The Dendronotus and Melibe paper in Current Biology

My latest paper appeared in Current Biology!

Different Roles for Homologous Interneurons in Species Exhibiting Similar Rhythmic Behaviors

This paper describes the differences in synaptic properties and organization of the swim CPGs in closely-related nudibranch species, Melibe leonina and Dendronotus iris. These animals show very similar swimming behaviors with left-right body flexions. However, their CPGs have quite different network organization; they have different synaptic connectivity and responded differently when perturbed by current injections. Thus, similarity in species-typical behavior is not necessarily predictive of common neural mechanisms.



We also discuss about how species-specific behaviors have developed through the animal evolution. We showed that, even though closely-related animals with similar neuronal architectures exhibit similar behaviors, some degree of divergence can be found in the underlying neural circuitry. A pair of homologous neurons in one species have regulatory role to modify the motor rhythm, whereas in the other species they are part of the CPG and reinforce the rhythm regularity. We don't know what is the functional significance; maybe such difference will be hidden until some time when it becomes more critical in the face of some environmental perturbations.

Plateau potentials in sacrocaudal motoneurons of chronic spinal rats, recorded in vitro

David J. Bennet, Yunru Li, and Merek Siu
J. Neurophysiol. 86, 2001

Jerky limb movements often develop after spinal cord injury. This general spasticity syndrome is caused at least in part by enhanced plateau potentials in the MNs. Depolarization in MN triggers the plateau potential and causes its sustained firing, which lead to exaggerated muscle contraction. This paper describes the basic properties of this plateau potential and the sustained firing in MNs after spinal cord transection. The recurrent GABAergic and Glycinergic inhibitions may play a role in suppressing this enhanced plateau potential. This will be studied in following paper.