Department of Psychology, Neuroscience & Behaviour, McMaster University, Hamilton, ON, Canada L8S 4K1;
Department of Psychology, Neuroscience & Behaviour, McMaster University, Hamilton, ON, Canada L8S 4K1.
Proc Natl Acad Sci U S A. 2020 May 5;117(18):10089-10096. doi: 10.1073/pnas.1914668117. Epub 2020 Apr 22.
Synesthesia is a neurologic trait in which specific inducers, such as sounds, automatically elicit additional idiosyncratic percepts, such as color (thus "colored hearing"). One explanation for this trait-and the one tested here-is that synesthesia results from unusually weak pruning of cortical synaptic hyperconnectivity during early perceptual development. We tested the prediction from this hypothesis that synesthetes would be superior at making discriminations from nonnative categories that are normally weakened by experience-dependent pruning during a critical period early in development-namely, discrimination among nonnative phonemes (Hindi retroflex /d̪a/ and dental /ɖa/), among chimpanzee faces, and among inverted human faces. Like the superiority of 6-mo-old infants over older infants, the synesthetic groups were significantly better than control groups at making all the nonnative discriminations across five samples and three testing sites. The consistent superiority of the synesthetic groups in making discriminations that are normally eliminated during infancy suggests that residual cortical connectivity in synesthesia supports changes in perception that extend beyond the specific synesthetic percepts, consistent with the incomplete pruning hypothesis.
联觉是一种神经特质，其中特定的诱发因素，如声音，会自动引起额外的独特感知，如颜色（因此称为“色听”）。对于这种特质的一种解释——也是这里测试的解释——是，联觉是由于在早期感知发展过程中，皮质突触过度连接的修剪异常微弱导致的。我们测试了这一假设的预测，即联觉者在从非母语类别进行区分方面会更出色，这些类别在发展早期的关键时期中，由于经验依赖性修剪而通常减弱，具体来说，是在区分非母语音素（印地语卷舌音/d̪a/和齿龈音/ɖa/）、黑猩猩面孔和倒置的人脸方面。与 6 个月大的婴儿优于年长婴儿的情况一样，联觉者在所有五个样本和三个测试地点的所有非母语区分任务中都明显优于对照组。联觉者在进行通常在婴儿期就被消除的区分方面具有一致的优势，这表明联觉中的残余皮质连接支持感知的变化，这些变化不仅限于特定的联觉感知，与不完全修剪假说一致。
