Schormans Ashley L, Allman Brian L
Department of Anatomy and Cell Biology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, ON, Canada.
Front Behav Neurosci. 2018 Oct 31;12:256. doi: 10.3389/fnbeh.2018.00256. eCollection 2018.
The ability to accurately integrate or bind stimuli from more than one sensory modality is highly dependent on the features of the stimuli, such as their intensity and relative timing. Previous studies have demonstrated that the ability to perceptually bind stimuli is impaired in various clinical conditions such as autism, dyslexia, schizophrenia, as well as aging. However, it remains unknown if adult-onset hearing loss, separate from aging, influences audiovisual temporal acuity. In the present study, rats were trained using appetitive operant conditioning to perform an audiovisual temporal order judgment (TOJ) task or synchrony judgment (SJ) task in order to investigate the nature and extent that audiovisual temporal acuity is affected by adult-onset hearing loss, with a specific focus on the time-course of perceptual changes following loud noise exposure. In our first series of experiments, we found that audiovisual temporal acuity in normal-hearing rats was influenced by sound intensity, such that when a quieter sound was presented, the rats were biased to perceive the audiovisual stimuli as asynchronous (SJ task), or as though the visual stimulus was presented first (TOJ task). Psychophysical testing demonstrated that noise-induced hearing loss did not alter the rats' temporal sensitivity 2-3 weeks post-noise exposure, despite rats showing an initial difficulty in differentiating the temporal order of audiovisual stimuli. Furthermore, consistent with normal-hearing rats, the timing at which the stimuli were perceived as simultaneous (i.e., the point of subjective simultaneity, PSS) remained sensitive to sound intensity following hearing loss. Contrary to the TOJ task, hearing loss resulted in persistent impairments in asynchrony detection during the SJ task, such that a greater proportion of trials were now perceived as synchronous. Moreover, psychophysical testing found that noise-exposed rats had altered audiovisual synchrony perception, consistent with impaired audiovisual perceptual binding (e.g., an increase in the temporal window of integration on the right side of simultaneity; right temporal binding window (TBW)). Ultimately, our collective results show for the first time that adult-onset hearing loss leads to behavioral plasticity of audiovisual perception, characterized by a rapid recalibration of temporal sensitivity but a persistent impairment in the perceptual binding of audiovisual stimuli.
准确整合或结合来自多种感觉模态的刺激的能力高度依赖于刺激的特征，如它们的强度和相对时间。先前的研究表明，在诸如自闭症、诵读困难、精神分裂症以及衰老等各种临床状况下，感知性结合刺激的能力会受损。然而，与衰老无关的成年后发生的听力损失是否会影响视听时间敏锐度仍不清楚。在本研究中，使用奖赏性操作条件反射训练大鼠执行视听时间顺序判断（TOJ）任务或同步判断（SJ）任务，以研究成年后发生的听力损失对视听时间敏锐度的影响的性质和程度，特别关注大声噪声暴露后感知变化的时间进程。在我们的第一系列实验中，我们发现听力正常的大鼠的视听时间敏锐度受声音强度影响，即当呈现较安静的声音时，大鼠倾向于将视听刺激感知为不同步（SJ任务），或者好像视觉刺激先呈现（TOJ任务）。心理物理学测试表明，噪声诱导的听力损失在噪声暴露后2 - 3周并未改变大鼠的时间敏感性，尽管大鼠最初在区分视听刺激的时间顺序方面存在困难。此外，与听力正常的大鼠一致，听力损失后刺激被感知为同时的时间（即主观同时性点，PSS）对声音强度仍然敏感。与TOJ任务相反，听力损失导致SJ任务期间异步检测持续受损，以至于现在更大比例的试验被感知为同步。此外，心理物理学测试发现，噪声暴露的大鼠改变了视听同步感知，这与视听感知结合受损一致（例如，同时性右侧整合时间窗口增加；右侧时间结合窗口（TBW））。最终，我们的总体结果首次表明，成年后发生的听力损失导致视听感知的行为可塑性，其特征是时间敏感性的快速重新校准，但视听刺激的感知结合持续受损。
