Improving human haptic performance in normal and impaired human populations through unattended activation-based learning

Abstract

Human haptic performance is not fixed, but subject to major alterations through learning processes. We describe a new stimulation protocol that allows to improve haptic performance in humans in a highly systemic way through unattended activation-based learning. The so-called coactivation protocol is based upon temporal constraints of Hebbian learning where simultaneity plays a key role for the induction of plastic changes. We provide an overview about the potential of coactivation by summarizing recent findings showing that coactivation alters a broad range of basic as well as cognitively demanding types of haptic performance in parallel to cortical reorganization in somatosensory cortex. For example, coactivation applied to the tip of the index finger, or to all fingers of the dominant hand improves tactile acuity, but also haptic object recognition, and speeds up multiple-choice reaction times. Because such changes persist between 24 h and 1 week without further intervention, we interpret the underlying processes as a particular form of perceptual learning. We describe results where coactivation has been utilized for therapeutical purposes in impaired human populations, we outline new developments to optimize and extend unattended activation-based learning protocols, and we sketch the next steps necessary to apply the concept of unattended activation-based learning on a regular and reliable basis as a therapeutical tool in order to selectively interfere with impaired haptic performance.