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N Raz

Publications and source records attributed to N Raz.

At least 19 recordsLinked to original sources
PubMed1995

Age, gender, and hemispheric differences in human striatum: a quantitative review and new data from in vivo MRI morphometry.

We reviewed postmortem and neuroimaging studies of striatal neuroanatomy in humans. The quantitative review revealed evidence of moderate age-related shrinkage of the caudate nucleus and the putamen and consistent leftward asymmetry of the globus pallidus. The data on sex differences were very sparse. We examined neostriatal structures in two samples (healthy volunteers and patients with negative radiological findings) using in vivo magnetic resonance imaging. In both samples, bilateral age-related shrinkage of the caudate nucleus was found, although among the patients the effect was significant only for males. The putamen was measured only in the second sample, and age-related reduction in its volume was found also only among males. A trend for rightward asymmetry in the volume of caudate nucleus was observed in both samples, although it reached statistical significance only among the patients. Putative pathological and physiological mechanisms underlying the observed differences in teh neostriatum are discussed.

Adolescent↗
PubMed1995

Selective neuroanatomic abnormalities in Down's syndrome and their cognitive correlates: evidence from MRI morphometry.

We examined the pattern of neuroanatomic abnormalities in adults with Down's syndrome (DS) and the cognitive correlates of these abnormalities. Specifically, we compared this pattern with what would be predicted by the hypotheses attributing DS pathology to either premature aging or Alzheimer's disease. We measured a number of brain regions on MRIs of 25 subjects: 13 persons with the DS phenotype and 12 age- and sex-matched healthy volunteers. Study participants had no history of cardiovascular disease, diabetes, thyroid dysfunction, or seizure disorder. After statistical adjustment for differences in body size, we found that, in comparison with controls, DS subjects had substantially smaller cerebral and cerebellar hemispheres, ventral pons, mammillary bodies, and hippocampal formations. In the cerebellar vermis of DS subjects, we observed smaller lobules VI to VIII without appreciable differences in other regions. In addition, we noted trends for shrinkage of the dorsolateral prefrontal cortex, anterior cingulate gyrus, inferior temporal and parietal cortices, parietal white matter, and pericalcarine cortex in DS subjects compared with normal controls. The parahippocampal gyrus was larger in DS subjects. We found no significant group differences in the volumes of the prefrontal white matter, the orbitofrontal cortex, the pre- and postcentral gyri, or the basal ganglia. We conclude that the pattern of selective cerebral damage in DS does not clearly fit the predictions of the premature aging or Alzheimer's disease hypotheses. To examine the relationship between brain abnormalities and cognitive deficits observed in DS, we correlated the size of brain regions that were significantly reduced in DS with performance on tests of intelligence and language. The correlation analysis suggested age-related decline in the DS subjects in general intelligence and basic linguistic skills. General intelligence and mastery of linguistic concepts correlated negatively with the volume of the parahippocampal gyrus. There was no relationship between total brain size and the cognitive variables.

Adult↗
PubMed1994

Procedural and declarative memory: a developmental study.

Measures of procedural and declarative memory were administered to 88 children forming two groups, aged 8 and 12. Two measures of priming, Gollin Figures and Degraded Words, were compared to declarative measures of recall. Strong support for a developmental dissociation between priming tasks and declarative memory was found. Both age groups showed a similar amount of priming facilitation, yet a significant age effect was observed for the declarative recall tasks. Current findings demonstrate that the level of procedural memory performance stabilizes during a period of development when declarative memory continues to improve.

Association Learning↗
PubMed1994

Toward the neural basis of verbal priming: a cognitive-neuropsychological synthesis.

Repetition priming is a mnemonic phenomenon that has attracted considerable attention from neuropsychologists and cognitive scientists. In an attempt at elucidating the putative mechanisms of priming, the present review draws on evidence from both domains. The review is restricted to verbal priming of visually presented stimuli--an area that accounts for the majority of empirical studies of priming. A number of theoretical accounts are presented. The interim conclusion is that neither multiple systems nor unitary system-multiple process theories can adequately explain the data on priming, although both contain many valid components. An integrative model is proposed to improve the explanation of the empirical evidence. The central assertion of the proposed model is that repetition priming depends on perceptual processes that can be mapped on specific neural systems. It is postulated that individual differences in perceptual processing ability predict variability in memory performance. It is proposed that data-driven priming of verbal stimuli critically depends on the activity of primary and secondary visual cortices in the right hemisphere, whereas conceptually-driven priming is hypothesized to rely on the activities of higher order tertiary association cortices in language areas and more anterior neocortical areas.

Alzheimer Disease↗
PubMed1994

Memory for facts, source, and context: can frontal lobe dysfunction explain age-related differences?

Age-related differences in memory for facts, source, and contextual details were examined in healthy young (18-35 years old) and old (65-80 years old) volunteers. In all tested memory functions, decline over time was greater in the elderly than in the young. A time-dependent increase in the prevalence of source amnesia errors was clearly associated with old age. Contrary to several recent reports, measures of frontal lobe functions did not predict source memory. Nevertheless, some of these putative frontal function measures were related to memory for contextual details. The number of perseverative responses on the Wisconsin Card Sorting Test was inversely related to performance on both factual and contextual memory tests, but the association with contextual memory was stronger. Difficulties with response selection on a Stroop task predicted poor contextual memory in young but not in old adults.

Adolescent↗
PubMed1992

Age-related regional differences in cerebellar vermis observed in vivo.

We investigated age-related differences in the cerebellar vermis. The areas of five vermal regions of interest were estimated from digitized midsagittal magnetic resonance imaging scans of 29 healthy volunteers and 30 neurologically intact patients (aged 18 to 78 years) who were free of vestibular symptoms, seizures, psychosis, or alcoholism. The five regions of interest included the following: (1) lingula and centralis, (2) culmen, (3) declive, folium, and tuber, (4) pyramis, and (5) uvula and nodulus. The ventral pons was used as a control region. After covarying skull size, we found a significant age-related reduction in the total area of the cerebellar vermis. The area of the dorsal regions declined with age, whereas the ventral segments of the vermis--lingula-centralis and uvula-nodulus--showed no significant age-related shrinkage. Notably, the area of the most dorsomedial portion, the declive-folium-tuber, tended to be more strongly associated with age than other segments. The pontine area was unaffected by age. No sex differences were found in the area of the vermis or its subdivisions, but the ventral pontine area was larger in male subjects than in female subjects, even after adjustment for skull size. The mechanisms underlying the observed differences are unclear. It appears, however, that phylogenetically more recent vermal regions, which are late to mature and are endowed with more extensive cortical connections, are the most vulnerable to the effects of aging.

Adolescent↗
PubMed1992

Age-related shrinkage of the mamillary bodies: in vivo MRI evidence.

Mamillary body (MB) is a diencephalic structure hypothesized to be involved in memory, a cognitive function that declines with age. In this study, age-related differences in the size of MB were examined in vivo using magnetic resonance (MR) imaging. The cross-sectional area of the MB was estimated from MR images of the brain in healthy volunteers and neurologically intact patients (age 18-78). The cross-sectional area of the tectum was used as a control region of interest. We found a significant age-related reduction in the area of the MB, but not of the tectum. No sex differences were observed in the size of either structure.

Adolescent↗
PubMed1990

Mechanism of age-related differences in frequency discrimination with backward masking: speed of processing or stimulus persistence?

In Experiment 1, frequency-discrimination thresholds were estimated in a 2-interval, forced-choice, backward masking procedure with a masker acoustically dissimilar to the targets. Young subjects were more efficient in escaping the effects of masking than were their elderly counterparts. In Experiment 2, young and elderly subjects performed the same task, with a masker acoustically similar to the targets and with a target-dissimilar masker. Under target-similar masking and at short target-masker intervals, the elderly demonstrated significant improvement, reaching the level of performance of the young, whereas under the target-dissimilar masker, the age-related differences were restored. Both age-related slowing of information processing and increase in stimulus persistence can account for the results of Experiment 1, but only increased stimulus persistence explains the results of Experiment 2.

Adolescent↗
PubMed1990

Structural brain abnormalities in the major psychoses: a quantitative review of the evidence from computerized imaging.

The neuroimaging literature on structural brain abnormalities in the major psychoses is quantitatively reviewed. The mean effect size for studies of lateral ventriculomegaly in schizophrenia (d = .70) corresponded to 43% nonoverlap between the distributions of schizophrenics and control Ss. Planimetry yielded larger effects than linear methods of ventricular size estimation. Although enlargement of the third ventricle was comparable to that of lateral ventriculomegaly (d = .66), it was found to be significantly greater after differences in measurement method were taken into account. The average cumulative length of hospitalization, adjusted for patients' age and duration of illness, predicted ventriculomegaly in schizophrenia. Studies on schizophrenia and affective disorder differed neither in the extent of reported ventriculomegaly nor in the amount of "cortical atrophy."

Brain↗
PubMed1988

Ventriculomegaly in schizophrenia: is the choice of controls important?

The issue of adequate controls for the study of ventriculomegaly in schizophrenia has been explored initially by Andreasen et al. (1982), who proposed that healthy volunteers, a group with presumably smaller ventricles than medical controls, be considered the optimal comparison group in this area of research. Recently, Smith and Iacono (1986) suggested that group differences may appear to be greater when controls who are patients are used, as a result of the systematic exclusion of medical patients with large though normal ventricles. We conducted a meta-analysis of 37 studies of lateral ventriculomegaly in schizophrenia to clarify this issue. The results indicate that the average effect size in studies with healthy controls does not differ significantly from that obtained in studies employing medical, neurological, or psychiatric (nonpsychotic) controls. Thus, any group without gross neurological damage or severe psychopathology may be used for establishing ventriculomegaly in schizophrenia.

Cerebral Ventricles↗
PubMed1987

Visual augmenting/reducing and P300 in autistic children.

Visual event-related potentials were recorded from five male autistics and five matched controls. Sensory effects were investigated by having subjects passively view flashes of three different but equiprobable intensities (augmenting/reducing paradigm). Cognitive effects were examined by having subjects count infrequent, target, flashes of one intensity embedded within a series of frequent, nontarget, flashes of a different intensity (oddball paradigm). In the augmenting/reducing paradigm, the sensory N100 wave of autistic but not controls showed a significant increase in amplitude (augmenting) as flash intensity increased. The cognitive P300 wave of autistics did not differ from controls in the oddball paradigm. Unlike controls, autistics had an equally large P300 in the no-task augmenting/reducing paradigm. It is concluded that autistics may experience a degree of stimulus overload in the visual modality.

Adolescent↗
PubMed1987

Morphological brain abnormalities in schizophrenia determined by computed tomography: a problem of measurement?

The size of the cerebral ventricles was estimated from computed tomographic (CT) scans of 14 young patients with schizophrenia and 12 medical controls. The subjects were a representative subsample from a larger sample studied by Boronow et al. (1985). Although no CT abnormalities were detected in the psychiatric patients using traditional measures (mechanical planimetry for the lateral ventricles and a linear measure for the third ventricle), a volumetric analysis of the same 26 scans revealed enlargement of the lateral and third ventricles in the schizophrenics. The effect revealed by volumetric measures of the lateral ventricles was 58% greater than that obtained with digital planimetry and 96% greater than the effect found using mechanical planimetry. No differences were found between volumetric and digital planimetric measures of the third ventricle, but the effect revealed by the latter measure was 114% greater than that obtained by a linear index. It is suggested that volumetric measures of lateral ventricles based on information from several CT slices may be more sensitive to group differences in ventricular size than planimetry. Likewise, area measures of the third ventricle may be more sensitive to group differences than linear measures.

Adolescent↗
PubMed1987

Volumetric asymmetries of the human brain: intellectual correlates.

Volumetric measures of the brain and ventricles were derived from CT films and related to intellectual variables from the Wechsler Adult Intelligence Scale (WAIS). Subjects were patients referred for neurological examination for headache or somatic complaints, sometimes accompanied by anxiety or dysphoric affect (N = 41), for whom a comprehensive neurological work-up revealed no evidence of abnormality. The asymmetry of hemispheric volume (left minus right over total, times 100) was correlated (r = .57, p less than .001) with Verbal IQ minus Performance IQ within subjects. No relationship was observed between total brain or hemispheric volumes and IQ scores. Brain and ventricular volumes were larger for the left hemisphere than the right.

Brain↗
PubMed1987

Effects of fenfluramine on EEG and brainstem average evoked response in infantile autism. Preliminary investigation.

The effects of fenfluramine on electrophysiological activity in autistic children were assessed by computerized EEG power analysis and brainstem evoked responses (BSER). Prolonged administration of fenfluramine resulted in a decrease of relative share of alpha-waves in the EEG power spectrum and in corresponding increase in slow activity. No effects of the drug on BSER latencies were observed. The spectral EEG pattern of fenfluramine identified in this sample was compared to the spectra reported for normal volunteers on an acute dose of fenfluramine. The implications of these findings for EEG classification of fenfluramine and neurochemical mechanisms of autism are discussed.

Adolescent↗
PubMed1987

No effect of chronic fenfluramine on the P300 component of the event-related potential.

Five autistic children were administered a visual version of the oddball paradigm under both drug (chronic fenfluramine) and placebo conditions. The P300 component of the event-related potential (ERP) was not affected by fenfluramine, although the drug significantly lowered blood concentrations of serotonin. It was concluded that serotonin as a neurotransmitter does not play a major role in production of P300. This conclusion fits with the facts that: (1) the general functional role of serotonin in the nervous system is to globally inhibit the overt expression of behavior, and (2) P300 is generally insensitive to response selection processes.

Autistic Disorder↗
PubMed1987

Relationship between cognitive and morphological asymmetry in dementia of the Alzheimer type: a CT scan study.

In this study we investigated the association between morphological asymmetry and patterns of cognitive ability in dementia of Alzheimer's type (DAT). Digitized CT scans were used to estimate volumetric parameters of the brain. The volume of the cranium, brain parenchyma, the subarachnoid space, and lateral ventricles was computed. The volume of the subarachnoid space was used as an index of cortical atrophy, while the ventricular volume served as an estimate of subcortical atrophy. Asymmetry indices were computed for all structures as the difference between left and right volume divided by their average and multiplied by 100. Cognitive asymmetry index was computed by dividing the difference between VIQ and PIQ of the Wechsler Adult Intelligence Scale (WAIS) by their average and multiplying by 100. After statistically controlling for cranial asymmetry, hemispheric asymmetry was found to correlate positively with cognitive asymmetry. The correlation was somewhat greater for male than for female patients. Asymmetry of both cortical and subcortical atrophy correlated negatively with cognitive asymmetry.

Aged↗
PubMed1986

Brain stem evoked response suppression during speech production.

Auditory brain stem evoked responses (BSERs) to repetitive clicks were recorded in subjects engaged in overt speech, whispering, silent articulation, and covert verbal rehearsal tasks and during a control condition of attending to the clicks. Overt speech and whispering resulted in a significant amplitude reduction of the fifth peak of BSERs without affecting the amplitudes or the latencies of the earlier peaks. These data strongly suggest efferent inhibition of irrelevant auditory input at the level of the upper brain stem.

Adolescent↗