Motoneurone synchronization for intercostal and abdominal muscles: interneurone influences in two different species

Figures

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  Fig. 1. Raw data from a cat experiment. a Schematic of the recording set-up. The efferent discharges in the 6 nerves (p)–(u) were used for measurements of motoneurone synchronization by cross-correlation. The 7th nerve (v), the external intercostal nerve at T5 or T6, was used as a marker of central inspiration. b A typical recording from these 7 nerves. (p)–(r) Three branches of the internal intercostal nerve at T8: (p) the lateral branch, innervating external abdominal oblique; (r) the distal remainder; (q) the first filament (Sears 1964a). (s)–(u) Three branches of L1 ventral ramus: (s) the lateral branch, innervating external abdominal oblique; (t) a branch innervating internal abdominal oblique; (u) a distal remainder

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  Fig. 2. Raw data and spike selection from a rat experiment. The four lowest traces show efferent discharges recorded from the indicated nerves. The continuous (green) horizontal lines show the thresholds (positive-going) for registering spikes as events. The large spikes in the top trace (EBSN recording) were used in this recording for identifying periods designated as expiration, using the threshold (negative-going) indicated by the interrupted (red) line. The large spikes in the lowest trace, with their threshold (positive going) indicated by the interrupted (red) line, were used for identifying periods designated as inspiration. See text for more details. α-chloralose anaesthesia

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  Fig. 3. Examples of cross-correlation histogram peaks from the cat experiments with a variety of durations and timings. a, c, e Raw histograms. b, d, f Same histograms after smoothing (5-point triangular filter). a, b T9EO/T9Fil. c, d L1IO/L1Dist. e, f T8Dist/L1IO. The peak in f is annotated to show the parameters measured: the baseline, m; the amplitude of the peak, usually expressed as k, the peak count (upper horizontal line) divided by m; the half-width (time between the arrows); the lag to the peak (lag of the vertical line)

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  Fig. 4. Distinguishing between short-term synchronization (STS) and broad-peak synchronization. Cross-correlation histograms from one pair of nerves (T8Fil/T8Dist) in one cat experiment. a, c The histogram derived from data during the whole experiment, shown at two different lag scales. b, d The same two plots after smoothing. e, f Smoothed histograms derived from data early (e) and late (f) in the experiment. Note the narrow peak (STS) is largely constant, but the underlying broad peak varies

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  Fig. 5. Amplitudes and occurrence of histogram peaks for the cat data. Values of k are plotted for each of the nerve pair categories, as indicated. T8*/T9* (third line) includes two examples of T8EO/T9Fil plus one each of T8Fil/T9Lat, T8EO/T9Dist, and T8Dist/T9Lat. The vertical bars indicate the median for the individual values shown by the points on each line. The right-hand column shows the proportion of experiments yielding a histogram with a significant peak, compared to the total tested for that category. The three ipsi-segmental thoracic nerve pair categories (lines 4–6) include four examples that were actually from T9

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  Fig. 6. More properties of the same histogram peaks summarized in Fig. 5. a values of half-width (same format as Fig. 5). Lines join points from two particular experiments, to show that the low values for T8/L1EO categories do not represent generally low values for those individual preparations. Vertical line indicates half-width value of 2.3 ms. b values for the lags to the peaks

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  Fig. 7. Relationships between lags and half-widths for T8/L1 histogram peaks. Different nerve pair categories, as indicated. Regression analysis showed a significant positive correlation for the T8EO/L1IO and T8EO/L1Dist categories

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  Fig. 8. Examples of cross-correlation histograms from pairs of Int nerves in rat experiments. Pairs of histograms, each pair from a single recording, the upper histograms from expiration, the lower ones from inspiration. a Anaesthetized animal (T9Int/T10Int, data illustrated in Fig. 2). b Decerebrate (T9Int/T10Int), flanking troughs present in the histogram from expiration, but not from inspiration. c Decerebrate (T10Int/T11Int), flanking troughs for both. d Distributions of the values of k and half-width for all of the significant peaks from Int/Int nerve pairs. Lines join values from the same recordings in expiration and inspiration. The occurrence of flanking troughs indicated by symbols (“Maybe” means that the baseline noise in the histogram from inspiration could have hidden troughs of equivalent amplitude to those seen in the histogram for expiration)

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  Fig. 9. Examples of cross-correlation histograms from Ext/Int nerve pairs in rat experiments. Pairs of histograms, each from a single recording, the upper ones from expiration, the lower ones from inspiration. a Anaesthetized animal (T9Ext/T9Int, data illustrated in Fig. 2). b–f Decerebrate: b, c T9Ext/T9Int; d T10Ext/T10Int. e T9Ext/T10Int, same recording as (b); f T9Ext/T10Int, same recording as (c)

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  Fig. 10. Examples of cross-correlation histograms with T6 Ext paired with other Ext nerves in rat experiments. a T6/T9: upper histogram, expiration; lower histogram inspiration. b–d inspiration only: b T6/T8; c T6/T9; d T6/T10. b anaesthetized; others, decerebrate

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  Fig. 11. Examples of cross-correlation histograms with T6 Ext paired with caudal Int nerves in rat experiments. All measured in inspiration. a anaesthetized animal, T6Ext/T10Int (data illustrated in Fig. 2). b–d Decerebrates: b T6Ext/T9Int; c, d T6Ext/T10Int