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PubMed2000

Complex semantic processing in old age: does it stay or does it go?

Old adults' (N = 24) and young adults' (N = 24) speed of producing exemplars of semantic categories (i.e., semantic fluency) varying in difficulty was assessed both in a standard condition and in a "set-switching" condition where exemplars had to be produced from 2 categories in an alternating manner. "Retrieval-position function" parameters were used to assess speed of semantic access independent of nonsemantic factors. Results suggested age effects in nonsemantic components but not in semantic retrieval per se. Also, age deficits in set switching were relatively subtle. Findings are discussed with relation to issues of domain specificity of age effects as well as of the role of executive control during semantic retrieval and age differences therein.

Adult↗

PubMed1991

Lexical but not semantic priming in Alzheimer's disease.

The hypothesis that patients with Alzheimer's disease (AD) have a disturbance in semantic processing was tested using a new lexical-priming task, threshold oral reading. Healthy elderly controls showed significant effects of priming for word pairs that are associatively related (words that reliably co-occur in word association tests) and for word pairs that are semantically related (high-frequency exemplars that belong to the same superordinate category but are not high-frequency associates). AD patients showed effects of priming for associatively related words but not for word pairs that are related only by shared semantic features. These results are consistent with the hypothesis that semantic processing is impaired in AD and suggest that independent networks of relationships among words and among concepts in semantic memory may be differentially disrupted with various forms of brain damage.

Aged↗

PubMed1993

Why do semantic priming effects increase in old age? A meta-analysis.

This study reports a meta-analysis comparing the size of semantic priming effects on young and older adults' lexical decision and pronunciation latency. The analysis included 15 studies with 49 conditions varying the semantic relatedness of a prime stimulus (single word or whole sentence) and a target word. An effect-size analysis on the difference between young and older adults' semantic priming effect (unrelated minus related latency) indicated that semantic priming effects are reliably larger for older than for young adults. There was no evidence for nonhomogeneity in this age difference across the different conditions. The relationship between young and older adults' semantic priming effects was described by a function with a positive intercept and a slope of 1.0. This pattern of findings favors aging models postulating process-specific slowing rather than general cognitive slowing.

Adult↗

PubMed1998

Lexical semantic and associative priming in Alzheimer's disease.

Semantic memory impairment was investigated in patients with probable Alzheimer's disease (AD) using a threshold oral word reading task to assess priming of different lexical relationships. Healthy elderly controls showed significant priming for associatively related nouns (tempest-teapot) and also for nouns semantically related either because both designate basic-level exemplars of a common superordinate category (cousin-nephew) or because the target names the superordinate category of the prime (daughter-relative). AD patients, in contrast, showed preserved priming of lexical associates but impaired priming of certain semantic relationships. They showed no priming between words designating coordinate exemplars within a category, despite preserved priming of the superordinate category label. Findings are consistent with the view that at least part of the semantic deficit in AD is due to disruption of semantic knowledge that affects relationships among basic-level concepts, more than the relationships between these concepts and their corresponding superordinate category of membership.

Adult↗

PubMed1999

The differentiation of semantic dementia and frontal lobe dementia (temporal and frontal variants of frontotemporal dementia) from early Alzheimer's disease: a comparative neuropsychological study.

The authors compared age-matched groups of patients with the frontal and temporal lobe variants of frontotemporal dementia (FTD; dementia of frontal type [DFT] and semantic dementia), early Alzheimer's disease (AD), and normal controls (n = 9 per group) on a comprehensive neuropsychological battery. A distinct profile emerged for each group: Those with AD showed a severe deficit in episodic memory with more subtle, but significant, impairments in semantic memory and visuospatial skills; patients with semantic dementia showed the previously documented picture of isolated, but profound, semantic memory breakdown with anomia and surface dyslexia but were indistinguishable from the AD group on a test of story recall; and the DFT group were the least impaired and showed mild deficits in episodic memory and verbal fluency but normal semantic memory. The frontal and temporal presentations of FTD are clearly separable from each other and from early AD.

Age Factors↗

PubMed2001

Object naming and semantic knowledge in temporal lobe epilepsy.

Object-naming impairment is common among temporal lobe epilepsy (TLE) patients, but other aspects of semantic memory have received limited attention in this population. This study examined object-naming ability and depth of semantic knowledge in healthy controls (n = 29) and patients with early onset TLE (n = 21). After administration of the Boston Naming Test (BNT), the authors asked participants to provide detailed definitions of 6 BNT objects. The TLE group demonstrated a significant deficit relative to controls in both object-naming ability and semantic knowledge for the target objects, even after controlling for IQ. In a multiple regression analysis that included other neuropsychological test scores as independent variables, the semantic knowledge score was the only significant predictor of patients' object-naming performance. Thus, at the group level, early onset TLE patients have a semantic knowledge deficit that contributes to dysnomia.

Adolescent↗

PubMed2004

Structure and deterioration of semantic memory: a neuropsychological and computational investigation.

Wernicke (1900, as cited in G. H. Eggert, 1977) suggested that semantic knowledge arises from the interaction of perceptual representations of objects and words. The authors present a parallel distributed processing implementation of this theory, in which semantic representations emerge from mechanisms that acquire the mappings between visual representations of objects and their verbal descriptions. To test the theory, they trained the model to associate names, verbal descriptions, and visual representations of objects. When its inputs and outputs are constructed to capture aspects of structure apparent in attribute-norming experiments, the model provides an intuitive account of semantic task performance. The authors then used the model to understand the structure of impaired performance in patients with selective and progressive impairments of conceptual knowledge. Data from 4 well-known semantic tasks revealed consistent patterns that find a ready explanation in the model. The relationship between the model and related theories of semantic representation is discussed.

Anomia↗

PubMed2003

Phonological encoding is not contingent on semantic feature retrieval: an electrophysiological study on object naming.

In the present study, the authors examined with event-related brain potentials whether phonological encoding in picture naming is mediated by basic semantic feature retrieval or proceeds independently. In a manual 2-choice go/no-go task the choice response depended on a semantic classification (animal vs. object) and the execution decision was contingent on a classification of name phonology (vowel vs. consonant). The introduction of a semantic task mixing procedure allowed for selectively manipulating the speed of semantic feature retrieval. Serial and parallel models were tested on the basis of their differential predictions for the effect of this manipulation on the lateralized readiness potential and N200 component. The findings indicate that phonological code retrieval is not strictly contingent on prior basic semantic feature processing.

Adolescent↗

PubMed2005

Enemies and friends in the neighborhood: orthographic similarity effects in semantic categorization.

Studies investigating orthographic similarity effects in semantic tasks have produced inconsistent results. The authors investigated orthographic similarity effects in animacy decision and in contrast with previous studies, they took semantic congruency into account. In Experiments 1 and 2, performance to a target (cat) was better if a previously studied neighbor (rat) was congruent (i.e., belonged to the same animate-inanimate category) than it was if it was incongruent (e.g., mat). In Experiments 3 and 4, performance was better for targets with more preexisting congruent neighbors than for targets with more preexisting incongruent neighbors. These results demonstrate that orthographic similarity effects in semantic categorization are conditional on semantic congruency. This strongly suggests that semantic information becomes available before orthographic processing has been completed.

Humans↗

PubMed2005

Cumulating retrieval inhibition in semantic and lexical domains.

In 3 experiments the authors examined changes in successive exemplar generation percentages within categories defined semantically (e.g., fruit-P, fruit-A, fruit-M) and by 1st letter (e.g., insect-C, sport-C, car-C), with a mixed control condition (e.g., fruit-P, insect-C, disease-M). Retrieval success declined across 12 successive items in both semantic and letter categories, with no change for the mixed condition. This retrieval inhibition is unrelated to taxonomic frequency of exemplars within either letter or semantic categorical structures. Furthermore, semantic retrieval inhibition appears to be long lasting, suggested by the decline in retrieval percentage across successive 12-item blocks in both the mixed and letter conditions. The authors suggest that different mechanisms underlie the inhibition found in the semantic (suppression) and letter (interference) conditions.

Discrimination Learning↗

PubMed2006

Eye movements to pictures reveal transient semantic activation during spoken word recognition.

Two experiments explore the activation of semantic information during spoken word recognition. Experiment 1 shows that as the name of an object unfolds (e.g., lock), eye movements are drawn to pictorial representations of both the named object and semantically related objects (e.g., key). Experiment 2 shows that objects semantically related to an uttered word's onset competitors become active enough to draw visual attention (e.g., if the uttered word is logs, participants fixate on key because of partial activation of lock), despite that the onset competitor itself is not present in the visual display. Together, these experiments provide detailed information about the activation of semantic information associated with a spoken word and its phonological competitors and demonstrate that transient semantic activation is sufficient to impact visual attention.

Attention↗

PubMed2006

The influence of dopamine on semantic activation in Parkinson's disease: evidence from a multipriming task.

Research has suggested that semantic processing deficits in Parkinson's disease (PD) are related to striatal dopamine deficiency. As an investigation of the influence of dopamine on semantic activation in PD, 7 participants with PD performed a lexical-decision task when on and off levodopa medication. Seven healthy controls matched to the participants with PD in terms of sex, age, and education also participated in the study. By use of a multipriming paradigm, whereby 2 prime words were presented prior to the target word, semantic priming effects were measured across stimulus onset asynchronies (SOAs) of 250 ms and 1,200 ms. The results revealed a similar pattern of priming across SOAs for the control group and the PD participants on medication. In contrast, within-group comparisons revealed that automatic semantic activation was compromised in PD participants when off medication. The implications of these results for the neuromodulatory influence of dopamine on semantic processing in PD are discussed.

Aged↗

PubMed2006

How does the brain support script comprehension? A study of executive processes and semantic knowledge in dementia.

The neuropsychological substrate of scripts, routines which guide much of human behavior, is unclear. We propose a model of script comprehension characterized by the interaction of semantic knowledge for script content, and executive resources that organize this knowledge into goal directed behavior. We examined these neuropsychological components by asking participants with Alzheimer's disease (AD) and frontotemporal dementia (behavioral disorder/dysexecutive syndrome (BDD) and semantic dementia (SD) subtypes), to judge the coherence of four-phrase scripts. The BDD group detected significantly fewer sequencing errors than semantic errors; the AD and SD groups detected these errors with equal frequency. Independent semantic measures predicted both semantic and sequencing script errors, while executive measures predicted sequencing errors only. Findings support a multi-component model of script comprehension.

Aged↗

PubMed2005

The effect of semantic representation on toddlers' word retrieval.

PURPOSE: This study tested the hypothesis that depth of semantic representation influences toddlers' word retrieval. METHOD: Nineteen toddlers participated under 3 word learning conditions in this longitudinal study. Gestures cued attention to object shape (SHP) or function (FNC) in the experimental conditions. No semantic cue was provided under a control condition (CTL). Word learning conditions occurred on each of 3 days. On the 4th day, word retrieval was assessed across 3 levels of scaffolding (uncued picture naming, cued picture naming, picture recognition). Evidence of semantic representation was provided at fast and slow mapping intervals. RESULTS: Less scaffolding was necessary for word retrieval (uncued and cued naming) under experimental conditions than under the CTL condition. However, more SHP than FNC condition targets were retrieved for uncued picture naming. This latter difference may be related to the superior fast mapping of targets under the SHP condition. Toddlers stated object functions (slow mapping) comparably in the experimental conditions, but this was superior to CTL condition performance. CONCLUSIONS: Word retrieval is a continuous behavior that is positively influenced by semantic representation. Semantic knowledge of objects can be enriched by shape or function gestures, thereby improving toddlers' object word productions. Shape cues appear to be more effective for this purpose.

Analysis of Variance↗

PubMed1999

Model-based semantic treatment for naming deficits in aphasia.

An interactive activation model for picture naming was used to guide treatment of a semantic-level deficit in 4 individuals with aphasia and severe picture-naming problems. Participants exhibited a profile consistent with Broca's aphasia with severe naming deficits, part of which was attributable to a semantic impairment based on testing of the lexical system. A semantic-based treatment was used to train naming of nouns in two semantic categories using a single-participant multiple baseline across behaviors and participants. Additional treatment, which included orthographic and phonological information about target words, then was applied. Treatment responses and error patterns demonstrated that semantic treatment resulted in improved naming of both trained and untrained items for 2 of 4 participants. Two participants did not show improved naming until treatment emphasizing the phonological form of the word was provided. This study demonstrates the utility of using an interactive activation model to plan treatment based on levels of disruption in the lexical processing system.

Aphasia, Broca↗

PubMed1998

Semantic development of African-American children prenatally exposed to cocaine.

Semantic content categories were described for the single word, multiple word, and verb relation utterances of 22 African-American 2-year-olds during a 90-min laboratory session. Half of the toddlers had been exposed prenatally to cocaine and half were unexposed, as documented by biological assay in the newborn period. The exposed and unexposed groups were carefully matched on demographic, medical, and proximal caregiving variables. Children's spontaneous utterances were transcribed from audio- and videotapes during the laboratory session and scored for semantic features by a team of reliable coders who were masked to child exposure status. General productive language features (utterance length, verbosity, and intelligibility) were also assessed. To evaluate general language and cognitive skills, the toddlers were evaluated with the Sequenced Inventory of Communicative Development-Revised (SICD-R) and the Bayley Scales of Infant Development (BSID). Although exposed and nonexposed toddlers exhibited similar sequences of semantic development, the exposed toddlers were more restricted and delayed in their semantic representations. No significant group differences were observed, however, for structural features of language (e.g., utterance length, distribution of utterance types) or for children's general language and cognitive functioning as assessed by standardized assessments (i.e., SICD-R, BSID). Thus, a history of prenatal cocaine exposure and associated risk factors (e.g., prenatal exposure to alcohol, diminished birth weight) are related to delays in early semantic development. Proposed diagnostic and treatment strategies are discussed.

Black or African American↗

PubMed2006

Nonconscious semantic processing of emotional words modulates conscious access.

Whether masked words can be processed at a semantic level remains a controversial issue in cognitive psychology. Although recent behavioral studies have demonstrated masked semantic priming for number words, attempts to generalize this finding to other categories of words have failed. Here, as an alternative to subliminal priming, we introduce a sensitive behavioral method to detect nonconscious semantic processing of words. The logic of this method consists of presenting words close to the threshold for conscious perception and examining whether their semantic content modulates performance in objective and subjective tasks. Our results disclose two independent sources of modulation of the threshold for access to consciousness. First, prior conscious perception of words increases the detection rate of the same words when they are subsequently presented with stronger masking. Second, the threshold for conscious access is lower for emotional words than for neutral ones, even for words that have not been previously consciously perceived, thus implying that written words can receive nonconscious semantic processing.

Consciousness↗

PubMed1988

Lexical and semantic priming deficits in patients with Alzheimer's disease.

Two experiments utilizing priming procedures examined the status of semantic memory in demented and amnesic patients. In the first investigation, lexical priming was assessed in patients with dementia of the Alzheimer type (DAT), Huntington's Disease (HD), alcoholic Korsakoff's syndrome (KS), and in intact control subjects. Subjects were first exposed to a list of words in a rating task and then required to complete three-letter stems with the "first word that comes to mind". Half of the stems could be completed with the previously presented words and the other half were used to assess baseline guessing rates. Recall and recognition of incidentally exposed words was also assessed. Although all three patient groups were impaired on tests of recall and recognition, only the DAT patients exhibited a priming deficit on the stem-completion task. In the second experiment, DAT, HD, and intact control subjects were administered a semantic priming test which required the subject to "free associate" to the first words of previously presented semantically associated word pairs. The results for this association task showed that DAT patients were significantly less likely to produce the second word of the semantically related pair than were the other subject groups. The results of these two experiments suggest that the memory capacities of DAT patients are characterized by a breakdown in the structure of semantic memory and that this impairment is evident on some "automatic" as well as "effortful" processing tasks.

Adult↗