Modification of the Motor Reflex Responses Due to Repetition of the Peripheral Stimulus in the Cockroach

1973 ◽  
Vol 59 (2) ◽  
pp. 359-381
Author(s):  
N. F. ZILBER-GACHELIN ◽  
M. P. CHARTIER
Keyword(s):  
Electrical Stimulation ◽  
Peripheral Stimulus ◽  
Excitatory Synapses ◽  
Nerve Response ◽  
Receptor Adaptation ◽  
Escape Reflex ◽  
Motor Reflex ◽  
Habituation Process ◽  
Transfer Properties ◽  
Stimulation Of

1. In the cockroach Blabera cranüfer repeated air puffs to the cerci induce a habituation of the corresponding escape reflex, which we have tried to relate to the transfer properties of the two central relays of the reflex. In this paper transmission through the first relay, the 6th abdominal ganglion (A.G.), was studied both by electrical stimulation of the sensory cereal nerve and by application of natural stimuli (air puffs) on the cerci, while recording simultaneously on the cereal nerve and the abdominal cord, i.e. respectively before and beyond the synaptic relay. 2. The electrical stimulation study shows transmission to be relatively labile. This property is still more apparent if air puffs are delivered. If they are separated by less than about 10 sec the cereal nerve response decreases, which is a sign of a receptor adaptation. For longer intervals, although this adaptation disappears, the response nevertheless decreases on the cord, implicating the ganglionic relay as the centre of a habituation phenomenon. 3. The characteristics of this habituation are the following: with repetition of the stimuli, the response decreases down to a non-zero plateau (decrease of about 50% if a puff is delivered every 20 sec); it recovers spontaneously if stimulations are suppressed ; habituation is potentiated when successive series of habituations followed by spontaneous restorations are accumulated; it is more pronounced as the stimulation frequency is increased; finally, it does not show generalization. These results confirm that the 6th A.G. independently exhibits a real habituation process. 4. The mechanism of this habituation process is discussed. A post-excitatory presynaptic depression intrinsic to the reflex's excitatory synapses themselves is tentatively proposed.

Modification of the Motor Reflex Responses Due to Repetition of the Peripheral Stimulus in the Cockroach

1973 ◽  
Vol 59 (2) ◽  
pp. 383-403
Author(s):  
N. F. ZILBER-GACHELIN ◽  
M. P. CHARTIER
Keyword(s):  
Motor Nerve ◽  
Spatial Summation ◽  
Minor Role ◽  
Peripheral Stimulus ◽  
Rhythmic Movements ◽  
Motor Responses ◽  
Escape Reflex ◽  
Motor Reflex ◽  
Time Courses ◽  
A Minor

1. The synaptic transfer properties within the 3rd thoracic ganglion (T.G.) from the abdominal cord axons to the motoneurones has been studied in the cockroach. This ganglion was completely de-afferented except for motor nerve 4, whose links with the muscles of the posterior legs were left intact. 2. The response of one of these nerves to electrical stimulation of the abdominal cord involves activation of 2 types of units: (a) Slow excitatory fibres which have a tonic discharge and respond to each lowthreshold abdominal cord stimulation by a transient increase of this firing rate; these units are responsible for muscular tonus and for low amplitude movements (startle reactions). (b) Fast excitatory fibres, which have no tonic discharge and require for their activation higher intensity and frequency of stimulation, i.e. an important temporal and spatial summation. They are responsible for larger and more rapid movements. They fire without any precise chronological relation with the stimuli, often in bursts which continue after the end of the stimulations and cause sudden rhythmic movements. 3. During repetition of the stimuli, the two types of synaptic pathways show both habituation and facilitation through temporal summation and post-tetanic potentiation. These two phenomena persist after the end of the stimulations and have long (minutes) but different time courses. Moreover, habituation always prevails over facilitation if stimulations are continued during a sufficient time. These antagonistic properties existing at the same time might explain the complex way in which the motor responses develop with the application of repetitive trains of stimuli to the cord. 4. The role of these properties in the changes of the reflex motor responses to successive air puffs applied to the cerci has been studied. These properties appear to be responsible for the sensitization of the responses which can be sometimes observed. They lead, in conjunction with the habituation properties of the 6th abdominal ganglion (A.G.), to the disappearance of the escape reflex involving firing of both fast and slow fibres. Finally, they seem to have a minor role in habituation of the startle reactions (involving firing of only the slow fibres) which would be mainly due to the 6th A.G. habituability.

Influence of VPM afferents on putative inhibitory interneurons in S1 of the awake rabbit: evidence from cross-correlation, microstimulation, and latencies to peripheral sensory stimulation

1995 ◽  
Vol 73 (4) ◽  
pp. 1584-1599 ◽  
Author(s):  
H. A. Swadlow
Keyword(s):  
Electrical Stimulation ◽  
Cortical Neurons ◽  
Response Times ◽  
Projection Neurons ◽  
Significant Shift ◽  
Peripheral Stimulus ◽  
Median Latency ◽  
Afferent Pathways ◽  
Antidromic Activation ◽  
Stimulation Of

1. Responses of thalamocortical projection neurons and suspected cortical interneurons (SINs) to very brief peripheral stimuli were examined within the vibrissae, the sinus hair, the lip, and the chin representations of ventroposterior medial thalamus (VPM) and primary somatosensory cortex (S1). VPM thalamocortical neurons (N = 40) were identified by their antidromic activation after electrical stimulation of S1. SINs were identified by a high-frequency (> 600 Hz) burst of three or more spikes elicited by suprathreshold stimulation of one or more afferent pathways. SINs also had spikes of very short duration. 2. Previous work has shown that electrical stimulation of VPM elicits a very early and powerful synaptic response in many S1 SINs. Three experimental strategies were employed to test the hypothesis that such responses reflect a monosynaptic VPM input onto SINs and to examine the effects of such input. 1) After a brief peripheral stimulus, the arrival times of VPM thalamocortical impulses in S1 were determined and compared with the initial response times of S1 SINs. 2) Shift-corrected cross-correlograms (CCGs) were constructed from the spike trains of pairs of VPM neurons and SINs that were in precise topographic alignment. 3) Inferences of connectivity based on such CCGs were supported by applying very low-intensity (1-10 microA) microstimulation pulses to the recording microelectrode in VPM and observing evoked responses in the cortical SIN. 3. VPM thalamocortical neurons responded to a brief air puff stimulus at a median latency of 5.05 ms, and the estimated arrival time of the VPM impulses at S1 had a median value of 5.97 ms. This estimate was obtained by adding the antidromic latency of each VPM neuron to the latency of the peripheral stimulus and was supported by similar values obtained from three VPM thalamocortical axons recorded near their termination site within S1. SINs of S1 were among the first cortical neurons to respond to the peripheral stimulus, responding to the air puff at a median latency of 6.6 ms (range 5.7-13.0 ms). The latency of SINs to the peripheral stimulus was strongly related to the latency to gross electrical stimulation of VPM (median value 1.52 ms, r2 = +0.44, P < 0.0001). Many SINs (23 of 34) showed significant shift-corrected CCGs with VPM neurons that were in precise topographic alignment. Most significant CCGs revealed a very brief increase in SIN spike probability (half-amplitude response of approximately 1 ms) that reached a peak value at intervals of 1.4-2.0 ms after the VPM spike.(ABSTRACT TRUNCATED AT 400 WORDS)

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