Alpha band

They recorded EEG and local field potentials (LFPs) from macroelectrodes inserted into the subthalamic nucleus area in nine awake patients following functional neurosurgery for PD. Patients were studied after overnight withdrawal of medication. Coherence between EEG and SA LFPs was apparent in the theta (3-7 Hz), alpha (8-13 Hz), lower beta (14-20 Hz), and upper beta (21-32 Hz) bands, although activity in the alpha and upper beta bands dominated. Theta coherence predominantly involved mesial and lateral areas, alpha and lower beta coherence the mesial and ipsilateral motor areas, and upper beta coherence the midline cortex. SA LFPs led EEG in the theta band. In contrast, EEG led the depth LEP in the lower and upper beta bands. SA LFP activity in the alpha band could either lead or lag EEG. 

This rather straightforward chain of situation-reaction relationship can be modified by characteristics of the situation such as additional emotional load caused by danger or time pressure. The "effort" system has the property to disconnect Arousal Systems 1 and 3 to prevent immediate action and dlitate deliberate analysis performed by certain cortical-subcortical brain circuits (Gray, 1982). However, Arousal System 1 facilitates the focusing of attention to the situational demands. In this case, an increase of spontaneous, nonstimulus-specific EDRs will indicate an emotional load that comes with the situation (Fowles, 1980). The ongoing central information processing will be reflected both by the dominance of the beta frequency band over the alpha band in the EEG and a decrease in heart rate variabihly (HRV). 

In addition to broadband powers, peak frequencies in the spectra were determined for the alpha band. A numerical value for the alpha peak frequency was obtained by calculating the frequency at the center of gravity of the spectra in the alpha band that is, the sum of spectral values multiplied by their frequency was divided by the sum of spectral values. 

Profiles of three parameters for the EEG alpha band (alpha broadband power, alpha desynchronization index and alpha peak frequency) for the outgoing flight and the homegoing flight. One star denotes an error probability of less than 5%, two stars of less than 1% for the contrasts in the interaction of the factors "time of day" and "flight" (UTC Universal Time Coordinates). 

Table 1-1 gives the alpha, beta, and gamma absorption bands of some cytochromes, including cytochrome c. Whereas the alpha band of purified cytochrome c has its maximum exactly at 550 mp, the spectrum of heart mitochondria has its maximum at 551 mp. However, when the mitochondria are heated, the band position moves to 550 mp. These results suggested to Keilin and Hartree that the spectrum of heart mitochondria is the resultant of two spectra. Indeed, repeated washings of the particles led to the discovery of a thermolabile, insoluble cytochrome with a maximum alpha band at 553-554 mp. 

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