from Section 3 - Radiological and neurophysiological investigations
Published online by Cambridge University Press: 01 March 2011
Introduction
The electroencephalogram (EEG) records electrical activity from the cerebral cortex. This activity is derived from synchronized postsynaptic action potentials from large numbers of neurons, reflecting the functional state of the brain. Thousands of publications have described the EEG during normal and abnormal conditions, in subjects of different ages, including very preterm newborn infants. Spontaneous recurrent action potentials within thalamocortical relay cells, the reticular thalamic nucleus, and cortical pyramidal cells constitute the basis for the EEG activity (Steriade et al., 1990). This activity is synchronized by recurrent connections between the thalamocortical relay cells and the reticular thalamic nucleus, and by thalamocortical connections. In adults, intracortical connections generate higher frequency EEG components during mental processes and active wakefulness. During arousal, cholinergic (and norepinephrinergic) afferents from the brainstem exert an excitatory depolarizing effect on thalamocortical and cortical cells and inhibit the reticular thalamic cells. The net result of arousal is a reduction of synchronous low-frequency activity, and an increase of asynchronous high-frequency activity. The neurophysiological basis for the EEG in newborn preterm and term infants is not very well known. The cortical subplate zone, a structure that is present in the fetus during the second trimester and which is the origin of thalamocortical and corticocortical afferents, probably modulates EEG activity via cortical connections (Kostovic & Jovanov-Milosevic, 2006). The subplate zone is probably also important for the mechanisms underlying spontaneous activity transients (SAT) in the discontinuous EEG of very preterm infants. The SATs are characterized by very-low-frequency waves with higher-frequency components superimposed.
To save this book to your Kindle, first ensure [email protected] is added to your Approved Personal Document E-mail List under your Personal Document Settings on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part of your Kindle email address below. Find out more about saving to your Kindle.
Note you can select to save to either the @free.kindle.com or @kindle.com variations. ‘@free.kindle.com’ emails are free but can only be saved to your device when it is connected to wi-fi. ‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
Find out more about the Kindle Personal Document Service.
To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Dropbox.
To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Google Drive.