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PubMed2006

Name relearning in elderly patients with schizophrenia: episodic and temporary, not semantic and permanent.

INTRODUCTION: Recent reports of lexical-semantic deficits in patients with schizophrenia (Laws, Al-Uzri, & Mortimer, 2000; Laws, McKenna, & Kondel, 1998) suggest that younger patients have problems accessing intact memories and older patients show apparent "loss" of the lexical-semantic memory representations themselves. METHODS: Picture naming for everyday items was examined in a unique series of elderly patients with schizophrenia (n = 10) with a mean illness duration of 45.5 years; and compared with that in patients with probable Alzheimer's disease (n = 18) and elderly healthy controls (n = 27). Naming consistency across time was used as an indicator of whether the schizophrenic patients had difficulty accessing representations or a loss of the representations themselves. Finally, we examined the ability of the schizophrenic patients to relearn the names of unnamed items across four weekly retraining sessions and to retain them at a one month follow-up. RESULTS: The elderly schizophrenic patients were as anomic as patients with probable Alzheimer's disease. Consistency analysis revealed that the patients had storage deficits. Analysis of patient error types was consistent with a semantic deficit. Finally, the schizophrenic patients showed significant improvement with relearning, but this was not maintained at follow-up. CONCLUSIONS: Elderly patients with schizophrenia show a profound and stable anomia. Although name relearning induced some significant gains in naming, these were short-term and reflect episodic rather than semantic reinstatement of representations. Implications for cognitive remediation are discussed.

Aged↗

PubMed2004

Heterogeneity is a fact of category-specific semantic deficits. so? comments on Rosazza, Imbornone, Zorzi, Farina, Chiavari, And Cappa (2003).

The Sensory/Functional Theory, until recently the received explanation of category-specific semantic deficits, has been shown to be at variance with various facts that have emerged about the nature of these deficits. In this context, Rosazza, Imbornone, Zorzi, Farina, Chiavari, and Cappa (2003: The Heterogeneity of Category-Specific Semantic Disorders: Evidence from a New Case. Neurocase, 9, 189-202.) report the case study of a patient, MA, with a purported category-specific semantic deficit for living things compared to nonliving things, and an associated modality-specific impairment that differentially affected visual/perceptual compared to functional/associative knowledge. While acknowledging that the Sensory/Functional Theory cannot account for the existence of category-specific semantic deficits, Rosazza and colleagues (2003) contend that "...the presence of a more severe loss of specific visual rather than functional knowledge could support an interpretation according to the Sensory/Functional Theory" [sic] (p. 200). Our comments are divided into two parts. First, we point out that there is an asymmetry between evidence and theory: if there is clear evidence that "disconfirms" a given theory, evidence that is consistent with the theory cannot be argued to support the theory. Second, we argue that the performance profile of MA could potentially be relevant to other interpretations of category-specific deficits but that theoretical interpretations of the performance profile of patient MA are undermined by a lack of methodological rigor, as well as the generally weak data associated with the case.

Brain Injuries↗

PubMed2005

Phonemic fluency, semantic fluency, and difference scores: normative data for adult Hebrew speakers.

Norms for Hebrew semantic and phonemic fluency were collected in a sample of 369 participants, ranging in age from 18 to 85. Two hundred and sixty nine persons completed both tests and the rest completed only the semantic test. Phonemic fluency was assessed with the use of three letters (bet, gimel, and shin) and semantic fluency with the use of three categories (animals, fruits and vegetables, and vehicles). Scores of individual letters and categories, sum scores, as well as the difference between the semantic and phonemic sum scores are presented for four age groups (18-30, 31-50, 51-70, and 71-85). Results show that age had the greatest effect on fluency performance, level of education was positively correlated to sum scores but contributed little to its prediction beyond the contribution of age, and gender had no significant effect.

Adolescent↗

PubMed1995

Semantic memory in Alzheimer's disease: an analysis of category fluency.

In order to study the strategies of access to semantic knowledge and the status of semantic representation, we analyzed the performance in a semantic fluency task (Animal naming) of 70 patients with probable Alzheimer's disease (AD), including 40 mild AD patients and 30 moderate-severe AD patients, and 35 matched elderly normal control subjects. The total amount of words produced, their lexical frequency, the number and type of errors, as well as the presence and the type of clusters of related animal names were recorded. AD patients produced less animal exemplars than controls. In addition to a lower total number of clusters, the AD patients showed a strong limitation in clusters' selection, producing a limited number of different clusters. While normal subjects produced several different clusters, only farm animals were clustered by AD patients. When the total amount of words was considered, the mean lexical frequency was higher in the AD group. On the other hand, the words produced within clusters were comparable to terms of lexical frequency and number. These data confirm the impairment of AD patients in category fluency tasks, and suggest a degradation of semantic knowledge as the most likely underlying mechanism.

Aged↗

PubMed1995

Memory for related and unrelated words: further evidence on the influence of semantic factors in immediate serial recall.

A number of recent studies have explored the role of long-term memory factors in memory span tasks. The effects of lexicality, frequency, imageability, and word class have been investigated. The work reported in this paper examined the effect of semantic organization on the recall of short lists of words. Specifically, the influence of semantic category on immediate serial recall and the interaction of this variable with articulatory suppression was investigated in three experiments. Experiment 1 compared immediate serial recall performance when lists comprising items from the same semantic category were used (homogeneous condition) with a situation where lists held items from different semantic categories. Experiment 2 examined the same conditions with and without articulatory suppression during item presentation, and Experiment 3 reproduced these conditions with suppression occurring throughout presentation and recall. Results of all three experiments showed a clear advantage for the homogeneous condition. Experiments 2 and 3 showed that the homogeneous category advantage did not depend on the articulatory loop. Furthermore, error analysis indicated that this effect was mainly attributable to better item information recall for the homogeneous condition. These results are interpreted as reflecting a long-term memory contribution to the recall stage of immediate serial recall tasks.

Adult↗

PubMed2001

Semantic priming of person recognition: categorial priming may be a weaker form of the associative priming effect.

An interactive activation and competition account (Burton, Bruce, & Johnston, 1990) of the semantic priming effect in person recognition studies relies on the fact that primes and targets (people) have semantic information in common. However, recent investigations into the type of relationship needed to mediate the semantic priming effect have suggested that the prime and target must be close associates (e.g., Barry, Johnston, & Scanlan, 1998; Young, Flude, Hellawell, & Ellis, 1994). A review of these and similar papers suggests the possibility of a small but non-reliable effect based purely on categorial relationships. Experiment 1 provided evidence that when participants were asked to make a name familiarity decision it was possible to boost this small categorial effect when multiple (four) primes were presented prior to the target name. Results from Experiment 2 indicated that the categorial effect was not due to the particular presentation times of the primes. This boosted categorial effect was shown to cross domains (names to faces) in Experiment 3 and persist in Experiment 4 when the task involved naming the target face. The similarity of the pattern of results produced by the associative priming effect and this boosted categorial effect suggests that the two may be due to the same underlying mechanism in semantic memory.

Facial Expression↗

PubMed2005

Information retrieval and knowledge discovery utilising a biomedical Semantic Web.

Although various ontologies and knowledge sources have been developed in recent years to facilitate biomedical research, it is difficult to assimilate information from multiple knowledge sources. To enable researchers to easily gain understanding of a biomedical concept, a biomedical Semantic Web that seamlessly integrates knowledge from biomedical ontologies, publications and patents would be very helpful. In this paper, current research efforts in representing biomedical knowledge in Semantic Web languages are surveyed. Techniques are presented for information retrieval and knowledge discovery from the Semantic Web that extend traditional keyword search and database querying techniques. Finally, some of the challenges that have to be addressed to make the vision of a biomedical Semantic Web a reality are discussed.

Abstracting and Indexing↗

PubMed2003

Investigating semantic similarity measures across the Gene Ontology: the relationship between sequence and annotation.

MOTIVATION: Many bioinformatics data resources not only hold data in the form of sequences, but also as annotation. In the majority of cases, annotation is written as scientific natural language: this is suitable for humans, but not particularly useful for machine processing. Ontologies offer a mechanism by which knowledge can be represented in a form capable of such processing. In this paper we investigate the use of ontological annotation to measure the similarities in knowledge content or 'semantic similarity' between entries in a data resource. These allow a bioinformatician to perform a similarity measure over annotation in an analogous manner to those performed over sequences. A measure of semantic similarity for the knowledge component of bioinformatics resources should afford a biologist a new tool in their repertoire of analyses. RESULTS: We present the results from experiments that investigate the validity of using semantic similarity by comparison with sequence similarity. We show a simple extension that enables a semantic search of the knowledge held within sequence databases. AVAILABILITY: Software available from http://www.russet.org.uk.

Artificial Intelligence↗

PubMed1992

Semantic dementia. Progressive fluent aphasia with temporal lobe atrophy.

We report five patients with a stereotyped clinical syndrome characterized by fluent dysphasia with severe anomia, reduced vocabulary and prominent impairment of single-word comprehension, progressing to a stage of virtually complete dissolution of the semantic components of language. A marked reduction in the ability to generate exemplars from restricted semantic categories (e.g. animals, vehicles, etc.) was a consistent and early feature. Tests of semantic memory demonstrated a radically impoverished knowledge about a range of living and man-made items. In contrast, phonology and grammar of spoken language were largely preserved, as was comprehension of complex syntactic commands. Reading showed a pattern of surface dyslexia. Autobiographical and day-to-day (episodic) memory were relatively retained. Non-verbal memory, perceptual and visuospatial abilities were also strikingly preserved. In some cases, behavioural and personality changes may supervene; one patient developed features of the Kluver-Bucy Syndrome. Radiological investigations have shown marked focal temporal atrophy in all five patients, and functional imaging by single positron emission tomography and positron emission tomography (one case) have implicated the dominant temporal lobe in all five. In the older literature, such cases would have been subsumed under the rubric of Pick's disease. Others have been included in series with progressive aphasia. We propose the term semantic dementia, first coined by Snowden et al. (1989), to designate this clinical syndrome.

Adult↗

PubMed2001

Identification of famous faces and buildings: a functional neuroimaging study of semantically unique items.

Several functional imaging experiments have clearly established that the fusiform gyri are preferentially responsive to faces, whereas the parahippocampal/lingual gyri are more responsive to buildings. Other studies have demonstrated that famous faces additionally activate the anterior temporal cortex relative to unfamiliar faces, animals, tools, body parts and maps. One explanation for this apparent specialization for known people could be that famous faces are 'semantically unique items'. In other words, they carry unique semantic associations that are not shared by other perceptually similar category members. If this hypothesis is correct, the anterior temporal cortex should also respond to other semantically unique items, such as famous buildings. In this PET study, we investigated the effect of fame (famous relative to non-famous) on activation elicited by famous and non-famous faces and buildings during a same-different matching task. We found that, when the task was held constant, category-specific activations in the fusiform and parahippocampal/lingual areas were not modulated by fame. In contrast, in the left anterior middle temporal gyrus there was an effect of fame that was common to faces and buildings. These results suggest that the identification of famous faces and buildings involves category-specific perceptual processing in the fusiform and parahippocampal/lingual regions, respectively, and shared analysis of unique semantic attributes in the left anterior temporal cortex.

Adolescent↗

PubMed2004

The effects of ageing and Alzheimer's disease on semantic and gender priming.

Normal ageing as well as age-associated pathological conditions, such as Alzheimer's disease, are associated with modifications of language processing. In particular, an impaired performance in semantic tasks, associated with relatively spared syntactic processing, has been suggested to be the hallmark of the language disorder of Alzheimer's disease. The present experiment tests semantic and syntactic aspects of language processing at the same time, using an on-line paradigm, in patients with Alzheimer's disease, compared with elderly and young controls. Normal ageing was associated with a profile of performance, which was slowed but qualitatively comparable with that of young controls. Both gender agreement and congruent sentential semantics resulted in facilitation relative to baseline in young and elderly controls, with no significant interference effects of incongruent grammatical and semantic information. In contrast, Alzheimer's disease patients presented both facilitation and interference effects. These findings suggest that interference effects are amplified by dementia, and may result from defective inhibitory processes due to Alzheimer's disease pathology.

Adult↗

PubMed2005

The pathological basis of semantic dementia.

Semantic dementia is a syndrome of progressive deterioration in semantic memory (knowledge of objects, people, concepts and words). It falls within the clinical spectrum of frontotemporal dementia but its pathology is yet to be studied systematically. This study included 18 consecutive post mortem cases meeting clinical criteria for semantic dementia. Clinic records and diagnostic histopathology were available for all cases; structural neuroimaging, neuropsychology and semi-quantitative histopathology/immunohistochemistry data were analysed where possible. The pathological diagnosis in a clear majority of cases was frontotemporal degeneration with ubiquitin inclusions (n = 13). Eleven of these cases had characteristic motor neuron disease-type inclusions in the dentate gyrus and cerebral cortex. Ubiquitin inclusions were found only in the inferior olivary nucleus in the other two, one of which was the only case to show degeneration of motor tracts and also to have shown evidence of motor neuron disease during life. None of the patients had motor symptoms or signs at presentation. A family history of motor neuron disease was documented in one case. Pick body-positive Pick's disease appeared three times. Two cases had Alzheimer's disease and significant coincidental Alzheimer-type pathology was also found in one of the ubiquitin inclusion cases. One of the Alzheimer's disease patients had changes in white matter signal on scanning, whereas all other scans showed cerebral atrophy only. Semi-quantitative assessment of regional neuronal loss found that anterior and inferior temporal regions bore the brunt of disease across all histopathological subtypes, usually on the left side, implicating this region in semantic processing.

Aged↗

PubMed2006

Semantic dementia and fluent primary progressive aphasia: two sides of the same coin?

Considerable controversy exists regarding the relationship between semantic dementia (SD) and progressive aphasia. SD patients present with anomia and impaired word comprehension. The widely used consensus criteria also include the need for patients to exhibit associative agnosia and/or prosopagnosia: many authors have used the label SD for patients with non-verbal, as well as verbal, semantic deficits on formal testing even if they recognize the objects and people encountered in everyday life; others interpret the criterion of agnosia to require pervasive recognition impairments affecting daily life. According to this latter view, SD patients have pathology that disrupts both a bilateral ventrotemporal-fusiform network (resulting in agnosia) and the left hemisphere language network (resulting in profound aphasia). These authors suggest that this profile is different to that seen in the fluent form of primary progressive aphasia (fPPA), a neurodegenerative disease primarily affecting language function. We present data on seven patients who met the diagnostic criteria for fPPA. All seven showed deficits relative to matched controls on both verbal and non-verbal measures of semantic memory, and these deficits were modulated by degree of anomia, concept familiarity and item typicality. Voxel-based morphometry revealed reduced grey matter density in the temporal lobes bilaterally (more widespread on the left), with the severity of atrophy in the left inferior temporal lobe being significantly related to performance on both the verbal and non-verbal measures. Together these findings suggest that patients who meet the diagnostic criteria for fPPA, can also meet the diagnostic criteria for early-stage SD provided that the impact of concept familiarity and typicality is taken into account. In addition, these findings support a claim that the patients' deficits on both verbal and non-verbal tasks reflect progressive deterioration of an amodal integrative semantic memory system critically involving the rostral temporal lobes, rather than a combination of atrophy in the left language network and a separate bilateral ventrotemporal-fusiform network.

Aged↗

PubMed2005

The neural mechanisms of speech comprehension: fMRI studies of semantic ambiguity.

A number of regions of the temporal and frontal lobes are known to be important for spoken language comprehension, yet we do not have a clear understanding of their functional role(s). In particular, there is considerable disagreement about which brain regions are involved in the semantic aspects of comprehension. Two functional magnetic resonance studies use the phenomenon of semantic ambiguity to identify regions within the fronto-temporal language network that subserve the semantic aspects of spoken language comprehension. Volunteers heard sentences containing ambiguous words (e.g. 'the shell was fired towards the tank') and well-matched low-ambiguity sentences (e.g. 'her secrets were written in her diary'). Although these sentences have similar acoustic, phonological, syntactic and prosodic properties (and were rated as being equally natural), the high-ambiguity sentences require additional processing by those brain regions involved in activating and selecting contextually appropriate word meanings. The ambiguity in these sentences goes largely unnoticed, and yet high-ambiguity sentences produced increased signal in left posterior inferior temporal cortex and inferior frontal gyri bilaterally. Given the ubiquity of semantic ambiguity, we conclude that these brain regions form an important part of the network that is involved in computing the meaning of spoken sentences.

Acoustic Stimulation↗

PubMed2006

The role of semantics and grammatical class in the neural representation of words.

On the basis of neuropsychological and functional imaging evidence, meaning and grammatical class (particularly the verb-noun distinction) have been proposed as organizational principles of linguistic knowledge in the brain. However, previous studies investigating verb and noun processing have been confounded by the presence of systematic correlations between word meaning and grammatical class. In this positron emission tomography study, we investigated implicit word processing using stimuli that allowed the effects of semantic and grammatical properties to be examined independently, without grammatical-semantic confounds. We found that left hemisphere cortical activation during single-word processing was modulated by word meaning, but not by grammatical class. Motor word processing produced significant activation in left precentral gyrus, whereas sensory word processing produced significant activation in left inferior temporal and inferior frontal regions. In contrast to previous studies, there were no effects of grammatical class in left inferior frontal gyrus (IFG). Instead, we found semantic-based differences within left IFG: anterior, but not posterior, left IFG regions responded preferentially to sensory words. These findings demonstrate that the neural substrates of implicit word processing are determined by semantic rather than grammatical properties and suggest that word comprehension involves the activation of modality-specific representations linked to word meaning.

Adult↗

PubMed1995

The reading and semantic link tests: a comparison between probable Alzheimer patients and reading-matched controls.

The performance in those diagnosed as probably suffering from Alzheimer's disease was compared with age-matched controls on a test of semantic and contextual processing relative to a test of silent reading. The former test, the Semantic Link Test, was hypothesized to deteriorate to a greater degree in those suffering from Alzheimer's disease. The controls were matched on reading performance as well as on age. Consequently, a deterioration in performance on the Semantic Link Test for Alzheimer's patients relative to controls was hypothesized. This hypothesis was confirmed, lending further support to the notion that Alzheimer's disease can specifically affect semantic processes.

Aged↗

PubMed1984

Effects of semantically related and unrelated contexts on recognition memory of different-aged adults.

Two experiments were conducted to examine adult age differences in the use of context information. In Experiment 1, the encoding of contextually influenced semantic features was examined, and the encodings of target words by both young and old adults were observed to be influenced by semantic information provided by the context. Older adults did make more semantic confusion errors, however, suggesting less distinctive encoding. Verbal ability also influenced performance, with the difference between ability groups being similar to that between age groups. In Experiment 2, target words were presented in semantically unrelated contexts, and older adults were found not to encode contextual information in this situation. It is hypothesized that the older adults' context effects in Experiment 1 were due to automatic activation of nonspecific word meaning features due to the relation between target and context. When no such familiar context existed, the older adults were less likely to use context information.

Adult↗

PubMed2004

Semantic acquisition in childhood amnesic syndrome: a prospective study.

Amnesic patients can acquire new semantic knowledge despite a profound deficit of episodic memory. Although retrospective studies have been carried out on adults and children, prospective studies have been restricted to adults. The aim of the present work was to assess the acquisition of new semantic knowledge in amnesic children. The semantic protocol, composed of short, illustrated texts, was based on an original methodology which included an assessment of episodic memory on two occasions. Two amnesic children acquired new concepts despite major episodic disturbance, illustrated notably by a lack of recollection in episodic tasks. Our findings lend weight to the assumption that forming new semantic knowledge does not necessarily involve episodic memory, and provide methodological pointers for children's neuropsychological rehabilitation.

Amnesia↗