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PubMed1994

Frequency-resolution measurements with notched noises for clinical purposes.

Knowledge of the frequency resolving power of the pathological ear can be helpful for good hearing-aid prescription. In particular, the slope of the low-frequency edge of the auditory filter will determine the extent of upward spread of masking. The most precise method for measuring this filter is the "notched-noise" procedure developed in the early 1980s. However, at this moment, the notched-noise protocol is too time consuming for clinical use. In this paper we developed a protocol that is applicable in the clinic. In the first part of the study we investigated the minimum number of threshold measurements necessary for a reliable estimation of the filter parameters. For this purpose we analyzed 99 filters originally obtained with 13 threshold measurements. The influence of reducing the number of notch widths used to obtain filter shapes on the variability of filter parameters was investigated. Subsets of seven and five notch widths gave about the same standard deviations of the differences between the parameters obtained with the subset and the parameters obtained with the full set of 13 thresholds, while subsets of four and three notch widths gave significantly higher variability. However, because small deviations of one threshold determination can give rise to a large change in filter parameters, especially for filters with flatter skirts, it is strongly recommended to reduce the variability by measuring thresholds twice (test and retest). In the second part of the study we investigated a faster method for measuring thresholds. The forced-choice paradigm normally used in notched-noise procedures was replaced by a Békésy paradigm. The Békésy paradigm did not significantly increase intra-individual standard deviations, but did reduce the measuring time by more than 50%. In conclusion, the new procedures reduce the measurement time needed to obtain reliable estimates of auditory-filter parameters by a factor of about 5. The new protocol lasts about 15 min for each filter measurement, which appears to be acceptable for clinical use, at least for difficult-to-fit hearing aid users.

Acoustic Stimulation↗
PubMed1994

Comparison of early communicative behavior in young children with cochlear implants and with hearing aids.

Analysis of preverbal behaviors, which are the natural precursors of language development, was performed in three groups of young children with severe/profound hearing impairments, based on video recordings of interactions with a known adult. All groups were matched for age at assessment. One group of nine children had Nucleus multichannel cochlear implants with the MSP sound processor, whereas the other two groups of nine children each used conventional hearing aids. The first hearing aid group had unaided hearing threshold levels averaging 101 dB and were proficient users; the second aided group had hearing threshold levels averaging 114 dB and were poor users. Over the assessment period lasting 12 mo, starting at implantation or entry to nursery school according to group, implantees and proficient hearing aid users developed a strongly vocal/auditory style of communicative behavior, especially the implantees. This contrasted with a strongly visual/gestural style developed by the poor hearing aid users. It is concluded that implantees develop their early communicative behavior along lines that are similar to proficient hearing aid users, but more rapidly and more strongly in the vocal/auditory direction.

Auditory Perception↗
PubMed1994

Improvement in auditory function following pentazocine suggests a role for dynorphins in auditory sensitivity.

The pharmacologic specificity of potentially beneficial drug effects on the auditory system were investigated. Changes in auditory sensitivity were evaluated in chinchillas following the infusion of an opioid narcotic. This drug (pentazocine) mimics endogenous opioid peptides (dynorphins), postulated to be chemical neurotransmitters (or neuromodulators) within the mammalian cochlea. In this study, two pentazocine enantiomers were investigated over a range of stimulus intensities. Significant baseline-relative changes in compound action potential (CAP) amplitudes were observed following intravenous administration of the kappa-opioid agonist (-)pentazocine (8 mg/kg). The sigma-receptor drug agonist (+)pentazocine (8 mg/kg) produced no measurable auditory effects. The magnitude of the (-)pentazocine effects were inversely related to stimulus intensity, up to 10 dB above threshold (i.e., 10 dB SL). Consistent with the observed amplitude doubling, auditory sensitivity was also improved an average 5-7 dB sound pressure level (SPL) following the administration of (-)pentazocine, while CAP response latencies and cochlear microphonic (CM) amplitudes remained unchanged. Results indicate stereospecific kappa-receptor mediated actions of pentazocine at the auditory nerve, and suggest an auditory role for neuroactive dynorphin peptides contained within the lateral efferent olivocochlear neurons.

Animals↗
PubMed1995

Comparison of objective threshold estimation procedures for 40-Hz auditory evoked potentials.

OBJECTIVE: Objective threshold estimation is possible using statistics such as magnitude-squared coherence (MSC) and responses such as the 40-Hz auditory evoked potential (AEP). The purpose of this paper is to compare three general methods of threshold estimation using MSC. DESIGN: Using 500-Hz amplitude-modulated tones and 40-Hz AEPs from 10 paid-volunteer young adults with normal hearing, we compared three MSC-based threshold estimation methods--extrapolation, intensity series, and adaptive. RESULTS: The extrapolation method yielded low thresholds but unacceptable variability. The intensity series method was insensitive and time-consuming. Two adaptive methods displayed good performance in terms of precision and sensitivity. The first employed an MSC criterion with a 13.5% false positive rate (per trial), but achieved overall false positive rates under 5% after 5 to 7 runs, requiring 30 to 40 minutes test time (a run is a single set of ascending or descending trials, terminated by a reversal). The second, which performed better overall, included only a single run, but collected more data at intensities near threshold than at higher intensities; test time could be further reduced (from 22 to 18 minutes) by using a stopping rule based on initial MSC and noise power estimates at each test intensity. If speed is paramount, a simple single-run method achieved threshold estimates in about 9 minutes, starting at 40 dB nHL, with acceptable precision but less sensitivity. CONCLUSIONS: A single-run adaptive method, with or without collection of additional data near threshold, yielded the best results, in terms of statistical performance and data collection time.

Adult↗
PubMed1995

Effects of reference interaural time and intensity differences on binaural performance in listeners with normal and impaired hearing.

OBJECTIVE: The purpose of this research was to measure the effects of reference interaural time and intensity differences on binaural performance in listeners with normal hearing and impaired hearing for a number of different binaural tests. Experiment 1 measures the dependence of binaural detection and discrimination performance on reference interaural intensity differences (IID) in the range of +/- 12 dB for listeners with normal hearing. Experiment 2 extends these measures to include reference IIDs and interaural time differences (ITD) for two groups of listeners with normal hearing with offsets in the range of +/- 12 dB and +/- 300 microseconds (group 1) and +/-24 dB and +/- 600 microseconds (group 2). Experiment 3 includes the same tests and conditions as experiment 2 for listeners with various hearing impairments. DESIGN: A set of psychophysical measurements was completed on 11 listeners with sensorineural hearing losses and 9 listeners with clinically normal hearing. The primary measurements were a set of four binaural detection and interaural discrimination thresholds measured for two 1/3-octave bands of Gaussian noise, one centered at 500 Hz and the other at 4000 Hz. Specifically, we measured binaural (antiphasic) detection thresholds for tones centered in the masking noise as well as the just-noticeable differences (JNDs) in IID, ITD, and interaural cross-correlation (ICC) for each of the noise-band stimuli. All measurements were done for a number of combinations of reference IID and ITD. In addition to these primary measurements, several other measurements were made on each subject, including monaural absolute thresholds, monaural intensity discrimination, monaural masked thresholds, and intensity levels required for interaurally balanced loudness and for a centered image. All measurements were made using a relatively quick, adaptive procedure. RESULTS: For the subjects with normal hearing, measured dependencies of the IID and ITD JNDs using noise stimuli on reference ITD and IID are different from those previously reported for tonal stimuli. Binaural performance of the listeners with impaired hearing varies widely across subjects and tests and is generally poorer than that of listeners with normal hearing. CONCLUSIONS: On the basis of the results for subjects with hearing impairments, we have reached several conclusions. First, the results for the binaural measurements cannot be explained in terms of available monaural audiometric and psychophysical measurements on these subjects. Second, the subjects' binaural abilities show no significant improvement with any combinations in the reference values of ITD and IID, providing negative evidence for the hypothesis that degraded performance for some subjects may be due to internal interaural offsets in ITD or IID. Third, the hypothesis that binaural detection and ICC discrimination are related, suggested by Durlach et al (1986), is generally supported. Fourth, binaural detection performance is not simply explained in terms of sensitivities to ITD and IID.

Adolescent↗
PubMed1998

Steady-state evoked potential and behavioral hearing thresholds in a group of children with absent click-evoked auditory brain stem response.

OBJECTIVE: 1) To examine the distribution of behavioral hearing thresholds in a group of children who had shown no click-evoked auditory brain stem response (ABR) at maximum presentation levels. 2) To describe the relationship between the 90 Hz steady-state evoked potential (SSEP) and behavioral thresholds in these subjects. DESIGN: A retrospective study based on clinical findings obtained from 108 infants and young children. Each of these children had shown no recordable ABR to clicks presented at maximum levels (100 dB nHL). SSEP audiograms were obtained using AM/FM tones at the octave frequencies 250 to 4000 Hz. The results of these evoked potential assessments were compared with hearing thresholds established behaviorally. RESULTS: Click-ABR assessment could not differentiate between the subjects in our sample with total hearing losses and those with useful residual hearing. Although some of the ears were anacusic, more than a quarter showed residual hearing at each of the audiometric frequencies. Furthermore, at least 10% of the behavioral thresholds at each frequency fell within the moderate/severe hearing loss range. A far closer relationship was observed between SSEP and hearing thresholds. On occasions where the SSEP was absent at maximum levels, 99.5% of the ears showed either a total loss or a behavioral threshold within 10 dB of that level. When an SSEP was obtained, the hearing threshold was typically within 5 dB of the SSEP threshold. CONCLUSION: The results suggested that in our group of selected subjects, the SSEP technique was able to assess ears with only minimal amounts of residual hearing. Where the brevity of the acoustic click limits both its frequency specificity and its presentation level, the modulated tones used for SSEP testing allow accurate, frequency-specific assessment at high presentation levels.

Acoustic Impedance Tests↗
PubMed1998

The effect of masker interaural time delay on the masking level difference in children with history of normal hearing or history of otitis media with effusion.

OBJECTIVE: To determine the relation between the masking level difference (MLD) and the interaural time delay of the stimulus in children with a history of normal hearing and with a history of otitis media with effusion (OME). DESIGN: MLDs for a 500 Hz pure tone presented in a 100 Hz-wide masking noise were determined as a function of the interaural delay of the masker (six interaural delays between -726 microsec and +998 microsec were examined). For the masker with zero interaural delay, the signal was presented either interaurally in-phase or 180 degrees out of phase. For the masker delay conditions, the signal was given the same interaural delay as the masker and then was inverted interaurally. All children had normal audiograms at the time of testing. Ten children had a history of normal hearing and seven children had a history of OME. RESULTS: Similar to what has been found previously in adults, children with a history of normal hearing showed the maximum MLD (approximately 16 dB) for an interaural time delay of 0 microsec, with the MLD decreasing as a function of interaural time delay (by as much as 4 to 5 dB for the extreme delays). Children with a history of OME had significantly smaller MLDs than normal for the three smallest interaural delays but did not differ significantly from normal at the three largest interaural delays. CONCLUSIONS: The form of the function relating masker interaural time delay to MLD magnitude is adult-like by age 6 yr. The function indicates a binaural advantage for the processing of sound near auditory midline. This advantage is less apparent in children having a history of OME.

Audiometry, Pure-Tone↗
PubMed1999

Sex differences in auditory sensitivity of chinchillas before and after exposure to impulse noise.

OBJECTIVE: To determine if chinchillas exhibit sex differences in 1) basic auditory sensitivity and 2) susceptibility to cochlear damage and hearing loss from high-level impulse noise. DESIGN: The auditory sensitivity of 73 chinchillas was assessed by measuring evoked potentials from electrodes implanted in the inferior colliculus (IC-EVPs) and cubic (2f1-f2) distortion product otoacoustic emissions (CDPs). A subgroup of 16 chinchillas were retested after exposure to simulated M16 rifle fire (150 dB pSPL impulse noise). Thresholds and postexposure temporary and permanent threshold shifts were compared as a function of sex and frequency using analysis of variance procedures. Cochleograms, showing the percent of hair cells missing as a function of location on the basilar membrane, were constructed to show inner hair cell (IHC) and outer hair cell (OHC) losses for each group. RESULTS: Female chinchillas had slightly lower high-frequency thresholds, and slightly higher low-frequency thresholds than male chinchillas, but similar IC-EVP and CDP amplitude functions. Significant sex differences were observed after exposure to high-level impulse noise. Overall, female chinchillas developed approximately 10 dB more high-frequency hearing loss, but approximately 5 dB less low-frequency hearing loss than males. Hair cell losses, particularly IHC losses, were substantially less for females as compared with males. CONCLUSIONS: The results point to close similarities between chinchillas and humans with regard to sex/gender differences in basic auditory sensitivity before noise exposure, suggesting that the chinchilla may be a good model for exploring the anatomical and physiological bases of these differences. In addition, the results show significant sex differences in the physiological and anatomical response of the chinchilla cochlea to high-level noise. Similar differences in humans could have important implications with regard to military assignments and hearing conservation programs.

Animals↗
PubMed1999

Unmasked thresholds and minimum masking in infants and adults: separating sensory from nonsensory contributions to infant-adult differences in behavioral thresholds.

OBJECTIVE: The purposes were to determine the degree to which infant unmasked thresholds differed from those of adults, to determine the effect of signal frequency on those differences, and to determine whether there is a difference in minimum effective masking as a function of age and frequency. The data were applied to a model to address the question of the origin (sensory versus nonsensory) of infant-adult differences in behavioral unmasked thresholds. DESIGN: Infant behavioral thresholds in quiet and in noise for pure tones of 0.5 and 2 kHz were measured using computer-based visual reinforcement audiometry. Adult thresholds were measured using the same apparatus and a modified conventional audiometric procedure. Twenty-three infants and 24 adults were included in the analyses. The masked thresholds versus masker intensity data were used to estimate minimum masking levels (MMLs). RESULTS: Group mean unmasked thresholds of infants were greater than those of adults at both frequencies and the difference was greater at 0.5 kHz (14.2 dB) than at 2 kHz (5.5 dB). Infant MMLs were greater than those of adults by 10.1 dB at 0.5 kHz and by 1.2 dB at 2 kHz. The fact that a masker had to be 10.1 dB greater in intensity for infants than for adults at 0.5 kHz and 1.2 dB greater at 2 kHz suggests that there is a difference in sensitivity between the groups of about 10 and 1 dB for the two frequencies, respectively. According to a proposed model, the difference between infants and adults in MMLs is less than the difference in unmasked thresholds owing to the influence of nonsensory factors that bias infant unmasked thresholds. Such factors, therefore, contribute 4.1 dB (i.e., 14.2 dB-10.1 dB) at 0.5 kHz and 4.3 dB (i.e., 5.5 dB-1.2 dB) at 2 kHz based on the data. CONCLUSIONS: The infant-adult differences in unmasked thresholds, with greater difference at 0.5 kHz than at 2 kHz, are consistent with earlier research on infant hearing. The data reveal that the greater difference between infants and adults at 0.5 kHz relative to 2 kHz is not a result of nonsensory factors alone, but is largely due to a difference in sensory processing. Only about 4 dB of the difference between infants and adults in unmasked thresholds can be attributed to nonsensory factors and the effect is not frequency specific according to the proposed model. Consideration of establishing audiometric reference values for infants that are different than those based on adults, owing to the elevated behavioral unmasked thresholds of normal-hearing infants, is suggested.

Adult↗
PubMed2000

Self-reports about tinnitus and about cochlear implants.

OBJECTIVE: Analyze literature on self-report outcomes in two areas of audiological rehabilitation: 1) tinnitus and 2) cochlear implant hearing aids. DESIGN: 1) Tinnitus: survey of features in the development of self-report approaches and of formal scales used in assessment of tinnitus disability and handicaps. 2) Cochlear implants: summary of the literature using self-report approaches to cochlear implant experience that indicates points of theoretical significance. RESULTS: 1) Major features of tinnitus are: a) disabilities such as interference with and distortion of normal auditory perception; b) handicaps such as emotional distress, interference with sleep, and with personal and social life. Nonauditory factors-chronic depression, high self-focused attention-mediate the degree of experienced tinnitus handicap. 2) People with prelingual loss of hearing report that a cochlear implant primarily enables improved detection and discrimination of environmental sound; those with postlingual loss find that an implant in addition provides improved speech recognition. CONCLUSIONS: 1) Coping with tinnitus is influenced by the personal resources that can be brought to bear on the experience, highlighting a general point that any rehabilitation outcome is not only a matter of acoustical solutions. By the same token, tinnitus can be easier to cope with if its "psychoacoustic presence" can be diminished by some form of masking. 2) Cochlear implants fitted in childhood that do not provide meaningful input signals in real-world settings may be rejected in adolescence. 3) "Hearing," as a capacity, does not have a fixed worth. Different circumstances mean it will be taken as desirable or as delivering torment (extreme tinnitus, e.g.). Its value will also vary depending on the extent of a person's access to spoken language (aiding in very early childhood, e.g.).

Adaptation, Psychological↗
PubMed2004

Effects of a suppressor tone on distortion product otoacoustic emissions fine structure: why a universal suppressor level is not a practical solution to obtaining single-generator DP-grams.

OBJECTIVES: The use of a suppressor tone has been proposed as the method of choice in obtaining single-generator distortion product (DP) grams, the speculation being that such DP grams will be more predictive of hearing thresholds. Current distortion product otoacoustic emissions (DPOAE) theory points to the ear canal DPOAE signal being a complex interaction between multiple components. The effectiveness of a suppressor tone is predicted to be dependent entirely on the relative levels of these components. We examine the validity of using a suppressor tone through a detailed examination of the effects of a suppressor on DPOAE fine structure in individual ears. DESIGN: DPOAE fine structure, recorded in 10 normal-hearing individuals with a suppressor tone at 45, 55, and 65 dB SPL, was compared with recordings without a suppressor. Behavioral hearing thresholds were also measured in the same subjects, using 2-dB steps. RESULTS: The effect of the suppressor tone on DPOAE fine structure varied between ears and was dependent on frequency within ears. Correlation between hearing thresholds and DPOAE level measured without a suppressor was similar to previous reports. The effects of the suppressor are explained in the theoretical framework of a model involving multiple DPOAE components. CONCLUSIONS: Our results suggest that a suppressor tone can have highly variable effects on fine structure across individuals or even across frequency within one ear, thereby making the use of a suppressor less viable as a clinical tool for obtaining single-generator DP grams.

Acoustic Stimulation↗
PubMed2005

Effect of audiometric configuration on threshold and suprathreshold auditory steady-state responses.

OBJECTIVE: The purpose of this study was to examine the correlation between auditory steady-state response (ASSR) thresholds and behavioral thresholds in hearing-impaired adults with two common audiometric configurations. A second goal was to compare suprathreshold ASSR growth functions in these two subject groups and to determine whether these growth functions could be used clinically to improve threshold estimation. DESIGN: Thirty adults participated, including 10 subjects with normal hearing, 10 subjects with flat moderately severe sensorineural hearing loss, and 10 subjects with sloping high-frequency sensorineural hearing loss. The accuracy of ASSR threshold estimations for the frequencies of 500, 1000, 2000, and 4000 Hz was compared across groups. In addition, ASSRs were recorded at multiple suprathreshold intensity levels, and the growth of the response was compared across subject groups. RESULTS: ASSR and behavioral thresholds were strongly correlated across all subjects, with no significant difference by audiometric configuration. Slightly poorer correlations were obtained in the normal-hearing subjects than in hearing-impaired subjects and for the 500-Hz test frequency compared with the higher stimulus frequencies. Subtraction and regression methods for predicting behavioral thresholds from ASSR thresholds were equally accurate. Suprathreshold amplitude growth was variable among individuals, but mean growth functions showed steeper slopes in hearing-impaired subjects than in normal-hearing subjects, particularly for the higher frequencies (2000 to 4000 Hz). However, there was not a significant difference in the slopes of amplitude growth functions between subjects with sloping versus flat audiometric configurations for these frequencies, and estimation of threshold from suprathreshold ASSR amplitude growth functions was not advantageous. CONCLUSIONS: ASSR thresholds accurately predicted behavioral threshold equally well for flat or sloping audiometric configurations. The accuracy of threshold estimation for either audiometric configuration and the similar growth function slopes may suggest that there is little spread of activation to neighboring regions of the cochlea when using multiple 100% AM stimuli in subjects with moderately sloping losses. The small amplitude of the ASSR response and individual variability may make threshold estimation based on extrapolation from suprathreshold ASSR responses impractical.

Acoustic Stimulation↗
PubMed2005

Prelexical vocalization in normal hearing and hearing-impaired infants before and after cochlear implantation and its relation to early auditory skills.

OBJECTIVES: To compare the vocalizations of hearing-impaired infants before and after cochlear implantation with those of a control group of hearing infants and to relate prelexical vocalizations by using the PRoduction Infant Scale Evaluation (PRISE) to early auditory skill attainments, using the Infant-Toddler Meaningful Auditory Integration Scale (IT-MAIS) in normal-hearing and hearing-impaired (HI) infants before and after cochlear implantation. DESIGN: A total of 187 infants participated in the study: 24 HI infants with severe-profound hearing loss (8 to 23 months of age) and 163 hearing infants (0.5 to 20 months of age). Prelexical vocalizations and early auditory skills were assessed by using parent questionnaires (PRISE and IT-MAIS, respectively) that reflect known milestones in the infant's vocal and auditory development. HI infant data were compared with hearing infant data according to chronological age and duration of device use (hearing aid or cochlear implant). RESULTS: Average PRISE score of aided HI infants before implantation was 50% or less (regardless of age). This score is comparable to that of hearing infants who are 6 to 7 months of age. After implantation, HI infants reached a score of 70% but did not reach normative performance. When HI infant data were compared with hearing infants by duration of device use, aided infants before implantation performed as well or worse than normative performance, whereas implanted infants performed as well as or better than hearing infants. Performance on individual PRISE questions showed limited ability by HI infants before implantation compared with hearing and implanted infants. A strong correlation was found between the IT-MAIS and the PRISE (r = 0.93 and r = 0.83, for hearing and HI infants, respectively). CONCLUSIONS: The PRISE was found to be a versatile tool for implant team clinicians who are required to assess prelinguistic skills of infants. The findings suggest that early auditory skills are related to prelexical vocalization. The data also highlighted unanswered questions related to the importance of early fitting of hearing aids on vocalization before and after implantation.

Auditory Perception↗
PubMed2005

Genetic algorithms for adaptive psychophysical procedures: recipient-directed design of speech-processor MAPs.

OBJECTIVES: The goal of the research is to evaluate the application of genetic algorithms (GAs) in listener-directed optimization of audio-processing designs. We hypothesize that cochlear-implant recipients can use a GA-guided adaptive psychophysical search procedure to select useful designs from among a large number of speech processor MAPS. DESIGN: An adaptive psychophysical procedure was developed in which a listener's preferred four out of eight speech processor MAPs were updated according to a genetic algorithm. Experiments involving cochlear-implant recipients were conducted to characterize both the convergence behavior of the adaptive procedure as well as properties of the MAPs optimized by the recipient. RESULTS: Results from five cochlear-implant recipients indicate that the adaptive procedure converges to useful speech processor MAPs within twenty iterations. CONCLUSION: The results suggest a means whereby a potentially large number of audio-processing designs can be searched efficiently by a human listener without requiring excessive amounts of feedback or prior knowledge about the listener's preferences. In the case of cochlear-implant recipients, it may be possible to use this procedure as an aid to the clinician in the fitting of a speech processor MAP.

Adaptation, Physiological↗
PubMedDate not supplied

Acoustic echoplanar scanner noise and pure tone hearing thresholds: the effects of sequence repetition times and acoustic noise rates.

PURPOSE: Our goal was to determine the effects of acoustic echoplanar scanner noise on pure tone hearing thresholds in normal volunteers and to determine the influence of echoplanar sequence repetition time on threshold effects. METHOD: With use of a calibrated audiometer, pure tones ranging from 125 to 8,000 Hz were delivered monaurally to 10 normal-hearing volunteers in a quiet MR scanner suite and in the presence of acoustic scanner noise produced by three separate single shot blipped echoplanar pulse sequences varying only in repetition time (TR = 1,000, 2,000, or 3,000 ms), with all other parameters including the number of slices held constant. The magnitude of noise-induced threshold changes and the slopes of the threshold curves produced by each of the three echoplanar pulse sequences were then analyzed using multiple comparisons and a least significant difference method. The shapes of the threshold curves produced in each background state were best fit using a quadratic effect for frequency in a mixed effects linear model and compared using F test statistics. RESULTS: All of the volunteers demonstrated entirely normal hearing thresholds throughout the full range of tonal frequencies tested (< 25 dB) when no acoustic scanner noise was present in the scanner suite. Pure tone hearing thresholds significantly increased (p < 0.01) in the presence of acoustic scanner noise, with the magnitude of change inversely proportional to the repetition time and therefore the rate of periodic noise production by the echoplanar sequence used. The shape of the threshold curve in the presence of noise produced by the 1,000 ms TR sequence was not equivalent across the frequency spectrum tested but had a quadratic distribution with peak effects at 750-2,000 Hz. As the repetition time was increased and the periodic noise rate decreased, the magnitude of the noise-induced threshold changes significantly lessened (p < 0.01) and the quadratic distributions of the threshold curves changed significantly (p < 0.01), tending toward a more planar configuration. CONCLUSION: Background acoustic echoplanar scanner noise can significantly increase pure tone thresholds in the optimal frequency hearing range (125-8,000 Hz). However, the threshold effects are not equivalent across the frequency spectrum, and the magnitude of threshold changes is dependent on the rate at which periodic acoustic scanner noises are produced for a given sequence repetition time.

Acoustic Stimulation↗
PubMed1986

The effects of an auditory subliminal message upon the production of images and dreams.

The purpose of this research was to investigate what effect an auditory subliminal message, produced by speeding up the rate at which it was recorded, would have upon the imagery and dreams of a group of normal subjects. The auditory subliminal message was produced by speeding up a message that was sung until it could not be consciously understood. This message was mixed with a normal music recording and played to nine subjects in the experimental group. Nine subjects in the control group heard the normal music recording without the subliminal message. Both groups were asked to produce a pretest drawing before the tapes were played, an imagery drawing immediately after the tapes were played, and a dream drawing of any dreams they might have that night. A statistical analysis was performed from data collected on blind ratings given to all the drawings by two art therapists. The results indicated a significant difference between the dream drawings and the imagery drawings of the experimental group and the control group. When the drawings were examined, the effect of the subliminal message could be seen. Based on the statistical data and certain drawings collected in this study, it would appear that the auditory subliminal message did have an effect upon the imagery and dreams of the subjects in the experimental group. The results of this study appear to indicate that the unconscious/preconscious mind is able to perceive a recorded verbal message that cannot be consciously understood at the high rate of speed at which it was recorded.

Acoustic Stimulation↗
PubMed1991

Dichotic listening failure in dysphoric neuropsychiatric patients who endorse multiple seizure-like symptoms.

In the present investigation, the dichotic word listening performance of a sample of 25 dysphoric neuropsychiatric patients who endorsed multiple partial seizure-like symptoms was compared with that of matched samples of normal controls and patients with mood disorders who did not endorse multiple seizure-like symptoms. Eighty percent of the patients who endorsed multiple episodic phenomena failed the dichotic listening task, compared with 8% of normal controls and 28% of patients with typical mood disorders. After treatment with carbamazepine, a subsample of polysymptomatic patients manifested significantly fewer seizure-like symptoms. This clinical improvement was typically associated with markedly improved dichotic listening performance in most cases. The results are consistent with our previous hypothesis that "subclinical" electrophysiological dysfunction may severely disrupt the normal transmission and processing of auditory information. Because it is sensitive to this type of presumed cerebral dysfunction and relatively specific, impaired dichotic listening performance is likely to be a useful clinical marker for this complex neuropsychiatric syndrome.

Adult↗