Binaural hearing in adults with histories of otitis media in childhood

Monaural and binaural phase sensitivity in school-age children with early-childhood otitis media

OBJECTIVE

Previous research has linked recurrent otitis media (OM) during early childhood to reduced binaural masking level differences (BMLDs) in school-age children. How this finding relates to monaural processing abilities and the individual otologic history has not been investigated systematically. The current study, therefore, addressed these issues.

DESIGN

Sensitivity to monaural and binaural phase information was assessed using a common test paradigm. To evaluate the influence of the otologic history, overall OM duration, OM onset age, and the time since the last OM episode were considered in the analyses.

STUDY SAMPLE

Children aged 6-13 years with a history of recurrent OM (N = 42) or without any previous ear diseases (N = 20).

RESULTS

Compared to the controls, the OM children showed smaller BMLDs (p < 0.05) whereas their monaural and binaural detection thresholds were comparable (p > 0.05). After controlling for age, the otologic history factors failed to predict the BMLDs of the OM children. Their monaural detection thresholds were correlated with the binaural detection thresholds (r = ∼0.5, p < 0.05) but not the BMLDs.

CONCLUSIONS

The current study suggests that early-childhood OM can impair binaural processing abilities in school-age children.

Critical periods of brain development

Brain plasticity is maximal at specific time windows during early development known as critical periods (CPs), during which sensory experience is necessary to establish optimal cortical representations of the surrounding environment. After CP closure, a range of functional and structural elements prevent passive experience from eliciting significant plastic changes in the brain. The transition from a plastic to a more fixed state is advantageous as it allows for the sequential consolidation and retention of new and more complex perceptual, motor, and cognitive functions. However, the formation of stable neural representations may pose limitations on future revisions to the circuitry. If sensory experience is abnormal or absent during this time, it can have profound effects on sensory representations in adulthood, resulting in quasi-permanent adaptations that can make it nearly impossible to learn certain skills or process certain stimulus properties later on in life. This chapter begins with a brief introduction to experience-dependent plasticity throughout the lifespan (Section Introduction). Next, we define what constitutes a CP (Section What Are Critical Periods?) and review some of the key CPs in the visual and auditory systems (Section Key Critical Periods of Sensory Systems). We then discuss the mechanisms whereby cortical plasticity is regulated both locally and through neuromodulatory systems (Section How Are Critical Periods Regulated?). Finally, we highlight studies showing that CPs can be extended beyond their normal epochs, closed prematurely, or reopened during adult life by merely altering sensory inputs (Section Timing of Critical Periods: Can CP Plasticity Be Extended, Limited, or Reactivated?).

Central auditory processing disorder in school-aged children: a critical review

The rationale to evaluate for central auditory processing disorder (CAPD) in school-aged children is based on the assumption that an auditory-specific perceptual deficit underlies many learning problems including specific reading and language disabilities. A fundamental issue in this area is whether convincing empirical evidence exists to validate this proposition. Herein, we consider the issue of modality specificity by examining the extent to which reading, language, and attention disorders in school-aged children involve perceptual dysfunctions limited to a single sensory modality. Difficulty in validating CAPD as a diagnostic label is due in large part to use of the unimodal inclusive framework, which has biased the diagnosis to favor sensitivity of test results over documenting the specificity of the deficit. Indeed, empirical research documenting modality-specific auditory-perceptual dysfunction in this population is scarce. Therefore, the existing literature on this topic has not clarified the "true" nature of the problem, and has left many questions about this disorder unanswered. It is argued that demonstrating modality specificity is one way to rule out supramodal disorders as explanations for observed dysfunction. Multimodal perceptual testing is one logical approach to help clarify this area of investigation.

The acoustic reflex in adults with histories of otitis media in childhood

OBJECTIVE

To investigate the effects of a history of otitis media (OM) in childhood on the acoustic reflex threshold (ART) in young adults.

DESIGN

Questionnaire responses on childhood ear and hearing problems were obtained from populations of university students. In Study 1, 31 students reporting histories of persistent childhood OM and 34 students with no known OM histories were identified. They received pure-tone audiometry, otomicroscopy, and measurement of ARTs for a 500 Hz pure tone. In Study 2, 20 students with OM histories and 20 students with no known OM histories received pure-tone audiometry, otomicroscopy, and measurement of ARTs for a broadband noise.

RESULTS

Subjects with OM histories had higher ARTs than did subjects with no known OM histories. Multiple regression analyses showed that the main variables contributing to elevated reflex thresholds were raised hearing thresholds on the activator ear and tympanic membrane abnormalities on the probe ear.

CONCLUSIONS

The elevated ARTs in adults with histories of childhood OM result from peripheral sequelae of OM. Further evidence is required to determine any functional significance of these raised reflex thresholds.

Binaural summation of the acoustic reflex

OBJECTIVE

The ways in which summation of energy or of information occurs have long been used to explore sensory mechanisms. In the case of the acoustic reflex, some binaural summation is known to occur, but both data and specification of method have been sketchy. Accurate estimates of mean and standard deviation were therefore sought to compare binaural acoustic reflex summation (BARS) with binaural loudness summation (BLS) to determine whether these have a common basis.

DESIGN

A specified method was developed for determining reliable acoustic reflex values from admittance/intensity functions. Subjects were 34 university students; the ages ranged from 18 through 25 yr. For each, the contralateral component of the binaural stimulus was presented at a level above the ipsilateral component corresponding to the difference in monaural reflex thresholds ("physiologically equivalent").

RESULTS

BARS had a mean of 4.4 dB (SD = 3.5 dB), which was significantly different from the BLS (mean = 7.6 dB, SD = 1.2 dB). The contralateral-ipsilateral difference had a mean of 11.0 dB (SD = 5.1 dB). The BARS estimate was not appreciably larger than that found in studies lacking correction for physiologic equivalence.

CONCLUSIONS

Although the presence of a contralateral component elicits a summation or facilitation effect, the particular intensity value contributes little to the magnitude of that effect.

Evaluation of self-report by adults of childhood otitis media histories

Several studies have suggested that reported auditory disabilities in adults are associated with reported histories of otitis media (OM) in childhood. However, no evaluation has previously been made of the accuracy of recall of childhood OM by adult subjects. In an investigation in university students, questionnaire responses on childhood OM histories were evaluated for 31 subjects reporting no known OM histories. Responses were compared with information obtained from GP (Family Doctor) records and parents. Agreement was very good for questions on ENT surgery, reasonably good for attendances at ENT clinics and poorer for GP attendances. It was concluded that the questionnaire approach was sufficiently valid in obtaining information from adults about childhood OM histories.