Recording the brain´s electrical activity

Up to some 3-4 years ago, EEG signals were generally displayed using pen recorders. These could barely meet the required specification and EEG technologists spent much of their time attempting to optimise the performance of these recalcitrant devices. The situation has been dramatically changed by recent advances in PC technology, providing processing speeds and storage capacities adequate for this application (demanding data acquisition rates of at least 40 Gbytes per hour) and display devices with adequate resolution. The combination of awake and sleep recording provides information relevant to the diagnosis of epilepsy in a large majority of patients, where this is not achieved, it may be necessary to attempt to capture an EEG during a seizure. Unless attacks occur very frequently prolonged recording is necessary and, to render such records often several days or even weeks duration tolerable to the patient telemetry is used. Early telemetry systems employed a radio link. This presented many technical problems, notably the bulk of transmitters and batteries and, more critically, the limited band width permitted by telecommunications regulations. Cable telemetry is now therefore generally preferred