The primate reticulospinal tract, hand function and functional recovery

Abstract

The primate reticulospinal tract is usually considered to control proximal and axial muscles, and to be involved mainly in gross movements such as locomotion, reaching and posture. This contrasts with the corticospinal tract, which is thought to be involved in fine control, particularly of independent finger movements. Recent data provide evidence that the reticulospinal tract can exert some influence over hand movements. Although clearly secondary to the corticospinal tract in healthy function, this could assume considerable importance after corticospinal lesion (such as following stroke), when reticulospinal systems could provide a substrate for some recovery of function. We need to understand more about the abilities of the reticular formation to process sensory input and guide motor output, so that rehabilitation strategies can be optimised to work with the innate capabilities of reticular motor control.

Sprouting of Brainstem–Spinal Tracts in Response to Unilateral Motor Cortex Stroke in Mice

“…5F). Functional implications of this increased projection (e.g., with respect to progressive poststroke flexor-tone) remain to be elucidated (Bach and Magoun, 1947;Welmer et al, 2010). The oral spinal trigeminal nucleus on the right side on average increased its projections to the left, stroke-affected hemicord whereby this response was variable across individual animals and absolute numbers of labeled cells remained low ( Fig.…”

Organization of pontine reticulospinal inputs to motoneurons controlling axial and limb muscles in the neonatal mouse

“…Thus we distinguish two pontine reticulospinal pathways to spinal MNs, one uncrossed and the other crossed, of which the uncrossed pathway transmits more faithfully and appears to be more direct. motor control; descending pathways; brain stem; spinal cord; trunk; limb THE MAMMALIAN RETICULOSPINAL system, consisting of the mesencephalic, pontine, and medullary reticulospinal pathways, is crucial for the control of skeletal musculature (Baker 2011;Kuypers 1964;Lemon 2008;Perreault and Glover 2013;Peterson 1979;Pettersson et al 2007), but the neural mechanisms by which it initiates and regulates movement are far from understood.Electrical stimulation has been a key method in studying the organization of the mammalian reticulospinal system, revealing excitatory reticulospinal connections (mono-and polysynaptic) with axial motoneurons (MNs), proximal and distal limb MNs, and digit MNs in a variety of species (monkey: Davidson and Buford 2006;Riddle et al 2009; cat: Drew and Rossignol 1990b;Galea et al 2010;Grillner et al 1968;Jankowska et al 2003;Lloyd 1941;Peterson et al 1979;Sprague and Chambers 1954;Wilson and Yoshida 1969; rat: Bolzoni et al 2013; Floeter and Lev-Tov 1993;Umeda et al 2010; and mouse: Alstermark and Ogawa 2004;Szokol et al 2008). However, many studies have not differentiated among different areas of the reticular formation (RF) that project to the spinal cord.…”

“…Thus we distinguish two pontine reticulospinal pathways to spinal MNs, one uncrossed and the other crossed, of which the uncrossed pathway transmits more faithfully and appears to be more direct. motor control; descending pathways; brain stem; spinal cord; trunk; limb THE MAMMALIAN RETICULOSPINAL system, consisting of the mesencephalic, pontine, and medullary reticulospinal pathways, is crucial for the control of skeletal musculature (Baker 2011;Kuypers 1964;Lemon 2008;Perreault and Glover 2013;Peterson 1979;Pettersson et al 2007), but the neural mechanisms by which it initiates and regulates movement are far from understood.…”

Proximal arm kinematics affect grip force-load force coordination

“…Previous studies on spinal cord injury patients found that intermuscular coherence in ␣-band may be spinal in origin (Norton et al, 2003(Norton et al, , 2004. On the other hand, a recent study suggested that ␥-band coherence may represent inputs from subcortical pathways, such as the reticulospinal and/or rubrospinal tracts (Nishimura et al 2009), which play an important role in motor control of various functional hand movements (Baker 2011). ␥-Band corticomuscular coherence was also found to increase specifically during strong isometric grip exertions (Brown 2000).…”

“…Different arm configurations involve different levels of energy expenditure, which may affect motor planning of the UE dynamics , including grip force production. Change in the proximal joint use may differently excite/ inhibit multijoint spinal/subcortical pathways used during voluntary arm movements (e.g., Bullock et al 1988) that could also affect hand muscle use (Baker 2011). Alternatively, grip force production may be affected by involuntary coupling between distal and proximal UE muscles during planning (d'Avella et al 2006;Santello et al 1998) or execution (Lee et al 2014).…”