Neurovascular transduction

What is neurovascular transduction?

The term ‘neurovascular transduction’ is often used to describe the transduction of sympathetic nerve activity to regional vascular responses.

The transduction toolkit supports the calculation of neurovascular transduction using beat by beat measurements of muscle sympathetic activity (MSNA) and blood pressure.

Parameter outputs

ParameterDefinition
Transduction gainDetermines the slope relating MSNA burst area and the change in diastolic blood pressure as described in Briant et al., 2016.
R2Coefficient of determination relating the slope between MSAN burst area and the change in diastolic blood pressure.

Control definitions

ParameterDefinition
Nerve signal selectDefines the channel that corresponds to the integrate MSNA neurogram. Please ensure accurate channel labelling during Aggregate.
Corruption thresholdThreshold on first derivative of the raw neurogram for deciding that a R-R interval is corrupted by large instantaneous changes characteristic of transient noise spikes and muscle twitch artifacts.
Rise thresholdThreshold for determining what constitutes a valid burst in the neurogram. The criteria for burst identification is based on amplitudes and slopes of rise and fall of candidate bursts compared against critical values (1). The height, rise slope, and fall slope are scaled proportionally such that if 2 of the 4 criteria are met, the area surrounding the burst is set to zero, creating a beat-by-beat detected neurogram.
Pressure bin sizeSize of bins for grouping diastolic blood pressures. Default is 3 mmHg.
N1, N2MSNA burst area is most correlated
with diastolic blood pressure when it precedes it by a given lag. Bryant et al., report that the optimal gain is obtained for 8–6 cardiac cycles (i.e. N1=8, N2=6). These parameters can be altered provided N1>N2.
Regress rawIf ON the regression is based on the raw summed data. If OFF (the default) it is based on the binned MSNA data, weighted by the number of points in each bin.
Remove artefactsRemoves MSNA signal artefacts.
Burst areaSelects the method for calculating burst areas. No criterion = Areas of all the bursts; Criterion = areas of al the bursts, but zero if it has been decided that there is no burst.
BRS methodSelects the method for calculating BRS slopes.

1 = plots the y-axis as the mean MSNA area/heart beat vs. diastolic blood pressure bins.

2 = same as option 1 but slopes are statistically weighted by the number of times that a particular value occurs.

3 = plots the y-axis as the burst count (Pulse area is ignored) vs. diastolic blood pressure bins.

4 = same as option 3 but slopes are statistically weighted by the number of times that a particular value occurs. This technique is equivalent to technique described by Kienbaum et al., 2001.

Graph definitions

GraphDefinitions
Integrated nerve inputx-axis is time in seconds.

y-axis is integrated MSNA neurogram.
Burst area (criterion)x-axis is time in seconds.

y-axis is the burst area in %*s with/without criterion applied.
Baroreflex sensitivityx-axis is diastolic blood pressure in mmHg.

y-axis is AIU/heart beat (BRS method 1 or 2), or bursts/100 heart beats (method 3 or 4).
Burstsx-axis is time in seconds.

y-axis is burst amplitude.

References

(1) Hamner JWTaylor JA. Automated quantification of sympathetic beat-by-beat activity, independent of signal quality.  2001 Sep;91(3):1199-206.

(2) Kienbaum PKarlssonn TSverrisdottir YBElam MWallin BG.Two sites for modulation of human sympathetic activity by arterial baroreceptors? 2001 Mar 15;531(Pt 3):861-9.

(3 )Briant LJBurchell AERatcliffe LECharkoudian NNightingale AKPaton JFJoyner MJHart EC 2016 Sep 1;594(17):4753-68. doi: 10.1113/JP272167. Epub 2016 Jul 3. Quantifying sympathetic neuro-haemodynamic transduction at rest in humans: insights into sex, ageing and blood pressure control.

Statistics

The statistics toolkit calculates basic summary measures for all specified data channels in Ensemble.