Synaptic linkages between red nucleus cells and limb muscles during a multi-joint motor task

The magnocellular red nucleus (RNm) becomes highly active when a monkey reaches to grasp an object. However, the only spike-triggered averaging studies of the RNm to date have been restricted to a simple wrist tracking paradigm and electromyographic (EMG) measurements of muscles of the forearm. We have now measured EMG signals from a large number of muscles throughout the shoulder, arm, forearm, and hand during a variety of tasks, including unconstrained reaching and grasping movements. Relations between these EMG signals and single-unit activity were assessed by on-line spike-triggered averaging and revealed significant post-spike effects among muscles of the shoulder and proximal arm, as well as intrinsic hand muscles. Although there remained a strong bias toward the extensor muscles of the forearm, as has been shown earlier, these results reinforce the importance of the RNm in the control of coordinated, whole-limb reaching movements.     

Activity of spinal interneurons and their effects on forearm muscles during voluntary wrist movements in the monkey

We studied the activity of 577 neurons in the C6-T1 spinal cord of three awake macaque monkeys while they generated visually guided, isometric flexion/extension torques about the wrist. Spike-triggered averaging of electromyographic activity (EMG) identified the units' correlational linkages with 相似文献   

Immobilizing muscle weakness accentuated in leg and proximal muscles

A 54 year old waiter was referred to the hospital because of proximal muscle weakness, most pronounced in his legs, which progressed to an inability to stand or walk within weeks. Myopathy was diagnosed based on the muscle biopsy findings and myositis was ruled out by laboratory and biopsy results. Further investigations led us to exclude an endocrine cause, hypovitaminosis D, infectious myopathy or a paraneoplastic syndrome. Heteroanamnesis revealed severe alcoholism, lasting for more than 30 years. The presumed alcohol induced hepatopathy was confirmed by liver biopsy. There were no signs of an acute alcoholic myopathy, as the weakness had developed rather insidiously, there was no elevation of the CK serum level nor myoglobinuria and a type 2 fibre atrophy was found by muscle biopsy. As expected the weakness improved under abstention. Thus the final diagnosis of a chronic alcohol induced myopathy was established.     

Absorption of L-DOPA from the proximal small intestine studied in the rhesus monkey by positron emission tomography

Positron emission tomography (PET) seems to be a valuable method for the understanding of intestinal absorption mechanisms, for simultaneous quantitation of absorption rate and distribution kinetics to the tissues of interest after oral drug delivery. PET was evaluated in three Rhesus monkeys for quantitation of the absorption rate from the gastrointestinal tract and the distribution kinetics into different organs. To obtain optimal standardized conditions for the measurement of absorption the drug was administered via a naso-duodenal catheter directly to the absorption site in the proximal small intestine. l-DOPA was used as study drug given in a suspension together with carbidopa and the radiomarker l-[beta-11C]DOPA. The l-DOPA suspension was given into the duodenum without and after administration of a suspension of six l-amino acids (120 mM) in order to investigate any interaction on the intestinal absorption and distribution of l-DOPA into the liver and brain tissue. Intestinal absorption was in general minor during the first study period and higher together with administered l-amino acids. The somewhat contradictory result with increased absorption when amino acids were present in the intestinal lumen, may be a consequence of increased intestinal motility initiated by the nutrient load.     

Speaking rate from proximal and distal contexts is used during word segmentation.

A series of eye-tracking and categorization experiments investigated the use of speaking-rate information in the segmentation of Dutch ambiguous-word sequences. Juncture phonemes with ambiguous durations (e.g., [s] in 'eens (s)peer,' “once (s)pear,” [t] in 'nooit (t)rap,' “never staircase/quick”) were perceived as longer and hence more often as word-initial when following a fast than a slow context sentence. Listeners used speaking-rate information as soon as it became available. Rate information from a context proximal to the juncture phoneme and from a more distal context was used during on-line word recognition, as reflected in listeners' eye movements. Stronger effects of distal context, however, were observed in the categorization task, which measures the off-line results of the word-recognition process. In categorization, the amount of rate context had the greatest influence on the use of rate information, but in eye tracking, the rate information's proximal location was the most important. These findings constrain accounts of how speaking rate modulates the interpretation of durational cues during word recognition by suggesting that rate estimates are used to evaluate upcoming phonetic information continuously during prelexical speech processing. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Regional differences in the nitrergic innervation between the proximal and the distal colon in rats

BACKGROUND & AIMS: Functional differences in the inhibitory neural pathway between the proximal and the distal colon are unknown. METHODS: We investigated the nonadrenergic, noncholinergic (NANC) relaxation, nitric oxide synthase (NOS) synthesis, and NOS messenger RNA (mRNA) expression of the myenteric plexus in the proximal and the distal colon in rats. RESULTS: Transmural nerve stimulation of the neuromuscular preparations from the proximal colon showed greater NANC relaxations than those from the distal colon. NANC relaxations were abolished by the NO biosynthesis inhibitor (NG-nitro-L-arginine methyl ester) in the proximal and the distal colon, suggesting mediation by NO released from the myenteric plexus. The average number of NOS-immunoreactive cells was significantly higher in the tissue from the proximal colon than in the tissue from the distal colon. Western and Northern blot analyses showed a higher density of the immunoreactive NOS band and the NOS mRNA band in the tissue from the proximal colon than in that from the distal colon. CONCLUSIONS: These observations indicate that the number of NOS-containing neurons and the NOS activity are increased in the myenteric plexus of the proximal colon compared with the distal colon, resulting in greater NANC relaxation in the proximal colon. These findings may explain the physiological role of the proximal colon as an organ for fecal storage and absorption of excess fluid.     

Comparison of the morphologic and vascular reactivity of the proximal and distal radial artery

BACKGROUND: Variations in the morphology and vascular reactivity of the proximal and distal radial artery might influence its performance as a bypass conduit. METHODS: The morphologic and functional characteristics of the proximal and distal RAs were compared with those of the left and right internal mammary arteries by using histologic and in vitro organ bath techniques. RESULTS: Proximal RA had a significantly greater medial cross-sectional area compared with that of the distal RA (2.48+/-0.27 mm2 compared with 1.86+/-0.21 mm2, p< 0.05), which were both significantly greater than the left internal mammary artery (0.54+/-0.09 mm2) or the right internal mammary artery (0.67+/-0.03 mm2). Proximal RA had a significantly greater response to 90 mmol/L potassium chloride than that of distal RA (88.4+/-7.3 compared with 60.2+/-10.3 mN, p<0.05), and both contracted more than the left internal mammary artery (30.3+/-2.9 mN) and the right internal mammary artery (32.6+/-4.1 mN). There was no difference in the response to noradrenaline and adrenaline between proximal and distal RA, both of which contracted more than the left and right internal mammary arteries. CONCLUSIONS: When choosing a segment of RA for use as a bypass conduit, regional variations in biologic properties should be considered.     

Presaccadic omnidirectional burst activity in the basal interstitial nucleus in the monkey cerebellum

The endocrine function and pituitary imaging in Sheehan's syndrome more than 30 years after causative events were evaluated. Magnetic resonance imaging (MRI), a combined anterior pituitary test, plasma vasopressin-to-osmolality adaptation study, and antithyroid and antipituitary cell antibody measurement were performed in 6 women with Sheehan's syndrome. The interval from delivery to the onset of symptoms of hormonal deficiency ranged from 3 to 32 years. Since clinical onset, all had received glucocorticoid and thyroid replacement therapy. Cranial MRI examination showed an "empty sella" in 5 cases. Among these, 2 of 5 (40%) demonstrated panhypopituitarism and the other 3 (60%) maintained gonadotropin response. The pituitary gland was normally discernible but with a low-intensity lesion on T1-weighted images in a patient who maintained PRL and gonadotropin responses. Posterior pituitary function was abnormal in 3 of 6 (50%) despite the absence of polyuria. No antipituitary antibodies were detected in any of the cases. Thyroid peroxidase antibody was negative in all cases, but antithyroglobulin antibody was detected in 2 of 6 (33%). Thyroid-stimulating antibody was not detected, but one case had an anti-TSH antibody. Thirty years after the initial events, most patients with Sheehan's syndrome showed signs of an empty sella on MRI, all having noticeable suppression of anterior and/or posterior pituitary hormones with no related autoimmunity.     

Responses of neurons of the nucleus of the optic tract and the dorsal terminal nucleus of the accessory optic tract in the awake monkey

The in vitro effect of recombinant human Granulocyte Macrophage Colony Stimulating Factor (rh-GMCSF) on the leishmanicidal activity and superoxide anion productivity of macrophages derived from human blood monocytes (MOs) were investigated. MOs treated with 25, 125, or 250 U/mL of rh-GMCSF for 72 h prior to infection with leishmania parasites, manifested significant dose-dependent increase in its leishmanicidal activities against Leishmania major and Leishmania donovani parasites. The percentage of increase in leishmanicidal activity of L. major-infected MOs were 22.71, 64.34 and 81.34, respectively while in L. donovani-infected MOs, it reached 3.01, 32.28 and 74.38, respectively. Treatment of leishmania-infected MOs with rh-GMCSF (250 U/mL) for different periods of time up to 96 hours, induced a significant time-dependent reduction in the percentage of infected cells and the parasitic load (No. of amastigotes/100 MOs). After 96 h of treatment with rh-GMCSF, the percentages of reduction in the infection rates were 82.45 in L.major-infected MOs (p < 0.001) and 39.65 in L. donovani-infected cells (p < 0.01). The percentage of reduction in the parasitic load reached 90.82 (p < 0.001) and 36.6 (p < 0.05) in MOs infected with L. major and L. donovani, respectively. The priming effect of rh-GMCSF on superoxide anion production by human MOs stimulated with phorbol myristate acetate (PMA) was both dose-dependent and time-dependent. In 72 hour-old human MOs, the maximum superoxide anion release was generated by MOs primed for 45 min with 500 U/mL of rh-GMCSF. These cells produced 8.960 +/- 2.075 nmol/5 x 10(4) MOs/ 180 min as compared to 4.563 +/- 1.773 nmol/5 x 10(4) unprimed cell control/180 min (p < 0.001).     

Distribution of motoneurons supplying feline neck muscles taking origin from the shoulder girdle

A combination of fluorescent retrograde tracers and horseradish peroxidase (HRP) was used to compare the spinal distributions of motoneurons supplying shoulder muscles with attachments to the skull and cervical spinal cord that suggest a significant role in head movement. Two muscles, the rhomboideus and the levator scapulae, were innervated by multiple segmental nerve bundles that entered the muscles at different rostrocaudal locations. Motoneurons that were labelled retrogradely from rhomboideus nerve bundles formed a single, long column in the ventral horn from C4 to C6, lateral to previously studied motor nuclei supplying deep neck muscles. When different tracers were used to differentiate motoneurons supplying specific nerve bundles, discrete subnuclei could be identified that were organized in a rostrocaudal sequence corresponding to the rostrocaudal order of the nerve bundles. Levator scapulae motoneurons formed a second elongate column immediately lateral to the rhomboidues motor nucleus. Three other muscles, that trapezius, sternomastoideus, and cleidomastoideus, were supplied by cranial nerve XI. Labelled motoneurons from these muscles formed a single column from the spinomedullary junction to middle C6. Within this column, the three motor nuclei supplying the sternomastoideus, cleidomastoideus, and trapezius were laminated mediolaterally. Sternomastoideus and cleidomastoideus motoneurons were confined to upper cervical segments, whereas trapezius motoneurons were found from C1 to C6. In C1 and C6, the motoneuron column was located centrally in the gray matter, but, between C2 and C5, the column lay on the lateral wall of the ventral horn in a position dorsolateral to motor nuclei supplying the rhomboideus and the deeper neck muscles. The findings in this study suggest that descending and propriospinal systems responsible for coordinating head movement may have to descend as far caudally as C6 if they are to project onto muscles controlling the mobility of the lower neck.     

The isolation and characteristics of the green monkey lentivirus

We characterized the simian immunodeficiency virus isolated from Cercopithecus aethiops (subspecies C. a. pygerythrus) originating from Kenya. SIV was isolated and continuously produced with the MOLT4 clone 8 cell line and was designated as SIV-SU1. SIV-SU1 isolate replicated with high efficiency in MOLT4 clone 8, MT-2 with moderate efficiency in CEM x 174 and with poor efficiency in HUT-78, U937, C8166. The infection of MT-2, C8166 and HUT-78 resulted in extensive cell killing. Western blotting of purified preparations of SIV-SU1 revealed viral proteins of 130, 68, 55, 41, 24, 17 kDa. Cross-reactivity of SIV-SU1 proteins with HIV-1, HIV-2, SIVmac, SIVsm, SIVmnd was studied by radioimmunoprecipitation assay. The most extensive cross-reactivity was observed with SIVmac. Total cellular DNA from chronically infected cells was hybridized to SIVagm266 DNA probes. Detection of cross-hybridizing DNA sequences required very low stringency, and the restriction endonuclease fragmentation pattern of SIV-SU1 differed from other SIVs.     

The mechanism of bicarbonate reabsorption in the proximal and distal tubules of the kidney. 1965

The mechanism of HCO3- reabsorption in proximal and distal tubules was examined in rats undergoing NaHCO3 diuresis. The steady-state intratubular pH was measured with pH-sensitive glass microelectrodes and compared with the equilibrium pH calculated from the HCO3- concentration of the tubular fluid (measured with quinhydrone electrodes) and plasma Pco2. In the proximal tubule the intratubular pH and the equilibrium pH were identical, indicating no accumulation of excess H2CO3. After inhibition of carbonic anhydrase, however, intratubular pH was significantly lower (0.85 pH U) than the equilibrium pH. It was concluded that HCO3- reabsorption in the proximal tubule was mediated by H+ secretion, but that carbonic anhydrase located in the luminal membrane of the cell prevented H2CO3 from accumulating in the tubular fluid. In the distal tubule the intratubular pH was 0.85 U lower than the equilibrium pH. This difference could be obliterated by an intravenous injection of carbonic anhydrase. It was concluded that HCO3- reabsorption in this segment was also accomplished by H+ secretion. The accumulation of excess H2CO3 in the tubular fluid indicated that, in contrast to the proximal tubule, carbonic anhydrase was not located in the luminal membrane of distal tubular cells.     

Distribution of nitric oxide synthase in the esophagus of the cat and monkey

The distribution of nitrergic neurons and processes in the esophagus of the cat and monkey was studied by light microscopic immunocytochemistry using a specific antibody against purified rat brain nitric oxide synthase and immunoperoxidase procedures. Immunoreactive nerve fibers were found pervading the myenteric plexus, submucous plexus and plexus of the muscularis mucosae, and particularly in the lower esophagus a few immunoreactive fibers entered the epithelium as free nerve endings, some of which derived from perivascular fibers. In the upper esophagus immunoreactive motor end-plates were found in the striated muscle. Thirty-forty-five percent of neuronal cell bodies found in the intramural ganglia and along the course of nerve fiber bundles were immunoreactive and were of the three morphological types earlier described. In the intramural ganglia immunoreactive nerve fibers formed a plexus in which varicose nerve terminals were in close relation to immunoreactive and non-immunoreactive neurons. The intramural blood vessels that crossed the different layers of the esophageal wall were surrounded by paravascular and perivascular plexuses containing immunoreactive nerve fibers. The anatomical findings suggest that nitric oxide is involved in neural communication and in the control of peristalsis and vascular tone in the esophagus. In the lower esophagus a few nitrergic nerve fibers are anatomically disposed to subserve a sensory-motor function.     

Difference between proximal and distal right coronary flow velocity pattern in humans

The choice of moral acts is governed by the unique ethnic and/or cultural meaning and values ascribed to by the individual. In pursuing an "acceptable" moral choice, the process of analysis is further directed by the ethical theories which are molded by time and tempered by the current context to which the action is undertaken. An OPTIMIN MODEL OF ETHICAL-DECISION MAKING PARADIGM is proposed, and health care policy on cultural diversity is adduced.     

Functional organization of owl monkey lateral geniculate nucleus and visual cortex

The nocturnal, New World owl monkey (Aotus trivirgatus) has a rod-dominated retina containing only a single cone type, supporting only the most rudimentary color vision. However, it does have well-developed magnocellular (M) and parvocellular (P) retinostriate pathways and striate cortical architecture [as defined by the pattern of staining for the activity-dependent marker cytochrome oxidase (CO)] similar to that seen in diurnal primates. We recorded from single neurons in anesthetized, paralyzed owl monkeys using drifting, luminance-modulated sinusoidal gratings, comparing receptive field properties of M and P neurons in the lateral geniculate nucleus and in V1 neurons assigned to CO "blob," "edge," and "interblob" regions and across layers. Tested with achromatic stimuli, the receptive field properties of M and P neurons resembled those reported for other primates. The contrast sensitivity of P cells in the owl monkey was similar to that of P cells in the macaque, but the contrast sensitivities of M cells in the owl monkey were markedly lower than those in the macaque. We found no differences in eye dominance, orientation, or spatial frequency tuning, temporal frequency tuning, or contrast response for V1 neurons assigned to different CO compartments; we did find fewer direction-selective cells in blobs than in other compartments. We noticed laminar differences in some receptive field properties. Cells in the supragranular layers preferred higher spatial and lower temporal frequencies and had lower contrast sensitivity than did cells in the granular and infragranular layers. Our data suggest that the receptive field properties across functional compartments in V1 are quite homogeneous, inconsistent with the notion that CO blobs anatomically segregate signals from different functional "streams."     

The role of distal and proximal interaction in infant social preference formation.

Created experimental social histories for 22 24-wk-old infants to determine the role of distal and proximal interaction in social preference formation. Each S interacted with 3 different adults during a 3-wk period. The distal interactor smiled and talked to the infant. The proximal interactor rocked and patted the infant. The neutral interactor sat by the infant without responding in any way. During 9 preference tests, infants were allowed to move in a specially adapted walker toward any of the 3 interactors. During the 3 wks, infants increased the time spent near the distal interactor. In the 3rd wk, infants looked more at the distal interactor than at the proximal interactor, and spent more time near both distal and neutral interactors than near the proximal interactor. The separate roles of distal and proximal interaction in the formation of social preferences are discussed in terms of the different contributions infants can make to distal and proximal aspects of interaction. (22 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Distribution of several gut neuropeptides and their effects on motor activity in muscularis mucosae of guinea-pig proximal colon

The distribution of peptide-containing nerve fibers and the effect of their neuropeptides on motor activity were studied in the muscularis mucosae of the guinea-pig proximal colon. In the immunohistochemical study, it was shown that the tachykinin (TK)-containing nerve fibers densely innervated the muscularis mucosae. In the superfusion study, three kinds of TKs, i.e., neurokinin A (NK-A), neurokinin B (NK-B) or substance P (SP), enhanced the spontaneous activity on the strips of muscularis mucosae with a tetrodotoxin (TTX)-insensitive manner. Their potency was in the rank order of NK-A > SP. This suggests that the muscle has a predominant NK2 receptor. Calcitonin gene-related peptide (CGRP)-immunoreactive fibers were commonly observed in the muscle. CGRP induced a potent inhibition on spontaneous activity and a concentration-dependent inhibition on the NK-A-elicited excitation in the presence of TTX, indicating its direct effect on the receptor in the muscle. On the other had, gastrin releasing peptide (GRP), galanin, neuropeptide Y or somatostatin were more or less immunopositive in nerve fibers, but they had no effect on the motility of the muscle except that GRP sometimes showed a faint increase in spontaneous activity. Neither methionine-enkephalin nor gastrin-17/cholecystokinin was immunoreactive and had any effect on the muscle. These neuropeptides other than TKs and CGRP do not seem to be neuromediators of motor activity of muscularis mucosae. The results suggest the possibility that TK-, especially NK-A- and CGRP-containing neurons, participate in the regulation of motor activity of the muscularis mucosae in the guinea-pig proximal colon.     

Rostral fastigial nucleus activity in the alert monkey during three-dimensional passive head movements

The fastigial nucleus (FN) receives vestibular information predominantly from Purkinje cells of the vermis. FN in the monkey can be divided in a rostral part, related to spinal mechanisms, and a caudal part with oculomotor functions. To understand the role of FN during movements in space, single-unit activity in alert monkeys was recorded during passive three-dimensional head movements from rostral FN. Seated monkeys were rotated sinusoidally around a horizontal earth-fixed axis (vertical stimulation) at different orientations 15 degrees apart (including roll, pitch, vertical canal plane and intermediate planes). In addition, sinusoidal rotations around an earth-vertical axis (yaw stimulus) included different roll and pitch positions (+/-10 degrees, +/-20 degrees). The latter positions were also used for static stimulation. One hundred fifty-eight neurons in two monkeys were modulated during the sinusoidal vertical search stimulation. The vast majority showed a uniform response pattern: a maximum at a specific head orientation (response vector orientation) and a null response 90 degrees apart. Detailed analysis was obtained from 111 neurons. On the basis of their phase relation during dynamic stimulation and their response to static tilt, these neurons were classified as vertical semicircular canal related (n = 79, 71.2%) or otolith related (n = 25; 22.5%). Only seven neurons did not follow the usual response pattern and were classified as complex neurons. For the vertical canal-related neurons (n = 79) all eight major response vector orientations (ipsilateral or contralateral anterior canal, posterior canal, roll, and nose-down and nose-up pitch) were found in Fn on one side. Neurons with ipsilateral orientations were more numerous and on average more sensitive than those with contralateral orientations. Twenty-eight percent of the vertical canal-related neurons also responded to horizontal canal stimulation. None of the vertical canal-related neurons responded to static tilt. Otolith-related neurons (n = 25) had a phase relation close to head position and were considerably less numerous than canal-related neurons. Except for pitch, all other response vector orientations were found. Seventy percent of these neurons responding during dynamic stimulation also responded during static tilt. The sensitivity during dynamic stimulation was always higher than during static stimulation. Sixty-one percent of the otolith-related neurons responded also to horizontal canal stimulation. These results show that in FN, robust vestibular signals are abundant. Canal-related responses are much more common than otolith-related responses. Although for many canal neurons the responses can be related to single canal planes, convergence between vertical canals but also with horizontal canals is common.     

Ultrasonographic cross-sectional characteristics of muscles of the head and neck

OBJECTIVE: Computed tomography and magnetic resonance imaging are the common techniques for evaluating cross-sectional areas and volumes of human jaw muscles. Because computed tomography has the disadvantage of showing cumulative biological effects and because MRI poses a problem in terms of clinical availability and cost, the purpose of this study was to determine whether ultrasonography could be used to measure local linear cross-sectional dimensions of muscles of the head and neck. STUDY DESIGN: In 46 patients with signs and symptoms of temporomandibular disorders, the anterior temporalis, anterior masseter, deep masseter, anterior digastric, posterior digastric, and sternocleidomastoid muscles were measured bilaterally by ultrasonography to assess linear local cross-sectional dimensions. Measurements were made in 2 sessions with a time interval of at least 5 minutes. Data were analyzed for reliability and variability through use of the intraclass correlation coefficient (ICC) and the repeatability coefficient (RC). To assess local muscle asymmetry patterns, the absolute asymmetry index was used, with the mean maximum muscle diameters of the respective right and left sides calculated from 3 consecutive measurements. RESULTS: Satisfactory visualization of muscles was obtained in 93.8% of 1104 imaging procedures. For the ultrasound measurements there was a significant difference in local cross-sectional dimensions between the first and second sessions for the anterior temporalis muscle only (P < .01). Acceptable intrarater reliabilities were obtained for the deep masseter (ICC = 0.92), anterior digastric (ICC = 0.91), and sternocleidomastoid (ICC = 0.86) muscles, whereas evaluation of the posterior digastric (ICC = 0.74), anterior masseter (ICC = 0.72), and anterior temporalis (ICC = 0.70) muscles was associated with moderate reliability. Variability of repeated measurements was found to be acceptable for the anterior temporalis (RC = 0.32 mm) and posterior digastric (RC = 0.48 mm) muscles. Analysis of muscle site-related local cross-sectional dimensions showed a significant difference between the right and left sides for the deep masseter muscle only (P < .05). The study population investigated revealed mean asymmetry indices ranging from 5.3% for the anterior digastric muscle to 8.7% for the deep masseter muscle. CONCLUSIONS: Ultrasonography may prove to be a reliable diagnostic technique for the evaluation of cross-sectional dimensions and areas of muscles of the head and neck.     

Effects of cortical stimulation on red nucleus neurons in the guinea pig

The aim of the present work was to study the control that the cerebral cortex exerts on red nucleus (RN) neurons in the guinea pig. The experiments were carried out in anaesthetized animals. Electrical stimulation of localized cortical foci was performed by tungsten microelectrodes in frontal and parietal regions containing sensorimotor representations of the body. Single unit RN activity was extracellularly recorded through glass micropipettes, and the encountered RN neurons were recognized by searching their peripheral receptive field. Then, corticorubral influences were tested on RN neurons whose receptive field was located in the same body regions where motor responses were evoked by cortical stimulation. The stimulation with a single pulse evoked complex responses, typically consisting of long lasting inhibitions sometimes preceded by a weak facilitation and always followed by an excitatory rebound. The application of a second pulse modified this pattern, depending on the time interval between the two stimuli. In fact, the reduction of the interval below 300 ms enhanced the excitatory components whereas it shortened the inhibitory component; moreover, an "early" facilitation was evoked but only at intervals as short as 50-150 ms, or less. These results suggest that the corticorubral control may vary according to different levels of cortical activation, becoming more and more facilitatory as the cortical discharges increase from low frequency values (tonic activity) towards high frequency values (phasic activity).