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PubMed1993

Changes in semantic memory in early stage Alzheimer's disease patients.

The types and number of exemplars of categories that are retrieved from semantic memory differentiate elderly normal controls and early stage Alzheimer's disease (AD) patients. Elderly normal controls generated more uncommon exemplars from closed semantic categories (fruits and vegetables) than did AD patients 2 1/2 years prior to the presumed onset of AD. AD patients, however, were just as productive as elderly normal controls in generating associations to open categories (letters). The findings suggest that one of the early cognitive symptoms of AD is changes in availability of uncommon exemplars of semantic networks.

Aged↗

PubMed2002

The role of semantic knowledge in short-term memory.

In this paper we examine the role of stored semantic knowledge in recall from short-term memory. We assessed the performance of a patient (FK), who showed a consistent lack of semantic knowledge for some words ('unknown') but not others ('known') on a range of serial recall tasks using both spoken and written words. Overall, FK was significantly better at recalling lists of known compared with unknown words. His recall of unknown words was characterized by numerous phonological errors, such as repeating 'bear skunk' as 'bunk scare'. FK showed a relatively normal primacy effect in immediate recall, but a striking lack of a recency effect. This pattern of performance is useful for constraining theoretical accounts of language production and verbal short-term memory and for understanding the role that long-term semantic knowledge may play in maintaining information in short-term memory.

Adult↗

PubMed1994

Brain potentials and the availability of semantic and phonological codes over time.

ERPs were recorded from subjects performing semantic and rhyme matching tasks using either spoken words, printed words or pictures as stimuli. Mismatches enhanced N400 (in the semantic task) and N450 (in the rhyme task). Onset and peak latencies were shorter for N450 than for N400 with spoken words; this relationship was inverted for pictures. Thus these latencies could index availability of semantic and phonological codes. For printed words, the latencies were shorter for N400 than N450, a result that supports direct-access modes of reading with late phonological code activation. The longer latencies found for N400 and N450 to pictures could suggest longer initial decoding for pictures with respect to words.

Adolescent↗

PubMed1994

The role of the left prefrontal cortex in verbal processing: semantic processing or willed action?

This study was designed to test the various proposed explanations (semantic processing, willed action, production of a spoken response) for the unilateral activation of the left prefrontal cortex noted in PET studies of verbal processing. Twenty subjects underwent 15O-water PET scans while undertaking a lexical task (detecting the letter 'a' in visually presented words) and a semantic task (categorizing nouns into living/non-living). The semantic task resulted in a significant unilateral left dorsolateral prefrontal activation. This finding suggests that the left inferior prefrontal cortex is the anatomical region involved in 'working with meaning', and that the activation does not reflect willed action, is not task-specific and is not attributable to the requirements of a spoken response.

Adult↗

PubMed2001

Semantic acquisition without memories: evidence from transient global amnesia.

Transient global amnesia (TGA), characterised by a profound anterograde amnesia, is a model of interest to study the acquisition of novel meanings independent of episodic functioning. Three patients were tested during a TGA attack, two in the early recovery phase and the third during the acute phase of TGA, with a semantic priming task involving a restructuring process of conceptual knowledge. During TGA, all patients demonstrated priming effects. Results obtained the day after the episode with the same task showed that these effects persisted at least one day. Episodic memory seems not to be critical for the formation of novel connections among unrelated semantic representations, in accordance with Tulving's model of memory, i.e. episodic memory is not necessary for the acquisition of semantic information.

Acute Disease↗

PubMed2002

Regional brain activations differ for semantic features but not categories.

Is human semantic knowledge neurally organised according to either category (e.g. living non-living) or attribute type (e.g. perceptual non-perceptual information)? Normal subjects were scanned using PET during a novel semantic production task, in which they generated either perceptual or non-perceptual information in response to names of living or non-living concepts. Analyses of blood flow in the temporal lobes revealed no significant differences associated with responses to living non-living concepts. Comparisons between retrieval of perceptual non-perceptual information, however, revealed significantly greater blood flow in left posterior inferior temporal cortex and right fusiform cortex associated with perceptual information and in left middle temporal cortex with non-perceptual information. These findings support a primarily attribute-based neural organisation of semantic knowledge.

Adult↗

PubMed2002

Semantic factors influence multisensory pairing: a transcranial magnetic stimulation study.

It is traditionally assumed that temporal and spatial factors determine whether information provided by different sensory modalities is combined in a single percept. However, neuropsychological reports of selective damage to audio-visual integration and recent neurophysiological results suggest that semantic factors related to the content of the stimuli could also play a role. As a means of extending evidence provided by neuropsychological dissociations we set up a direct comparison of two kinds of audio-visual pairs with different semantic properties and used transcranial magnetic stimulation (TMS). We investigated the selective impact of TMS on two kinds of audio-visual pairings presented under identical spatio-temporal conditions (face-voice and tone-shape pairings). Our results show that TMS applied over the left posterior parietal cortex at 200 ms disrupted audio-visual integration for the tone-shape pairings but not for the face-voice ones. Our data are consistent with neuropsychological findings and indicate that besides the well-known dimensions of spatial and temporal contiguity, content is an important determinant of audio-visual integration. Our study also illustrates the usefulness of TMS for addressing the role of semantic factors in multi-sensory perception

Acoustic Stimulation↗

PubMed1999

Sensitivity to semantic cuing: an index of episodic memory dysfunction in early Alzheimer disease.

Alzheimer disease (AD) is characterized by episodic memory impairment. This study was aimed at assessing various aspects of episodic memory, and particularly sensitivity to semantic cuing, in patients with various degrees of cognitive deterioration, compared with normal elderly subjects. One hundred thirty-one patients, subdivided into four subgroups as a function of their Mini-Mental State Examination score, were included. All subjects, including 20 normal elderly subject, were given an episodic memory test with controlled encoding and selective reminding. The subgroups of patients were homogeneous in terms of free recall and recognition, but differed in terms of responsiveness to cuing by semantic categories corresponding to the to-be-remembered items. The data confirmed that a severe amnesic syndrome occurs very early in AD, even in a subgroup of patients who did not meet the criteria for dementia. The data indicated that free recall performance, characterized in all subgroups by a floor effect, is not likely to be an appropriate index in pharmacological trials. By contrast, sensitivity to semantic cuing seemed relatively preserved in the early stages, and decreased with the progression of the disease. This index would be the most sensitive index of episodic memory in AD.

Aged↗

PubMed2006

Effects of childhood hearing loss on organization of semantic memory: typicality and relatedness.

OBJECTIVE: The purpose of this research was to study how early childhood hearing loss affects development of concepts and categories, aspects of semantic knowledge that allow us to group and make inferences about objects with common properties, such as dogs versus cats. We assessed category typicality and out-of-category relatedness effects. The typicality effect refers to performance advantage (faster reaction times, fewer errors) for objects with a higher number of a category's characteristic properties; the out-of-category relatedness effect refers to performance disadvantage (slower reaction times and more errors) for out-of-category objects that share some properties with category members. DESIGN: We applied a new children's speeded category-verification task (vote "yes" if the pictured object is clothing). Stimuli were pictures of typical and atypical category objects (e.g., pants, glove) and related and unrelated out-of-category objects (e.g., necklace, soup). Participants were 30 children with hearing impairment (HI) who were considered successful hearing aid users and who attended regular classes (mainstreamed) with some support services. Ages ranged from 5 to 15 yr (mean = 10 yr 8 mo). Results were related to normative data from . RESULTS: Typical objects consistently showed preferential processing (faster reaction times, fewer errors), and related out-of-category objects consistently showed the converse. Overall, results between HI and normative groups exhibited striking similarity. Variation in speed of classification was influenced primarily by age and age-related competencies, such as vocabulary skill. Audiological status, however, independently influenced performance to a lesser extent, with positive responses becoming faster as degree of hearing loss decreased and negative responses becoming faster as age of identification/amplification/education decreased. There were few errors overall. CONCLUSIONS: The presence of a typicality effect indicates that 1) the structure of conceptual representations for at least one category in the HI group was based on characteristic properties with an uneven distribution among members, and 2) typical objects with a higher number of characteristic properties were more easily accessed and/or retrieved. The presence of a relatedness effect indicates that the structure of representational knowledge in the HI group allowed them to appreciate semantic properties and understand that properties may be shared between categories. Speculations linked the association 1) between positive responses and degree of hearing loss to an increase in the quality, accessibility, and retrievability of conceptual representations with better hearing; and 2) between negative responses and age of identification/amplification/education to an improvement in effortful, postretrieval decision-making proficiencies with more schooling and amplified auditory experience. This research establishes the value of our new approach to assessing the organization of semantic memory in children with HI.

Adolescent↗

PubMed2005

Semantic sentence processing reflected in the event-related potentials of one- and two-year-old children.

The present study used the N400, an electrophysiological correlate of semantic processing, to investigate 19- and 24-month-old children's ability to integrate the meaning of words in a sentential context. Children listened passively to semantically appropriate sentences and to sentences in which the object noun violates the selection restriction of the verb. The event-related potentials of both age groups revealed an N400 on inappropriate object nouns. This indicates that the children are able to semantically integrate words into sentence contexts. Furthermore, the result implies that selection restrictions are part of the children's first verb representations.

Age Factors↗

PubMed2005

Automatic image orientation detection via confidence-based integration of low-level and semantic cues.

Automatic image orientation detection for natural images is a useful, yet challenging research topic. Humans use scene context and semantic object recognition to identify the correct image orientation. However, it is difficult for a computer to perform the task in the same way because current object recognition algorithms are extremely limited in their scope and robustness. As a result, existing orientation detection methods were built upon low-level vision features such as spatial distributions of color and texture. Discrepant detection rates have been reported for these methods in the literature. We have developed a probabilistic approach to image orientation detection via confidence-based integration of low-level and semantic cues within a Bayesian framework. Our current accuracy is 90 percent for unconstrained consumer photos, impressive given the findings of a psychophysical study conducted recently. The proposed framework is an attempt to bridge the gap between computer and human vision systems and is applicable to other problems involving semantic scene content understanding.

Algorithms↗

PubMed2002

Semantic generation can cause episodic forgetting.

The repeated retrieval of a subset of previously learned items can cause forgetting of the nonretrieved items. The study reported here investigated whether retrieval-induced forgetting generalizes to a situation in which the retrieved and nonretrieved items are not part of the same experiential episode and task. Subjects learned an item list that they had to recall later in the experiment. In a separate intermediate phase, they repeatedly generated related items from semantic memory, or were presented the same items intact for study. Only the semantic generation of items, and not their presentation for study, induced forgetting of the initially learned items. This result indicates that, first, semantic generation can cause recall-specific episodic forgetting and, second, retrieval-induced forgetting can occur even if the retrieved and nonretrieved items belong to different experiential episodes and tasks. Connections of the present results to other memory phenomena, such as part-set cuing and the generation effect, social cognition, and eyewitness memory, are discussed.

Humans↗

PubMed2004

Comparing arithmetic and semantic fact retrieval: effects of problem size and sentence constraint on event-related brain potentials.

Event-related potentials were recorded with 61 electrodes from 16 students who verified either the correctness of single-digit multiplication problems or the semantic congruency of sentences. Multiplication problems varied in size and sentence fragments in constraint. Both semantic and arithmetic incongruencies evoked a typical N400 with a clear parieto-central maximum. In addition, numerically larger problems (8x7), in comparison to smaller problems (3x2), evoked a negativity starting at about 360 ms whose maximum was located over the right temporal-parietal scalp. These results indicate that the arithmetic incongruency and the problem-size effect are functionally distinct. It is suggested that the arithmetic and the semantic incongruency effects are both functionally related to a context-dependent spread of activation in specialized associative networks, whereas the arithmetic problem-size effect is due to rechecking routines that go beyond basic fact retrieval.

Attention↗

PubMed2004

False memories in children. Evidence for a shift from phonological to semantic associations.

Memory illusions in children of three age groups (5-, 8-, and 11-year-olds) were investigated using a modified version of the Deese-Roediger-McDermott (DRM) procedure. Children from each age group falsely recalled nonpresented items related to the study lists. However, the nature of the intrusions varied across the different groups. The 5-year-olds were more likely to falsely recall words that rhymed with the studied items than to recall unrelated items, whereas the 11-year-olds were more likely to falsely recall words that were semantically related to the list theme than to produce either rhyming or unrelated intrusions. Intrusions made by the 8-year-olds were equally likely to be semantic, rhyming, or unrelated to study items. The results are consistent with the notion of a developmental shift from phonological to semantic associations, leading to qualitatively different memory distortions in children of different ages.

Association↗

PubMed1989

Semantic differentials and the process of developing one to measure maternal role competence.

The semantic differential (SD) technique is seen increasingly in studies by nurse investigators. A better understanding of this technique will assist in the appraisal of findings based on SD data. In taking a semantic differential the respondent describes the meaning of a given concept or stimulus by marking a series of bipolar adjective pair scales. Scoring and analysis can proceed in various ways but should not violate the semantic differential's multidimensional nature. The evaluative, potency, and activity dimensions commonly seen in the technique are described. How to construct an SD is explained. The ease with which an SD can be completed makes this technique suitable for clinical populations. The process of developing an SD to measure maternal role competence provides an example of using the technique in a new area of investigation. Factor analysis of the SD to measure the concept myself as a mother revealed that the adjective pairs did not cluster according to the typical SD dimensions. Alternative dimensions are described. These new dimensions gain support from their correlation with other measures of maternal role. The SD provides a promising technique for the measurement of maternal role competence.

Adult↗

PubMed1997

Representations of self and other: a semantic space model.

This article describes a semantic space model of personality. According to the model, representations of facets of the self (e.g., actual self, ideal self) and of others are arrayed in a semantic space, with proximities among representations predicted to be associated with mood, self-evaluation, and broad personality dimensions. The relation of proximities among pairs of representations to personality and mood measures was found to be mediated by the spatial proximity of other representations, indicating that the representations constitute dynamic systems. Proximities among representations were shown to predict self-esteem and self-evaluative moods even after controlling for the contribution of the personality dimensions of Neuroticism, Extraversion, and Agreeableness. Generally, the semantic space model led to better predictions than did several related models concerning representations of self and other.

Affect↗

PubMed2004

The effects of meaningful irrelevant speech and road traffic noise on teachers' attention, episodic and semantic memory.

The aim of the present experiment was to examine the effects of meaningful irrelevant speech and road traffic noise on attention, episodic and semantic memory, and also to examine whether the noise effects were age-dependent. A total of 96 male and female teachers in the age range of 35-45 and 55-65 years were randomly assigned to a silent or the two noise conditions. Noise effects found in episodic memory were limited to a meaningful text, where cued recall contrary to expectations was equally impaired by the two types of noise. However, meaningful irrelevant speech also deteriorated recognition of the text, whereas road traffic noise caused no decrement. Retrieval from two word fluency tests in semantic memory showed strong effects of noise exposure, one affected by meaningful irrelevant speech and the other by road traffic noise. The results implied that both acoustic variation and the semantic interference could be of importance for noise impairments. The expected age-dependent noise effects did not show up.

Adult↗

PubMed1993

Bottle, tulip and wineglass: semantic and structural picture processing by savant artists.

Semantic and structural aspects of picture processing were investigated with graphically gifted mentally handicapped subjects and intellectually normal children. The results suggest that savants as well as controls rely primarily on semantically organised memory schemata when reproducing pictures. A semantically determined strategy also determines picture sorting. The findings indicate that within the domain of expertise there appears to be no difference between savants and normals regarding the nature of the mental structures underlying specific talents. The mental structures on which such talents are based, should therefore be regarded as being relatively independent of the level of general cognitive functioning.

Adolescent↗