Oscillatory activity

The synchronised oscillatory activity between the intrinsically linked thalamus and cortex. Under normal circumstances there is a level of activity which changes during the sleep-wake cycle increasing during periods of slow wave sleep. Excess synchrony occurs in conditions such as epilepsy. Thiazolidinedione... 

R16. Ross, R., Miell, J., Freeman, E Jonest, J., Matthews, D., Preece, M and Buchanan, C, Critically ill patients have high basal growth hormone levels with attenuated oscillatory activity associated with low levels of insulin-like growth factor-I. Clin. Endocrinol. 35,47-54 (1991). 

Studies of mammals subjected to SCN destruction and transplantation have revealed that the hypothalamic SCN contains a master circadian oscillator which is involved in a number of behaviours and hormonal secretions. The circadian oscillatory activity of SCN neurons is directly demonstrated by the measurement of [ " C] glucose metabolic activity and field potentials assessed by electro-physiological devices. The clock oscillatory genes mPer1 and mPer2 are expressed rhythmically in most neurons in the SCN. Thus, thousands of clock cells in the SCN might generate the rhythm. 

The starting point of a number of theoretical studies of packed catalytic reactors, where an exothermic reaction is carried out, is an analysis of heat and mass transfer in a single porous catalyst since such system is obviously more conductive to reasonable, analytical or numerical treatment. As can be expected the mutual interaction of transport effects and chemical kinetics may give rise to multiple steady states and oscillatory behavior as well. Research on multiplicity in catalysis has been strongly influenced by the classic paper by Weisz and Hicks (5) predicting occurrence of multiple steady states caused by intrapellet heat and mass intrusions alone. The literature abounds with theoretical analysis of various aspects of this phenomenon however, there is a dearth of reported experiments in this area. Later the possiblity of oscillatory activity has been reported (6). 

The present article is not designed to review the work devoted to theoretical treatment of multiple steady states and oscillatory activity predicted from these equations, for those readers who seek a profound review the texts by Aris (7), Schmitz (5), and others (7,9) are recommended. 

So far we have considered an infinite value of the gas-to-particle heat and mass transfer coefficients. One may encounter, however, an imperfect access of heat and mass by convection to the outer geometrical surface of a catalyst. Stated in other terms, the surface conditions differ from those in the bulk flow because external temperature and concentration gradients are established. In consequence, the multiple steady-state phenomena as well as oscillatory activity depend also on the Sherwood and Nusselt numbers. The magnitudes of the Nusselt and Sherwood numbers for some strongly exothermic reactions are reported in Table III (77). We may infer from this table that the range of Sh/Nu is roughly Sh/Nu (1.0, 104). 

So far, there have been published only a few papers devoted to experimental investigation of multiplicity and oscillatory activity of a single catalyst particle. Observations of multiple steady states and/or oscillations for a single catalyst particle are reported in Table IV. Evidently three types of strong exothermic reactions have been investigated ... 

The classical problem of multiple solutions and undamped oscillations occurring in a continuous stirred-tank reactor, dealt with in the papers by Aris and Amundson (39), involved a single homogeneous exothermic reaction. Their theoretical analysis was extended in a number of subsequent theoretical papers (40, 41, 42). The present paragraph does not intend to report the theoretical work on multiplicity and oscillatory activity developed from analysis of governing equations, for a detailed review the reader is referred to the excellent text by Schmitz (3). To understand the problem of oscillations and multiplicity in a continuous stirred-tank reactor the necessary and sufficient conditions for existence of these phenomena will be presented. For a detailed development of these conditions the papers by Aris and Amundson (39) and others (40) should be consulted. 

Oster H, Werner C, Magnone MC, Mayser H, Feil R, Seeliger MW, Hofmann F, et al. (2003) cGMP-dependent protein kinase II modulates mPerl and mPer2 gene induction and influences phase shifts of the circadian clock. Curr Biol 13 725-33 Pape HC, Mager R (1992) Nitric oxide controls oscillatory activity in thalamocortical neurons. Neuron 9 441-8... 

A recent experiment by Lei et al. (2002), measuring intracellular activity simultaneously from two PNs in M. sexta, revealed synchrony between pairs of MGC output neurons however, in this experiment synchronous spiking was found not to be associated with oscillatory activity. Intraglomerular synchrony... 

Placantonakis DG, Schwarz C, Welsh JP. Serotonin suppresses subthreshold and suprathreshold oscillatory activity of rat inferior olivary neurones in vitro. J Physiol 2000 524(Pt 3) 833-851. 

Elinas, R.R., Grace, A.A., and Yarom, Y. In vitro neurons in mammalian cortical layer 4 exhibit intrinsic oscillatory activity in the 10- to 50-Hz frequency range. 

Niktarash A. H. Transmission of the subthalamic nucleus oscillatory activity to the cortex a computational approach. J Comput Neurosci, 2003, 25, 223-232. 

Inada T, Nakamura A, lijima Y (2003) Relationship between catechol-O-methyltransferase polymorphism and treatment-resistant schizophrenia. Am J Med Genet 120B 35-39 JoUot M, Ribary U, Lhnas R (1994) Neuromagnetic coherent oscillatory activity in the vicinity of 40 Hz coexists with cognitive temporal binding in the human brain. Proc Natl Acad Sci USA... 

Lidocaine and mexiletine both suppress the action potential features induced by a-toxins (Khodorova et al 2001). At 5—20 /iM, L accelerates the decay of the plateau (Fig. 2), reduces its area by > 80%, and halves the amplitudes of the high-frequency, post-spike oscillatory activity (Fig. 3). By comparison, inhibition of directly stimulated propagating spikes in peripheral fibres requires 200-800 fiM L (Huang et al 1997). 

Bean Do you know if you get oscillations and synchronized firing in the allodynia model Can you take nerves from those animals and see the oscillatory activity ... 

Bean I can echo Rodolfo Llinas ideas on this, which I think are insightful. A primary result from persistent Na+ current is to induce overall oscillatory activity in the CNS. This is crucial for the function of the nervous system in some way we still don t understand. A cost of this is the possibility of going into a less well controlled oscillatory activity. The normal oscillatory activity that you see reflected in the normal EEG may well reflect the activity of the persistent Na + currents in some cell types. 

T-type calcium channels (with the T standing for transient ) require only a weak depolarization for activation and carry a transient current at negative membrane potentials that inactivates rapidly during a prolonged pulse. In neurons, the T-type channel is responsible for neuronal oscillatory activity and is thought to play a role in the regulation of wakefulness and motor coordination. The pyrazine diuretic, amiloride, inhibits the T-type calcium channel. 

Barnacle muscle Morris and Lecar [1981] sought to model the oscillatory activity in current-clamped barnacle muscle fibers using just two noninactivating currents a fast calcium current and a potassium current. It should be kept in mind that their model does not take into account the presence of a calcium chelator (EGTA) inside the cells used to obtain experimental results. Their equations have the same general structure as the HH equations ... 

PitzHugh-Nagumo The FitzHugh-Nagumo equations are also called the Bonhoeffer-Van der Pol equations and have been used as a generic system that shows excitability and oscillatory activity. FitzHugh [1969] showed that much of the behavior of the Hodgkin-Huxley equations can be reproduced by a system of two differential equations ... 

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