Consistency and signal strength of respiratory neuronal activity

Abstract

The concerns of this study are taxonomic. We demonstrate a defining characteristic of respiratory neuronal activity. This characteristic is the degree or size of the respiratory component in the activity of a respiratory cell. The essential feature of respiratory activity is that it occurs in phase with some portion of the respiratory cycle. Therefore, neuronal activity can be arranged within a matrix in which the columns are fractions of the respiratory cycle and the rows are breaths and, as Netick and Orem (10) have shown, this matrix can be analyzed with an analysis of variance to determine whether the activity contains a respiratory component. However, the analysis of variance indicates nothing about the size of a statistically significant respiratory component. We hypothesized that the size of the respiratory component in the activity of different respiratory cells differed among cells but was a stable characteristic of any given cell. The index used to quantify the degree of respiratory activity was eta 2, the proportion of the total variance of the activity of a respiratory neuron consisting of the variance occurring across fractions of the respiratory cycle. This index theoretically depends on a) the range of activity levels across a respiratory cycle and the dispersion of activity levels over this range (parameters signifying the strength of the respiratory signal) and b) the variability in the activity of the cell across breaths (a parameter signifying the consistency of the respiratory activity). Theoretically, eta 2 values can vary from 0.0 to 1.0 indicating, respectively, that none or all of the variability in the activity of a cell across breaths is accounted for by a respiratory effect. eta 2 was used to analyze the size of the respiratory component in the activity of 32 medullary respiratory neurons recorded during nonrapid eye movement (NREM) sleep in chronic cats. These different respiratory cells had activity patterns with eta 2 values ranging from 0.1 to 0.9. However, the activity of a given cell produced eta 2 values that were consistent from sample to sample. Therefore, the eta 2 value of the activity of a cell was a defining, stable characteristic of that cell. The eta 2 values of the activity of the cells were strongly correlated with the consistency of their discharge pattern from breath to breath (r x,y = 0.975).(ABSTRACT TRUNCATED AT 400 WORDS)

Regulation of Ventral Surface Chemoreceptors by the Central Respiratory Pattern Generator

“…However, our previous study of RTN neurons underestimated RTN respiratory modulation for three reasons. Respiratory modulation was previously gauged using the 2 index (Orem and Dick, 1983), a less sensitive index than perievent histograms. We previously explored lower levels of CO 2 at which respiratory modulation is modest.…”

Tonic and Phasic Respiratory Drives to Human Genioglossus Motoneurons During Breathing

“…In one study of a small number of GG motor units in humans, Tsuiki and colleagues (2000) found units discharged during inspiration or both inspiration and expiration (see also Bailey et al 2005;and in rats, John et al 2005). However, no formal classification procedures were applied as used in other animal studies (Orem and Dick 1983). We hypothesized that there would be different populations of motoneurons with different firing properties that make up the overall pattern of human GG activity during respiration.…”

Precise rhythmicity in activity of neocortical, thalamic and brain stem neurons in behaving cats and rabbits

“…The database for this study was a subset from the databases used for our previously published studies [6,7,8,9,49,50,60]. The selection of the neurons and neuronal populations for this study was based on the duration of available spike trains (4000-65000 spikes).…”

“…The discharge of all the neurons was modulated to the rhythm of respiration. The measure of neuron involvement in respiration, η 2 [49], was in the range 0.5-0.9, for all neurons, except RM11 (η 2 = 0.12). The preferred phase of 67% of them was in the inspiratory phase of the cycle.…”

“…The relation of spike activity of these neuronal populations to locomotion and respiration we have described in a series of separate reports: [6] -cat ventrolateral thalamus; [7] -cat parietal cortex; [9,60] -cat motor cortex; [8] -rabbit motor cortex; [49,50] -cat respiratory medulla. The database for this study was a subset from the databases used for the above published studies.…”