Symposium on the Role of the Vestibular Organs in Space Exploration (1970) / Chapter Skim
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INTERACTION BETWEEN VESTIBULAR AND NONVESTIBULAR SENSORY INPUTS
INTERACTION BETWEEN VESTIBULAR AND NONVESTIBULAR SENSORY INPUTS
Pages 209-236
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From page 209... ...
This postsynaptic event, together with the presynaptic mechanism, contributes to the phasic depression of transmission of somatic afferent volleys through the cuneate nucleus at the time of the REM. Lesion experiments indicate that the increase in the vestibular activity occurring during REM is able to block the transmission of somatic afferent volleys within the dorsal-column nuclei through the roundabout way of the sensory-motor cortex.
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From page 210... ...
. While during wakefulness the activity of the second-order vestibular neurons largely depends upon the discharge of different types of labyrinthine receptors, during desynchronized sleep the increase in the activity of the vestibular neurons, particularly those localized in the medial and descending vestibular nuclei, depends upon internal extralabyrinthine volleys.
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From page 211... ...
which are invariably associated with the ocular movements typical of this phase of sleep. The increased activity of the units localized in the medial and descending vestibular nuclei indicates that these structures are in some way related to REM occurring during desynchronized sleep.
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From page 212... ...
In this experimental condition the episodes of desynchronized sleep are simply characterized by the typical low-voltage, fast activity in the EEG and by complete abolition of the neck muscular activity. The integrity of the medial and descending vestibular nuclei is necessary not only
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From page 213... ...
for the response. Observations in which the orthodromic lemniscal response was recorded simultaneously with the antidromic volley led from a branch of the superficial radial nerve, distally to the stimulating electrode, clearly showed that the threshold for the orthodromic lemniscal response corresponded to about 1.05 times the threshold for the antidromic group II volley (ref.
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From page 214... ...
b. c IOms« FIGURE 2. -- Modulation of the orthodromic lemniscal response during a typical episode of desynchronized sleep.
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From page 215... ...
The records indicate the orthodromic lemniscal responses recorded from the right medial lemniscus following stimulation of the left superficial radial nerve before (a) , during (b)
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From page 216... ...
It can be concluded that somatic afferent transmission through the dorsal-column system is greatly depressed during the REM periods of desynchronized sleep. Presynaptic and Postsynaptic Inhibition of Transmission of Somatic Afferent Volleys Through the Cuneate Nucleus During REM The experiments reported in the previous section have led to the conclusion that the sleep modulation of the orthodromic lemniscal response was mainly caused by reduced transmission of somatic afferent volleys through the dorsalcolumn pathway.
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From page 217... ...
It was then possible to study in the unrestrained, unanesthetized animal either the modulation during sleep of the antidromic responses, recorded monopolarly from the superficial or the deep radial nerve, or the modulation of the orthodromic lemniscal responses to direct stimulation of the cuneate nucleus. In some experiments both types of responses could be recorded simultaneously or separately during successive episodes of sleep.
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From page 218... ...
During the transition from quiet waking to synchronized sleep, no significant changes in either mean amplitude or standard deviation of group II antidromic volleys were recorded from the superficial radial nerve, nor was there any clear-cut difference found between the periods characterized by trains of synchronous waves and the interspindle lulls. The main changes in amplitude of the antidromic volley occurred during desynchronized sleep.
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From page 219... ...
On the contrary, the mean amplitude and the standard deviation of the responses recorded during the same episodes of desynchronized sleep in the absence of REM closely corresponded to the values obtained during synchronized sleep. A correlation between increase in the antidromic group II cutaneous volley and ocular movements turned out to be particularly evident when the bursts of REM were composed of high-rate, large-amplitude movements (fig.
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From page 220... ...
The dots represent the amplitudes of the antidromic group 11 cutaneous volley recorded from the left superficial radial nerve on single-shock stimulation of the ipsilateral cuneate nucleus during the REM periods of desynchronized sleep. The abscissa indicates the repetition rate (c/s)
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From page 221... ...
. The records show 15 antidromic responses of group 1 muscular fibers led from the left deep radial nerve following single-shock stimulation of the cuneate nucleus before (1-5)
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From page 222... ...
Figure 9 shows the changes in amplitude of both the lemniscal responses elicited by direct stimulation of the cuneate nucleus during desynchronized sleep and their depression at the time of the large bursts of REM, while figure 10 illustrates those responses plotted in figure 9 which occur at the time of two large bursts of REM. To obtain a statistical evaluation of the relative depression affecting a- and /3-spikes during REM, the mean amplitude of both the responses occurring during phasic bursts of ocular movements was compared with the mean amplitude of the responses that occurred during the same episodes of desynchronized sleep, but in the absence of REM.
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From page 223... ...
B C: Episode of desynchronized sleep, during which time there are phasic depressions of the lemniscal responses.
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From page 224... ...
Also, this depression occurred during the REM periods. In figure 12 the mean amplitude and the standard deviations of such orthodromic and direct lemniscal responses recorded in the same experiment during different EEG backgrounds can be compared with the mean amplitude and the standard deviation of the antidromic group II cutaneous volley recorded in another experiment from the superficial radial nerve on singleshock stimulation of the cuneate nucleus during corresponding EEC backgrounds.
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From page 225... ...
-- Effects of sleep on the orthodromic lemniscal response and on the excitability both of cuneate neurons and of the presynaptic terminals in the cuneate nucleus. Filled circles: Orthodromic responses recorded from the right medial lemniscus (ML)
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From page 226... ...
Summing up, the structures which are responsible for the phasic depression of the orthodromic lemniscal response during desynchronized sleep must operate through both mechanisms of presynaptic and postsynaptic inhibition. Transmission of Sensory Volleys Through the Nucleus Ventralis Posterolateralis During REM Accumulated evidence indicates that during desynchronized sleep the transmission of somatic centripetal impulses elicited either by peripheral stimulation (refs.
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From page 227... ...
Middle records: Changes in antidromic responses recorded from ML to intrathalamic (VPL) stimulation during a REM burst of desynchronized sleep.
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From page 228... ...
Summing up, the depression of the orthodromic lemniscal response elicited by single-shock stimulation of the superficial radial nerve during the bursts of REM is abolished by a bilateral lesion of the vestibular nuclei, or by complete ablation of the sensory-motor cortex. It appears, therefore, that during REM, the vestibular nuclei depress the synaptic transmission at the level of the dorsal column nuclei through the roundabout way of the sensory-motor cortex and the pyramidal tract (fig.
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From page 229... ...
In both instances the responses were recorded from the right medial lemniscus on single-shock stimulation of the left superficial radial nerve. The results obtained during several episodes of desynchronized sleep have been statistically evaluated.
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From page 230... ...
Parallel to the phasic excitation of the extrinsic ocular and spinal motoneurons occurring during desynchronized sleep, phasic events influence the transmission of sensory inputs along the dorsal-column -- medial-lemniscal system. In particular, the experimental evidence clearly indicates that the orthodromic lemniscal response is phasically depressed during REM due to mechanisms of presynaptic and postsynaptic inhibition occurring within the cuneate nucleus (refs.
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From page 231... ...
One may propose that also during the natural labyrinthine stimulations in the awake animal, the somatosensory volleys originated at the time of the muscle contractions are not simply transmitted without alteration through the ascending lemniscal pathways. Similar to what has been described in the sleeping preparation, vestibular volleys may well interact with exteroceptive and proprioceptive afferent impulses at different relay stations of the somatosensory pathway, thus leading to proper perception during body movements.
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From page 232... ...
I Abolition of the Rapid Eye Movements During Desynchronized Sleep Following Vestibular Lesions.
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From page 233... ...
47. FAVALE, E.; LOEB, C.; MANFREDI, M.: AND SACCO, G.: Somatic Afferent Transmission and Cortical Responsiveness During Natural Sleep and Arousal in the Cat.
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From page 234... ...
N.; FAVALE, E.: LOEB, C.: AND MANFREDI. M.: Thalamic Transmission Changes During the Rapid Eye Movements of Deep Sleep.
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From page 235... ...
The result is that external stimulation due to somatic afferent volleys is partially substituted by internal stimulation due to vestibular afferent volleys which are incorporated at thalamic level and elaborated by the somatosensory cortex. It appears, therefore, as if a central discharge originating from the oculomotor centers in the brainstem reaches the VPL neurons simultaneously with the efferent discharge which gives rise to the limb and eye movements.
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From page 236... ...
Pompeiano: Nobody has so far watched for REM sleep in subjects who had lost all four extremities. Our observation that the REM bursts depend upon the activity of the vestibular nuclei has been recently confirmed in man (O.
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