Biomedical subjects

E M Reiman

Publications and source records attributed to E M Reiman.

47 records · Page 3Linked to original sources

PubMed1989

Neuroanatomical correlates of a lactate-induced anxiety attack.

Positron emission tomographic measurements of regional blood flow were used to assess local neuronal activity in patients with panic disorder and in normal control subjects before and during the infusion of sodium lactate. A new technique for the analysis of positron emission tomographic data was employed to identify significant changes in regional blood flow associated with lactate infusion in the panicking patients, nonpanicking patients, and controls. Lactate-induced panic was associated with significant blood flow increases bilaterally in the temporal poles; bilaterally in insular cortex, claustrum, or lateral putamen; bilaterally in or near the superior colliculus; and in or near the left anterior cerebellar vermis. Lactate infusion was not associated with significant changes in regional blood flow in the nonpanicking patients or control subjects. Thus, the identified regions seemed to be involved in an anxiety attack.

Adult↗

PubMed1989

Left striato-pallidal hyperactivity in schizophrenia. Part II: Phenomenology and thought disorder.

Our previous paper summarized abundant evidence that schizophrenic patients show forms of sensory and motor hemineglect compatible with a left striato-pallidal hyperactivity model of schizophrenia. In this paper we discuss how the model may also account for some of the cognitive and phenomenological aspects of this disorder. Hemineglect can be associated with pallidal hyperactivity through its mediation of the anterior attention system of the frontal lobe. We postulate that this same attentional deficit can also affect higher functions such as the control of language and thought by internal motivations. Many symptoms of schizophrenia can be explained as a form of hemineglect of these higher functions.

Arousal↗

PubMed1989

Hyperactivity of the left striato-pallidal projection. Part I: Lower level theory.

We have observed increased relative blood flow to the left globus pallidus and evidence for subtle forms of right-sided hemineglect in neuroleptic-naive schizophrenic patients. These findings occur in animals following certain lesions such as unilateral destruction of midbrain dopaminergic neurons, and are presumed to be due to left striato-pallidal hyperactivity. A survey of the literature reveals many similarities between animals with unilateral dopaminergic denervation and schizophrenic patients. It has previously been suggested that available evidence does not preclude the possibility that schizophrenic patients have something like a dopaminergic deficiency. Other studies demonstrate that neuroleptics reverse asymmetries in indices of dopamine turnover. A model based upon dopaminergic hemideficiency is outlined, and can potentially explain other abnormalities in schizophrenic patients including eye movement abnormalities and the link between temporal lobe epilepsy and psychosis. A companion article describes how this model can account for some of the phenomenological symptoms of psychosis.

Arousal↗

PubMed1988

Enhanced detection of focal brain responses using intersubject averaging and change-distribution analysis of subtracted PET images.

Intersubject averaging and change-distribution analysis of subtracted positron emission tomographic (PET) images were developed and tested. The purpose of these techniques is to increase the sensitivity and objectivity of functional mapping of the human brain with PET. To permit image averaging, all primary tomographic images were converted to anatomically standardized three-dimensional images using stereotactic anatomical localization and interslice interpolation. Image noise, measured in control-minus-control subtractions, was strongly suppressed by averaging. Signal-to-noise ratio, measured in stimulus-minus-control subtractions (hand vibration minus eyes-closed rest), rose steadily with averaging, confirming the accuracy of our method of anatomical standardization. Distribution analysis of CBF change images (outlier detection by gamma-2 statistic) was assessed as an omnibus test for state-dependent changes in regional neuronal activity. Sensitivity in detecting the somatosensory response rose steadily with averaging, increasing from 50% in individual images to 100% when three or more images were averaged. Specificity was 100% at all averaging levels. Although described here as a technique for functional brain mapping with H2(15O) CBF images, image averaging, and change-distribution analysis are more generally applicable techniques, not limited to a single purpose or tracer.

Adolescent↗

PubMed1988

The quest to establish the neural substrates of anxiety.

Recent developments in neuroanatomic, lesion and stimulation, and functional brain mapping studies offer great promise in the search for the neural substrates of anxiety. Animal studies have provided important clues about the neural pathways that underlie certain aspects of the evaluative and expressive components of anxiety. As a brain-imaging technique that safely permits the study of the living human brain, positron emission tomography is likely to provide additional information about the neural structures that underlie the evaluation, expression, and experience of anxiety in each of its normal and pathologic forms. The quest to establish the neural substrates of anxiety has two parts: identification of the elementary psychophysiologic operations that define anxiety and identification of the precise neural pathways that underlie each of these operations. To paraphrase an investigator who is involved in this quest, the challenge and charm of this field are that studies of both the mind and the brain are required.

Animals↗

PubMed1987

Left globus pallidus abnormality in never-medicated patients with schizophrenia.

Schizophrenia is a severe psychiatric disorder characterized by onset in young adulthood, the occurrence of hallucinations and delusions, and the development of enduring psychosocial disability. The pathophysiology of this disorder remains unknown. Studies of cerebral blood flow and metabolism designed to identify brain abnormalities in schizophrenia have been limited by inadequate methods of anatomical localization and the possibility of persistent medication effects. We have now used positron emission tomography and a validated method of anatomical localization in an attempt to identify abnormalities of regional cerebral blood flow in newly diagnosed never-medicated patients with schizophrenia. An exploratory study of 5 patients and 10 normal control subjects identified abnormally high blood flow in the left globus pallidus of patients with schizophrenia. A replication study of 5 additional patients and 10 additional control subjects confirmed this finding. No other abnormalities were found.

Adolescent↗

PubMed1987

The study of panic disorder using positron emission tomography.

Positron emission tomography (PET) is a brain imaging technique which safely provides quantitative, regional measurements of biochemical and physiological processes. Because of its capabilities, PET is well suited to the study of psychiatric disorders. Among psychiatric disorders, panic disorder is especially well suited for study. Since anxiety attacks can be precipitated by biological agents, blocked by anti-panic medications, and studied in a laboratory setting, PET can be used to investigate the elements necessary for the generation and treatment of anxiety attacks. Recently, we employed PET to identify several abnormalities in a sub-group of patients with panic disorder. Patients with panic disorder who were vulnerable to lactate-induced anxiety attacks had abnormal hemispheric asymmetries of parahippocampal blood flow, blood volume, and oxygen metabolism; abnormally high whole brain metabolism; and abnormal susceptibility to episodic hyperventilation. This article reviews the current concepts of panic disorder; it provides an introduction to the components, capabilities and limitations of PET; and it describes the strategy now being employed at Washington University to investigate the neurobiology of panic disorder.

Anxiety Disorders↗

PubMed1986

The application of positron emission tomography to the study of panic disorder.

Positron emission tomography was used to study eight patients with panic disorder who were vulnerable to lactate-induced panic, eight patients with panic disorder who were not vulnerable to lactate-induced panic, and 25 normal control subjects. Patients who were vulnerable to lactate-induced panic had several abnormalities in the resting, nonpanic state: an abnormal hemispheric asymmetry of parahippocampal blood flow, blood volume, and oxygen metabolism; abnormally high whole brain metabolism; and abnormal susceptibility to episodic hyperventilation. A hypothetical model for the neurobiology of panic disorder, involving the abnormal parahippocampal region and its afferent and efferent connections, is proposed.

Adult↗

PubMedDate not supplied

Behavior and brain uptake of fluorodeoxyglucose in mature and aged C57BL/6 mice.

This paper describes regional brain energy metabolism, sensorimotor, and memory functions in mature (12 months) and old (24 months) C57BL/6 mice. Male mice were tested across a variety of sensorimotor procedures and in the Morris water maze before evaluating brain uptake of fluorodeoxyglucose (FDG) in the resting state. Mature mice outperformed older mice during the difficult sensorimotor and memory tasks, but not the easier tasks. This suggested that the greater sensorimotor and memory demands of a task compromised the performance of the older mice. This conclusion was consistent with the relative FDG uptake decreases found in regions mediating sensorimotor coordination (vestibular, cerebellar, ventral thalamic regions) and some limbic regions linked to memory (mammillary body, posterior cingulate, and piriform cortices). The inferior colliculus and flocculus had the greatest metabolism in mature mice, as shown by resting FDG uptake, and these regions showed the most marked hypometabolism in the older mice. The data also showed that the neurobehavioral correlative pattern in older mice was modified. In conclusion, brain regions with higher energy metabolism, and the behaviors to which they are related, were affected most greatly by aging in C57BL/6 mice-suggesting that these areas are more metabolically vulnerable to aging effects.

Aging↗

PubMedDate not supplied

A focal brain abnormality in panic disorder, a severe form of anxiety.

Panic disorder is characterized by recurrent anxiety attacks in the absence of a frightening stimulus. It is a common disorder, affecting 2-5% of the general population and 10-14% of patients seen in cardiology practice. Infusion of sodium (DL)lactate precipitates an anxiety attack in most persons with this disorder but rarely does so in normal controls, suggesting a neurobiological basis for the problem. Despite this observation, the pathophysiology of panic disorder remains unknown. We have now used positron emission tomography to measure cerebral blood flow (CBF) in patients with panic disorder in the absence of a panic attack. Analysis of CBF in regions thought to mediate symptoms of panic, anxiety and vigilance reveals a significant (P less than 0.005) abnormal asymmetry of CBF (left less than right) located in a region of the parahippocampal gyrus. This asymmetry was present in seven patients with panic disorder and a positive response to lactate infusion but was absent in six normal controls and in three patients with panic disorder associated with a negative response to lactate. We believe this to be the first study to identify a discrete brain abnormality in patients with this severe form of anxiety.

Anxiety Disorders↗

PubMedDate not supplied

Neuroanatomical correlates of implicit and explicit memory for structurally possible and impossible visual objects.

Implicit memory refers to nonconscious retrieval of past experience demonstrated by facilitation in test performance on tasks that do not require intentional recollection of previous experiences. Explicit memory, in contrast, refers to the conscious retrieval of prior information, as demonstrated during standard recall and recognition tasks. In this experiment, positron emission tomographic (PET) measurements of regional cerebral blood flow (CBF), a marker of local neuronal activity, were used to identify and contrast brain regions that participate in the perception, implicit memory, and explicit memory for structurally possible and impossible visual objects. Ten CBF images were acquired in 16 normal women as they made possible/impossible and old/new recognition decisions about previously studied (old) and nonstudied (new) structurally possible and impossible objects. As reported previously, object decisions for familiar possible objects were associated with increased CBF in the vicinity of the left inferior temporal and fusiform gyri and recognition memory for familiar possible objects was associated with increased CBF in the vicinity of the right hippocampus. In this report, we provide more extensive analyses of the roles of the inferior temporal cortex, the hippocampus, the parahippocampus, and the pulvinar in encoding and retrieval operations. Additionally, patterns of CBF increases and decreases provide information regarding the neural structures involved in implicit and explicit memory.

Adult↗