Direct and Indirect Corticospinal Control of Arm and Hand Motoneurons in the Squirrel Monkey (Saimiri sciureus)

1997 ◽  
Vol 78 (2) ◽  
pp. 721-733 ◽  
Author(s):  
M. A. Maier ◽  
E. Olivier ◽  
S. N. Baker ◽  
P. A. Kirkwood ◽  
T. Morris ◽  
...  
Keyword(s):  
Squirrel Monkey ◽  
Macaque Monkey ◽  
Saimiri Sciureus ◽  
Excitatory Postsynaptic Potential ◽  
Onset Latency ◽  
Implanted Electrodes ◽  
Postsynaptic Potential ◽  
Common Response ◽  
Hand Muscle ◽  
Comparable Sample

Maier, M. A., E. Olivier, S. N. Baker, P. A. Kirkwood, T. Morris, and R. N. Lemon. Direct and indirect corticospinal control of arm and hand motoneurons in the squirrel monkey ( Saimiri sciureus). J. Neurophysiol. 78: 721–733, 1997. Anatomic evidence suggests that direct corticomotoneuronal (CM) projections to hand motoneurons in the New World squirrel monkey ( Saimiri sciureus) are weak or absent, but electrophysiological evidence is lacking. The nature of the corticospinal linkage to these motoneurons was therefore investigated first with the use of transcranial magnetic stimulation (TMS) of the motor cortex under ketamine sedation in five monkeys. TMS produced early responses in hand muscle electromyogram, but thresholds were high (compared with macaque monkey) and the onset latency was variable. Second, stimulation of the pyramidal tract (PT) was carried out with the use of chronically implanted electrodes in ketamine-sedated monkeys; this produced more robust responses that were markedly facilitated by repetitive stimulation, with little decrease in latency on the third compared with the first shock. Finally, postsynaptic potentials were recorded intracellularly from 93 arm and hand motoneurons in five monkeys under general chloralose anesthesia. After a single PT stimulus, the most common response was a small, slowly rising excitatory postsynaptic potential (EPSP), either alone (35 of 93 motoneurons) or followed by an inhibitory postsynaptic potential (39 of 93). The segmental delay of the early EPSPs was within the monosynaptic range (mean 0.85 ms); however, the rise time of these EPSPs was slow (mean 1.3 ms) and their amplitude was small (mean 0.74 mV). These values are significantly slower and smaller than EPSPs in a comparable sample of Old World macaque monkey motoneurons. The results show that CM connections do exist in the squirrel monkey but that they are weak and possibly located on the remote dendrites of the motoneurons. The findings are consistent with earlier anatomic studies. Repetitive PT stimulation produced large, late EPSPs in some motoneurons, suggesting that, in this species, there are relatively strong nonmonosynaptic pathways linking the corticospinal tract to hand motoneurons.

Stimulation of aortic nerve evokes three different response patterns in neurons of rostral VLM of the rat

1996 ◽  
Vol 271 (6) ◽  
pp. R1720-R1728 ◽  
Author(s):  
A. Zagon ◽  
K. M. Spyer
Keyword(s):  
Discharge Rate ◽  
Ventrolateral Medulla ◽  
Excitatory Postsynaptic Potential ◽  
Onset Latency ◽  
Postsynaptic Potential ◽  
Aortic Nerve ◽  
Group 2 ◽  
Regular Increase ◽  
Stimulation Of ◽  
Group 1

Because the aortic nerve of the rat is believed to contain only barosensory fibers in a functionally significant number, stimulation of this nerve provides a convenient means to identify barosensitive neurons in the central nervous system. The aim of the present study was to describe the characteristics of responses to stimulation of the aortic nerve in the neurons of the ventrolateral medulla oblongata (VLM) from in vivo intracellular recordings. Data were obtained from 25 neurons that were either spontaneously active and exhibited pulse-synchronous discharge or were silent. Cells that showed a regular increase in their discharge rate during diastole responded with either an inhibitory postsynaptic potential (IPSP, group 1; n = 3) or a biphasic excitatory postsynaptic potential (EPSP)-IPSP (group 2; n = 10) to aortic nerve stimulation. Parameters of the inhibitory response were similar in both groups (27 +/- 2 and 31 +/- 2 ms for onset latency and 55 +/- 10 and 67 +/- 7 ms in duration, respectively). In group 2 cells, the inhibition was, however, preceded by a brief excitation (14 +/- 2 ms for onset latency and 13 +/- 1 ms in duration). Group 3 neurons, which showed a regular increase in their discharge rate during or before systole (n = 7), responded with an EPSP (20 +/- 2 ms for onset latency and 44 +/- 5 ms in average duration). Group 1 and 3 responses were also encountered in quiescent neurons (n = 5). Intracellular labeling revealed that neurons of all three types were localized within the rostral VLM. The functional significance of these findings is discussed.

Striking Differences in Transmission of Corticospinal Excitation to Upper Limb Motoneurons in Two Primate Species

2000 ◽  
Vol 84 (2) ◽  
pp. 698-709 ◽  
Author(s):  
K. Nakajima ◽  
M. A. Maier ◽  
P. A. Kirkwood ◽  
R. N. Lemon
Keyword(s):  
Squirrel Monkey ◽  
Upper Limb ◽  
Hand Function ◽  
Significant Proportion ◽  
Macaque Monkey ◽  
Primate Species ◽  
Saimiri Sciureus ◽  
Reticular Nucleus ◽  
Experimental Conditions ◽  
Antidromic Activation

There is considerable debate as to the relative importance, for cortical control of upper limb movements, of direct cortico-motoneuronal (CM) versus indirect, propriospinal transmission of corticospinal excitation to cervical motoneurons. In the cat, which has no CM connections, a significant proportion of corticospinal excitation reaches forelimb motoneurons via a system of C3–C4propriospinal neurons (PN). In contrast, in the macaque monkey most motoneurons receive direct CM connections, and, under the same experimental conditions as in the cat, there is little evidence for PN transmission. We have investigated corticospinal transmission in the New World squirrel monkey ( Saimiri sciureus) because its CM projections are weaker than in the macaque. Intracellular recordings were made from motoneurons identified from the ulnar, median, and deep radial (DR) nerves in four adult squirrel monkeys under chloralose anesthesia and neuromuscular paralysis. Responses to stimulation of the contralateral medullary pyramid were recorded before and after a lesion to the dorsolateral funiculus (DLF) at C5, designed to interrupt direct corticospinal inputs to the lower cervical segments and unmask PN-mediated effects. This lesion greatly reduced the proportion of motoneurons showing either CM EPSPs or disynaptic IPSPs, but the proportion showing late EPSPs with segmental latencies beyond the monosynaptic range, evoked by repetitive but not single PT stimuli, was unaffected: 23 of 29 motoneurons (79%) before and 32 of 37 (86%) after the lesion; 41% of these late EPSPs had strictly disynaptic latencies after the lesion, only 14% before. These results are in striking contrast to the macaque (late EPSPs in only 18% of motoneurons before a C5 lesion, 19% after it). Transmission of the late EPSPs via C3–C4 PNs in the squirrel monkey was indicated by their absence after an additional C2 DLF lesion. Nearly all tested motoneurons also responded with short latency EPSPs to stimulation in the ipsilateral lateral reticular nucleus. By analogy with the cat, these EPSPs probably reflect antidromic activation of ascending collaterals of C3–C4 PNs with monosynaptic connections to motoneurons; the EPSPs were significantly smaller than in the cat but larger than in the macaque. These results suggest that the positive correlation across species between more advanced hand function and the strength of the CM system is accompanied by a negative correlation between hand function and the strength of the PN system. We hypothesize that in primates with more advanced hand function, the CM system effectively replaces PN-mediated control. This would include a contribution to the control of reaching movements, which are said to be specifically under the control of the PN system in the cat, and we speculate that these differences may be related to the degree of dexterity exhibited by the different species. This interpretation of the results predicts that in man, where the CM system is highly developed, the PN system is unlikely to be responsible for significant transmission of cortical commands to upper limb motoneurons.

Vocalization in the squirrel monkey (Saimiri sciureus) elicited by brain stimulation

1967 ◽  
Vol 4 (2) ◽  
Author(s):  
U. J�rgens ◽  
M. Maurus ◽  
D. Ploog ◽  
P. Winter
Keyword(s):  
Squirrel Monkey ◽  
Brain Stimulation ◽  
Saimiri Sciureus

Morphology and mitochondrial phylogenetics reveal that the Amazon River separates two eastern squirrel monkey species: Saimiri sciureus and S. collinsi

2015 ◽  
Vol 82 ◽  
pp. 426-435 ◽  
Author(s):  
Michelle P. Mercês ◽  
Jessica W. Lynch Alfaro ◽  
Wallax A.S. Ferreira ◽  
Maria L. Harada ◽  
José S. Silva Júnior
Keyword(s):  
Squirrel Monkey ◽  
Saimiri Sciureus ◽  
Amazon River ◽  
Monkey Species

Plasmodium falciparumin the squirrel monkey (Saimiri sciureus): infection of non-splenectomised animals as a model for exploring clinical manifestations of malaria

2000 ◽  
Vol 2 (8) ◽  
pp. 945-954 ◽  
Author(s):  
Hugues Contamin ◽  
Charlotte Behr ◽  
Odile Mercereau-Puijalon ◽  
Jean-Claude Michel
Keyword(s):  
Squirrel Monkey ◽  
Clinical Manifestations ◽  
Saimiri Sciureus

Production of Zinc Deficiency in the Squirrel Monkey (Saimiri sciureus)

1967 ◽  
Vol 93 (4) ◽  
pp. 499-510 ◽  
Author(s):  
M. P. Macapinlac ◽  
G. H. Barney ◽  
W. N. Pearson ◽  
W. J. Darby
Keyword(s):  
Squirrel Monkey ◽  
Zinc Deficiency ◽  
Saimiri Sciureus

Electrically coupled pacemaker neurons respond differently to same physiological inputs and neurotransmitters

1984 ◽  
Vol 51 (6) ◽  
pp. 1362-1374 ◽  
Author(s):  
E. Marder ◽  
J. S. Eisen
Keyword(s):  
Motor Neurons ◽  
Slow Wave ◽  
Lucifer Yellow ◽  
Electrical Coupling ◽  
Excitatory Postsynaptic Potential ◽  
Panulirus Interruptus ◽  
Bursting Neuron ◽  
Postsynaptic Potential ◽  
Pyloric Dilator ◽  
Muscarinic Cholinergic

The two pyloric dilator (PD) motor neurons and the single anterior burster (AB) interneuron are electrically coupled and together comprise the pacemaker for the pyloric central pattern generator of the stomatogastric ganglion of the lobster, Panulirus interruptus. Previous work (31) has shown that the AB neuron is an endogenously bursting neuron, while the PD neuron is a conditional burster. In this paper the effects of physiological inputs and neurotransmitters on isolated PD neurons and AB neurons were studied using the lucifer yellow photoinactivation technique (33). Stimulation of the inferior ventricular nerve (IVN) fibers at high frequencies elicits a triphasic response in AB and PD neurons: a rapid excitatory postsynaptic potential (EPSP) followed by a slow inhibitory postsynaptic potential (IPSP), followed by an enhancement of the pacemaker slow-wave depolarizations. Photoinactivation experiments indicate that the enhancement of the slow wave is due primarily to actions of the IVN fibers on the PD neurons but not on the AB neuron. Bath-applied dopamine dramatically alters the motor output of the pyloric system. Photoinactivation experiments show that 10(-4) M dopamine increases the amplitude and frequency of the slow-wave depolarizations recorded in the AB neurons but hyperpolarizes and inhibits the PD neurons. Bath-applied serotonin increases the frequency and amplitude of the slow-wave depolarizations in the AB neuron but has no effect on PD neurons. Pilocarpine, a muscarinic cholinergic agonist, stimulates slow-wave depolarization production in both PD neurons and the AB neuron, but the waveform and frequency of the slow waves elicited are quite different. These results show that although the electrically coupled PD and AB neurons always depolarize synchronously and act together as the pacemaker for the pyloric system, they respond differently to a neuronal input and to several putative neuromodulators. Thus, despite electrical coupling sufficient to ensure synchronous activity, the PD and AB neurons can be modulated independently.

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