scholarly journals Pyramidal tract neurons receptive to different forelimb joints act differently during locomotion

2012 ◽  
Vol 107 (7) ◽  
pp. 1890-1903 ◽  
Author(s):  
Erik E. Stout ◽  
Irina N. Beloozerova
Keyword(s):  
Motor Cortex ◽  
Cortical Neurons ◽  
Pyramidal Tract ◽  
Receptive Fields ◽  
Close Relation ◽  
Afferent Input ◽  
The Body ◽  
Pyramidal Tract Neurons ◽  
Discharge Duration ◽  
Increased Activity

During locomotion, motor cortical neurons projecting to the pyramidal tract (PTNs) discharge in close relation to strides. How their discharges vary based on the part of the body they influence is not well understood. We addressed this question with regard to joints of the forelimb in the cat. During simple and ladder locomotion, we compared the activity of four groups of PTNs with somatosensory receptive fields involving different forelimb joints: 1) 45 PTNs receptive to movements of shoulder, 2) 30 PTNs receptive to movements of elbow, 3) 40 PTNs receptive to movements of wrist, and 4) 30 nonresponsive PTNs. In the motor cortex, a relationship exists between the location of the source of afferent input and the target for motor output. On the basis of this relationship, we inferred the forelimb joint that a PTN influences from its somatosensory receptive field. We found that different PTNs tended to discharge differently during locomotion. During simple locomotion shoulder-related PTNs were most active during late stance/early swing, and upon transition from simple to ladder locomotion they often increased activity and stride-related modulation while reducing discharge duration. Elbow-related PTNs were most active during late swing/early stance and typically did not change activity, modulation, or discharge duration on the ladder. Wrist-related PTNs were most active during swing and upon transition to the ladder often decreased activity and increased modulation while reducing discharge duration. These data suggest that during locomotion the motor cortex uses distinct mechanisms to control the shoulder, elbow, and wrist.

Discharge Characteristics of Neurons in the Red Nucleus During Voluntary Gait Modifications: A Comparison with the Motor Cortex

2002 ◽  
Vol 88 (4) ◽  
pp. 1791-1814 ◽  
Author(s):  
Sylvain Lavoie ◽  
Trevor Drew
Keyword(s):  
Motor Cortex ◽  
Cortical Neurons ◽  
Red Nucleus ◽  
Receptive Fields ◽  
Maximal Activity ◽  
Swing Phase ◽  
Emg Activity ◽  
Step Cycle ◽  
Step Over ◽  
Increased Activity

We have examined the contribution of the red nucleus to the control of locomotion in the cat. Neuronal activity was recorded from 157 rubral neurons, including identified rubrospinal neurons, in three cats trained to walk on a treadmill and to step over obstacles attached to the moving belt. Of 72 neurons with a receptive field confined to the contralateral forelimb, 66 were phasically active during unobstructed locomotion. The maximal activity of the majority of neurons (59/66) was centered around the swing phase of locomotion. Slightly more than half of the neurons (36/66) were phasically activity during both swing and stance. In addition, some rubral neurons (14/66) showed multiple periods of phasic activity within the swing phase of the locomotor cycle. Periods of phasic discharge temporally coincident with the swing phase of the ipsilateral limb were observed in 7/66 neurons. During voluntary gait modifications, most forelimb-related neurons (70/72) showed a significant increase in their discharge activity when the contralateral limb was the first to step over the obstacle (lead condition). Maximal activity in nearly all cells (63/70) was observed during the swing phase, and 23/63 rubral neurons exhibited multiple increases of activity during the modified swing phase. A number of cells (18/70) showed multiple periods of increased activity during swing and stance. Many of the neurons (35/63, 56%) showed an increase in activity at the end of the swing phase; this period of activity was temporally coincident with the period of activity in wrist dorsiflexors, such as the extensor digitorum communis. A smaller proportion of neurons with receptive fields restricted to the hindlimbs showed similar characteristics to those observed in the population of forelimb-related neurons. The overall characteristics of these rubral neurons are similar to those that we obtained previously from pyramidal tract neurons recorded from the motor cortex during an identical task. However, in contrast to the results obtained in the rubral neurons, most motor cortical neurons showed only one period of increased activity during the step cycle. We suggest that both structures contribute to the modifications of the pattern of EMG activity that are required to produce the change in limb trajectory needed to step over an obstacle. However, the results suggest an additional role for the red nucleus in regulating intra- and interlimb coordination.

Activity of Pyramidal Tract Neurons in the Cat During Postural Corrections

2005 ◽  
Vol 93 (4) ◽  
pp. 1831-1844 ◽  
Author(s):  
I. N. Beloozerova ◽  
M. G. Sirota ◽  
G. N. Orlovsky ◽  
T. G. Deliagina
Keyword(s):  
Motor Cortex ◽  
Pyramidal Tract ◽  
Frontal Plane ◽  
Dorsal Side ◽  
The Body ◽  
Contact Forces ◽  
Postural Control System ◽  
Pyramidal Tract Neurons ◽  
The Right

The dorsal side-up body orientation in quadrupeds is maintained by a postural control system. We investigated participation of the motor cortex in this system by recording activity of pyramidal tract neurons (PTNs) from limb representations of the motor cortex during postural corrections. The cat was standing on the platform periodically tilting in the frontal plane, and maintained equilibrium at different body configurations: with the head directed forward (symmetrically alternating loading of the left and right fore limbs), or with the head voluntary turned to the right or to the left (asymmetrical loading). We found that postural corrective responses to tilts included an increase of the contact forces and activity of limb extensors on the side moving down, and their decrease on the opposite side. The activity of PTNs was strongly modulated in relation to the tilt cycle. Phases of activity of individual PTNs were distributed over the cycle. Thus the cortical output mediated by PTNs appeared closely related to a highly automatic motor activity, the maintenance of the body posture. An asymmetrical loading of limbs, caused by head turns, resulted in the corresponding changes of motor responses to tilts. These voluntary postural modifications were also well reflected in the PTNs' activity. The activity of a part of PTNs correlated well with contact forces, in some others with the limb muscle activity; in still others no correlation with these variables was observed. This heterogeneity of the PTNs population suggests a different functional role of individual PTNs.

scholarly journals Slowly-conducting pyramidal tract neurons in macaque and rat

2019 ◽  
Author(s):  
A Kraskov ◽  
D Soteropoulos ◽  
I Glover ◽  
RN Lemon ◽  
SN Baker
Keyword(s):  
Motor Cortex ◽  
Pyramidal Tract ◽  
Recurrent Inhibition ◽  
Anatomical Studies ◽  
Slow Conduction ◽  
Pyramidal Tract Neurons ◽  
Conduction Velocities ◽  
Myelinated Fibres ◽  
Anaesthetised Rats

SummaryAnatomical studies report a large proportion of fine myelinated fibres in the primate pyramidal tract (PT), while very few pyramidal tract neurons (PTNs) with slow conduction velocities (CV) (< ∼10 m/s) are reported electrophysiologically. This discrepancy might reflect recording bias towards fast PTNs or prevention of antidromic invasion by recurrent inhibition of slow PTNs from faster axons. We investigated these factors in recordings made with a polyprobe (32 closely-spaced contacts) from motor cortex of anaesthetised rats (n=2) and macaques (n=3), concentrating our search on PTNs with long antidromic latencies. We identified 21 rat PTNs with antidromic latencies > 2.6 ms and estimated CV 3-8 m/s, and 67 macaque PTNs (> 3.9ms, CV 6-12 m/s). Spikes of most slow PTNs were small and present on only some recording contacts, while spikes from simultaneously recorded fast-conducting PTNs were large and appeared on all contacts. Antidromic thresholds were similar for fast and slow PTNS, while spike duration was considerably longer in slow PTNs. Most slow PTNs showed no signs of failure to respond antidromically. A number of tests, including intracortical microinjection of bicuculline (GABAA antagonist), failed to provide any evidence that recurrent inhibition prevented antidromic invasion of slow PTNs. Our results suggest that recording bias is the main reason why previous studies were dominated by fast PTNs.

Responses of primate SI cortical neurons to noxious stimuli

1983 ◽  
Vol 50 (6) ◽  
pp. 1479-1496 ◽  
Author(s):  
D. R. Kenshalo ◽  
O. Isensee
Keyword(s):  
Receptive Field ◽  
Cortical Neurons ◽  
Receptive Fields ◽  
The Body ◽  
Thermal Stimulation ◽  
Discharge Frequency ◽  
Mechanical Stimuli ◽  
Noxious Heat ◽  
Nociceptive Neurons ◽  
Heat Pulses

Recordings were made from single SI cortical neurons in the anesthetized macaque monkey. Each isolated cortical neuron was tested for responses to a standard series of mechanical stimuli. The stimuli included brushing the skin, pressure, and pinch. The majority of cortical neurons responded with the greatest discharge frequency to brushing the receptive field, but neurons were found in areas 3b and 1 that responded maximally to pinching the receptive field. A total of 68 cortical nociceptive neurons were examined in 10 animals. Cortical neurons that responded maximally to pinching the skin were also tested for responses to graded noxious heat pulses (from 35 to 43, 45, 47, and 50 degrees C). If the neuron failed to respond or only responded to 50 degrees C, the receptive field was also heated to temperatures of 53 and 55 degrees C. Fifty-six of the total population of nociceptive neurons were tested for responses to the complete series of noxious heat pulses: 46 (80%) exhibited a progressive increase in the discharge frequency as a function of stimulus intensity, and the spontaneous activity of two (4%) was inhibited. One population of cortical nociceptive neurons possessed restricted, contralateral receptive fields. These cells encoded the intensity of noxious mechanical and thermal stimulation. Sensitization of primary afferent nociceptors was reflected in the responses of SI cortical nociceptive neurons when the ascending series of noxious thermal stimulation was repeated. The population of cortical nociceptive neurons with restricted receptive fields exhibited no adaptation in the response during noxious heat pulses of 47 and 50 degrees C. At higher temperatures the response often continued to increase during the stimulus. The other population of cortical nociceptive neurons was found to have restricted, low-threshold receptive fields on the contralateral hindlimb and, in addition, could be activated only by intense pinching or noxious thermal stimuli delivered on any portion of the body. The stimulus-response functions obtained from noxious thermal stimulation of the contralateral hindlimb were not different from cortical nociceptive neurons with small receptive fields. However, nociceptive neurons with large receptive fields exhibited a consistent adaptation during a noxious heat pulse of 47 and 50 degrees C. Based on the response characteristics of these two populations of cortical nociceptive neurons, we conclude that neurons with small receptive fields possess the ability to provide information about the localization, the intensity, and the temporal attributes of a noxious stimulus.4+.

Lateral cervical nucleus of the dog: anatomical and microelectrode studies

1965 ◽  
Vol 209 (2) ◽  
pp. 307-311 ◽  
Author(s):  
S. T. Kitai ◽  
H. Ha ◽  
F. Morin
Keyword(s):  
Cell Size ◽  
Single Unit ◽  
Canis Familiaris ◽  
Receptive Fields ◽  
Afferent Input ◽  
The Body ◽  
Medial Lemniscus ◽  
Joint Movement ◽  
Cell Counts ◽  
Lateral Cervical Nucleus

The lateral cervical nucleus (LCN) of the dog ( Canis familiaris) was investigated by histological and microelectrode technique. The LCN extends from the obex to the upper C3 and is located ventrolateral to the dorsal horn. Cell counts showed over 6,000 cells in the nuclei on both sides and the cell size varied from 20 to 45 µ. Single-unit analysis of the 220 neurons showed that the majority of cells responded to touch, some to pressure, some to pressure and touch, and an extremely limited number to joint movement. All responses were recorded from the ipsilateral half of the body. More than half of these neurons had small peripheral receptive fields located mostly in the distal parts of the limbs. The rest, with large receptive fields, were located mainly in the proximal parts of the limbs and the trunk. The peripheral receptive fields were almost equally distributed among the forelimb, trunk, and hindlimb for touch. The prominence of the hindlimb representation over the forelimb was found for pressure and for touch and pressure. The results indicate that the organization of the afferent input to the LCN has some similarity to that of the medial lemniscus system.

Functional properties of single neurons in the face primary motor cortex of the primate. II. Relations with trained orofacial motor behavior

1992 ◽  
Vol 67 (3) ◽  
pp. 759-774 ◽  
Author(s):  
G. M. Murray ◽  
B. J. Sessle
Keyword(s):  
Motor Cortex ◽  
Cortical Neurons ◽  
Primary Motor Cortex ◽  
Motor Behavior ◽  
Afferent Input ◽  
Single Neurons ◽  
Tongue Protrusion ◽  
Input And Output ◽  
The Face ◽  
Tongue Movements

1. The previous paper has described in detail the input and output features of single neurons located at sites within primate face motor cortex from which intracortical microstimulation (ICMS, less than or equal to 20 microA) evoked tongue movements at the lowest threshold ("tongue-MI" sites); for comparative purposes, we also reported on the input and output features of a smaller number of neurons recorded at sites from which ICMS could evoke jaw movements ("jaw-MI" sites), facial movements ("face-MI" sites), or, at a few sites, tongue movements and, at the same threshold intensity, either a jaw movement or a facial movement. 2. Our findings of an extensive and diverse representation of sites within face motor cortex of monkeys for the generation of elemental components of tongue movement, and the relatively few sites from which jaw-closing movements could be evoked, were consistent with our recent observations that reversible, cooling-induced inactivation of the face motor cortex severely impaired the performance by monkeys of a tongue-protrusion task but had only relatively minor effects on the performance of a biting task. In an attempt to establish a neuronal correlate for these different behavioral relations, the present study has documented the task-related activities of those single neurons that were characterized in the previous paper in terms of afferent input and ICMS-defined output features. 3. Each task required the development and maintenance by each monkey of a fixed force level for a minimum period of time to obtain a fruit-juice reward. During one or both of these tasks, we characterized the activities of 231 single face motor cortical neurons that were located at the above-mentioned ICMS-defined sites. Neurons were said to be related to a particular task if they showed statistically significant differences in firing rates during the task in comparison with a control pretrial period (PTP). 4. In tongue-MI, there was a significantly higher proportion of neurons (63% of 156 neurons tested) that were related to the tongue-protrusion task than to the biting task (15% of 65). However, in jaw-MI the proportion of neurons that were biting task-related (63% of 19) was significantly higher than the proportion related to the tongue-protrusion task (11% of 9); the proportion of biting task-related neurons at ICMS-defined jaw-closing sites was also higher than that at jaw-opening sites.(ABSTRACT TRUNCATED AT 400 WORDS)

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