A vibrissa pathway that activates the limbic system.

Michaël Elbaz,Amalia Callado Perez,David Kleinfeld,Martin Deschenes,Maxime Demers,Shengli Zhao,Conrad Foo

doi:10.7554/elife.72096

Michaël Elbaz, Amalia Callado Perez + Show 5 more

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https://doi.org/10.7554/elife.72096

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Abstract

Vibrissa sensory inputs play a central role in driving rodent behavior. These inputs transit through the sensory trigeminal nuclei, which give rise to the ascending lemniscal and paralemniscal pathways. While lemniscal projections are somatotopically mapped from brainstem to cortex, those of the paralemniscal pathway are more widely distributed. Yet the extent and topography of paralemniscal projections are unknown, along with the potential role of these projections in controlling behavior. Here, we used viral tracers to map paralemniscal projections. We find that this pathway broadcasts vibrissa-based sensory signals to brainstem regions that are involved in the regulation of autonomic functions and to forebrain regions that are involved in the expression of emotional reactions. We further provide evidence that GABAergic cells of the Kölliker-Fuse nucleus gate trigeminal sensory input in the paralemniscal pathway via a mechanism of presynaptic or extrasynaptic inhibition.

Highlights

Most sensory systems comprise parallel pathways of sensory information that encode different features of a stimulus and take part in the control of sensor motion (Merigan and Maunsell, 1993; Lomber and Malhotra, 2008; Nassi and Callaway, 2009; Niu et al, 2013; Igarashi et al, 2012)
Ascending signals in the vibrissa system travel along two main trigeminothalamic pathways: (1) a lemniscal pathway that arises from the trigeminal nucleus principalis (PrV), transits through the ventral posterior medial nucleus (VPM) of the thalamus, and projects to the primary somatosensory cortex; (2) a paralemniscal pathway that arises from the rostral part of trigeminal nucleus interpolaris (SpVIr), transits through the posterior group (Po) of the thalamus, and projects to the somatosensory cortical areas and to the vibrissa motor cortex
Collateral projections of interpolaris cells that project to Po thalamus

Summary

Introduction

Most sensory systems comprise parallel pathways of sensory information that encode different features of a stimulus and take part in the control of sensor motion (Merigan and Maunsell, 1993; Lomber and Malhotra, 2008; Nassi and Callaway, 2009; Niu et al, 2013; Igarashi et al, 2012). Ascending signals in the vibrissa system travel along two main trigeminothalamic pathways (reviewed in Prescott et al, 2016): (1) a lemniscal pathway that arises from the trigeminal nucleus principalis (PrV), transits through the ventral posterior medial nucleus (VPM) of the thalamus, and projects to the primary somatosensory cortex; (2) a paralemniscal pathway that arises from the rostral part of trigeminal nucleus interpolaris (SpVIr), transits through the posterior group (Po) of the thalamus, and projects to the somatosensory cortical areas and to the vibrissa motor cortex. In contrast with PrV cells, which innervate principally VPM thalamus, SpVIr cells that project to Po thalamus innervate a number of additional regions by means of branching axons

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