The various forms of sensorimotor plasticity following limb amputation and their link with rehabilitation strategies

Stable Cortical Body Maps Before and After Arm Amputation

The adult brain's capacity for cortical reorganization remains debated. Using longitudinal neuroimaging in three adults, followed up to five years before and after arm amputation, we compared cortical activity elicited by movement of the hand (pre-amputation) versus phantom hand (post-amputation) and lips (pre/post-amputation). We observed stable representations of both hand and lips. By directly quantifying activity changes across amputation, we overturn decades of animal and human research, demonstrating amputation does not trigger large-scale cortical reorganization.

What you feel is not always what you've got. Jean Lhermitte (1877-1959) and the phantom limb phenomenon

Jean Lhermitte (1877-1959), the French neurologist and psychiatrist, is most often associated with the sign he described in three patients with multiple sclerosis, back in 1927. In 1937, Lhermitte analytically studied a series of 28 amputees experiencing phantom limb sensations further to amputations dating between 1891 and 1934. After having described the main clinical characteristics of this unpublished series, we will detail the ideas advanced by Jean Lhermitte regarding the phenomenon of the phantom limb. Lhermitte will use these observations to develop conceptions of consciousness and the body schema encompassing very modern resonances.

How Does the Central Nervous System for Posture and Locomotion Cope With Damage-Induced Neural Asymmetry?

In most vertebrates, posture and locomotion are achieved by a biomechanical apparatus whose effectors are symmetrically positioned around the main body axis. Logically, motor commands to these effectors are intrinsically adapted to such anatomical symmetry, and the underlying sensory-motor neural networks are correspondingly arranged during central nervous system (CNS) development. However, many developmental and/or life accidents may alter such neural organization and acutely generate asymmetries in motor operation that are often at least partially compensated for over time. First, we briefly present the basic sensory-motor organization of posturo-locomotor networks in vertebrates. Next, we review some aspects of neural plasticity that is implemented in response to unilateral central injury or asymmetrical sensory deprivation in order to substantially restore symmetry in the control of posturo-locomotor functions. Data are finally discussed in the context of CNS structure-function relationship.