Use-dependent cortical plasticity in thalidomide-induced upper extremity dysplasia: evidence from somaesthesia and neuroimaging.

In this study cerebral reorganization was investigated in thalidomide-damaged subjects who use their feet to compensate for their malformed upper extremities. Tactile localization across toes was combined with fMRI to study use-dependent plasticity of the human somatosensory cortex. The manner of compensatory foot use was assessed by a questionnaire. In the behavioural experiment toes were stimulated with above threshold monofilaments and subjects had to report which toe was stimulated. When feet were employed for all everyday actions subjects made significantly fewer errors in the localization task. In subjects who use their feet only for specific actions such as grasping objects there were as many localization errors as in the control group of thalidomide-affected subjects with normal extremities. However, the patterns of mislocalizations were different with less errors occurring for the toe of the dominant foot involved in these actions. Functional MRI showed stronger haemodynamic responses to electrical stimulation of the toes in subjects using their feet for everyday actions as compared to controls. Our data show that long-term use of the feet for fine sensorimotor skills leads to better performance in tactile localization and changes in cerebral SI representation supporting the notion of use-dependent plasticity in the somatosensory cortex.