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Distortion-product emissions and auditory sensitivity in human ears with normal hearing and cochlear hearing loss. 总被引:2,自引:0,他引:2
Distortion product emissions (DPEs) at 2f1-f2 frequencies were measured in 53 human ears; 21 of them exhibited cochlear hearing loss. DPEs were obtained as a function of stimulus level (DPE growth curves) at seven frequency regions between 707 Hz and 5656 Hz. Several distinctly different shapes or patterns of DPE growth curves were observed. These included single-segment monotonic growth curves with and without saturation at moderate and high stimulus levels, diphasic growth curves with nulls at moderate stimulus levels, and non-monotonic growth curves with negative slopes at high stimulus levels. Low-level, irregularly shaped segments were more frequent in normal-hearing ears, suggestive of normal low-level active nonlinearities from the outer-hair-cell subsystem. High-level, steeply sloped segments were frequent in hearing-impaired ears, suggestive of residual nonlinearities from a cochlear partition without functional outer hair cells. The stimulus level at which the DPE could just be distinguished from the noise floor, the DPE detection threshold, demonstrated moderate positive correlations (r's from 0.50 to 0.81) with auditory thresholds when all ears, both normal and impaired, were considered together. Those correlations were not strong enough to quantitatively predict auditory thresholds with any great accuracy. However, DPE thresholds were able to predict abnormal auditory sensitivity with some precision. DPE thresholds correctly predicted abnormal auditory sensitivity 79% of the time in the present study, and up to 96% of the time in previous studies. These results suggest that DPE thresholds may prove useful for hearing screening in cases where cooperation from the subject is limited or where corroboration of cochlear hearing loss is required. Different patterns of DPE growth curves suggest underlying micro-mechanical differences between ears, but the differential diagnostic value of those patterns remains to be determined. 相似文献
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Cognitive learning during surgical residency. A model for curriculum evaluation. 总被引:1,自引:0,他引:1
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The program summary of the American Board of Surgery In-Service Training Exam (ABSITE) can be used to quantitate cognitive learning during a surgical residency and to identify areas of curricular weakness in a residency program. Knowledge on each question is categorized as high (known) or low (unknown) depending on the percentage of residents who answered correctly. Knowledge of Level 1 (entry) residents is then compared with Level 5 (exit) residents. Each ABSITE question can thus be categorized on entry versus exit as known-known, unknown-unknown, unknown-known, and known-unknown. Only about half of unknown knowledge on entry appears to become known on exit. Very little knowledge known on entry becomes unknown on exit. Weaknesses in specific subject areas can be readily identified by ranking questions according to the number of exiting residents who answer incorrectly. Use of this technique to quantitate cognitive learning in a residency program may allow objective assessment of changes in curriculum. 相似文献
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Miranda Jeanne James J. Gross Jacqueline B. Persons Judy Hahn 《Cognitive therapy and research》1998,22(4):363-376
Cognitive theory holds that dysfunctionalattitudes are important risk factors for depression.Critics have questioned this view, noting that, althoughdysfunctional attitudes are elevated in depression, they are not evident in vulnerable individualswho are asymptomatic. To deal with this criticism,Miranda and Persons (1988) have advanced the mood-statedependent hypothesis, which suggests that cognitive vulnerability factors are indeed present invulnerable individuals, but remain dormant untilactivated by negative mood. To test this hypothesis, 33women with and 67 women without histories of depression reported dysfunctional attitudes before andafter a film negative mood induction. As predicted,vulnerable subjects who reported increased negative moodreported increased dysfunctional attitudes.Unexpectedly, nonvulnerable subjects who reported increasednegative mood reported decreased dysfunctionalattitudes. These findings support the mood-statedependent hypothesis, and suggest that a deficit in theability to regulate negative emotions may be animportant feature of vulnerability todepression. 相似文献
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Immunization reverses memory deficits without reducing brain Abeta burden in Alzheimer's disease model 总被引:13,自引:0,他引:13
Dodart JC Bales KR Gannon KS Greene SJ DeMattos RB Mathis C DeLong CA Wu S Wu X Holtzman DM Paul SM 《Nature neuroscience》2002,5(5):452-457
We have previously shown that chronic treatment with the monoclonal antibody m266, which is specific for amyloid beta-peptide (Abeta), increases plasma concentrations of Abeta and reduces Abeta burden in the PDAPP transgenic mouse model of Alzheimer's disease (AD). We now report that administration of m266 to PDAPP mice can rapidly reverse memory deficits in both an object recognition task and a holeboard learning and memory task, but without altering brain Abeta burden. We also found that an Abeta/antibody complex was present in both the plasma and the cerebrospinal fluid of m266-treated mice. Our data indicate that passive immunization with this anti-Abeta monoclonal antibody can very rapidly reverse memory impairment in certain learning and memory tasks in the PDAPP mouse model of AD, owing perhaps to enhanced peripheral clearance and (or) sequestration of a soluble brain Abeta species. 相似文献
8.
Allison J Geddes Heather E Angka Kimberley A Davies Boris Kablar 《Developmental dynamics》2006,235(8):2175-2184
The aim of our study was to assess the ability of brain-derived neurotrophic factor (BDNF) to rescue motor and sensory neurons from programmed cell death. It is clearly demonstrated that the administration of a single injection of a putative neurotrophic factor to mouse embryos in utero on embryonic day (E) 14.5 is sufficient to significantly reduce the death of motor neurons when assessed on E18.5. However, the trophic requirements of somatic neurons have not been unequivocally determined in a mammalian species in vivo. Indeed, the unexpectedly high numbers of surviving neurons observed in neurotrophin and tyrosine kinase receptor knockout mice are probably the consequence of functional redundancy between the neurotrophins and their receptors. We studied spinal cord and facial motor nucleus neurons and proprioceptive neurons in the dorsal root ganglion and mesencephalic nucleus. The action of BDNF was assessed in wild-type fetuses to gain insight into its ability to rescue neurons from naturally occurring programmed cell death. In addition, we used Myf5(-/-):MyoD(-/-) embryos, which completely lack skeletal musculature, to assess the ability of BDNF to rescue neurons from excessively occurring programmed cell death. We found that BDNF differentially rescued neurons from naturally vs. excessively occurring cell death and that its ability to do so varied among neuronal subpopulations. 相似文献
9.
Background
Relatives of BRCA1 and BRCA2 mutation carriers have long been proposed by epidemiological studies to have an increased risk of developing prostate cancer. In the Ashkenazi Jewish (AJ) population, the existence of 3 frequent founder mutations, 185delAG and 5382insC in BRCA1 and 6174delT in BRCA2 greatly facilitates screening for carriers. 相似文献10.
Three theories about the cognitive processes underlying symptoms of formal thought disorder in psychiatric inpatients were tested. Chapman and Chapman's "excessive yielding to normal bias" theory and a response competition theory were tested by using two ambiguity tasks. Chapman and Chapman's bias theory predicts a smaller ambiguity effect for thought-disordered patients; a response competition hypothesis predicts a larger ambiguity effect. Results showed no difference between thought-disordered and non-thought-disordered patients. To test a distractibility theory of thought disorder, subjects performed a Stroop-type task in which they counted the number of digits (e.g., 3333) or symbols (####) in a set. Thought-disordered patients did show an increased effect of the presence of the digits, and this finding was replicated in a second inpatient sample. Thus, results were consistent with the distractibility theory and with a reformulation of the bias theory, in which the bias shown by thought-disordered patients is not a tendency toward a particular response, but rather toward a particular rule, or set, for responding. 相似文献