Ipsilateral Afferents Research Articles

Choline acetyltransferase and acetylcholinesterase in fascia dentata following lesion of the entorhinal afferents

The perforant path (entorhino-dentate fibers) which terminates in the outer parts of the molecular layer of fascia dentata, was transected in adult rats. After 2–93 days survival, serial cryostat sections were prepared and either stained for acetylcholinesterase (AChE), cell bodies (thionin) and degenerating nerve terminals (Fink-Heimer), or freeze-dried for biochemical assay of choline acetyltransferase (ChAc), AChE and glutamate decar☐ylase (GAD). There was a 50–60% increase in the activities of ChAc and AChE per weight or volume of tissue in the molecular layer of fascia dentata, being specifically localized to the zones where the degenerating nerve terminals are found. The increase was already fully developed at 8 days survival. Simultaneously, there was a moderate increase in GAD per amount of tissue, significantly smaller than that of ChAc and AChE. The latter effect was probably caused by the shrinkage of tissue due to loss of perforant path elements. Concomitantly with these changes there was an increase in width of the AChE-poor zone in the inner part of the molecular layer, which normally contains the terminals of the commissural and ipsilateral afferents from hippocampus (CA3). Transection of the septal afferents showed that the nerve elements responsible for the increased ChAc and AChE activities were of the same origin as the cholinergic elements normally present. Transection of another important afferent route to the fascia dentata, the commissural fibers, led to no changes in AChE staining. The results indicate that in response to degeneration of the afferents from the entorhinal area there occurs a reorganization of the nerve elements in the molecular layer of fascia dentata, including a relative increase of the cholinergic nerve terminals and axons.

Ipsilateral afferents to the commissural zone of the fascia dentata, demonstrated in decommissurated rats by silver impregnation.

AbstractAn ipsilateral pathway to the commissural zone of the dentate fascia has been demonstrated in the rat using the Fink‐Heimer silver impregnation method. The pathway arises in one or both of the CA3c and CA4 hippocampal subfields. As lesions of these structures normally will cause degeneration of commissural fibers terminating in the dentate fascia, animals without commissural fibers were provided for this study. This was done by transecting the hippocampal commissures in eight day old rats which were allowed to survive until the adult stage at which time all stainable, degenerating commissural fibers had disappeared. Lesions involving the CA3c/4‐subfields were then made. The resulting degeneration in the commissural zone of the dentate fascia was shown to be of purely ipsilateral origin.Fibers of this pathway display a spread along the longitudinal septotemporal axis of the hippocampal formation. The spread in the “septal” direction (ascent) is in general greater than the descent in the temporal direction, and the more “septal” the lesion is placed, the further does the degeneration extend in the septal direction. The most ascending fibers occupy a juxtagranular position along the medial crus of the dentate granule cells. The most descending (temporal) fibers are seen superficially in the commissural zone along the lateral crus.The pyramids of CA3c and the modified pyramids of CA4 are considered the most probable cells of origin of this system.The ipsilateral system may possibly be absent in normal rats. In view of the early age at which decommissuration was carried out in the experimental animals, axonal sprouting, resulting in the appearance of fibers which may normally be absent, cannot be excluded.

A macrophysiological study of functional organization of the claustrum

The organization of somatic sensory, auditory, and visual projections to the claustrum was studied using macroelectrodes. Heterotopic and heterosensory convergence characterizes the entire claustrum. In acute experiments with cats with or without anesthesia, as well as in chronic experiments, responses differ when the stimulus or the recording site (or both) are changed. The results demonstrate that the claustrum is functionally a nonhomogeneous multisensory structure that electrophysiologically has three parts: anterior, intermediate, and posterior. The evolution of the somatic responses during different recording conditions and the examination of the somatic and auditory pathways show that the primary somatic (lemniscal) and auditory systems participate in the elaboration of the claustral activities; these pathways are at least partly independent. Somatic inflow arrives via a direct, as well as an indirect pathway from the nucleus ventralis posterolateralis of the thalamus. The direct pathway carries the impulses responsible for the relatively invariable components. The components which are sensitive to the recording conditions are mediated in part by the indirect pathway which reaches the claustrum after a cortical detour in area SII and in part by the extralemniscal system. Ipsilateral afferents have a double crossed pathway. Auditory inflow reaches the claustrum after a relay in the MG of the thalamus and after a cortical detour in area AI. Evidence is presented suggesting that the claustrum serves as a relay for the afferents to the amygdaloid complex.

Splanchnic afferents on the cerebral cortex of the cat

1. The areas of representation of the splanchnic nerve were investigated in the following cortical areas: somatic area II (ipsi-and contralteral), and somatic area I (contralateral). These areas of representation were found to be much larger than formerly reported in the literature. 2. The fibers of the Aβ-and Aγδ-group are represented differentially in these areas. The fastet fibers of the Aβ-group are primarily represented in the contralateral somatic area II. The ipsilateral area II receives afferent impulses from the entire range of the Aβ-fibers, and probably also from the Aγδ-fibers. In the contralateral somatic area I, there is probably no representation of the fastest fibers of the Aβ-group. Otherwise all other fibers sizes of the Aβ-group and the Aγδ-fibers are represented. 3. Of all the pathways leading to the different cortical areas, the pathway to the contralateral somatic area II transmits with the greatest strength. 4. The Aβ afferentś of the splanchnic nerve interfere at a supraspinal level with afferents of the ipsilateral radial superficial nerve and with afferents of the contralateral splanchnic nerve. Thus, there exists a dominance of the somatic afferents (radial nerve) over the visceral afferents, and a dominance of the contralateral over the ipsilateral afferents of the splanchnic nerves.

Differential Course and Organization of Uncrossed and Crossed Long Ascending Spinal Tracts

The uncrossed and crossed spinal tracts differ in two respects: (1) uncrossed tracts are located dorsally of the crossed tracts; (2) uncrossed tracts are polysynaptically activated only from ipsilateral nerves and crossed tracts both from contralateral and ipsilateral nerves. Tracts activated monosynaptically from ipsilateral afferents are uncrossed and tracts activated monosynaptically from contralateral afferents are crossed at the spinal level. Recording from fascicles dissected at the cervical level has revealed that the borderline between uncrossed and crossed tracts varies according to the spinal cord level and the segmental origin of the tracts. The borderline between uncrossed and crossed hindlimb tracts has shifted dorsally at the cervical level when compared with the lumbar level. Afferents belonging to sacral roots differ from afferents in most other segments by terminating not only ipsilaterally but also contralaterally in the grey matter.

Organization of Ascending Tracts in the Spinal Cord of the Frog

AbstractDischarges evoked in ascending spinal tracts on stimulation of the sciatic nerve were recorded from dissected fascicles of the cord. As in mammals and birds dorsally located tracts are activated monosynaptically only from ipsilateral afferents, whereas ventromedially located tracts are activated monosynaptically only from contralateral afferents. It is concluded that the former tracts are uncrossed and the latter tracts crossed at the spinal level. The overlapping of the areas containing uncrossed and crossed tracts is much larger in the amphibian than in the mammalian and avian cords. The fastest fibres of the ascending tracts have a conduction velocity of about 10 m/sec.

Location, course, and characteristics of uncrossed and crossed ascending spinal tracts in the cat.

AbstractHolmqvist, B. and O. Oscarsson. Location, course, and characteristics of uncrossed and crossed ascending spinal tracts in the cat. Acta physiol. stand. 1963. 58. 57—67. — Discharges evoked in coarsefibred ascending spinal tracts on stimulation of muscle and skin nerves in the hindlimbs and on stimulation of lumbar, sacral, and caudal dorsal roots, were recorded from dissected fascicles of the cord at L1 and C3. Tracts in the dorsal part of the lateral funiculus are monosynaptically activated only from ipsilateral afferents and tracts located ventrally thereof only from contralateral afferents (exceptional findings on stimulation of the most caudal roots are related to the crossing of primary afferents in these caudal segments). It is concluded that the former tracts are uncrossed and the latter crossed at the spinal level. — There is no obvious segmental lamination of fibres within the areas of uncrossed and crossed tracts. Individual tracts occupy relatively fixed and well defined areas independent of their level of origin. There is a marked dorsal shift of the dorsal and ventral spinocerebellar tracts during their ascent in the cord.

Ipsilateral afferents to the hippocampal formation in the albino rat. I. Cingulum projections.

Journal of Comparative NeurologyVolume 113, Issue 1 p. 1-41 Article Ipsilateral afferents to the hippocampal formation in the albino rat. I. Cingulum projections Lowell E. White Jr., Lowell E. White Jr. Anatomical Institute, University of Oslo, Oslo, Norway Fellow of the John Simon Guggenheim Memorial Foundation. Division of Neurosurgery, University of Washington School of Medicine, Seattle, Washington.Search for more papers by this author Lowell E. White Jr., Lowell E. White Jr. Anatomical Institute, University of Oslo, Oslo, Norway Fellow of the John Simon Guggenheim Memorial Foundation. Division of Neurosurgery, University of Washington School of Medicine, Seattle, Washington.Search for more papers by this author First published: August 1959 https://doi.org/10.1002/cne.901130102Citations: 72 AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume113, Issue1August 1959Pages 1-41 RelatedInformation