Nuclear Terminations of Corticoreticular Fiber Systems in Rats; pp. 223–237

Abstract

Corticoreticular fiber systems were examined in adult albino and hooded rats using anterograde transport of wheat germ agglutinin-horseradish peroxidase (WGA-HRP) and anterograde degeneration. WGA-HRP injections were made stereotactically into the medial prefrontal cortex, the medial agranular cortex, the anterior cingulate cortex, the face motor cortex, the forelimb motor cortex, the trunk-hindlimb motor cortex, the face somatosensory cortex, the primary auditory cortex, the secondary visual cortex and the primary visual cortex. With the exception of the cingulate cortex (which is relatively inaccessible to lesioning methods) and the primary visual cortex, electrocautery lesions were made into these same cortical areas. The precise locations of cortical injection/lesion sites were corroborated on the basis of cortical cytoarchitectonic criteria, patterns of retrograde and anterograde thalamic labeling, and patterns of anterograde labeling in nonreticular brainstem nuclei such as the red nucleus, trigeminal nuclei and dorsal column nuclei.The heaviest corticoreticular projections arise from the medial agranular cortex. The medial prefrontal cortex also gives rise to consistently strong corticoreticular projections. The anterior cingulate cortex sends robust corticoreticular projections to the upper brainstem but relatively weak projections to the lower brainstem. With respect to the primary motor cortex, the face area gives rise to the densest corticoreticular projections, rivaling those emanating from the medial agranular cortex. The trunk-hindlimb area gives rise to substantial corticoreticular projections, but those originating from the forelimb area are modest and directed chiefly to midbrain and medullary levels. The face area of the somatosensory cortex gives rise to rather weak corticoreticular projections, while those arising from the primary auditory cortex are fewer still. Descending projections from the secondary visual cortex are sparse, with labeled terminals occurring in a few pontine and medullary reticular nuclei. Only one brainstem reticular nucleus (nucleus cuneiformis) was found to receive projections from the primary visual cortex, and this input was extremely sparse.Corticoreticular projections to the upper brainstem terminate predominately ipsilateral to the cortical injection site, whereas medullary corticoreticular projections distribute bilaterally. Corticoreticular fibers from the medial agranular, face motor and trunk-hindlimb motor cortex terminate heavily in somatomotor brainstem reticular nuclei such as the pontis oralis, the pontis caudalis and the gigantocellularis. Corticoreticular fibers from the prefrontal and cingulate cortices also target these nuclei but in addition send dense projections to autonomic brainstem reticular nuclei such as the A1-lateral reticular complex and the paragigantocellularis lateralis. The face area of the motor cortex projects to medullary reticular nuclei closely associated with the trigeminal system, such as the reticularis parvocellularis and the do...

Connectivity‐based segmentation of the periaqueductal gray matter in human with brainstem optimized diffusion MRI

“…The precentral gyrus demonstrates dominant connectivity to the lPAG and vlPAG, and the occipital cortex strong connectivity to the dlPAG. This is in agreement with studies in rats; where primary motor areas project exclusively to the lPAG and vlPAG, while the secondary visual cortex preferentially [Newman et al, 1989]. Furthermore, sensory cortex connectivity arose predominantly from the dlPAG and lPAG.…”

Transdural motor cortex stimulation reverses neuropathic pain in rats: A profile of neuronal activation

“…Consequently, a direct action of MCS on VPL/VPM inhibition is more likely to take place bilaterally. As described by Newman et al (1989), using anterograde tract-tracing techniques, fibers originating in the motor cortex spread into diffuse terminal fields in the ipsilateral mesencephalic reticular formation and PAG. Inter-estingly, the afferents from the motor cortex are found to maintain some topography once they reach the PAG.…”

“…Inter-estingly, the afferents from the motor cortex are found to maintain some topography once they reach the PAG. The face area projects preferentially to the ventral PAG, the forelimb area connects to its ventrolateral aspects, while the trunk-hindlimb motor area is related to the lateral part of PAG (Newman et al, 1989).…”

Autoradiographic localization of 5HT1 binding sites in the medulla oblongata of the rat

“…Neurons in these nuclei terminate on motor neurons in the ventral horn of the spinal cord and are important in maintaining postural reflexes (Holstege and Kuypers, 1987a,b). These same reticular nuclei also receive inputs from corticoreticular fibers (Newman et al, 1989). In this regard, it is interesting to note that the pyramidal tract, which contains corticoreticular and corticospinal fibers that control fine movement (Kuypers, 1982), also exhibited %-ITlB binding sites.…”