Fig. 7

Fig. 7

a Summary schematic of organization by directional tuning. Hair cells in the utricular macula, left, project via afferents that maintain rostrocaudal organization but not mediolateral organization. The utricular afferent ganglion is organized rostrocaudally, but contralateral tilt sensitive afferents are intermingled. These afferents project with different patterns to distinct brainstem targets, conferring directional sensitivity in the mediolateral (escape) or rostrocaudal (VOR, posture) pathways. Colors indicate directional tuning as previously. b Summary schematic of organization by temporal kinetics. Early-born, striolar hair cells make synaptic connections to early-born afferents, whose cell bodies are positioned laterally in the utricular ganglion, and typically myelinated by the larval stage examined here. These early-born afferents, carrying phasic information about head movement, preferentially excite escape pathways, which consist of early-born, fast reticulospinal and spinal motor neurons and muscles. Postural and VOR reflex pathways rely more on the tonic and phasic-tonic signals arising from extrastriolar, slightly later-born pathways. We speculate that circuits carrying immature input, like VS_med, may project to motor circuits governing slower and more refined control of movement.