Visual responses and afferent connections of the n. ventrolateralis thalami (VLT) in the pigeon (Columba livia)

Abstract

The nucleus ventrolateralis thalami (VLT) in pigeons receives direct retinal and forebrain projections and has reciprocal connections with the optic tectum. Although VLT is a component of the avian visual system, no study directly examined its connections or its cellular response characteristics. We, therefore, recorded from single units in the pigeon's VLT while visually stimulating the ipsi-and/or contralateral eye. In addition, tracing experiments were conducted to investigate its afferent connections. Electrophysiologically, we discovered three types of neurons, two of which were probably activated via a top-down telencephalotectal system (latencies > 100 ms). Type I neurons responded to uni-and bilateral and type II neurons exclusively to bilateral stimulation. Type III neurons were probably activated by retinal or retinotectal input (latencies < 27 ms) and responded to contra-and bilateral stimulation. Retrograde tracer injections into the VLT revealed an ipsilateral forebrain input from the visual Wulst, from subregions of the arcopallium, and bilateral afferents from the optic tectum. Most intriguing was the direct connection between the VLTs of both hemispheres. We suggest that the avian VLT is part of a system that integrates visuomotor processes which are controlled by both forebrain hemispheres and that VLT contributes to descending tectomotor mechanisms.

Afferent connections of septal nuclei of the domestic chick (Gallus domesticus): A retrograde pathway tracing study

“…In both species a small to moderate number of neurons from the nucleus subrotundus and the thalamic ventrolateral nucleus project to SL (present data, Atoji and Wild,2004). However, in another study, there is no indication of thalamic ventrolateral nucleus neurons projecting to the septum in the pigeon (Schulte et al,2006).…”

Neuroanatomical specificity in the expression of the immediate early gene c‐fos following expression of appetitive and consummatory male sexual behaviour in Japanese quail

“…Males in the CSB and ASB‐F groups also exhibited an increase in FOS expression in the visual part of the VLT, a poorly studied thalamic nucleus in birds. This nucleus appears to be involved in the integration of visual information as suggested by an electrophysiological study demonstrating the presence of evoked potentials in this nucleus following 500 ms uni‐lateral or bi‐lateral photic stimulation (Schulte et al ., 2004) and indicated by the existence of a massive projection from the visual Wulst, a major visual component of the avian thalamofugal pathway, to the VLT (Schulte et al ., 2004). Moreover, previous tracing studies have identified in quail the existence of projections from the POM to the VLT (Balthazart et al ., 1994) and from the HA to the POM (Balthazart & Absil, 1997).…”

The visual system of a Palaeognathous bird: Visual field, retinal topography and retino‐central connections in the Chilean Tinamou (Nothoprocta perdicaria)

“…7B-D, 8B) which, as in other birds, first appears at the rostral margin of the thalamus and continues to form an envelope around the LA (G€ unt€ urk€ un and Karten, 1991), and more caudally around the n. rotundus (Rt) just below the DLL. In the n. ventrolateralis thalami (VLT), which lies between the GLv and Rt and is a known retinorecipient region in birds (Schulte et al, 2006), we found only a few sparse terminals (Fig. 7D).…”