1,720,969 research outputs found

    Post-processing analysis of transient-evoked otoacoustic emissions to detect 4 kHz-notch hearing impairment--a pilot study.

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    BACKGROUND: To identify a parameter to distinguish normal hearing from hearing impairment in the early stages. The parameter was obtained from transient-evoked otoacoustic emissions (TEOAEs), overcoming the limitations of the usually adopted waveform descriptive parameters which may fail in standard clinical screenings. MATERIAL/METHODS: Audiometric examinations and TEOAE analysis were conducted on 15 normal ears and on 14 hearing-impaired ears that exhibited an audiometric notch around 4 kHz. TEOAE signals were analyzed through a multivariate technique to filter out the individual variability and to highlight the dynamic structure of the signals. The new parameter (named radius 2-dimension--RAD2D) was defined and evaluated for simulated TEOAE signals modeling a different amount of hearing impairment. RESULTS: Audiometric examinations indicated 14 ears as impaired-hearing (IH), while the TEOAE ILO92 whole reproducibility parameter (WWR) indicated as IH 7 signals out of 14 (50%). The proposed new parameter indicated as IH 9 signals out of 14 (64%), reducing the number of false negative cases of WWR. CONCLUSIONS: In this preliminary study there is evidence that the new parameter RAD2D defines the topology and the quantification of the damage in the inner ear. The proposed protocol can be useful in hearing screenings to identify hearing impairments much earlier than conventional pure tone audiometry and TEOAE pass/fail test

    Enhancing plasticity mechanisms in the mouse motor cortex by anodal transcranial direct-current stimulation: the contribution of nitric oxide signaling

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    Consistent body of evidence shows that transcranial direct-current stimulation (tDCS) over the primary motor cortex (M1) facilitates motor learning and promotes recovery after stroke. However, the knowledge of molecular mechanisms behind tDCS effects needs to be deepened for a more rational use of this technique in clinical settings. Here we characterized the effects of anodal tDCS of M1, focusing on its impact on glutamatergic synaptic transmission and plasticity. Mice subjected to tDCS displayed increased long-term potentiation (LTP) and enhanced basal synaptic transmission at layer II/III horizontal connections. They performed better than sham-stimulated mice in the single-pellet reaching task and exhibited increased forelimb strength. Dendritic spine density of layer II/III pyramidal neurons was also increased by tDCS. At molecular level, tDCS enhanced: 1) BDNF expression, 2) phosphorylation of CREB, CaMKII, and GluA1, and 3) S-nitrosylation of GluA1 and HDAC2. Blockade of nitric oxide synthesis by L-NAME prevented the tDCS-induced enhancement of GluA1 phosphorylation at Ser831 and BDNF levels, as well as of miniature excitatory postsynaptic current (mEPSC) frequency, LTP and reaching performance. Collectively, these findings demonstrate that anodal tDCS engages plasticity mechanisms in the M1 and highlight a role for nitric oxide (NO) as a novel mediator of tDCS effects
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