A phase synchrony measure for quantifying dynamic functional integration in the brain

The temporal coordination of neural activity within structural networks of the brain has been posited as a basis for cognition. Changes in the frequency and similarity of oscillating electrical potentials emitted by neuronal populations may reflect the means by which networks of the brain carry out functions critical for adaptive behavior. A computation of the phase relationship between signals recorded from separable brain regions is a method for characterizing the temporal interactions of neuronal populations. Recently, different phase estimation methods for quantifying the time‐varying and frequency‐dependent nature of neural synchronization have been proposed. The most common method for measuring the synchronization of signals through phase computations uses complex wavelet transforms of neural signals to estimate their instantaneous phase difference and locking. In this article, we extend this idea by introducing a new time‐varying phase synchrony measure based on Cohen's class of time–frequency distributions. This index offers improvements over existing synchrony measures by characterizing the similarity of signals from separable brain regions with uniformly high resolution across time and frequency. The proposed measure is applied to both synthesized signals and electroencephalography data to test its effectiveness in estimating phase changes and quantifying neural synchrony in the brain. Hum Brain Mapp, 2010. © 2010 Wiley‐Liss, Inc.     

Influence of talc dose on extrapleural talc dissemination after talc pleurodesis

This study was designed to ascertain, in a rabbit model, extrapleural talc deposition and the related inflammatory response after talc slurry pleurodesis with two clinical doses, 200 and 50 mg/kg. Histopathologic evaluations revealed that whereas numerous rabbits receiving a high dose had talc in the ipsilateral (70%) and contralateral (55%) lung, mediastinum (90%), pericardium (30%), and liver (25%), a small number of animals treated with a low dose showed talc in the ipsilateral lung (10%) and mediastinum (20%) and none in the contralateral lung, pericardium, or liver. Hematologic and immunocytochemical analyses showed that a systemic inflammatory response develops shortly after pleurodesis with a high talc dose involving massive accumulation of neutrophils and macrophages in lung tissue. Zymography also revealed that the pulmonary expression of matrix metalloproteinases 2 and 9 was up-regulated in both lungs in a dose-dependent manner soon after talc instillation. Furthermore, microscopic examination of lung specimens revealed that the higher the dose of talc, the greater the development of both fibrotic visceral pleural thickening and foreign-body granulomas. These findings show pleurodesis with a high talc dose to be associated with an increased risk of extrapleural talc deposition, which may originate undesirable acute and chronic inflammatory responses.     

Activation of the 10-Hz sympathetic generator during the second phase of severe hypoxia-hypercapnia and Cushing reaction

Under urethane anesthesia, as in freely moving cats, the sympathetic nerve discharge (SND) contains a 10-Hz component, either as a single peak in the autospectra or in addition to the cardiac-related or 2-6-Hz rhythm. In this study, we examined the changes in these rhythmic SND components during the reaction to asphyxia and to sudden elevation in the intracranial pressure (Cushing reaction). In all cats included in this study, resting SND was dominated by 2-6-Hz rhythm, but a peak at 10 Hz was also present in the coherence functions. During asphyxia or Cushing reaction, the 2-6-Hz component exhibited the usual two-phase pattern of activation followed by suppression. In phase 2, however, the SND did not desynchronize, as in chloralose-urethane anesthetized cats [Am. J. Physiol. 256 (1989) R120; J. Physiol. (London) 469 (1993) 37], and the massive SND activation and the resulting pressor reaction was due to strengthening of the 10-Hz rhythm. After the ischemic reaction, the 10-Hz component diminished and 2-6-Hz rhythm recovered. These findings suggest that two-phase response to hypoxia-hypercapnia is not due to hypoxic neuronal damage but represents a physiological sympathetic reaction involving different patterns of SND.     

Combined laryngotracheal separation and esophageal injury following blunt neck trauma

In this article we describe the first case of combined laryngotracheal and esophageal injury following blunt neck trauma in the otolaryngology literature and delineate appropriate management considerations. Successful reconstruction requires appropriate airway management, restoration of esophageal and laryngeal mucosal integrity, and reduction of tracheal and laryngeal fractures with appropriate stenting. Laryngotracheal separation following blunt neck trauma is rare and can be initially overlooked. After the airway is secure, injury severity dictates repair and postoperative care. Immediate reconstruction with restoration of the laryngotracheal framework and mucosal integrity enables patients to recover a patent airway, functional voice, and normal swallow.