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PubMed2003

Semantic hyperpriming in thought-disordered patients with schizophrenia: state or trait?--a longitudinal investigation.

Enhanced semantic priming (SP) has been reported in individuals with schizophrenia who exhibit positive formal thought disorder (TD) and it has been linked to heightened automatic spreading activation in semantic networks of these patients. However, the state or trait nature of semantic hyperpriming in schizophrenia and its relation to clinical features (e.g., length of illness, symptom shifts) is not clear. To explore these issues, we administered a lexical decision task with semantically related, indirectly related or unrelated prime-target pairs to acutely ill inpatients with schizophrenia shortly after admission and again after 12-16 weeks, while most patients were already in (partial) remission (n=33). In addition, we examined 20 healthy control subjects twice (2 weeks apart). Relative to control subjects, TD patients with schizophrenia exhibited hyperpriming only in the acute psychotic state, but not during the follow-up examination, when TD and other positive symptoms had resolved. There were no associations between priming effects and length of illness or number of previous psychotic episodes. In conclusion, semantic hyperpriming in TD patients with schizophrenia appears to be clearly state-dependent and might be viewed as an episode marker of psychosis with TD.

Adult↗

PubMed2003

Matching faces for semantic information and names: an event-related brain potentials study.

In face identification, it has been controversial whether or not access to biographical information and to a person's name are mediated by qualitatively different loci. We recorded ERPs while participants saw two successive faces and performed a matching task that either required retrieval of semantic information ("same or different profession?"), or retrieval of the person's name ("same or different number of forename syllables?"). For both tasks, slow ERP activity between the first and the second face was characterized by a prominent right posterior negativity, with the asymmetry being larger for the name than the semantic matching task. ERPs to the second face showed a difference between congruent (matching) and incongruent (mismatching) trials, with more negative ERPs for incongruent trials. In the semantic matching task, these differences were significant between 450 and 550 ms, and resembled an N400, with a maximum negativity over the vertex. In the name matching task, the topography of this congruency effect was qualitatively different from that seen in semantic matching. These findings suggest that different brain substrates mediate the access to semantic and name information.

Adolescent↗

PubMed1999

The lifetime of automatic semantic priming effects may exceed two seconds.

The N400 component of event-related potentials (ERPs) was obtained in a modified version of the Neely [J.H. Neely, Semantic priming and retrieval from lexical memory: Roles of inhibitionless spreading activation and limited-capacity attention, Journal of Experimental Psychology: General, Vol. 106 (1977), pp. 226-254.] paradigm which permits unconfounding of semantic priming effects due to automatic and attentional processes. It was found that a short stimulus onset asynchrony (SOA) of 250 ms between the prime and the target was associated with automatic but not expectancy effects on the amplitude of N400. At a long SOA of 2000 ms between prime and target, semantic priming effects on N400 were obtained associated with both automatic and expectancy processes. Moreover, there was no significance difference in the magnitude of the automatic effects at the two SOAs, suggesting that automatic processing had not decayed within the 2000 ms interval between the prime and target. The results support the two-processing interpretation of semantic priming advanced by Posner and Synder [M.I. Posner, C.R.R. Snyder, Attention and cognitive control, in: R.L. Solso (Ed.), Information Processing and Cognition: The Loyola Symposium, Erlbaum, Hillsdale, NJ (1975).] and concur with the results of Neely [J.H. Neely, Semantic priming and retrieval from lexical memory: Roles of inhibitionless spreading activation and limited-capacity attention, Journal of Experimental Psychology: General, Vol. 106 (1977), pp. 226-254], with the exception of indicating a longer persistence of automatic processes.

Adult↗

PubMed2000

Event-related potential indices of semantic priming using masked and unmasked words: evidence that the N400 does not reflect a post-lexical process.

Several authors have contended that the N400 is a reflection of a post-lexical event such as that proposed by Neely and Keefe [J.H. Neely, D.E. Keefe, Semantic context effects on visual word processing: a hybrid prospective/retrospective processing theory, in: G.H. Bower (Ed.), The Psychology of Learning and Motivation: Advances in Research and Theory, Vol. 23, Academic Press, New York, 1989, pp. 207-248.], whereby the subject compares the word on the current trial to the "context" provided by the word on the preceding trial [M. Besson, M. Kutas, The many facets of repetition: A cued-recall and event-related potential analysis of repeating words in same versus different sentence contexts, Journal of Experimental Psychology: Learning, Memory and Cognition, 19 (5) (1993), 1115-1133; C. Brown, P. Hagoort, The processing nature of the N400: Evidence from masked priming. Journal of Cognitive Neuroscience, 5(1) (1993), 34-44; P.J. Holcomb, Semantic priming and stimulus degradation: Implications for the role of the N400 in language processing, Psychophysiology 30 (1993), 47-61; M.D. Rugg, M.C. Doyle, Event-related potentials and stimulus repetition in indirect and direct tests of memory, in: H. Heinze, T. Munte, G.R. Mangun (Eds), Cognitive Electrophysiology, Birkhauser Boston, Cambridge, MA, 1994]. A study which used masked primes to directly test this possibility has been reported by Brown and Hagoort [C. Brown, P. Hagoort, The processing nature of the N400: evidence from masked priming. Journal of Cognitive Neuroscience, 5(1) (1993), 34-44]. When the primes were masked, no priming effect was observed on the N400. When behavioral data were collected in the same paradigm, from another group of subjects, the usual priming effect on RT was obtained. Considered together, the data from the two groups of subjects indicated that activation of semantic representations had occurred without conscious awareness. As no N400 priming effect was observed, it was suggested that N400 must reflect a post-lexical process. This interpretation, however, is at odds with the findings of other studies which have reported N400 priming effects under conditions where post-lexical processes would not be thought to operate[J. Anderson, P. Holcomb, Auditory and visual semantic priming using different stimulus onset asynchronies: an event-related brain potential study. Psychophysiology 32 (1995), 177-190; J. Boddy, Event-related potentials in chronometric analysis of primed word recognition with different stimulus onset asynchronies, Psychophysiology 23 (1986), 232-245; D. Deacon, T. Uhm, W. Ritter, S. Hewitt, The lifetime of automatic priming effects may exceed two seconds, Cognitive Brain Research 7 (1999), 465-472; P.J. Holcomb, Automatic and attentional process: an event-related brain potential analysis of semantic priming. Brain and Language 35 (1998) 66-85]. The present study replicated Brown and Hagoort using a repeated measures design, a shorter SOA (stimulus onset asynchrony), and a slightly different threshold setting procedure. Significant priming effects were obtained on the mean amplitude of the N400 regardless of whether the words were masked or unmasked. The findings imply that the processing subserving the N400 is not postlexical, since the N400 was manipulated without the subjects being aware of the identity of the words.

Adolescent↗

PubMed2002

Semantic priming: on the role of awareness in visual word recognition in the absence of an expectancy.

By hypothesis, awareness is involved in the modulation of feedback from semantics to the lexical level in the visual word recognition system. When subjects are aware of the fact that there are many related prime-target pairs in a semantic priming experiment, this knowledge is used to configure the system to feed activation back from semantics to the lexical level so as to facilitate processing. When subjects are unaware of this fact, the default set is maintained in which activation is not fed back from semantics to the lexical level so as to conserve limited resources. Qualitative differences in the pattern of data from two lexical decision experiments that employ masked priming are consistent with this hypothesis. Semantic context and stimulus quality interact when the prime is processed with awareness whereas these same two factors produce additive effects on RT when the prime is unlikely to have been processed with awareness. These experiments thus illustrate one way in which awareness (or lack thereof) affects the dynamics of visual word recognition.

Adult↗

PubMed1999

Cortical activation related to auditory semantic matching of concrete versus abstract words.

OBJECTIVE: The aim of this study was to examine cortical correlates of semantic memory processes in the auditory stimulus modality. METHODS: Event-related desynchronization (ERD) and synchronization (ERS) of the lower (8-10 Hz) and upper (10-12 Hz) alpha frequency bands of background EEG were studied in 10 subjects performing an auditory semantic matching task. The stimuli were abstract and concrete nouns which were presented sequentially in pairs. The task was to decide whether the two nouns belonged to the same semantic category or not. RESULTS: The presentation of the first stimulus (encoding) elicited ERS whereas the presentation of the second stimulus (semantic matching) elicited ERD. Abstract nouns presented as the second stimulus elicited ERD which was most prominent in the lower alpha frequency band, whereas the presentation of a concrete noun as the first stimulus elicited ERS, most prominently in the upper alpha frequency band. CONCLUSIONS: The auditorily elicited ERD/ERS reflects cortical activity associated with cognitive functions. The present findings demonstrate that the auditorily elicited ERD/ERS can reveal subtle differences in auditory information processing. Semantic memory processes (encoding and comparison) are reflected as varying responses in the two alpha frequency bands.

Acoustic Stimulation↗

PubMed2002

Semantic clustering in verbal fluency: schizophrenic patients versus control participants.

BACKGROUND: Schizophrenic patients generate fewer words than healthy controls during verbal fluency tasks. The structure of output may explain why patients generate fewer exemplars. METHODS: Twenty-four healthy controls and 24 patients with schizophrenia participated in six, 3 min semantic fluency tasks. In a subsequent session, participants were given cards, each printed with one of their own words generated from previous fluency tasks. Participants were to sort the cards into categories (e.g. subcategories of 'animals'), thus defining their own semantic subcategories of words, and thereby eliminating experimenter assumptions about word relatedness. These clusters were matched with fluency output of each participant. The time spent searching through semantic networks within clusters and switching to other clusters when locating and producing associated words were measured. RESULTS: Patients produced fewer words and spent more time switching to words within clusters and to different clusters than controls, but otherwise response profiles were similar. Although controls returned more frequently to clusters and consequently made more switches between these clusters than patients, this group difference disappeared when the total number of words produced was covaried. CONCLUSIONS: Consistent with previous literature, patients produced fewer words and made more errors than controls. The absence of a group difference in number of different clusters or mean number of items per cluster suggests that patients are similar to controls with respect to number of ideas in their semantic network. Patients' longer between-cluster switching times indicate a general slowness that may be attributed to difficulties finding new words within a semantic field.

Adult↗

PubMed2005

Testing the role of semantic similarity in syntactic development.

The study explored early syntactic development, and tested the hypothesis that children use similarity of meaning in order to move beyond the learning of individual item-based multiword constructions. The first 6 types of verb-object (VO) constructions in Hebrew-speaking children were analysed for the occurrence of transfer of learning and facilitation, as well as for the semantic similarity of the direct objects (DO). Longitudinal naturalistic speech corpora of 20 children (1;06-2;06) were analysed. We found facilitation (increased rate of learning) among the first 6 types of VO constructions (each type built on a different verb) as evidenced by the accelerating growth curves. Next, we measured the semantic similarity of the DOs using an 8-category system including Patient, Theme and Object of Result. The first 6 DO types represented 3.95 different semantic roles. On the average, after the first VO construction was learned, 3 out of the following 5 constructions produced were not preceded by another VO construction where the DO was of the same semantic category. The results indicate that facilitation of learning of early syntax is most probably NOT mediated by semantic similarity.

Child Language↗

PubMed1995

Semantic network abnormality predicts rate of cognitive decline in patients with probable Alzheimer's disease.

The present study examined the relationship between rate of cognitive decline in patients with Alzheimer's disease (AD) and the integrity of the network of associations that comprise their semantic knowledge. The integrity of the semantic network of 12 AD patients was determined by comparing their networks to a standard normal control network derived with Pathfinder analysis, a multidimensional graphic analysis technique. A simple linear regression analysis, comparing the degree of semantic network deterioration with rate of cognitive decline as measured by the difference between the Dementia Rating Scale (DRS) scores obtained at the time of the testing of semantic knowledge (Year 1) and one year later (Year 2), was highly significant (r2 = .84; p < .001). These results suggest that a sensitive measure of the structural deterioration of semantic knowledge may be useful for predicting the rate of progression of cognitive changes in patients with AD.

Aged↗

PubMed2002

Semantic priming in schizophrenia: a review and synthesis.

In this paper, we present a review of semantic priming experiments in schizophrenia. Semantic priming paradigms show utility in assessing the role of deficits in semantic memory network access in the pathology of schizophrenia. The studies are placed in the context of current models of information processing. In this review we include all English-language reports (from peer-reviewed journals) of single-word semantic priming studies involving participants with schizophrenia. The studies to date show schizophrenic patients to exhibit variable semantic priming effects under automatic processing conditions, and consistent impairments under controlled/attentional conditions. We also describe associations with other neurocognitive dysfunction, neurochemical and electrophysiological disturbances, and clinical manifestations (such as thought disorder).

Clinical Trials as Topic↗

PubMed2003

Exploring semantic memory by investigating buildup and release of proactive interference in healthy older adults and individuals with dementia of the Alzheimer type.

There is debate regarding the integrity of semantic memory in dementia of the Alzheimer type (DAT). One view argues that DAT is associated with a breakdown in semantic memory; the other argues that DAT is associated with predominantly preserved semantic memory and a breakdown in retrieval. The classic release from proactive interference (RPI) paradigm was used to shed light on this debate. Individuals with early-stage DAT (n = 36) and healthy older adult controls (n = 45) participated in an RPI paradigm. Each trial was a Brown-Peterson task in which participants read three-word lists, counted (for 0, 3, 6, or 9 s), and recalled the words. Both groups showed significant proactive interference (PI), but the size of the PI was significantly smaller in the DAT group. The group difference in PI may be due to the faster forgetting rate in the DAT group. Both groups showed significant RPI and there was no group difference in size when RPI was considered in terms of PI levels. Both groups showed PI and RPI in prior list intrusions. The DAT group's significant buildup and release of PI based on semantic categories suggest predominantly preserved semantic memory activity, at least, in early-stage DAT individuals.

Aged↗

PubMed2002

Semantic fields in low-functioning autism.

Restricted semantic fields and resultant stimulus overselectivity are often thought to be typical of low-functioning autism, as is a strong visual processing preference. However, these conclusions may in part be an artifact of testing methodology. A 12-year-old, low-functioning and nonverbal autistic boy was tested on an auditory word-to-picture selection task. The picture foils were chosen to have visual features, semantic features, both, or neither in common with the correct answer. Errors were made more often to semantically than to visually related items, and he showed generalization to items that had not been explicitly trained. This is taken as evidence that his semantic fields are broader than otherwise apparent, and that he was capable of expanding his semantic representations independently of specific training.

Acoustic Stimulation↗

PubMed1995

Semantic processing and memory for attended and unattended words in dichotic listening: behavioral and electrophysiological evidence.

Thirty-two Ss studied words presented to 1 ear, while ignoring a concurrent word list presented to the opposite ear. The N400 component of the event-related potentials elicited by attended words was modulated by semantic priming between successive words. The N400 elicited by unattended words was insensitive to semantic manipulation. Recognition memory was better for attended than for unattended words. However, the percentage of false positives was elevated equally for lures that were semantically related to "old" words, whether they had been attended or unattended. Words that were initially attended induced similar repetition effects in a lexical decision task as words that were initially unattended. Hence, both attended and unattended words are semantically processed and activate semantic representations. However, attended words from traces that are subsequently more available to conscious recollection than unattended words.

Adult↗

PubMed2000

Word-based grouping affects the prime-task effect on semantic priming.

Semantic priming between words is reduced or eliminated if a low-level task such as letter search is performed on the prime word (the prime task effect), a finding used to question the automaticity of semantic processing of words. This idea is critically examined in 3 experiments with a new design that allows the search target to occur both inside and outside the prime word. The new design produces the prime task effect (Experiment 1) but shows semantic negative priming when the target letter occurs outside the prime word (Experiments 2 and 3). It is proposed that semantic activation and priming are dissociable and that inhibition and word-based grouping are responsible for reduction of semantic priming in the prime task effect.

Adult↗

PubMed1993

Responses to anomalous gestural sequences by a language-trained dolphin: evidence for processing of semantic relations and syntactic information.

This study examined the responses of a bottlenosed dolphin (Tursiops truncatus) to "normal" (semantically and syntactically correct) sequences of gestures and to anomalous sequences given within an artificial gestural language highly familiar to the animal. Anomalous sequences violated the semantic rules or syntactic constraints of the language. The dolphin discriminated anomalous from normal sequences in that rejections (refusals to respond) occurred to some anomalous sequences but never to normal sequences. Rejections rarely occurred, however, if the anomalous sequence contained a subset of gestures that would comprise a normal unit if joined together. Such units were typically perceived by the dolphin and responded to even if they consisted of gestures that were not sequentially adjacent. All semantic elements of a sequence were processed by the dolphin in relation to other elements before the dolphin organized its final response. The results show the importance of both semantic properties and semantic relations of the referents of the gestures and of syntactic (ordering) constraints in the dolphin's interpretations of the anomalies.

Animal Communication↗

PubMed1991

Long-lasting perceptual priming and semantic learning in amnesia: a case experiment.

An investigation of perceptual priming and semantic learning in the severely amnesic subject K.C. is reported. He was taught 64 three-word sentences and tested for his ability to produce the final word of each sentence. Despite a total lack of episodic memory, he exhibited (a) strong perceptual priming effects in word-fragment completion, which were retained essentially in full strength for 12 months, and (b) independent of perceptual priming, learning of new semantic facts, many of which were also retained for 12 months. K.C.'s semantic learning may be at least partly attributable to repeated study trials and minimal interference during learning. The findings suggest that perceptual priming and semantic learning are subserved by two memory systems different from episodic memory and that both systems (perceptual representation and semantic memory) are at least partially preserved in some amnesic subjects.

Adult↗

PubMed1993

Access to word meanings during spoken language comprehension: effects of sentential semantic context.

In 3 cross-modal priming experiments, we investigated whether access to a word's meaning is affected by the semantic context in which it is heard or is exhaustive and context-independent. We probed access of nonassociated semantic properties and normatively associated words before and after prime offset. Whereas associated targets were primed context-independently, access to semantic property targets was affected by the sentential context. Semantic property targets showed greater priming in a sentence biasing to a specific semantic property than in a neutral condition, even when this bias made the target property irrelevant rather than relevant. These results cannot be accounted for by current exhaustive access or context-dependency theories of lexical access.

Adolescent↗

PubMed1997

Electrophysiological evidence on the time course of semantic and phonological processes in speech production.

The temporal properties of semantic and phonological processes in speech production were investigated in a new experimental paradigm using movement-related brain potentials. The main experimental task was picture naming. In addition, a 2-choice reaction go/no-go procedure was included, involving a semantic and a phonological categorization of the picture name. Lateralized readiness potentials (LRPs) were derived to test whether semantic and phonological information activated motor processes at separate moments in time. An LRP was only observed on no-go trials when the semantic (not the phonological) decision determined the response hand. Varying the position of the critical phoneme in the picture name did not affect the onset of the LRP but rather influenced when the LRP began to differ on go and no-go trials and allowed the duration of phonological encoding of a word to be estimated. These results provide electrophysiological evidence for early semantic activation and later phonological encoding.

Adult↗