Estimates of the convergence of association projections from area 17 to rostral area 18 in the cat depend on injection site size.
To estimate the degree of convergence of corticocortical projections from area 17 to the rostral part of area 18 in the cat, we injected the retrograde tracer diamidino yellow either at single or multiple adjacent sites in area 18. We measured the diameters of the individual or larger composite injections and the diameters of the labelled regions in area 17; from these values we estimated convergence factors. Small injections led to underestimates of the overall convergence of this pathway. A maximal value for convergence (about 3 mm) was obtained with larger composite injections (above about 3 mm in diameter). These results indicate that some area 17-to-18 projections may arborize widely in area 18. Their detection may require that injected tracer covers a large portion of their arbors.
Price
D J
DJ
Department of Physiology, University Medical School, Edinburgh, UK.
Ferrer
J M
JM
D000578:Amidines / Q000008:administration & dosage* / Q000493:pharmacokinetics; D000818:Animals; D001370:Axonal Transport; D001369:Axons / Q000648:ultrastructure; D002415:Cats / Q000033:anatomy & histology*; D004396:Coloring Agents / Q000008:administration & dosage* / Q000493:pharmacokinetics; D007267:Injections / Q000379:methods*; D013238:Stereotaxic Techniques; D014793:Visual Cortex / Q000033:anatomy & histology* / Q000166:cytology; D014795:Visual Pathways / Q000033:anatomy & histology*
D000578:Amidines; D004396:Coloring Agents; C037945:diamidino yellow