Current Trends in Neurosciences
Electroencephalographic Investigation of Brain Functions
Sevcan Ayaş Köksal, Emine Elif Tülay, Banu Femir Gürtuna, Mesut Canlı, Nuh Yılmaz, Zeliha Matur, Tamer DemiralpElectroencephalogram (EEG) as a non-invasive method of measuring brain’s electrical activity has been widely used for investigating many neuroscientific and clinical questions. Generated mainly by the post-synaptic potentials on the apical dendrites of the cortical pyramidal neurons, it represents the synchronized inputs from a wide variety of local and/or distant sources to the main output cells of the cortex and reflects the neuronal activity with a high temporal resolution. Despite the poor spatial resolution and ill-defined inverse problem of estimating the generator locations, the high temporal resolution of the EEG signal allows for precisely detecting transient brain signals such as epileptic spikes or event-related potentials (ERP) as well as for precisely characterizing the neural synchronization patterns in specific frequency bands. While the analysis of the ongoing EEG is based on the statistical characterization of rhythmic components, event-related EEG signals temporally associated with specific sensory, motor, or cognitive events, can be characterized both as transient ERP wave components in time-domain or as event-related oscillations (ERO) in the frequency domain. Such EEG analyses have provided important information about the functional organization of the healthy brain. Additionally, beyond the fundamental clinical use of the EEG in the diagnosis of the epilepsy, the ERPs and EROs allowed for a range of further clinical investigations on the neural mechanisms of various neuropsychiatric disorders. This chapter will present basic concepts, measurement and analysis methods of the EEG, and an overview with few sample studies for the use of the EEG for basic neuroscientific and clinical questions.