1. Electroencephalogram (EEG) and Its Background

Electroencephalograms (EEGs) have become increasingly important measurements of brain activities for the diagnosis and treatment of mental and brain diseases and abnormalities. EEG recordings provide information about electrical activity of the brain. EEG signals’ parameters and patterns indicate the health states of the brain. The study of the brain electrical activity, through the EEG records, is one of the most important tools for the diagnoses of neurological diseases, such as epilepsy, brain tumour, head injury, sleep disorder, dementia and monitoring depth of anaesthesia during surgery etc. It may also be recommended for the treatment of abnormalities, behavioural disturbances (e.g. Autism), attention disorders, learning problems, language delay etc. This chapter provides an overview about fundamental knowledge of Electroencephalogram (EEG) signals including its generation mechanism, characteristics and natures. At last, this chapter discusses on the abnormal EEG patterns for different neurological disease and disorders with some illustrations.