Description
The nucleus isthmi(NI) is a hindbrain nucleus located in the tegmentum of rhombomere 1 close to the secondary gustatory nucleus. NI is reciprocally connected with the optic tectum. Henriques et al (2019) describe two distinct types of isthmic projection neuron that either connect ipsilaterally to retinorecipient laminae of the tectum and pretectum or bilaterally to both tectal hemispheres.
“The nucleus isthmi (NI) is thought to correspond to the parabigeminal nucleus (PBg) in mammals. These paired cholinergic nuclei are located at the midbrain-hindbrain boundary of the tegmentum and are reciprocally connected with Optic Tectum(OT) and Superior Colliculus(SC) in all vertebrates studied. The NI and PBg has been described a satellite system of OT and SC and is a good candidate to modulate tectal activity during hunting. NI and PBg has been implicated in visual prey detection, tracking of moving targets, generation of binocular visual responses in rostral OT, and mechanisms of selective spatial attention .”Henriques et al., 2019
Ablation of the nucleus ithmi results in specific deficits in tectally mediated loom-avoidance and prey-catching behavior. Ablating the NI does not affect prey detection or hunting initiation but did lead to a failure to sustain prey-tracking sequences and the abortion of larval hunting routines. Larvae show elevated neural activity in NI following onset of hunting behavior. Henriques et al (2019) propose a model in which the "nucleus ithmi provides state-dependent feedback facilitation to the optic tectum and pretectum to potentiate neural activity and increase the probability of consecutive prey-tracking maneuvers during hunting sequences." Henriques et al., 2019.
Schematic based on Henriques et al., 2019 showing the position of the nucleus isthmi at the midbrain-hindbrain boundary in the tegmentum.
Schematic based on Henriques et al., 2019 showing the nuclear subdivisions of the paired cholinergic nucleus ithmi visualised using FISH expression of the cholinergic genes chata (green) and vachtb(magenta). The Ch-A domain could be subdivided into anterior (aCh-A) and posterior (pCh-A) subregions, with the location of the boundary marked by a large fascicle from the cerebellum.
Ontology
is part of: medulla oblongata
has parts:
OLS Tree Diagram
Transgenic Lines/Antibodies that label this brain region
Key Publications
Henriques PM, Rahman N, Jackson SE, Bianco IH.
Nucleus Isthmi is required to sustain target pursuit during visually guided prey-catching.
Current Biology (2019) 29:1771-1786. doi.org/10.1016/j.cub.2019.04.064