Neural oscillators

Neural oscillations have also been examined in EEG studies in schizophrenia (for reviews see Javitt et al., 2008 Uhlhaas et al., 2008). Gamma band (>30 Hz) measures have been of particular interest in schizophrenia, because they have been proposed to mediate perceptual feature binding. Several recent studies have reported decreased early visual-evoked gamma oscillations in schizophrenia (Spencer et al., 2003 Spencer et al., 2004 Wynn et al., 2005 Spencer, 2008). However, deficits have also been found at lower... 

The temporal, spatial, and frequency dimensions of neural oscillations associated with verbal working memory. Clin EEG Neurosci 43 145-153... 

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Systems of coupled neural oscillators frequently display bi- or even multirhyth-micity. These complex entities must be able to generate and maintain different modes of oscillation, which result in different behaviors of the organism, in response to variations in their environment. 

In addition to the compound oscillation depicted in Figures 12.16 and 12.17, the collision of two limit cycles may lead to other scenarios. One possibility is complex periodic oscillation in which one cycle of one type is followed by several of another type. This type of behavior is analogous to the bursting mode of oscillation of neural oscillators, in which a period of relative quiescence is followed by a series of action potentials. In Figure 12.18, we compare a membrane potential trace from a crab neuron with potential oscillations in a pair of physically coupled chlorine dioxide-iodide oscillators. 

Nerve cells, or neurons, are the primary means by which signaling and information transfer occur in living organisms (Levitan and Kaczmarek, 1997). The signals that neurons generate and transmit are electrical in nature moreover, they are often oscillatory. In this section, we take a brief look at how neurons work and how some of the ideas that we have developed for studying chemical oscillators can usefully be applied to understanding neural oscillations. 

Chambers JD, Bomstein JC, Thomas EA (2011) Multiple neural oscillators and muscle feedback are required for the intestinal fed state motor program. PLoS One 6(5), el9597 Chassany O, Michaux A, Bergmann JE (2000) Drug-induced diarrhoea. Dmg Saf 22(l) 53-72 Chaudhri O, Small C, Bloom S (2006) Gastrointestinal hormones regulating appetite. Philos Trans RSocB 361 1187-1209... 

Zhang, D., Poignet, R, Widjaja, F., and Tech Ang, W. 2011. Neural oscillator based control for pathological tremor suppression via functional electrical stimulation. Control Eng. Practice, 19(1), 74-88. 

Some of the main types of cellular regulation associated with rhythmic behavior are listed in Table III. Regulation of ion channels gives rise to the periodic variation of the membrane potential in nerve and cardiac cells [27, 28 for a recent review of neural rhythms see, for example, Ref. 29]. Regulation of enzyme activity is associated with metabolic oscillations, such as those that occur in glycolysis in yeast and muscle cells. Calcium oscillations originate... 

As indicated above, theoretical models for biological rhythms were first used in ecology to study the oscillations resulting from interactions between populations of predators and preys [6]. Neural rhythms represent another field where such models were used at an early stage The formalism developed by Hodgkin and Huxley [7] stiU forms the core of most models for oscillations of the membrane potential in nerve and cardiac cells [33-35]. Models were subsequently proposed for oscillations that arise at the cellular level from regulation of enzyme, receptor, or gene activity (see Ref. 31 for a detailed fist of references). 

Researchers have oscillated between emphasizing specificity of neurons ( labeled lines ) and responses to a spectrum of tastants by one cell. More recently, patterns of activation of a number of sensory cells are favored for coding specific taste sensations (Smith and Margolskee, 2001). Neural distinction of different tastes requires simultaneous activation of different cell types. The brain receives a single channel of information, simply bitter for a number of different compounds. 

It is possible to show that when the different parts of a system are connected by nonlinear interactions, one can again obtain oscillation in concentrations, patterns of chemical substances in space, and wave propagation. These phenomena are important in some biological problems when the reaction-diffusion mechanisms cannot give an adequate description of the system. Morphogenetic fields and neural networks are examples of such systems. 

Wehr M. and Laurent G. (1996) Odour encoding by temporal sequences of firing in oscillating neural assemblies. Nature 384, 162-166. 

In several insect types the presence of oscillations among AL neural assemblies have been demonstrated. The main experimental animal for these investigations has been the locust. In these experiments it has been shown how synchronous oscillations allow a temporal coding of odor information. These experiments will be further elaborated in the following paragraphs. 

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Light GA, Hsu JL, Hsieh MH, Meyer-Gomes K, Sprock J, et al. 2006. Gamma band oscillations reveal neural network cortical coherence dysfunction in schizophrenia patients. Biol Psychiatry 60 1231-1240. 

Spencer KM. 2008. Visual gamma oscillations in schizophrenia Implications for understanding neural circuitry abnormalities. Clin EEG Neurosci 39 65-68. 

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