Mapping the corticoreticular pathway from cortex‐wide anterograde axonal tracing in the mouse

Abstract

The corticoreticular pathway (CRP) has been implicated as an important mediator of motor recovery and rehabilitation after central nervous system damage. However, its origins, trajectory and laterality are not well understood. This study mapped the mouse CRP in comparison with the corticospinal tract (CST). We systematically searched the Allen Mouse Brain Connectivity Atlas (© 2011 Allen Institute for Brain Science) for experiments that used anterograde tracer injections into the right isocortex in mice. For each eligible experiment (N = 607), CRP and CST projection strength were quantified by the tracer volume reaching the reticular formation motor nuclei (RF motor ) and pyramids, respectively. Tracer density in each brain voxel was also correlated with RF motor versus pyramids projection strength to explore the relative trajectories of the CRP and CST. We found significant CRP projections originating from the primary and secondary motor cortices, anterior cingulate, primary somatosensory cortex, and medial prefrontal cortex. Compared with the CST, the CRP had stronger projections from each region except the primary somatosensory cortex.Ipsilateral projections were stronger than contralateral for both tracts (above the pyramidal decussation), but the CRP projected more bilaterally than the CST. The estimated CRP trajectory was anteromedial to the CST in the internal capsule and dorsal to the CST in the brainstem. Our findings reveal a widespread distribution of CRP origins and confirm strong bilateral CRP projections, theoretically increasing the potential for partial sparing after brain lesions and contralesional compensation after unilateral injury.

Evaluating the Neural Underpinnings of Motivation for Walking Exercise

“…Unlike SMA and PMd, SFG9m is not typically considered a motor region, but this finding adds to a growing body of evidence that SFG9m may indeed be a novel motor area, or at least highly relevant to walking function. 28,29,59,60 For example, the medial prefrontal cortex (including SFG9m) was recently found to be a major origin of a key descending projection for gross motor functions like walking (the cortico-reticulo-spinal pathway). 59,60 The current study cannot determine whether SFG9m exerted any direct effects on walking through the cortico-reticulo-spinal pathway and/or indirect effects via connections with established motor regions of the cortex (M1-LL, SMA, PMd).…”

“…28,29,59,60 For example, the medial prefrontal cortex (including SFG9m) was recently found to be a major origin of a key descending projection for gross motor functions like walking (the cortico-reticulo-spinal pathway). 59,60 The current study cannot determine whether SFG9m exerted any direct effects on walking through the cortico-reticulo-spinal pathway and/or indirect effects via connections with established motor regions of the cortex (M1-LL, SMA, PMd). Given the correlational nature of this result, it is also possible that SFG9m did not exert any effects on walking (non-causal/confounded association) or that faster walking somehow led to greater SFG9m activation (reverse causality).…”

Direction-dependent neural control of finger dexterity in humans

“…The detection of relatively few anatomical correlates of finger force in the current analysis, may be methodological constrains of VLSM, which cannot detect lesion-symptom relationship outside the minimal overlap region, which included only regions within the core of MCA vascular territory which included the CST but only small part of the CRP. Additionally, CST descends in a much smaller area relative to the CRP, thus is far more vulnerable to focal damage 64,65 (compare the CST and CRP on the first and third rows, respectively). The partial dissociation of neural mechanisms controlling finger individuation and strength (depicted in Figures 3F and 4B), is reflected also in the inverse anatomical patterns of individuation and strength in flexion and extension (much more flexion-selective voxels in VLSM analysis of individuation capacity, in contrast to the existence of extension-selective but no flexion-selective brain voxels in the VLSM analysis of finger strength; Table 4).…”

“…Sensorimotor Area Tract Template (SMATT) 64 ; the cortico-reticular pathway (CRP) based on a recently published template 65 ; trajectories of association tracts based on the XTRACT atlas and template 82 . Only voxels belonging to clusters of more than 5 adjacent significant voxels are reported.…”

Advanced Temporally‐Spatially Precise Technologies for On‐Demand Neurological Disorder Intervention

“…[ 124 ] While long‐term follow‐up studies demonstrated that it was of no avail for gait disturbance, neither reduced the incidence of complications related to cognitive or emotional disorders, such as dementia and depression. [ 125 ] Notably, although the dyskinesia of PD roots in the inordinate inhibition of subcortical structures (basal ganglion, thalamus) to the motor cortex, downstream pathways including internal capsule, brain stem, and spinal cord cooperate intimately to accomplish motor reflex, [ 126 ] and the motor coordination depends on cortex‐cerebellum connection for repeat comparison and adjustment between cortical launch and downstream execution. [ 127 ] Moreover, there are intricate projections from basal ganglion to brain stem, which may account for the gait disturbance of PD.…”