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PubMed2005

Executive inhibition and semantic association in schizophrenia.

Research indicates that some patients with schizophrenia display aberrant inhibition of semantic memory, which may underpin formal thought disorder (FTD). We administered a novel Stroop-like paradigm to three groups of participants: 15 schizophrenic patients with formal thought disorder (FTD), 16 with low FTD ratings, and 15 healthy matched controls. They were required to inhibit a prepotent response for a (previously instructed) required response. Four conditions examined the effect of executive demands by manipulating the relatedness between prepotent and required responses (i.e., identical, semantically related, or unrelated). Two further conditions examining executive function working memory demands required the naming of real or abstract pictures that did and did not necessitate inhibition, respectively. Patients with and without FTD experienced increased difficulty when executive function working memory was required. Moreover, those with FTD also showed increased executive inhibition, but the pattern of errors suggested that the result of this was an automatic activation of semantically related representations. The findings support the notion that increased inhibition underpins the disorganised access to semantic memory in patients with FTD.

Association↗

PubMed2005

An investigation of semantic priming in schizophrenia using a new priming paradigm.

In the present study, twenty schizophrenic patients and twenty healthy controls were tested in a new priming paradigm that allows a clear distinction to be made between automatic, perceptual priming effects and effects related to decision bias. Participants had to identify briefly presented masked target words preceded by clearly visible primes that were semantically related to the target or not. Target presentation duration corresponded to a pre-determined perceptual threshold for each participant, and a two-alternative forced-choice methodology was used. Equivalent amounts of semantic priming were found in schizophrenic patients compared with healthy controls. However, for the schizophrenic patients, a positive correlation was found between the size of automatic perceptual priming effects and formal thought disorders, as measured by Andreasen's Thought, Language and Communication (TLC) scale. The new paradigm tested in the present study overcomes some of the limitations of prior research on semantic priming in schizophrenia, and provides further evidence suggesting that an increased spreading of activation in the semantic network could partly underlie formal thought disorders in schizophrenia.

Cognition Disorders↗

PubMed2002

False memories and lexical decision: even twelve primes do not cause long-term semantic priming.

Semantic priming effects are usually obtained only if the prime is presented shortly before the target stimulus. Recent evidence obtained with the so-called false memory paradigm suggests, however, that in both explicit and implicit memory tasks semantic relations between words can result in long-lasting effects when multiple 'primes' are presented. The aim of the present study was to investigate whether these effects would generalize to lexical decision. In four experiments we showed that even as many as 12 primes do not cause long-term semantic priming. In all experiments, however, a repetition priming effect was obtained. The present results are consistent with a number of other results showing that semantic information plays a minimal role in long-term priming in visual word recognition.

Cues↗

PubMed1997

Adding new word associations to semantic memory: evidence for two interactive learning components.

The addition of newly learned word associations to semantic memory was investigated in three experiments. In these experiments word pairs were repeatedly presented as prime-target pairs in a lexical decision task. Performance on repeated pairs (both pre-experimentally associated and initially unrelated pairs) was compared to that on neutral pairs. In Experiments 1 and 2, effects of prior study (episodic priming) were observed but since this episodic priming effect was equal for both conditions it could not be concluded that the new associations has been added to semantic memory. In Experiment 3 some evidence was found that the newly learned word associations had been added to semantic memory. This occurred only after presenting the word pairs for several trials in paired-associate learning. The results are interpreted as supporting a model that distinguishes two memory components that mediate the effects of new learning, an episodic and a semantic one.

Adult↗

PubMed1999

Object identification is isolated from scene semantic constraint: evidence from object type and token discrimination.

Two models of the interaction between scene meaning and object identification were tested: the description enhancement model and the criterion modulation model. The former proposes that the early activation of a scene schema facilitates the initial perceptual analysis of schema-consistent objects, the latter that schema activation modulates the amount of information necessary to indicate the presence of an object of a particular perceptual type. In Experiment 1, we employed a forced-choice, type-discrimination paradigm. Participants were asked to determine which of two semantically consistent objects or which of two semantically inconsistent objects had appeared in a briefly presented scene. Contrary to the prediction derived from both of these models, discrimination performance was better for semantically inconsistent versus consistent objects. In Experiments 2 and 3 we introduced a forced-choice, token-discrimination paradigm to further test the description enhancement model. Contrary to the prediction of that model, discrimination performance was no better for semantically consistent versus inconsistent tokens. These results suggest that both the initial perceptual analysis of an object and the matching of an object's constructed visual description to stored descriptions are isolated from stored knowledge about real-world contingencies between scenes and objects.

Adult↗

PubMed2004

Out of one's mind: a study of involuntary semantic memories.

The study of memories that pop into one's mind without any conscious attempt to retrieve them began only recently. While there are some studies on involuntary autobiographical memories (e.g., ) research on involuntary semantic memories or mind-popping is virtually non-existent. The latter is defined as an involuntary conscious occurrence of brief items of one's network of semantic knowledge. The recall of these items (e.g., a word, a name, a tune) is not accompanied by additional contextual information and/or involvement of self-a standard feature of involuntary autobiographical memories. The paper reports several diary and questionnaire studies which looked into the nature and frequency of occurrence of these memories. The data show that people do experience involuntary semantic memories which tend to occur without any apparent cues while being engaged in relatively automatic activities. Possible mechanisms of involuntary semantic memories are discussed (e.g., very long-term priming), and the results of the study provide information on the possible duration of the priming effects in everyday life. Related theoretical and methodological issues and future avenues of research in this neglected area are outlined.

Adult↗

PubMed2006

Now you see it, now you don't: on turning semantic interference into facilitation in a Stroop-like task.

We use a masked priming procedure to test two accounts of the picture-word interference (PWI) effect: the lexical selection by competition account (Levelt et al., 1999; Roelofs, 1992) and the response selection account (Lupker, 1979; Miozzo and Caramazza, 2003). In the visible (standard) condition, we replicated the often-observed semantic interference effect. In the masked condition, we observed semantic facilitation. We take the polarity shift as a function of masking to mean that the semantic interference and semantic facilitation in the PWI task should be attributed to two qualitatively different processes. We argue that this conclusion follows naturally from the response selection account, but only with great difficulty from the lexical selection by competition account.

Adolescent↗

PubMed1998

The more you know the less you can tell: inhibitory effects of visuo-semantic activation on modality specific visual misnaming.

WH, a 77-years old right-handed psychoanalyst, displayed modality specific visual misnaming as a sequel of an embolic stroke in the left posterior cerebral artery. WH's errors in visual object naming consisted mainly of semantic paraphasias and perseverations. His verbalizations during testing sometimes manifested a conflict between correct responses and perseverations. Analysis of the stream of information from visual perception via semantics to phonology suggested incomplete access from vision to semantics as the source of errors. The disconnection did not affect verbo-visual matching, though he was unable to reject names that did not correspond to visual stimuli. Action naming was relatively spared, but naming of pictures of actions with objects was worse than naming of pictures of intransitive actions. Tactile naming worsened with simultaneous vision of objects. In visual object naming the error rate increased with increasing familiarity of objects. We propose that an interaction of excitation and inhibition within a single semantic system can explain the clinical phenomena of modality specific visual misnaming.

Aged↗

PubMed1991

The effect of contextual constraint on semantic judgments by Alzheimer patients.

Subjects (Alzheimer patients, normal young and elderly individuals) heard a sentence the last word of which was missing. A visual word then appeared and the subjects decided whether it made a sensible ending to the sentence. Sentences varied in the degree to which their semantic context constrained possible endings to the sentence. The degree of contextual constraint greatly influenced response time--the greater the constraint, the faster subjects made their decisions. While Alzheimer patients were slower than normals, their decision time was affected by contextual constraint to the same degree as that of normals. Thus, the performance of Alzheimer patients was sensitive to the amount of semantic context present in sentences, and this context facilitated their ability to make conscious semantic judgements. These findings suggest that Alzheimer patients are capable of using semantic information in a task requiring attention-dependent processes.

Adult↗

PubMed1977

Pragmatic-semantic and syntactic factors influencing ear differences in dichotic listening.

In a three-factorial experiment sequences of 3 words were presented dichotically. The sequences consisted of two uninflected nouns denoting a person or a group of persons and 1 verb denoting an interaction. The three factors were Ear, Syntactic Structuredness vs. Unstructuredness and Semantic-Pragmatic Structuredness vs. Unstructuredness. The sequences in the syntactic unstructuredness condition are spoken in staccato form without sentence intonation and the order of the 2 nouns and the verb was at random; in the syntactic structuredness condition the sequences were spoken fluently and with sentence intonation and the order was always N-V-N. Semantic-pragmatic structuredness of the sequences means that one of the two potential actor-object-relations between the two nouns of a sequence was more probable than the other. The results show that it is only the left hemisphere that is responsive to syntactic structuredness, while the two hemispheres seems to be equally responsive to semantic-pragmatic structuredness. But it is possible that the two hemispheres differ in the manner in which they make use of semantic structures: the left hemisphere in a selective manner, appropriate for the solution of a specific task, and the right hemisphere in a more diffuse and global manner.

Adolescent↗

PubMed1984

Experimentally induced semantic paralexias in normals: a property of the right hemisphere.

The recently proposed association between semantic paralexias and right hemispheric reading processes was investigated in normals with a tachistoscopic half-field reading experiment. With extremely brief lateralized exposure of nouns, permitting only 25% of correct reading, semantic paralexias were induced. These semantic substitutions occurred three times more often to LVF (right hemisphere) than to RVF (left hemisphere) presentations, whereas other errors were observed with similar frequency to both visual fields. We concluded that semantic paralexias, as they are observed in patients, occur in normals induced by reduced reading time and are the product of right hemispheric reading processes.

Adult↗

PubMed1996

Semantic processing without conscious understanding in a global aphasic: evidence from auditory event-related brain potentials.

We report a global aphasic who showed evidence of implicit semantic processing of spoken words. Auditory event-related brain potentials (ERPs) to semantically congruous and incongruous final words in spoken sentences were recorded. 17 elderly adults served as control subjects. Their ERPs were more negative to incongruous than to congruous final words between 300 and 800 ms after stimulus onset (N400), and more positive between 800 and 1500 ms (Late Positivity). The aphasic showed an exactly similar pattern of ERP components as the controls did, but his performance in a task demanding explicit differentiation between semantically congruous and incongruous sentences was at the chance level. During follow-up, his explicit understanding recovered over the chance level but the ERPs remained fairly similar. We conclude that implicit semantic activation at the conceptual level can take place even in the absence of conscious (explicit) comprehension of the meaningfulness of linguistic stimuli.

Acoustic Stimulation↗

PubMed2002

Differential involvement of the hippocampus and temporal lobe cortices in rapid and slow learning of new semantic information.

The present study examined the rapid and slow acquisition of new semantic information by two patients with differing brain pathology. A partial double dissociation was found between the patterns of new learning shown by these two patients. Rapid acquisition was impaired in a patient (YR) who had relatively selective hippocampal damage, but it was unimpaired in another patient (JL) who, according to structural MRI, had an intact hippocampus but damage to anterolateral temporal cortex accompanied by epileptic seizures. Slow acquisition was impaired in both patients, but was impaired to a much greater extent in JL. The dissociation suggests that the mechanisms underlying rapid and slow acquisition of new semantic information are at least partially separable. The findings indicate that rapid acquisition of semantic, as well as episodic information, is critically dependent on the hippocampus. However, they suggest that hippocampal processing is less important for the gradual acquisition of semantic information through repeated exposure, although it is probably necessary for normal levels of such learning to be achieved.

Adult↗

PubMed2003

A procedure for identifying regions preferentially activated by attention to semantic and phonological relations using functional magnetic resonance imaging.

A procedure is introduced for using functional magnetic resonance imaging (fMRI) techniques to identify neural regions associated with attention to semantic and phonological aspects of written words within a single group of subjects. Short lists (16 words/list), consisting of visually-presented semantically-related words (bed, rest) or rhyming words (weep, beep) were presented rapidly to subjects, who were asked to attend to the relations among the words. Regions preferentially involved in attention to semantic relations appeared within left anterior/ventral inferior frontal gyrus (IFG, approximate Brodmann Area, BA47), left posterior/dorsal IFG (BA44/45), left superior/middle temporal cortex (BA22/21), left fusiform gyrus (BA37), and right cerebellum. Regions preferentially involved in attention to phonological relations appeared within left inferior frontal cortex (near BA6/44, posterior to the semantic regions within IFG described above) and within bilateral inferior parietal cortex (BA40) and precuneus (BA7). This method is notable in that a comparison of the two tasks within some of the individual subjects revealed activation patterns similar to the group average, especially within left inferior frontal and left superior/middle parietal cortices. This fact combined with the efficiency with which the data can be obtained (here, in about an hour of functional scanning) and the adaptability of the task for many different subject populations suggests a wide range of possibilities for this technique: it could be used to track language development (e.g. in children), compare language organization across subject populations (e.g. for dyslexic or blind subjects), and identify language regions within individuals (e.g. potentially to aid in surgical planning).

Adolescent↗

PubMed1997

The deterioration of semantic networks in patients with Alzheimer's disease: a cross-sectional study.

Previous studies showed that the semantic networks of Alzheimer's disease (AD) patients are disrupted in the early stages of the disease. The present study examined the semantic networks of 33 AD patients in different stages of disease severity to compare the quantitative and qualitative changes in their networks as the disease progresses. The properties of the semantic networks (e.g. the dimensionality and strength of the connections) were examined with multidimensional scaling and Pathfinder analyses. The results showed that, as AD patients became more demented, they focused less on abstract attributes in categorizing concepts, and have an alteration in the relative strength of associations between concepts. These findings indicate that the structure of semantic knowledge deteriorates in a systematic manner throughout the course of AD.

Aged↗

PubMed2006

Emotional connotation of words: role of emotion in distributed semantic systems.

One current doctrine regarding lexical-semantic functions asserts separate input and output lexicons with access to a central semantic core. In other words, processes related to word form have separate representations for input (comprehension) vs. output (expression), while processes related to meaning are not split along the input-output dimension. Recent evidence from our laboratory suggests that semantic processes related to emotional connotation may be an exception to this rule. The ability to distinguish among different emotional connotations may be linked distinctly both to attention systems that select specific sensory input for further processing and to intention systems that select specific actions for output. In particular, the neuroanatomic substrates for emotional connotation on the input side of the equation appear to differ from the substrates on the output side of the equation. Implications for semantic processing of emotional connotation and its relationship to attention and motivation systems are discussed.

Attention↗

PubMed2003

Differences in the perception and time course of syntactic and semantic violations.

A reading time and an ERP experiment conducted in Italian investigated the parser's responses to a syntactic violation (subject-verb number agreement) and to a semantic violation (subject-verb selectional restriction), examining the time course of comprehension processes until sentence end. The reading-time data showed that the syntactic violation was detected earlier than the semantic one and that the two violations differed in the time-course. The ERP data fully supported the reading time data: Syntactic anomalies elicited a left anterior negativity (LAN) and a P600. Semantic anomalies elicited a N400 centred on the parietal sites which started 90 ms later (latency 430 ms) than the LAN. Furthermore, the N400 evoked by the words that followed the target word continued and increased until sentence end. The results are discussed with respect to the hypotheses that the parser constructs distinct syntactic and semantic analyses of a sentence and that this characteristic holds cross-linguistically. The appropriateness of different methodologies to the study of sentence processing is also evaluated.

Adolescent↗

PubMedDate not supplied

What do graded effects of semantic transparency reveal about morphological processing?

We examined the influence of semantic transparency on morphological facilitation in English in three lexical decision experiments. Decision latencies to visual targets (e.g., CASUALNESS) were faster after semantically transparent (e.g., CASUALLY) than semantically opaque (e.g., CASUALTY) primes whether primes were auditory and presented immediately before onset of the target (Experiment 1a) or visual with an stimulus onset asynchrony (SOA) of 250 ms (Experiment 1b). Latencies did not differ at an SOA of 48 ms (Experiment 2) or with a forward mask at an SOA of 83 ms (Experiment 3). Generally, effects of semantic transparency among morphological relatives were evident at long but not at short SOAs with visual targets, regardless of prime modality. Moreover, the difference in facilitation after opaque and transparent primes was graded and increased with family size of the base morpheme.

Decision Making↗