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P D Cheney

Publications and source records attributed to P D Cheney.

50 records · Page 3Linked to original sources
PubMed1984

Corticomotoneuronal cells contribute to long-latency stretch reflexes in the rhesus monkey.

To test the hypothesis that a transcortical reflex contributes to the stretch-evoked long-latency electromyographic (e.m.g.) response we documented the responses of identified corticomotoneuronal (c.m.) cells and their target muscles to perturbations of active wrist movements. Macaque monkeys performed ramp-and-hold wrist movements against elastic loads, alternating between flexion and extension zones; brief (25 ms) torque pulses were intermittently applied during the hold period. C.m. cells were identified by a clear post-spike facilitation in spike-triggered averages of forelimb muscle e.m.g. activity. Activity of c.m. cells and twelve wrist and digit flexor and extensor muscles was recorded during: (a) active ramp-and-hold wrist movements, (b) passive ramp-and-hold wrist movements, and (c) torque perturbations applied during the hold phase of active flexion and extension which either lengthened or shortened the c.m. cell's target muscles. Muscle-lengthening perturbations evoked a reproducible pattern of average e.m.g. activity in the stretched muscles, consisting of two peaks: the first response (M1) had an onset latency of 11.2 +/- 2.1 ms (mean +/- S.D.), and the second (M2) began at 27.9 +/- 5.1 ms. Torque perturbations which shortened the active muscles also evoked a characteristic e.m.g. response consisting of an initial cessation of activity at 13.5 +/- 3.4 ms followed by a peak beginning at 33.9 +/- 3.0 ms. The responses of twenty-one c.m. cells which facilitated wrist muscles were documented with torque pulse perturbations applied during active muscle contraction. Twenty of twenty-one c.m. cells responded at short latency (23.4 +/- 8.8 ms) to torque perturbations which stretched their target muscles. For each c.m. cell-target muscle pair, transcortical loop time was calculated as the sum of the onset latency of the c.m. cell's response to lengthening perturbations (afferent time) and the onset latency of post-spike facilitation (efferent time). The mean transcortical loop time was 30.4 +/- 10.2 ms, comparable to the mean onset latency of the M2 peak (27.9 +/- 5.1). The duration of a c.m. cell's response to torque perturbations provides a further measure of the extent of its potential contribution to the M2 muscle response. In all cases but two, the c.m. cell response, delayed by the latency of the post-spike facilitation, overlapped the M2 e.m.g. peak.

Action Potentials↗
PubMed1983

Double-barreled electrode for simultaneous iontophoresis and single unit recording during movement in awake monkeys.

A double-barreled electrode for simultaneous glutamate iontophoresis and chronic single unit recording from cortical neurons in awake monkeys during voluntary movement is described. Electrode assembly consists of pulling a heated, partitioned capillary tube over a sharpened tungsten rod. Glutamate iontophoresis increased the firing rates of wrist movement related cells an average of 34 Hz during the agonist phase of movement and 27 Hz during the antagonist phase of movement. However, in no case did glutamate iontophoresis alter the detailed structure of the cell's response pattern during wrist movement. This electrode is well suited to chronic recording applications that involve methods such as cross-correlation requiring overlapping activity of neurons and/or muscles. Other applications might involve activation of totally 'silent' neurons to avoid possible sampling bias or to detect effects in post-stimulus time histograms that would otherwise be subliminal.

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PubMed1980

Response of rubromotoneuronal cells identified by spike-triggered averaging of EMG activity in awake monkeys.

Red nucleus neurons were recorded in awake monkeys during alternating ramp-and-hold wrist movements into flexion and extension position zones. Spike-triggered averages (STAs) of rectified EMG activity of wrist flexor and extensor muscles were computed to document effects of single RN cells on the activity of forelimb motoneurons. Some red nucleus cells produced a transient short-latency post-spike facilitation (PSF) of motor unit firing probability, indicative of underlying rubromotoneuronal (RM) connections. We, therefore, termed these RM cells. The discharge of wrist-related red nucleus cells was more strongly correlated with the dynamic than static component of wrist movement.

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PubMed1976

Classification and response characteristics of muscle spindle afferents in the primate.

A study was made of the response characteristics of spindle afferents in the baboon soleus muscle. Afferents were isolated from the dorsal roots, their conduction velocities were determined, and their responses were recorded to muscle stretch at rates of 2.5-45 mm/s and amplitudes of 2-10 mm. Spindle afferents could be classified as primary or secondary on the basis of two criteria. The first criterion was conduction velocity. The conduction velocity histogram was bimodal, with peaks at about 45 and 80 m/s and an intermediate region from 55 to 70 m/s. The second criterion was the pattern of adaptation following the peak of ramp stretch. This latter criterion has the advantage of allowing units with intermediate conduction velocities also to be confidently classified as primary or secondary. The velocity and position sensitivities of primate spindle afferents were determined. The mean dynamic index and mean dynamic sensitivity of secondary afferents were about 45% of the corresponding values for primary afferents. On the other hand, the position sensitivities of primary and secondary spindle afferents in the baboon were not significantly different.

Action Potentials↗
PubMed1976

Effects of fusimotor stimulation on dynamic and position sensitivities of spindle afferents in the primate.

The effects of stimulation of single static and dynamic fusimotor fibers on the dynamic sensitivity and position sensitivity of primary and secondary spindle afferents have been studied in the soleus muscle of the baboon. Static fusimotor fibers decreased the mean dynamic sensitivity of primary afferents at all rates of stretch and stimulation. The magnitude of the decrease in dynamic sensitivity increased as the rate of fusimotor stimulation was increased. Qualitatively similar effects were observed in secondary afferents. Static fusimotor stimulation had a strong excitatory effect on spindle afferent resting discharge and greatly increased the mean position sensitivity of both primary and secondary afferents. Dynamic fusimotor fibers increased the mean dynamic index of primary afferents at all rates of stretch and stimulation. The effect of dynamic fusimotor fibers on the mean dynamic sensitivity, however, was dependent on the rate of muscle stretch; at rates below 15 mm/s the dynamic sensitivity was substantially increased, whereas at rates greater than 15 mm/s it was either unchanged or decreased. Dynamic fusimotor fibers slightly decreased the mean position sensitivity of primary afferents.

Action Potentials↗
PubMed1976

Classification of fusimotor fibers in the primate.

The classification and distinguishing characteristics of fusimotor fibres of the baboon soleus muscle have been studied by determining the effects of single fusimotor fiber stimulation on the response of isolated spindle afferents to muscle stretch. As in the cat, fusimotor fibres in the baboon were divisible into static and dynamic types on the basis of the effect of their stimulation at 200/s on the dynamic index of the primary afferent. Single fusimotor fibres had the same qualitative effect-static or dynamic-on all the primary afferents they were found to influence. All static fusimotor fibres produced at least 1 to 1 driving of primary afferent discharge at 50/s if the muscle length was adjusted to optimize conditions for driving. In contrast, 31 of 32 dynamic fusimotor fibres did not produce driving of primary afferent discharge even though all were studied at many different muscle lengths and frequencies of stimulation. Therefore, fusimotor fibres in the baboon could be classified as static or dynamic on the basis of their ability to produce driving of the primary afferent. The ratio of isolated static to dynamic fusimotor fibers was 1.5 to 1. The mean conduction velocity of static fusimotor fibers was 24.1 m/s and that of dynamics was 20.2 m/s. Although the difference between these two means was statistically significant (P less than 0.001), the conduction velocity histograms of static and dynamic fusimotors overlapped, precluding classification by this means. Secondary afferents with one possible exception were concluded to be exclusively activated by static fusimotor fibers. Poststimulus effects of fusimotor stimulation on primary afferent response to stretch were studied. With intervals between the end of stimulation and the beginning of stretch of 0.1 s, dynamic fusimotor stimulation produced facilitation of the primary afferent response to stretch, whereas static fusimotor fibers produced depression.

Action Potentials↗
PubMed1976

Responses of cortical neurons (areas 3a and 4) to ramp stretch of hindlimb muscles in the baboon.

1. A study was made of the response of single cortical units in areas 3a and 4 to electrical stimulation of hindlimb muscle nerves and to ramp stretch of hindlimb muscles in baboons anesthetized with chloralose.2. Stimulation of hindlimb muscle nerves revealed a group I projection primarily to area 3a but with some input into adjacent area. 4. A major group II projection was found in area 4 adjacent to area 3a. A small number of area 3a neurons receive convergence from both group I and group II muscle afferents.3a. On the basis of their response pattern to ramp stretch, units were classified into one of six categories and their cytoarchitectonic location was determined. Units in area 3a had hynamic sensitivities equivalent to that of the primary spindle afferents. Although the discharge of some area 3a neurons also reflected differences in muscle length, most area 3a neurons had low position sensitivities. One unit type in area 3a did not respond to maintained muscle stretch and signaled only velocity of stretch.4. Units in area 4 had position sensitivities equivalent to that of primary and secondary spindle afferents. Although the discharge of some area 4 units reflected different velocities of muscle stretch, these units had dynamic sensitivities similar to those of secondary spindle afferents rather than those of primary afferents. One type of unit in area 4 had no dynamic component to muscle stretch and signaled only muscle length.5. The results demonstrate that there is a transfer of dynamic and position sensitivity from spindle afferents to cortical neurons. Furthermore, data processing has occurred because some units respond only to the steady-state length of muscle, while other units encode only the dynamic phase of stretch. This behavior is different from the responses to ramp stretch of either group I or group II muscle afferents in the baboon.6. The results demonstrate that single units in cerebral cortex can encode the information transmitted to the central nervous system by muscle spindle afferents. The purpose for which this information is used remains undetermined.

Action Potentials↗
PubMedDate not supplied

Encoding of motor parameters by corticomotoneuronal (CM) and rubromotoneuronal (RM) cells producing postspike facilitation of forelimb muscles in the behaving monkey.

This paper compares the properties of corticomotoneuronal (CM) and rubromotoneuronal (RM) cells identified by postspike facilitation (PSF) of rectified EMG activity in the awake monkey. The postspike effects of CM and RM cells in flexors and extensors of the wrist and fingers have been determined, as have the discharge properties of these cells in relation to alternating ramp-and-hold wrist movements. The characteristics of postspike facilitation and postspike suppression (PSS) were similar for RM and CM cells. The magnitude of RM-PSF was weaker than CM-PSF and RM cells showed a stronger preference for facilitation of extensor muscles than CM cells. As with CM cells, the onset of discharge in RM cells preceded the onset of EMG activity in their target muscles. Tonic discharge related to static torque was more prominent in CM cells, whereas phasic discharge was more prominent in RM cells; however, many RM cells showed some tonic activity weakly related to static torque. We conclude that CM and RM cells share many common features; however, RM cells are concerned primarily with the dynamics of muscle contraction.

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