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At least 1,189 records · Page 66Linked to original sources
PubMed1993

Awareness and recall during general anesthesia. Facts and feelings.

BACKGROUND: Experiences of awareness and recall during general anesthesia can be most distressing for patients. To obtain relevant information, the authors systematically interviewed patients in whom awareness during surgery had occurred, and questioned them about their experiences. METHODS: Twenty-six patients, referred by colleagues, described the facts and feelings they had experienced during the period of awareness, and whether these had had any consequences. Available anesthetic records were independently judged by three experienced anesthesiologists for relevant parameters. RESULTS: Auditory perception and the sensation of paralysis were most frequently mentioned, followed by the sensation of pain. Patients' feelings were mostly related to anxiety, panic, powerlessness, and helplessness. Eighteen patients (70%) experienced unpleasant aftereffects, including sleep disturbances, dreams and nightmares, and flashbacks and anxiety during the day. Only nine patients (35%) had informed their anesthesiologists about what had taken place. Twelve anesthetic records were assessed. In three, the occurrence of awareness had been indicated, while, in a fourth, it was noted that an amnesic drug had been given at a moment of increased blood pressure. Experienced anesthesiologists were unable to reliably distinguish awareness cases from matched controls when judging the records. CONCLUSIONS: Details recalled from the period of awareness correspond with data from the literature. The anesthesiologist's role in discussing, and dealing with, traumatic experiences related to anesthesia may be of great importance. The hand-written anesthetic record is of limited value in retrospectively explaining why awareness and recall have occurred.

Adult↗
PubMed2005

The inheritance of intermediate phenotypes for schizophrenia.

PURPOSE OF REVIEW: While schizophrenia is substantially heritable, the mode of inheritance is complex, involving numerous genes of small effect and a non-trivial environmental component. The 'endophenotype' approach is an alternative method for measuring phenotypic variation that may facilitate the identification of susceptibility genes in the context of complexly inherited traits. Here we review recent studies applying this method to measures of brain structure, physiology, and function in samples of schizophrenia patients and their non-ill first-degree relatives (siblings and co-twins). RECENT FINDINGS: The results suggest that there are multiple heritable dimensions of central nervous system pathology in schizophrenia, including disturbances in the structure and functioning of frontal lobe systems involved in working memory and executive processes, temporal lobe systems involved in episodic memory, auditory perception, and language processing, and cortical and sub-cortical systems mediating smooth pursuit eye movements and sensorimotor gating. A number of genetic loci that are suspected to play a role in predisposing to schizophrenia, including the DISC1, COMT, neuregulin, dysbindin, and alpha-7 nicotinic receptor genes, appear to affect quantitative variation on one or more of these indicators. SUMMARY: Future work is encouraged to address whether each of these neural system dysfunctions are under the influence of a partially distinct set of genes, to elucidate the manner in which multiple genes may coalesce in determining schizophrenia-promoting dysfunction in each neurobehavioral domain, and to clarify the degree of overlap in these quantitative trait loci-endophenotype relationships with other forms of psychosis, particularly bipolar disorder.

Journal Article↗
PubMed2000

Perceptual auditory gap detection deficits in male BXSB mice with cerebrocortical ectopias.

Underlying impairments in rapid auditory processing may contribute to disrupted phonological processing, which in turn characterizes developmental language impairment (LI). Identification of a neurobiological feature of LI that is associated with auditory deficits would further support this model. Accordingly, we found that adult male rats with induced cortical malformations were impaired in rapid auditory processing. Since 40-60% of BXSB mice exhibit spontaneous focal cerebrocortical ectopias (as seen in dyslexics brains), we assessed auditory gap detection in adult male BXSB mice. Ectopic mice were significantly worse than non-ectopics in detecting a 5 ms silent gap, but were not significantly impaired at longer gap durations (10-100 ms). Our results confirm that focal cortical malformations are associated with impairments in rapid auditory processing.

Animals↗
PubMed2001

Impaired detection of variable duration embedded tones in ectopic NZB/BINJ mice.

Utilizing rodent models, prior research has demonstrated a significant association between focal neocortical malformations (i.e. induced microgyria, molecular layer ectopias), which are histologically similar to those observed in human dyslexic brains, and rate-specific auditory processing deficits as seen in language impaired populations. In the current study, we found that ectopic NZB/BINJ mice exhibit significant impairments in detecting a variable duration 5.6 kHz tone embedded in a 10.5 kHz continuous background, using both acoustic reflex modification and auditory event-related potentials (AERP). The current results add further support to the association between focal cortical malformations and impaired auditory processing, and the notion that these auditory effects may occur regardless of the cortical location of the anomaly.

Acoustic Stimulation↗
PubMed2002

Event-related potentials reflect individual differences in age-invariant auditory skills.

Previous work has found that auditory event-related potentials show maturational changes, with latency and amplitude of late components (N1 and P2) decreasing and increasing with age respectively. Our goal was to test the hypothesis that these changes reflect increased speed of neural processing in the auditory system. Thirty-three listeners, aged 10-50 years, were tested on a frequency discrimination task and an auditory backward recognition masking task. P1 and N1b event-related potential components were measured to tones. The N1b became larger and earlier with age, and the latency of P1 decreased with age. However, thresholds on the behavioural tasks did not change with age. Nevertheless, individual differences in the peak amplitude of N1b were independently related to frequency discrimination and degree of masking. Thus, the relationship that does exist between individual differences in psychoacoustic performance and the auditory N1b reflect a stable characteristic of the individual rather than a maturational change.

Acoustic Stimulation↗
PubMedDate not supplied

Auditory processing limitations in low verbal children: evidence from a two-response dichotic listening task.

Evidence for auditory processing limitations based on the use of two-response consonant-vowel (CV) dichotic listening tasks is reviewed. These studies show that low verbal children obtain fewer trials on which both items are correctly identified (double correct responses). A study is reported comparing a group of good and poor readers on the dichotic CV task. These data are then analyzed in terms of a normative model which attempts to show the effects of overall performance and guessing on double correct responses. It is concluded, in terms of the model, that the poor double correct performance of the poor readers is the direct result of poor auditory processing capacity.

Auditory Perception↗
PubMedDate not supplied

Cochlear summating potential to broadband clicks detected from the human external auditory meatus. A study of subjects with normal hearing for age.

The cochlear summating potential (SP) preceding the auditory nerve compound action potential (AP) was elicited by broadband alternating condensation and rarefaction clicks and recorded by noninvasive electrodes from the external auditory meatus (EAM) of 60 volunteers of both sexes, 12 to 67 years old, who had normal hearing for age. Quantitative data were obtained on: the number of ears displaying measurable SPs; the SP detection level; the SP onset, peak and rise times; the duration of the SP-AP complex; the SP amplitude; and the SP/AP amplitude ratio. Previously unknown relationships were unveiled between the amplitude, but not the temporal, measures of the SP and laterality, sex, age, and audiometrically determined hearing thresholds to 4 to 8 kHz tones. The highest correlations were obtained with these last thresholds, which suggested that receptors in the basal turn of the cochlea played a dominant role in the generation of the EAM-detected SP. To improve on existing techniques for determining abnormal SP elevation, a multiple regression method was devised that utilized sex, age, 4 to 8 kHz hearing thresholds, and AP voltage to establish upper normal limits of SP amplitude for individual subjects and ears.

Acoustic Stimulation↗
PubMedDate not supplied

Functional hearing loss and its relationship to resolved hearing levels.

The nature of functional hearing loss was retrospectively studied with respect to hearing sensitivity after resolution of the nonorganic components in 63 adults with bilateral exaggerated losses (126 ears). The configuration of the functional components (difference between the functional and resolved thresholds) was found to be related to that of the resolved hearing levels. The size of the functional overlay was essentially the same across the audiometric frequency range when the hearing was actually normal or if there was only mild loss. In cases of precipitously sloping high-frequency losses, the magnitude of the functional overlay became dramatically smaller for the impaired frequencies than for lower frequencies where hearing was normal or only mildly impaired. Moderate and severe losses represented a transitional situation, in which the functional components became gradually smaller with increasing frequency. Subjects with different resolved hearing in each ear (e.g., mild loss in one ear and a precipitous loss in the other) demonstrated nonorganic overlays that were consistent with the actual hearing levels for each respective ear. The findings suggest the use of an internalized, loudness level-based anchor by subjects with functional losses: the test signal must sound as loud as the anchor at each frequency in order for an exaggerated threshold response to be volunteered at that respective frequency. The pure-tone audiometric configuration and amount of functional loss at least in bilateral cases is thus consistently accounted for on the basis of known and explainable auditory factors.

Adult↗
PubMedDate not supplied

The effects of chronic hypoxemia on central auditory processing in patients with chronic obstructive pulmonary disease.

This study was designed to discover if chronic hypoxemia produced measurable deficits in subjects' ability to process complex auditory stimuli. In Part I, a group of normal middle-aged subjects and a group of middle-aged subjects with hypoxemia secondary to chronic obstructive pulmonary disease (COPD) were compared with respect to their performance on a central auditory test battery. (The test battery included the Staggered Spondaic Word, Synthetic Sentence Identification with Ipsilateral Competing Message, Synthetic Sentence Identification with Contralateral Competing Message, Memory for Unrelated Words, Memory for Sentences, and a Competing Sentence-Binaural Separation Test). The COPD group's scores were significantly poorer than the normal group's on two of the six tests. The pattern of test scores suggested that chronic hypoxemia produced its principle deficiency at the brain stem level. Part II of this study examined the specific relationships between pulmonary function, arterial blood gas levels, and central auditory performance in this same group of COPD subjects. Statistical analyses revealed that subjects with better pulmonary function and higher arterial blood oxygen levels had better performance on tests of central auditory function.

Aged↗
PubMed1990

Long latency auditory event-related potentials from children with auditory processing disorders.

The purpose of this study was to evaluate auditory event-related potentials, and related long latency components, in children with auditory processing disorders, and to compare these results with a normal group matched for age, intelligence, and gender. Results showed a significant latency increase for the N1, P2, and P3 components in the processing disordered group. Furthermore, the interpeak latency interval P2-P3 was significantly longer in the clinical group. In terms of amplitude measures, only P3 amplitude differed significantly between groups. These results suggest that the long latency potentials may be useful in the assessment of children with processing disorders.

Auditory Perception↗
PubMed1992

The relative contributions of occupational noise and aging in individual cases of hearing loss.

A method is proposed for allocation of hearing handicap between noise and aging in individual cases when noise exposure level and duration are known or can be estimated. A recently published international standard (ISO-1999, 1990) provides statistical models for hearing threshold changes associated with aging and noise exposure. When an individual's hearing threshold level exceeds the sum of the median levels expected given that individual's age, gender, exposure level, and exposure duration, the appropriate allocation depends on the correlation between age-related and noise-induced changes. However, the differences in allocation between assumptions of perfect and absent correlation are small. Only very small errors result from calculating the allocation based on median expectations for noise and aging. In most cases, age-related changes exceed noise-induced changes for the 0.5, 1, 2, and 3 kHz pure-tone average; for men age 65, this is true for all exposure levels below 100 dBA.

Age Factors↗
PubMed1992

High-frequency threshold measurements using insert earphones.

Several recent studies have reported large intersubject variability of high-frequency thresholds measured with circumaural earphones. In the present study, high-frequency thresholds of 10 subjects were measured with circumaural (Sennheiser HD-250) and insert (Etymotic ER-1) earphones at 10, 12, 14, and 16 kHz. Overall results show significantly smaller variability of the threshold data obtained with insert earphones than with circumaural earphones. The above data indicate that insert earphones may be more suitable for high-frequency testing than circumaural earphones.

Acoustic Stimulation↗
PubMed1992

Test/retest reliability of distortion-product and transiently evoked otoacoustic emissions.

Otoacoustic emissions can be used to study cochlear function in an objective and noninvasive manner. These features of emitted responses have stimulated a great deal of investigation into the utility of evoked emissions as clinical tests of hearing. One practical and essential aspect of any clinical measure is the consistency of its result upon repeated testing of the same individual (i.e., its test/retest reliability). The goal of the present work was to conduct a systematic study of the test/retest reliability of the two evoked emission types, the transiently evoked and the distortion-product otoacoustic emissions, that have the greatest promise of becoming clinically useful. Toward this end, the short- and long-term reliabilities of these two response measures were examined in 12 normally hearing adults. The results of these experiments showed that the consistency of both measures of evoked otoacoustic emissions was generally excellent.

Adult↗
PubMed1992

Distortion-product otoacoustic emissions in human newborns and adults.

Cubic distortion-product otoacoustic emissions (DPEs) may have clinical and research applications. We reliably recorded DPEs at some frequencies in all of the normal-hearing human adults and newborns tested. Adult and newborn DPEs were of comparable amplitude, with the exception that a prominent dip between 1 and 3 kHz in the adult data was less evident in the newborn data. DPE amplitude was a linear function of the intensity of the eliciting primary stimuli. The slopes of the linear input-output functions increased with increasing frequency. Except at the highest frequencies assessed, adult input-output functions were steeper than newborn input-output functions.

Acoustic Stimulation↗
PubMed1993

A comparison of auditory brain stem response thresholds and latencies elicited by air- and bone-conducted stimuli.

Auditory brain stem responses (ABRs) were measured for stimuli presented both by air conduction and by bone conduction. Stimuli included clicks and tone bursts at octave frequencies from 250 to 4000 Hz. ABR thresholds were comparable for air- and bone-conducted stimuli. Wave V latencies were longer for bone-conducted stimuli compared to similar responses for air conduction. This effect was evident for both clicks and tone bursts. The fact that these latency differences were largely independent of stimulus spectrum suggests that they are not due to differences between the frequency responses of air and bone conduction transducers. This finding is expected when one considers the interaction between output, threshold, and frequency for both transducer types. These data also suggest that there are inherent differences in transmission by air and bone conduction that affect response latency but are unrelated to the amplitude spectrum in the signal.

Acoustic Stimulation↗
PubMed1993

The effect of forward masker duration, rise/fall time, and integrated pressure on auditory brain stem evoked responses in human newborns and adults.

The effects of duration, rise/fall time, integrated pressure, and intensity of a forward masker on the auditory brain stem evoked response (ABR) were examined in three studies. Keeping peak masker intensity constant, integrated masker pressure was a better predictor of ABR latency prolongation than masker duration or rise/fall time in human newborns. Masker effects varied as a function of masker intensity. Greater ABR latency prolongation was observed for more intense maskers. Furthermore, latency prolongation was observed with increasing masker duration for high-intensity, but not low-intensity maskers. Forward masking had a greater effect on newborn wave V latencies than adult wave V latencies; however, increasing masker duration had similar effects on newborn and adult wave V latencies.

Acoustic Stimulation↗
PubMed1993

The hamster's auditory brain stem response as a function of stimulus intensity, tone burst frequency, and hearing loss.

Young adult hamsters were evaluated for normal variations in the auditory brain stem response (ABR) and for the effects of hearing loss. Normal variations in the ABR's latencies and amplitudes were defined for both click and tone burst stimuli over a broad range of intensities. As stimulus intensity decreased from 100 to 15 dB pe SPL, the ABR latencies were prolonged, the P4-P1 interpeak latencies varied in a complex manner, and amplitudes decreased. As tone burst frequency decreased from 8000 to 4000 and then to 2000 Hz, ABR latencies were prolonged, amplitudes decreased, and thresholds increased. The P4-P1 interpeak latencies were also influenced by tone burst frequency, with the longest interpeak latencies occurring in response to the 2000 Hz tone bursts. Data from two hamsters with hearing loss were compared to the normal data to illustrate how the ABR can be used to describe experimentally induced hearing impairment. Hearing impairment was induced by rearing animals in ambient noise. These animals showed elevated ABR thresholds at all three frequencies and upward displacements in the ABR's latency-intensity profiles.

Acoustic Stimulation↗