Cardiac modulation of alpha motoneuron discharges

Area of Science:

• Neuroscience
• Physiology

Background:

• Muscle spindles are known to respond to the cardiac pulse.
• It remains unclear if this cardiac signal is transmitted to higher neural levels.

Purpose of the Study:

• To investigate the presence and transmission of cardiac signals within the efferent activity of thoracic and abdominal nerves.
• To determine if muscle spindle afferents contribute to cardiac interoception.

Main Methods:

• Analysis of alpha motoneuron discharges from intercostal and abdominal nerves in anesthetized cats.
• Cross-correlation histograms between ECG R-waves and efferent spikes to assess cardiac modulation.

Main Results:

• Cardiac modulation was observed in alpha motoneuron discharges, indicated by short-duration peaks/troughs in cross-correlation histograms.
• These modulations suggest oligosynaptic pathway activity, likely from cardiac-synchronized muscle spindle afferents.

Conclusions:

• A cardiac signal, originating from muscle spindles, is present in efferent nerve activity.
• This finding suggests probable onward transmission of the cardiac signal to other central nervous system levels.
• Muscle spindles may contribute to cardiac interoception.