Data from: Cortical reorganisation during a 30-week tinnitus treatment program

Subjective tinnitus is characterised by the conscious perception of a phantom sound. Previous studies have shown that individuals with chronic tinnitus have disrupted sound-evoked cortical tonotopic maps, time-shifted evoked auditory responses, and altered oscillatory cortical activity. The main objectives of this study were to: (i) compare sound-evoked brain responses and cortical tonotopic maps in individuals with bilateral tinnitus and those without tinnitus; and (ii) investigate whether changes in these sound-evoked responses occur with amelioration of the tinnitus percept during a 30-week tinnitus treatment program. Magnetoencephalography (MEG) recordings of 12 bilateral tinnitus participants and 10 control normal-hearing subjects reporting no tinnitus were recorded at baseline, using 500 Hz, 1000 Hz, 2000 Hz, and 4000 Hz tones presented monaurally at 70 dBSPL through insert tube phones. For the tinnitus participants, MEG recordings were obtained at 5-, 10-, 20- and 30- week time points during tinnitus treatment. Results for the 500 Hz and 1000 Hz sources (where hearing thresholds were within normal limits for all participants) showed that the tinnitus participants had a significantly larger and more anteriorly located source strengths when compared to the non-tinnitus participants. During the 30-week tinnitus treatment, the participants’ 500 Hz and 1000 Hz source strengths remained higher than the non-tinnitus participants; however, the source locations shifted towards the direction recorded from the non-tinnitus control group. Further, in the left hemisphere, there was a time-shifted association between the trajectory of change of the individual’s objective (source strength and anterior-posterior source location) and subjective measures (using tinnitus reaction questionnaire, TRQ). The differences in source strength between the two groups suggest that individuals with tinnitus have enhanced central gain which is not significantly influenced by the tinnitus treatment, and may result from the hearing loss per se. On the other hand, the shifts in the tonotopic map towards the non-tinnitus participants’ source location suggests that the tinnitus treatment might reduce the disruptions in the map, presumably produced by the tinnitus percept directly or indirectly. Further, the similarity in the trajectory of change across the objective and subjective parameters after time-shifting the perceptual changes by 5 weeks suggests that during or following treatment, perceptual changes in the tinnitus percept may precede neurophysiological changes. Subgroup analyses conducted by magnitude of hearing loss suggest that there were no differences in the 500 Hz and 1000 Hz source strength amplitudes for the mild-moderate compared with the mild-severe hearing loss subgroup, although the mean source strength was consistently higher for the mild-severe subgroup. Further, the mild-severe subgroup had 500 Hz and 1000 Hz source locations located more anteriorly (i.e., more disrupted compared to the control group) compared to the mild-moderate group, although this was trending towards significance only for the 500Hz left hemisphere source. While the small numbers of participants within the subgroup analyses reduce the statistical power, this study suggests that those with greater magnitudes of hearing loss show greater cortical disruptions with tinnitus and that tinnitus treatment appears to reduce the tonotopic map disruptions but not the source strength (or central gain).

主观性耳鸣（Subjective tinnitus）以个体有意识地感知到幻声为特征。既往研究证实，慢性耳鸣患者存在声音诱发的皮层音调拓扑图（cortical tonotopic maps）紊乱、听觉诱发电位时程偏移及皮层振荡活动异常。
本研究的核心目标为：（1）对比双侧耳鸣患者与无耳鸣对照人群的声音诱发性脑反应及皮层音调拓扑图；（2）探究在为期30周的耳鸣干预疗程中，随着耳鸣感知的改善，上述声音诱发性反应是否会发生相应改变。
本研究采集了12名双侧耳鸣受试者与10名无耳鸣、听力正常的对照受试者的脑磁图（Magnetoencephalography, MEG）数据：基线状态下，通过插入式耳机以70 dBSPL单耳呈现500 Hz、1000 Hz、2000 Hz及4000 Hz纯音。针对耳鸣受试者，我们分别在干预疗程的第5、10、20及30周采集其MEG数据。
针对所有受试者听力阈值均处于正常范围的500 Hz与1000 Hz刺激，结果显示：相较于无耳鸣对照组，耳鸣受试者的源强度显著更高，且源位置更靠前。在30周的耳鸣干预过程中，耳鸣受试者的500 Hz与1000 Hz源强度仍高于对照组，但源位置逐渐向对照组的源位置偏移。
进一步分析发现，在左侧半球中，个体客观指标（源强度与源位置的前后维度）的变化轨迹与主观指标（采用耳鸣反应问卷（tinnitus reaction questionnaire, TRQ）进行评估）的变化轨迹存在时程偏移关联。
两组间的源强度差异提示，耳鸣患者存在增强的中枢增益（central gain），该增益未受耳鸣干预的显著影响，其成因或与听力损失本身相关。另一方面，音调拓扑图向对照组源位置偏移的结果表明，耳鸣干预或可减轻由耳鸣感知直接或间接引发的皮层拓扑图紊乱。
此外，在将感知变化的时程滞后5周后，客观与主观参数的变化轨迹呈现出高度相似性，这提示在干预期间或干预结束后，耳鸣感知的主观变化可能先于神经生理变化发生。
亚组分析按照听力损失程度进行分层，结果显示：轻中度听力损失亚组与重度听力损失亚组间，500 Hz与1000 Hz的源强度振幅无显著差异，但重度听力损失亚组的平均源强度始终更高。同时，相较于轻中度亚组，重度听力损失亚组的500 Hz与1000 Hz源位置更靠前（即与对照组相比紊乱程度更显著），不过该差异仅在500 Hz左侧半球源中接近统计学显著性。
尽管亚组分析的受试者数量较少导致统计效力有限，但本研究表明：听力损失程度更严重的耳鸣患者皮层紊乱程度更高，且耳鸣干预似乎可减轻音调拓扑图紊乱，但无法改变源强度（或中枢增益）。