There is a strong genetic contribution to children's language and literacy impairments. The aim of this study was to determine which aspects of the phenotype are familial by comparing 34 parents of probands with language/literacy impairments and 33 parents of typically developing probands. The parents responded to questionnaires regarding previous history for language/reading impairment and participated in psychometric testing. The psychometric test battery consisted of tests assessing nonverbal IQ, short-term memory, articulation, receptive grammar, reading abilities and spelling. Self-report measures demonstrated a higher prevalence of language and literacy impairments in parents of affected probands (32%) compared with parents of unaffected probands (6%). The two groups of parents differed significantly in their performance on the non-word repetition, oromotor and digit span tasks. Non-word repetition gave the best discrimination between the parent groups even when the data from the parents who actually were impaired as ascertained by direct testing or self-report were removed from the analyses. This suggests that non-word repetition serves as a marker of a family risk for language impairment. The paper concludes with a discussion of issues associated with ascertainment of specific language impairment (SLI).

The mammalianauditorysystemincludesabrainstem-mediatedefferentpathwayfromthesuperiorolivarycomplexbywayofthemedialolivocochlear system,whichreducesthecochlearresponsetosound (WarrandGuinan,1979;Libermanetal.,1996).Thehumanmedialolivocochlearresponsehasan onsetdelayofbetween25and40msandriseanddecayconstantsintheregionof280and160ms,respectively(BackusandGuinan,2006).Physiological studies with nonhuman mammals indicate that onset and decay characteristics of efferent activation are dependent on the temporal and level characteristics of the auditory stimulus (Bacon and Smith, 1991; Guinan and Stankovic, 1996). This study uses a novel psychoacoustical masking technique usingaprecursorsoundtoobtainameasureoftheefferenteffectinhumans.Thistechniqueavoidsconfoundscurrentlyassociatedwithotherpsychoacousticalmeasures.Bothtemporalandleveldependencyoftheefferenteffectwasmeasured,providingacomprehensivemeasureoftheeffectofhuman auditoryefferentsoncochleargainandcompression.Resultsindicatethataprecursor(Ͼ20dBSPL)inducedefferentactivation,resultinginadecrease in both maximum gain and maximum compression, with linearization of the compressive function for input sound levels between 50 and 70 dB SPL. Estimatedgaindecreasedasprecursorlevelincreased,andincreasedasthesilentintervalbetweentheprecursorandcombinedmasker-signalstimulus increased, consistent with a decay of the efferent effect. Human auditory efferent activation linearizes the cochlear response for mid-level sounds while reducing maximum gain.

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Forward-masked psychophysical tuning curves were obtained using a fixed, low-level signal at a frequency of 4 kHz, and masker frequencies of 2.0, 2.5, 3.0, 3.5, 3.75, 4.0, 4.25, 4.5, 4.75, 5.0, and 5.5 kHz, at masker-signal gaps of 20, 30, 40, 60, 80, and 100 ms. An adaptive two-interval, two alternative forced-choice (21-2AFC) procedure was used to obtain the masker level at threshold. This procedure was repeated with the addition of a 4.75-kHz suppressor at 50 or 60 dB SPL, gated with the masker. Tuning curves were broader, and estimates of compression and gain from derived input/output functions were decreased in the presence of a suppressor as compared to the no-suppressor condition. The results are consistent with physiological results, which show that suppression leads to a broadening of tuning curves and a partial linearization of the midlevel portion of the basilar-membrane input/output function.

Abbreviations: ERB, equivalent rectangular bandwidth; MOC, medial olivocochlear.Running title: Efferent effect on binaural processing Verhey et al. 2ABSTRACT 1 2 Binaural notched-noise experiments indicate a reduced frequency selectivity of the 3 binaural system compared to monaural processing. The present study investigates how 4 auditory efferent activation (via the medial olivocochlear system) affects binaural 5 frequency selectivity in normal-hearing listeners. Thresholds were measured for a 1-6 kHz signal embedded in a diotic notched-noise masker for various notch widths. The 7 signal was either presented in phase (diotic) or in antiphase (dichotic), gated with the 8 noise. Stimulus duration was 25 ms, in order to avoid efferent activation due to the 9 masker or the signal. A bandpass-filtered noise precursor was presented prior to the 10 masker and signal stimuli to activate the efferent system. The silent interval between 11 the precursor and the masker-signal complex was 50 ms. For comparison, thresholds 12 for detectability of the masked signal were also measured in a baseline condition 13 without the precursor and, in addition, without the masker. On average, the results of 14 the baseline condition indicate an effectively wider binaural filter, as expected.