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  • 1
    ISSN: 1432-1106
    Keywords: Key words Pedunculopontine tegmental nucleus ; Reinforcement ; Signal processing ; Microinjection ; Reaction time ; Movement
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The effects of reversible pharmacological manipulation of the neuronal activity in the pedunculopontine tegmental nucleus (PPTg) on the performance of a conditioned movement was studied in two freely moving cats. The microinjections were given in regions where, in the same subjects, we had previously identified neurons with context-dependent early activity after a trigger stimulus and with reinforcement-related activity. The subjects were conditioned to perform a forelimb-flexion movement controlled by a simple reaction-time task. In addition, one subject was trained to execute the same flexion movement, but delayed after the trigger stimulus. Food pellets were used as the reinforcer. Lidocaine injections (1 µl of 2% solution, injected over a 6-min period) induced a transient arrest of performance within minutes. The cessation of performance could be preceded by behavioral signs such as meowing, attempt to escape from the experimental booth, licking, or stereotyped posture. No rotational behavior could be observed. The effects of lidocaine could be mimicked in one subject by an extinction procedure. Muscimol injections (two injections of 0.2 µg in 1 µl, tested in one subject) also induced arrest of performance, but the return to pre-injection level of performance could not be obtained within the time of the test session. The quantitative analysis of reaction times and of inter-trial intervals showed that altering PPTg activity affected inter-trial intervals, but only slightly affected the reaction times. It is speculated that the PPTg is involved in the reinforcement process related to selecting the appropriate motor program.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1106
    Keywords: Key words Pedunculopontine tegmental nucleus ; Reinforcement ; Signal processing ; Single-unit activity ; Reaction time ; Delayed movement
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The activity of the pedunculopontine tegmental nucleus (PPTg) neurons was recorded in three unrestrained cats operantly conditioned to perform a lever-release movement. The movement had to be initiated either rapidly after a (click) stimulus in a simple reaction-time paradigm or had to be delayed after the same stimulus in trials identified by a tone cue. Successful trials were rewarded by a food pellet. A total of 107 neurons were recorded with microelectrodes. Brief spike neurons (mean duration: 0.7 ms) and broad spike neurons (mean duration: 2 ms) presumed to be cholinergic were detected. Of the 73 neurons localized in the PPTg area, 53 had brief spikes and 20 broad spikes. Changes in activity most commonly occurred very early after the stimulus or during the reinforcement process. Most neurons with brief spikes exhibited very early excitation after the stimulus and reinforcement-related activity. These neurons had a mean activity of 23.7 impulses/s in the period preceding the stimulus. The onset of activation after the stimulus had a latency of 8.6±6.9 ms (mean±SD), with a range of 4–35 ms. In trials where the movement had to be delayed after the stimulus, the early activation disappeared or was considerably reduced, showing that it was context-dependent. A small proportion of neurons with brief spikes initially decreased activity after the stimulus, but with a latency 〉9 ms. All the neurons with broad spikes, except one, had reinforcement-related activity. Half of them showed exclusively reinforcement-related activity, the other half also early activation after the stimulus. These neurons were about half as active in the period preceding the stimulus occurrence than the neurons with brief spikes. The early context-dependent activation is discussed in relation to the excitatory projection of PPTg neurons on the subthalamic nucleus. The reinforcement-related activity, preferentially evidenced in broad spike neurons presumed to be cholinergic, is speculated to be associated with cholinergic projection of PPTg neurons to the dopaminergic neurons of the substantia nigra. Finally, the role of PPTg in the ongoing control of motor performance and reinforcement processes is discussed in relation to the basal ganglia circuitry.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-1106
    Keywords: Cooling ; Ventrolateral thalamic nucleus ; Pyramidal system ; Reaction time ; Ballistic movement ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Five cats were trained to perform a forelimb ballistic flexion on a reaction time paradigm including an upper limit of about 400 ms for reinforcement (food pellets). They were implanted with a cyrogenic probe thermically insulated, except at the tip, by a vacuum jacket (outer diameter, 1.1 mm). Four cats had the probe inserted into the ventrolateral thalamic nucleus (VL), contralateral to the moving limb. During cooling they showed increased reaction times, which remained constant throughout daily sessions performed during many weeks, independent of the foreperiod but varying from 25 to 100 ms according to the subject. The temperatures used to upset the reaction times varied from +10 ° C to −8 ° C, depending on the localisation of the probe and on the insulation of the silver tip used to prevent nervous tissue reaction, but for each subject the reaction times always increased when the temperature was lowered. The fifth cat, with a probe inserted between VL and the Centre Median, showed a decrease of reaction times on cooling to 0 ° C and an increase of the reaction times for a cooling at −10 ° C. For one of the four cats with a probe properly inserted into the VL, strain-gauges were stuck on the lever to measure the latency of the decrease of the pressure exerted by the subject when the subject initiated the forelimb flexion in response to the CS. Reaction times and latencies of pressure changes were closely correlated with the movement onset, and they were equally delayed during cooling. This result demonstrates that it is not by slowing down movement velocity that reaction times are upset during VL cooling but by delaying the movement onset.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 52 (1983), S. 210-218 
    ISSN: 1432-1106
    Keywords: Red nucleus ; Motor initiation ; Reaction time ; Single unit recording
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Unit recordings were made in the posterior red nucleus of 4 freely moving cats, performing a conditioned forelimb flexion in response to a sound, in a simple reaction time (RT) paradigm. More than 50% of the recorded neurons (154) were found to be task-related, with marked changes of firing (mostly increases) time-locked with the go-signal (mean latency: 40.8 ms ± 12 ms SD) and frequency-correlated with the duration of the RT. These RT-correlated changes of firing disappeared or were markedly decreased when the movement was not triggered. Most of the task-related neurons also displayed late changes of firing during the force change, time-locked with the movement. Furthermore, a clear relation was observed between the rubral firing before and after the go-signal and the sensorimotor field of the recorded neuron: the neurons preferentially related to limb or trunk movements discharged with the highest frequency throughout the conditioned sequence and exhibited the best RT-correlated increases of firing during the movement initiation. In contrast, rubral neurons apparently related to head-movements generally discharged with low frequency and commonly exhibited decreases of firing in the initiation period. The changes of rubral firing prior to the motor activity, correlated to the RTs, suggest a command function for the RN, in the triggering of the conditioned motor response.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 12 (1971), S. 204-222 
    ISSN: 1432-1106
    Keywords: Centrum Medianum ; Striatum ; Pallidum ; Associative cortex ; Cooling ; Pain
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary 1. Evoked potentials were recorded in cats to study the distribution of axons leaving the Centrum Medianum of thalamus (CM). 2. Non-repetitive CM stimulation elicits surface-positive potentials onto the associative cortex: anterior sigmoïd gyrus, anterior marginal gyrus and suprasylvian gyrus (minimal latencies, 2, 4, 6 ms). The stimulation of these cortical foci by electrodes in the grey matter does not evoke in the CM any asynaptic response. It is concluded that the cortical response is not a sufficient indication of a cortical projection of the CM. 3. Associative cortical responses evoked by somatic stimulation are not affected either by electrocoagulation of CM or by cooling the CM with a cryogenic probe insulated except at the tip. Hence the CM does not seem to contribute to relay somatic activation from the periphery to the ipsilateral cortex. 4. Asynaptic responses (0.2–0.8 ms latency) and corresponding postsynaptic responses (0.5–1.5 ms latency) are recorded in the internal capsule, dorsal parts of putamen and globus pallidus, and in the entopedoncular nucleus. 5. Long latency waves are also recorded in these regions, in the amygdaloïd complex (2–9 ms latency) and in the caudate nucleus (minimal latency, 12 ms). Their distribution and their latencies are not related to those of the asynaptic responses. 6. The hypothesis that the CM plays a role in pain is discussed on the basis of hodological data.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 36 (1979), S. 285-300 
    ISSN: 1432-1106
    Keywords: VL nucleus ; Single units ; Reaction time ; Movement initiation ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Unrestrained cats performed ballistic forelimb flexion movements triggered by an auditory stimulus (CS) on a simple reaction time (RT) paradigm. During the variable foreperiod the subject was required to hold down a lever and to release it on presentation of the CS. The RTs ranged from 200 to 300 ms. The activity of single neurons of the ventrolateral nucleus of the thalamus (VL) was recorded bilaterally. More than 40% of the 166 units recorded in the VL contralateral to the performing limb presented, after the CS, changes of activity with a latency less than 100 ms and were classified into three types: (1) Twenty-five units had a short latency transient increase of activity 10 to 30 ms after the CS, followed by a longer increase or decrease in activity. Short latency increase as well as subsequent increase of the firing rate were not correlated to the RTs. (2) Twenty-nine units showed a 40–60 ms latency increase of activity which lasted long enough to continue during the forelimb movement. These units displayed a correlation between the RTs and the mean firing rate measured in the 40–100 ms period after the CS. The more the cells were activated, the shorter the RTs. (3) Fifteen units presented a reciprocal pattern of discharge with respect to the type (2) units. The firing rate decreased with latencies ranging from 20 to 90 ms after the CS. Only 14,5% of the 96 units recorded in the VL ipsilateral to the performing limb presented changes of activity starting in the 100 ms period following the CS. Background firing levels as well as phasic activity were rather low compared to those observed contralaterally. Sixteen units showed burst activity while the cat was performing but burst pattern was not time-related to the task. In an unconditioned animal, a very low level of activity and an absence of modulations were observed in both VLs.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 48 (1982), S. 315-322 
    ISSN: 1432-1106
    Keywords: Ventrolateral thalamic nucleus ; Variability ; Stationarity ; Motor program ; Information processing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The variability and stationarity of single unit activity and reaction times in a simple reaction time task were investigated by means of unit recordings from the ventrolateral thalamic nucleus in the cat. The study was carried out on eight neurons recorded over many trials and displaying an increase in activity correlated with the performed reaction time. The stationarity of the correlation appeared to be better than that of the unit activity or reaction time taken alone. In this stationary process the neuronal variability is considerable, and the investigator has to use time averages over many trials to be able to extract information from the single unit data. Since the nervous system does not require repeated presentations of a stimulus to trigger a movement, it must be using parallel processing of information through ensemble averages. A simulation of an ensemble average based upon the data from these eight neurons showed that such a process can be efficient. An evaluation of the number of neurons required to obtain a quasi deterministic neuronal command of the reaction time value, gave the speculative figure of 70. This figure could represent the dimension of the set of neurons with the same characteristics involved in the motor command.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 0375-9474
    Keywords: Nuclear Reaction
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Nuclear Physics, Section A 128 (1969), S. 209-218 
    ISSN: 0375-9474
    Keywords: Nuclear reactions
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 0375-9474
    Keywords: Nuclear reactions
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
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