Diversity of reticulospinal systems in mammals

Abstract

Reticulospinal (RS) neurons provide the spinal cord with the executive signals for a large repertoire of motor and autonomic functions, ensuring at the same time that these functions are adapted to the different behavioral contexts. This requires the coordinated action of many RS neurons. In this mini-review, we examine how the RS neurons that carry out specific functions distribute across the three parts of the brain stem. Extensive overlap between populations suggests a need to explore multi-functionality at the single cell-level. We next contrast functional diversity and homogeneity in transmitter phenotype. Then, we examine the molecular genetic mechanisms that specify brain stem development and likely contribute to RS neurons identities. We advocate that a better knowledge of the developmental lineage of the RS neurons and a better knowledge of RS neuron activity across multiple behaviors will help uncover the fundamental principles behind the diversity of RS systems in mammals.

Brain-wide analysis of the supraspinal connectome reveals anatomical correlates to functional recovery after spinal injury

“…Labeled nuclei were also abundant in the pontine reticular nuclei ( Leong et al, 1984 ; Liang et al, 1997 ; Figure 1—figure supplement 4B6 ). Although perhaps less well understood than medullary reticular populations, pontine reticular neurons have been linked to muscle atonia during sleep, startle responses, and to multisegment postural adjustments during limb extension ( Perreault and Giorgi, 2019 ; Takakusaki et al, 2016 ). More dorsally in the pons, labeled nuclei mapped to known supraspinal regions in and around the pontine central gray, including the locus coeruleus (LC), laterodorsal and sublaterodorsal tegmental nucleus ( Leong et al, 1984 ; Liang et al, 1997 Cornwall et al, 1990 ; Peever and Fuller, 2016 ; Sluka and Westlund, 1992 ; Figure 1—figure supplement 4B3 ).…”

The role of eutherian‐specific RTL1 in the nervous system and its implications for the Kagami‐Ogata and Temple syndromes

“…Therefore, this is highly likely to be associated with the impairment of CST, CRT, and RST because they are responsible for the voluntary muscle movement of the trunk and limbs (Lemon, 2008; Patestas & Gartner, 2016), such as specific skilled muscle movement (i.e. CST) (Iwaniuk & Whishaw, 2000) and diverse specific motor function (i.e., CRT and RST) (Perreault & Giorgi, 2019) including escape, micturition, reaching and grasping, sleep, respiration, vomiting, and locomotion. Impairment of the corpus callosum is also likely to be involved in the motor delay because it connects the right and left hemispheres and is critically involved in information exchange, especially in cortex layer V.…”

Autonomic and respiratory components of orienting behaviors are mediated by descending pathways originating from the superior colliculus

“…This is perhaps surprising, as RVLM neurons are: a major source of excitatory drive to sympathetic nerves and play a critical role in subserving a wide range of cardiovascular reflexes (Guyenet, 2006); implicated in mediating sympathetic responses to a range of physiological and psychological stressors (Abe et al, 2017; Guyenet et al, 2013; Zhao et al, 2017); and reported to receive monosynaptic input from the SC (Dempsey et al, 2017; Stornetta et al, 2015). In contrast, we found extensive arborization of cl-dSC efferents across multiple medullary reticular formation (mRF) compartments, most prominently the GiA, which is a major hub for descending control to spinal locomotor circuits (Bouvier et al, 2015; Dougherty and Kiehn, 2010; Kim et al, 2017; Perreault and Giorgi, 2019; Usseglio et al, 2020). Similar SC innervation of the mRF has been described previously in the mouse and rat (Isa et al, 2020; Redgrave et al, 1987; Usseglio et al, 2020).…”