Theta power

These data thus confirm our initial hypothesis that mGlu2/3 receptors are tonically active in lowering the level of brain arousal. Thus, antagonizing these receptors increases arousal as evidenced by the increase in waking and the stimulation of high-frequency EEG power. The striking increase in theta power was unexpected but is also consistent with increased arousal. 

BW373U86 increased hippocampal type 2 theta power in rat EEG measurements however, this study did not test doses of BW373U86 that would produce convulsions in rats [51]. Therefore, it is difficult to determine the role of seizures in the antidepressant-like effects of delta opioid agonists. This concept must be studied in the future to determine the role of seizure activity or electroencephalographic activity in the antidepressant-like effects of delta opioid agonists. 

Significantly different Theta power response was observed in the Cz channel, as seen in Fig. 11.17. The mean of the difference is less than zero at 83% confidence level, which indicates that Pattern 1.2 evoked higher Theta power than Pattern 1.1 at the centre of the central sulcus of the brain. 

Figure 11.17 A significant result of the Theta power corresponding to Patterns 1.1 and 1.2.

Significant results of Theta power were also found in most areas of the brain, including the frontal lobe at channels Fz and F4, the Cz and C4 channels in the central sulcus, the P3, Pz and P4 channels over the parietal lobe, and the 01, 02 channels over the occipital lobe, as shown in Fig. 11.28. The mean of the observed differences is over zero at above 85% confidence level, which indicates that Pattern 3.1 evoked significantly higher Theta power than Pattern 3.2 in these areas of the brain. 

Significant differences of Theta power were observed in the Fpl and Fp2 channels over the prefrontal lobe as shown in Fig. 11.34. The mean of difference of these channels is less than zero at 90% confidence level, which shows that Pattern 4.1 triggered lower Theta power than Pattern 4.2 in the prefrontal lobe of the brain. 

The linearity of L with N is maintained at the theta point. Relative to Eq. 5, the chains have shrunk by a factor of (a/d),/3 but the linear variation indicates that the chains are still distorted at the theta point and characteristic dimensions do not shrink through a series of decreasing power laws as do free chains [29-31]. Experimentally, Auroy [25] has produced evidence for this linearity even in poor solvents. Pincus [32] has recently applied this type of analysis to tethered polyelectrolyte chains, where the electrostatic interactions can produce even stronger stretching effects than those that have been discussed for good solvents. Tethered polyelectrolytes have also been studied by others [33-35],... 

Simulation methods have been proved to be useful in the study of many different molecular systems, in particular in the case of flexible polymers chains [ 14]. According to the variety of structures and the theoretical difficulties inherent to branched structures, simulation work is a very powerful tool in the study of this type of polymer, and can be applied to the general problems outHned above. Sometimes, this utility is manifested even for behaviors which can be explained with simple theoretical treatments in the case of linear chains. Thus, the description of the theta state of a star chain cannot be performed through the use of the simple Gaussian model. The adequate simulation model and method depend strongly on the particular problem investigated. Some cases require a realistic representation of the atoms in the molecular models [10]. Other cases, however, only require simplified coarse-grained models, where some real mon-... 

It should also be noted that ternary and higher order polymer-polymer interactions persist in the theta condition. In fact, the three-parameter theoretical treatment of flexible chains in the theta state shows that in real polymers with finite units, the theta point corresponds to the cancellation of effective binary interactions which include both two body and fundamentally repulsive three body terms [26]. This causes a shift of the theta point and an increase of the chain mean size, with respect to Eq. (2). However, the power-law dependence, Eq. (3), is still valid. The RG calculations in the theta (tricritical) state [26] show that size effect deviations from this law are only manifested in linear chains through logarithmic corrections, in agreement with the previous arguments sketched by de Gennes [16]. The presence of these corrections in the macroscopic properties of experimental samples of linear chains is very difficult to detect. 

The effects of kavain on human electrophysiology was examined in a double-blind, placebo-controlled study (Frey 1991). Dose-dependent increases were seen in delta, theta, and alpha 1 power, and decreases ocurred in alpha 2 and beta power. These changes were suggestive of a sedative effect of kavain, and were maximal in frontal areas. Interestingly, an initial activating effect was seen at the lowest dose (200 mg) but not at the largest dose (600 mg). 

When long-term chronic cannabis users (i.e., daily use for 15-24 years) were compared to shortterm users and nonusers, they were found to have elevated absolute power of theta activity over bilateral frontal-central cortex, as well as significantly increased interhemispheric coherence of theta activity across central and posterior regions (Struve et al. 1998). Concurrent reaction time studies also showed slowed cognitive processing in that group. Other work by this group has shown that in... 

Flory and Huggins developed an interaction parameter that may be used as a measure of the solvent power of solvents for amorphous polymers. Flory and Krigbaum introduced the idea of a theta temperature, which is the temperature at which an infinitely long polymer chain exists as a statistical coil in a solvent. 

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