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A van Wieringen

Publications and source records attributed to A van Wieringen.

14 recordsLinked to original sources
PubMed1999

Natural vowel and consonant recognition by Laura cochlear implantees.

OBJECTIVE: This study was performed to examine whether spectral and temporal properties of speech sounds are transferred effectively by the Laura cochlear implant device, and to determine whether listeners with different levels of performance use the same type of information to understand speech. DESIGN: Twenty-five adult Laura cochlear implantees identified 12 repetitions of 10 vowels in /hVt/ utterances and 16 consonants placed in intervocalic /a/ context. The stimulus-response confusion matrices were analyzed in terms of relative information transmission scores (Miller & Nicely, 1955), and they were subjected to multidimensional INDSCAL analyses to examine whether a similar pattern of results would emerge when no prior assumptions were made about the division of categories. RESULTS: To examine perception for different levels of performance, the vowel and consonant confusion data were divided into three groups of subjects: the better, intermediate, and poorer performers. In general, the INDSCAL analyses confirmed the results obtained from the information transmission analyses. However, they also supplemented it with other perceptually relevant cues for cochlear implantees, as well as with the weightings over different perceptual dimensions for different types of performers. These analyses suggest that although all subjects use the same type of information, the better performers are more capable of using these different cues than poor performers.

Adolescent↗
PubMed1999

Gap detection in single- and multiple-channel stimuli by LAURA cochlear implantees.

Gap-detection thresholds were determined for different complex patterns of electrical stimulation in four postlingually deafened LAURA cochlear implantees, to examine the nature of within- and across-channel auditory processes in more detail. Gap detectability was examined as a function of stimulus complexity (one, two, or three channels), channel distance within and across multichannel pre- and post-gap markers, stimulus asymmetry, and pulse rate. All markers roved in duration from 200 to 500 ms to ensure that subjects were not using overall stimulus duration as a cue. Gap-detection thresholds for all subjects were short (< 5 ms) when the pre- and post-gap markers stimulated the same single or multiple channels, even when the distance between simultaneously stimulated channels was large (exp. 1). For some subjects, gap detectability was more difficult in the across-channel condition, when the pre- and post-gap markers each stimulated different channels, although performance improved substantially in most subjects after extensive training (exp. 2). Additional tests with random maskers also suggest that neural interaction only affects performance mildly, and that the magnitude of the gap-detection threshold probably depends more on the subject's cognitive (in)ability to attend to the temporal gap than on the temporal acuity of their auditory system. Other stimulus conditions showed a difference in performance related to the order of the markers: gap thresholds were longer when the pre-gap marker stimulated one channel and the post-gap marker stimulated two or more channels, than vice versa (exp. 3). In addition, gap thresholds of three of the subjects increased with decreasing pulse rate from 1250 to 400 pps, a finding which may be related to the rate of the speech processing strategies used by each individual implantee (exp. 4).

Acoustic Stimulation↗
PubMed1994

Frequency and duration discrimination of short first-formant speechlike transitions.

Frequency and duration discrimination thresholds of short rising and falling one-formant speechlike transitions without a steady state were determined by means of same/different paired comparison tasks in two experiments. When frequency extent is varied (experiment 1), just noticeable differences decrease with increasing transition duration. Expressed in Hz, thresholds are, on average, 70, 63, and 58 Hz for 20, 30, and 50 ms, respectively. However, when transition duration is varied at a constant frequency extent (experiment 2), difference limens increase with increasing duration and are, on average, 2.7, 4.5, and 4.9 ms for standard transitions of 20, 30, and 50 ms, respectively. The thresholds determined in the two experiments indicate that different psychoacoustical cues are used depending on whether final frequency (experiment 1) or transition duration (experiment 2) are varied. Both experiments were performed at two different frequency regions (between 200 and 700 Hz and between 500 and 1000 Hz), but the results did not differ per region. In addition, no significant differences were found between rising and falling transitions. Particular attention was paid to a methodological issue, viz., the extent to which sensitivity changes as a result of different proportions of catch trials. It was found that the listeners maintained the same response strategies throughout the tests, as their performance is similar, irrespective of the number of catch trials included in the testing sessions.

Adult↗
PubMed1990

Pilot study to determine the interaction of oxiracetam with antiepileptic drugs.

Oxiracetam, a nootropic drug, could be of potential use in the treatment of memory disturbances in patients with epilepsy who are using antiepileptic drugs. The half-life of oxiracetam appears to be influenced by the concomitant use of carbamazepine or valproic acid, necessitating more frequent administration of oxiracetam than is recommended for other conditions. No effect was observed on the serum concentrations of these antiepileptic drugs by oxiracetam. Long term concurrent use of oxiracetam and antiepileptic agents does not appear to be contraindicated.

Adult↗
PubMed1989

Comparison of the effects of lamotrigine and phenytoin on the EEG power spectrum and cortical and brainstem-evoked responses of normal human volunteers.

Phenytoin and lamotrigine (a new antiepileptic drug with an animal experimental profile resembling phenytoin) have closely similar effects on the quantitative pharmaco-electroencephalogram. These characteristics do not provide a basis for the functional classification of antiepileptic drugs nor for prediction of clinical efficacy, but they do give some insight into the probable secondary psychotropic effects which may arise with use of these drugs. Central conduction in cortical (visual) and brainstem (auditory) event-related potentials are not influenced by either drug, but peripheral nerve conduction is delayed with the use of phenytoin as reflected in increased latency wave I in the brainstem auditory-evoked response. The evidence suggests that in equivalent therapeutic dosage, lamotrigine may be less neurotoxic than phenytoin.

Adult↗
PubMed1986

Add-on therapy in epilepsy with calcium entry blockers.

In view of the known role of Ca2+ in the paroxysmal depolarization shifts of epileptic neurones, the possibility arises that certain Ca2+ entry blockers possess antiepileptic activity. The only drug of the class which readily passes the blood-brain barrier is flunarizine. This is effective in experimental models of epilepsy and produced significant seizure reduction in two therapeutic trials in therapy-resistant patients. It has few and mild side effects at therapeutic blood levels.

Adolescent↗
PubMedDate not supplied

Open dose-ranging trial of flunarizine as add-on therapy in epilepsy.

A double-blind placebo-controlled crossover trial of flunarizine as add-on treatment in therapy-resistant epilepsy offered significant evidence of efficacy, but the plasma levels of flunarizine were lower than anticipated, probably due to induction of liver enzymes by comedication. An open dose-ranging trial was therefore undertaken to investigate the relationships among dose, efficacy, side effects, and blood level. With basal medication held constant, flunarizine was added at 3-month intervals in increasing doses of 0, 10, 15, 20, and 25 mg daily, or until side effects occurred or marked seizure reduction was obtained. Forty-seven patients completed the trial; all were adults with therapy-resistant epilepsy who had at least 3 seizures per month. All had complex partial seizures, with additional types in 20. Sixteen patients showed a 50% and 24 a 25% reduction of seizure incidence on flunarizine; 6 and 7, respectively, showed a corresponding increase. The greatest seizure reduction, when observed, occurred generally at a daily dose of 15-20 mg. Side effects, chiefly drowsiness and weight gain, increased markedly between 15 and 20 mg daily. Flunarizine administration produced no change in serum levels of comedication, but flunarizine levels were lower in patients taking more than one other drug. Seizure reduction was obtained most consistently in patients with secondary generalized epilepsy or neurologic deficits. The findings confirm the antiepileptic action of flunarizine in humans and justify further trials.

Adolescent↗
PubMedDate not supplied

Acute effects of lamotrigine (BW430C) in persons with epilepsy.

Sixteen epileptic patients took single doses of lamotrigine, 120 mg or 240 mg. Six photosensitive patients showed reduction (with abolition in two) in photosensitivity after lamotrigine administration. Five subjects with frequent interictal spikes showed reduction in spike frequency over 24 h after lamotrigine administration. The half-life (t1/2) of lamotrigine in subjects taking sodium valproate was prolonged, whereas the t1/2 in subjects taking carbamazepine and/or phenytoin was reduced. The area under the curve of co-medication plasma levels was not affected by a single dose of lamotrigine. Five patients reported mild and generally transitory side effects; some of which represented exacerbation of preexisting complaints.

Adolescent↗
PubMedDate not supplied

Double-blind placebo-controlled, neuropsychological and neurophysiological investigations with oxiracetam (CGP 21690E) in memory-impaired patients with epilepsy.

A double-blind placebo-controlled between-patient study was carried out to assess the effects of oxiracetam (CGP 21690E) on memory function in patients with epilepsy. During a 12-week period, either oxiracetam (800 mg t.i.d.) or placebo was given to 30 patients. Twenty-four of the patients had a partial epilepsy. Most patients were on monotherapy carbamazepine. Effect of oxiracetam on memory and related cognitive functions were assessed, using a computerized neuropsychological testing method, while concomitant electrophysiological changes were investigated with routine EEG registration, power spectrum analysis and auditory evoked event-related potentials (P300). Subjective evaluation of well-being was quantified with a mood rating scale. The results did not show any meaningful changes in memory function. This finding is in line with the subjective patient reports and the P300 measures.

Adolescent↗
PubMedDate not supplied

Speech intelligibility in noisy environments with one- and two-microphone hearing aids.

In this study speech intelligibility in background noise was evaluated with 10 binaural hearing-aid users for hearing aids with one omnidirectional microphone and a hearing aid with a two-microphone configuration (enabling an omnidirectional as well as a directional mode). Signal-to-noise ratio (SNR) measurements were carried out for three different types of background noise (speech-weighted noise, traffic noise and restaurant noise) and two kinds of speech material (bisyllabic word lists and sentences). The average SNR improvement of the directional microphone configuration relative to the omnidirectional one was 3.4 dB for noise presented from 90 degrees azimuth. This improvement was independent of the specific type of noise and speech material, indicating that one speech-in-noise condition may yield enough relevant information in the evaluation of directional microphones and speech understanding in noise.

Adolescent↗