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PubMed1990

The contribution of morphological and semantic relatedness to repetition priming at short and long lags: evidence from Hebrew.

The effect of morphological repetition at lag 0 and at lag 15 on lexical decision was investigated in Hebrew with three types of relation between prime and target. In the semantic-plus-morphological condition (SM), the prime and the target in each pair were two semantically related derivatives of the same root. In the "pure morphological" condition (M), the prime and the target derived from the same root, but their semantic association was very low, or non-existent. In the semantic priming condition (S), primes and targets were semantically associated but were not morphologically related. The pure semantic relationship produced a significant facilitation at lag 0 that disappeared completely at lag 15. The pure morphological relation produced (smaller but) significant facilitation at lag 0 that was not attenuated at lag 15. When prime and target were semantically as well as morphologically related, the facilitation at lag 0 was similar to semantic priming, whereas at lag 15 it was similar to the pure morphological effect. Significant repetition effects at both lags were also found with non-words that shared the same (nonsensical) root and differed with respect to real derivational affixes. The differential time course for facilitation due to semantic and morphological relatedness suggests distinct underlying processes, although at lag 0 it is possible that semantic relatedness may augment the morphological repetition effect. Morphological repetition probably facilitates the retrieval of lexical information that, under certain circumstances, is necessary for lexical decision.

Adult↗

PubMed1999

Verbal semantic memory in temporal lobe epilepsy.

OBJECTIVES: Temporal lobe epilepsy (TLE) may determine memory difficulties not explained by episodic memory impairment. The present study was aimed to verify the presence of specific semantic memory dysfunctions in TLE and to explore their relations to epilepsy variables. SUBJECTS AND METHODS: Forty-seven patients with lateralized temporal (n = 26) or extra-temporal lobe epilepsy (n = 21) and 23 healthy subjects were compared. Picture Naming and Pointing to a Picture were used to explore expressive and receptive vocabulary and the Semantic Questionnaire evaluated semantic judgment of verbally presented items. The Selective Reminding Procedure for word list learning and Story Recall were used to assess episodic memory. Spontaneous speech and the Token Test controlled for language disturbances, and Raven's Coloured Progressive Matrices were used to evaluate abstract reasoning ability. RESULTS: Multivariate analysis of variance of test scores showed significant impairment of semantic memory in patients with left TLE compared to healthy controls, whereas episodic memory was impaired in left temporal and extra-temporal epilepsy (as measured by word learning) and all epilepsy groups (as measured by Story Recall). In the TLE groups, naming abilities were more compromised than single-word comprehension and semantic judgment - which were not significantly affected. No deficits in language abilities or in abstract reasoning were found in any patient group. Factor analysis of memory tests scores in the patients produced two factors, one semantic and the other episodic. Regression analysis revealed that the semantic factor was related to abstract reasoning, left hemisphere lateralization of seizures, and age of seizure onset; while the episodic factor was related to age. CONCLUSIONS: Left TLE may determine significant verbal semantic memory compromise, maybe due to impaired access to the semantic-lexical storage. In non-aphasic epilepsy patients, comparison of performance on semantic and episodic memory tests may be useful for assessing the nature of memory failures, and may complement clinical and neurophysiological means for defining the epileptic center.

Adolescent↗

PubMed2003

Effects of semantic treatment on verbal communication and linguistic processing in aphasia after stroke: a randomized controlled trial.

BACKGROUND AND PURPOSE: Semantic deficits, deficits in word meaning, have a large impact on aphasic patients' verbal communication. We investigated the effects of semantic treatment on verbal communication in a randomized controlled trial. METHODS: Fifty-eight patients with a combined semantic and phonological deficit were randomized to receive either semantic treatment or the control treatment focused on word sound (phonology). Fifty-five patients completed pretreatment and posttreatment assessment of verbal communication (Amsterdam Nijmegen Everyday Language Test [ANELT]). In an on-treatment analysis (n=46), treatment-specific effects on semantic and phonological measures were explored. RESULTS: Both groups improved on the ANELT, with no difference between groups in overall score (difference, -1.1; 95% confidence interval [CI], -5.3 to 3.1). After semantic treatment, patients improved on a semantic measure (mean improvement, 2.9; 95% CI, 1.2 to 4.6), whereas after phonological treatment, patients improved on phonological measures (mean improvement, 3.0; 95% CI, 1.4 to 4.7, and 3.0; 95% CI, 1.2 to 4.7). CONCLUSIONS: No differences in primary outcome were noted between the 2 treatments. Our findings challenge the current notion that semantic treatment is more effective than phonological treatment for patients with a combined semantic and phonological deficit. The selective gains on the semantic and phonological measures suggest that improved verbal communication was achieved in a different way for each treatment group.

Adult↗

PubMed2003

Semantic and phonological influences on the processing of words and pseudohomophones.

In two experiments, we investigated the relationship between semantics and phonology in the lexical decision task. In the first experiment, lexical decisions to words with large semantic neighborhoods were faster than those to words with sparse semantic neighborhoods. Conversely, this effect of semantic neighborhood was reversed for pseudohomophones (e.g., nale). That is, pseudohomophones based on words with large semantic neighborhoods took longer to reject than did those based on words with sparse semantic neighborhoods. In the second experiment, we found the magnitude of the semantic neighborhood effect for words to be a function of nonword foil type. Taken together, these results indicate that semantic neighborhood size affects processing of both words and pseudohomophones, and that the effect of semantic neighborhood size for words is more pronounced when pseudohomophone foils are employed. These effects are discussed in terms of a model in which the orthographic, phonological, and semantic systems are fully interactive.

Humans↗

PubMed2002

Enriching the structure of the UMLS semantic network.

The Unified Medical Language System's (UMLS's) Semantic Network (SN)---consisting of a network of semantic types---has a two-tree structure, where each semantic type has at most one parent semantic type. This arrangement is restrictive because some semantic types are, by their definition, specializations of several parents. As a proposed enhancement to the SN, its semantic types have previously been partitioned into groups, each of which contains semantic types of some specific area. However, some groups of this proposed partition contain forest (i.e., multiple-tree) structures or even isolated semantic types. Both situations imply a disconnected internal structure. Connectivity is actually one way to assess the proposed "semantic validity" principle for partitions. It is a desired, although not required, property. In this paper, we introduce a methodology for identifying "missing" IS-A links and adding them to the SN. This process transforms the SN into a Directed Acyclic Graph (DAG) structure, with semantic types permitted to have multiple parents. A result of our methodology is the transformation of the proposed SN partition into groups satisfying the connectivity property.

Semantics↗

PubMed1998

Cognitive brain activity in Alzheimer's disease: electrophysiological response during picture semantic categorization.

Semantic memory deterioration is a major component of the cognitive decline seen in patients with dementia of the Alzheimer's type (DAT); however, the exact nature of this deficit remains unclear. Some research data support a procedural deficit where there is an inability to access or retrieve the contents of semantic memory, while other data point to a degraded semantic store where the actual content of semantic memory is degraded. Additional information about semantic processing in DAT can be obtained through the use of an event-related potential (ERP) component known as N400. In the present study, ERPs were recorded from 10 young control participants, 10 elderly control participants, and 10 DAT patients in a picture-semantic matching task. Stimuli were presented sequentially as prime-target pairs, with one-half of the targets matching the primes via semantic relationships (e.g., piano-violin) and the other half mismatching the prime (e.g., helmet-violin). The task was to discriminate between semantically related and unrelated pairs of pictures. In the young and elderly control groups, ERPs generated a larger N400 for unrelated than related target pictures, with a maximum amplitude around 380 ms in the young group and around 480 ms in the elderly group. The amplitude of the N400 was significantly reduced in the DAT patients. However, a separate analysis of congruent and incongruent ERPs trials revealed significant differences only with the incongruent trials. The amplitude of incongruent recordings was larger for the elderly control group than for the DAT patients, while the amplitude for congruent recordings was similar in both groups. These findings are consistent with the neuropathological evidence that Alzheimer's disease is a neocortical disconnection syndrome in which there is a loss of structural and functional integrity of long corticocortical tracts. The semantic activation created by the context is not used efficiently in processing stimuli, which affects access to specific concepts and gradually leads to a breakdown in the structure and organization of semantic memory.

Adult↗

PubMedDate not supplied

A study of idiom comprehension in children with semantic-pragmatic difficulties. Part II: Between-groups results and discussion.

Using a play-based methodology and a symptom checklist, this study investigated idiom comprehension in 26 children aged between 6-11 who were considered to have semantic-pragmatic difficulties. This group was compared with two groups of mainstream children and a group of children with (other) language disorders not primarily of a semantic or pragmatic nature. The results indicate that the children with semantic-pragmatic difficulties did, as a group, demonstrate significantly fewer appropriate idiomatic interpretations and significantly more inappropriate interpretations than did any of the other three groups. However, the higher level of inappropriate scores in the semantic-pragmatic difficulties group reflected a large number of 'fuzzy' actions rather than significantly higher rates of literality. This may indicate an awareness among these children that the literal meaning is inappropriate in the absence of adequate idiom vocabulary. It may also reflect difficulty in retrieving known idioms from memory and/or in selecting the most appropriate meaning from several possibilities in context. Despite relative weakness, the children with semantic-pragmatic difficulties displayed appropriate interpretations considerably more often than they evidenced inappropriate ones. Within-group analysis reveals that the children diagnosed with Asperger syndrome or high-functioning autism performed less well than did those diagnosed with 'semantic-pragmatic disorder'. Nevertheless, both of these subgroups encompassed a considerable range of comprehension ability with regard to the 12 common idioms tested. Analysis of the play task performance and symptom checklist suggests that this variation probably reflects differences in the critical semantic and pragmatic skills underpinning idiom comprehension. These include flexibility of thought, theory of mind, attention to context, prosody and overall coherence, as well as the ability to integrate world knowledge and current contextual information to guide inferencing. In combination with definition task data and broader knowledge of symptomatology, the play task may be used to identify the sites and sources of idiom comprehension breakdown in individual children. It is probable that idiom comprehension in this group of children with semantic-pragmatic difficulties was facilitated by the inclusion of only concrete idioms and by the visual support provided by the play set. Nevertheless, the moderate to age-appropriate ability displayed by this group in this context suggests that the characterization of children with semantic-pragmatic difficulties as predominantly literal needs to be revised. Rather than seeking a blanket characterization of an essentially heterogeneous group, it may be more useful to consider idiom comprehension a secondary manifestation of semantic and/or pragmatic difficulties. Since the children who exhibit these difficulties vary in symptomatology and, probably, in aetiology, it follows that they will also vary with respect to idiom comprehension and the reasons for its breakdown.

Autistic Disorder↗

PubMed2001

No right to speak? The relationship between object naming and semantic impairment: neuropsychological evidence and a computational model.

The processes required for object naming were addressed in a study of patients with semantic dementia (a selective decline of semantic memory resulting from progressive temporal lobe atrophy) and in a computational model of single-word production. Although all patients with semantic dementia are impaired in both single-word production and comprehension, previous reports had indicated two different patterns: (a) a parallel decline in accuracy of naming and comprehension, with frequent semantic naming errors, suggesting a purely semantic basis for the anomia and (b) a dramatic progressive anomia without commensurate decline in comprehension, which might suggest a mainly postsemantic source of the anomia. Longitudinal data for 16 patients with semantic dementia reflected these two profiles, but with the following additional important specifications: (1) despite a few relatively extreme versions of one or other profile, the full set of cases formed a continuum in the extent of anomia for a given degree of degraded comprehension; (2) the degree of disparity between these two abilities was associated with relative asymmetry in laterality of atrophy: a parallel decline in the two measures characterized patients with greater right- than left-temporal atrophy, while disproportionate anomia occurred with a predominance of atrophy in the left-temporal lobe. In an implemented computational model of naming, semantic representations were distributed across simulated left- and right-temporal regions, but the semantic units on the left were more strongly connected to left-lateralized phonological representations. Asymmetric damage to semantic units reproduced the longitudinal patient profiles of naming relative to comprehension, plus additional characteristics of the patients' naming performance. On the basis of both the neuropsychological and computational evidence, we propose that semantic impairment alone can account for the full range of word production deficits described here.

Anomia↗

PubMed2002

N400 and automatic semantic processing abnormalities in patients with schizophrenia.

BACKGROUND: One factor hypothesized to underlie thinking disturbance in patients with schizophrenia is abnormal or disinhibited automatic spreading activation of semantic networks, which can be assessed using the N400 event-related potential. N400 is a negative-going component elicited at about 400 milliseconds following semantic stimuli that are not primed by the preceding context. Semantic priming refers to facilitated semantic processing gained through preexposure to semantic context, which can happen automatically or strategically. Using N400, inferences can be drawn regarding the extent to which a given context primes a word. METHODS: During a picture-word matching task, N400s to primed (exact match) and unprimed (remotely related) words were recorded from 18 healthy control subjects and 18 patients with schizophrenia performing a picture-word matching task. A short interval (325 milliseconds) between picture and word onset (stimulus-onset asynchrony) was used to optimize the role of automatic spreading semantic activation and to minimize the role of attention, expectancy, preparation, and working memory. RESULTS: Despite behavioral evidence of normal semantic priming, patients generated an abnormally small N400 (ie, less negative) to unprimed words. The N400 to primed words was neither larger nor smaller in patients than in controls, suggesting normal use of context. CONCLUSIONS: A reduced N400 to unprimed words in patients with schizophrenia suggests that there was inappropriate priming of words by remotely related semantic contexts. This is consistent with an overly broad automatic spread of activation through semantic networks in patients with schizophrenia.

Adult↗

PubMed2002

Functional anatomy of syntactic and semantic processing in language comprehension.

A functional magnetic resonance imaging (fMRI) study was conducted to map syntactic and semantic processes onto the brain. Chinese-English bilingual subjects performed two experimental tasks: a syntactic plausibility judgment task in which they decided whether a viewed verb phrase was syntactically legal, and a semantic plausibility judgment task in which they decided whether a viewed phrase was semantically acceptable. A font size judgment task was used as baseline. It is found that a large-scale distributed neural network covering the left mid-inferior frontal and mid-superior temporal cortices was responsible for the processing of Chinese phrases. The right homologue areas of these left cortical sites were also active, although the brain activity was obviously left-lateralized. Unlike previous research with monolingual English speakers that showed that distinct brain regions mediate syntactic and semantic processing of English, the cortical sites contributing to syntactic analysis of Chinese phrases coincided with the cortical sites relevant to semantic analysis. Stronger brain activity, however, was seen in the left middle frontal cortex for syntactic processing (relative to semantic processing), whereas for semantic processing stronger cortical activations were shown in the left inferior prefrontal cortex and the left mid-superior temporal gyri. The overall pattern of results indicates that syntactic processing is less independent in reading Chinese. This is attributable to the linguistic nature of the Chinese language that semantics and syntax are not always clearly demarcated. Equally interesting, we discovered that when our bilingual subjects performed syntactic and semantic acceptability judgments of English phrases, they applied the cerebral systems underlying Chinese reading to the processing of English.

Adult↗

PubMed2006

Auditory semantic networks for words and natural sounds.

Does lexical processing rely on a specialized semantic network in the brain, or does it draw on more general semantic resources? The primary goal of this study was to compare behavioral and electrophysiological responses evoked during the processing of words, environmental sounds, and non-meaningful sounds in semantically matching or mismatching visual contexts. A secondary goal was to characterize the dynamic relationship between the behavioral and neural activities related to semantic integration using a novel analysis technique, ERP imaging. In matching trials, meaningful-sound ERPs were characterized by an extended positivity (200-600 ms) that in mismatching trials partly overlapped with centro-parietal N400 and frontal N600 negativities. The mismatch word-N400 peaked later than the environmental sound-N400 and was only slightly more posterior in scalp distribution. Single-trial ERP imaging revealed that for meaningful stimuli, the match-positivity consisted of a sensory P2 (200 ms), a semantic positivity (PS, 300 ms), and a parietal response-related positivity (PR, 500-800 ms). The magnitudes (but not the timing) of the N400 and PS activities correlated with subjects' reaction times, whereas both the latency and magnitude of the PR was correlated with subjects' reaction times. These results suggest that largely overlapping neural networks process verbal and non-verbal semantic information. In addition, it appears that semantic integration operates across different time scales: earlier processes (indexed by the PS and N400) utilize the established meaningful, but not necessarily lexical, semantic representations, whereas later processes (indexed by the PR and N600) are involved in the explicit interpretation of stimulus semantics and possibly of the required response.

Acoustic Stimulation↗

PubMed2006

Category-specific effects in semantic memory: category-task interactions suggested by fMRI.

Much work has investigated the neural representation of specific categories of knowledge, but relatively scant attention has been paid in the cognitive neuroscience literature to the semantic processes that contribute to semantic memory. In this study, we monitored regional cortical activity with fMRI while healthy young adults evaluated visually displayed NATURAL KIND, ARTIFACT, and ABSTRACT nouns with two standard tasks: Typicality judgments and Pleasantness judgments. We observed a significant interaction effect between the category of knowledge and the type of judgment used to evaluate members of these semantic categories. Typicality judgments recruited greater temporal-occipital activation relative to Pleasantness judgments of the same category, and this was seen for comparisons of all three semantic categories. However, when contrasted with Typicality judgments, Pleasantness judgments activated a different anatomic distribution for each semantic category. These findings are consistent with a dynamic approach to semantic memory that includes at least two components: semantic knowledge and semantic processes that interpret this knowledge in several ways depending on the particular semantic challenge.

Adult↗

PubMed2006

Selective preservation of memory for people in the context of semantic memory disorder: patterns of association and dissociation.

A number of single cases in the literature demonstrate that person-specific semantic knowledge can be selectively impaired after acquired brain damage compared with that of object categories. However, there has been little unequivocal evidence for the reverse dissociation, selective preservation of person-specific semantic knowledge. Recently, three case studies have been published which provide support for the claim that such knowledge can be selectively preserved [Kay, J., & Hanley, J. R. (2002). Preservation of memory for people in semantic memory disorder: Further category-specific semantic dissociation. Cognitive Neuropsychology, 19, 113-134; Lyons, F., Hanley, J. R., & Kay, J. (2002). Anomia for common names and geographical names with preserved retrieval of names of people: A semantic memory disorder. Cortex, 38, 23-35; Thompson, S. A, Graham, K. S., Williams, G., Patterson, K., Kapur, N., & Hodges, J. R. (2004). Dissociating person-specific from general semantic knowledge: Roles of the left and right temporal lobes. Neuropsychologia, 42, 359-370]. In this paper, we supply further evidence from a series of 18 patients with acquired language disorder. Of this set, a number were observed to be impaired on tests of semantic association and word-picture matching using names of object categories (e.g. objects, animals and foods), but preserved on similar tests using names of famous people. Careful methodology was applied to match object and person-specific categories for item difficulty. The study also examined whether preservation of person-specific semantic knowledge was associated with preservation of knowledge of 'biological categories' such as fruit and vegetables and animals, or with preservation of 'token' knowledge of singular categories such as countries. The findings are discussed in the context of a variety of accounts that examine whether semantic memory has a categorical structure.

Adult↗

PubMed2006

Refractory effects in stroke aphasia: a consequence of poor semantic control.

This study examined the full range of effects associated with "semantic access impairment" - namely, refractory variables (semantic relatedness, speed of presentation and item repetition), inconsistency, the absence of frequency effects and facilitation by cues - in a series of stroke patients with multimodal semantically impairment. By investigating all of these factors in a group of patients who were not specifically selected to show "access" effects, we were able to establish (1) whether this pattern is a common consequence of infarcts that produce semantic impairment and (2) if these symptoms co-occur. All of the patients showed effects of cueing and an absence of frequency effects in comprehension. Patients whose brain damage included the left inferior prefrontal cortex (LIPC) also showed marked effects of refractory variables; in contrast, two patients with temporal-parietal but not frontal lesions were less sensitive to these variables. Parallel results were obtained for cyclical naming and word-picture matching tasks suggesting that the LIPC plays a role in semantic selection as well as lexical retrieval. Rapid presentation and item repetition is likely to have increased the selection demands in both of these tasks in a similar fashion. Unlike patients with classical "semantic access impairment", our semantically impaired stroke patients showed significant test-retest consistency, indicating that their difficulties did not result from an unpredictable failure of semantic access--instead, their deficits were interpreted as arising from failures of semantic control.

Adult↗

PubMed1998

Cortical networks implicated in semantic and episodic memory: common or unique?

While previous functional neuroimaging studies have shown that semantic and episodic memory tasks activate different cortical regions, they never compared regional cerebral blood flow (rCBF) patterns associated with semantic and episodic memory within the same experimental design. In this study, we used H2(15)O PET to study subjects in the course of semantic and episodic memory tasks. rCBF was measured in 9 normal volunteers during a resting baseline condition and two cognitive tasks. In the semantic categorisation task subjects heard a list of concrete words and had to respond to words belonging to the "animals" or "food" category. In the episodic recognition task subjects heard a list of concrete words, half "old", i.e. belonging to the list of the semantic categorisation task, and half "new", i.e. presented for the first time. Subjects had to respond to the "old" words. Both tasks were compared to a resting condition. Statistical analysis was performed with Statistical Parametric Mapping (SPM). Compared to the resting condition, the semantic tasks, activated the superior temporal gyri bilaterally, the left frontal cortex, and right premotor cortex. The episodic tasks activated the left superior temporal gyrus, the frontal cortex bilaterally, and the right inferior parietal cortex. Compared to the episodic memory tasks, the semantic memory tasks activated the superior temporal/insular cortex bilaterally and the right premotor cortex. Compared to the semantic memory tasks, the episodic memory tasks activated the right frontal cortex. These results suggest that cortical networks implicated in semantic and episodic memory show both common and unique regions, with the right prefrontal cortex being the neural correlate specific of episodic remembering.

Adult↗

PubMed2001

Semantic structure in schizophrenia as assessed by the category fluency test: effect of verbal intelligence and age of onset.

It has been reported that long-term memory function, including the semantic structure of category, is impaired in patients with schizophrenia. The present study was performed to determine: (1) whether the deficit in semantic structure in schizophrenia is independent of cultural backgrounds, and (2) the effect of age of onset and verbal intelligence on the degradation of semantic structure in these patients. Fifty-seven Japanese patients with schizophrenia and 33 normal control subjects entered the study. The semantic structure was derived by Multidimensional Scaling (MDS) analysis based on data from the ANIMAL category fluency test. The semantic structure was compared between: (1) schizophrenic patients as a whole vs. normal control subjects; (2) earlier onset (age of onset <20 years) vs. later-onset groups of patients; and (3) high Vocabulary score (score of the Vocabulary subtest from the WAIS-R>7) vs. low Vocabulary score patient groups. Normal control subjects demonstrated the domestic/size dimension in semantic structure, while no such dimension was obtained in patients with schizophrenia. The subgroup comparisons revealed that the later onset or the high Vocabulary score group maintained a relatively intact semantic structure compared with the earlier onset or the low Vocabulary score group, respectively. These findings suggest that the deficit in semantic structure in patients with schizophrenia is commonly observed irrespective of cultural backgrounds, and that age of onset and the level of verbal intelligence are closely related to severity of degradation of the semantic structure in schizophrenia.

Adult↗

PubMed2003

Semantic versus phonological false recognition in aging and Alzheimer's disease.

Patients with Alzheimer's disease (AD) have been found to exhibit lower levels of false recognition of semantic associates compared with healthy older adults. Because these patients may show impaired performance of episodic and semantic memory tasks, this finding could be explained by deficits in episodic memory, semantic memory, or both. The authors adapted a paradigm for comparison of semantic versus phonological false recognition. They found that: (a) patients with AD exhibited lower levels of corrected false recognition of semantic, phonological, and hybrid (mixed semantic and phonological) lists than older adults, and (b) patients with AD showed very similar levels of false recognition for all list types. These results suggest that only episodic memory deficits are necessary to explain the lower level of false recognition of semantic associates observed in patients with AD when compared to older adults. Additionally, (c) older adults showed greater levels of semantic, phonological, and hybrid false recognition than younger adults, extending previous false recognition research of semantically related words and categorized colored photographs to phonologically related words.

Aged↗

PubMed2002

An investigation of the integrity of semantic boundaries in schizophrenia.

Organizing information and knowledge, and hence categorization, requires specifying boundaries between items, concepts and words. Over-inclusiveness in categorization may be seen as looseness of association; over-inclusive thinking was an early description of schizophrenic thinking. Recent studies suggest semantic memory problems in schizophrenia, and that thought disorder is associated with a disorganized semantic network. One such study [Psychol. Med. 24 (1994) 193], using a word categorization task, found patients slowest to respond to items semantically related to, but outside the category, whereas controls were slower responding to items sharing less features of the category (i.e. borderline). The authors suggested that there is an outward shift of semantic category boundaries in schizophrenia. In Experiment 1, we replicated methods, but did not find this qualitative difference in patients (28 patients, 26 controls). We extended this question in Experiment 2 to a more visual domain using pictures that 'morphed' from one entity into another and asked participants to decide when they no longer considered an item to be that item (20 patients, 25 controls). We did not find a difference between patients and controls in their sensitivity to detect boundaries of representations. These two experiments do not support the notion that thought disorder with postulated looseness of association or over-inclusive thinking is related to reduced awareness of boundaries of semantic category membership or entities, and inferentially their featural network. Despite anomalies in the semantic system in schizophrenia, we found aspects to be intact. This specificity of semantic processing is promising, suggesting that research will be informative as to how semantic memory is constructed, and thus how it can selectively break down. Moreover, this study indicates that patients do not 'fail' semantic tasks (e.g. priming) because of globally disorganized decision-making: here their capability to make precise distinctions between representations was intact.

Adult↗