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Central patterning of inspiratory activity in the neonatal period
A L Sica1, M R Gandhi, A M Steele
1Department of Pediatrics, Schneider Children's Hospital, New Hyde Park, NY 11042.
Insights
Neonatal inspiratory motoneuron synchronization involves common inputs from central pattern generators, manifesting as medium and high-frequency oscillations. A medium-frequency generator appears to be active beyond the neonatal period.
Area of Science:
- Neuroscience
- Respiratory Physiology
Background:
- Neonatal inspiratory motoneuron synchronization is crucial for breathing.
- Central pattern generators (CPGs) are hypothesized to provide common inputs.
Purpose of the Study:
- To investigate the oscillatory patterns in neonatal phrenic and hypoglossal nerve discharges.
- To determine if these oscillations originate from common CPG inputs.
- To identify the frequency characteristics and temporal distribution of these oscillations.
Main Methods:
- Recording spontaneous discharges of phrenic (C5-C6) and hypoglossal nerves in neonatal swine.
- Utilizing anesthesia, decerebration, vagotomy, paralysis, and artificial ventilation.
- Performing autopower spectral and coherence analyses on neural discharges.
Main Results:
- Phrenic nerve discharges exhibited both medium (<50 Hz) and high (≥50 Hz) frequency oscillations.
- Both oscillation types were present throughout inspiration, with larger amplitudes in the second half.
- Hypoglossal nerve discharges showed only medium-frequency oscillations, indicating a common medium-frequency input to both nerves.
Conclusions:
- The findings provide strong evidence for a medium-frequency CPG influencing neonatal inspiratory motoneuron synchronization.
- This medium-frequency pattern generator may persist beyond the neonatal period.
- Differential amplitude changes suggest frequency-specific gating mechanisms during inspiration.
Abstract:
We hypothesized that synchronization of neonatal inspiratory motoneurons is achieved by common inputs from one or more central pattern generators. Such inputs are manifested in neural discharges as medium-frequency (less than 50 Hz) and/or high-frequency (greater than or equal to 50 Hz) oscillations. Furthermore, if both oscillations appeared, one or both might be gated, i.e. present only in the first or second half of inspiration. The spontaneous discharges of phrenic (C5 and C6) roots and hypoglossal nerves were recorded in anesthetized or decerebrated, vagotomized, paralyzed and artificially ventilated neonatal swine. Autopower spectral analyses showed that phrenic discharges had peaks in the medium- and/or the high-frequency band. Phrenic spectra, derived from either half of inspiration, demonstrated that, while both types of oscillation were present throughout inspiration, their amplitudes were larger during the second half of inspiration. However, comparisons of the relative distributions of power in each half of inspiration showed that the increase of high-frequency power was much larger than that of medium-frequency power during the second half of inspiration. In contrast to phrenic spectra, hypoglossal spectra had peaks only at medium-frequencies; consequently, correlated frequencies (indicative of common inputs) in phrenic-hypoglossal coherence spectra were present at those frequencies. The presence of highly correlated frequencies provided strong evidence of a medium-frequency pattern generator which may remain operative beyond the neonatal period.