TY - JOUR TI - Chronology-based architecture of descending circuits that underlie the development of locomotor repertoire after birth AU - Pujala, Avinash AU - Koyama, Minoru A2 - Thirumalai, Vatsala A2 - Calabrese, Ronald L A2 - Wyart, Claire VL - 8 PY - 2019 DA - 2019/02/25 SP - e42135 C1 - eLife 2019;8:e42135 DO - 10.7554/eLife.42135 UR - https://doi.org/10.7554/eLife.42135 AB - The emergence of new and increasingly sophisticated behaviors after birth is accompanied by dramatic increase of newly established synaptic connections in the nervous system. Little is known, however, of how nascent connections are organized to support such new behaviors alongside existing ones. To understand this, in the larval zebrafish we examined the development of spinal pathways from hindbrain V2a neurons and the role of these pathways in the development of locomotion. We found that new projections are continually layered laterally to existing neuropil, and give rise to distinct pathways that function in parallel to existing pathways. Across these chronologically layered pathways, the connectivity patterns and biophysical properties vary systematically to support a behavioral repertoire with a wide range of kinematics and dynamics. Such layering of new parallel circuits equipped with systematically changing properties may be central to the postnatal diversification and increasing sophistication of an animal’s behavioral repertoire. KW - hindbrain KW - V2a KW - descending pathways KW - locomotion KW - escape KW - spontaneous swim JF - eLife SN - 2050-084X PB - eLife Sciences Publications, Ltd ER -