Telencephalic projections to the nucleus of the basal optic root and pretectal nucleus lentiformis mesencephali in pigeons

Abstract

In birds, the nucleus of the basal optic root (nBOR) of the accessory optic system (AOS) and the pretectal nucleus lentiformis mesencephali (LM) are involved in the analysis of optic flow and the generation of the optokinetic response. In several species, it has been shown that the AOS and pretectum receive input from visual areas of the telencephalon. Previous studies in pigeons using anterograde tracers have shown that both nBOR and LM receive input from the visual Wulst, the putative homolog of mammalian primary visual cortex. In the present study, we used retrograde and anterograde tracing techniques to further characterize these projections in pigeons. After injections of the retrograde tracer cholera toxin subunit B (CTB) into either LM or nBOR, retrograde labeling in the telencephalon was restricted to the hyperpallium apicale (HA) of the Wulst. From the LM injections, retrograde labeling appeared as a discrete band of cells restricted to the lateral edge of HA. From the nBOR injections, the retrograde labeling was more distributed in HA, generally dorsal and dorso-medial to the LM-projecting neurons. In the anterograde experiments, biotinylated dextran amine (BDA) was injected into HA and individual axons were reconstructed to terminal fields in the LM and nBOR. Those fibers projecting to the nBOR also innervated the adjacent ventral tegmental area. However, tracing of BDA-labeled axons revealed no evidence that individual neurons project to both LM and nBOR. In summary, our results suggest that the nBOR and LM receive input from different areas of the Wulst. We discuss how these projections may transmit visual and/or somatosensory information to the nBOR and LM.

Pretectal projections to the oculomotor cerebellum in hummingbirds (Calypte anna), zebra finches (Taeniopygia guttata), and pigeons (Columba livia)

“…For example, Vega‐Zuniga et al () found that some cells in the LPC of chickens extend their dendrites into LMm, leading to the possibility that CR+ cells in the LPC of zebra finches and hummingbirds might still be retino‐recipient (Vega‐Zuniga et al, ). Additionally, the LPC and LMm share several inputs, including inputs from the ventral geniculate nucleus (GLv) and the adjacent nucleus intercalatus thalami (ICT; Vega‐Zuniga et al, ; Vega‐Zuniga, Trost, Schicker, Bogner, & Luksch, ), as well as the visual wulst (Wylie, Ogilvie, Crowder, Barkley, & Winship, ). This suggests a functional link among these regions, but further study of the functional response properties of LPC and LMm neurons is required.…”

Spatiotemporal frequency and speed tuning in the owl visual wulst

“…These two structures are involved with the analysis of optic flow resulting from self‐motion and with the generation of compensatory motor behaviours like the optokinetic response that facilitates retinal image stabilization (for reviews see Simpson, 1984; Grasse & Cynader, 1990). They also receive a projection from the visual wulst (Wylie et al. , 2005).…”

Programmed Acute Electrical Stimulation of Ventral Tegmental Area Alleviates Depressive-Like Behavior

“…This being said, we would like to note that within the framework of our limited experiment we were able to improve our technique of electrode implantation and stimulation to such a degree that nearly all animals succeed in recovering from the procedure (2 of 20 animals succumbed to the surgical process but this was likely due to anesthesia complications). Furthermore, in light of the physiological relationship between the VTA and oculomotor functions (Wylie et al, 2005), it is important to note that no ocular abnormalities were observed. There is of course a need to be cautious in drawing inference from our success in performing the procedure in an animal model to the possibility of succeeding similarly with human subjects.…”