Grzegorz Marcin Wójcik

Sanei/EEG Signal Processing, 2013

Introduction to EEG The neural activity of the human brain starts between the 17th and 23rd week of prenatal development. It is believed that from this early stage and throughout life electrical signals generated by the brain represent not only the brain function but also the status of the whole body. This assumption provides the motivation to apply advanced digital signal processing methods to the electroencephalogram (EEG) signals measured from the brain of a human subject, and thereby underpins the later chapters of the book. Although nowhere in this book do the authors attempt to comment on the physiological aspects of brain activities there are several issues related to the nature of the original sources, their actual patterns, and the characteristics of the medium, that have to be addressed. The medium defines the path from the neurons, as so-called signal sources, to the electrodes, which are the sensors where some form of mixtures of the sources are measured. Understanding of neuronal functions and neurophysiological properties of the brain together with the mechanisms underlying the generation of signals and their recordings is, however, vital for those who deal with these signals for detection, diagnosis, and treatment of brain disorders and the related diseases. A brief history of EEG measurements is first provided. 1.1 History Carlo Matteucci (1811-1868) and Emil Du Bois-Reymond (1818-1896) were the first people to register the electrical signals emitted from muscle nerves using a galvanometer and established the concept of neurophysiology [1,2]. However, the concept of action current introduced by Hermann Von Helmholz [3] clarified and confirmed the negative variations that occur during muscle contraction. Richard Caton (1842-1926), a scientist from Liverpool, England, used a galvanometer and placed two electrodes over the scalp of a human subject and thereby first recorded brain activity in the form of electrical signals in 1875. Since then, the concepts of electro-(referring to registration of brain electrical activities) encephalo-(referring to emitting the signals from the head), and gram (or graphy), which means drawing or writing, were combined so that the term EEG was henceforth used to denote electrical neural activity of the brain.

SpringerBriefs in Applied Sciences and Technology, 2018

The human brain is a major part of the central nervous system (CNS). The CNS and the peripheral nervous system (PNS) are two major sections of the human nervous system. The CNS comprises of the brain and the spinal cord, whereas, the PNS connects the CNS to primary sensory organs of the body such as the eye, ear, nose, etc., and other organs of the body. It comprises of the spinal nerves, 12 cranial nerves, and the autonomic nerves which regulate the cardiac muscles, blood vessel wall, and gland muscles. The CNS receives information from the sensory organs and resends this information to the PNS. This chapter gives details on the human brain and its constituent features. It also discusses electroencephalography (EEG) recording, the physics behind it, EEG electrodes, their composition, and other necessary details. The last section is about the conventional EEG placement methodologies. 2.1 Neurons Neurons can be called the basic units of the nervous system. Any cell in the nervous system has neuron as its primary component. Neurons can be of the following three types:

2016

Electroencephalographic measurements are commonly used in medical and research areas. This review article presents an introduction into EEG measurement. Its purpose is to help with orientation in EEG field and with building basic knowledge for performing EEG recordings. The article is divided into two parts. In the first part, background of the subject, a brief historical overview, and some EEG related research areas are given. The second part explains EEG recording.

Wiley Encyclopedia of Biomedical Engineering, 2006

Electroencephalographic measurements are commonly used in medical and research areas. This review article presents an introduction into EEG measurement. Its purpose is to help with orientation in EEG field and with building basic knowledge for performing EEG recordings. The article is divided into two parts. In the first part, background of the subject, a brief historical overview, and some EEG related research areas are given. The second part explains EEG recording.

An Electroencephalography or EEG signal carries the valuable information to study the functioning of brain and neurobiological disorders. EEG is a special type of technique for the measurement of brain electrical functions which is nothing but a graphical representation of difference in voltages from two sites of brain recorded over time. Since these EEG measurements are used in Medical and research areas, this is considered to be one of the noninvasive method to study and examine the human brain. This paper imparts sufficient information for understanding the concept of EEG signals and its recording system along with their application in some specific areas.

Computational Intelligence and Neuroscience, 2010

Human neocortical processes involve temporal and spatial scales spanning several orders of magnitude, from the rapidly shifting somatosensory processes characterized by a temporal scale of milliseconds and a spatial scales of few square millimeters to the memory processes, involving time periods of seconds and spatial scale of square centimeters. Information about the brain activity can be obtained by measuring different physical variables arising from the brain processes, such as the increase in consumption of oxygen by the neural tissues or a variation of the electric potential over the scalp surface. All these variables are connected in direct or indirect way to the neural ongoing processes, and each variable has its own spatial and temporal resolution. The different neuroimaging techniques are then confined to the spatiotemporal resolution offered by the monitored variables. For instance, it is known from physiology that the temporal resolution of the hemodynamic deoxyhemoglobin increase/decrease lies in the range of 1-2 seconds, while its spatial resolution is generally observable with the current imaging techniques at few millimeter scale. Today, no neuroimaging method allows a spatial resolution on a millimeter scale and a temporal resolution on a millisecond scale. Nevertheless, the issue of several temporal and spatial domains is critical in the study of the brain functions, since different properties could become observable, depending on the spatiotemporal scales at which the brain processes are measured.