Model of intersegmental coordination in the leech heartbeat neuronal network

Area of Science:

• Neuroscience
• Computational Biology
• Systems Neuroscience

Background:

• The heartbeat of the medicinal leech (Hirudo medicinalis) is controlled by a timing network of segmental oscillators.
• Intersegmental coordination mechanisms within this network remain unclear despite known inhibitory coupling.

Purpose of the Study:

• To elucidate the mechanisms of intersegmental coordination in the leech heartbeat timing network.
• To computationally model the synchronization dynamics of coupled segmental oscillators.

Main Methods:

• Developed two computational models (symmetric and asymmetric) of the leech heartbeat timing network.
• Simulated interactions between two segmental oscillators with different inherent periods.
• Modeled the effect of inhibitory coordinating interneurons and oscillator interneurons.
• Simulated physiological experiments using external stimuli to control oscillator interneurons.

Main Results:

• The symmetric model demonstrated that faster oscillators can entrain slower ones by temporarily removing synaptic inhibition.
• In the symmetric model, the coupled system's period matched the faster oscillator's period.
• The asymmetric model showed similar behavior, with one oscillator dominating the system's period.
• Simulated external stimuli successfully entrained the entire timing network.

Conclusions:

• The computational models provide a plausible biophysical mechanism for intersegmental coordination in the leech heartbeat.
• Oscillator interneuron activity and synaptic inhibition play critical roles in synchronizing segmental oscillators.
• The models offer insights into how external stimuli can modulate rhythmic neural network activity.