Intergeniculate leaflet and ventral lateral geniculate nucleus afferent connections: An anatomical substrate for functional input from the vestibulo‐visuomotor system

Abstract

The intergeniculate leaflet (IGL) has widespread projections to the basal forebrain and visual midbrain, including the suprachiasmatic nucleus (SCN). Here we describe IGL-afferent connections with cells in the ventral midbrain and hindbrain. Cholera toxin B subunit (CTB) injected into the IGL retrogradely labels neurons in a set of brain nuclei most of which are known to influence visuomotor function. These include the retinorecipient medial, lateral and dorsal terminal nuclei, the nucleus of Darkschewitsch, the oculomotor central gray, the cuneiform, and the lateral dorsal, pedunculopontine, and subpeduncular pontine tegmental nuclei. Intraocular CTB labeled a retinal terminal field in the medial terminal nucleus that extends dorsally into the pararubral nucleus, a location also containing cells projecting to the IGL. Distinct clusters of IGL-afferent neurons are also located in the medial vestibular nucleus. Vestibular projections to the IGL were confirmed by using anterograde tracer injection into the medial vestibular nucleus. Other IGL-afferent neurons are evident in Barrington's nucleus, the dorsal raphe, locus coeruleus, and retrorubral nucleus. Injection of a retrograde, trans-synaptic, viral tracer into the SCN demonstrated transport to cells as far caudal as the vestibular system and, when combined with IGL injection of CTB, confirmed that some in the medial vestibular nucleus polysynaptically project to the SCN and monosynaptically to the IGL, as do cells in other brain regions. The results suggest that the IGL may be part of the circuitry governing visuomotor activity and further indicate that circadian rhythmicity might be influenced by head motion or visual stimuli that affect the vestibular system.

Vestibular loss disrupts daily rhythm in rats

“…Despite the paucity of evidence of a monosynaptic connection, one main indirect neuronal pathway has been shown to exist from the vestibular nuclei to the SCN. Vestibular inputs have been shown to be relayed by the intergeniculate leafet (IGL) nucleus through the geniculohypothalamic tract, where both photic and nonphotic stimuli influence circadian rhythmicity (29).…”

Spatial and temporal requirements for sonic hedgehog in the regulation of thalamic interneuron identity

“…4A) (Vue et al, 2007). Thalamic neurons derived from pTH-R progenitors are thought to contribute to two dorsolaterally positioned thalamic nuclei, the ventrolateral geniculate nucleus (vLG) and the intergeniculate leaflet (IGL), neither of which projects axons to the cerebral cortex (Horowitz et al, 2004;Morin and Blanchard, 2005;Vue et al, 2007;Jones, 2007). We examined first the expression of thalamic progenitor markers at E12.5 and observed that genes expressed in the pTH-R domain (Nkx2.2, Gsx1, Ascl1, Tal1) were partially reduced in Shh SBE1/SBE1 embryos and almost completely downregulated in Shh SBE1/-mutants ( Fig.…”

“…The rostral population of thalamic progenitors, pTH-R, consists of a narrow band of cells sandwiched between pTH-C and the zli. Thalamic neurons derived from pTH-R progenitors are thought to contribute to two dorsolaterally positioned thalamic nuclei with incompletely understood functions: the ventrolateral geniculate nucleus (vLG) and the intergeniculate leaflet (IGL), neither of which projects axons to the cortex (Horowitz et al, 2004;Morin and Blanchard, 2005;Vue et al, 2007;Vue et al, 2009;Jones, 2007).…”

Intrinsically Photosensitive Retinal Ganglion Cells

“…APTd anterior pretectal nucleus dorsal division; BNST bed nucleus of the stria terminalis; CPT commissural pretectal nucleus; DLG dorsal lateral geniculate nucleus; DMH dorsomedial hypothalamic nucleus; DR dorsal raphe nucleus; IGL intergeniculate leaflet; LH lateral hypothalamic area; LPO lateral preoptic area; LP lateral posterior thalamic nucleus; MeA medial amygdaloid nucleus; MnR median raphe nucleus; MPO medial preoptic area; MPT medial pretectal nucleus; NOT nucleus of the optic tract; OPT olivary pretectal nucleus; OT optic tract; PAG periaqueductal gray; PLi posterior limitans thalamic nucleus; PPT posterior pretectal nucleus; Rch retrochiasmatic area; RHT retinohypothalamic tract; SC superior colliculus; SCN suprachiasmatic nucleus; sPVz subparaventricular zone; VLG ventral lateral geniculate nucleus; VLPO ventral lateral preoptic nucleus. Based on (Morin et al 1992;Blanchard 1997, 1998;Hattar et al 2002;Gooley et al 2003;Horowitz et al 2004;Hattar et al 2006;Ecker et al 2010 . 2002, 2006).…”