Fig. 1

Overview of tectum-TL circuitry and PyrN synaptic input. A Schematic dorsal view of the larval zebrafish brain B. Schematic coronal view of the larval brain at the level of anterior tectum. Note each lobe of tectum is innervated by TL and contralateral retina. C Enlarged coronal view of tectum. Note superficial input layer from TL and deeper neuropil innervated by retinal axons. D Putative tectum-TL circuitry. Contralateral retina provides synaptic input to both TLPNs and PyrNs. TLPNs send axonal projections to TL. SM-projecting TL neurons (SMTLs) form axon terminals in tectum that represent a second synaptic input onto PyrNs. E Putative circuitry that generates binocular responses in PyrNs. Transfer from one side of TL to the other is likely mediated by both TLPN axons that cross the midline of TL as well as commissural interneurons within TL. F PyrNs in tectum receive input from both ipsilateral TL and contralateral retina