PubMed Health⌕ Search

Biomedical subjects

A J Boelhouwer

Publications and source records attributed to A J Boelhouwer.

8 recordsLinked to original sources
PubMed1998

Optimal EMG signal bandwidth and interelectrode distance for the recording of acoustic, electrocutaneous, and photic blink reflexes.

The bandwidth for the recording of the orbicularis oculi blink reflex electromyogram (EMG) response is optimal when low-frequency artifacts, such as motion artifacts and cross-talk from other muscles, are maximally suppressed, whereas true EMG signal power is maximally retained. The optimal bandwidth was investigated for acoustic, electrocutaneous, and photic blink reflexes. Reflexes were recorded with varying bandwidth and interelectrode distances of 12 and 36 mm. Power spectra of the EMG signals were calculated and compared with a theoretical spectrum of the uncontaminated EMG signal. For both electrode distances, the optimal bandwidth was on the average 28-500 Hz for acoustic and electrocutaneous blink reflexes and 12-500 Hz for photic blinks. Using photic stimuli, however, a high-pass filter frequency larger than 12 Hz (probably at least 30 Hz) in combination with occlusion of the eye will be necessary to avoid influences of retinal potentials. Given the optimal bandwidth, a larger electrode spacing may be expected to moderately improve the detectability of small blinks in all stimulus conditions.

Acoustic Stimulation↗
PubMed1996

The effect of acoustic pulse intensity upon the electrically elicited blink reflex at positive and negative stimulus onset asynchronies.

The present study examined the effects of acoustic pulse intensity and stimulus onset asynchrony (SOA) on the electrically elicited startle reflex response. Subjects were presented with 165 startle eliciting stimuli: 15 control trials with no acoustic pulse, and 5 trials at each pulse intensity (50, 70, and 90 dB) for each SOA (-80, 60, -40, -20, 0, 20, 40, 60, 80, and 100 ms). The results demonstrated R2 magnitude facilitation at negative, simultaneous, and short positive SOAs. R2 facilitation was greatest in the 90 dB condition and least in the 50 dB condition. R1 facilitation at short positive SOAs was greater for more intense acoustic pulses. These data support the notion that R2 facilitation at near-zero SOAs may be the result of combination of pulse induced potentiation of the electrically elicited startle response and temporal summation of the effects of electrical and acoustic stimuli at the facial motor nucleus.

Acoustic Stimulation↗
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↗
PubMed1983

Changes of human blink reflex magnitude during a three second fixed foreperiod.

Blink reflexes were evoked at distinct times during a 3 sec foreperiod (FP) between a warning stimulus (WS) and a reaction signal (RS). Sixteen well-trained, right-handed subjects participated in the experiment. Following RS, they reacted instantaneously with a blink of the right eye. In the electrically evoked blink reflex, an early ipsilateral component (R1) with a latency of +/- 10 msec and a late bilateral component (R2) with a latency of +/- 25-40 msec could be distinguished. The peak-to-peak amplitude of R1 and the integral of R2 were computed. In the beginning of FP, R1 was enlarged as compared to control values. Toward the end of FP, a continuous rise of R1 amplitudes was seen. This increment was most pronounced in the muscle involved in the reaction following RS. R2 was inhibited immediately after WS, while no significant inhibition could be seen near the end of FP. The conclusion is that the facilitation of R1 and the disinhibition of R2 towards the end of FP reflect the preparation on the reaction after RS. The extra increment of R1 might be due to a selective extra preparation of the motoneurons of the involved muscle, although an effect of motor dominance cannot be excluded.

Adult↗
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↗
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

Blink reflexes and preparation.

Blink reflexes were evoked during a foreperiod of 3 sec between a warning signal (WS) and a reaction signal (RS). In a between group design, two possible reactions following RS were investigated: 20 subjects always reacted with both hands, another group of 20 subjects always reacted with a voluntary blink. A manual response was assumed not to involve the circuit of the blink reflex, whereas a blink as a response was thought to be (at least partly) realized via the same circuit as the blink reflex. Both groups showed a strong increase of the early component (R1) of the blink reflex during the first 300 msec after WS, while the late polysynaptic component (R2) showed a strong inhibition during the same period. R1 did not decrease as a function of presentation order when the demanded reaction was a voluntary blink. No other inhibition or excitation related to the type of reaction after RS was observed during the foreperiod before RS.

Adolescent↗