Evidence for a laminar organization of basal forebrain afferents to the visual cortex

The present study shows that restriction of HRP injections to layer I within the visual cortex results in negligible retrograde labeling within the nuclei of the basal forebrain. In contrast, when the injections of either HRP or WGA-HRP are restricted to the granular and infragranular layers of visual cortex, extensive retrograde labeling occurs within the basal forebrain. Based upon these findings, we argue that the projection from the basal nucleus terminates preferentially within the deep layers of the visual cortex, and thus contributes minimally to the supragranular layers, including layer I.