Brain waves are chaotic during an epileptic attack, as this electroencephalogram shows. (Credit, Nature Magazine).
Some clips from the review:
...neurons not only respond to stimuli, but often do so in a rhythmic fashion. The strength of neural rhythms can predict a subject's performance on a task. Even when we sleep, neurons in most parts of the brain are active in a highly rhythmic fashion. By contrast, epileptic fits and Parkinson's disease are accompanied by an abnormal increase in certain brain rhythms...Buzsáki describes a wide range of brain rhythms, ranging from very slow rhythms of the order of 1 cycle per second up to several hundred cycles per second. The frequency of rhythms changes as a function of development, ageing and disease. The frequency of oscillations often changes dramatically within a few seconds, as a function of the animal's behaviour...Buzsáki then moves on to describe possible functions of brain rhythms, such as resonance, synchronization of neural circuits, and improvement of signal-to-noise ratio by stochastic resonance...Buzsáki's book describes the amazing influence of oscillations on information encoding in the hippocampus and how this may be critical for learning facts and events. It ends with a discussion of some of the toughest problems in the field, such as what consciousness is, and how to irrefutably demonstrate the role of oscillations in brain function.