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Nitric oxide (NO) is a potent central neuromodulator of respiration, yet its scope and site of action are unclear. We used 7-nitroindazole (7-NI), a selective inhibitor of endogenous neuronal NO synthesis, to investigate the neurogenesis of respiration in larval bullfrog (Rana catesbeiana) isolated brain stems. 7-NI treatment (0.0625-0.75 mM) increased the specific frequency of buccal ventilation (BV) events, indicating influence on BV central rhythm generators (CRGs). The drug reduced occurrence, altered burst shape, and disrupted clustering of lung ventilation (LV) events, without altering their specific frequency. LV burst occurrence and clustering also differed between pH conditions. We conclude that NO has diverse effects on respiratory rhythmogenesis, being necessary for the expression of respiratory rhythms, inhibiting the frequency of BV CRG, and affecting both shape and clustering of LV bursts through conditional modulation of LV CRG. We confirm central chemosensitivity in these preparations and demonstrate chemomodulation of LV burst clustering and occurrence but not specific frequency. Results support distinct oscillators underlying LV and BV CRGs. nitric oxide synthase; neuronal nitric oxide synthase; nitric oxide synthase-1; breathing; central pattern generation; central chemoreception; carbon dioxide; 7-nitroindazole; L-arginine; amphibian; tadpole; Rana catesbeiana; episodic periodic discontinuous clustered breathing

In this study, the interaction between increased gain in the visual feedback loop and motor control of the periphery was investigated. Participants (N = 15) were asked to maintain a constant finger position while they used magnified visual feedback. The measure of the accuracy of each trial was the standard deviation (trial error) of the finger position. Trials performed under magnification had lower trial errors than trials without magnification. The change in trial error between trials with and without magnification proved greater than the difference between trials at any 2 magnifications. In contrast, the differences between individual subjects were often greater than the differences between performances at individual magnifications. At higher magnifications, performance seemed to be limited by the tremor; the ratio of trial error to tremor intensity was constant. When applied to microsurgery, the present results accord with those found in earlier research, including investigations that have found that the level of magnification used in microsurgery is not the most significant factor in achieving good results and that tremor is the limiting factor in microsurgical tasks., The most significant performance factor in determining good results in microsurgery is not the level of magnification that is used, but rather it is tremor that limits performance. Recent trial experiments indicated that tremor intensity and trial error is consistent, even when magnification is high., Key words: finger position, magnification, postural control, tremor, visual feedback Effective motor performance involves proper integration of several factors, including visual inputs (Glass, Beuter, & Larocque, 1988; Kerr, 1992), proprioceptive [...]

Several letters to the editor in response to the article "The Parafacial Respiratory Group (pFRG)⁄pre-Bötzinger Complex (preBötC) is the Primary Site of Respiratory Rhythm Generation in the Mammal" are presented.

A realistic model of the human ventilatory controller during sleep is presented. The model consists of two chemoreflex feedback loops (central and peripheral) each with its own delay and gain. An initial stability analysis of the resultant model produces a thumb shape region of stability for the steady state solution. Changes in cerebral blood flow in the model had profound changes in the shape of the region of the stability. Increasing the gain of either the central or the peripheral loop yielded periodic solutions consistent with observed data from humans. The model provides a new tool for understanding human ventilation during sleep. The interaction of the two loops produces complex dynamics. Understanding these dynamics will assist in the treatment of sleep-disordered breathing. [ABSTRACT FROM AUTHOR]