Research ArticleTINNITUS

Auditory-somatosensory bimodal stimulation desynchronizes brain circuitry to reduce tinnitus in guinea pigs and humans

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Science Translational Medicine  03 Jan 2018:
Vol. 10, Issue 422, eaal3175
DOI: 10.1126/scitranslmed.aal3175
  • Fig. 1 STDP regulates synchrony in fusiform cells of the guinea pig DCN.

    (A) Spontaneous activity (SA) was recorded across the fusiform cell (FC) population in 25 guinea pigs for 150 s, followed by 60 s (5 Hz) of bimodal stimulation (BIS) with bimodal intervals (BI) from −20 to +20 ms. SA was recorded again 15 min after BIS for 150 s. (B) Synchrony was assessed by cross-correlations (x-corr) of spikes in FC pairs (FC1 and FC2). SA of FCs shows Poisson distributions in interspike interval histograms (ISIHs). Synchronous unit pairs are defined by threshold cross-correlation coefficients (x-corr coef) of 4 SD (dashed line). (C) In one representative FC unit pair, a BI of −10 ms (auditory preceding somatosensory stimulus by 10 ms; pink) reduced the peak x-corr coef (top), whereas a BI of 10 ms (somatosensory preceding auditory stimulus by 10 ms; blue) increased the peak x-corr coef 15 min after BIS (bottom). (D) Changes in peak x-corr coef for the FC unit pair in (C) are plotted as a function of BI (learning rule). (E) In a different FC unit pair, a BI of −10 ms increased peak x-corr coef (top), whereas a BI of 10 ms decreased peak x-corr coef 15 min after BIS (bottom). (F) For the FC unit pair in (E), changes in x-corr coef after BIS were opposite to that for the FC unit pair in (D).

  • Fig. 2 STDP shifts toward LTP in guinea pigs with tinnitus.

    (A) Increased mean cross-correlation coefficient (x-corr; weighted by the proportion of synchronous unit pairs) and (B) increased mean spontaneous firing rate (SA) compared to the normal-hearing (N) and exposed-but-no-tinnitus (ENT) groups of animals. One-way analysis of variance (ANOVA), *P < 0.05; data are mean ± SEM. Spontaneous firing rates for the N, ENT, and ET (exposed tinnitus) groups were 116, 93, and 167 unit pairs for x-corr and 106, 387, and 478 units, respectively. (C and D) A shift in the proportion of learning rules toward Hebbian-like (Heb; x axis) and long-term potentiation (LTP) (y axis) in the ET group for (C) synchrony and (D) SA. aHeb, anti-Hebbian. (E and F) Long-term depression (LTD)–LTP index: total magnitude of LTP, that is, green area under the curve relative to total magnitude of LTD, that is, blue area above the curve of learning rules (E, inset), is increased in the ET group for (E) synchrony and (F) SA.

  • Fig. 3 Targeted bimodal stimulation suppresses synchrony and spontaneous activity in fusiform cells of guinea pigs.

    (A) Probability of synchrony (x-corr) or SA suppression as a function of bimodal interval. Probability is computed by proportion of unit pairs (total n = 159) or units (n = 251) showing decreased x-corr or SA at a given bimodal interval. A probability of 0.5 indicates an equal number of units showing increased or decreased x-corr or SA. The highest probability of suppression occurs for the −10- and −5-ms intervals [error bar, confidence interval (CI) for binomial proportion]. The −5-ms interval was chosen for the treatment. (B) The distributions of suppression versus enhancement of synchrony are compared for the −5-ms bimodal interval, unimodal somatosensory (uni. som), or unimodal auditory stimulation (uni. aud). The bimodal stimulus clearly suppressed synchrony, whereas the unimodal stimuli showed little deviation from zero. (C) Similar to synchrony, the bimodal stimulus suppressed SA, whereas the unimodal stimulus showed little deviation from zero (bar = 2% bin; shaded curve is fitted by Spline Interpolant).

  • Fig. 4 LTD-induction reduces synchrony and spontaneous activity and reduces tinnitus in guinea pigs.

    (A) Four representative animals (one from each group) showed increased normalized startles (norm. startle) after noise exposure [from pre-exposure (pre-exp) to post-exposure (post-exp)] indicating tinnitus (left ordinate), quantified as the TI (right ordinate). After LTD induction by application of a bimodal auditory-somatosensory stimulus to the fusiform cells (ET-treat), there was a reduction in TI in the treated animal (ET-treat). Sham-treated (ET-sham; sedative only), auditory stimulus–only (ET-audio), and somatosensory stimulus–only (ET-som) animals showed either no reduction in TI or worsened TI. (B) Mean TI was significantly reduced in the ET-treat group at the treated frequency (on-freq; 8 kHz) but not at the untreated frequencies (off-freq; 12 and 16 kHz). TI was not significantly reduced in the ET-sham, ET-audio, or ET-som groups. Pink horizontal bar indicates the 95% CI for the ET-sham group. (C) The weighted mean cross-correlation coefficient (x-corr) for FCs (at best frequencies within the TI bandwidth) is plotted as a function of ΔTI (116, 36, 35, and 106 unit pairs for the ET-sham, ET-audio, ET-som, and ET-treat groups, respectively). Gray area indicates the range of x-corr for nonexposed animals. Reduction in synchrony significantly correlated with TI reduction. (D) SA plotted as a function of ΔTI (446, 204, 202, and 696 units). Reduction in SA significantly correlated with TI reduction. Data are mean ± SEM.

  • Fig. 5 Outline of crossover design for the human study.

    Subjects were randomly assigned to group 1, in which the bimodal treatment was presented first, or group 2, in which the sham treatment was presented first. After 4 weeks of 30 min/day of the treatment, there was a 4-week washout period. Thereafter, subjects crossed over to receive the treatment that they had not yet received for 4 more weeks. This was followed by a second, 4-week washout period. Loudness and Tinnitus Functional Index (TFI) assessments were done weekly in the clinic.

  • Fig. 6 Bimodal treatment results in reduced tinnitus loudness and reduced TFI scores in human patients.

    (A) Mean loudness by group. Group 1 (n = 10) received the active treatment first; group 2 (n = 10) received the sham treatment first. Loudness was assessed using the interactive software TinnTester, in which subjects match their tinnitus loudness and spectrum to an externally presented sound (see Materials and Methods). (B) Mean changes (normalized to baseline) in loudness matching for each condition. (C) Mean TFI changes (relative to baseline) for groups 1 and 2. (D) Mean changes (relative to baseline) in TFI scores. Error bars are SEM. dB SPL, decibels sound pressure level.

Supplementary Materials

  • www.sciencetranslationalmedicine.org/cgi/content/full/10/422/eaal3175/DC1

    Materials and Methods

    Fig. S1. Development of STDP in the fusiform cell circuit.

    Fig. S2. The experimental timeline for the animal study.

    Fig. S3. Noise exposure produces only temporary threshold and suprathreshold shifts.

    Fig. S4. GPIAS behavioral assessment of tinnitus in guinea pigs.

    Fig. S5. Human treatment groups had similar hearing thresholds.

    Fig. S6. Reduction in tinnitus loudness in humans correlates with reductions in TFI.

    Fig. S7. Tinnitus modulation maneuver checklist.

    Table S1. Distribution of STDP learning rule type across unit/unit pairs in guinea pigs.

    Table S2. Subject demographics.

    Table S3. Correlations between changes in loudness and changes in TFI subscore.

    References (5970)

  • Supplementary Material for:

    Auditory-somatosensory bimodal stimulation desynchronizes brain circuitry to reduce tinnitus in guinea pigs and humans

    Kendra L. Marks, David T. Martel, Calvin Wu, Gregory J. Basura, Larry E. Roberts, Kara C. Schvartz-Leyzac, Susan E. Shore*

    *Corresponding author. Email: sushore{at}umich.edu

    Published 3 January 2018, Sci. Transl. Med. 10, eaal3175 (2018)
    DOI: 10.1126/scitranslmed.aal3175

    This PDF file includes:

    • Materials and Methods
    • Fig. S1. Development of STDP in the fusiform cell circuit.
    • Fig. S2. The experimental timeline for the animal study.
    • Fig. S3. Noise exposure produces only temporary threshold and suprathreshold shifts.
    • Fig. S4. GPIAS behavioral assessment of tinnitus in guinea pigs.
    • Fig. S5. Human treatment groups had similar hearing thresholds.
    • Fig. S6. Reduction in tinnitus loudness in humans correlates with reductions in TFI.
    • Fig. S7. Tinnitus modulation maneuver checklist.
    • Table S1. Distribution of STDP learning rule type across unit/unit pairs in guinea pigs.
    • Table S2. Subject demographics.
    • Table S3. Correlations between changes in loudness and changes in TFI subscore.
    • References (5970)

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