Recent findings in clinical neurophysiology show that the cortical representation of an
amputated hand is not so largely affected, as once thought, by critical rearrangements, and that
central and peripheral neural connections somehow maintain their functions. These findings
paved the way towards the exploitation of cortical and peripheral residual functions by neural
interfaces for hand prosthesis control. In the present study, a young male amputee has been
implanted with four intraneural multielectrodes, two in the median and two in the ulnar stump
nerves. During the next four weeks, these electrodes were used with the double purpose of
recording neural signals (for the extraction of subject’s motor intentions to be performed by the
robotic hand prosthesis) and eliciting sensory feedback through proper electrical stimulation
(pulses frequency and duty cycle). Recorded neural signals were mapped in real-time onto three
actions of the robotic hand through an amplitude on the best matching channel threshold
method, while, thanks to an AI classifier trained offline, was achieved an 85% accuracy.
Recorded peripheral nerves activity was then compared with the cortical activity over the
missing hand motor area. By performing the classification of the motor intention over the
peripheral signals solely during a time window compatible with the transmission delay of the
motor command from the cortex, identified as an event related desynchronization of the EEG
rhythm, the classification rate approached 100% of success. The study also aimed at
investigating possible neurorehabilitative effects of the re-acquired stream of data to/from the
missing limb and the continuative use of a high-interactive hand prosthesis. Results show that
training for robotic hand control and for sensory perception produced a normalization in the
electroencephalographic activation pattern and a reorganization of the motor cortical maps as
evaluated via TMS, with restriction of the cortical overrepresentation of muscles proximal to the
stump. In parallel, a clinical improvement of phantom limb pain has been observed, that
recognizes in the correction of the aberrant plasticity in its anatomical substrate.
Keywords: Robotic Hand Electrodes, Multi-channel Interfaces, Proprioceptive and Tactile Feedback, Clinical
Neurophysiology, Brain Plasticity, Phantom Limb Pain.
