Bidelman Gavin M, Chow Ricky, Noly-Gandon Alix, Ryan Jennifer D, Bell Karen L, Rizzi Rose, Alain Claude
Department of Speech, Language and Hearing Sciences, Indiana University Bloomington, Bloomington, IN, United States.
School of Communication Sciences and Disorders, The University of Memphis, Memphis, TN, United States.
Front Neurosci. 2022 Jul 6;16:884130. doi: 10.3389/fnins.2022.884130. eCollection 2022.
Emerging evidence suggests transcranial direct current stimulation (tDCS) can improve cognitive performance in older adults. Similarly, music listening may improve arousal and stimulate subsequent performance on memory-related tasks. We examined the synergistic effects of tDCS paired with music listening on auditory neurobehavioral measures to investigate causal evidence of short-term plasticity in speech processing among older adults. In a randomized sham-controlled crossover study, we measured how combined anodal tDCS over dorsolateral prefrontal cortex (DLPFC) paired with listening to autobiographically salient music alters neural speech processing in older adults compared to either music listening (sham stimulation) or tDCS alone. EEG assays included both frequency-following responses (FFRs) and auditory event-related potentials (ERPs) to trace neuromodulation-related changes at brainstem and cortical levels. Relative to music without tDCS (sham), we found tDCS alone (without music) modulates the early cortical neural encoding of speech in the time frame of ∼100-150 ms. Whereas tDCS by itself appeared to largely produce suppressive effects (i.e., reducing ERP amplitude), concurrent music with tDCS restored responses to those of the music+sham levels. However, the interpretation of this effect is somewhat ambiguous as this neural modulation could be attributable to a true effect of tDCS or presence/absence music. Still, the combined benefit of tDCS+music (above tDCS alone) was correlated with listeners' education level suggesting the benefit of neurostimulation paired with music might depend on listener demographics. tDCS changes in speech-FFRs were not observed with DLPFC stimulation. Improvements in working memory pre to post session were also associated with better speech-in-noise listening skills. Our findings provide new causal evidence that combined tDCS+music relative to tDCS-alone (i) modulates the early (100-150 ms) cortical encoding of speech and (ii) improves working memory, a cognitive skill which may indirectly bolster noise-degraded speech perception in older listeners.
新出现的证据表明，经颅直流电刺激（tDCS）可以改善老年人的认知表现。同样，听音乐可能会提高唤醒水平，并刺激随后在与记忆相关任务上的表现。我们研究了tDCS与听音乐相结合对听觉神经行为指标的协同作用，以调查老年人言语加工中短期可塑性的因果证据。在一项随机假对照交叉研究中，我们测量了与单独听音乐（假刺激）或单独进行tDCS相比，在背外侧前额叶皮层（DLPFC）进行阳极tDCS与听具有自传体意义的音乐相结合，如何改变老年人的神经言语加工。脑电图检测包括频率跟随反应（FFR）和听觉事件相关电位（ERP），以追踪脑干和皮层水平与神经调节相关的变化。相对于没有tDCS的音乐（假刺激），我们发现单独的tDCS（不听音乐）在约100-150毫秒的时间范围内调节言语的早期皮层神经编码。虽然单独的tDCS似乎在很大程度上产生抑制作用（即降低ERP振幅），但tDCS与音乐同时作用时，反应恢复到音乐+假刺激水平。然而，这种效应的解释有些模糊，因为这种神经调节可能归因于tDCS的真实效应或音乐的存在与否。尽管如此，tDCS+音乐（高于单独的tDCS）的综合益处与听众的教育水平相关，这表明神经刺激与音乐相结合的益处可能取决于听众的人口统计学特征。在DLPFC刺激下未观察到言语FFR的tDCS变化。从会话前到会话后工作记忆的改善也与更好的噪声中言语聆听技能相关。我们的研究结果提供了新的因果证据，表明与单独的tDCS相比，tDCS+音乐相结合（i）调节言语的早期（100-150毫秒）皮层编码，（ii）改善工作记忆，这是一种认知技能，可能间接增强老年听众中受噪声干扰的言语感知。
