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PubMed1998

Morpho-semantic parsing of medical expressions.

The task of editing, indexing, storing, and retrieving medical expressions within medical records remains the main objective for the years to come. Therefore, the need for a parser with semantic capabilities able to robustly extract an essential part of the knowledge embedded in the medical record is paramount. The minimal requirements before considering clinical trials are that such a system has to be in position to handle any source of medical information and to conveniently grasp the main key concepts with low silence, good recognition of modalities and acceptable noise. This paper shows that the potential of morpho-semantic parsing is high to meet these conditions. This technique is an important complement to the traditional lexical approach and to expression-oriented systems like controlled vocabularies.

Language↗
PubMed2004

Passive perception of odors and semantic circuits.

The sense of smell has been traditionally assumed to be different from other sensory modalities in that odors are encoded perceptually, without a semantic component. Recent findings of improved odor memory upon encoding with verbal cues question this view. Furthermore, familiar odors are easier to remember and discriminate than are unfamiliar ones, and odor familiarity is reported to predict odor naming. To investigate whether familiar odors are processed by different cerebral structures than those that process unfamiliar odors, (15)O H(2)O-positron emission tomography (PET) measurements of cerebral blood flow were carried out in 14 healthy men. The task was passive, birhinal, smelling of familiar odors (FAM), unfamiliar odors (uFAM), and odorless air (AIR). Significant activations (P < 0.05) were calculated using the contrasts FAM-AIR, uFAM-AIR, and FAM-uFAM, and deactivations running these contrasts in the opposite direction. In relation to AIR, both FAM and uFAM activated amygdala, piriform cortex, and parts of anterior cingulate cortex. FAM activated, in addition, left frontal cortex (Brodmann's areas 44,45,47), left parietal cortex incorporating precuneus, and right parahippocampus. Clusters covering parahippocampus and precuneus were observed also in FAM-uFAM. The activation of left frontal cortex and right parahippocampus was positively correlated with familiarity ratings. Smelling of familiar but not unfamiliar odorants seems to engage cerebral circuits mediating memory and language functions, in addition to the engagement of olfactory cortex. Already the most elemental form of odor processing, passive perception thus seems to engage semantic circuits. This is achieved by the ability of odorants to immediately elicit associations and judgments of odor characteristics.

Adult↗
PubMed2005

Theta rhythm of navigation: link between path integration and landmark navigation, episodic and semantic memory.

Five key topics have been reverberating in hippocampal-entorhinal cortex (EC) research over the past five decades: episodic and semantic memory, path integration ("dead reckoning") and landmark ("map") navigation, and theta oscillation. We suggest that the systematic relations between single cell discharge and the activity of neuronal ensembles reflected in local field theta oscillations provide a useful insight into the relationship among these terms. In rats trained to run in direction-guided (1-dimensional) tasks, hippocampal cell assemblies discharge sequentially, with different assemblies active on opposite runs, i.e., place cells are unidirectional. Such tasks do not require map representation and are formally identical with learning sequentially occurring items in an episode. Hebbian plasticity, acting within the temporal window of the theta cycle, converts the travel distances into synaptic strengths between the sequentially activated and unidirectionally connected assemblies. In contrast, place representations by hippocampal neurons in 2-dimensional environments are typically omnidirectional, characteristic of a map. Generation of a map requires exploration, essentially a dead reckoning behavior. We suggest that omnidirectional navigation through the same places (junctions) during exploration gives rise to omnidirectional place cells and, consequently, maps free of temporal context. Analogously, multiple crossings of common junction(s) of episodes convert the common junction(s) into context-free or semantic memory. Theta oscillation can hence be conceived as the navigation rhythm through both physical and mnemonic space, facilitating the formation of maps and episodic/semantic memories.

Animals↗
PubMed1996

Language and Operations in Children's Class Inclusion Reasoning: The Operational Semantic Theory of Reasoning

In this article we critique two prominent theories of reasoning-mental logic and mental models-and argue that reasoning does not consist of either applying logical rules or constructing mental models. Instead, we propose an operational semantic theory of reasoning, according to which reasoning is based on children's operational understanding of key terms in a given problem. We then go on to consider an important recent developmental theory of reasoning, fuzzy-trace theory. In order to illustrate the view of reasoning proposed here we report a study of class inclusion. Dramatic differences in class inclusion performance were found as the result of linguistic context; performance was significantly higher when an explicit request for a subclass comparison preceded the class inclusion question as compared to a standard condition when the class inclusion question alone was asked. This was the case, however, only when the prior subclass comparison question referred to the same dimensions as the class inclusion question and not when irrelevant subclasses were referred to. Children's performance was also better when they sorted the materials into the supraordinate class as compared to the subclasses, but not when the experimenter sorted them for the child. These effects due to the operational and linguistic manipulations are discussed in terms of a general operational semantic theory of reasoning.

Journal Article↗
PubMed2000

Is 7300 m Equal to 7.3 km? Same Semantics but Different Anchoring Effects.

Anchoring effect (AE) refers to a phenomenon that an arbitrary number (i.e., the anchor) biases a subsequent numerical judgment. Three experiments were conducted to examine how the anchor is represented in short-term memory. Experiment 1 showed that despite the semantic equivalence of two anchors, the anchor with a larger absolute value (i.e., 7300 m) induced a greater numerical estimate than did the anchor with a smaller absolute value (i.e., 7.3 km). Experiment 2 showed that an anchor 228 could serve as both a high and a low anchor, depending on the absolute value to be judged in the numerical judgment. By including anchors with negative signs, Experiment 3 further demonstrated that it was the absolute value but not the semantics of the anchors that exerted an effect on the subsequent numerical estimate. The three experiments provided converging support for the hypothesis that an anchor is superficially represented as absolute value plus affix in short-term memory. The processes leading to AE and the practical implications are discussed. Copyright 2000 Academic Press.

Journal Article↗
PubMed1996

Increased regional cerebral glucose metabolism and semantic memory performance in Alzheimer's disease: a pilot double blind transdermal nicotine positron emission tomography study.

Nicotinic receptor dysfunction and impaired semantic memory occur early in Alzheimer's disease patients (AD). Previous research implied that nicotine's ability to enhance alertness, arousal, and cognition in a number of nonclinical populations was a function of its ability to stimulate CNS nicotinic cholinergic receptors. In this study it was hypothesized that transdermal administration of nicotine would increase both regional cerebral glucose metabolism (rCMRglc) and semantic memory (as assessed by verbal fluency). Two mild AD and two elderly controls underwent positron emission tomography scanning during a double blind nicotinic agonist verbal fluency challenge procedure. rCMRglc increases occurred in both AD patients, but not controls. In the two AD patients, verbal fluency scores increased by an average of 17%. One elderly control's verbal fluency increased, and the other decreased. These findings suggest that nicotine's effect on metabolism and verbal fluency is due to its ability to stimulate the cholinergic system.

Alzheimer Disease↗
PubMed1998

Functional brain imaging of episodic and semantic memory with positron emission tomography.

Human memory is composed of several independent but interacting systems. These include a system for remembering general knowledge, semantic memory, and a system for recollection of personal events, episodic memory. The results of positron emission tomography (PET) studies of regional cerebral blood flow indicate that networks of distributed brain regions subserve episodic and semantic memory. Some networks seem to be generally engaged in memory processes whereas the involvement of others is specific to factors such as the type of information to be remembered or the level of retrieval success. The PET findings help to understand memory dysfunction (a) by showing that multiple brain regions are involved in different memory processes and (b) by sharpening the interpretation of the functional role of different brain regions.

Brain↗
PubMed2000

Semantic dementia: clinical, radiological and pathological perspectives.

Semantic dementia (SD) is a recently described clinical syndrome characterised by an acquired progressive inability to name or comprehend common concepts, with little or no distortion of the phonological and syntactic aspects of language, and relative sparing of other aspects of cognition, such as episodic memory, nonverbal problem-solving, and perceptual and visuo-spatial skills. The cognitive locus of this syndrome appears to lie in the permanent store of long-term memory representing general world knowledge-semantic memory. The anatomical distribution of atrophy is less well-defined, and the contribution of various imaging modalities is discussed in the context of a body of 45 published and unpublished cases. We conclude that involvement of the left infero-lateral temporal cortex is the critical area in the genesis of SD. SD probably always represents a non-Alzheimer neurodegenerative process; a variety of pathological lesions may be present, and possible causes, together with debates about their correct classification, are discussed.

Dementia↗
PubMed1994

Semantic integration of information in a physician's workstation.

Patient care is an information-intensive activity, yet physicians have few tools to effectively access and manage patient data. We studied physicians' information needs in an outpatient clinic, and developed a prototype physician's workstation (PWS) to address those needs. The PWS provides integrated access to patient information and uses embedded domain knowledge to enhance the presentation of clinical information to the physician. All the applications in the PWS share a common patient context, defined by the state of the internal patient model--semantic integration. Relevant data are presented together and higher-order alerts are generated by combining notable events with relevant data from the patient context. Semantic integration allows us to present and to operate on all patient data in a given patient's context, significantly enhancing the effectiveness with which information is presented to the physician.

Computer Communication Networks↗
PubMed1985

Deep dyslexia and the right-hemisphere hypothesis for semantic paralexia: a reply to Marshall and Patterson.

Studies of deep dyslexia have conferred prominence upon observations of semantic paralexia (e.g. reading "town" as "city"). Landis et al. (Neuropsychologia 21, 359-364, 1983) have reported evidence indicating that such errors arise in the right hemisphere. However, Marshall and Patterson (Neuropsychologia 21, 425-427, 1983) have advanced both empirical and theoretical arguments against this interpretation: the present paper examines these arguments and finds them seriously flawed. It therefore concludes in favour of the right-hemisphere hypothesis for semantic paralexia.

Dominance, Cerebral↗
PubMed1987

Hemispheric asymmetry in memory for pictorial semantics in normal subjects.

Effects of presence versus absence of semantic organization in pictorial scenes were investigated in a memory hemi-field tachistoscopic paradigm in order to assess the hemispheric status of long-term semantic memory (LTSM). Forty normal subjects were asked to remember a series of pictorial scenes which were organized either in common configurations or were unorganized with respect to real-world configurations. Memory for these scenes was measured by hemi-field presentations of detail probes and whole scene probes. The results showed that there were no differences between the two visual fields in accuracy scores. Latency of positive responses showed that memory for the common/organized scenes was better in the left (LVF) than in the right visual field (RVF) and a dissociation between the two types of pictorial organization was present only in the LVF, with the slower latencies for unorganized scenes. The effect of probe-type was also different in the two visual fields: detail and whole scene probes were undifferentiated within the LVF but were differentiated in the RVF, with whole scenes remembered more quickly. The findings are discussed in terms of asymmetries in storage/retrieval of schemata in LTSM.

Female↗
PubMed1996

Electrophysiological insights into the nature of the semantic deficit in Alzheimer's disease.

Event-related brain potential (ERP) and reaction-time measures were used to determine if the specificity of a category prime differentially affects the amount of semantic priming seen in patients with dementia of the Alzheimer type (DAT) compared with normal elderly and young controls. Subjects were primed with an auditory category name followed by the visually presented name of an imageable object and indicated whether the object was a category member; the category was either superordinate to, at, or subordinate to the basic level. All groups showed similar priming effects in response to the category manipulation, as evidenced in both reaction time and the amplitude of the N400 component of the ERP. Overall, DAT subjects showed the smallest ERP priming effects and young controls the largest. The present study did not provide evidence for a strong version of a strictly "bottom-up" breakdown of the semantic networks in subjects with DAT, suggesting a role for factors such as task difficulty and memory search strategies in online categorization tasks of this type.

Adolescent↗
PubMed1994

Differential activation of right and left posterior sylvian regions by semantic and phonological tasks: a positron-emission tomography study in normal human subjects.

A previous study of brain activation in normal subjects during a phonological (Phonemes) task and a lexical semantic (Words) task using positron-emission tomography [3] is complemented by new data after a method for image realignment was applied [17]. The pattern of cerebral blood flow increases associated with Words compared with Phonemes, involved several foci of activation but these were not exclusively distributed in the left hemisphere as it also included the right angular gyrus, suggesting a participation of the right hemisphere in lexical semantic processes. Conversely, by comparison to Words, Phonemes activated left-sided perisylvian regions, involving the inferior part of the left supramarginal gyrus, in accordance with previous results on verbal short-term memory [12].

Adult↗
PubMed2004

The role of context in remembering familar persons: insights from semantic dementia.

Semantic dementia (SD) is a progressive condition characterized by an insidious and gradual breakdown in semantic knowledge. Patients suffering from this condition gradually lose their knowledge of objects and their attributes, concepts, famous persons, and public events. In contrast, these patients maintain a striking preservation of autobiographical memory. The aim of the present study was to examine in a patient suffering from SD the role of context in the ability to recall knowledge of familiar persons. In an experiment, patient J.M. was asked to name and identify familiar persons that appeared on family photographs from recent and remote periods of her life. In the first experimental condition, the pictures represented personally familiar persons present in a specific spatial and temporal context. In a second experimental condition, the pictures showed personally familiar persons who were presented without any specific episodic context. Results indicate that the patient was able to name and identify familiar persons irrespective of the context of presentation (with/without context) and of the time period (recent/remote). No temporal gradient was found using family photographs. Finally, in contrast with familiar persons, J.M. presented a severe anomia for celebrities. Results are discussed in light of recent research in the field.

Anomia↗
PubMed2006

The effect of aging on event-related potentials and behavioral responses: comparison of tonal, phonologic and semantic targets.

OBJECTIVE: To investigate age-related changes in speech perception by measuring event-related potentials (ERPs) elicited by auditory stimuli varying in their linguistic characteristics from pure tones to words. METHODS: ERPs were recorded from 64 subjects in three age groups (young, middle age and elderly) to auditory target stimuli, using an oddball paradigm. Three different tasks and stimuli were used: tonal, phonological and semantic. RESULTS: N100 latency to tonal targets was significantly shorter than to both types of speech targets. P300 latency to tonal targets was significantly shorter than to phonological targets, which in turn was shorter than to semantic targets. P300 amplitude recorded to the speech targets was significantly larger over the left hemisphere than over the right hemisphere in the young subjects. However, the reverse pattern of asymmetry, favoring the right hemisphere was found in the elderly subjects. The pattern of the hemispheric distribution for the middle aged was somewhere in between the young and elderly. CONCLUSIONS: The data indicate possible progressive changes in left-right asymmetry in language processing with aging. SIGNIFICANCE: Findings may indicate an increased use of compensatory mechanisms for speech processing, or alternatively, an increased use of different generators as individuals age.

Acoustic Stimulation↗
PubMed2004

Recovery of semantic word processing in global aphasia: a functional MRI study.

One important issue concerning the recovery of higher cognitive functions-such as word comprehension in aphasia-is to what extent impairments can be compensated for by intact parts of the network of areas normally involved in a closely related function ("redundancy recovery"). In a previous functional MRI investigation, we were able to show that left hemispheric redundancy recovery within a distributed system of related lexical-semantic functions was the most probable basis of recovery of comprehension from transcortical sensory aphasia. The question remained, however, whether redundancy recovery may play a more general role in the recovery of comprehension after large left hemispheric lesions and severe aphasia. We had the possibility, using the same fMRI paradigm, to study seven cases with left middle cerebral artery (MCA) infarction and partial recovery of comprehension > or =6 months after presentation with global aphasia on acute assessment. Lateralization of activation did not differ significantly between patients and controls. The most consistent regions of activation included the left extrasylvian posterior temporal and the right posterior parietal cortex. Recovery of language comprehension was associated predominantly with activations in regions, which were also activated in several normal subjects. We suggest that a redundancy recovery mechanism within multiple representations of closely related functions was more important than take-over of function by previously unrelated areas (vicariation) as the basis of recovery of word comprehension in our patients in spite of extensive left hemispheric damage. We conclude that redundancy within the lexical-semantic system seems to make an important contribution to recovery of comprehension even in severe aphasia.

Acoustic Stimulation↗
PubMed2006

The cognitive neuroscience of remote episodic, semantic and spatial memory.

The processes and mechanisms implicated in retention and retrieval of memories as they age is an enduring problem in cognitive neuroscience. Research from lesion and functional neuroimaging studies on remote episodic, semantic and spatial memory in humans is crucial for evaluating three theories of hippocampal and/or medial temporal lobe-neocortical interaction in memory retention and retrieval: cognitive map theory, standard consolidation theory and multiple trace theory. Each theory makes different predictions regarding first, the severity and extent of retrograde amnesia following lesions to some or all of the structures mentioned; second, the extent of activation of these structures to retrieval of memory across time; and third, the type of memory being retrieved. Each of these theories has strengths and weaknesses, and there are various unresolved issues. We propose a unified account based on multiple trace theory. This theory states that the hippocampus is needed for re-experiencing detailed episodic and spatial memories no matter how old they are, and that it contributes to the formation and assimilation of semantic memories and schematic spatial maps.

Amnesia, Retrograde↗