Electroencephalography

A normal electroretinogram was seen in one of the six subjects examined by Korey and Terry (1963), but the cortical response was absent even in this case. 

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The spontaneous electrical activity of the brain can be measured by electroencephalography (EEG), a technique that has been widely employed to study neurotoxic effects of chemicals both in humans and in experimental animals. EEG waves represent summated synaptic potentials generated by the pyramidal cells of the cerebral cortex (Misra 1992). These potentials are the responses of cortical cells to rhythmical changes arising from thalamic nuclei. The signals recorded can be separated into frequency bands—faster waves exceeding 13 Hz, and slower ones below 4 Hz. 

Vajda, A. Schmid, H., and Groll-Knapp, E. et al. (1974). EEC changes in evoked potentials caused by insecticides. Electroencephalography and Clinical Neurophysiology 37, 442. 

In medical practice, methods and instruments relying on electrochemical principles are widely nsed in diagnosing various diseases. The most important ones are electrocardiography, where the transmembrane potential of the muscle cells during contraction of the heart mnscle is measured, and electroencephalography, where impulses from nerve cells of the brain are measured. They also include the numerous instruments nsed to analyze biological fluids by electrochemical methods (see also Section 30.3). 

BP, blood pressure Cl, continuous infusion CT, computed tomography ECG, electrocardiogram EEG, electroencephalography HR, heart rate ICU, intensive care unit IV, intravenous IVP, intravenous push OTC, over the counter MRI, magnetic resonance imaging PE, phenytoin equivalents PR, per rectum RR, respiratory rate T, temperature. 

Other diagnostic tests to consider for differential diagnosis erythrocyte sedimentation rate, urinalysis, toxicology, chest x-ray, heavy metal screen, HIV testing, cerebrospinal fluid (CSF) examination, electroencephalography, and neuropsychological tests such as the Folstein Mini Mental Status Exam. 

Evaluation Perform computed tomography (CT) scan and MRI for evaluation of acute event. Perform magnetic resonance angiography for asymptomatic infarction. Perform transcranial Doppler to detect abnormal velocity and identify high-risk patients. Perform electroencephalography if there is a history of seizure. 

Electroencephalography The recording of brain waves via electrodes placed on the scalp or cortex. 

Belyavin, A., and Wright, N. A., Changes in electrical activity of the brain with vigilance. Electroencephalography and Clinical Neurophysiology 66(2), 137-144, 1987. 

Electroencephalography allows real-time measurement of neural activity with millisecond temporal resolution. When coupled with the repeated presentation of a stimulus, the electroencephalograms can be averaged to produce an event-related potential (ERP), whose components develop and resolve within tens or hundreds of milliseconds. These potentials are designated by the millisecond lag between presentation of the stimulus and the appearance of the ERP, with the P50 (i.e. potential at 50 ms after... 

Electroencephalography Burst suppression Burst suppression Epileptiform activity Burst suppression Burst suppression ... 

Reflex action can be objectively examined. Measurement of the so-called electrical conduction velocity of motor nerves gives an indication of whether peripheral nerves have been damaged. Electromyography, or examination of the electrical activity of the muscle, and electroencephalography (EEG) can also be used to detect the presence of neurologic abnormalities. And, at least in animal tests, detailed pathological examination of neural tissue can be performed on animals that are killed. 

Williams, R.L. et al. (1974). Electroencephalography (EEG) of Human Sleep Clinical Applications. New York John WUey and Sons. 

Dement, W. 8r N. Kleitman (1957a). Electroencephalography Clinical Neurophysiology 9,... 

Dement, W. (1958). Electroencephalography and Clinical Neurophysiology 10, 291-296. Dement, W. 8c N. Kleitman (1957a). Journal of Experimental Psychology 53, 339-346. Dement, W. 8c N. Kleitman (1957b). Electroencephalography and Clinical Neurophysiology 9, 673-690. 

Wong, M.T.H., Lumsden, J., Fenton, G.W., and Fenwick, P.B.C. (1994) Electroencephalography, computer tomography and violence rating of male patients in a maximum-security mental hospital. Acta Psychiatr Scand 90 97-101. 

Mendlewicz J, Kerkhofs M Sleep electroencephalography in depressive illness a collaborative study by the World Health Organization. Br J Psychiatry 159 505-509, 1991... 

Riemann D, Berger M The effects of total sleep deprivation and subsequent treatment with clomipramine on depressive symptoms and sleep electroencephalography in patients with a major depressive disorder. Acta Psychiatr Scand 81 24-31, 1990... 

Greenblatt, D J., Harmatz, J.S., Gonthro, T.A., et a/. Distinguishing a benzodiazepine agonist ( triazolam) from a nonagonist anxiolytic (buspirone) by electroencephalography kinetic-dynamic studies. CHn. Pharmacol. Ther. 56, 100— 111, 1994. 

Matejcek, M. Pharmaco-electroencephalography the value of quantified EEG in psychopharmacology. Pharmakopsvchiatrie 12, 126-136, 1979. 

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