AD.

Aged↗

PubMed2001

An event-related fMRI study of syntactic and semantic violations.

We used event-related functional magnetic resonance imaging to identify brain regions involved in syntactic and semantic processing. Healthy adult males read well-formed sentences randomly intermixed with sentences which either contained violations of syntactic structure or were semantically implausible. Reading anomalous sentences, as compared to well-formed sentences, yielded distinct patterns of activation for the two violation types. Syntactic violations elicited significantly greater activation than semantic violations primarily in superior frontal cortex. Semantically incongruent sentences elicited greater activation than syntactic violations in the left hippocampal and parahippocampal gyri, the angular gyri bilaterally, the right middle temporal gyrus, and the left inferior frontal sulcus. These results demonstrate that syntactic and semantic processing result in nonidentical patterns of activation, including greater frontal engagement during syntactic processing and larger increases in temporal and temporo-parietal regions during semantic analyses.

Brain↗

PubMed2002

Early components of event-related potentials related to semantic and syntactic processes in the Japanese language.

Brain activities were compared between semantic and syntactic processing in the Japanese language using event-related potentials with a 58-ch EEG system. We previously found that semantic violations elicited N400 and syntactic violations elicited P600 but not early left anterior negativity (ELAN) or left anterior negativity (LAN) using a relatively long stimulus presentation time (1 s). In the present study, we adopted a shorter stimulus presentation time (0.5 s), which might impose a heavier burden on the working memory system, to test the possible relevance of load on the working memory system to ELAN/LAN. A global field power analysis showed an increased potential field strength at the latency of 320 ms in either type, as well as those at the later latencies reflecting N400 (556 ms) and P600 (712 ms). Statistical analyses revealed a significant negative deflection in the right frontal region for the semantic type, whereas no significant deflection in either specified region was obtained for the syntactic type at the latency of 320 ms. The lack of ELAN/LAN suggested that it was not due to the deactivation of the working memory system. Moreover, scalp current density topographies implied that the processing of the verbal stimuli was mediated by distinct areas within the left temporal region, according to its semantic congruency with the preceding context at a latency as early as 320 ms. These findings are in line with the dual-route hypothesis of reading, which suggests that the reading of verbal stimuli semantically incongruent with the preceding context is dominated by phonological processes rather than lexico-semantic.

Adult↗

PubMed1998

Recognition by action: dissociating visual and semantic routes to action in normal observers.

In this article the operation of a direct visual route to action in response to objects, in addition to a semantically mediated route, is demonstrated. Four experiments were conducted in which participants made gesturing or naming responses to pictures under deadline conditions. There was a cross-over interaction in the number of visual errors relative to the number of semantic plus semantic-visual errors in the two tasks: In gesturing, compared with naming, participants made higher proportions of visual errors and lower proportions of semantic plus semantic-visual errors (Experiments 1, 3, and 4). These results suggest that naming and gesturing are dependent on separate information-processing routes from stimulus to response, with gesturing dependent on a visual route in addition to a semantic route. Partial activation of competing responses from the visual information present in objects (mediated by the visual route to action) leads to high proportions of visual errors under deadline conditions. Also, visual errors do not occur when gestures are made in response to words under a deadline (Experiment 2), which indicates that the visual route is specific to seen objects.

Adult↗

PubMed1983

Parafoveal visual information and semantic contextual constraints.

Two experiments are reported that examine the influence of semantic contextual constraints on an individual's ability to use parafoveal visual information. Subjects were presented either a word (reptile) or a row of Xs in foveal vision along with a parafoveal nonword (snckks) centered 2.3 degrees or 5 degrees to the left or right of fixation. The subjects were asked to pronounce the parafoveal stimulus aloud. During their eye movement to that stimulus, the nonword was replaced by a word that was either (a) semantically related to the foveal item and visually related to the parafoveal preview nonword (snakes), (b) semantically unrelated to the foveal item and visually related to the preview (sneaks), (c) semantically related to the foveal item and visually unrelated to the preview (lizard), or (d) semantically unrelated to the foveal item and visually unrelated to the preview (limits). In Experiment 1, subjects were only given 250 msec to use the semantic context, whereas in Experiment 2, subjects were given 1,250 msec. The results of both experiments yielded highly significant effects of contextual constraints and parafoveal visual information. However, the first experiment yielded additive effects of the two variables, whereas the second experiment yielded interactive effects. The results are discussed in light of recent arguments regarding the importance of contextual constraints for the use of parafoveal visual information.

Cues↗

PubMed1988

Semantic facilitation with pictures and words.

The present experiments explored the role of processing level and strategic factors in cross-form (word-picture and picture-word) and within-form (picture-picture and word-word) semantic facilitation. Previous studies have produced mixed results. The findings presented in this article indicate that semantic facilitation depends on the task and on the subjects' strategies. When the task required semantic processing of both picture and word targets (e.g., category verification), equivalent facilitation was obtained across all modality combinations. When the task required name processing (e.g., name verification, naming), facilitation was obtained for the picture targets. In contrast, with word targets, facilitation was obtained only when the situation emphasized semantic processing. The results are consistent with models that propose a common semantic representation for both picture and words but that also include assumptions regarding differential order of access to semantic and phonemic features for these stimulus modalities.

Adult↗

PubMed1989

Semantic associations and elaborative inference.

In this article, a theoretical framework is proposed for the inference processes that occur during reading. According to the framework, inferences can vary in the degree to which they are encoded. This notion is supported by three experiments in this article that show that degree of encoding can depend on the amount of semantic-associative information available to support the inference processes. In the experiments, test words that express possible inferences from texts are presented for recognition. When testing is delayed, with other texts and test items intervening between a text and its test word, performance depends on the amount of semantic-associative information in the text. If the inferences represented by the test words are not supported by semantic associates in the text, they appear to be only minimally encoded (replicating McKoon & Ratcliff, 1986), but if they are supported by semantic associates, they are strongly encoded. With immediate testing, only 250 ms after the text, performance is shown to depend on semantic-associative information, not on textual information. This suggests that it is the fast availability of semantic information that allows it to support inference processes.

Adult↗