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Biomedical subjects

C H Brunia

Publications and source records attributed to C H Brunia.

At least 73 records · Page 4Linked to original sources
PubMed1981

Opposite hemisphere differences in movement related potentials preceding foot and finger flexions.

Nine right-handed subjects performed an experiment in which the recording of the readiness potential (RP) and of the contingent negative variation (CNV) was combined. A microswitch was pressed by a voluntary foot or finger movement. 4 sec later a visual stimulus was presented, to which the subject had to respond as quickly as possible by making the same movement. Four electrode positions were used: C3, C4, C'3 and C'4, the latter two in between Cz and C3 or C4, respectively. The RPs showed larger amplitudes over the hemisphere, contralateral to the finger movement. Moreover, although not significant, RPs showed larger amplitudes over the hemisphere, ipsilateral to the foot movement. Late CNV waves were larger at C3 prior to a finger response and at C'4 prior to a foot response. This result is an argument for the hypothesis of a common underlying mechanism of RP and CNV late waves. Moreover, it suggests that motor preparation is a selective process which is related to the activation of a specific area in the motor cortex.

Adult↗
PubMed1980

Monosynaptic reflexes during generalized spike and wave activity, provoked by intermittent photic stimulation.

Achilles tendon (T) and Hoffmann (H) reflexes were evoked during spike and wave activity (SWA) in 6 patients with generalized epilepsy, selected on the basis of their photosensitivity. SWA was provoked by intermittent photic stimulation (IPS). It was demonstrated that monosynaptic reflex amplitudes were larger during SWA than at rest. Although IPS caused by itself a slight increase in amplitudes, there was an obvious difference from the larger increase during SWA. T reflexes showed a more explicit increment than H reflexes. The activity changes in the spinal motor circuits were nearly always present in the absence of any clinical manifestation of motor activity. The possible mechanisms are discussed.

Adolescent↗
PubMed1979

Effects of stimulus frequency on the blink reflex during rest and a task.

Blink reflexes were studied in 84 healthy subjects, applying 4 different stimulation frequencies. The experiments were subdivided into 3 periods: rest, binary choice task and final rest period. Independent of the applied stimulation frequency, an increment of R1 during the task was found, and it was concluded that R1 amplitude reflects the state of arousal of the subject. Within each of the 3 periods, R1 amplitudes decreased independently of the applied frequency, while R2 amplitudes decreased dependent on the applied frequency, i.e. at lower frequencies a smaller decrement in time could be observed. It was concluded that R2 habituated at frequencies lower than those so far reported.

Analog-Digital Conversion↗
PubMed1979

Effect of propanolol on monosynaptic reflex activity during a task.

20 normal healthy subjects in a double-blind crossover experiment were given a table of either 40 mg propranolol or placebo half an hour before the beginning of the experiment. At rest and during the performance of a task, hert rate, Achilles tendon (T) and Hoffmann (H) reflexes were recorded. No increase in heart rate occurred during the task in the propranolol session. The increase of T-reflex amplitude, a common finding during the task under consideration, was larger in the propranolol session. No difference with H reflexes was found. It is concluded that the increase of T-reflex amplitudes during the task is caused only by fusimotor and not by sympathetic activity. It is speculated that if the sympathetic system plays a role at all, the effect on the T reflex is depressive rather than facilitating.

Adolescent↗
PubMed1978

MSH/ACTH4-10 and task-induced increase in tendon reflexes and heart rate.

Earlier studies revealed that during a binary choice reaction task an increase of tendon reflex amplitudes and heart rate can be found, together with a suppression of heart rate variability. The results were interpreted as a task-induced increase in generalized arousal. In this study two experiments, consisting of a rest period and a binary choice reaction task, were done. In Experiment 1, twenty subjects, in a cross-over design, received 15 mg MSH/ACTH4-10 or a placebo. Only reflexes were recorded. In experiment 2, three groups of 9 subjects received either 30 or 15 mg MSH/ACTH4-10 or a placebo. Reflexes, heart rate and heart rate variability were recorded. Rest-task differences of reflexes and heart rate were enhanced by the drug. We hypothesized that MSH/ACTH4-10 intensified the arousal effect of the task.

Adolescent↗
PubMed1977

Blink reflexes and the state of arousal.

Blink reflexes were studied in 40 subjects at rest and during the performance of a task. The early reflex (R1) showed an increase of amplitude of action potential during the task, the late reflex (R2) did not. The latency of R1 did not change within the 45 minutes test period; R2 showed an increase of latency during task. R1 showed a systematic decrease in amplitude within rest and task periods, presumably because of habituation. R2 amplitudes decreased throughout the whole experiment, independent of task or rest.

Action Potentials↗
PubMedDate not supplied

The modulation of somatosensory evoked potentials during the foreperiod of a forewarned reaction time task.

During the foreperiod of a forewarned reaction time (RT) task reflexes in the executing limb increase to a lesser extent than those in the contralateral limb. This is possibly due to input modulation. The present study investigates the possibility of cutaneous sensory modulation during motor preparation by studying the amplitudes of somatosensory evoked potentials (SEPs). Eighteen subjects performed a forewarned RT task with the same fingers as the ones which were electrically stimulated. SEPs evoked during the 4 sec preparatory period were compared to those evoked during movement execution and during the resting period after the motor response respectively. During response execution most SEP components showed smaller amplitudes, i.e., they were gated, which agrees with other studies. In the first part of the foreperiod no SEP modulation was observed. Towards the end of the foreperiod, 500 msec before the response stimulus (RS), the amplitude of the contralateral parietal N70-P100 was significantly decreased, while the P45-N70 showed a similar tendency. However, at the same time the P100-N140 was increased in amplitude. The decrease of the intermediate latency components towards the end of the foreperiod is discussed in terms of gating, while the increase in the long latency component is discussed with respect to a decrease in RT on trials where the fingers were stimulated just before the RS, pointing to the role of attentional mechanisms.

Adult↗
PubMedDate not supplied

CNV and EMG preceding a plantar flexion of the foot.

In 25 subjects CNV and EMG were recorded during a reaction time experiment with a fixed 4 sec foreperiod. The response was plantar flexion of the right foot. EEGs were recorded with four electrodes from the central area, two over each hemisphere. CNV amplitudes were larger over the ipsilateral than over the contralateral hemisphere. Amplitudes were smaller in the more lateral derivations. The late component of the CNV showed larger amplitudes when preceding relatively fast responses. EMG activity was recorded from the calf muscles of both legs. In the left leg it was not different during the intertrial interval and the foreperiod. A small but systematic increase in EMG activity was found during the foreperiod in the right leg. The increase was larger preceding fast responses, parallel to the amplitude changes in CNV late waves.

Adolescent↗