PubMed Health⌕ Search

Biomedical subjects

M C Silveri

Publications and source records attributed to M C Silveri.

At least 19 recordsLinked to original sources
PubMed1994

Evidence for a possible neuroanatomical basis for lexical processing of nouns and verbs.

Neuropsychological studies have revealed that brain-damaged patients may show impairments of specific word categories. This study reports the performance of three patients with impairments of the categories noun and verb. The first and second patients, with left frontal lobe atrophy, were impaired in naming and comprehension of verbs. The third patient, with striking atrophy of the left temporal lobe, was disproportionately impaired in naming and comprehension of nouns. These findings suggest that anatomically distinct neural systems in the temporal and frontal lobes of the dominant hemisphere might play a critical role in lexical processing of nouns and verbs, respectively.

Aged↗
PubMed1992

Can residual lexical knowledge concern word form rather than word meaning?

We described a patient with a dramatic deficit of both word comprehension and naming but with good preservation of visual pictorial semantics. On word-picture matching, his performances were slightly better than expected based on the observed lexical semantic disorder; in addition, the patient, who maintained good preservation of his underlying phonology, showed a tendency to point to the picture phonologically related to the target. In order to interpret these data, we advanced the hypothesis that the patient, in spite of his virtually complete inability to name, would be able, in a word-picture matching task, to "covertly" (i.e., preverbally) retrieve the name from the picture and to use this name to attempt a match with the phonological form of the stimulus word. This mechanism, that we called "phonological" comprehension, would allow the identification of the correct target and would explain the choice of the phonologically related foil that was sometimes selected.

Aged↗
PubMed1991

Myotonic dystrophy: an electrophysiological study of cognitive deficits.

Patients with Myotonic Dystrophy (MyD) frequently suffer from a dysfunction of the primary sensory pathways, as documented by abnormalities of short-latency evoked potentials. Impairment of intellectual functions has been less extensively investigated. Short-latency brainstem auditory evoked potentials (BAEPs) as well as long-latency auditory event-related potentials (ERPs) were recorded from 5 female and 6 male patients affected by MyD. A simple discrimination ("oddball") paradigm was used to record ERPs to tones from Fz, Cz, Pz. Both BAEPs and ERPs were significantly altered as compared to normals. BAEP abnormalities were detected in 9 patients and ERP components N2 and P3 were delayed or absent for all patients, who nonetheless correctly discriminated between tones. These data indicate that CNS dysfunction in MyD involves not only primary sensory systems but also neural mechanisms underlying cognitive events and ERP generation.

Acoustic Stimulation↗
PubMed1991

Dissociation between knowledge of living and nonliving things in dementia of the Alzheimer type.

Patients who survive herpes simplex encephalitis (HSE) sometimes present a category-specific disorder for living things. Since HSE specifically involves the temporolimbic structures of both hemispheres, these structures could play a critical role in processing and storing information about living things. If this were the case, a category-specific disorder for the same items should also be observed in the early stages of dementia of the Alzheimer type (DAT) as the temporolimbic structures are often severely affected in this condition. To test this hypothesis, we administered to 15 DAT patients and to 10 normal controls a confrontation-naming task and a verbal associates recognition task, with both living and nonliving items as stimuli. The hypothesis was confirmed, since DAT patients performed worse with living than with nonliving items, and scored worse than normal controls on the living but not the nonliving items.

Alzheimer Disease↗
PubMed1989

Variation in the pattern of omissions and substitutions of grammatical morphemes in the spontaneous speech of so-called agrammatic patients.

We describe the patterns of omissions (and substitutions) of freestanding grammatical morphemes and the patterns of substitutions of bound grammatical morphemes in 20 so-called agrammatic patients. Extreme variation was observed in the patterns of omissions and substitutions of grammatical morphemes, both in terms of the distribution of errors for different grammatical morphemes as well as in terms of the distribution of omissions versus substitutions. Results are discussed in the context of current debates concerning the possibility of a theoretically motivated distinction between the clinical categories of agrammatism and paragrammatism and, more generally, concerning the theoretical usefulness of any clinical category. The conclusion is reached that the observed heterogeneity in the production of grammatical morphemes among putatively agrammatic patients renders the clinical category of agrammatism, and by extension all other clinical categories from the classical classification scheme (e.g., Broca's aphasia, Wernicke's aphasia, and so forth) to more recent classificatory attempts (e.g., surface dyslexia, deep dysgraphia, and so forth), theoretically useless.

Adult↗
PubMed1989

The influence of semantic and perceptual factors on lexical comprehension in aphasic and right brain-damaged patients.

We investigated whether the errors made by aphasic patients and right brain-damaged (RBD) patients on a word-picture matching test were differently related to the semantic and perceptual difficulties of the task. To this effect, the target picture was presented in one condition along with two semantically similar distractors, in another condition with two perceptually similar distractors, and in a third condition with two distractors that were both semantically and perceptually similar. There were also two control conditions in which part of targets that had been originally shown with semantic distractors were now presented with perceptual distractors and vice versa. The findings were consistent with the hypothesis that aphasics mainly fail when the task involves semantic discrimination and RBD patients when it involves perceptual discrimination. In aphasics the semantic perceptual condition produced the highest number of errors, but this was due, it was argued, to an increase of the semantic demands of the task.

Analysis of Variance↗
PubMed1986

Molecular forms of cholinesterases in CSF of Alzheimer's disease/senile dementia of Alzheimer type patients and matched neurological controls.

Acetylcholinesterase, pseudocholinesterase and their molecular forms were measured in the CSF of patients affected by Alzheimer's disease and of matched neurological controls. Three different molecular forms of ChE were found in the CSF of both groups of patients, but only two of them belonged to 'true' AChE. No differences were found between Alzheimer's disease patients and neurological controls in all the examined parameters.

Acetylcholinesterase↗
PubMed1986

Anomia with and without lexical comprehension disorders.

Anomic patients are usually described as free from language comprehension disorders, but the status of lexical comprehension in anomia is still controversial. Most anomic patients are impaired on tasks of semantic-lexical discrimination, but some of them do not present clear signs of semantic-lexical deficit at the receptive level. The aim of the present research was to elucidate the nature of word-finding disturbances by contrasting results obtained by anomic patients with and without lexical comprehension disorders on a number of variables, namely severity of anomia, implicit knowledge of words that patients failed to name, presence of verbal-semantic paraphasias, and scores obtained on a test of phoneme discrimination and on the "Token Test." The results of our investigation seem to suggest that there are two types of anomia, caused by the impairment of two different sets of mechanisms. In "purely expressive anomia" the locus of defect seems to be near to the stage in which the selected lexical item is specified into the appropriate phonological form. In "anomia with lexical comprehension disturbances" the locus of defect seems to be much deeper within the lexicon, so that the semantic disorder affects both the expressive and the receptive levels in a roughly comparable manner.

Adult↗
PubMed1986

Disorders of classificatory activity in aphasia.

Two nonverbal tasks of classificatory activity ("class inclusion" and "class intersection") were administered to 46 aphasics, 28 normal controls, 19 nonaphasic left-brain-damaged and 17 right-hemisphere-damaged patients in order to study if aphasic patients are more impaired than nonaphasic brain-damaged patients on these two tasks of elementary logic and if a relationship exists within the aphasic patients between inability to perform the tasks of classifiactory activity and impairment of the semantic-lexical level of integration of language. Results were for the most part in line with expectations because aphasics scored worse than normal controls and nonaphasic brain-damaged patients (even if the difference reached the level of statistical significance only on the test of "class intersection") and within the aphasic patients the worst results were obtained by subjects presenting clear signs of semantic-lexical disintegration.

Aphasia↗
PubMed1986

Mechanisms of unilateral spatial neglect in relation to laterality of cerebral lesions.

An Overlapping Figures test, considered as appropriate to study focusing of attention on small but complex stimuli falling in the central parts of visual field and a Searching for Animals test, designed to study the exploration of large parts of extrapersonal space, were administered to 38 controls, and 90 right and 82 left brain-damaged patients. The investigation was designed to test the hypothesis that the extent of space to be explored may have a different influence on unilateral spatial neglect of right and left brain-damaged patients. Both right and left brain-damaged patients showed an asymmetric exploration of space on the Searching for Animals test, making more omissions on the side contralateral to the damaged hemisphere than on the ipsilateral one. On the Overlapping Figures test, however, only right brain-damaged patients showed a clear tendency to omit figures lying on the left side of the composite pattern. This finding suggests that inability to extract visual information from one side of the stimuli during single eye fixations may be the most characteristic feature of unilateral spatial neglect resulting from right hemisphere lesions.

Attention↗
PubMed1985

Cognitive analysis of a case of pure dysgraphia.

An Italian patient with a pure dysgraphia who incorrectly spelled words and nonwords is described. The spelling errors made by the patient were not affected by lexical factors (e.g., frequency, form class) and were qualitatively the same for words and nonwords. The pattern of writing performance is discussed in relation to current models of writing and, specifically, in relation to the role of the Output Grapheme Buffer and Phoneme-Grapheme Conversion in writing.

Cerebrovascular Disorders↗
PubMed1984

On the basis for the agrammatic's difficulty in producing main verbs.

Current theories of agrammatism do not provide a clear explanation for the co-occurrence of omission of grammatical markers and main verbs in this disorder. This study tested the hypothesis that the two symptom features have distinct underlying causes. Specifically, that the omission of main verbs in agrammatic speech is caused, at least in part, by a lexical (as opposed to a syntactic) deficit. Agrammatic and anomic aphasics and normal controls were given an object and action naming test. Agrammatic patients showed a marked impairment in naming actions in contrast to anomic aphasics and normal controls who named actions better than objects. The action naming impairment in agrammatic patients was interpreted as evidence for the lexical deficit hypothesis of verb omission in the speech of these patients and as a demonstration that agrammatism is a heterogeneous disorder that implicates damage to both lexical and syntactic mechanisms.

Adult↗
PubMed1983

The production of morphological and lexical opposites in aphasia.

Four unselected groups of Broca's, Wernicke's, conduction, amnesic aphasic patients and a group of normal controls were asked to produce the best opposite of 60 adjectives. For half of the stimuli the expected opposite was morphologically related to the stimulus word (e.g. "formal"/"informal"), for the other half it could be obtained only by selecting a new base-form within the lexicon (e.g. "good"/"bad"). Following some neurolinguistic observations by Hécaen et al., it was predicted that amnesic patients should produce mainly morphological opposites, whereas conduction aphasics should produce mainly lexical antonyms. Results confirmed the predictions, since amnesic aphasics showed a prevalent impairment in the selection lexical opposites, whereas conduction aphasics showed a selective impairment in the production of morphological antonyms.

Anomia↗
PubMed1983

Drawing objects from memory in aphasia.

The ability of aphasic patients to draw from memory objects with a characteristic shape has been investigated. Their capacity to reproduce the form of real objects was studied by showing them for a short time line drawings of simple objects. When the patient had analysed and recognized the figure, the model was hidden from view and the subject was asked to draw the same object from memory. This Drawing from Memory task was administered to 54 aphasics, 67 patients with right hemisphere lesions, 44 nonaphasic left brain-damaged patients and 23 normal controls. The influence of visuoconstructive disabilities was controlled by administering to the same patients a standard test for constructional apraxia (copying 10 geometrical figures). The severity and clinical form of the aphasia and the presence of semantic-lexical impairment at the receptive level were also examined in the aphasic patients. The following results were obtained. (1) Aphasic patients scored significantly less well than the control groups on the Drawing from Memory task and the intergroup differences became greater when the scores from the test for constructional apraxia were included by an analysis of covariance. (2) No significant correlation was detected between the severity and clinical form of the aphasia and the scores obtained on the Drawing from Memory task. (3) There was a significant correlation between impaired drawing from memory and disruption at the semantic-lexical level of language integration.

Aged↗
PubMed1981

The relationship between type of naming error and semantic-lexical discrimination in aphasic patients.

When submitted to confrontation naming tasks, aphasic patients show different types of naming errors: phonetic, phonemic and verbal-semantic paraphasias, neologisms and anomia, but it is generally difficult to decide whether these errors are mainly due to a breakdown of the semantic systems or to post-lexical phonological disorders. In order to clarify this issue, 118 aphasic patients were given 3 tests of confrontation naming and 3 tests of semantic-lexical discrimination. Naming errors on confrontation were used to classify aphasic patients in various subgroups (according to the prevalence of a given type of naming error), whereas performances obtained on tests of semantic-lexical discrimination were taken as an index of disorganization of the semantic systems. The performances on semantic discrimination tests of patients showing a prevalence of phonetic, phonemic and verbal-semantic paraphasias, neologisms and anomia on confrontation naming tasks were compared. A very small number of semantic discrimination errors was obtained by patients showing a prevalence of phonetic and phonemic transformations on confrontation, whereas a much larger number of semantic discrimination errors was obtained by patients showing a prevalence of verbal-semantic paraphasias, neologisms and anomia.

Anomia↗
PubMed1981

Neuropsychological correlates of localized cerebral lesions in non-aphasic brain-damaged patients.

A neuropsychological test battery made up of verbal, visual-spatial, and intelligence tests was administered to 82 right and 67 on-aphasic left brain-damaged patients with localized cerebral lesions, in order to draw impairment profiles of the various subgroups. Separate analyses were undertaken on patients with unilobar and multilobar lesions. As for hemisphere effects, LH patients performed worse than RH subjects on verbal tests, while the reverse was true for visual-spatial tasks. As for lobe effects, patients with frontal lobe damage fared worse than other subgroups on word fluency, independent of the side of the lesion. RH patients with multilobar posterior lesions were significantly more impaired than other RH subgroups on the test of Copying Drawings with Landmarks, probably owing to the detrimental effect of unilateral spatial neglect on tasks requiring an accurate visual-spatial analysis.

Brain Damage, Chronic↗