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.

Electroencephalogram Signal Correlations between Default Mode Network and Attentional Functioning

Attentional issues may affect acquiring new information, task performance, and learning. Cortical network activities change during different functional brain states, including the default mode network (DMN) and attention network. We investigated the neural mechanisms underlying attentional functions and correlations between DMN connectivity and attentional function using the Trail-Making Test (TMT)-A and -B. Electroencephalography recordings were performed by placing 19 scalp electrodes per the 10 - 20 system. The mean power level was calculated for each rest and task condition. Non-parametric Spearman’s rank correlation was used to examine the correlation in power levels between the rest and TMT conditions. The most significant correlations during TMT-A were observed in the high gamma wave, followed by theta and beta waves, indicating that most correlations were in the parietal lobe, followed by the frontal, central, and temporal lobes. The most significant correlations during TMT-B were observed in the beta wave, followed by the high and low gamma waves, indicating that most correlations were in the temporal lobe, followed by the parietal, frontal, and central lobes. Frontoparietal beta and gamma waves in the DMN may represent attentional functions.

Taming desynchronized bursting with delays in the Macaque cortical network

Inhibitory coupled bursting Hindmarsh-Rose neurons are considered as constitutive units of the Macaque corti- cal network. In the absence of information transmission delay the bursting activity is desynchronized, giving rise to spatiotemporally disordered dynamics. This paper shows that the introduction of finite delays can lead to the synchro- nization of bursting and thus to the emergence of coherent propagating fronts of excitation in the space-time domain. Moreover, it shows that the type of synchronous bursting is uniquely determined by the delay length, with the transi- tions from one type to the other occurring in a step-like manner depending on the delay. Interestingly, as the delay is tuned close to the transition points, the synchronization deteriorates, which implies the coexistence of different bursting attractors. These phenomena can be observed by different but fixed coupling strengths, thus indicating a new role for information transmission delays in realistic neuronal networks.