Sexual Behavior in the Human Male

Phantom auditory perception (tinnitus): mechanisms of generation and perception

The ability to determine the location of a sound source is fundamental to hearing. However, auditory space is not represented in any systematic manner on the basilar membrane of the cochlea, the sensory surface of the receptor organ for hearing. Understanding the means by which sensitivity to spatial cues is computed in central neurons can therefore contribute to our understanding of the basic nature of complex neural representations. We review recent evidence concerning the nature of the neural representation of auditory space in the mammalian brain and elaborate on recent advances in the understanding of mammalian subcortical processing of auditory spatial cues that challenge the "textbook" version of sound localization, in particular brain mechanisms contributing to binaural hearing.

Mechanisms of Sound Localization in Mammals

This paper presents a neurophysiological approach to tinnitus and discusses its clinical implications. A hypothesis of discordant damage of inner and outer hair cells systems in tinnitus generation...

A neurophysiological approach to tinnitus: Clinical implications

Otoacoustic emissions (OAEs) of all types are widely assumed to arise by a common mechanism: nonlinear electromechanical distortion within the cochlea. In this view, both stimulus-frequency (SFOAEs) and distortion-product emissions (DPOAEs) arise because nonlinearities in the mechanics act as "sources" of backward-traveling waves. This unified picture is tested by analyzing measurements of emission phase using a simple phenomenological description of the nonlinear re-emission process. The analysis framework is independent of the detailed form of the emission sources and the nonlinearities that produce them. The analysis demonstrates that the common assumption that SFOAEs originate by nonlinear distortion requires that SFOAE phase be essentially independent of frequency, in striking contradiction with experiment. This contradiction implies that evoked otoacoustic emissions arise by two fundamentally different mechanisms within the cochlea. These two mechanisms (linear reflection versus nonlinear distortion) are described and two broad classes of emissions--reflection-source and distortion-source emissions--are distinguished based on the mechanisms of their generation. The implications of this OAE taxonomy for the measurement, interpretation, and clinical use of otoacoustic emissions as noninvasive probes of cochlear function are discussed.

http://web.mit.edu/apg/papers/shera-guinan-taxonomy-JASA99.pdf

Evoked otoacoustic emissions arise by two fundamentally different mechanisms: A taxonomy for mammalian OAEs

The psychoacoustical literature contains multiple reports about small differences in performance depending upon the sex and phase of the menstrual cycle of the subjects. In an attempt to verify these past reports, a large-scale study was implemented. After extensive training, the performance of about 75 listeners was measured on seven common psychoacoustical tasks. For most tasks, the signal was a 3.0-kHz tone. The initial data analyses failed to confirm some past outcomes. Additional analyses, incorporating the limited information available about the racial background of the listeners, did confirm some of the past reports, with the direction and magnitude of the differences often diverging for the White and Non-White listeners. Sex differences and race differences interacted for six of the seven tasks studied. These interactions suggest that racial background needs to be considered when making generalizations about human auditory performance, and when considering failures of reproducibility across studies. Menstrual differences were small, but generally larger for Whites than Non-Whites. Hormonal effects may be responsible for the sex and cycle differences that do exist, and differences in intra-cochlear melanocytes may account for the race differences.

/pdf/differences-in-common-psychoacoustical-tasks-by-sex-57ex21kla4.pdf

Differences in common psychoacoustical tasks by sex, menstrual cycle, and race

Distortion-product otoacoustic emissions (DPOAEs) were weak or absent in about one-third of sheep (Ovis aries) of both sexes tested for otoacoustic emissions (OAEs) even though their click-evoked OAEs (CEOAEs) seemingly were typical of other sheep of the same sex. Various pieces of evidence suggest that the absence of measurable DPOAEs was unlikely to be attributable to anesthetic effects, a poorly located probe tip, a pressure differential between middle and outer ears, season of the year, body position during testing, temperature effects, or previous medical history. Sheep apparently can exhibit a marked dissociation between DPOAEs and CEOAEs. In those sheep having measurable DPOAEs, the DPOAEs were stronger in males than in females, which is the opposite direction of effect from the CEOAEs measured in these same sheep and in humans. In female sheep exposed to higher-than-normal levels of androgens during gestation, the measurable DPOAEs were stronger than in untreated females. Although this also was th...

Dissociation between distortion-product and click-evoked otoacoustic emissions in sheep (Ovis aries)

Attention‐deficit/hyperactivity disorder (ADHD) is generally acknowledged to be more prevalent in males than in females. Further, some precursors to ADHD appear early in life. Together these facts suggest that ADHD may be influenced by androgenic mechanisms operating early in development. This reasoning raises the question of whether the otoacoustic emissions (OAEs) of children with ADHD are masculinized. Click‐evoked OAEs were measured for one click level in 8 boys and 3 girls diagnosed as ADHD/Combined, in 11 males and 5 females diagnosed as ADHD/Inattentive (IA), and in 17 male and 18 female controls. The ages of these samples ranged between 7 and 15. As in adults, the CEOAEs of the control males were weaker than those of the control females. Further, the CEOAEs of the ADHD/IA males were weaker than in the control males (a hypermasculinization) and the CEOAEs of the IA females were weaker than in the female controls (a masculinization). The CEOAEs of the Combined groups were slightly stronger (feminized) than those of the control males and females. One interpretation is that the IA subgroup of ADHD boys and girls (but not the Combined subgroup) was exposed to higher‐than‐normal levels of androgens sometime early in development. [Work supported by NIDCD.]

Otoacoustic emissions measured in children diagnosed with attention‐deficit/hyperactivity disorder

Otoacoustic emissions (OAEs) were measured in Suffolk sheep (Ovis aries), the first ruminant species tested for OAEs to our knowledge Some sheep had been administered testosterone or estradiol during prenatal development, some had been gonadectomized after birth, and some had been allowed to develop normally The click‐evoked otoacoustic emissions (CEOAEs) exhibited by the female control group (N=11) were stronger than those in the male control group (N=15), which is the same direction of effect reported for other mammals, including humans The females administered testosterone prenatally (N=13) had substantially weaker (masculinized) CEOAEs than control females Both outcomes suggest that prenatal exposure to androgens weakens the cochlear amplifiers The CEOAEs of males administered testosterone prenatally (N=5) were not different from those of control males, which is contrary to expectation, but in accord with data from similarly treated rhesus monkeys Seven males (of 24) and seven females (of 34) had no measurable DPOAEs at any frequency or level of primary tones tested, even though all did have normal‐appearing CEOAEs No spontaneous otoacoustic emissions (SOAEs) were found in any ears, a common finding in non‐human species [Supported by NIDCD (DM) and NICHD (TML)]

Otoacoustic emissions in sheep (Ovis aries): Sex differences and prenatal androgen effects

In humans, otoacoustic emissions (OAEs) are stronger in females than in males and stronger in right ears than in left. The physiological bases for these differences are unknown, but several lines of circumstantial evidence suggest that the sex difference is attributable to androgenizing mechanisms operating during prenatal development. Specifically, it appears that exposure to high levels of androgens during prenatal development diminishes the strength of the cochlear amplifiers and thus the strength of the OAEs. Sex and ear differences in OAEs have not been well studied in species other than humans. Accordingly, click‐evoked OAEs and distortion‐product OAEs were measured in nine female and nine male rhesus monkeys. For CEOAEs, but less clearly for DPOAEs, females exhibited significantly stronger OAEs than males. There was no consistent ear difference for either sex for either type of OAE. In order to better study the early components of the CEOAE waveform, a nonlinear procedure [Molenaar et al., Hearing ...

Edward G. Pasanen

Papers

Differences in common psychoacoustical tasks by sex, menstrual cycle, and race

Dissociation between distortion-product and click-evoked otoacoustic emissions in sheep (Ovis aries)

Otoacoustic emissions measured in children diagnosed with attention‐deficit/hyperactivity disorder

Otoacoustic emissions in sheep (Ovis aries): Sex differences and prenatal androgen effects

Otoacoustic emissions measured in rhesus monkeys (Macaca mulatta)