Visual Processing in Deaf Signers: Psychophysics and Brain Imaging Studies

在国家科学基金会的支持下，多布金斯博士和他的同事们将进行一项为期三年的研究，调查早发性感觉剥夺对知觉和神经的影响。聋人从出生起就被剥夺听力，依靠视觉语言(即美国手语，ASL)进行交流，这为研究剩余感觉(特别是视觉)内的感觉处理如何以及在多大程度上因感觉体验改变而改变提供了独特的机会。长期以来，人们一直认为(主要是通过轶事证据)，聋子“看”得更好(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，令人惊讶的是，人们对聋人的视觉加工知之甚少。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？”)以及大脑成像技术(定位和测量由视觉刺激引起的神经活动)，以表征聋人和听力受试者在视觉处理方面的差异。在我们之前的NSF研究中，我们专注于视觉运动处理，认为运动对聋人来说可能特别重要，因为1)由于理解在很大程度上依赖于手的运动，2)在没有听觉提示的情况下，聋人可能依赖周围的运动来帮助他们定向到进入他们视野的物体。这些研究的结果显示，聋人手语者在运动加工中存在强大的右视野/左半球优势，这可能可以通过提出理解语言所需的知觉过程(在ASL的情况下，运动加工)由左脑、语言主导的半球来招募来解释。在目前的提案中，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，即颜色和形状处理来扩展这些发现。此外，作为我们之前的注意力研究的延伸，我们将调查聋人和听力受试者之间的注意资源是否存在差异，特别是在外围视野中。最后，结合这些视觉研究，我们将进行语言学研究，考察语言在个别受试者中偏向左半球的程度。这将使我们能够进一步调查聋人的视觉和语言经验之间的拟议联系。这项拟议活动的智力价值包括提高我们对大脑发育中的感觉区域如何对改变的感觉输入做出反应进行自我重组的知识，这应该会对大脑发育的一般原则产生影响。从临床的角度来看，这些结果可能有助于为听力不足的人设计补偿计划，他们可以接受培训，利用感觉处理的那些方面，这些方面最适合于对改变的感觉输入做出反应。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体的特殊功能。这些项目的更广泛影响包括一个强有力的外展部分；就其性质而言，它们将代表人数不足的群体的人(即聋人)作为研究对象。它们还吸引聋人接受我们实验室的研究人员培训。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)外，这些项目的成果还通过PI的课程教学(如“感觉和知觉”和“生理心理学”)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".