How to Enhance Ipsilateral Actions of Pyramidal Tract Neurons

Jankowska, E.; Cabaj, Anna; Pettersson, L.‐G.

doi:10.1523/jneurosci.1838-05.2005

Cited by 32 publications

(46 citation statements)

References 15 publications

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“…Monosynaptic excitation of contralateral motor neurons by CINs was shown here directly for the first time, although glutamatergic CINs excited by reticulospinal neurons and projecting directly to contralateral motor neurons have been shown indirectly in adult cats (Bannatyne et al, 2003;Jankowska et al, 2003Jankowska et al, , 2005bHammar et al, 2004;Matsuyama and Jankowska, 2004). Glutamatergic dCINs have also been shown to directly excite caudal, contralateral motor neurons in neonatal rats (Butt and Kiehn, 2003).…”

Section: Excitatory Cinsmentioning

confidence: 63%

Segmental, Synaptic Actions of Commissural Interneurons in the Mouse Spinal Cord

Quinlan¹,

Kiehn²

2007

Journal of Neuroscience

121

148

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Left-right alternation depends on activity in commissural interneurons (CINs) that have axons crossing in the midline. In this study, we investigate the CIN connectivity to local motor neurons using a newly developed preparation of the in vitro neonatal mouse spinal cord that allows us to identify all classes of CINs. Nineteen of 29 short-range CINs with axonal projections Ͻ1.5 segments (sCINs) directly excited, directly inhibited, or indirectly inhibited contralateral motor neurons in the quiescent spinal cord. Excitation was glutamatergic and inhibition was mixed glycinergic and/or GABAergic. Long-range CINs were also found to have input to local, contralateral motor neurons. Thirteen of 29 descending CINs had similar synaptic connectivity to contralateral motor neurons as the sCINs, including direct excitation and direct and indirect inhibition. Some (9 of 23) rostrally projecting ascending CINs, and a few (2 of 10) CINs with bifurcating axons that both ascend and descend, indirectly inhibited local, contralateral motor neurons. Rhythmic firing during locomotor-like activity was observed in a number of CINs with segmental synaptic effects on contralateral motor neurons. This study outlines the basic connectivity pattern of CINs in the mouse spinal cord on a segmental level. Our study suggests that, based on observed synaptic connectivity, both short-and long-range CINs are likely involved in segmental left-right coordination and that the CIN system is organized into a dual-inhibitory and single-excitatory system. These systems are organized in a way that they could provide appropriate coordination during locomotion.

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Section: Excitatory Cinsmentioning

confidence: 63%

Segmental, Synaptic Actions of Commissural Interneurons in the Mouse Spinal Cord

Quinlan¹,

Kiehn²

2007

Journal of Neuroscience

121

148

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“…It has been shown that pyramidal tract neurons influence ipsilateral MNs in normal animals through several different types of corticoreticulo-spinal pathways ). Cortico-reticulospinal pathways are suggested to compensate for the transmission of motor commands after damage to corticospinal neurons in adult cats and monkeys Jankowska et al 2005Nishimura et al 2009;Pettersson et al 2007;Riddle et al 2009). In the present study, roughly 50% of recorded ipsilateral MNs responded to stimulation of the left pyramid after the transection of the C 2 dorsal column in hemidecorticated rats (Fig.…”

Section: Possible Descending Cortical Motor Pathwaysmentioning

confidence: 99%

“…The actual site of plastic change for synaptic transmission to ipsilateral MNs after the juvenile brain was lesioned remains to be solved. After the application of 4-aminopyridine (4-AP), pyramidal excitation could induce EPSPs in ipsilateral MNs due to the enhancement of synaptic transmission in the cortico-reticulo-spinal pathways (Jankowska et al 2005). It is important to examine whether the strengthened connection in hemidecorticated rats is the same as the connection enhanced by 4-AP.…”

Section: Further Questionsmentioning

confidence: 99%

Formation of Descending Pathways Mediating Cortical Command to Forelimb Motoneurons in Neonatally Hemidecorticated Rats

Umeda

Takahashi

Isa

et al. 2010

Journal of Neurophysiology

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Neonatally hemidecorticated rats show fairly normal reaching and grasping behaviors of the forelimb contralateral to the lesion at the adult stage. Previous experiments using an anterograde tracer showed that the corticospinal fibers originating from the sensorimotor cortex of the intact side projected aberrant collaterals to the spinal gray matter on the ipsilateral side. The present study used electrophysiological methods to investigate whether the aberrant projections of the corticospinal tract mediated the pyramidal excitation to the ipsilateral forelimb motoneurons and, if so, which pathways mediate the effect in the hemidecorticated rats. Electrical stimulation to the intact medullary pyramid elicited bilateral negative field potentials in the dorsal horn of the spinal cord. In intracellular recordings of forelimb motoneurons, oligosynaptic pyramidal excitation was detected on both sides of the spinal cord in the hemidecorticated rats, whereas pyramidal excitation of motoneurons on the side ipsilateral to the stimulation was much smaller in normal rats. By lesioning the dorsal funiculus at the upper cervical level, we clarified that the excitation was transmitted to the ipsilateral motoneurons by at least two pathways: one via the corticospinal tract and spinal interneurons and the other via the cortico-reticulo-spinal pathways. These results suggested that in the neonatally hemidecorticated rats, the forelimb movements on the side contralateral to the lesion were modulated by motor commands through the indirect ipsilateral descending pathways from the sensorimotor cortex of the intact side either via the spinal interneurons or reticulospinal neurons.

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“…While many plausible explanations for this finding are possible, the simplest explanation would be that direct and indirect reticulospinal pathways were strengthened from the left PMRF to motoneurons on the right side. We know there are reticulospinal neurons with direct contralateral projections to the spinal gray, and there are also strong ipsilateral reticulospinal projections to spinal interneurons that decussate, so these substrates exist (Edgley et al 2004;Jankowska et al 2005;Jankowska and Edgley 2006;Zaaimi et al 2012). The current study was not designed to distinguish between the various possible explanations, which remain as topics for further investigation.…”

Section: Potential Mechanisms For Recovery: Pmrf Contributionsmentioning

confidence: 95%

“…Following damage to corticospinal projections, recovery of arm function could be mediated by strengthening of PMRF effectiveness via corticoreticular pathways from intact ipsilesional cortical motor areas (Jankowska et al 2005;Jankowska and Edgley 2006;Rho et al 1997). Recovery of arm function could also be mediated by increased effectiveness of corticoreticular projections from contralesional homologous cortical motor regions.…”

Section: Potential Mechanisms For Recovery: Pmrf Contributionsmentioning

confidence: 99%

Evidence for a role of the reticulospinal system in recovery of skilled reaching after cortical stroke: initial results from a model of ischemic cortical injury

2015

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The purposes of this pilot study were to create a model of focal cortical ischemia in Macaca fascicularis and to explore contributions of the reticulospinal system in recovery of reaching. Endothelin-1 was used to create a focal lesion in the shoulder/elbow representation of left primary motor cortex (M1) of two adult female macaques. Repetitive microstimulation was used to map upper limb motor outputs from right and left cortical motor areas and from the pontomedullary reticular formation (PMRF). In subject 1 with a small lesion and spontaneous recovery, reaching was mildly impaired. Changes were evident in the shoulder/elbow representations of both the lesioned and contralesional M1, and there appeared to be fewer than expected upper limb responses from the left (ipsilesional) PMRF. In subject 2 with a substantial lesion, reaching was severely impaired immediately after the lesion. After 12 weeks of intensive rehabilitative training, reach performance recovered to near-baseline levels, but movement times remained about 50% slower. Surprisingly, the shoulder/elbow representation in the lesioned M1 remained completely absent after recovery, and there was a little change in the contralesional M1. There was a definite difference in motor output patterns for left versus right PMRF for this subject, with an increase in right arm responses from right PMRF and a paucity of left arm responses from left PMRF. The results are consistent with increased reliance on PMRF motor outputs for recovery of voluntary upper limb motor control after significant cortical ischemic injury.

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How to Enhance Ipsilateral Actions of Pyramidal Tract Neurons

Cited by 32 publications

References 15 publications

Segmental, Synaptic Actions of Commissural Interneurons in the Mouse Spinal Cord

Segmental, Synaptic Actions of Commissural Interneurons in the Mouse Spinal Cord

Formation of Descending Pathways Mediating Cortical Command to Forelimb Motoneurons in Neonatally Hemidecorticated Rats

Evidence for a role of the reticulospinal system in recovery of skilled reaching after cortical stroke: initial results from a model of ischemic cortical injury

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