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Biomedical subjects

M Bénita

Publications and source records attributed to M Bénita.

12 recordsLinked to original sources
PubMed1981

Control of reaction time performance involves the striatum.

Cats were tested for the effect of unilateral cooling of the centre median nucleus of the thalamus (CM) or of the caudate nucleus (Cd) as they performed a simple reaction time schedule. Shortening of reaction time occurred during CM cooling. Lengthening of the reaction time was observed during Cd cooling. Moreover, the Cd cooling was followed after a variable delay of a few minutes by a slowing down of the trial rate, and even by the arrest of performance for the lowest cooling temperature. The subject restarted at will after an arrest period, without motivational or motor disturbances, except for a short period of rotatory behaviour. The arrest period duration was about equal to the arrest period latency. Human subjects suffering from Parkinson's disease were tested with the same reaction time schedule. They showed lengthened reaction times and difficulty to perform reliably more than a ten of trials.

Animals↗
PubMed1979

Activity of ventrolateral thalamic neurons in relation to a simple reaction time task in the cat.

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.

Animals↗
PubMed1979

Effects of ventrolateral thalamic nucleus cooling on initiation of forelimb ballistic flexion movements by conditioned cats.

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 decrees C to -8 degrees 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 degrees C and an increase of the reaction times for a cooling at -10 degrees 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.

Animals↗
PubMed1978

Scheduled-training of cats to a simple reaction time performance.

Cats were trained to release a lever at the onset of a sound, using a simple reaction time paradigm with different foreperiods. The training of the subjects was controlled by a PDP 8/L computer with a training schedule that avoided the problems of manual shaping except for the preliminary step, the lever press. This schedule successfully trained the cats in about 6 daily sessions up to the reaction time paradigm with a 3 sec criterion. In contrast, a programme designed to reduce the criterion value so as to induce the subjects to perform shorter latency movements failed because the cats learned to control it through an escape procedure.

Animals↗