The Brain’s Alpha Rhythms and the Mind

It is well known that the alpha rhythm is the most common component of the brain's electrical activity, the electroencephalogram (EEG), which can be recorded in a healthy awake adult human. This, it seems, is the only fact about alpha rhythm that we can be sure about. Is alpha activity a single alpha rhythm (as is classically described), or are there many oscillations at alpha frequencies in the brain, forcing us to use the more generic term alpha activities to encapsulate this wider concept? The precise nature of alpha oscillations is as yet unclear: does alpha rhythm result from intrinsic cellular oscillations or does it emerge due to reverberating circuits which depend on the interaction time constants of two or more cells? What does fast or phasic variability of alpha activity mean? If the periods of alpha synchronization reflect " rest " or an " idling state " of the brain, then why does synchronized alpha activity dominate in the EEG of an awake adult human? From viewpoint of the common sense, it is not economical for an organism to " use " the brain cortex only half (on average) of the total time that a human is awake. We do not yet fully understand the biological, behavioural, physiological and functional significance of alpha rhythm and its responses. Moreover, there are a lot of misconceptions about alpha rhythm in relation to the functions of the brain's hemispheres, and to altered states of consciousness, which need to be corrected and put in perspective. It is not surprising that starting from the first registrations of EEG there has been considerable interest in the sphere of brain alpha rhythm and in the search for a general theory that can explain what alpha rhythm is and why and how it originates. Over the past century the diversity of results has led to many alternative hypotheses which account for the genesis of alpha oscillations. Besides well-known and generally accepted hypotheses, there are a number of more exotic ones which describe alpha rhythm as an atavistic feature of humans, or which explain the dominating alpha oscillations in terms of evolutionary adjustment of neuronal tissue to oscillations of the earth's atmosphere. All these suggest the need to develop a general theoretical framework that allows researchers to handle an enormous amount of diverse observations related to alpha phenomena: there have been more than 50.000 research publications on this …