Projections of the densocellular part of the hyperpallium in the rostral Wulst of pigeons (Columba livia)

• Published in: Brain research Vol. 1711; pp. 130 - 139
• Main Authors: Atoji, Yasuro, Wild, J. Martin
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 15-05-2019
• Subjects: Bird; Fiber connection; Hippocampal formation; Medial striatum; Somatosensory Wulst; TT; HI; IHA; Ov; SPC; Hippocampal formation; DL; DM; CDL; dThal; MSt; NFM; NFL; MD; MI; GLd; AD; AI; MV; TSM; MIM; NC; NCL; BDA; Somatosensory Wulst; Fiber connection; DLM; E; Bird; DLP; LSt; M; N; TuO; DIVA; OB; MFM; V; Rt; Ru; OT; DMP; DIP; Medial striatum; CTB; NIM; HA; HD; HF
• ISSN: 0006-8993; 1872-6240
• DOI: 10.1016/j.brainres.2019.01.001

•Interconnections between the four layers of the Wulst (HA, IHA, HI, HD) are similar for both rostral and visual parts.•Both Wulst parts connect with the hippocampal formation via HD.•Only HD of the rostral Wulst has a connection with the olfactory system and projects upon the medial striatum.•The rostral and visual Wulst provide different extratelencephalic outputs from HA.
The Wulst in birds shows a four-layered structure: apical part of the hyperpallium (HA), interstitial part of HA (IHA), intercalated part of hyperpallium (HI), and densocellular part of hyperpallium (HD). The Wulst consists of a small rostral somatosensory region and a larger caudal visual region. The visual HD relays visual information to IHA and HA in the Wulst and also transfers visual information to the hippocampal formation (Atoji et al., J Comp Neurol 526: 146–165, 2018). However, fiber pathways of the rostral HD remain unknown. In the present study, the fiber connections of the rostral HD and overlying HI were analyzed with tract-tracing techniques using a combination of injections of cholera toxin subunit B (CTB) for retrograde tracing and biotinylated dextran amine (BDA) for anterograde tracing. When the two tracers were bilaterally but separately injected into the rostral HD, major reciprocal connections were seen with the rostral HA, prepiriform cortex, and subdivisions of the hippocampal formation. One-way projections of huge fibers also reached the medial part of the medial striatum. When CTB and BDA were bilaterally and separately injected into the rostral HI, strong reciprocal connections were found between the rostral HI and HA, and weak connections were seen with areas outside the Wulst. These results suggest that the fiber pathways of the rostral HD and HI are distinguishable from each other in the telencephalon and suggest also that the rostral HD relays information to the rostral HA and simultaneously acts as a mediator to the hippocampal formation.