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C H Brunia

Publications and source records attributed to C H Brunia.

At least 19 recordsLinked to original sources
PubMed1991

Event-related potentials to different feedback stimuli.

Event-related potentials (ERPs) were recorded in a time estimation task under different feedback conditions, in which the informative value of the feedback signals (true versus false) was manipulated. A control condition was added in which no signal was presented. Fifteen subjects pressed a button 3 seconds after presentation of a warning signal. Two seconds after the response, a visual feedback signal was presented, indicating whether the preceding interval was estimated correctly. Two different slow waves were observed: the response was preceded by a readiness potential and the feedback stimulus was preceded by a negative slow wave called the stimulus-preceding negativity. The readiness potential was not influenced by the different feedback conditions. The stimulus-preceding negativity was larger in the true feedback condition compared to the false feedback and no feedback conditions. The P300 to the feedback signal was also larger following a true as compared to a false feedback signal. The conclusion is that the stimulus-preceding negativity is an anticipatory component contingent upon the presentation of an informative feedback signal.

Adult↗
PubMed1991

The effect of an acoustic warning stimulus upon the electrically elicited blink reflex in humans.

In a warned Go/No-Go reaction time experiment blink reflexes were elicited electrically immediately before, at, and shortly after the onset of a low intensity acoustic warning stimulus. This provided the opportunity to study the mutual effects of two stimuli of different modalities arriving at the facial nucleus. The warning stimulus was followed after 3 s by an acoustic response stimulus. Sixteen subjects participated in the experiment. They were informed by the response stimulus if a response (a voluntary blink of the right eye) was required. R1 magnitude was increased from 10 ms to 100 ms after warning stimulus onset, with a pronounced peak at 50 ms. The bilateral late component R2 was enhanced when the reflex eliciting stimulus preceded the warning stimulus. Between 20 ms and 30 ms after warning stimulus onset, R2 returned to control level, whereas an eliciting stimulus presented 40 ms or later after warning stimulus onset produced a pronounced inhibition. R2 latency was facilitated immediately after warning stimulus onset. It was concluded that the mutual effects of stimuli of different modalities can be interpreted only if the moment of arrival at the motor nucleus is taken into consideration.

Adult↗
PubMed1990

Contingent Negative Variation in migraine.

The Contingent Negative Variation (CNV) is an event-related slow potential. It was recorded in healthy volunteers (n = 8) and in patients suffering from migraine without (n = 12) or with (n = 5) aura, during one (CNV1) and three second (CNV3) foreperiods in a forewarned reaction time task. CNV1 was recorded at the vertex while CNV3 was recorded at multiple electrode sites to assess topographical differences. Seven out of twelve migraine patients without aura had increased CNV1 amplitudes. CNV3 amplitudes were increased as well, but only at electrode positions C3 and C4 and not at Fz. CNV3, which allows for analysis of both an early and a late CNV component, could improve the discrimination of migraine without aura beyond that of CNV1. In migraine with aura all CNV parameters were at control levels, confirming previous results. The data obtained are discussed in terms of arousal, activation and stress and the "biobehavioral model of migraine" (Welch, 1986).

Adult↗
PubMed1989

Correction of ocular artifacts in EEGs using an autoregressive model to describe the EEG; a pilot study.

The basic idea in eye movement (EM) artifact corrections is that the actual recording is the summation of brain potentials (true EEG) and artifact. Often a regression analysis is performed, using simultaneous EEG and EOG data, to find the parameters describing the relationship between artifact and EOG derivations (EOGs). Our method uses a maximum likelihood parameter estimation and considers data from preceding sample moments as well, since there may be a delay in the artifact transferring over the scalp. For the error term (true EEG) an autoregressive function is used. Results from estimations on data from one volunteer indicate that a delay need not be considered and that 3 autoregressive parameters are sufficient. For F3 4 EOGs give only somewhat better results than 2 EOGs. For C3 and C4 2 EOGs are sufficient. For practical reasons for each of these 3 EEG recordings, 2 EOGs were used to perform corrections. Corrections were performed using either the parameters estimated for EMs and blinks together, or the parameters estimated for EMs only (used for EMs), or the parameters estimated for blinks only (used for blinks). For EMs the differences between these corrections are very small. For blinks the differences are much larger. Parameters estimated for one trial may be used to correct other trials, recorded within a period of about 15 min preceding or following that trial.

Blinking↗
PubMed1988

Distribution of slow brain potentials related to motor preparation and stimulus anticipation in a time estimation task.

Subjects had to press a button at regular intervals of 20 sec. Two seconds after each button press a stimulus was presented indicating the length of the past interval. EEG was analysed from 2500 msec preceding the button press until the presentation of the stimulus. Preceding the button press a readiness potential (RP) was recorded with amplitudes that were larger over the hemisphere contralateral to the movement side. Preceding the stimulus negative waves were recorded which were larger over the right hemisphere, irrespective of the movement side. In a warned reaction time experiment, the CNV late wave represents both motor preparation and stimulus anticipation. In the present study motor preparation and stimulus anticipation are no longer confounded factors. Thus, it is shown that stimulus anticipation is indeed reflected by negative activity, as is motor preparation. The potential distribution of the RP, however, is different from the stimulus-preceding negativity (SPN), a pointing to a different electrophysiological source. The potential distribution of the SPN has been investigated and a right hemisphere preponderance of the SPN has been found.

Adolescent↗
PubMed1988

Movement and stimulus preceding negativity.

After a short description of the different premovement potentials it is suggested that readiness potentials (RPs) recorded over different cortical motor areas reflect different functions. Then it is proposed that the late wave of the contingent negative variation (CNV) is a composite of a RP and a stimulus preceding negativity (SPN). Arguments for the existence of a non-motoric SPN are given, based upon our recent experiments. Next, it is suggested that a SPN is found preceding at least three different kinds of stimuli. Finally, it is stated that motor preparation and stimulus anticipation are different processes, reflected in a different distribution of the accompanying Slow Waves and an all or none accompanying change in reflex amplitudes.

Animals↗
PubMed1986

Motor preparation and the Achilles tendon reflex: the role of background muscle tension.

The effects of instructed tension or relaxation of the soleus muscles on the amplitude of the Achilles tendon reflex were investigated. Reflexes were evoked during the foreperiod of a warned reaction time experiment with a plantar flexion of the right foot serving as the response, and during isometric contractions of the right soleus muscle at different low levels of tension. The tension levels were related to the subject's maximal voluntary contraction force. The results were comparable in the two tasks. When background muscle tension was present in the right leg the reflexes in that leg were depressed, whereas in the contralateral leg reflexes were increased. This difference in amplitude was roughly proportional to the amount of tension and independent of whether the antagonist muscle was also activated during the contraction. It was argued that the differential reflex effect found in the two soleus muscles during motor preparation need not be a reflection of a selective neural inhibition. It could also be explained by a reduced effectiveness of the tendon tap in stretching the muscle, due to stiffening of the muscle during contraction. It was concluded that during motor preparation, only reflex changes recorded in the absence of muscle tension can be considered reflections of subliminal changes in spinal reactivity.

Achilles Tendon↗
PubMed1985

Movement related slow potentials. II. A contrast between finger and foot movements in left-handed subjects.

Finger and foot movement related potentials (MRPs) were recorded over the frontal, central and parietal areas of both hemispheres in 20 left-handed subjects. A unilateral flexion of the index finger and a plantar flexion of the foot were studied on either side. MRPs were larger preceding foot movements than preceding finger movements, their onset being earlier also. Prior to a finger flexion amplitudes were larger over the hemisphere contralateral to the movement than over the ipsilateral hemisphere. Preceding a foot movement, however, amplitudes were larger over the ipsilateral hemisphere. These results indicate differently localized sources of the MRPs in the two kinds of movement, in accordance with data obtained in right-handed subjects. No indication of a hemisphere effect, possibly related to motor dominance, was found in left-handers. This is in contrast to a slight hemisphere effect found with foot movements in right-handed subjects in the former study.

Adolescent↗
PubMed1985

Anticipatory response-relevant muscle activity, CNV amplitude and simple reaction time.

The present experiment was aimed at whether subjects, performing a forewarned simple reaction time (RT) task, do voluntarily tense agonist and antagonist muscles during the foreperiod; if so, would such muscle tension co-vary with CNV amplitude or RT? Although excessive eye movements caused 30% of the subjects to be removed from the analysis, it was still possible after the experiment to differentiate between subjects who gradually tensed their agonist during the foreperiod and subjects who did not. The former group showed higher CNV early and late wave amplitudes as compared with the latter group. A similar effect was found on the N1 amplitude of the potential evoked by the warning stimulus. The increased EMG in the agonist muscle at the end of the foreperiod was not concomitant with faster RTs. In addition, fast RTs were preceded by higher CNV late wave amplitudes at pre- and postcentral electrode positions. The observed relationships between CNV, EMG, and RT were discussed in terms of specific and general motor preparation.

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↗