Voss Patrice, Lepore Franco, Gougoux Frédéric, Zatorre Robert J
Montreal Neurological Institute, McGill University Montreal, QC, Canada.
Front Psychol. 2011 Mar 28;2:48. doi: 10.3389/fpsyg.2011.00048. eCollection 2011.
We have previously shown that some blind individuals can localize sounds more accurately than their sighted counterparts when one ear is obstructed, and that this ability is strongly associated with occipital cortex activity. Given that spectral cues are important for monaurally localizing sounds when one ear is obstructed, and that blind individuals are more sensitive to small spectral differences, we hypothesized that enhanced use of spectral cues via occipital cortex mechanisms could explain the better performance of blind individuals in monaural localization. Using positron-emission tomography (PET), we scanned blind and sighted persons as they discriminated between sounds originating from a single spatial position, but with different spectral profiles that simulated different spatial positions based on head-related transfer functions. We show here that a sub-group of early blind individuals showing superior monaural sound localization abilities performed significantly better than any other group on this spectral discrimination task. For all groups, performance was best for stimuli simulating peripheral positions, consistent with the notion that spectral cues are more helpful for discriminating peripheral sources. PET results showed that all blind groups showed cerebral blood flow increases in the occipital cortex; but this was also the case in the sighted group. A voxel-wise covariation analysis showed that more occipital recruitment was associated with better performance across all blind subjects but not the sighted. An inter-regional covariation analysis showed that the occipital activity in the blind covaried with that of several frontal and parietal regions known for their role in auditory spatial processing. Overall, these results support the notion that the superior ability of a sub-group of early-blind individuals to localize sounds is mediated by their superior ability to use spectral cues, and that this ability is subserved by cortical processing in the occipital cortex.
我们之前已经表明，一些盲人在一只耳朵被阻塞时，能够比有视力的人更准确地定位声音，而且这种能力与枕叶皮质活动密切相关。鉴于频谱线索对于一只耳朵被阻塞时单耳定位声音很重要，并且盲人对微小的频谱差异更敏感，我们推测通过枕叶皮质机制增强对频谱线索的利用可以解释盲人在单耳定位方面表现更好的原因。我们使用正电子发射断层扫描（PET）技术，对盲人和有视力的人进行扫描，他们要区分来自单一空间位置但具有不同频谱特征的声音，这些频谱特征是根据头部相关传递函数模拟不同空间位置的。我们在此表明，一组表现出卓越单耳声音定位能力的早期盲人在这项频谱辨别任务上的表现明显优于其他任何组。对于所有组来说，对模拟周边位置的刺激表现最佳，这与频谱线索对辨别周边声源更有帮助的观点一致。PET结果显示，所有盲人组的枕叶皮质脑血流量都增加；但有视力的组也是如此。体素级协变分析表明，在所有盲人受试者中，更多的枕叶激活与更好的表现相关，但在有视力的受试者中并非如此。区域间协变分析表明，盲人的枕叶活动与几个已知在听觉空间处理中起作用的额叶和顶叶区域的活动协变。总体而言，这些结果支持这样一种观点，即一组早期盲人在声音定位方面的卓越能力是由他们利用频谱线索的卓越能力介导的，并且这种能力是由枕叶皮质的皮质处理来实现的。
