This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Using a variety of neuroimaging modalities including positron emission tomography (PET) and functional magnetic resonance imaging (fMRI), a substantial number of studies have not shown that changes in activation of the amygdala are common during the acute evocation of fear in normal human subjects (Rauch et al., 2003;Anand &Shekhar, 2003) Furthermore, several imaging studies suggest that patients with anxiety disorders such as panic disorder (PD), posttraumatic stress disorder (PTSD), and social anxiety disorder (SAD) have an altered threshold for amygdala activation compared to normal volunteers. These studies were stimulated by earlier work in rodents and non-human primates thate demonstrates that the lateral and central nuclei of the amygdala are required for both the acuisition and expression of a particular type of fear, conditioned fear, although some studies suggest some division of roles for regions of the central and extended amydala (Davis, 1992). Thus, there is now strong evidence that activation of the amygdala is a phylogentically conserved phenomenon for the experience of a key emotion, fear. The work supporting amygdalar activation in the pathogenesis of pathological fear in patients with anxiety disorder has helped investigators consider the genetic origins of anxiety disorder and likely molecular targets for the development fo novel interventions. Nevertheless, it is widely recognized that activation of the amygdale does not occur in insolation during fear responses. Furthermore, there are obvious limitations in extrapolating from animal models of conditioned fear to anxiety disorders in humans. For examle, conditioned fear can be readily extinguished in experimental animals but anxiety disorders are known o be chronic conditions that do not abate even if a patient has multiple experiences in which previously avoided situations do not result in acute ffear responses. Hences, it is important to consider other areas of the neural circuitry involved in fear responses when attempting to fully understand the neuroanatomy and physiology of anxiety disorders. Recently, a few research groups found that patients with PD, SAD and PSD manifest decreased PFC activity dring the experience of acute anxiety responses. In particular, decreases in activity in the anterior cingulte and in the orbital frontal cortex (OFC) have been cited. Using fMRI, our group found that amygdalar activation in normal volunteers during the presentation of fears cues is blunted when subjects are given a task that demands PFC engagement. Using magnetic resonance spectroscopy, we found decreased concentration of a marker of neuronal viability, N-acetyl aspartate, in the anterior cingulate of adult non-human primates who had been raised under conditions of mild stress dring infancy. In collaboration with colleagues at Cornell University, as part of our Conte Neuroscience Center we recently reported, using fRI, that patients with PD have increased right amygdala and decreased OFC activity during a fear-inducing procedure. Finally, in a pilot study using 15O-PET imaging involving patients with PD and normal controls, we found a marked decrease in OFC blood flow immediately prior to panic attacks induced by the administration of doxapram. This suggests, as some speculations predicts, that reduced PFC activity occurs during the anticipatory anxiety stage immediately prior to a panic attack, thus increasing amygdala activity. Previously, we have shown that in this exact same period prior to panic, patients with PD manifest increased anxiety, increased cortisol level and decreased pCO2 an indication of acute hyperventilation. On the other hand, studies in patients with generalized anxiety disorder (GAD), OCD, and PD also suggest greater activation in regions of the prefrontal cortex than in normal comparison subjects. Hence, there is ambiguity in the literature at present about the way in which the PFC and aygdala interact in PD patients at rest, during anticipatory anxiety, and during panic. Also, in our most recent pilot study using the methods we propose to use in the present study, we found tht following placebo adminitration, when subjects were in an anticipatory anxiety state, patients with PD showed increased aygdalar and increased OFC metabolic rate compared to comparison subjects. During doxapram-induced panic attacks and subtracting out the placebo responses the patients showed further greater increases in amygdalar and OFC metabolic rate compared to controls. Thus, our pilot data show patient control differences in the amygdala that are consistent with our hypotheses, but findings in the PFC that are not. Interestingly, during the placebo infusion we noted an increased left/right ratio in Brodmann area 11 in patients, consistent with psychological theory implicating an anxious anticipatory rather than arousal state. During doxapram infusion, enhanced amygdalar metabolic rate increases in patients are most prominent on the left side, suggesting continuation of anticipatory anxiety into that phase. hence, in the revised application we now include efforts to use instruments sensitive to anxious anticipation and arousal in an attempt to disaggregate these psychological states and better explain the findings. Treatment with cognitive behavioral therapy (CBT) normalized the prefrontal findings in the patients, but had no effect on the amygdala findings. Finally, in exploratory analyses of our pilot data, we uncovered differential relationships between the dorsa___d ventral amygdala and the OFC in patients compared to controls that parallel recent preclinical findings. Taken together, these observations indicate that patients with PD have abnormal patters of regional brain activation compared to controls, some of which may be amenable to improvement with sychoscial intervention, but that studies with expanded sample sizes and rigorous methodology are needed to clarify some of the inconsistencies in the existing literature. We therefore, propose to study this critical aspect of the neurocircuitry of fear by employing a study design that will permit us to image and quantify activity in the OFC and other key brain regions during three conditions of emotional arousal: 1) at rest, experiencing """"""""ordinary"""""""" levels of anxiety;2) during anticipatory anxiety;and 3) during panic anxiety, in untreated patients with PD, and then to repeat this after treatment with CBT. We will use panic anxiety, in untreated patients with PD, and then to repeat this after treatment with CBT. We will use doxapram as the """"""""panicogenic"""""""" agent in this study because of its high rate of panic induction in PD patients and relatively low rate in normal volunteers and because previous work has shown that panic to doxapram is affedted by """"""""cognitive set."""""""" We will employ 18flurodeoxyglucose (FDG) PET imaging instead of 15O-Hs) PET imaging in this study because we wish to measure the metabolic acitvity fo specific brain regions before and during panic attacks. HYPOTHESIS; 1. Prior to treatment, following a saline (placebo) injection but anticipating that they will receive the panicogen doxapram, patients with PD will show altered metabolic activity in the orbital frontal cortex (OFC) as measured by FDG-PET compared to normal comparison subjects and to a separate group of PD patients undergoing FDG-PET scans during a resting condition. 2. There will be significant statistical associations between OFC acitvity, increased anxiety, increased salivary cortisol level, increased heart rate, and increased minute ventilation (the product of respiratory frequency and the tidal volume of breathing) following saline administration (i.e. in the anticipatory state) in PD patients. 3. Prior to treatment, an injection of doxapram will prduce panic attacks in approximately 70% of patients with PD but only 20% of normal comparison subjects. Panicking subjects will show alterred OFC and amygdala metabolic activity compared to non-panicking subjects and to a separate group of PD ptients undergoing FDG-PET scans djuring a resting condition. 4. Prior to treatment, patients with PD will show increased 24-hour urinary cortisol levels, increased variability fo respiration, and decreased heart period variability compared to controls. These will be correlated with OFC metabolic activity during the FDG-PET scans, sggesting coordinated abnormalities between the autonomic nervous system, the hypothalamic-pituitary-adrenal (HPA) axis, and prefrontal cortical activity in PD patients. 5. Baseline OFC acitvity, anxiety level,cortisol and physiological measures both to saline and doxapram will be correlated with treatment response, and post treatment outcomes measures (PDSS, HAM-A, HAM-D, ASI etc.).
Showing the most recent 10 out of 869 publications
