The alpha rhythm in the electroencephalogram: a theory based on a neurophysiological model

A column in the cerebral cortex is made up of a group of neurons and is considered to be a functional unit. Previous work has suggested that a column has two separate levels of activity, and that only a few of the columns are at the high level of activity simultaneously. To keep this number within proper limits, it is necessary to have a regulating system that reduces the cortical excitability when the number tends to increase, and vice versa. In the present paper, it is proposed that these changes up and down in the excitability can explain the generation of the alpha rhythm in the electroencephalogram. Preliminary results show that a normal alpha rhythm of about 10 Hz can be generated when the number of columns with high activity is shifting between four and five. The duration of the high activity of a column is around 450 ms.