Neural Circuits and Systems Neuroscience
Author: Graciela Ines Kearney | email: graciela.kearney@gmail.com
Graciela Ines Kearney 1°, Lidia Szczupak 1°
1° Instituto de Fisiología, Biología Molecular y Neurociencias (UBA-CONICET)
In animal motor behaviors, the segments along the antero-posterior axis perform movements in a coordinated manner. Leeches are an outstanding model to analyze the underlying neuronal network controlling this function because the 21 segments that compose the body are virtually identical, simplifying the question on intersegmental coordination to that on interactions among iterated units. Leeches crawl over solid surfaces through successive elongation and contraction body waves. Each segment bears all the neurons required to produce this rhythmic motor pattern and dopamine evokes fictive crawling in isolated midbody ganglia. Coordinated rhythmic motor pattern can be also elicited in chains of 3 ganglia. The pattern of activity in both experimental conditions is highly similar, and fits behavioral parameters. Within the chain, the intersegmental interactions give rise to a global network, turning each segmental circuit refractory to local perturbations. To analyze the nature of these intersegmental signals, we used a chamber that allows chemical compartmentalization of the chain. Application of dopamine in a single ganglion elicited crawling in anterior and/or posterior ganglia. These results show that local crawling oscillators provide excitatory drive bidirectionally, which operates tonically upon neighboring circuits spreading the rhythmic activity.