Topography of tecto-toral interconnections in Gnathonemus petersii. (1–3) Drawings of the three levels of the torus semicircularis documented in four rows below (R1 – R3/C1 – C3/D1 – D3/V1 – V3) each row showing toral connections after one of four tectal DiI injections (R, rostral; C, caudal; D, dorsal; V, ventral). Arrows point to labeled fields. All connections are ipsilateral. Note evident topographical relationship between lateral toral nucleus and optic tectum, also schematically visualized in top drawings 1–3 with corresponding colors. Size bar in (1): 0.5 mm, applies to all panels. See text for details. DP, dorsal posterior thalamic nucleus; DR, rostrodorsal tegmental nucleus; fr, fasciculus retroflexus; fll, lateral longitudinal fascicle; MD, mediodorsal nucleus of torus semicircularis; MV, medioventral nucleus of torus semicircularis; NE, exterolateral nucleus of torus semicircularis; NL, lateral nucleus of torus semicircularis; PD, dorsal perilemniscal part of nucleus lateralis valvulae; PGd, PGc, dorsal, caudal preglomerular nuclei; RT, rostral tegmental nucleus (of Grover and Sharma, 1981); TeO, tectum opticum; TLo, torus longitudinalis; tmc, mesencephalo-cerebellar tract; tt, toro-pre-eminential tract; VP, ventroposterior nucleus of torus semicircularis.