Dynamics of neck-to-forelimb reflexes in the decerebrate cat

1983 ◽  
Vol 50 (3) ◽  
pp. 688-695 ◽  
Author(s):  
K. Ezure ◽  
V. J. Wilson
Keyword(s):  
Head Rotation ◽  
Longitudinal Axis ◽  
Triceps Brachii ◽  
Vestibular Reflexes ◽  
Sinusoidal Analysis ◽  
Low Frequencies ◽  
Decerebrate Cat ◽  
Splenius Capitis ◽  
Response Phase ◽  
Stimulation Of

We have studied the neck-to-forelimb reflex evoked by head rotation around the longitudinal axis (roll) in the long and medial heads of triceps brachii of decerebrate, acutely labyrinthectomized cats. Reflexes were measured by recording mass electromyogram (EMG). As expected from the work of others, they were reciprocal in the two limbs, with excitation in the limb toward which the chin rotates. The reflex was sufficiently linear for a sinusoidal analysis. Although there was sometimes adaptation at stimulus frequencies of 0.1 Hz and below, response phase at these frequencies was usually in phase with position, and gain was flat. At higher frequencies there was some sensitivity to the velocity of the stimulus: gain increased with a slope of 10 dB/decade and phase advanced in some cats but not in others. Gain at low frequencies of head rotation, expressed as percent modulation of EMG, was typically 1%/deg or less. Reflexes evoked by head rotation in triceps and in the neck extensor splenius capitis have different dynamics. It remains to be determined whether this difference is due to activation of different receptors. We compared the dynamics of roll reflexes evoked by stimulation of neck receptors with those of vestibular reflexes evoked by tilt of the whole animal (23). Taking into account dynamics and gain, the two reflexes should cancel at low frequencies, as predicted by others. Above 0.2 Hz, cancellation becomes less effective.

Responses of medullary reticulospinal neurons to sinusoidal stimulation of labyrinth receptors in decerebrate cat

1983 ◽  
Vol 50 (5) ◽  
pp. 1059-1079 ◽  
Author(s):  
D. Manzoni ◽  
O. Pompeiano ◽  
G. Stampacchia ◽  
U. C. Srivastava
Keyword(s):  
Phase Angle ◽  
Intermediate Phase ◽  
Longitudinal Axis ◽  
Peak Amplitude ◽  
Slow Rotation ◽  
Medullary Reticular Formation ◽  
Peak Displacement ◽  
Decerebrate Cat ◽  
Reticulospinal Neurons ◽  
Stimulation Of

The electrical activity of 168 individual neurons located in the medullary reticular formation, namely, in the medial aspects of the nucleus reticularis gigantocellularis, magnocellularis, and ventralis, has been recorded in precollicular decerebrate cats during sinusoidal tilt about the longitudinal axis of the whole animal, leading to stimulation of labyrinth receptors. In particular, 93 neurons were activated antidromically by stimulation of the spinal cord at T12 and L1 (1RS neurons); the remaining 75 neurons were not activated antidromically (RF neurons). Among these medial reticular neurons tested, 64 of 93 (i.e., 69%) 1RS neurons and 49 of 75 (i.e., 65%) RF neurons responded to slow rotation of the animal at the standard frequency of 0.026 Hz and at the peak amplitude of displacement of 10 degrees. A periodic modulation of firing rate of the units was observed during the sinusoidal stimulus. In particular, 71 of 113 units (i.e., 63%) were excited during side-up and depressed during side-down tilt, whereas 24 of 113 units (i.e., 21%) showed the opposite behavior. In both instances, the peak of the responses occurred with an average phase lead of about +25 degrees with respect to the extreme side-up or side-down position of the animal. The remaining 18 units (i.e., 16%) showed a prominent phase shift of the peak of their response with respect to animal position. Within the explored region of the medulla, the proportion of units excited during side-up tilt was higher at caudal levels, whereas that of the units excited during side-down tilt was higher at rostral levels. Units displaying intermediate phase angle of the responses predominated at intermediate levels of the medulla. Responses to animal tilt were detectable at 1 degree of peak displacement. The gain (impulses x s-1 x deg-1) of the responses of reticulospinal neurons did not change by increasing the peak amplitude of tilt from 5 to 20 degrees at the fixed frequency of 0.026 Hz. This finding indicates that the system was relatively linear with respect to the amplitude of displacement. By varying the frequency of stimulation from 0.008 to 0.32 Hz at the fixed amplitude of 10 degrees, two populations of reticulospinal neurons were observed. In the first, the gain and the phase angle of response remained relatively unmodified against changes in frequencies: these positional responses were attributed to stimulation of macular receptors.(ABSTRACT TRUNCATED AT 400 WORDS)

Interaction of Vestibular and Proprioceptive Reflexes in the Decerebrate Cat

1956 ◽  
Vol 185 (3) ◽  
pp. 607-613 ◽  
Author(s):  
Werner P. Koella ◽  
Hiroyuki Nakao ◽  
Robert L. Evans ◽  
Jun Wada
Keyword(s):  
Stretch Reflex ◽  
Muscle Spindles ◽  
Longitudinal Axis ◽  
Strain Gauges ◽  
Vestibular Apparatus ◽  
Triceps Brachii ◽  
Decerebrate Cat ◽  
Proprioceptive Reflexes ◽  
The Difference ◽  
Decerebrate Cats

The quantitative interrelation between stretch, tension and position in space was studied in decerebrate cats. The tension produced by the isolated M. triceps brachii was recorded by means of strain gauges. It was found that the tension increment, produced by a particular stretch, increases as the preparation is turned from the prone to the supine position around its longitudinal axis. The proportion between the tensions produced by a series of two or more different stretches, however, stays constant under these conditions. It was shown, furthermore, that the effect of a change in position upon the degree of rigidity—i.e., the difference between the tensions in the prone and in the supine positions—is the greater the greater the initial stretch. A quantitative analysis of the results disclosed that the vestibular factor and the proprioceptive factor are related in a multiplicative manner. These experiments show that the vestibular apparatus and the muscle spindles exert their influence not in an isolated and independent, but a quantitatively interdependent manner. The results of the present work together with the findings of other authors (Granit) give strength to the argument that the vestibular apparatus controls the stretch reflex activity in an indirect manner, i.e., over the ‘by-pass’ of the gamma-efferents.

Spatial organization of neck and vestibular reflexes acting on the forelimbs of the decerebrate cat

1986 ◽  
Vol 55 (3) ◽  
pp. 514-526 ◽  
Author(s):  
V. J. Wilson ◽  
R. H. Schor ◽  
I. Suzuki ◽  
B. R. Park
Keyword(s):  
Spatial Organization ◽  
Stimulus Frequency ◽  
Semicircular Canals ◽  
Head Rotation ◽  
Otolith Organs ◽  
Vestibular Reflexes ◽  
Decerebrate Cat ◽  
Shoulder Muscles ◽  
Long Head ◽  
Vector Orientation

EMG recording was used to study the spatial organization of vestibular and tonic neck reflexes acting on forelimb and shoulder muscles of the decerebrate cat. Neck reflexes were studied in preparations with intact labyrinths as well as those with acute or chronic labyrinthectomies. Reflexes were described by response vectors whose orientation component is aligned with the optimal excitatory direction of tilt or head rotation. A muscle's vector orientation remained reasonably stable over a period of hours, although there was sometimes drift at the beginning or end of an experiment. Orientation of muscle response vectors did not change systematically with stimulus frequency of 0.05-2.0 Hz. For vestibular reflexes this is so, although their dynamics are consistent with convergent input from semicircular canals and otolith organs. Regardless of the preparation, a consistent reflex pattern emerged. Vestibular reflexes are characterized by response vector orientation near ear-down roll. Neck vector orientation lies in the opposite direction from the vestibular vector but typically lies further from the roll plane: Nose-up pitch is excitatory for the shoulder muscles supra- and infraspinatus, and for the medial and lateral heads of triceps, whereas nose-down pitch excites the long head of triceps. Our results generally agree with the pattern proposed by Roberts (28) for neck reflexes but disagree in part with his proposed pattern of vestibular reflexes; we did not see the expected consistent excitation by nose-down pitch.

Responses of lateral reticular neurons to sinusoidal stimulation of labyrinth receptors in decerebrate cat

1980 ◽  
Vol 44 (5) ◽  
pp. 922-936 ◽  
Author(s):  
L. Kubin ◽  
P. C. Magherini ◽  
D. Manzoni ◽  
O. Pompeiano
Keyword(s):  
Firing Rate ◽  
Longitudinal Axis ◽  
Vestibular Nuclei ◽  
Peak Amplitude ◽  
Reticular Nucleus ◽  
Slow Rotation ◽  
Medullary Reticular Formation ◽  
Decerebrate Cat ◽  
Reticular Neurons ◽  
Stimulation Of

1. The electrical activity of 106 individual neurons located in the precerebellar lateral reticular nucleus (NRL) and the surrounding medullary reticular formation (RF) has been recorded in precollicular decerebrate cats during sinusoidal tilt around the longitudinal axis of the whole animal leading to stimulation of labyrinth receptors. 2. Among these lateral reticular neurons tested, 48 of 712 (67.6%) NRL neurons and 11 of 35 (31.4%) RF neurons responded to slow rotation of the animal at the standard frequency of 0.026 Hz and at the peak amplitude of displacement of 5-10 degrees. 3. All the responsive units showed a periodic modulation of firing rate during the sinusoidal stimulus. In particular, 35 of 57 units (i.e., 61.4%) were excited during side-up and depressed during side-down tilt of the whole animal; on the other hand, 14 of 57 units (i.e., 24.6%) showed the opposite behavior. In both instances, the peak of the responses occurred with an average phase lead of about 16 degrees with respect to the extreme side-up or side-down position of the animal. The remaining eight units (i.e., 14%) showed a phase shift of the peak of their response of about 90 degrees with respect to the animal position. 4. The sensitivity of the responses, expressed in percentage change of the average firing rate per degree of displacement, did not change by increasing the peak amplitude of tilt from 5 to 15 degrees at the frequency of 0.026 Hz. This finding indicates that the system was relatively linear with respect to the amplitude of stimulation. The sensitivity of the units, however, slightly increased but the phase angle of the responses did not change by increasing the frequency of tilting from 0.015 to 0.15 Hz at the peak amplitude of 5 or 10 degrees. These findings indicate that the responses depended on stimulation of macular labyrinth receptors. 5. Most of the lateral reticular units affected by tilt received also a bilateral convergent input from the hindlimbs. 6. These observations are related to the results of previous studies in which the responses of macular afferents, vestibular nuclei neurons, and corticocerebellar Purkinje (P) cells to sinusoidal tilt of the whole animal have been investigated. A possible role of lateral reticular neurons in the labyrinth control of posture in decerebrate cat is also discussed.

Detection of diaphragmatic fatigue in man by phrenic stimulation

1981 ◽  
Vol 50 (3) ◽  
pp. 538-544 ◽  
Author(s):  
M. Aubier ◽  
G. Farkas ◽  
A. De Troyer ◽  
R. Mozes ◽  
C. Roussos
Keyword(s):  
Phrenic Nerve ◽  
Chronic Obstructive Lung Disease ◽  
Chronic Obstructive ◽  
Low Frequencies ◽  
Transdiaphragmatic Pressure ◽  
Control Value ◽  
Transcutaneous Stimulation ◽  
Diaphragmatic Fatigue ◽  
Residual Capacity ◽  
Stimulation Of

Transdiaphragmatic pressure (Pdi) was measured at functional residual capacity (FRC) in four normal seated subjects during supramaximal, supraclavicular transcutaneous stimulation of one phrenic nerve (10, 20, 50, and 100 Hz--0.1 ms duration) before and after diaphragmatic fatigue, produced by breathing through a high alinear inspiratory resistance. Constancy of chest wall configuration was achieved by placing a cast around the abdomen and the lower one-fourth of the rib cage. Pdi increased with frequency of stimulation, so that at 10, 20, and 50 Hz, the Pdi generated was 32 +/- 4 (SE), 70 +/- 3, and 98 +/- 2% of Pdi at 100 Hz, respectively. After diaphragmatic fatigue, Pdi was less than control at all frequencies of stimulation. Recovery for high stimulation frequencies was complete at 10 min, but at low stimulation frequencies recovery was slow: after 30 min of recovery, Pdi at 20 Hz was 31 +/- 7% of the control value. It is concluded that diaphragmatic fatigue can be detected in man by transcutaneous stimulation of the phrenic nerve and that diaphragmatic strength after fatigue recovers faster at high than at low frequencies of stimulation. Furthermore, it is suggested that this long-lasting element of fatigue might occur in patients with chronic obstructive lung disease, predisposing them to respiratory failure.

The release of catecholamines from the adrenal medulla and its modulation by α2-adrenoceptors in the anaesthetized dog

1987 ◽  
Vol 65 (4) ◽  
pp. 550-557 ◽  
Author(s):  
Sylvain Foucart ◽  
Réginald Nadeau ◽  
Jacques de Champlain
Keyword(s):  
Electrical Stimulation ◽  
Adrenal Medulla ◽  
Plasma Concentrations ◽  
Splanchnic Nerve ◽  
Feedback Mechanism ◽  
Adrenal Vein ◽  
Low Frequencies ◽  
Negative Feedback Mechanism ◽  
Frequency Of Stimulation ◽  
Stimulation Of

The adrenal nerve of anaesthetized and vagotomized dogs was electrically stimulated (10 V pulses of 2 ms duration for 10 min) at frequencies of 1, 3, 10, and 25 Hz. There was a correlation between the frequency of stimulation and the plasma concentrations of epinephrine, norepinephrine, and dopamine in the adrenal vein, mainly after the 1st min of stimulation and the maximal concentration was reached sooner with higher frequencies of stimulation. Moreover, the relative percentage of catecholamines released in response to the electrical stimulation was not changed by the frequency of stimulation. To test the hypothesis that a local negative feedback mechanism mediated by α2-adrenoceptors exists in the adrenal medulla, the effects of the systemic administration of clonidine (α2-agonist) and yohimbine (α2-antagonist) on the concentrations of catecholamines in the adrenal vein were evaluated during the electrical stimulation of the adrenal nerve (5 V pulses of 2 ms duration for 3 min) at 3 Hz. Moreover, the effects of the systemic injections of more specific α2-agonist and antagonist (oxymetazoline and idazoxan) were tested on the release of catecholamines in the adrenal vein in response to electrical stimulation of the splanchnic nerve at 1 and 3 Hz frequencies. The injection of 0.5 mg/kg of yohimbine caused a significant increase in the concentrations of epinephrine and norepinephrine in the adrenal vein induced by the electrical stimulation of the adrenal nerve and the injection of 15 μg/kg of clonidine had no effects. In the second series of experiments, the injection of 2 μg/kg of oxymetazoline caused a significant decrease in the release of epinephrine and norepinephrine at 1 Hz, but similarly to clonidine, there were no changes at 3 Hz. In contrast, the release of epinephrine and dopamine in response to electrical stimulation of the splanchnic nerve was increased at 3 Hz after the injection of idazoxan, but not at 1 Hz. It is concluded that the adrenal medulla catecholamines secretion appears to be partly modulated by a presynaptic inhibitory mechanism that involves α2-adrenoceptors. The observation that agonists appear to be more efficient at low frequencies of stimulation while antagonists appear to be more efficient at higher frequencies could be explained by the possibility that adrenal medullary α2-receptors would be saturated at higher frequencies of stimulation.

Motor-unit recruitment in the decerebrate cat: several unit properties are equally good predictors of order

1991 ◽  
Vol 66 (4) ◽  
pp. 1127-1138 ◽  
Author(s):  
T. C. Cope ◽  
B. D. Clark
Keyword(s):  
Motor Unit ◽  
Rank Order ◽  
Motor Units ◽  
Afferent Input ◽  
Medial Gastrocnemius ◽  
Size Principle ◽  
Recruitment Pattern ◽  
Decerebrate Cat ◽  
Recruitment Order ◽  
Stimulation Of

1. Recruitment order was studied in pairs of motor units of the medial gastrocnemius (MG) muscle of decerebrate cats with the use of dual microelectrode recording from intact ventral root filaments. Excitation was provided by stretch of MG, stretch of synergists [lateral gastrocnemius (LG), plantaris (PL), and soleus (SOL) muscles] or electrical stimulation of the caudal cutaneous sural (CCS) nerve. Motor units were characterized by axonal conduction velocity (CV), tetanic tension (Pmax), twitch contraction time (CT), and fatigue index (FI). 2. Consistent with the recruitment pattern described by others, most often in relation to either CV or Pmax, the first unit of a pair to be recruited by MG stretch was typically the one with the lower CV and Pmax, and the higher FI and CT. The proportion of pairs that agreed in rank order of each property and recruitment order was as follows: for CT, 94%; for CV, 87%; for Pmax, 84%; and for FI, 75%. With a single marginal exception (CT vs. FI), no motor-unit property proved to be significantly better than the others at predicting recruitment (G test; P greater than 0.05). 3. In all 11 tested pairs containing one slow (type S) and one fast (type F) unit, the S was more easily recruited by stretch. Type F units divided into groups with high (type FR), low (type FF), and intermediate (type FInt) values for FI were recruited in order from FR to FInt to FF in 8/11 pairs. Thus our findings were similar to earlier demonstrations that recruitment proceeds in order by type. 4. Stretch of MG synergists usually recruited units in the same order as MG stretch. In two S-S pairs, recruitment order was switched with synergist stretch. 5. Stimulation of the CCS nerve was generally excitatory to the MG units sampled. Most unit pairs were recruited by CCS stimulation in the same order as by MG stretch, but, for 6 of 39 pairs, CCS stimulation switched the order produced by stretch. Thus, whereas sural afferent input can preferentially excite some units over others as suggested by Kanda et al., that effect is not widespread or selective for unit type under these conditions. 6. Assuming that all MG motor units cooperate as a single functional pool in homonymous stretch reflexes, we support others in concluding that a motoneuron's recruitment threshold is not strictly determined by its size. However, our data do not distinguish other schemes that predict recruitment order more accurately than the size principle.(ABSTRACT TRUNCATED AT 400 WORDS)

Tilt responses of neurons in the caudal descending nucleus of the decerebrate cat: influence of the caudal cerebellar vermis and of neck receptors

1996 ◽  
Vol 75 (3) ◽  
pp. 1242-1249 ◽  
Author(s):  
V. J. Wilson ◽  
H. Ikegami ◽  
R. H. Schor ◽  
D. B. Thomson
Keyword(s):  
Head Rotation ◽  
Muscle Spindles ◽  
Vestibular Nuclei ◽  
Vestibular Stimulation ◽  
Cerebellar Vermis ◽  
Neck Muscle ◽  
Vestibular Input ◽  
Decerebrate Cat ◽  
Neck Rotation ◽  
Vertical Semicircular Canal

1. In decerebrate cats with intact cerebellums, we studied the responses of neurons in the caudal areas of the vestibular nuclei to natural vestibular stimulation in vertical planes and to neck rotation. The activity of most neurons was recorded in the caudal half of the descending nucleus. 2. One goal of our experiments was to compare the dynamic and spatial properties of responses to sinusoidal vestibular stimulation with those seen in previous experiments in which the caudal cerebellar vermis, including the nodulus and uvula, was removed. This part of the cerebellum receives vestibular input and projects to the caudal areas of the vestibular nuclei, suggesting that it could influence responses to stimulation of the labyrinth. 3. As in our previous experiments, most neurons could be classified as receiving predominant input either from the otoliths or from one vertical semicircular canal. When mean gain and phase and response vector orientations were compared, there were no obvious differences between the behavior of neurons in the partially decerebellate preparation and the one with the cerebellum intact, demonstrating that in the decerebrate cat the nodulus and uvula have little or no influence on the processing of vertical vestibular input in this region of the vestibular nuclei. 4. Only 23 of 74 (31%) of neurons tested responded to neck rotation. This contrasts with the much larger fractions that respond to this stimulus in Deiters' nucleus and in the rostral descending nucleus. We also recorded from neurons near the vestibular nuclei, mainly in the external cuneate nucleus. All of them (9 of 9) responded to neck rotation. 5. Responses to neck rotation also differed in their dynamics from those found more rostrally in the vestibular nuclei. Dynamics of more rostral neurons resemble those of neck muscle spindles, as do those of external cuneate neurons. The dynamics of caudal vestibular neurons, on the other hand, have a steeper gain slope and more advanced phases than do those of neurons in the more rostral vestibular nuclei. This suggests the possibility of involvement of additional receptors in the production of these responses. 6. In the more rostral vestibular nuclei, responses to vestibular and neck rotation are most often antagonistic, so that head rotation results in little or no response. This is not the case in the caudal areas of the vestibular nuclei, where less than half the neurons tested displayed antagonistic behavior. Further experiments are required to put the neck projection to the caudal vestibular nuclei in a functional context.

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