The perception of voice gender and identity: a combined behavioural electrophysiological and neuroimaging approach.

我们怎么知道一个声音是男性还是女性的呢？我们如何识别一个人的声音？尽管我们很容易解决这些问题，而且这些能力在我们的日常交流中很重要，但我们对其中涉及的大脑机制知之甚少。该研究旨在通过结合声音合成和脑成像的最新技术来研究我们对声音性别和声音身份的感知。最近的“听觉变形”技术将用于产生一系列自然的合成声音，在一个声音和另一个声音之间逐渐变化。将产生两种类型的morphs，对应于所提出的研究的两部分。在男声和女声之间会产生一种类型的变形（“性别变形”），并将在研究的第一部分中使用，以调查如何感知语音性别。另一种类型的变形将在声音a和声音B之间产生，参与者将熟悉它（“身份变形”），并将在研究的第二部分中使用，以调查我们如何从声音中识别一个人的身份。研究的两部分——第一部分关于性别，第二部分关于身份——将遵循完全相同的计划。在每个部分中，将招募一组正常的成年志愿者——男女各占一半。每个参与者将首先播放变形的合成声音，并将被要求决定每个声音听起来更像男性或女性的声音（第一部分）或更像声音a或声音B（第二部分）。这将允许确定每个参与者在变形上的声音是最“模糊”的，即在一半的试验中被分类为男性，一半的试验为女性（第一部分），或者一半的试验为声音A，一半的试验为声音B（第二部分）。然后，参与者将被播放为变形而绘制的成对声音，要么来自模糊声音的同一侧，要么来自模糊声音的每一侧，并被要求决定这两个声音是相同的还是不同的。我们预计，平均而言，参与者将获得更好的表现，从每一边的模棱两可的声音。这将证明他们以一种“分类的方式”来感知变形，即将其视为两个不同的类别，而不是一个连续体。这种“分类感知”已经被证明适用于不同音节之间的词形变化，或者不同面孔之间的视觉变化，但从未被证明适用于声音的性别或身份。然后将使用两种互补的技术来测量参与者的大脑对合成声音的反应：脑电图（EEG）和功能性磁共振成像（fMRI）。这两种技术将确定参与者大脑的哪些部分对声音性别（第一部分）或声音身份（第二部分）的变化敏感。脑电图和功能磁共振成像的结合将允许在空间（大脑的确切位置）和时间（他们在声音呈现后的确切反应时间）上对这些敏感的大脑区域进行非常精确的表征。重要的是，使用来自变体的合成声音将确保识别的大脑区域对感知到的声音的性别（第一部分）或身份（第二部分）真正敏感，而不仅仅是对声音的物理特征敏感。总的来说，这项研究将增加我们对大脑听觉部分分析声音的方式的理解，使我们能够快速准确地通过听到他/她的声音来提取关于一个人的性别和身份的信息。这很重要，因为我们对大脑功能的这方面知之甚少；在这一大脑研究领域了解得更多，将对我们理解人类大脑中言语和语言是如何进化的，以及如何更好地诊断和治疗对视听交流有不利影响的脑部疾病，如失语症或自闭症，具有重要意义。

How do we know that a voice belongs to a male or a female individual? How can we recognize a person's voice? Despite the apparent ease with which we solve these problems and the importance of these abilities in our everyday communication, little is known on the cerebral mechanisms involved. The proposed research aims to investigate our perception of voice gender and voice identity by combining state-of-the-art techniques in sound synthesis and brain imaging. Recent 'auditory morphing' techniques will be used to generate series of natural-sounding synthetic voices changing progressively between one voice and another. Two types of morphs will be generated, corresponding to the two parts of the proposed research. One type of morph will be generated between male and female voices ('gender morph') and will be used in the first part of the research to investigate how voice gender is perceived. Another type of morph will be generated between a voice A and a voice B with which participants will be familiarized ('identity morph') and will be used in the second part of the research to investigate how we recognize a person's identity from the voice. The two parts of the research - Part one on gender and Part two on identity- will then follow the exact same plan. In each part, a group of normal adult volunteers -half male and half female- will be recruited. Each participant will first be played synthetic voices from the morphs, and will be asked to decide for each voice if it sounds more like a male or a female voice (Part one) or more like voice A or voice B (Part two). This will allow to determine for each participant the voice on the morph that is the most 'ambiguous', i.e. that is classified on half the trials as male and half the trials as female (Part one), or half the trials as voice A and half the trials as voice B (Part two). Then participants will be played pairs of voices drawn for the morph, either from a same side of the ambiguous voice, or from each side of the ambiguous voice, and will be asked to decide if the two voices are the same or different. We expect that on average, participants will obtain a better performance for two voices taken from each side of the ambiguous voice. This would be a proof that they perceive the morphs in a 'categorical manner', i.e., as two distinct categories rather than as a continuum. This 'categorical perception' has already been demonstrated for morphs between different syllables -or in vision between different faces- but never for the gender or identity of voices. Two complementary techniques will then be used to measure participants' brain response to the synthetic voices: electroencephalography (EEG), and functional magnetic resonance imaging (fMRI). These two techniques will determine what parts of the participants' brain are sensitive to changes in voice gender (Part one) or voice identity (Part two). The combination of EEG and fMRI will allow a very precise characterization of these sensitive brain regions both in space (where exactly in the brain) and time (when exactly do they respond after presentation of the voice). Importantly, using synthetic voices from the morphs will ensure that the brain regions identified are really sensitive to the perceived gender (Part one) or identity (Part two) of the voices, not merely to physical characteristics of the voices. Overall, this research will increase our understanding of the way the auditory part of the brain analyses sounds of voice to allow us to rapidly and accurately extract information on a person's gender and identity simply by hearing his/her voice. This is important because very little is known on this aspect of brain function; knowing more in this area of brain research will have important implications on our understanding of how speech and language evolved in the human brain, and how brain diseases with an adverse impact on audio-visual communication, such as aphasia or autism, could be better diagnosed and treated.