Neuromorphic transcutaneous electrical nerve stimulation(nTENS)induces efficient tactile-related cortical networks in forearm amputees

Conventional transcutaneous electrical nerve stimulation(cTENS),which uses a modulated square waveform as stimuli,has been generally used in testing and eliciting artificial tactile perception in forearm amputees.However,a novel neuromorphic TENS(nTENS)model based on neural signals has been largely ignored.In this study,we further explore the effect of nTENS patterns to elicit tactile perception in forearm amputees.Four forearm amputees were recruited to test discriminate tactile perception elicited by different TENS patterns with electroencephalography(EEG)recording at the following four stimulated sites:the index finger and the little finger on both phantom and real sides.Finally,we compared the results of cortical networks in six frequency bands at different stimulated sites between forearm amputees and able-bodied subjects.Behavioral results suggested that n TENS patterns required a lower electric charge at each stimulated site than cTENS patterns.And forearm amputees required a higher intensity in each TENS pattern than able-bodied subjects.Moreover,amputees showed a lower clustering coefficient(aCP),global efficiency(aEG),local efficiency(aEL),and a longer path length(aLP)than able-bodied subjects in all six frequency bands when stimulation was accessed.Specifically,the SMU pattern showed a higher functional network efficiency in real fingers than at phantom sites in theta,alpha,and high gamma bands.This study highlighted the characteristics of n TENS patterns in eliciting tactile perception among forearm amputees,which provided insights into evaluating the neural mechanism of tactile information processing in forearm amputees and building tactile perceptual systems for sensory rehabilitation.

Chronic electrical stimulation induces functional network changes in cortical neuron cultures

Recent studies demonstrated that a functional brain network could be regarded as a complex network.With the help of network theory,neuroscientists can identify common organizational principles of the functional brain networks.As a consequence,some non-random organizational features,such as"small world"(most of the nodes are not connected directly but can communicate with few intermediate relay steps)and"rich club"(nodes that are rich in connections tend to form strongly interconnected clubs),have been found in functional brain network.Recently,the"small world"organizational feature of neuronal functional networks in vitro was found to be influenced by external applications.However,little is known about the influence of chronic electrical stimulation on functional networks of dissociated cortical cultures during network development.In the present study,cortical cultures were electrically stimulated at a frequency of 0,0.02,and 0.2 Hz,between 7 and 26 days in vitro(DIV).The spontaneous activity of the cortical cultures was recorded using MEAs.Next,a cross-covariance method and graph theory were applied to investigate organizational feature of functional networks.Our results showed that over 3 weeks of stimulation,the network density significantly increased with maturation in the control and 0.02 Hz stimulation groups,but not in 0.2 Hz stimulation groups.Moreover,all the cultures had a small-world topology at 14,18,22,and 26 DIV,free from the effect of chronic electrical stimulation.Besides,we found an asymmetry effect that partial electrical stimulation inhibited the formation of node connections in stimulated areas.This effect was more pronounced at 0.2 Hz than at 0.02 Hz stimulation.Our results suggest that electrical stimulation does not affect the small-world properties of neural cultures.Instead,electrical stimulation modulates connectivity patterns,and neurons within the stimulated area are less connected than neurons outside the stimulated area.