Institute for Experimental Psychology, University of Regensburg, Regensburg 93053, Germany
Department of Psychological and Brain Sciences, Dartmouth College, Hanover, New Hampshire 03755.
J Neurosci. 2022 Aug 3;42(31):6131-6144. doi: 10.1523/JNEUROSCI.0301-22.2022. Epub 2022 Jun 29.
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. 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.
沃尔克曼（Volkmann）（1858 年）进行了一项开创性的研究，揭示了在触觉辨别任务上进行训练可以提高任务表现，表明存在触觉学习，并且这种触觉学习可以从训练过的身体部位转移到未训练过的身体部位。然而，触觉学习和触觉学习转移的神经机制仍然不清楚。我们在日常训练中，让一组人类受试者（女性和男性）接受训练，训练任务是刺激右手手掌或右脚脚底。在训练之前，手掌和脚底的任务表现相似。从训练过的右脚脚底到未训练的右手手掌的触觉学习转移比从训练过的右手手掌到未训练的右脚脚底的触觉学习转移更大。功能磁共振成像（fMRI）和多元模式分类分析显示，在右脚脚底受到触觉刺激时，对侧初级体感皮层（SI）中右手掌的躯体定位代表区被共同激活。右脚脚底受到触觉刺激时，右手掌皮层代表区的共同激活程度越强，右脚脚底的触觉表现越差，从训练过的右脚脚底到未训练的右手手掌的触觉学习转移越明显。相比之下，手掌受到触觉刺激时，脚底皮层代表区的共同激活程度较弱，并且与触觉表现和随后从训练过的右脚脚底到未训练的右手手掌的触觉学习转移没有关联。这些结果表明，触觉学习可能会转移到与受过训练的身体部位共同激活以支持触觉学习的未训练身体部位。知觉技能，例如触觉线索的辨别，可以通过训练得到改善，表明存在知觉学习和感觉可塑性。然而，仍然不清楚如果训练任务非常困难，是否以及如何发生这种知觉学习。在这里，我们证明了对于触觉知觉学习，手部手掌在初级体感皮层（SI）中的代表区会共同激活，以支持用脚底进行的困难触觉辨别任务的学习。这种对未训练身体部位的皮层共同激活，以支持用训练过的身体部位进行的触觉学习，可能对于从训练过的身体部位到未训练的身体部位的触觉学习转移至关重要。
