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Biomedical subjects

P van den Broek

Publications and source records attributed to P van den Broek.

At least 19 recordsLinked to original sources
PubMed2005

Discrimination of speech sound contrasts determined with behavioral tests and event-related potentials in cochlear implant recipients.

Cortical potentials evoked with speech stimuli were investigated in ten experienced cochlear implant (CI, type Nucleus 24M) users using three different speech-coding strategies and two different speech contrasts, one vowel (/i/-/a/) and one consonant (/ba/-/da/) contrast. On average, results showed that, compared to subjects with normal hearing, P300 amplitudes were smaller; however, most latencies were within the normal range. Next, individual P300 measures in response to the two speech contrasts were compared to behavioral discrimination scores. Significant within-subject differences in P300 amplitudes and latencies were found for the three speech coding strategies. These differences were in agreement with the behavioral, strategy-dependent discrimination of the speech contrasts.

Acoustic Stimulation↗
PubMed2001

Aflatoxin genes and the aflatoxigenic potential of Koji moulds.

Sixty-four Aspergillus isolates, 54 of which originated from food fermentations, and 18 Aspergillus reference strains were identified and screened for the presence of aflatoxin genes aflR and omt-1. Among the Koji moulds, not only A. oryzae but also A. flavus strains were found. Furthermore, 27% of A. oryzae and 93% of A. flavus strains lacked either aflR or both aflR- and omt-1. A selection of 29 strains was also checked for the presence of pksA and nor-1. This revealed large deletions in the aflatoxin gene cluster of some strains. The hybridisation patterns also suggested a polarity in the deletion events, originating in the vicinity of pksA and extending towards omt-1. Other strains exhibited BamHI restriction fragment length polymorphisms (RFLPs) for either aflR or for aflR and omt-1. All aflR and/or omt-1 deletion strains turned out to be unable to produce aflatoxin. The RFLP-carrying strains either produced only traces of aflatoxin or none at all. In 73% of the A. oryzae strains, no apparent deletions were detected with the aflR and omt-1 probes. Nevertheless, after incubation in aflatoxin-inducing media, no aflatoxin B1 production could be detected in those A. oryzae strains.

Aflatoxins↗
PubMed2001

Generalizability of trial results based on randomized versus nonrandomized allocation of OME infants to ventilation tubes or watchful waiting.

The objective was to study the generalizability of trial results by comparing randomized patients to eligible but nonrandomized patients who received the same management. Implementation of trial results is only justifiable when the results can be generalized to the total domain population. The design was a multicentre randomized controlled trial on the effect of early screening and treatment with ventilation tubes on infants with otitis media with effusion. Randomized (n = 187) and nonrandomized eligible patients (n = 133) were followed up. The study population comprised children who were detected by auditory screening at the age of 9-12 months and who were subsequently diagnosed with persistent bilateral otitis media with effusion for 4-6 months. A significant difference was found in the distribution of some prognostic factors: more randomized children had older siblings, did not attend day care and had mothers with a lower educational level than the nonrandomized children. These factors, however, did not modify the outcome. No differences were found in mean hearing levels between the randomized and nonrandomized children: in both the randomized and nonrandomized children ventilation tubes improved the hearing level, especially after 6 months. However, in the long term (12 months), the hearing levels were equal again. The results of the randomized and nonrandomized patients were comparable. The results of this trial appear to be generalizable to the total domain population. The procedure of following up both randomized and nonrandomized patients is recommended when there is concern about selective participation and reduced generalizability.

Acoustic Impedance Tests↗
PubMed2001

Speech-evoked cortical potentials and speech recognition in cochlear implant users.

Processing in the auditory cortex may play a role in the unexplained variability in cochlear implant benefit. P300 and N1/P2 were elicited in post-lingually deaf cochlear implant users wearing a Nucleus multichannel cochlear implant. Four sound contrasts were presented (500-1,000 Hz, /ba/-/da/, /ba/-/pa/ and /i/-/a/). N1 and P2 were present in all subjects for all conditions. Prolonged N1, P2 and P300 latencies were found in the cochlear implant group compared to a control group of subjects with normal hearing. Cochlear implant users show smaller amplitudes of N1 for all the speech signals as well as smaller amplitudes of P2 for the consonants compared to the controls. P300 results of the cochlear implant users were compared to behavioural results of speech recognition testing. A relation was found between P300 amplitude and magnitude for the 500-1,000 Hz and /i/-/a/ contrasts and behavioural speech recognition in cochlear implant users. The results suggest that P300 measurements are useful and have additional value to speech recognition evaluations in cochlear implant users.

Adolescent↗
PubMed2001

The effect of short-term ventilation tubes versus watchful waiting on hearing in young children with persistent otitis media with effusion: a randomized trial.

OBJECTIVE: To study the effect of short-term ventilation tubes in children aged 1 to 2 yr with screening-detected, bilateral otitis media with effusion (OME) persisting for 4 to 6 mo, as compared with watchful waiting. DESIGN: Multi-center randomized controlled trial (N = 187) with two treatment arms: short-term ventilation tubes versus watchful waiting. Young children underwent auditory screening; those with persistent (4 to 6 mo) bilateral OME were recruited. RESULTS: The mean duration of effusion over 1-yr follow-up was 142 days (36%) in the ventilation tube (VT) group versus 277 days (70%) in the watchful waiting (WW) group. After 6 mo of follow-up, the pure-tone average in the VT group was 5.6 dB A better than that in the WW group. After 12 mo, most of the advantage in the VT group had disappeared. After the insertion of ventilation tubes, the children with poorer hearing levels at randomization improved more than the children with better hearing levels. The largest difference in hearing levels was found between the children in the VT group whose ventilation tubes remained in situ and the children in the WW group. In the VT children with recurrence of OME, the hearing levels again increased, but remained slightly lower than those in the infants with persistent OME in the WW group. CONCLUSIONS: Ventilation tubes have a beneficial effect on hearing in the short run (6 mo); this effect, however, largely disappears in the long run (12 mo). This is probably due to partial recurrent OME in the VT group and to partial spontaneous recovery in the WW group.

Algorithms↗
PubMed2001

The effects of readers' goals on inference generation and memory for texts.

We investigated the effects of readers' goals on inference generation and memory for expository text. College students (N = 82) read texts for the purpose of either study or entertainment. On-line inference generation was recorded via think-aloud procedures, and off-line memory was assessed via free recall. Reading goal strongly influenced inferential activity: Readers with a study goal produced more coherence-building (i.e., backward/explanatory and forward/predictive) inferences, whereas readers with an entertainment goal produced more associations and evaluations. These differences were associated with superior memory for the texts in the study condition. The results indicate that inference generation during reading is partly strategic and is influenced systematically by reading purpose. We propose that reading goals influence readers' standards of coherence, which in turn influence the types of inferences that they draw and the final memory representations that they construct.

Adult↗
PubMed2000

The effect of cochlear implant use in postlingually deaf adults.

OBJECTIVE: To assess the effect of the use of cochlear implants (CI) on the health status of postlingually deaf adults. METHODS: Participants comprised 45 postlingually deaf adult multichannel CI users and 46 deaf candidates on the waiting list for a CI. The latter group acted as control subjects to corroborate the validity of retrospective completion of the questionnaires by the CI recipients. Three HRQOL instruments were used: a) a specially developed CI questionnaire (NCIQ); b) a generic HRQOL questionnaire (SF-36); and c) a health-state classification system (HUI-2) suited to estimate single preference scores. RESULTS: Retrospectively estimated pre-implant scores in the CI user group corresponded very well with the scores in the control group. Postimplant scores in the CI users were substantially higher in all six domains (p < .001) of the NCIQ than the scores in the control group. Effects due to a CI were also observed with the SF-36 in five of the seven domains (p < .01). Statistically significant differences between the two groups (p = .001) were observed in two of the six domains of the HUI-2. CONCLUSIONS: All three questionnaires detected improvements in HRQOL due to CI use. To make a detailed assessment of the effect of a CI on functional outcomes and well-being, a special purpose HRQOL instrument is far more adequate than a general HRQOL instrument. This study also showed that a CI affects several other health domains besides auditory performance. The effect of CI use on general functioning and well-being proved to be considerable.

Adult↗
PubMed2000

The role of causal discourse structure in narrative writing.

All writers produce text content and ideally connect it together according to discourse conventions. We investigate whether a particularly strong discourse convention, the need for causal coherence in narratives, can predict the kind of text writers will produce. Causality has been found to be a significant discourse factor in reading comprehension and hence can be expected to determine also what writers produce during composition. In Experiment 1, writers composed short continuations at various points throughout a simple narrative, whereas in Experiment 2, writers composed continuations to complete several narratives. The results indicate that causality indeed plays a major role in composition. Writers tend to produce new text in such a way that it is causally connected to the prior text. Furthermore, writers favored causal relations of necessity or of necessity and sufficiency while largely avoiding relations of sufficiency alone, which suggests a general discourse constraint to be maximally informative (e.g., Grice, 1975).

Communication↗
PubMed2000

The effect of ventilation tubes on language development in infants with otitis media with effusion: A randomized trial.

OBJECTIVE: To study the effectiveness of ventilation tubes on the language development in infants with persistent otitis media with effusion (OME). All existing studies addressed children 3 years of age or older. Currently, OME is detected and treated with ventilation tubes at a younger age. Because of the critical relationship between age, hearing, and language development, we conducted a study of the effects of ventilation tubes on language development in infants 1 to 2 years old with persistent OME. DESIGN: A multicenter, randomized, controlled trial (embedded in a cohort) with 2 treatment arms: 1) treatment with ventilation tubes (VT group; n = 93); or 2) with a period of watchful waiting (WW group; n = 94). Hearing loss and expressive and comprehensive language were assessed every 6 months, while tympanometry and otoscopy were performed every 3 months. Other factors with potential influence on language development were also included: adenoidectomy, hospital, attending day care, sex, age at randomization, educational level of the mother, upper respiratory infections, and the native country of the parents and older siblings. The trial was designed to allow for the detection of a mean difference in language development of 3 months or more between children allocated to the VT and WW groups. RESULTS: No relevant differences were found in expressive or comprehensive language between the 2 groups after adjustment for educational level of the mother, IQ of the child, and differences at baseline. A principal component analysis showed that in the VT group, the children with frequent complaints improved 1.6 months more in comprehensive language than those with no or some complaints. The children with favorable language stimulation, however, did not improve more than the children with less favorable stimulation. No differences were found for expressive language among the various clusters. The probability to improve >3 months in comprehensive language was.48 (95% confidence interval [CI]:.29-.68) for children with highly educated mothers versus.09 (95% CI:.02-.30) for children whose mothers had a low educational level. In the WW group, these changes were.30 (95% CI:.14-.53) and.14 (95% CI:.04-.35), respectively. The probability to improve >4 months in expressive language was.52 (95% CI:.32-.71) for children with highly educated mothers versus.06 (95% CI:.01-.31) for children whose mothers had a low educational level. In the WW group these changes were.42 (95% CI:.23-.64) and.11 (95% CI:.03-.35), respectively. In addition, there were delays in expressive language in both groups compared with their age expected values. The comprehensive language of the children who were effusion-free during the follow-up (n = 54) improved 1.5 months (95% CI: -.2-3.2) more than that of the children who had persistent effusion during the entire follow-up (n = 28). No differences were found for expressive language development. Disregarding the intervention contrast, improvements in hearing seemed to be related to improvements in language development, especially in verbal comprehension. DISCUSSION: In this study, we used the Reynell, Schlichting, and Lexi tests to study the relation between early persistent OME and language development. These tests are directly related to normal language, widely accepted, and validated. It cannot be ruled out that more specific measures such as auditory perception tests would have produced more differences between groups, but the focus was on general language development. A total of 10 children in the WW group received treatment with ventilation tubes during follow-up. A further 11 children dropped out during the trial. A sensitivity analysis with the 10 children who received ventilation tubes did not change the results, and baseline differences were not found between the 11 children who dropped out and those who completed the trial. CONCLUSIONS: In the total group of infants with persistent OME, ventilation tubes did not h

Child Language↗
PubMed1999

Oral language acquisition in children assessed with the Reynell Developmental Language Scales.

Oral language development of ten children, prelingually deafened by meningitis, was assessed with a Dutch version of the Reynell Developmental Language Scales. The test was administered pre-operatively and at regular intervals after implantation. The average rate of language development between two consecutive evaluations was computed. This rate was defined as the quotient of the increase of the language age and the increase of the chronological age between the evaluations. A normal language development has a rate of 1; this means 12 months language development in 12 months time. In case of language retardation the rate of language development is less than 1. The rate of receptive language development showed a gradual increase. In the interval between 12 and 24 months of implant use the ratio was 0.9. This implies a language development that is quite similar with the development in normal hearing children. The rate of expressive language development showed a fast improvement in the period between 6 and 12 months after implantation, up to 1.4. If this rate of development continues the children with C.I. will catch up with their normal hearing peers.

Child↗
PubMed1999

Auditory training in severely and profoundly hearing impaired toddlers: the development of auditory skills and verbal communication.

Three different tests are applied to evaluate the performance of very young hearing impaired children. Three subgroups were formed according to hearing loss. The sound identification test as well as the Reynell Developmental Scales proved to be useful but Early Scales of Communication did not differentiate well enough between the three subgroups.

Auditory Perception↗
PubMed1999

Prognostic factors for persistent otitis media with effusion in infants.

OBJECTIVE: To study prognostic factors for persistent otitis media with effusion (OME) in a birth cohort of 30,099 children born in the eastern part of The Netherlands between January 1, 1996, and April 1, 1997. DESIGN: Case-referent study. SUBJECTS: Children who failed a triple hearing test before their first birthday and were subsequently diagnosed with bilateral OME during 3 of the 4 bimonthly visits to an ear, nose, and throat (ENT) department (n = 372). The persistent cases were compared with 3 referent groups: (1) all the children who attended the first of 3 hearing tests; (2) all the children of the birth cohort who were referred to an ENT department after the third hearing test; and (3) all the children who were diagnosed with bilateral OME during the first visit to an ENT department. RESULTS: When all the children who participated in the first hearing test were taken as referents, persistent OME was associated with upper respiratory tract infections, attending a day-care center, having older siblings, and a family history of otitis media. When all the children who were referred to an ENT department were taken as referents, only attending a day-care center was associated with persistent OME. When the children diagnosed with bilateral OME during the first visit to an ENT department were taken as referents, no prognostic factors were found for OME persistence. CONCLUSION: When a child is referred early, an otolaryngologist can ask the parent about the presence of prognostic factors to decide which policy to follow.

Case-Control Studies↗
PubMed1999

The relation of story structure properties to recall of television stories in young children with attention-deficit hyperactivity disorder and nonreferred peers.

In this study, the authors examined memory for televised stories to gain insight into similarities and differences in story comprehension between young children with attention-deficit hyperactivity disorder (ADHD) and their typical peers. In particular, the authors investigated the extent to which 4- to 6-year-old children's free recall of story events is predicted by several structural properties of story events (number of causal connections, whether an event is on or off the story's causal chain, story-grammar category, and position in the story's hierarchical structure), whether differences exist between children with ADHD and nonreferred comparison children in their sensitivity to structural features of stories, and whether age differences in sensitivity to structural features are similar for both groups. For both groups, recall of story events was predicted by all four structural properties, but the effects of the two causal properties was stronger for comparison children than for children with ADHD. Further examination revealed that this difference was observed only when a competing activity was available during television viewing. These findings indicate that both groups of preschool children are able to benefit from causal structure when recalling television stories, but that children with ADHD lose this benefit when attention is divided. Consistent with previous findings for nonreferred children (P. W. van den Broek, E. P. Lorch, & R. Thurlow, 1996), in both diagnostic groups the effects of causal properties increased across age, and older children were more likely to include causally important protagonists' goals in their recalls than younger children.

Attention Deficit Disorder with Hyperactivity↗
PubMed1999

Modelling surface potentials from intracochlear electrical stimulation.

Volume conduction models were used qualitatively to model surface potentials from cochlear implant patients recorded earlier by the authors. These recorded potentials reflected the equivalent dipole orientation in the head in patients who are deaf due to otosclerosis, but increased uniformly with the distance between the stimulating electrodes along the basilar membrane in other patients, which suggested a low and high resistivity of the cochlear bone, respectively. Several models of the head were constructed, with compartments representing the skin, skull, brain, cochlea, internal and external ear canal. In the "petrous bone" model, the cochlea was modelled as a cavity in a bony layer surrounded by the brain compartment. Of all models, the petrous bone model using a high resistivity ratio (1:100) between the bony and the other compartments was the only one that produced outcomes similar to the potentials observed in non-otosclerosis patients. In conclusion, the results suggested that the surface potentials observed in non-otosclerosis patients are sufficiently explained by a high impedance between cochlear turns and a non-specific return of current via the wall of the petrous bone into the larger brain compartment.

Cochlea↗
PubMed1998

[Cochlear implantation in deaf children].

OBJECTIVE: To evaluate the results of cochlear implantation in deaf children. DESIGN: Descriptive. SETTING: Ear, nose and throat department, Academic Hospital, Nijmegen, and Institute for the Deaf St. Michielsgestel, the Netherlands. METHODS: The results in 29 totally deaf children implanted with a 22-channel Nucleus implant--partly in a project supported by the National Fund for Investigative Medicine--in the period 1990-1996 were determined. Six of the children had congenital deafness, the others were deaf as a sequel to meningitis. The operation had no serious complications. All children were followed for at least two years. Progress in auditory perception and speech-language development were measured with structured tests. RESULTS: There was a marked improvement in auditory performance, and language development (measured with Reynell test), although the level of normal hearing children was not reached by most of the operated children. The results were better for children with total insertion of the electrodes than for those with partial insertion (n = 4); of these last, one stopped using the implant. CONCLUSION: Cochlear implantation can limit the consequences of total deafness in children.

Adolescent↗
PubMed1998

Can event-related potentials be evoked by extra-cochlear stimulation and used for selection purposes in cochlear implantation?

To investigate whether electrically evoked event-related responses (P300) could be elicited by extra-cochlear stimulation, measurements were performed on a group of adults fitted with the single-channel extra-cochlear implant. To optimize measurement conditions, and because of the low number of subjects still using an extra-cochlear device in our cochlear implant programme, measurements were also performed on a group of experienced users fitted with the intra-cochlear Nucleus multichannel device. For reference purposes, subjects with normal hearing (control group) were also included in the study. Reproducible late latency responses (N1 and P2 peaks) were found in the five extra-cochlear implant users, while P300s were present in four out of these five subjects. The latencies were longer than those of the control group, but were similar to those obtained in the intra-cochlear implant group. Significant correlations were found for most N1, P2 and P300 measurements evoked by the tonal stimuli and by speech stimuli. The P300 amplitudes, evoked by either tonal or speech stimuli, appeared to be related to speech perception ability. This led to the conclusion that N1, P2 and P300 measurements may have potential as a clinical tool for preoperative prediction and postoperative evaluation of sound processing on a cortical level.

Adolescent↗