RESUMO
BACKGROUND: Neuroimaging research has demonstrated medial prefrontal cortex (mPFC) hyporesponsivity and amygdala hyperresponsivity to trauma-related or emotional stimuli in post-traumatic stress disorder (PTSD). Relatively few studies have examined brain responses to the recollection of stressful, but trauma-unrelated, personal events in PTSD. In the current study, we sought to determine whether regional cerebral blood flow (rCBF) abnormalities in mPFC and amygdala in PTSD could be observed during the recollection of trauma-unrelated stressful personal events. METHOD: Participants were 35 right-handed male combat veterans (MCVs) and female nurse veterans (FNVs) who served in Vietnam: 17 (seven male, 10 female) with current military-related PTSD and 18 (nine male, nine female) with no current or lifetime PTSD. We used positron emission tomography (PET) and script-driven imagery to study rCBF during the recollection of trauma-unrelated stressful versus neutral and traumatic events. RESULTS: Voxelwise tests revealed significant between-group differences for the trauma-unrelated stressful versus neutral comparison in mPFC, specifically in the anterior cingulate cortex (ACC). Functional region of interest (ROI) analyses demonstrated that this interaction in mPFC represented greater rCBF decreases in the PTSD group during trauma-unrelated stressful imagery relative to neutral imagery compared to the non-PTSD group. No differential amygdala activation was observed between groups or in either group separately. CONCLUSIONS: Veterans with PTSD, compared to those without PTSD, exhibited decreased rCBF in mPFC during mental imagery of trauma-unrelated stressful personal experiences. Functional neuroanatomical models of PTSD must account for diminished mPFC responses that extend to emotional stimuli, including stressful personal experiences that are not directly related to PTSD.
Assuntos
Córtex Pré-Frontal/irrigação sanguínea , Transtornos de Estresse Pós-Traumáticos/fisiopatologia , Estresse Psicológico/fisiopatologia , Veteranos/psicologia , Guerra do Vietnã , Idoso , Circulação Cerebrovascular/fisiologia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Tomografia por Emissão de Pósitrons , Córtex Pré-Frontal/fisiopatologia , Estados UnidosRESUMO
PURPOSE: We propose a novel approach for PET respiratory motion correction using tagged-MRI and simultaneous PET-MRI acquisitions. METHODS: We use a tagged-MRI acquisition followed by motion tracking in the phase domain to estimate the nonrigid deformation of biological tissues during breathing. In order to accurately estimate motion even in the presence of noise and susceptibility artifacts, we regularize the traditional HARP tracking strategy using a quadratic roughness penalty on neighboring displacement vectors (R-HARP). We then incorporate the motion fields estimated with R-HARP in the system matrix of an MLEM PET reconstruction algorithm formulated both for sinogram and list-mode data representations. This approach allows reconstruction of all detected coincidences in a single image while modeling the effect of motion both in the emission and the attenuation maps. At present, tagged-MRI does not allow estimation of motion in the lungs and our approach is therefore limited to motion correction in soft tissues. Since it is difficult to assess the accuracy of motion correction approaches in vivo, we evaluated the proposed approach in numerical simulations of simultaneous PET-MRI acquisitions using the NCAT phantom. We also assessed its practical feasibility in PET-MRI acquisitions of a small deformable phantom that mimics the complex deformation pattern of a lung that we imaged on a combined PET-MRI brain scanner. RESULTS: Simulations showed that the R-HARP tracking strategy accurately estimated realistic respiratory motion fields for different levels of noise in the tagged-MRI simulation. In simulations of tumors exhibiting increased uptake, contrast estimation was 20% more accurate with motion correction than without. Signal-to-noise ratio (SNR) was more than 100% greater when performing motion-corrected reconstruction which included all counts, compared to when reconstructing only coincidences detected in the first of eight gated frames. These results were confirmed in our proof-of-principle PET-MRI acquisitions, indicating that our motion correction strategy is accurate, practically feasible, and is therefore ready to be tested in vivo. CONCLUSIONS: This work shows that PET motion correction using motion fields measured with tagged-MRI in simultaneous PET-MRI acquisitions can be made practical for clinical application and that doing so has the potential to remove motion blur in whole-body PET studies of the torso.
Assuntos
Abdome/diagnóstico por imagem , Processamento de Imagem Assistida por Computador/métodos , Imageamento por Ressonância Magnética/métodos , Movimento , Tomografia por Emissão de Pósitrons/métodos , Algoritmos , Encéfalo/diagnóstico por imagem , Pulmão/fisiologia , Imagens de Fantasmas , Respiração , Espalhamento de Radiação , Fatores de TempoRESUMO
Visual imagery is used in a wide range of mental activities, ranging from memory to reasoning, and also plays a role in perception proper. The contribution of early visual cortex, specifically Area 17, to visual mental imagery was examined by the use of two convergent techniques. In one, subjects closed their eyes during positron emission tomography (PET) while they visualized and compared properties (for example, relative length) of sets of stripes. The results showed that when people perform this task, Area 17 is activated. In the other, repetitive transcranial magnetic stimulation (rTMS) was applied to medial occipital cortex before presentation of the same task. Performance was impaired after rTMS compared with a sham control condition; similar results were obtained when the subjects performed the task by actually looking at the stimuli. In sum, the PET results showed that when patterns of stripes are visualized, Area 17 is activated, and the rTMS results showed that such activation underlies information processing.
Assuntos
Mapeamento Encefálico , Imaginação/fisiologia , Córtex Visual/fisiologia , Adulto , Humanos , Magnetismo , Masculino , Memória/fisiologia , Tomografia Computadorizada de Emissão , Córtex Visual/diagnóstico por imagem , Percepção Visual/fisiologiaRESUMO
Poor attention and impaired memory are enduring and core features of schizophrenia. These impairments have been attributed either to global cortical dysfunction or to perturbations of specific components associated with the dorsolateral prefrontal cortex (DLPFC), hippocampus and cerebellum. Here, we used positron emission tomography (PET) to dissociate activations in DLPFC and hippocampus during verbal episodic memory retrieval. We found reduced hippocampal activation during conscious recollection of studied words, but robust activation of the DLPFC during the effort to retrieve poorly encoded material in schizophrenic patients. This finding provides the first evidence of hippocampal dysfunction during episodic memory retrieval in schizophrenia.
Assuntos
Hipocampo/fisiopatologia , Rememoração Mental/fisiologia , Recrutamento Neurofisiológico/fisiologia , Esquizofrenia/fisiopatologia , Adulto , Encéfalo/diagnóstico por imagem , Circulação Cerebrovascular/fisiologia , Humanos , Masculino , Pessoa de Meia-Idade , Psicologia do Esquizofrênico , Tomografia Computadorizada de Emissão , Comportamento Verbal/fisiologiaRESUMO
OBJECTIVES: This study tested the hypothesis that nonviable myocardium can be identified by quantitative measurements of regional myocardial blood flow obtained using positron emission tomography in conjunction with a mathematical model of nitrogen-13 (N-13) ammonia tracer kinetics. BACKGROUND: Under steady state basal conditions there is a minimal level of blood flow required to sustain myocardial viability. Therefore, the hypothesis predicts that regions with flow below a certain threshold are likely to be composed primarily of scar. METHODS: Studies were conducted in 26 patients with chronic myocardial infarction. Positron emission tomographic measurements of basal regional myocardial blood flow (N-13 ammonia) and fluorine-18 (F-18) fluorodeoxyglucose uptake were made and correlated with information about coronary anatomy and regional wall motion to assess myocardial viability. RESULTS: In patients with chronic myocardial infarction, normal zone blood flow (0.81 +/- 0.32 ml/min per g [mean +/- SD]) was greater (p < 0.02) than that of border zones (0.59 +/- 0.29 ml/min per g), which in turn exceeded (p < 0.001) that of infarct zone flow (0.27 +/- 0.17 ml/min per g). Good correlation was noted between relative F-18 fluorodeoxyglucose uptake and relative regional myocardial blood flow in all zones (r = 0.63, p < 0.001). Mismatch between blood flow and F-18 fluorodeoxyglucose uptake, with a single exception, was not observed in any segment with blood flow < 0.25 ml/min per g. All dyskinetic segments (n = 5) also had blood flow < 0.25 ml/min per g. In contrast, 43 of 45 myocardial segments (23 patients) with normal contraction or only mild hypokinesia had flow > or = 0.39 ml/min per g (average flow 0.78 +/- 0.35 ml/min per g). CONCLUSIONS: In patients with chronic myocardial infarction, myocardial viability is unlikely when basal regional myocardial blood flow is < 0.25 ml/min per g. Average basal flow in segments with normal or nearly normal wall motion is 0.78 +/- 0.35 ml/min per g. Thus, positron emission tomographic measurement of regional myocardial blood flow is helpful in identifying nonviable myocardium in these patients.
Assuntos
Circulação Coronária , Coração/diagnóstico por imagem , Coração/fisiopatologia , Infarto do Miocárdio/fisiopatologia , Tomografia Computadorizada de Emissão , Adulto , Idoso , Animais , Doença Crônica , Feminino , Glucose/metabolismo , Humanos , Masculino , Pessoa de Meia-Idade , Contração Miocárdica/fisiologia , Infarto do Miocárdio/diagnóstico por imagem , Infarto do Miocárdio/patologia , Miocárdio/metabolismo , Miocárdio/patologia , Radioisótopos de Nitrogênio , Fluxo Sanguíneo Regional/fisiologia , SuínosRESUMO
OBJECTIVES: We tested the hypothesis in patients (n = 24) with ischemic heart disease that chronic contractile dysfunction occurs in myocardial regions with true reduction in rest blood flow. BACKGROUND: Whether viable myocardial regions with chronic contractile dysfunction have true reduction in rest myocardial blood flow is controversial. METHODS: Positron emission tomography (PET) 13N-ammonia was used to measure myocardial blood flow in combination with 18F-fluorodeoxyglucose (18FDG) to assess myocardial viability. Viability also was assessed by dobutamine echo and recovery of function after coronary artery bypass grafting (CABG). Segments (n = 252) were selected based on PET measured reduced resting blood flow and rest asynergy on echo. RESULTS: Regional myocardial viability was present in 20 of 23 patients by PET, 13 of 23 by dobutamine echo and 10 of 11 by postrevascularization criteria. Rest blood flow in normal regions was 1.14+/-0.52 ml/min/g and by definition exceeded (p < 0.005) that in both viable (0.48+/-0.15; n = 8 patients) and nonviable (0.45+/-0.14; n = 8 patients) regions (post-CABG criteria), which did not differ. Correction of rest myocardial blood flow in viable asynergic segments, only, for fibrosis and incomplete tracer recovery raised the level to 0.67+/-0.21 (p < 0.005 vs. normal). Finally, evidence of both stunning (rest asynergy with normal flow) and hibernation was present in 15 of 23 (65%) patients. CONCLUSIONS: Reduced rest blood flow in viable myocardial regions with chronic asynergy is common and cannot be accounted for by partial volume effect. Thus, hypotheses concerning physiologic mechanisms underlying chronic contractile dysfunction should consider the role played by chronic reduction of basal myocardial blood flow.
Assuntos
Circulação Coronária , Contração Miocárdica , Isquemia Miocárdica/fisiopatologia , Adulto , Idoso , Idoso de 80 Anos ou mais , Cardiotônicos , Dobutamina , Feminino , Fluordesoxiglucose F18 , Hemodinâmica , Humanos , Processamento de Imagem Assistida por Computador , Masculino , Pessoa de Meia-Idade , Isquemia Miocárdica/diagnóstico por imagem , Compostos Radiofarmacêuticos , Tomografia Computadorizada de Emissão , UltrassonografiaRESUMO
BACKGROUND: Relative regional cerebral blood flow (rCBF) changes were measured in Vietnam combat veterans with and without posttraumatic stress disorder (PTSD) during exposure to combat-related stimuli. METHODS: Positron emission tomography was used to measure rCBF in 7 combat veterans with PTSD (PTSD group) and 7 healthy combat veterans (control group) who viewed and generated visual mental images of neutral, negative, and combat-related pictures. RESULTS: Unlike control subjects, subjects with PTSD had increased rCBF in ventral anterior cingulate gyrus and right amygdala when generating mental images of combat-related pictures; when viewing combat pictures, subjects with PTSD showed decreased rCBF in Broca's area. CONCLUSIONS: Results suggest that ventral anterior cingulate gyrus and right amygdala play a role in the response of combat veterans with PTSD to mental images of combat-related scenes. Reexperiencing phenomena of PTSD, which often involve emotional visual mental imagery, may be likewise associated with increased rCBF in these regions.
Assuntos
Circulação Cerebrovascular , Imaginação , Transtornos de Estresse Pós-Traumáticos/diagnóstico por imagem , Transtornos de Estresse Pós-Traumáticos/psicologia , Tomografia Computadorizada de Emissão , Percepção Visual , Tonsila do Cerebelo/irrigação sanguínea , Tonsila do Cerebelo/diagnóstico por imagem , Tonsila do Cerebelo/fisiologia , Lateralidade Funcional/fisiologia , Giro do Cíngulo/irrigação sanguínea , Giro do Cíngulo/diagnóstico por imagem , Giro do Cíngulo/fisiologia , Humanos , Imaginação/fisiologia , Masculino , Pessoa de Meia-Idade , Fluxo Sanguíneo Regional , Percepção Visual/fisiologia , GuerraRESUMO
BACKGROUND: The study was designed to determine the mediating neuroanatomy of obsessive-compulsive disorder (OCD). METHODS: The short half-life tracer oxygen 15-labeled carbon dioxide was used to allow for repeated positron emission tomographic determinations of regional cerebral blood flow on each of eight patients with OCD during a resting and a provoked (symptomatic) state. RESULTS: Individually tailored provocative stimuli were successful in provoking OCD symptoms, in comparison with paired innocuous stimuli, as measured by self-report on OCD analogue scales (P = .002). Omnibus subtraction images demonstrated a statistically significant increase in relative regional cerebral blood flow during the OCD symptomatic state vs the resting state in right caudate nucleus (P < .006), left anterior cingulate cortex (P < .045), and bilateral orbitofrontal cortex (P < .008); increases in the left thalamus approached but did not reach statistical significance (P = .07). CONCLUSIONS: These findings are consistent with results of previous functional neuroimaging studies and contemporary neurocircuitry models of OCD. The data further implicate orbitofrontal cortex, caudate nucleus, and anterior cingulate cortex in the pathophysiology of OCD and in mediating OCD symptoms.
Assuntos
Encéfalo/diagnóstico por imagem , Dióxido de Carbono , Circulação Cerebrovascular , Transtorno Obsessivo-Compulsivo/diagnóstico por imagem , Radioisótopos de Oxigênio , Tomografia Computadorizada de Emissão , Adulto , Encéfalo/fisiopatologia , Núcleo Caudado/irrigação sanguínea , Feminino , Lobo Frontal/irrigação sanguínea , Giro do Cíngulo/irrigação sanguínea , Humanos , Masculino , Transtorno Obsessivo-Compulsivo/diagnóstico , Transtorno Obsessivo-Compulsivo/fisiopatologia , Tálamo/irrigação sanguíneaRESUMO
BACKGROUND: Neuroimaging studies have provided evidence of abnormal frontal and temporal lobe function in schizophrenia. Frontal cortex abnormalities have been associated with negative symptoms and temporal lobe abnormalities with positive symptoms. The deficit and nondeficit forms of schizophrenia were predicted to differ in prefrontal cortical activity, but not in medial temporal lobe activity. METHODS: Regional cerebral blood flow was studied using oxygen 15 positron emission tomography during 3 different memory retrieval conditions in 8 control subjects, 8 patients with the deficit syndrome, and 8 patients without the deficit syndrome. Behavioral and positron emission tomography data were analyzed using a mixed-effects model to test for population differences. RESULTS: In all memory conditions, frontal cortex activity was higher in patients without the deficit syndrome than in patients with the deficit syndrome. During the attempt to retrieve poorly encoded words, patients without the deficit syndrome recruited the left frontal cortex to a significantly greater degree than did patients with the deficit syndrome. The 2 schizophrenia subtypes did not differ in the activity or recruitment of the hippocampus during memory retrieval. CONCLUSION: Frontal cortex function during memory retrieval is differentially impaired in deficit and nondeficit schizophrenia, whereas hippocampal recruitment deficits are not significantly different between the 2 schizophrenia groups.
Assuntos
Lobo Frontal/fisiopatologia , Memória/fisiologia , Esquizofrenia/diagnóstico , Psicologia do Esquizofrênico , Tomografia Computadorizada de Emissão , Adulto , Diagnóstico Diferencial , Lobo Frontal/irrigação sanguínea , Lobo Frontal/diagnóstico por imagem , Lateralidade Funcional/fisiologia , Hipocampo/irrigação sanguínea , Hipocampo/diagnóstico por imagem , Hipocampo/fisiopatologia , Humanos , Masculino , Transtornos da Memória/diagnóstico por imagem , Transtornos da Memória/fisiopatologia , Rememoração Mental/fisiologia , Radioisótopos de Oxigênio , Córtex Pré-Frontal/irrigação sanguínea , Córtex Pré-Frontal/diagnóstico por imagem , Córtex Pré-Frontal/fisiopatologia , Fluxo Sanguíneo Regional , Esquizofrenia/diagnóstico por imagem , Esquizofrenia/fisiopatologia , Lobo Temporal/irrigação sanguínea , Lobo Temporal/diagnóstico por imagem , Lobo Temporal/fisiopatologiaRESUMO
BACKGROUND: Previous studies have used symptom provocation and positron emission tomography to delineate the brain systems that mediate various anxiety states. Using an analogous approach, the goal of this study was to measure regional cerebral blood flow changes associated with posttraumatic stress disorder (PTSD) symptoms. METHODS: Eight patients with PTSD, screened as physiologically responsive to a script-driven imagery symptom provocation paradigm, were exposed sequentially to audiotaped traumatic and neutral scripts in conjunction with positron emission tomography. Heart rate and subjective measures of emotional state were obtained for each condition. Statistical mapping techniques were used to determine locations of significant brain activation. RESULTS: Increases in normalized blood flow were found for the traumatic as compared with control conditions in right-sided limbic, paralimbic, and visual areas; decreases were found in left inferior frontal and middle temporal cortex. CONCLUSIONS: The results suggest that emotions associated with the PTSD symptomatic state are mediated by the limbic and paralimbic systems within the right hemisphere. Activation of visual cortex may correspond to the visual component of PTSD reexperiencing phenomena.
Assuntos
Encéfalo/fisiologia , Circulação Cerebrovascular , Imaginação/fisiologia , Memória/fisiologia , Transtornos de Estresse Pós-Traumáticos/diagnóstico , Tomografia Computadorizada de Emissão , Adulto , Encéfalo/diagnóstico por imagem , Emoções/fisiologia , Feminino , Lobo Frontal/irrigação sanguínea , Lobo Frontal/fisiologia , Lateralidade Funcional/fisiologia , Frequência Cardíaca/fisiologia , Humanos , Acontecimentos que Mudam a Vida , Sistema Límbico/irrigação sanguínea , Sistema Límbico/fisiologia , Masculino , Pessoa de Meia-Idade , Fluxo Sanguíneo Regional/fisiologia , Transtornos de Estresse Pós-Traumáticos/diagnóstico por imagem , Transtornos de Estresse Pós-Traumáticos/psicologia , Córtex Visual/irrigação sanguínea , Córtex Visual/fisiologiaRESUMO
BACKGROUND: The goal of this study was to determine the mediating neuroanatomy of simple phobic symptoms. METHODS: Positron emission tomography and oxygen 15 were used to measure normalized regional cerebral blood flow in seven subjects with simple phobia during control and provoked states. Stereotactic transformation and statistical parametric mapping techniques were employed to determine the locations of significant activation. RESULTS: Statistical parametric maps demonstrated significant increases in normalized regional blood flow for the symptomatic state compared with the control state in the anterior cingulate cortex, the insular cortex, the anterior temporal cortex, the somatosensory cortex, the posterior medial orbitofrontal cortex, and the thalamus. CONCLUSIONS: The results suggest that anxiety associated with the simple phobic symptomatic state is mediated by paralimbic structures. Moreover, activation of somatosensory cortex may reflect tactile imagery as one component of the phobic symptomatic condition.
Assuntos
Encéfalo/diagnóstico por imagem , Circulação Cerebrovascular , Transtornos Fóbicos/diagnóstico por imagem , Tomografia Computadorizada de Emissão , Adulto , Córtex Cerebral/irrigação sanguínea , Córtex Cerebral/diagnóstico por imagem , Feminino , Giro do Cíngulo/irrigação sanguínea , Giro do Cíngulo/diagnóstico por imagem , Humanos , Masculino , Pessoa de Meia-Idade , Radioisótopos de Oxigênio , Transtornos Fóbicos/diagnóstico , Transtornos Fóbicos/psicologia , Córtex Somatossensorial/irrigação sanguínea , Córtex Somatossensorial/diagnóstico por imagem , Tálamo/irrigação sanguínea , Tálamo/diagnóstico por imagem , Tato/fisiologiaRESUMO
The sequence and magnitude of acute changes in renal blood flow following administration of captopril were determined in a canine model of acute unilateral renal artery stenosis using rubidium-82 and positron emission tomography. Data were recorded in each of nine dogs under three conditions: 1) during a baseline control interval, 2) during renal artery stenosis, and 3) during stenosis with intravenous injection of captopril (1.2 mg/kg). Mean arterial blood pressure was 108 +/- 12 mm Hg at control, increased significantly to 125 +/- 13 mm Hg (p less than 0.01) during stenosis, and decreased to 98 +/- 13 mm/Hg (p less than 0.01) after captopril infusion. Mean renal blood flow was calculated using a steady state single compartment model from the images produced by positron emission tomography. The estimated flow to the affected kidney was 3.37 +/- 1.48 ml/min/g at control, 0.86 +/- 0.62 ml/min/g during stenosis (p less than 0.01), and 0.64 +/- 0.57 ml/min/g after captopril administration (p = NS compared with precaptopril value). The estimated flow to the contralateral kidney was minimally reduced from a baseline of 3.84 +/- 0.95 to 3.24 +/- 1.13 ml/min/g (p = NS) during stenosis and increased after captopril infusion (4.08 +/- 0.94 ml/min/g; p = 0.01). These data suggest that repetitive imaging with positron emission tomography can be used to delineate acute changes in renal perfusion following captopril administration.
Assuntos
Captopril/farmacologia , Rim/diagnóstico por imagem , Obstrução da Artéria Renal/diagnóstico por imagem , Circulação Renal/efeitos dos fármacos , Sistema Renina-Angiotensina/efeitos dos fármacos , Radioisótopos de Rubídio , Tomografia Computadorizada de Emissão , Animais , Cães , Obstrução da Artéria Renal/fisiopatologiaRESUMO
Previous neuroimaging research has contributed insights regarding the neural substrates of specific psychiatric disorders. The purpose of this study was to determine the shared mediating neuroanatomy of anxiety symptoms across three different anxiety disorders. Data were pooled from 23 right-handed adult outpatients meeting criteria for obsessive-compulsive disorder, simple phobia, or posttraumatic stress disorder. Relative regional cerebral blood flow (rCBF) was measured using positron emission tomography in the context of symptom provocation paradigms. Symptom severity was measured via self-reports. The analysis of pooled imaging data indicated activation in right inferior frontal cortex, right posterior medial orbitofrontal cortex, bilateral insular cortex, bilateral lenticulate nuclei, and bilateral brain stem foci during the symptomatic versus control conditions. A positive correlation was found between rCBF at one brain stem locus and subjective anxiety scores (r = .744, p < .001). These findings suggest that elements of the paralimbic belt together with right inferior frontal cortex and subcortical nuclei mediate symptoms across different anxiety disorders. In addition, activation at one brain stem locus appears to be associated with the subjective severity of anxiety. Further studies are warranted to determine whether these same brain systems mediate normal anxiety states as well.
Assuntos
Transtornos de Ansiedade/patologia , Circulação Cerebrovascular/fisiologia , Adulto , Transtornos de Ansiedade/fisiopatologia , Transtornos de Ansiedade/psicologia , Feminino , Humanos , Processamento de Imagem Assistida por Computador , Sistema Límbico/irrigação sanguínea , Masculino , Pessoa de Meia-Idade , Transtorno Obsessivo-Compulsivo/fisiopatologia , Tomografia Computadorizada de EmissãoRESUMO
BACKGROUND: Several recent neuroimaging studies have examined the neuroanatomical correlates of normal emotional states, such as happiness, sadness, fear, anger, anxiety, and disgust; however, no previous study has examined the emotional state of guilt. METHODS: In the current study, we used positron emission tomography and the script-driven imagery paradigm to study regional cerebral blood flow (rCBF) during the transient emotional experience of guilt in eight healthy male participants. In the Guilt condition, participants recalled and imagined participating in a personal event involving the most guilt they had ever experienced. In the Neutral condition, participants recalled and imagined participating in an emotionally neutral personal event. RESULTS: In the Guilt versus Neutral comparison, rCBF increases occurred in anterior paralimbic regions of the brain: bilateral anterior temporal poles, anterior cingulate gyrus, and left anterior insular cortex/inferior frontal gyrus. CONCLUSIONS: These results, along with those of previous studies, are consistent with the notion that anterior paralimbic regions of the brain mediate negative emotional states in healthy individuals.
Assuntos
Córtex Cerebral/fisiologia , Circulação Cerebrovascular , Culpa , Tomografia Computadorizada de Emissão , Adulto , Animais , Córtex Cerebral/irrigação sanguínea , Córtex Cerebral/diagnóstico por imagem , Circulação Cerebrovascular/fisiologia , Emoções/fisiologia , Giro do Cíngulo/fisiologia , Humanos , Imaginação , Masculino , Valores de ReferênciaRESUMO
BACKGROUND: Many patients with schizophrenia demonstrate memory deficits. We studied patterns of brain activity during episodic recognition of new and previously seen three-dimensional objects. METHODS: We used (15)O positron emission tomography to study regional cerebral blood flow in eight normal subjects and nine patients with schizophrenia during a visual object recognition task. RESULTS: In comparison with control subjects, patients with schizophrenia showed less regional cerebral blood flow increases in the pulvinar region of the right thalamus and the right prefrontal cortex during the recognition of new objects and significantly greater left prefrontal cortex regional cerebral blood flow increases during the recognition of previously seen objects. Patients with schizophrenia exhibited alarm rates to new objects similar to those of control subjects, but significantly lower recognition rates for previously seen objects. CONCLUSIONS: Schizophrenia is associated with attenuated right thalamic and right prefrontal activation during the recognition of novel visual stimuli and with increased left prefrontal cortical activation during impaired episodic recognition of previously seen visual stimuli. This study provides further evidence for abnormal thalamic and prefrontal cortex function in schizophrenia.
Assuntos
Rememoração Mental/fisiologia , Consumo de Oxigênio/fisiologia , Reconhecimento Visual de Modelos/fisiologia , Córtex Pré-Frontal/irrigação sanguínea , Esquizofrenia/fisiopatologia , Tálamo/irrigação sanguínea , Tomografia Computadorizada de Emissão , Adulto , Mapeamento Encefálico , Doença Crônica , Dominância Cerebral/fisiologia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Córtex Pré-Frontal/diagnóstico por imagem , Fluxo Sanguíneo Regional/fisiologia , Esquizofrenia/diagnóstico por imagem , Transmissão Sináptica/fisiologia , Tálamo/diagnóstico por imagemRESUMO
BACKGROUND: Abnormalities of smooth pursuit eye movements occur commonly in schizophrenia, but the pathophysiological significance of these abnormalities is unknown. To address this, the authors conducted a pilot study in which we examined differences in regional cerebral activation using positron-emission tomography (PET) in normal volunteers as they performed two types of eye movements. METHODS: Cerebral activation in 10 normal volunteers was studied using C15O2 PET while subjects tracked a visual target using smooth pursuit and saccadic eye movements. A left-hand movement comparison task provided a physiologic landmark for verification of the location of the frontal eye fields (FEFs). RESULTS: Subjects exhibited FEF activation during both smooth pursuit and saccadic eye movements, which was greater in the latter. During smooth pursuit, subjects also exhibited increased cerebral activation in the left temporal-occipital border and left superior frontal cortex and decreased activation in medial superior parietal and insular regions relative to saccades. Other cortical visual and eye-movement brain regions also demonstrated differences in activation between the two visual tasks. CONCLUSIONS: Significant fEF activation appears to underlie both smooth pursuit and saccadic eye movements but may be more critical in the former. Dysfunction of the frontal lobe, and possibly of other areas in the pursuit pathway such as the temporo-occipital motion area, may contribute to observed eye-movement abnormalities in patients with schizophrenia.
Assuntos
Encéfalo/diagnóstico por imagem , Encéfalo/fisiologia , Acompanhamento Ocular Uniforme/fisiologia , Movimentos Sacádicos/fisiologia , Adolescente , Adulto , Radioisótopos de Carbono , Humanos , Masculino , Pessoa de Meia-Idade , Tomografia Computadorizada de EmissãoRESUMO
BACKGROUND: An understanding of the neurobiological basis of normal emotional processing is useful in formulating hypotheses regarding the pathophysiology of psychiatric illnesses. METHODS: This study examined the mediating functional neuroanatomy of anger in eight healthy men. Narrative scripts were developed from autobiographical information to induce anger and neutral states. The subjects imagined the content of the narrative scripts to induce anger during positron emission tomography to measure normalized regional cerebral blood flow (rCBF). Psychophysiologic responses and subjective ratings of emotional state were measured for each condition. Statistical parametric maps were constructed to reflect the Anger versus Neutral state contrast. RESULTS: Anger was associated with activation of the left orbitofrontal cortex, right anterior cingulate cortex affective division, and bilateral anterior temporal poles. CONCLUSIONS: These results suggest that the subjective experience of anger is associated with rCBF increases in anterior paralimbic regions of the brain.
Assuntos
Ira/fisiologia , Mapeamento Encefálico , Córtex Cerebral/fisiologia , Imaginação , Tomografia Computadorizada de Emissão , Adulto , Nível de Alerta/fisiologia , Córtex Cerebral/irrigação sanguínea , Humanos , Sistema Límbico/fisiologia , Masculino , Valores de ReferênciaRESUMO
BACKGROUND: As interventions for severe, treatment-refractory obsessive compulsive disorder (OCD), neurosurgical procedures are associated with only modest efficacy. The purpose of this study was to identify cerebral metabolic correlates as potential predictors of treatment response to anterior cingulotomy for OCD. METHODS: Clinical data were analyzed in the context of a retrospective design. Subjects were 11 patients who underwent stereotactic anterior cingulotomy for OCD. Symptom severity was measured using the Yale-Brown Obsessive Compulsive Scale (Y-BOCS) before and at approximately 6 months postoperative. Preoperative F-18-fluorodeoxyglucose-positron emission tomography (FDG-PET) data were available. Statistical parametric mapping methods were used to identify loci of significant correlation between preoperative regional cerebral metabolism and postoperative reduction in Y-BOCS scores. RESULTS: One locus within right posterior cingulate cortex was identified, where preoperative metabolism was significantly correlated with improvement in OCD symptom severity following cingulotomy. Specifically, higher preoperative rates of metabolism at that locus were associated with better postoperative outcome. CONCLUSIONS: A possible predictor of treatment response was identified for patients with OCD undergoing anterior cingulotomy. Further research, utilizing a prospective design, is indicated to determine the validity and reliability of this finding. If confirmed, an index for noninvasively predicting response to cingulotomy for OCD would be of great value.
Assuntos
Giro do Cíngulo/metabolismo , Giro do Cíngulo/cirurgia , Procedimentos Neurocirúrgicos/métodos , Transtorno Obsessivo-Compulsivo/diagnóstico , Transtorno Obsessivo-Compulsivo/cirurgia , Adulto , Feminino , Fluordesoxiglucose F18/farmacocinética , Giro do Cíngulo/anatomia & histologia , Humanos , Imageamento por Ressonância Magnética , Masculino , Pessoa de Meia-Idade , Período Pós-Operatório , Cuidados Pré-Operatórios , Compostos Radiofarmacêuticos/farmacocinética , Estudos Retrospectivos , Índice de Gravidade de Doença , Técnicas Estereotáxicas , Inquéritos e Questionários , Tomografia Computadorizada de Emissão , Resultado do TratamentoRESUMO
The goal of research with receptor ligands and PET is the characterization of an in vivo system that measures rates of association and dissociation of a ligand-receptor complex and the density of available binding sites. It has been suggested that multiple injection studies of radioactive ligand are more likely to identify model parameters than are single injection studies. Typically, at least one of the late injections is at a low specific activity (SA), so that part of the positron emission tomography (PET) curve reflects ligand dissociation. Low SA injections and the attendant reductions in receptor availability, however, may violate tracer kinetic assumptions, namely, tracer may no longer be in steady state with the total (labeled and unlabeled) ligand. Tissue response becomes critically dependent on the dose of total ligand, and an accurate description of the cold ligand in the tissue is needed to properly model the system. Two alternative models have been applied to the receptor modeling problem, which reduces to describing the time-varying number of available receptor sites. The first (Huang et al., 1989) contains only compartments for the hot ligand, 'hot only' (HO), but indirectly accounts for the action of cold ligand at receptor sites via SA. The second stipulates separate compartments for the hot and cold ligands, 'hot and cold' (HC), thus explicitly calculating available number of receptors. We examined these models and contrasted their abilities to predict PET activity, receptor availability, and SA in each tissue compartment. For multiple injection studies, the models consistently predicted different PET activities--especially following the third injection. Only for very high rate constants were the models identical for multiple injections. In one case, simulated PET curves were quite similar, but discrepancies appeared in predictions of receptor availability. The HO model predicted nonphysiological changes in the availability of receptor sites and introduced errors of 30-60% into estimates of B'max for test data. We, therefore, strongly recommend the use of the HC model for all analyses of multiple injection PET studies.
Assuntos
Ligantes , Glicoproteínas de Membrana , Proteínas de Membrana Transportadoras , Modelos Biológicos , Proteínas do Tecido Nervoso , Receptores de Superfície Celular/metabolismo , Tomografia Computadorizada de Emissão/métodos , Animais , Radioisótopos de Carbono , Proteínas de Transporte/metabolismo , Proteínas da Membrana Plasmática de Transporte de Dopamina , Humanos , Cinética , Macaca mulatta , Matemática , Receptores de Dopamina D2/metabolismo , Tomografia Computadorizada de Emissão/estatística & dados numéricosRESUMO
The analysis of positron emission tomography measurements of oxygen metabolism has been extended to provide a quantitative estimate of end-capillary PO2. The principle of this extension rests on the idea that the oxygen extraction fraction can be used to calculate the end-capillary oxygen saturation of the blood. The relation between oxygen saturation and PO2 is obtained through the oxygen dissociation curve. Our studies show that in addition to the local oxygen extraction fraction, arterial PO2 and pH values are needed in the calculation, whereas fairly large variations in factors such as PCO2, hematocrit, hemoglobin, and plasma protein levels have little or no effect. Rough estimates of end-capillary PO2 can be made using standard O2 dissociation nomograms. Blood gas and acid-base properties of blood have been known for decades, making it possible to account accurately for individual differences that may be encountered when studying patients. Measurements in nine normal subjects yielded a mean end-capillary PO2 value of 31.2 mm Hg. The ability to make a quantitative visualization of altered patterns of end-capillary PO2 provides an additional dimension to the investigation of stroke disease and tumor metabolism.