Cerebral states during sleep, as studied by human brain potentials.

Abstract

The general recording arrangements for taking long continuous ink records on an 8 ft drum are similar to those described in our previous paper. The three new sets of amplifiers, installed during the year, were designed to give stable and constant amplification over long runs and to have a long 'time constant,' in order to record faithfully relatively slow changes in the potentials. They were also designed not to block when large surges occur. Each of the three circuits is completely independent so that the subject need not be 'grounded* in any way. Each circuit consists of a 4-stage push-pull amplifier which has certain special devices referred to below. The amplifiers are provided with a proper amount of 'negative feed back' so that undesired or in-phase signals are amplified only to a very small extent, while the desired signals that appear differentially on the imput grids of the push-pull amplifiers may be amplified to the desired amount. This negative feed back provides for great stability and constancy of amplification. We have also found that placing large resistances directly in series with the grids of the last two stages reduces the 'blocking' very considerably, since these grids, when driven positive by too large surges, cannot draw much current. This device has recently been described by Schmitt (1937). Any one of the three amplifier systems can be tuned to any desired frequency. The outputs of the three amplifiers are led to three cathode ray oscillographs and to the impute of the three power amplifiers which operate three specially built dynamic ink writers. In order to limit the signal that can be applied to the ink writers so that they will not be damaged by an excessive signal, a limiting device has been found extremely satisfactory. This limitor consists of a neon light connected across the plates of the fourth stage, which discharges when the signal voltage reaches approximately 90 volts.With three pens the recording drum runs for 3 § hours before the paper has to be changed. The drum, 44 inches in circumference, makes one revolution in exactly one minute and therefore no additional time scale is required. Auxiliary devices permit the sending of various stimuli to the subject; for example, sound, light, touch, electric stimulation, etc., in any desired combination, and the drum is arranged to send these signals automatically at pre-detennined parts of each minute. A fourth pen records on the drum when any stimulus is sent. It can also record heart beats or respiration or noise. ELECTRODES AND ELECTRODE POSITIONThe electrodes are made of fine silver wire bent into spirals 5 mm in diameter. They are covered with Sanborn electrode paste and held in position on the scalp by collodion. No cutting of hair is necessary. The electrodes remain firmly attached and their resistance is low after 24 hours.A switching box outside of the bedroom providing for eight leads from the subject allows any combination of eight positions to be connected to any one of the three amplifiers.

Negative symptoms in neuroleptic-naïve patients with first-episode psychosis correlate with QEEG parameters

“…Moreover, we tried to control for this effect by excluding EEG recordings with signs of sleep deeper than stage A of Loomis (1937) and by controlling for the time of day of the recording.…”

“…In a last step the already corrected EEG was visually inspected by an experienced neurophysiologist who was blind to the patient's symptoms. He cut further artefacts not readily removed in steps 1 and 2 from the EEG recording: muscle, movement and electrode artefacts; patients with EEGs containing deeper sleep than stage A of Loomis et al (1937) and with EEGs that showed EEG-identifiable pathologies (e.g. generalized epilepsy) were excluded.…”

Characteristics of the Normal Electroencephalogram. I. A Study of the Occipital Cortical Potentials in 500 Normal Adults 1

“…Traces of 7.0 to 7.5 per second frequencies were found in the records of 125 out of the series of 500 subjects, but only in 4 individuals was there more than 5 per cent of such slow activity in the 2-minute recording; of these 4 individuals, 1 had 19 per cent slow activity, 2 had 9 per cent, and 1 had 6 per cent.…”

Computer-assisted sleep staging

“…In the earlier years, many researchers used variants of the Dement and Kleitman standard [8] to stage sleep automatically. Itil et al [9] used period analysis to classify 1-min epochs based on the Loomis et al [10] classification. Johnson et al [11] presented a spectral analysis study of the EEG in different stages which was subsequently used by Larsen and Walter [12] to develop an automated staging technique based on multiple-discriminant analysis.…”