A simple method for recording and analysing circadian rhythms in man.

We describe a method for recording human rest-activity and body temperature. A small automatic cordless electronic device has been developed in order to record circadian rhythmicity of rest-activity for a period of one week. A comparable device connected to a small temperature transducer by means of a flexible probe was designed to register body temperature. These devices can register human circadian rhythms without interfering with their normal daily activity.

Effect of noradrenergic denervation on task-related visual evoked potentials in rats.

The present study examines whether destruction of the noradrenergic innervation of the forebrain interferes with the processing of sensory information in a manner that results in impaired selective attention. Electro-cortical responses to task-relevant and irrelevant stimuli were found to be sensitive indicators of the rat's attention to the stimuli. The amplitude of the response to the task-relevant stimulus increased as the rat's performance improved. The response to irrelevant flashes of light depended on the predictability of the flashes and on the rat's level of arousal. Noradrenergic denervation (with the selective neurotoxin DSP4) did not affect either the behavioural response to a visual stimulus which the rat had been trained to respond to for a food reward, or the late positive potential evoked by this stimulus. Neither did it affect the response to continuous (temporally predictable) flashes of light that were irrelevant to the task. Although the response to unpredictable flashes was also largely unaffected, we did find an additional late component in this response after DSP4 treatment. These results show that the noradrenergic innervation of the occipital cortex does not always regulate the extent to which visual stimuli are processed, but that noradrenergic neurotransmission may be activated in order to diminish excessive processing of unexpected stimuli.

Circadian rhythms in preterm infants: a preliminary study.

A method has been developed for long-term continuous recordings of several physiological variables in humans, including body movements, core temperature, heart rate and respiratory rate. This method enabled us to study circadian rhythms of body temperature and rest-activity in preterm infants. In 5 out of 9 infants (recorded at 28-34 weeks conceptional age) circadian rhythms were found in body temperature. We conclude that circadian rhythmicity is present during the early neonatal period in certain physiological variables (body temperature) but not in others (rest-activity).

A device for the maintenance of a constant body temperature, with some special features.

A device for the maintenance of constant body temperature of laboratory animals during experiments is presented. Some special features make it especially suitable for experiments in which small electrical events are to be recorded, because no 50 or 60 c/sec interference or spurious signals will occur from it, nor is the animal earthed through the apparatus. In 2 years of daily use it has proved to be a reliable and accurate working device.

An economical, semi-automatic system for measuring cellular tree structures in three dimensions, with special emphasis on Golgi-impregnated neurons.

The hardware and software of a semi-automatic system are described for the measurement of cellular tree structures in thick microscopical sections such as the process of Golgi-impregnated neurons. With this system, the morphologist--viewing the neuron directly through the microscope--measures the tree structures using three cartesian coordinates of characteristic points, e.g. centre of cell, origin of processes, bifurcation points, end points, deflection points, etc. The system requires an on-line computer, but does not demand a dedicated computer since a joy-stick generator usually drives the microscopical stage during cell tracking. A digital computer is utilized for acquisition of data, and, when needed, to return the stage to a required position. The microscope stage is coupled to three stepping motors with 0.5 micron as the smallest step. The stepping motor for movement of the stage parallel to the optical axis (z-direction) is coupled directly to a spindle mechanism, replacing the original cog wheel mechanism. This construction shows no measurable backlash. The practical advantages of this new measuring system in relation to the existing digital systems currently in use, its accuracy and its costs, are discussed.