Learning of tactile frequency discrimination in humans

Abstract

Learning is based on the remodeling of neural connections in the brain. The purpose of the present study was to examine the extent to which training-induced improvements in tactile frequency discrimination in humans are correlated with an increase of cortical representations in the primary somatosensory cortex. Healthy male subjects (n = 16) were trained in a tactile frequency discrimination task of the left ring finger. During the first 15 days of training, there was a steep improvement in frequency discrimination, which generalized from the trained finger to its homologue on the opposite hand, and to a lesser extent, to the other fingers on both hands. During the following 15 days of training, there was only a minor improvement in tactile frequency discrimination. Retention of improved performance in frequency discrimination 30 days after training was demonstrated for all digits. Cortical finger representation in the primary somatosensory cortex, as measured by magnetic source imaging, did not change during training. Because of the generalized training effect and the lack of detectable increase in the cortical field evoked from the trained finger, we assume that skill improvement was mediated predominantly by regions outside the primary somatosensory cortex.

Feeling Better

“…In our experiments, the coincidence of task performance with tDCS administration may have served to restrict potentiation effects to the neural populations specifically engaged in crossmodal processing or perceptual learning, leading to the persistent sensitivity improvements. Even extensive practice without brain stimulation can result in improvements in spatial (Wong, Peters, & Goldreich, 2013) and temporal (Imai et al, 2003) touch, so anodal tDCS interventions likely facilitate processing in cortical circuits that typically undergo experience-dependent plasticity. Whether comparable perceptual gains can be achieved with anodal tDCS alone remains to be tested.…”

Facilitating Effect of 15-Hz Repetitive Transcranial Magnetic Stimulation on Tactile Perceptual Learning

“…Using regular (periodic) and irregular (noisy) vibrations, they showed that in monkeys, activity in SII is best correlated to the discrimination performance. Imai et al (2003) have demonstrated that in humans intensive training of tactile frequency discrimination led to a persistent improvement with the trained and neighboring finger but did not change the primary somatosensory cortical representation as measured with magnetic source imaging, whereas Braun et al (2000) could intriguingly demonstrate that spatial discrimination training led to a differential functional reorganization in SI depending on the difference in the discrimination task.…”

Novel vibrotactile discrimination task for investigating the neural correlates of short-term learning with fMRI

“…Presently, it is increasingly proposed that training-related behavioral improvements may be mediated by changes beyond the primary (SI) and secondary (SII) somatosensory cortices (Hodzic et al, 2004;Imai et al, 2003;Karim et al, 2006), thus reinforcing the need for investigations using approaches that are compatible with fMRI techniques. Blood oxygenation-level dependent (BOLD) changes linked to tactile discrimination or learning have been previously explored using a number of innovative paradigms.…”