Behavioral significance of input-dependent plasticity of human somatosensory cortex

Training and learning induce powerful cortical reorganizational changes, which are referred to as use- or experience-dependent plasticity. Using MEG, we investigated how rapid reorganization of human somatosensory cortex induced by tactile stimulation leads to improved spatial discrimination performance. Plastic changes were induced by several hours of tactile co-activation in separated receptive fields on the right index finger. Subjects did not attend the stimulation but performed their daily work. We found a 20% decrease in spatial two-point discrimination thresholds paralleled by a dipole shift in medio-lateral direction along the central sulcus. We conclude that reorganization of primary somatosensory cortex induced by purely passive tactile co-activation is sufficient to improve tactile discrimination performance without training, attention or reinforcement.