Cortical determinants of human auditory cognition

由于耳朵受损导致的听力损失最终会影响到一半的人口，是工作和家庭生活的主要障碍，也是英国经济的一大负担。如果你问任何有普通听力损失的人出了什么问题，他们都不会说‘我在2千赫的频率下损失了40分贝’：听力测试结果。他们会说，他们听不到同事在食堂工作的声音，也听不到家人吃饭的声音。在噪音中听讲话比通过听力测试简单地检测声音要复杂得多。我们必须将重叠的语音和比听力测试中的声音更大的背景噪音分开，将语音元素组合成单词和句子，并将它们与意义联系起来，这取决于我们的语言暴露和能力。因此，听力测试并不能很好地预测噪声中的语音能力，也就不能很好地预测听力设备的益处，这一点也就不足为奇了。两名相同听力损失的患者，如果接受相同的助听器，在听力测试中有相同的改善，可能会有明显不同的语言噪声能力：因此一个人对结果感到满意，另一个人扔掉助听器。在这个项目中，我们将测试受试者将具有复杂结构的声音组合在一起并保留声音的能力，并将这些声音与嘈杂的背景分开。与语音不同，声音与意义无关，在说不同语言、拥有不同语言技能的患者中，可以精确地测量它们的检测。这些测试使我们能够测量一个重要的过程，该过程与噪声中的语音分析比简单的听力测试更密切地相关。我们使用的第一个测试是独立于简单的听力测试来预测人们在噪音中听到语音的好坏。我们的目标是为听力诊所开发进一步的测试，以预测人们在现实世界中的表现如何：真实世界的听力测试。尽管我们将开发的测试评估了可能被认为是基于声音元素分组和分离的简单过程，但对这些过程的分析需要大脑的广泛处理，我们希望更好地了解这一点。这种分析需要大脑的听觉部分，但也需要大脑中通常不被认为是听觉大脑部分的部分，包括通常与记忆相关的关键结构。也许这并不令人惊讶：声音刺激不同于静态的视觉刺激，随着时间的推移而演变，声音混合的分离要求我们记住或记住构成前景和背景的元素。在这项工作中，我们将测量大脑活动，使我们能够区分噪音中的语音等混合声音。我们将使用正常听者在执行这些任务时进行的功能性磁共振成像作为大脑活动的间接测量。我们还可以直接测量癫痫患者的大脑活动，这些患者在大脑中放置电极几天，以便找出癫痫从哪里开始。除了定位他们的癫痫，我们还可以测量在聆听任务中的大脑活动。这些大脑实验的结果将是定义大脑系统，以区分噪音中的语音等声音。首先，这将提供其他措施(除了新的听力测试)，以衡量助听器、人工耳蜗植入或听力训练等干预措施的成功。其次，这项工作将提出可能的干预措施，帮助患者理解噪音中的语音。尽管试图通过干扰大脑来改善噪声中的语音检测可能看起来有些牵强，但已经有证据表明，微创电刺激可以做到这一点，这项工作可以识别药物治疗的大脑靶点。

Hearing loss due to ear damage eventually affects half the population, is a major obstacle to work and home life, and a drain on the UK economy. If you ask anyone with common hearing loss what is wrong, they will NOT say 'I have lost 40 decibels at 2 kilohertz': the hearing-test result. They WILL say that they cannot hear colleagues at work in the canteen, or their family at dinner. Listening to speech in noise is much more complicated than the simple detection of sounds measured with hearing tests. We have to separate overlapping speech sounds and background noise that are louder than the sounds in hearing tests, group together speech elements into words and sentences, and associate those with meaning, which depends on our language exposure and ability. It is not surprising, then, that the hearing test, measuring the detection of tones in quiet, is not a good predictor of speech-in-noise ability, or the benefit from hearing devices. Two patients with the same hearing loss who are given the same hearing aids with the same improvement in their hearing tests can have strikingly different speech in noise ability after: so that one is happy with the result and the other throws the hearing aid away.In this programme we will develop tests of the ability of subjects to group together and retain sounds that have a complex structure, like speech, and separate these from a noisy background. Unlike speech, the sounds are not associated with meaning, and their detection can be measured precisely in patients that speak different languages and have different language skills. These tests allow us to measure an important process that is more closely related to speech-in-noise analysis than simple hearing tests. The first tests we have used predict how well people hear speech in noise independently of simple hearing tests. We aim to develop further tests for the hearing clinic to predict how well people will manage in the real world: real world listening tests.Although the tests we will develop assess what might be considered a simple process based on grouping and separation of sound elements, the analysis of these requires extensive processing in the brain, which we want to understand better. This analysis requires the auditory part of the brain, but also parts of the brain that are not usually considered parts of the auditory brain, including key structures usually associated with memory. Perhaps this is not surprising: sound stimuli, unlike static visual stimuli, evolve over time, and the separation of mixtures of sound requires us to remember or hold in mind the elements that form the foreground and background. In this work, we will measure brain activity that allows us to separate mixtures of sounds like speech in noise. We will use functional magnetic resonance imaging carried out on normal listeners when they carry out these tasks as an indirect measure of brain activity. We can also measure brain activity directly, in patients with epilepsy who have electrodes placed in the brain for a few days in order to work out where the epilepsy starts. As well as the localising their epilepsy, we can measure brain activity during listening tasks.The outcome of these brain experiments will be the definition of brain systems for separating sounds like speech in noise. This will, firstly, provide other measures (in addition to the new listening tests) tests) of the success of interventions like hearing aids, cochlear implants, or hearing training. Secondly, the work will suggest possible interventions that might help patients to understand speech in noise. Although it may seem far fetched to try to improve speech-in-noise detection by interfering with the brain, there is already evidence that minimally invasive electrical stimulation can do this, and the work could identify brain targets for drug treatments.