Search PubMed⌕ Search

Biomedical subjects

M S Buchsbaum

Publications and source records attributed to M S Buchsbaum.

At least 37 records · Page 2Linked to original sources
PubMed2000

Hemispheric asymmetry for selective attention.

A letter-identification task, previously demonstrated to show activation of the pulvinar nucleus of the thalamus with fluodeoxyglucose position emission tomography, was administered to 20 normal volunteers. The letter to be detected could appear alone as a big stimulus or as a small one stimulus surrounded by flanking letters. To test for a hemispheric specialization for filtering processes, the stimuli were displayed horizontally, either in the left or in the right hemifield, or vertically, either above or below the fixation point. In addition, to study the effect of cognitive processes on selective attention resources, we varied the feedback conditions, by delivering or not delivering a blue flash in cases of misses or mistakes. The results show a significant interaction between the type of stimulus (alone or surrounded by flankers) and the hemifield of presentation (left or right) only in the condition where the subjects were presented stimuli horizontally without any feedback. In this condition, reaction times (RTs) were shorter in the left hemifield than in the right hemifield for single stimuli, whereas for stimuli surrounded by flankers, the opposite pattern was observed, that is, shorter RT in the right hemifield than in the left one. The present findings suggest a hemispheric specialization for selective attention, in particular at the subcortical level.

Adult↗
PubMed2000

Visual target detection paradigm for the study of selective attention.

The current protocol can be used to examine selective attention. It has been used to acquire behavioral performance data in neurologically healthy normal control subjects and schizophrenic patients. A modified version, also described here, has been used to acquire functional neuroimaging data in normal subjects using positron emission tomography. Subject response accuracy and reaction times are recorded while subjects detect visual stimuli in either hemifield (left vs. right of a fixation point) or along the vertical meridian (above or below fixation). The lateralized presentation of stimuli permits the study of hemispheric specialization for selective attentional processes. Attentional load is manipulated by presenting larger-sized target stimuli alone (i.e., the letter 'O') or smaller-sized target stimuli surrounded by flanking letters. This protocol report includes a description of subject exclusion criteria, procedural details, relevant experimental conditions and variables, suggestions for data analysis, expected results, and a discussion of the protocol's significance for attentional research along with suggestions for future research.

Attention↗
PubMed2000

Feeling unreal: a PET study of depersonalization disorder.

OBJECTIVE: The goal of this study was to assess brain glucose metabolism and its relationship to dissociation measures and clinical symptoms in DSM-IV depersonalization disorder. METHOD: Positron emission tomography scans coregistered with magnetic resonance images of eight subjects with depersonalization disorder were compared to those of 24 healthy comparison subjects. The two groups did not differ in age, sex, education, performance on a baseline neuropsychological battery, or performance on a verbal learning task administered during [(18)F]fluorodeoxyglucose uptake. A cortical analysis by individual Brodmann's areas was performed. RESULTS: Compared to the healthy subjects, subjects with depersonalization disorder showed significantly lower metabolic activity in right Brodmann's areas 22 and 21 of the superior and middle temporal gyri and had significantly higher metabolism in parietal Brodmann's areas 7B and 39 and left occipital Brodmann's area 19. Dissociation and depersonalization scores among the subjects with depersonalization disorder were significantly positively correlated with metabolic activity in area 7B. CONCLUSIONS: Depersonalization appears to be associated with functional abnormalities along sequential hierarchical areas, secondary and cross-modal, of the sensory cortex (visual, auditory, and somatosensory), as well as areas responsible for an integrated body schema. These findings are in good agreement with the phenomenological conceptualization of depersonalization as a dissociation of perceptions as well as with the subjective symptoms of depersonalization disorder.

Adult↗
PubMed2000

Limbic circuitry in patients with autism spectrum disorders studied with positron emission tomography and magnetic resonance imaging.

OBJECTIVE: Cytoarchitectonic changes in the anterior cingulate cortex, hippocampus, subiculum, entorhinal cortex, amygdala, mammillary bodies, and septum were reported in a postmortem study of autism. Previously, the authors found smaller cingulate volume and decreased metabolism of the cingulate in seven autistic patients. In this study, they measured the volume and glucose metabolism of the amygdala, hippocampus, and cingulate gyrus in an expanded group of 17 patients with autism spectrum disorders (autism [N=10] or Asperger's disorder [N=7]) and 17 age- and sex-matched healthy volunteers. METHOD: Subjects performed a serial verbal learning test during (18)F-deoxyglucose uptake. The amygdala, hippocampus, and cingulate gyrus were outlined on magnetic resonance imaging scans, volumes of the structures were applied to matching coregistered positron emission tomography scans, and three-dimensional significance probability mapping was performed. RESULTS: Significant metabolic reductions in both the anterior and posterior cingulate gyri were visualized in the patients with autism spectrum disorders. Both Asperger's and autism patients had relative glucose hypometabolism in the anterior and posterior cingulate as confirmed by analysis of variance; regional differences were also found with three-dimensional significance probability mapping. No group differences were found in either the metabolism or the volume of the amygdala or the hippocampus. However, patients with autism spectrum disorders showed reduced volume of the right anterior cingulate gyrus, specifically in Brodmann's area 24'. CONCLUSIONS: Compared with age- and sex-matched healthy volunteers, patients with autism spectrum disorders showed significantly decreased metabolism in both the anterior and posterior cingulate gyri.

Adult↗
PubMed1999

d,l-fenfluramine response in impulsive personality disorder assessed with [18F]fluorodeoxyglucose positron emission tomography.

Reduced serotonergic activity has been associated with impulsive aggression in personality disordered patients in metabolite and pharmacologic challenge studies. This study used positron emission tomography to explore whether reduced serotonergic function occurs in critical brain regions such as orbital frontal and cingulate cortex that, may play a role in modulating aggression. Six impulsive-aggressive patients and five healthy volunteers were evaluated for changes in regional glucose metabolism after administration of the serotonergic releasing agent d,l-fenfluramine (60 mg, p.o.) or placebo. Volunteers demonstrated increases in orbital frontal and adjacent ventral medial frontal cortex, cingulate, and inferior parietal cortex, whereas impulsive-aggressive patients showed no significant increases in glucose metabolism after fenfluramine in any region. Compared with volunteers, patients showed significantly blunted metabolic responses in orbital frontal, adjacent ventral medial and cingulate cortex, but not in inferior parietal lobe. These results are consistent with reduced serotonergic modulation of orbital frontal, ventral medial frontal, and cingulate cortex in patients with impulsive-aggressive personality disorders.

Adult↗
PubMed1999

Visualizing fronto-striatal circuitry and neuroleptic effects in schizophrenia.

Disturbances in fronto-striatal circuitry have been postulated to be important in schizophrenia. Positron emission tomography typically shows decreased metabolic rates in these areas relative to other brain areas in schizophrenia. After treatment with typical neuroleptics, striatal metabolic rates are increased, but other brain areas tend not to show significant changes. Atypical neuroleptics less markedly affect striatal metabolic rates, but show wider cortical effects. In order to examine fronto-striatal circuitry, a technique for visualizing the correlations between metabolic rates in all brain areas was applied in 33 controls and 27 unmedicated schizophrenic patients. Correlation images revealed strong fronto-striatal connections in controls, but weak fronto-striatal links in schizophrenic patients. Changes in striatal circuits, also reflected in recent anatomical studies, may be important for understanding antipsychotic effects.

Adult↗
PubMed1999

Prediction of antidepressant effects of sleep deprivation by metabolic rates in the ventral anterior cingulate and medial prefrontal cortex.

OBJECTIVE: Sleep deprivation has been shown to have an antidepressant benefit in a subgroup of depressed patients. Functional imaging studies by the authors and others have suggested that patients with elevated metabolic rates in the anterior cingulate gyrus at baseline are more likely to respond to either sleep deprivation or antidepressant medications than patients with normal metabolic rates. The authors extend their earlier work in a larger group of patients and explore additional brain areas with statistical probability mapping. METHOD: Thirty-six patients with unipolar depression and 26 normal volunteers were studied with positron emission tomography before and after sleep deprivation. Response to sleep deprivation was defined as a 40% or larger decrease in total scores on the Hamilton Depression Rating Scale. RESULTS: One-third of the depressed patients had a significant response to sleep deprivation. Responders had higher relative metabolic rates in the medial prefrontal cortex, ventral anterior cingulate, and posterior subcallosal gyrus at baseline than depressed patients who did not respond to sleep deprivation and normal volunteers. Lower Hamilton depression scores correlated significantly with lower metabolic rates in the left medial prefrontal cortex. After sleep deprivation, significant decreases in metabolic rates occurred in the medial prefrontal cortex and frontal pole in the patients who responded positively to sleep deprivation. CONCLUSIONS: High pretreatment metabolic rates and decreases in metabolic rates after treatment in the medial prefrontal cortex may characterize a subgroup of depressed patients who improve following sleep deprivation and, perhaps, other antidepressant treatments.

Adolescent↗
PubMed1999

Three-dimensional analysis with MRI and PET of the size, shape, and function of the thalamus in the schizophrenia spectrum.

OBJECTIVE: In an exploration of the schizophrenia spectrum, the authors compared thalamic size, shape, and metabolic activity in unmedicated patients with schizophrenia and schizotypal personality disorder to findings in age- and sex-matched healthy control subjects. METHOD: Coregistered magnetic resonance imaging (MRI) and positron emission tomography scans were obtained in 27 schizophrenic patients, 13 patients with schizotypal personality disorder, and 32 control subjects who performed a serial verbal learning test during tracer uptake. After thalamus edges were outlined on 1.2-mm MRI scans, a radial warping program yielded significance probability mapping in three dimensions. RESULTS: Significance probability mapping (with resampling) identified an area in the region of the mediodorsal nucleus bilaterally with significantly lower relative metabolism in the schizophrenia group than in either the control or schizotypal personality disorder groups, which did not differ from each other. The three groups did not differ significantly in total thalamic volume in square millimeters or thalamic volume relative to brain volume. Shape analyses revealed that schizophrenic patients had significantly fewer pixels in the left anterior region, whereas patients with schizotypal personality disorder had significantly fewer pixels in the region of the right mediodorsal nucleus than did control subjects. CONCLUSIONS: Schizophrenic patients showed significant metabolism and shape differences from control subjects in selective subregions of the thalamus, whereas patients with schizotypal personality disorder showed only a difference in shape. Because the mediodorsal and anterior nuclei have different connections with limbic and prefrontal structures, the anterior thalamic shrinkage and mediodorsal metabolic and shape changes might relate to the different clinical pictures in schizotypal personality disorder and schizophrenia.

Adult↗
PubMed1998

A method of basal forebrain anatomical standardization for functional image analysis.

Functional as well as structural assessment of the basal forebrain has mostly focused on the dorsal caudate and putamen in axial slices where they are easily outlined or their centers located with stereotaxic methods. The more ventral extent of the basal forebrain, where the irregular form and indistinct boundaries of the nucleus accumbens and substantia innominata are difficult to trace and where the brain's ventral surface may contribute partial volume artifacts to measurement, has been less studied. We present a method based on coronal sections, landmarks placed on clearly visible anchor points, and the computational technique of thin-plate spline warping which allows the alignment of groups of individuals to common coordinates for pixel-by-pixel statistical mapping. The reliability of the landmarks across independent raters yields a median absolute difference of 1.3-1.6 mm. The validity of the method is confirmed by variance maps which reveal significant decreases in variance over spindle and bounding box alignment.

Adult↗
PubMed1998

Diabetic ketoacidosis associated with cocaine use.

BACKGROUND: Multiple risk factors for diabetic ketoacidosis (DKA) have been described, including omission of insulin therapy and clinical conditions known to increase counterregulatory hormones. Recently, substance abuse has been identified in patients with DKA. We observed many cases of DKA in cocaine users, although the association between cocaine use and DKA has not been well described in the medical literature. METHODS: We performed a retrospective case-control study of admissions for DKA in cocaine users and non-user controls in an urban teaching hospital from January 1, 1985, to December 31, 1994. RESULTS: We identified 720 adult admissions for DKA. Twenty-seven cocaine users accounted for 102 admissions (14% of all DKA admissions). The users were compared with 85 nonuser controls who had 154 DKA admissions. Cocaine users had more admissions for DKA (mean, 3.78 vs 1.81; P = .03). Cocaine users were less likely than controls to have an intercurrent illness identified as a precipitating factor for DKA (14.7% vs 33.1%; P<.001) and were more likely to have missed taking insulin prior to admission (45.1% vs 24.7%; P<.001). Although cocaine users had higher serum glucose levels on admission (32.9 mmol/L [593.4 mg/dL] vs 29.5 mmol/L [531.1 mg/dL]; P =.03), no differences in intensity of illness or treatment outcome were detected. CONCLUSIONS: In this preliminary study, cocaine use was found in a significant number of adults admitted with DKA and was associated with more frequent omission of insulin therapy and the absence of precipitating systemic illness. Either because of its association with insulin therapy omission or its effects on counterregulatory hormones, cocaine use should be considered a risk factor for DKA, particularly in patients with multiple admissions.

Adult↗
PubMed1998

Ventricular enlargement in poor-outcome schizophrenia.

BACKGROUND: A subset of patients with schizophrenia, defined on the basis of longitudinal deficits in self-care, may show a classic ("Kraepelinian") degenerative course. An independent validator of the phenomenologically defined Kraepelinian subtype might be provided by a structural indicator of possible brain degeneration: ventricular size as measured by computed tomography (CT). METHODS: To examine whether Kraepelinian patients would show a differential increase in ventricular size over time, two CT scans were conducted at intervals separated by > 4 years, an average of 5 years. Fifty-three male patients with DSM-III-R diagnoses of chronic schizophrenia were subdivided into Kraepelinian (n = 22; mean age = 42 +/- 6 years) and non-Kraepelinian (n = 31; mean age = 38 +/- 12.2 years) subgroups. Kraepelinian patients were defined on the basis of longitudinal criteria: > 5 years of complete dependence on others for life necessities and care, lack of employment, and sustained symptomatology. Thirteen normal elderly volunteers (mean age = 60 +/- 17.8) were also scanned at 4-year intervals. CT measurements were made by raters without knowledge of subgroup membership. A semiautomated computer program was used to trace the anterior horn, lateral ventricles, and temporal horns for each slice level on which they were clearly seen. RESULTS: The ventricles showed a bilateral increase in size over the 4-year interval in the Kraepelinian subgroup, more marked in the left hemisphere than the right. By contrast, neither the non-Kraepelinian subgroup nor the normal volunteers showed significant CT changes from scan 1 to scan 2. CONCLUSIONS: Thus, the longitudinal dysfunctions in self-care that characterize the Kraepelinian patients were associated with an independent indicator of brain abnormality.

Adult↗
PubMed1998

MRI white matter diffusion anisotropy and PET metabolic rate in schizophrenia.

A disturbance in the frontal-striatal-thalamic circuitry has been proposed for schizophrenia, but this concept has been based primarily on indirect evidence from psychopharmacology and analogies with animal research. Diffusion tensor imaging, a new MRI technique that permits direct assessment of the large axon masses stretching from the prefrontal cortex to the striatum, was used to study white matter axon bundles. Diffusion tensor images, high-resolution structural MRI and positron emission tomography scans with 18-fluorodexoyglucose were obtained on five patients with schizophrenia and six age- and sex-matched normal controls. Significantly lower diffusion anisotropy in the white matter of the prefrontal cortex in schizophrenic patients than in normal controls was observed in statistical probability maps. Co-registered PET scans revealed significantly lower correlation coefficients between metabolic rates in the prefrontal cortex and striatum in patients than in controls. These twin findings provide convergent evidence for diminished fronto-striatal connectivity in schizophrenia.

Adult↗
PubMed1998

Dorsal striatal size, shape, and metabolic rate in never-medicated and previously medicated schizophrenics performing a verbal learning task.

BACKGROUND: Magnetic resonance imaging and positron emission tomography were used to study the size and metabolic rate of the caudate and the putamen in 18 patients with schizophrenia (n=16) or schizo-affective disorder (n=2) and 24 age- and sex-matched control subjects. METHODS: The patients were either never medicated (n=7) or drug free (n=11) for a median of 3 weeks. During uptake of fludeoxyglucose F 18, all patients performed a serial verbal learning test. Positron emission tomographic and magnetic resonance imaging scans were coregistered, and the caudate and the putamen were traced on the magnetic resonance image. RESULTS: The striatum had a significantly lower relative metabolic rate in schizophrenics than in controls. Never-medicated patients had lower metabolic rates in the right putamen (ventral part of the dorsal striatum) than previously medicated patients. The caudate was significantly smaller in never-medicated patients than in controls and largest in previously medicated patients. Patients with higher relative metabolic rates in the putamen scored higher on the Abnormal Involuntary Movements Scale. CONCLUSIONS: The findings are consistent with reports of striatal enlargement in previously medicated patients and size increases after neuroleptic treatment. Never-medicated patients, in contrast, had ventral striatal structures that were smaller and less active than those observed in controls and previously medicated patients.

Adolescent↗
PubMed1998

Reduced prefrontal and increased subcortical brain functioning assessed using positron emission tomography in predatory and affective murderers.

There appear to be no brain imaging studies investigating which brain mechanisms subserve affective, impulsive violence versus planned, predatory violence. It was hypothesized that affectively violent offenders would have lower prefrontal activity, higher subcortical activity, and reduced prefrontal/subcortical ratios relative to controls, while predatory violent offenders would show relatively normal brain functioning. Glucose metabolism was assessed using positron emission tomography in 41 comparisons, 15 predatory murderers, and nine affective murderers in left and right hemisphere prefrontal (medial and lateral) and subcortical (amygdala, midbrain, hippocampus, and thalamus) regions. Affective murderers relative to comparisons had lower left and right prefrontal functioning, higher right hemisphere subcortical functioning, and lower right hemisphere prefrontal/subcortical ratios. In contrast, predatory murderers had prefrontal functioning that was more equivalent to comparisons, while also having excessively high right subcortical activity. Results support the hypothesis that emotional, unplanned impulsive murderers are less able to regulate and control aggressive impulses generated from subcortical structures due to deficient prefrontal regulation. It is hypothesized that excessive subcortical activity predisposes to aggressive behaviour, but that while predatory murderers have sufficiently good prefrontal functioning to regulate these aggressive impulses, the affective murderers lack such prefrontal control over emotion regulation.

Affect↗
PubMed1998

Positron emission tomography studies of abnormal glucose metabolism in schizophrenia.

Schizophrenia, a devastating disease characterized by a combination of various types of disturbed behaviors, thoughts, and feelings, may likewise be heterogeneous in etiology. Recent advances in neuroscience and psychopharmacology have suggested a wide array of competing mechanisms that may be involved in schizophrenia, including but not limited to deficits in one or more neurotransmitters and second messenger systems (e.g., dopamine, serotonin, gamma-aminobutyric acid, glutamate, and noradrenaline), neurodevelopmental defects in brain circuitry, and viral infection. Psychiatric genetic studies indicate that schizophrenia is a disorder with multifactorial inheritance. Since cerebral metabolic activity reflects regional brain work for all neurotransmitter systems, imaging metabolism directly with fluorodeoxyglucose and indirectly with blood flow and hemoglobin oxygen saturation can provide information about the functional neuroanatomy of a deficit in individual patients and allow patients to be grouped into more homogeneous subgroups for intensive study. This review summarizes metabolic imaging studies in schizophrenia over the past decade.

Antipsychotic Agents↗
PubMed1998

Greater metabolic rate decreases in hippocampal formation and proisocortex than in neocortex in Alzheimer's disease.

Neuropathological studies of Alzheimer's disease (AD) have found pathological changes in some cytoarchitectural regions and relative sparing in others. Positron emission tomography (PET) studies have also shown selective decreases in glucose metabolic rates but have generally focused on whole brain lobes or geometrically derived regions of interest. In this report, a template of Brodmann areas, derived from a whole brain histological section atlas, was used to analyze PET findings from 34 AD patients and 16 control subjects matched for age, sex, and educational level. AD patients had lowest glucose metabolic rates in limbic areas of the temporal lobe and other proisocortical areas higher rates in frontal lobe and unimodal association areas, and relative sparing of parietal/occipital lobes and motor/sensory cortices. Analysis of variance revealed larger effect sizes when AD and control subjects were compared on metabolic rate for cortical type than for lobe. These findings, which parallel neuropathological studies of regional distribution of neurofibrillary tangles in AD, suggest that vulnerability is greatest in cortical areas that are in closer synaptic contact with limbic areas.

Aged↗
PubMed1998

Prefrontal cortex glucose metabolism and startle eyeblink modification abnormalities in unmedicated schizophrenia patients.

Attentional modulation of the startle reflex was studied in 16 unmedicated schizophrenia patients and 15 control individuals during the 18F-2-deoxyglucose uptake period for positron emission tomography. In a task involving attended, ignored, and novel tones that served as prepulses, control individuals showed greater prepulse inhibition (PPI) at 120 ms and greater prepulse facilitation at 4,500 ms during attended than during ignored prepulses; the amount of PPI and facilitation during novel prepulses was intermediate. In contrast, patients failed to show differential PPI at 120 ms and tended to show greater facilitation at 4,500 ms during novel prepulses. For control individuals, greater PPI was associated with higher relative metabolic activity rates in prefrontal (Brodmann Areas 8, 9, and 10 bilaterally) and lower in visual cortex. Patients showed this relationship only for Area 10 on the left. Patients also had low metabolism in superior, middle, and inferior prefrontal cortex. Consistent with animal models, our results demonstrate the importance of the functional integrity of prefrontal cortex to PPI modulation.

Acoustic Stimulation↗