Visual Processing in Deaf Signers: Psychophysics and Brain Imaging Studies

在美国国家科学基金会（National Science Foundation）的支持下，多布金斯博士及其同事将开展一项为期三年的研究，调查早发性感觉剥夺的感知和神经后果。聋人自出生以来就被剥夺了听觉，他们依靠视觉语言（即美国手语，ASL）进行交流，对聋人的研究提供了一个独特的机会来研究剩余感官（特别是视觉）的感觉处理是如何以及在多大程度上由于感觉经验的改变而被改变的。长期以来，人们一直认为（主要是通过轶事证据）聋人“看”得更好（而盲人“听”得更好）。然而，由于听力研究人员和聋人受试者（他们说不同的语言，属于不同的文化）之间交流的困难性质，令人惊讶的是，对聋人的视觉处理知之甚少。为了研究这个问题，我们使用了两种心理物理技术（即，要求受试者报告在视频监视器上呈现给他们的刺激，例如，“刺激是向上移动还是向下移动？”）脑成像技术（定位和测量由视觉刺激引起的神经活动）可以表征聋人和听力正常的受试者在视觉处理方面的差异。在我们之前的NSF研究中，我们关注的是视觉运动处理，我们认为运动对聋人受试者来说可能特别重要，因为1)美国手语理解严重依赖手部的运动；2)在缺乏听觉线索的情况下，聋人受试者可能依赖于他们周边的运动来帮助他们定位进入他们视野的物体。这些研究的结果表明，聋哑人的右视野/左半球在运动处理方面具有强大的优势，这可能是由语言理解所需的感知过程（在美国手语的情况下是运动处理）由语言主导的左半球吸收来解释的。在当前的提案中，我们通过测试聋人和听力受试者的运动处理，以及其他两个视觉领域，即颜色和形式处理，来扩展这些发现。此外，作为我们先前注意力研究的延伸，我们将调查聋人和听力人之间的注意力资源是否存在差异，特别是在外围视野方面。最后，结合这些视觉研究，我们将进行语言研究，以检查语言在个体受试者中向左半球偏侧的程度。这将使我们能够进一步研究聋人的视觉和语言经验之间的联系。这一活动在智力上的价值包括推进我们对大脑中正在发育的感觉区域如何根据改变的感觉输入进行自我重组的认识，这应该对大脑发育的一般原理有启示。从临床角度来看，这些结果可能有助于为听觉剥夺者设计补偿程序，他们可以接受训练，利用那些最能适应改变的感觉输入的感觉处理方面。此外，随着人工耳蜗植入频率的上升，我们的发现可能有助于为聋人设计这些假肢装置的特殊功能。这些项目的广泛影响包括强有力的外联部分；就其本质而言，它们包括来自代表性不足的群体（即聋人）的人作为研究对象。他们还吸引聋人来我们的实验室接受研究人员的培训。最后，除了通过会议和期刊出版物接触到广泛的受众（包括心理物理学、神经科学、发展和语言学领域的研究人员）之外，这些项目的结果还通过PI的“感觉与感知”和“生理心理学”等课程的教学带给加州大学圣地亚哥分校的本科生和研究生。

With National Science Foundation support, Dr. Dobkins and colleagues will conduct a three-year study to investigate the perceptual and neural consequences of early-onset sensory deprivation. The study of deaf individuals, who have been auditorily deprived since birth and who rely upon a visual language (i.e., American Sign Language, ASL) for communication, affords a unique opportunity to investigate how and the degree to which sensory processing within the remaining senses (specifically vision) is modified as a result of altered sensory experience. It has long been thought (mostly through anecdotal evidence) that the deaf "see" better (and that the blind "hear" better). However, owing to the difficult nature of communication between hearing researchers and deaf subjects (who speak different languages and are part of different cultures), surprisingly little is known about visual processing in the deaf. To investigate this issue, we use both psychophysical techniques (i.e., asking subjects to report about stimuli presented to them on a video monitor, e.g., "did the stimulus move up or down?") and brain imaging techniques (which localize and measure neural activity elicited by visual stimuli) to characterize differences in visual processing between deaf and hearing subjects. In our prior NSF studies, we focused on visual motion processing, with the notion that motion may be particularly important to deaf subjects, since 1) ASL comprehension relies heavily on the motion of the hands and 2) in the absence of auditory cues, deaf subjects may rely on motion in their periphery to help orient them to objects entering their visual field. The results of these studies revealed a robust right visual field / left hemisphere dominance for motion processing in deaf signers, which can potentially be accounted for by proposing that perceptual processes required for the comprehension of language (motion processing in the case of ASL) get recruited by the left, language-dominant hemisphere. In the current proposal, we expand on these findings by testing deaf and hearing subjects on motion processing, as well as two other domains of vision, namely color and form processing. In addition, as an extension of our previous attentional studies, we will investigate whether attentional resources differ between deaf and hearing subjects, particularly in the peripheral visual fields. Finally, in combination with these visual studies, we will conduct linguistic studies that examine the degree to which language is lateralized to the left hemisphere within individual subjects. This will allow us to investigate further the proposed link between the deaf's visual and linguistic experience. The intellectual merits of this proposed activity include advancing our knowledge of how developing sensory areas of the brain reorganize themselves in response to altered sensory input, which should have implications for principles of brain development in general. From the clinical standpoint, the results may be useful in designing compensatory programs for auditorily-deprived persons, who could be trained to exploit those aspects of sensory processing that are most adaptive in response to altered sensory input. Moreover, with the frequency of cochlear implants on the rise, our findings may be helpful in designing special features for these prosthetic devices in deaf individuals. The broader impacts of these projects include a strong outreach component; by their very nature, they include people from an underrepresented group (i.e., deaf people) as subjects. They also attract deaf people to be trained as researchers in our laboratory. Finally, in addition to reaching a broad audience (including researchers in the fields of psychophysics, neuroscience, development and linguistics) through conferences and journal publications, the results of these projects are brought to both undergraduate and graduate students at UC San Diego through the PI's teaching of courses such as "Sensation and Perception" and "Physiological Psychology".