Schweizer R, Braun C, Fromm C, Wilms A, Birbaumer N
Institute of Medical Psychology and Behavioral Neurobiology, MEG-Center, University of Tuebingen, Germany.
Exp Brain Res. 2001 Aug;139(4):435-42. doi: 10.1007/s002210100793.
The somatosensory system has been shown to alter its cortical activation patterns in reaction to changes in the attended sensory input to certain body parts. Whether these modifications in the functional organization of the somatosensory cortex of humans also result in perceptual changes has rarely been investigated. Here we used near-threshold tactile stimuli to the center of the fingertips to evoke mislocalizations to fingers other than the stimulated. In healthy untrained subjects, the distribution of the mislocalizations from each of the fingers was different from a distribution expected if the subjects were purely guessing the position of the stimulus. The digits next to the stimulated one receive a higher number of mislocalizations than digits further away from the stimulated digits. This decrease can be accounted for by digit-overlapping receptive fields in combination with the sequential representation of the digits in the primary somatosensory cortex. In a second experiment subjects received 20 h of simultaneous stimulation of the left thumb and little finger in the context of a perceptual task. For both hands, the distribution of mislocalization from these fingers was analyzed at the beginning and the end of the training. For the left hand, the number of assigned mislocalizations to the most distant neighbor digit (i.e., the simultaneously stimulated digit in the training) increased while the number of mislocalizations toward the direct neighboring digit decreased with the training. This change did not occur in the untrained right hand, or in the untrained subjects. We conclude that the distribution of mislocalization to fingers other than the stimulated can be used to investigate perceptual changes paralleling training-induced modifications in the activation patterns of the somatosensory cortex.
体感系统已被证明会根据对特定身体部位的关注感觉输入的变化来改变其皮质激活模式。人类体感皮质功能组织的这些改变是否也会导致感知变化，这一点很少被研究。在这里，我们使用接近阈值的触觉刺激指尖中心，以诱发对受刺激手指以外的其他手指的错误定位。在健康的未经训练的受试者中，每个手指的错误定位分布与受试者纯粹猜测刺激位置时预期的分布不同。受刺激手指旁边的手指比离受刺激手指更远的手指收到更多的错误定位。这种减少可以通过数字重叠的感受野与初级体感皮质中数字的顺序表示相结合来解释。在第二个实验中，受试者在感知任务的背景下接受了20小时的左手拇指和小指同时刺激。对于双手，在训练开始和结束时分析了这些手指的错误定位分布。对于左手，随着训练的进行，分配给最远相邻手指（即训练中同时受刺激的手指）的错误定位数量增加，而指向直接相邻手指的错误定位数量减少。这种变化在未经训练的右手或未经训练的受试者中没有发生。我们得出结论，对受刺激手指以外的其他手指的错误定位分布可用于研究与训练引起的体感皮质激活模式改变平行的感知变化。
