B. Hellmann et O. Gunturkun, Visual-field-specific heterogeneity within the tecto-rotundal projection of the pigeon, EUR J NEURO, 11(8), 1999, pp. 2635-2650
The organization of the tecto-rotundal projection of the pigeon was investi
gated by means of anterograde and retrograde tracing techniques. Besides th
e known organization in tecto-rotundal connectivity, this study additionall
y demonstrates major variations in the ascending projections of different t
ectal subfields. We show that the ventral tectum opticum (TO) has significa
ntly more projections onto the nucleus rotundus (Rt) than dorsal tectal are
as. This difference coincides with differential innervation densities of af
ferent fibres within rotundal subregions. While ventral tectal efferents pr
oject onto the ventral and central Rt, dorsal tectal efferents mainly arbor
ize within limited areas between the central Rt and its dorsal cap, the nuc
leus triangularis. Thus, the ventral TO, representing the lower and frontal
field of view, exhibits a quantitatively and spatially enhanced projection
onto the Rt, as compared with the dorsal TO. The data presented here demon
strate a visual field-dependent projection pattern of ascending tectal outp
uts onto different rotundal domains. The data are consistent with behaviour
al studies, demonstrating tectofugal lesions to suppress visual stimulus an
alysis mainly within the frontal field of view.