Rakesh Kottu Srisai, Lazar Leslee
Department of Cognitive and Brain Sciences, Indian Institute of Technology Gandhinagar, Palaj, Gandhinagar, India.
Department of Cognitive and Brain Sciences, Indian Institute of Technology Gandhinagar, Palaj, Gandhinagar, India.
Cortex. 2025 Feb;183:38-52. doi: 10.1016/j.cortex.2024.09.015. Epub 2024 Oct 29.
This study investigates the impact of vision on the maintenance of hand representation in the implicit body model, particularly focusing on congenitally blind individuals. To address this, we performed a hand landmark localization task on blind individuals who lacked visual experience of their bodies and compared their performance to normally sighted and normally sighted but blindfolded participants. Through measurements of finger lengths, hand width, and shape index, we demonstrate that blind participants exhibit significantly greater distortions in their hand representation compared to sighted and blindfolded controls. Notably, blind individuals displayed a marked overestimation of hand width and an underestimation of finger lengths, particularly in digits D2, D3, and D4. Surprisingly, blind subjects with partial vision displayed more severe distortions than those with no residual vision. Furthermore, our findings reveal that late-blind participants exhibit similar levels of distortion as congenitally blind individuals, suggesting an extended period of susceptibility to the lack of visual input in shaping body representations. The Reverse Distortion (RD) hypothesis provides a plausible explanation for these distortions, suggesting that compensatory mechanisms occur within the body model to counteract the anisotropic cortical representations. Our results support this hypothesis: blind individuals have expanded cortical representations processing tactile information, so this could lead to more pronounced distortions in their hand representation of the body model. This underscores the importance of visual input in modulating body representations. Overall, our study highlights the malleability of body representations and the intricate interplay between sensory inputs and cortical processing in shaping the implicit body model.
本研究调查视觉对隐性身体模型中手部表征维持的影响，尤其关注先天性失明个体。为解决这一问题，我们对缺乏身体视觉体验的盲人个体进行了手部地标定位任务，并将他们的表现与正常视力者以及正常视力但被蒙住眼睛的参与者进行比较。通过测量手指长度、手宽和形状指数，我们证明与有视力和蒙眼的对照组相比，盲人参与者在手部表征上表现出明显更大的扭曲。值得注意的是，盲人个体对手宽有明显高估，而对手指长度有低估，特别是在食指、中指和无名指。令人惊讶的是，有部分视力的盲人受试者比没有残余视力的受试者表现出更严重的扭曲。此外，我们的研究结果表明，晚期失明参与者与先天性失明个体表现出相似程度的扭曲，这表明在塑造身体表征方面，对缺乏视觉输入的易感性持续时间更长。反向扭曲（RD）假说为这些扭曲提供了一个合理的解释，表明在身体模型内会发生补偿机制以抵消各向异性的皮质表征。我们的结果支持这一假说：盲人个体扩展了处理触觉信息的皮质表征区域，所以这可能导致他们在身体模型的手部表征上出现更明显的扭曲。这突出了视觉输入在调节身体表征中的重要性。总体而言，我们的研究强调了身体表征的可塑性以及感觉输入与皮质处理在塑造隐性身体模型过程中的复杂相互作用。
