A non-intrusive method of recording the EMG of respiratory muscles with electronic suppression of the ECG artifact and averaging with a running window was employed in newborn infants at term to study respiratory patterns in different behavioural states. There are clear state-related differences in the diphragmatic and intercostal activity patterns. During most of the time in state 1 (quiet sleep) sustained tonic activity is found in the diaphragm as well as in intercostal muscles, but is virtually absent during state 2 (active sleep). During state 1 intercostal activity slightly precedes diaphragmatic activity whereas in state 2 both muscles contract about synchronously and vary widely in their amplitude. During periodic breathing the inspiratory EMG activity is absent in the pauses, but tonic activity may be present during periodic breathing in state 1. Isolated respiratory pauses with silence in the respiratory muscles occur in state 1 after sighs and starties with deep inspirations. During state 2 many respiratory pauses accompany gross movements and simultaneous laryngeal muscle activity suggests upper airway occlusion. Respiratory pauses without movements cannot be due to general alpha-motoneuron inhibition, because chin muscle activity may be seen at the same time. Gross movements often act as a reset mechanism for increase or decrease in tonic activity and phasic respiratory activity. Some speculations on the neural mechanisms of respiratory control based on the preliminary findings from the EMG recordings are mentioned.

Apnea↗

PubMed1977

Sleep state transitions in newborn infants: preliminary study.

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Electroencephalography↗

PubMed1976

Muscle activity and postural behaviour in newborn infants. A polymyographic study.

In a group of 9 healthy newborns, spontaneous activity of different muscles was studied for 6 or 8 hours by means of surface electromyography on the 5th or 6th day of life. According to the local nursing routine the infants were placed in alternating left and right side positions. Averaged EMG activities were analysed with respect to behavioural states and observed postural behaviour. An improved recording technique and the logarithmic presentation of averaged EMG activities allowed the study of characteristics of tonic activity in state 1. The chin muscles showed the most specific EMG pattern in state 1. Chin muscle quiescence was observed during only 15% of that state. Lack of tonic activity was observed more in the beginning than at the end, but never in the middle of state 1. By visual analysis of 41 patterns of averaged EMG activities from the chin muscle it was found that increases of tonic activity only happen stepwise following concomitant phasic activities. Relaxation of tonic activity is either asymptotic or abrupt or by steps. The latter two are especially characteristic for the transition to state 2. Long periods of sustained tonic activity and low motility were characteristic for a long lasting state 1. The interval between the beginning of state 1 and the first increase of tonic activity varied more than the interval between the end of state 1 and the final drop of tonic activity back to the noise level. Other muscles showed less tonic activity in state 1: the neck area (sterncleidomastoid muscle 48% of state 1 time, trapezius m. 32%) was followed by the muscles of the forearm (extensor carpi m. 18%, flexor carpi m. 16%). These muscles also lead the rank order of the modulation of tonic activity. Tonic activity sustained for more than 30 sec. was not observed in state 2, except during transitions. In state 2 as in state 1 the muscles from chin, neck and upper extremities were more active than the muscles from the lower extremities. Durations of activities ranged from 28% (chin) to 13% (ant. tibialis) of state 2 time. No dominance of flexor muscles, which might account for the observed flexed posture, was found. Systematically changed side positions during the recording had no consistent effect on either motility or presence of tonic activity when corresponding muscles from the upper- and the lower-lying body side were compared during state 1. Likewise in state 2 no consistent effect on the total duration of phasic activity was observed. The results are discussed in relation to other known state dependent motor phenomena. It is suggested that sustained tonic activity results from an increased gain of the gamma-loop which may also contribute to the regularity of respiration. Differences between muscles probably reflect maturational and functional differences.

Action Potentials↗

PubMed1976

[Minimal early childhood brain damage and the compensation capacity of the nervous system].

The concept of infantile cerebral lesion with later behavioral and learning disorders remains unclear and controversial, despite the voluminous literature on the subject. Neuropathologic data are lacking and the neurologic findings are often hard to interpret. Indirect access to this problem is provided by animal experiments in which the sequelae (neurologic and behavioral) of early and late, circumscribed cerebral lesions are compared. They have provided evidence that early--usually neonatal--lesions in particular areas of the central nervous system can be largely compensated. This may involve assumption of the function by the undamaged contralateral side, or sprouting of intact axons reinnervates denervated neurons. In this process, incorrect "switching" is not out of the question. Moreover, subcortical areas may retain their functions if cortical areas which normally take over their functions are damaged. Compensation following early lesions frequently produces intact, but biologically different, nervous systems. For this reason the behavior they generate may diverge from the norm. In many cases these deviations are apparent only in quite specific situations and otherwise remain latent.

Animals↗

PubMed1974