A pioneering study by Volkmann (1858) revealed that training on a tactile discrimination task improved task performance, indicative of tactile learning, and that such tactile learning transferred from trained to untrained body parts. However, the neural mechanisms underlying tactile learning and transfer of tactile learning have remained unclear. We trained groups of human subjects (female and male) in daily sessions on a tactile discrimination task either by stimulating the palm of the right hand or the sole of the right foot. Task performance before training was similar between the palm and sole. Posttraining transfer of tactile learning was greater from the trained right sole to the untrained right palm than from the trained right palm to the untrained right sole. Functional magnetic resonance imaging (fMRI) and multivariate pattern classification analysis revealed that the somatotopic representation of the right palm in contralateral primary somatosensory cortex (SI) was coactivated during tactile stimulation of the right sole. More pronounced coactivation in the cortical representation of the right palm was associated with lower tactile performance for tactile stimulation of the right sole and more pronounced subsequent transfer of tactile learning from the trained right sole to the untrained right palm. In contrast, coactivation of the cortical sole representation during tactile stimulation of the palm was less pronounced and no association with tactile performance and subsequent transfer of tactile learning was found. These results indicate that tactile learning may transfer to untrained body parts that are coactivated to support tactile learning with the trained body part.

SIGNIFICANCE STATEMENT Perceptual skills such as the discrimination of tactile cues can improve by means of training, indicative of perceptual learning and sensory plasticity. However, it has remained unclear whether and if so, how such perceptual learning can occur if the training task is very difficult. Here, we show for tactile perceptual learning that the representation of the palm of the hand in primary somatosensory cortex (SI) is coactivated to support learning of a difficult tactile discrimination task with tactile stimulation of the sole of the foot. Such cortical coactivation of an untrained body part to support tactile learning with a trained body part might be critically involved in the subsequent transfer of tactile learning between the trained and untrained body parts.

一项开创性的研究沃尔克曼 (1858)揭示了对触觉辨别任务的训练提高了任务表现，表明触觉学习，并且这种触觉学习从受过训练的身体部位转移到了未经训练的身体部位。然而，触觉学习和触觉学习迁移的神经机制仍不清楚。我们通过刺激右手手掌或右脚底，在日常课程中训练一组人类受试者（女性和男性）进行触觉辨别任务。手掌和足底训练前的任务表现相似。训练后触觉学习从受过训练的右脚底到未受过训练的右手掌的转移比从受过训练的右手掌到未受过训练的右脚掌的迁移更大。功能磁共振成像 (fMRI) 和多变量模式分类分析显示，在右脚底的触觉刺激过程中，右手掌在对侧初级体感皮层 (SI) 中的体细胞表征被共同激活。右手掌皮层表现中更明显的共激活与右脚底触觉刺激的较低触觉性能相关，以及触觉学习从受过训练的右脚底到未受过训练的右手掌的更明显的后续转移。相比之下，在手掌的触觉刺激过程中，皮质唯一表征的共激活不太明显，并且与触觉表现和随后的触觉学习转移没有关联。

意义陈述感知技能，例如触觉线索的辨别力，可以通过训练得到提高，这表明感知学习和感觉可塑性。然而，目前还不清楚如果训练任务非常困难，这种感知学习是否会发生，如果会发生，如何发生。在这里，我们展示了触觉感知学习，手掌在初级体感皮层 (SI) 中的表示被共同激活，以支持通过脚底的触觉刺激来学习困难的触觉辨别任务。这种未经训练的身体部位的皮层共激活以支持与受过训练的身体部位的触觉学习，可能在随后的受过训练和未经训练的身体部位之间的触觉学习转移中至关重要。