Activation of limbic structures during CO2-stimulated breathing in awake man

Forebrain control of breathing: Anatomy and potential functions

The forebrain plays important roles in many critical functions, including the control of breathing. We propose that the forebrain is important for ensuring that breathing matches current and anticipated behavioral, emotional, and physiological needs. This review will summarize anatomical and functional evidence implicating forebrain regions in the control of breathing. These regions include the cerebral cortex, extended amygdala, hippocampus, hypothalamus, and thalamus. We will also point out areas where additional research is needed to better understand the specific roles of forebrain regions in the control of breathing.

Frontoparietal Cortical Thinning in Respiratory-Type Panic Disorder: A Preliminary Report

OBJECTIVE

Many evidences raise the possibility that the panic disorder (PD) patients with respiratory subtype (RS) may have characteristic structural abnormalities. We aimed to explore the structural differences between PD patients with and without the respiratory symptoms.

METHODS

Patients with PD were recruited from the Department of Psychiatry at Korea University Anam Hospital. Respiratory subtype (RS) was diagnosed when at least 4 out of 5 of the following respiratory symptoms were present during the panic attack: fear of dying, chest pain/discomfort, shortness of breath, paresthesias, and a choking sensation. We acquired high-resolution MRI scans and used FreeSurfer to obtain a measure of cortical thickness for each patient.

RESULTS

Cluster based analysis revealed significantly decreased cortical thickness in the left hemisphere in the caudal-middle-frontal, superior frontal, and posterior parietal areas in the RS group. No significant difference was observed in any of the limbic areas.

CONCLUSION

Respiratory symptoms of panic disorder were associated with a reduction in cortical thickness in the left frontal and parietal areas. This finding leads to the assumption that the frontoparietal network is the crucial component in a larger cortical network underlying the perception of dyspnea in RS.

Visceral influences on brain and behavior

Mental processes and their neural substrates are intimately linked to the homeostatic control of internal bodily state. There are a set of distinct interoceptive pathways that directly and indirectly influence brain functions. The anatomical organization of these pathways and the psychological/behavioral expressions of their influence appear along discrete, evolutionarily conserved dimensions that are tractable to a mechanistic understanding. Here, we review the role of these pathways as sources of biases to perception, cognition, emotion, and behavior and arguably the dynamic basis to the concept of self.

An official American Thoracic Society statement: update on the mechanisms, assessment, and management of dyspnea

BACKGROUND

Dyspnea is a common, distressing symptom of cardiopulmonary and neuromuscular diseases. Since the ATS published a consensus statement on dyspnea in 1999, there has been enormous growth in knowledge about the neurophysiology of dyspnea and increasing interest in dyspnea as a patient-reported outcome.

PURPOSE

The purpose of this document is to update the 1999 ATS Consensus Statement on dyspnea.

METHODS

An interdisciplinary committee of experts representing ATS assemblies on Nursing, Clinical Problems, Sleep and Respiratory Neurobiology, Pulmonary Rehabilitation, and Behavioral Science determined the overall scope of this update through group consensus. Focused literature reviews in key topic areas were conducted by committee members with relevant expertise. The final content of this statement was agreed upon by all members.

RESULTS

Progress has been made in clarifying mechanisms underlying several qualitatively and mechanistically distinct breathing sensations. Brain imaging studies have consistently shown dyspnea stimuli to be correlated with activation of cortico-limbic areas involved with interoception and nociception. Endogenous and exogenous opioids may modulate perception of dyspnea. Instruments for measuring dyspnea are often poorly characterized; a framework is proposed for more consistent identification of measurement domains.

CONCLUSIONS

Progress in treatment of dyspnea has not matched progress in elucidating underlying mechanisms. There is a critical need for interdisciplinary translational research to connect dyspnea mechanisms with clinical treatment and to validate dyspnea measures as patient-reported outcomes for clinical trials.

Validation of a three-factor measurement model of dyspnea in hospitalized adults with heart failure

OBJECTIVE

The purpose of this study was to validate a 3-factor measurement model of dyspnea sensory quality (WORK-EFFORT, TIGHTNESS, SMOTHERING-AIR HUNGER) originally derived in patients with exacerbated chronic obstructive pulmonary disease.

METHODS

In this validation study, adult patients with heart failure were enrolled after hospital admission (median hospital day 1) and asked to rate the intensity of dyspnea sensory quality descriptors on the day of enrollment (study day 1; N = 119) and in a recall version for the day of admission (study day 0; n = 97).

RESULTS

Confirmatory factor analysis demonstrated good model fit for both days. Cronbach's α for each factor was greater than .87 for both study days.

CONCLUSION

This is the first study to validate a previously specified measurement model of dyspnea sensory quality in an independent sample. Results indicate that measurement of dyspnea sensory quality in exacerbated cardiopulmonary disease does not necessarily require disease-specific questionnaires.

Neurobiology of repeated transcranial magnetic stimulation in the treatment of anxiety: a critical review

Transcranial magnetic stimulation (TMS) has been applied to a growing number of psychiatric disorders as a neurophysiological probe, a primary brain-mapping tool, and a candidate treatment. Although most investigations have focused on the treatment of major depression, increasing attention has been paid to anxiety disorders. The aim of this study is to summarize published findings about the application of TMS as a putative treatment for anxiety disorders. TMS neurophysiological and mapping findings, both clinical and preclinical, have been included when relevant. We searched Medline, PsycInfo, and the Cochrane Library from 1980 to January 2009 for the terms 'generalized anxiety disorder', 'social anxiety disorder', 'social phobia', 'panic', 'anxiety', or 'posttraumatic stress disorder' in combination with 'TMS', 'cortex excitability', 'rTMS', 'motor threshold', 'motor evoked potential', 'cortical silent period', 'intracortical inhibition', 'neuroimaging', or 'intracortical facilitation'. Most of the therapeutic experiences with repetitive TMS available in the literature are in the form of case reports, not controlled or blinded studies. Stimulation of the right dorsolateral prefrontal cortex, especially at high frequencies, has been reported to reduce anxiety symptoms in posttraumatic stress disorder and panic disorder; nevertheless, results are mixed. A specific role for the right dorsolateral prefrontal cortex in the posttraumatic stress disorder symptom core can be hypothesized. TMS remains an investigational intervention that has not yet gained approval for the clinical treatment of any anxiety disorder. Clinical sham-controlled trials are scarce. Many of these trials have supported the idea that TMS has a significant effect, but in some studies, the effect is small and short lived. The neurobiological correlates suggest possible efficacy for the treatment of social anxiety that still has to be investigated.

Neural alterations associated with anxiety symptoms in obstructive sleep apnea syndrome

BACKGROUND

Neuropsychological comorbidities, including anxiety symptoms, accompany obstructive sleep apnea (OSA); structural and functional brain alterations also occur in the syndrome. The objective was to determine whether OSA patients expressing anxiety symptoms show injury in specific brain sites.

METHODS

Magnetic resonance T2-relaxometry was performed in 46 OSA and 66 control subjects. Anxiety symptoms were evaluated using the Beck Anxiety Inventory (BAI); subjects with BAI scores >9 were classified anxious. Whole brain T2-relaxation maps were compared between anxious and nonanxious groups using analysis of covariance (covariates, age and gender).

RESULTS

Sixteen OSA and seven control subjects showed anxiety symptoms, and 30 OSA and 59 controls were nonanxious. Significantly higher T2-relaxation values, indicating tissue injury, appeared in anxious OSA versus nonanxious OSA subjects in subgenu, anterior, and mid-cingulate, ventral medial prefrontal and bilateral insular cortices, hippocampus extending to amygdala and temporal, and bilateral parietal cortices. Brain injury emerged in anxious OSA versus nonanxious controls in bilateral insular cortices, caudate nuclei, anterior fornix, anterior thalamus, internal capsule, mid-hippocampus, dorsotemporal, dorsofrontal, ventral medial prefrontal, and parietal cortices.

CONCLUSIONS

Anxious OSA subjects showed injury in brain areas regulating emotion, with several regions lying outside structures affected by OSA alone, suggesting additional injurious processes in anxious OSA subjects.

Panic disorder: the psychobiology of external treat and introceptive distress

Panic disorder seems to be mediated by the neuronal circuitry and neurochemical systems that have evolved to respond to external threatening stimuli. Distant threats activate prefrontal cortex (involved in complex planning of avoidance strategies), while immediate threats activate midbrain structures (involved in fast reflexive behaviors). Panic disorder may, however, also involve more specific interoceptive mechanisms. For example, the association between respiratory dysfunction and panic disorder has bolstered a false suffocation alarm hypothesis. Genetic and environmental contributors to panic disorder are beginning to be delineated. Effective pharmacotherapy and psychotherapy are able to normalize the relevant psychobiology.

Learning in respiratory control

In this article, it is argued that learning participates to fulfill the metabolic requirements by adapting respiratory control to changing internal and external states. Recent classical-conditioning experiments in newborn mice or adult rats show the close link between conditioned respiratory and arousal responses. The conditioned fear model may be a suitable and largely unexplored model of emotionally induced hyperventilation. The parabrachial nucleus and periacqueducal grey may play a pivotal role in the ventilatory component of conditioned fear. The sensitivity of breathing to conditioning in newborn and adult animals suggests that learning processes may shape breathing pattern throughout life.