Neurobiology of Social Communication, Department of Otolaryngology, Head and Neck Surgery, Hearing Research Centre, University of Tübingen Medical Center, Elfriede-Aulhorn-Str. 5, 72076 Tübingen, Germany; Werner Reichardt Centre for Integrative Neuroscience, University of Tübingen, Otfried-Müller-Str. 25, 72076 Tübingen, Germany; Graduate School of Neural & Behavioural Sciences - International Max Planck Research School, University of Tübingen, Österberg-Str. 3, 72074 Tübingen, Germany.
Neurobiology of Social Communication, Department of Otolaryngology, Head and Neck Surgery, Hearing Research Centre, University of Tübingen Medical Center, Elfriede-Aulhorn-Str. 5, 72076 Tübingen, Germany; Werner Reichardt Centre for Integrative Neuroscience, University of Tübingen, Otfried-Müller-Str. 25, 72076 Tübingen, Germany.
Curr Biol. 2020 Nov 2;30(21):4276-4283.e3. doi: 10.1016/j.cub.2020.08.019. Epub 2020 Sep 3.
Human speech shares a 3-8-Hz theta rhythm across all languages [1-3]. According to the frame/content theory of speech evolution, this rhythm corresponds to syllabic rates derived from natural mandibular-associated oscillations [4]. The underlying pattern originates from oscillatory movements of articulatory muscles [4, 5] tightly linked to periodic vocal fold vibrations [4, 6, 7]. Such phono-articulatory rhythms have been proposed as one of the crucial preadaptations for human speech evolution [3, 8, 9]. However, the evolutionary link in phono-articulatory rhythmicity between vertebrate vocalization and human speech remains unclear. From the phonatory perspective, theta oscillations might be phylogenetically preserved throughout all vertebrate clades [10-12]. From the articulatory perspective, theta oscillations are present in non-vocal lip smacking [1, 13, 14], teeth chattering [15], vocal lip smacking [16], and clicks and faux-speech [17] in non-human primates, potential evolutionary precursors for speech rhythmicity [1, 13]. Notably, a universal phono-articulatory rhythmicity similar to that in human speech is considered to be absent in non-human primate vocalizations, typically produced with sound modulations lacking concomitant articulatory movements [1, 9, 18]. Here, we challenge this view by investigating the coupling of phonatory and articulatory systems in marmoset vocalizations. Using quantitative measures of acoustic call structure, e.g., amplitude envelope, and call-associated articulatory movements, i.e., inter-lip distance, we show that marmosets display speech-like bi-motor rhythmicity. These oscillations are synchronized and phase locked at theta rhythms. Our findings suggest that oscillatory rhythms underlying speech production evolved early in the primate lineage, identifying marmosets as a suitable animal model to decipher the evolutionary and neural basis of coupled phono-articulatory movements.
人类语言在所有语言中共享 3-8-Hz 的θ节律[1-3]。根据言语进化的框架/内容理论，这种节律对应于从下颌相关运动中衍生出的音节率[4]。这种底层模式源于发音肌肉的振荡运动[4,5]，与周期性声带振动紧密相关[4,6,7]。这种语音运动节律被提出是人类言语进化的关键预适应之一[3,8,9]。然而，脊椎动物发声与人类言语之间的语音运动节律的进化联系尚不清楚。从发音的角度来看，θ振荡可能在所有脊椎动物谱系中都经历了系统发育的保存[10-12]。从发音的角度来看，θ振荡存在于非发声的唇动[1,13,14]、牙齿颤抖[15]、发声的唇动[16]和非人类灵长类动物的喀哒声和假言语[17]中，这些都是言语节律的潜在进化前体[1,13]。值得注意的是，类似于人类言语的普遍的语音运动节律被认为在非人类灵长类动物的发声中不存在，通常发声伴随着缺乏伴随发音运动的声音调制[1,9,18]。在这里，我们通过研究狨猴发声中的发音和发音系统的耦合来挑战这一观点。我们使用声学呼叫结构的定量测量，例如幅度包络，以及与呼叫相关的发音运动，即唇间距离，来展示狨猴表现出类似于言语的双运动节律性。这些振荡在θ节律下同步和相位锁定。我们的发现表明，言语产生的基础振荡节律在灵长类动物的谱系中很早就进化了，确定狨猴是一个合适的动物模型，用于破译耦合的语音运动的进化和神经基础。
