On the impact of tactile processing on motor cortex: how touch shapes motor behaviour.

Abstract

The ability to manipulate objects is a fundamental human skill that relies primarily on the motor system. However, effective object manipulation would not be possible without the continuous information provided by the somatosensory system. Cutaneous tactile feedback is particularly important when a movement must be adjusted while performing an action. Efficient interactions between the tactile and motor systems are therefore paramount for fine motor behaviour, as clearly demonstrated by the profound impairments observed following lesions to sensorimotor brain regions. However, somatosensory deficits following cortical damage have received considerably less attention than motor impairments, even though substantial evidence shows that such deficits are typically associated with poorer motor recovery and that preserved somatosensation is a strong predictor of motor outcome. This disconnect highlights a significant gap in the literature: despite the critical role of touch in shaping motor behaviour, the functional relationships between the tactile and motor systems remain inadequately characterized. In this review, we provide a unified (though not exhaustive) synthesis of the evidence pointing towards the substantial role of cutaneous tactile information in modulating motor cortical processing and, consequently, motor behaviour. We first describe, across species, the anatomical and neurophysiological connections linking somatosensory and motor systems and the nature of their interactions. We then review evidence from neuropathological studies demonstrating the severe consequences of disrupted tactile signals on motor performance. Finally, we examine the impact of short- and long-term tactile learning on motor function, highlighting its potential for developing novel tactile-to-motor rehabilitation strategies for individuals suffering from brain injury and other neurological conditions. Table of contents. Introduction 4. Anatomical connections between the somatosensory and motor cortices 8. Functional nature of sensorimotor interactions 13. Neuropathological evidence of sensorimotor interactions 19. Tactile and motor interactions in the context of motor planning and motor learning 26. Effects of tactile training on motor and sensorimotor performance 29. Conclusion and future perspectives 34. References 37.