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There is considerable trial-to-trial variability in single cortical neurons when performing the same action repeatedly. One possibility is that neural populations are more stable in representing actions; alternatively, they too may be distinctly engaged from trial-to-trial. To address the nature of variability in large neural populations, we captured the EEG signals time-locked to repeated voluntary thumb flexion movements (∼500 repetitions, 23 subjects). By using non-negative matrix factorization on the low-frequency sensorimotor cortical signals, we quantified the trial-to-trial motor-related potentials (MRPs) in terms of prototypical signals (meta-MRPs) and their corresponding prominence at each trial (meta-trials). Clustering the meta-MRPs across the sampled population revealed 5 distinct signal patterns. There were brain-wide correlates of these meta-MRP clusters. Cortical hemispheres were distinctly recruited from trial-to-trial as certain clusters were accompanied by bilateral motor negativity while others were characterized by ipsilateral motor negativity. The sensory feedback too was distinctly processed from trial-to-trial as the central post-movement positivity was present only for certain clusters. A poorly understood pre-motor positivity accompanied all clusters albeit varying in their timing from trial-to-trial. These patterns – including the time-varying positivity preceding the movement – were rendered invisible by the traditional averaging of the signals. We suggest that the variability in EEG signals is not just noise but a consequence of distinct activation patterns deployed by the cortex. We support the idea that the cortex flexibly switches between distinct forms of neural processing to achieve the same behavioral goals.

Smartphones offer unique opportunities to trace the convoluted behavioral patterns accompanying healthy aging. Here we captured smartphone touchscreen interactions from a healthy population (N = 684, ∼309 million interactions) spanning 16 to 86 years of age and trained a decision tree regression model to estimate chronological age based on the interactions. The interactions were clustered according to their next interval dynamics to quantify diverse smartphone behaviors. The regression model well-estimated the chronological age in health (mean absolute error = 6 years, R2 = 0.8). We next deployed this model on a population of stroke survivors (N = 41) to find larger prediction errors such that the estimated age was advanced by 6 years. A similar pattern was observed in people with epilepsy (N = 51), with prediction errors advanced by 10 years. The smartphone behavioral model trained in health can be used to study altered aging in neurological diseases.

Nonlinear dependencies among highly correlated variables of a multifaceted process system pose significant challenges for process safety assessment. The copula function is a flexible statistical tool to capture complex dependencies and interactions among process variables in the causation of process faults. An integration of the copula function with the Bayesian network provides a framework to deal with such complex dependence. This study attempts to compare the performance of the copula-based Bayesian network with that of the traditional Bayesian network in predicting failure of a multivariate time dependent process system. Normal and abnormal process data from a small-scale pilot unit were collected to test and verify performances of failure models. Results from analysis of the collected data establish that the performance of copula-based Bayesian network is robust and superior to the performance of traditional Bayesian network. The structural flexibility, consideration of non-linear dependence among variables, uncertainty and stochastic nature of the process model provide the copula-based Bayesian network distinct advantages. This approach can be further tested and implemented as an online process monitoring and risk management tool.

Summary A range of abnormal electrical activity patterns termed epileptiform discharges can occur in the brains of persons with epilepsy. These epileptiform discharges can be monitored and recorded with implanted devices that deliver therapeutic neurostimulation. These continuous recordings provide an opportunity to study the behavioral correlates of epileptiform discharges as the patients go about their daily lives. Here, we captured the smartphone touchscreen interactions in eight patients in conjunction with electrographic recordings (accumulating 35,714 h) and by using an artificial neural network model addressed if the behavior reflected the epileptiform discharges. The personalized model outputs based on smartphone behavioral inputs corresponded well with the observed electrographic data (R: 0.2–0.6, median 0.4). The realistic reconstructions of epileptiform activity based on smartphone use demonstrate how day-to-day digital behavior may be converted to personalized markers of disease activity in epilepsy, Graphical abstract, Highlights • Brain implants can continuously log abnormal activity patterns in epilepsy. • Real-world behavioral implications of the abnormal activity are not clear. • An artificial neural network inferred brain activity based on smartphone behavior. • Diurnal and other behavioral patterns were leveraged by the network., Behavioral neuroscience; Bioengineering; Neural networks

The complexities of process plants are increasing because of process integration and plant-wide optimization. Failure models of a process system (henceforth referred to as process-accident models) ...

Summary Striatal dopamine and smartphone behavior have both been linked with behavioral variability. Here, we leverage day-to-day logs of natural, unconstrained smartphone behavior and establish a correlation between a measure of smartphone social activity previously linked with behavioral variability and a measure of striatal dopamine synthesis capacity using [18F]-DOPA PET in (N = 22) healthy adult humans. Specifically, we find that a higher proportion of social app interactions correlates with lower dopamine synthesis capacity in the bilateral putamen. Permutation tests and penalized regressions provide evidence that this link between dopamine synthesis capacity and social versus non-social smartphone interactions is specific. These observations provide a key empirical grounding for current speculations about dopamine's role in digital social behavior., Graphical abstract, Highlights • Putamen dopamine synthesis capacity correlates with smartphone social app use. • The correlation parallels a prior link between social app use and motor variability. • It is selective to social app use, controlling for multiple smartphone use factors., Behavioral neuroscience; Biological sciences; Neuroscience

Brain areas representing the body can change in response to behavioral alterations. This idea is firmly established for the adult cortex in response to extraordinary alterations such as traumatic amputation or casting of the limb. Here we address how adult cortical sensorimotor processing alters in response to a subtle perturbation in the form of smartphone deprivation lasting for ~7 days. We quantified the sensorimotor processes associated with the fingertips before and after the deprivation in right-handed smartphone users. The measurements were contrasted with those of a control group with unperturbed smartphone behavior. First, smartphone tapping speed in daily life became slower after the deprivation. Second, according to reaction time tests conducted in the laboratory the asymmetrically superior performance of the right vs. left thumb was eroded by the deprivation. Third, according to EEG measurements at physical rest, tactile stimulation at the right thumb tip resulted in smaller signal amplitudes after the deprivation. Moreover, the EEG measurements during smartphone use revealed larger signal amplitudes for tactile stimulation at the right little fingertip after the deprivation. We show that cortical plasticity can occur by merely disengaging from a common day-to-day behavior. We suggest that in daily life the adult brain continuously and selectively updates its sensorimotor processing according to recent experience.

Clinical observations suggest dynamic alterations in behavior after brain surgery. While some alterations reportedly occur within days others gradually develop over several months. These alterations can be attributed to the pre-surgical impact of the diseased tissue, neuronal damage caused by the surgery, and subsequent plasticity. A key step towards a systems-level understanding of the brain-behavior relationships is to capture the dynamics of the cognitive alterations. Here, we first established in 38 healthy individuals that the day-to-day smartphone interactions can be used to inform on cognitive processing speed. Next, we analyzed the smartphone interactions in 12 patients undergoing intracranial tumor surgery, with postsurgical follow-up of up to a year. In healthy individuals, the speed of the touchscreen interactions was highly correlated to choice reaction times (R2 = 0.71) but less so to simple reaction times (R2 = 0.15) on Deary-Liewald tests. Touchscreen interactions slowed immediately after surgery but the post-surgical changes varied between patients. Data-driven models revealed the time-constant of the short-term postsurgical changes and the time taken to stabilize after the surgery. Furthermore, by using conceptually distinct types of touchscreen interaction speeds – i.e. unlocking time and app locating speed – we established that the post-surgical changes are domain-specific. Interestingly, in this small sample, the pre-surgical smartphone speeds were highly related to the speeds post-stabilization (R2 = 0.75 to 0.95). The proxy measures of cognition seamlessly captured on the smartphone can reveal postsurgical dynamics inaccessible to conventional testing. We propose that the transient cognitive alterations indicate the time-constrained influence of distinct neuronal mechanisms triggered by the surgery.

The distribution of intervals between human actions such as email posts or keyboard strokes demonstrates distinct properties at short vs long time scales. For instance, at long time scales, which are presumably controlled by complex process such as planning and decision making, it has been shown that those inter-event intervals follow a scale-invariant (or power-law) distribution. In contrast, at shorter time-scales - which are governed by different process such as sensorimotor skill - they do not follow the same distribution and little do we know how they relate to the scale-invariant pattern. Here, we analyzed 9 millions intervals between smartphone screen touches of 84 individuals which span several orders of magnitudes (from milliseconds to hours). To capture these intervals, we extend a priority-based generative model to smartphone touching events. At short-time scale, the model is governed by refractory effects, while at longer time scales, the inter-touch intervals are governed by the priority difference between smartphone tasks and other tasks. The flexibility of the model allows to capture inter-individual variations at short and long time scales while its tractability enables efficient model fitting. According to our model, each individual has a specific power-low exponent which is tightly related to the effective refractory time constant suggesting that motor processes which influence the fast actions are related to the higher cognitive processes governing the longer inter-event intervals., Comment: 11 pages, 6 figures, 1 table

Striatal dopamine has been implicated in social behavior across humans, rodents, and non-human primates in artificial laboratory settings with highly-practiced tasks and fixed reward contingencies. Whether striatal dopamine drives naturalistic, spontaneous social behavior remains unclear. Here, we leverage day-to-day logs of unconstrained smartphone behavior and establish a novel link between smartphone social activity and individual differences in striatal dopamine synthesis capacity using [18F]-DOPA PET in (N=22) healthy adult humans. We find a strong relationship such that a higher proportion of social app interactions correlates with lower dopamine synthesis capacity in the bi-lateral putamen. Permutation tests and penalized regressions provide evidence that this link between dopamine synthesis capacity and social versus non-social smartphone taps is specific. These observations provide a key empirical grounding for current speculations about dopamine’s role in digital social behavior.

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Summary Dietary interventions have not been effective in the treatment of multiple sclerosis (MS). Here, we show that periodic 3-day cycles of a fasting mimicking diet (FMD) are effective in ameliorating demyelination and symptoms in a murine experimental autoimmune encephalomyelitis (EAE) model. The FMD reduced clinical severity in all mice and completely reversed symptoms in 20% of animals. These improvements were associated with increased corticosterone levels and regulatory T (Treg) cell numbers and reduced levels of pro- inflammatory cytokines, TH1 and TH17 cells, and antigen-presenting cells (APCs). Moreover, the FMD promoted oligodendrocyte precursor cell regeneration and remyelination in axons in both EAE and cuprizone MS models, supporting its effects on both suppression of autoimmunity and remyelination. We also report preliminary data suggesting that an FMD or a chronic ketogenic diet are safe, feasible, and potentially effective in the treatment of relapsing-remitting multiple sclerosis (RRMS) patients (NCT01538355).

Body movements drop with sleep, and this behavioural signature is widely exploited to infer sleep duration. However, a reduction in body movements may also occur in periods of intense cognitive activity, and the ubiquitous use of smartphones may capture these wakeful periods otherwise hidden in the standard measures of sleep. Here, we continuously captured the gross body movements using standard wrist-worn accelerometers to quantify sleep (actigraphy) and logged the timing of the day-to-day touchscreen events (‘tappigraphy’). Using these measures, we addressed how the gross body movements overlap with the cognitively engaging digital behaviour (from n = 79 individuals, accumulating ~1400 nights). We find that smartphone use was distributed across a broad spectrum of physical activity levels, but consistently peaked at rest. We estimated the putative sleep onset and wake-up times from the actigraphy data to find that these times were well correlated to the estimates from tappigraphy (R2 = 0.9 for sleep-onset time and wake-up time). However, actigraphy overestimated sleep as virtually all of the users used their phones during the putative sleep period. Interestingly, the probability of touches remained greater than zero for ~2 h after the putative sleep onset, and ~2 h before the putative wake-up time. Our findings suggest that touchscreen interactions are widely integrated into modern sleeping habits—surrounding both sleep onset and waking-up periods—yielding a new approach to measuring sleep. Smartphone interactions can be leveraged to update the behavioural signatures of sleep with these peculiarities of modern digital behaviour.

In this paper, seven critical parameters have been identified contributing to generation shortages, and affecting the peak load demand forecasting for power system generation planning. Due to the difficulty to predict the occurrence of each parameter effectively, the time series regression models of these parameters and the peak load demand are developed using the curve fitting tool box in MATLAB. The accuracy of the developed models is evaluated through the residual, goodness of fit, and percentage errors calculated between actual and calculated data.

Unconstrained day-to-day activities are difficult to quantify and how the corresponding movements shape the brain remain unclear. Here, we recorded all touchscreen smartphone interactions at a sub-second precision and show that the unconstrained day-to-day behavior captured on the phone reflects in the simple sensorimotor computations measured in the laboratory. The behavioral diversity on the phone, the speed of interactions, the amount of social & non-social interactions, all uniquely influenced the trial-to-trial motor variability used to measure the amount of intrinsic neuronal noise. Surprisingly, both the motor performance and the early somatosensory cortical signals (assessed using EEG in passive conditions) became noisier with increased social interactions. Inter-individual differences in how people use the smartphone can help thus decompose the structure of low-level sensorimotor computations., npj Digital Medicine, 1 (1), ISSN:2398-6352

Explaining how the human brain operates in the real world remains far from the reach of modern systems and cognitive neuroscience. The brain is measured in highly controlled laboratory settings and most neuroscientific research is laser focused on explaining highly simplistic behaviours designed in the laboratory. The ubiquitous use of smartphones provides a fresh opportunity to radically reverse this trend by providing a quantitative insight into human actions in the real world. Addressing how this digital behaviour maps onto elementary neuronal measures is a powerful starting point towards appreciating the complexity of human actions.

Both voluntary and involuntary movements activate sensors in the muscles, skin, tendon and joints. As limb movement can result from a mixture of spinal reflexes and voluntary motor commands, the cortical centres underlying conscious proprioception might either aggregate or separate the sensory inputs generated by voluntary movements from those generated by involuntary movements such as spinal reflexes. We addressed whether healthy volunteers could perceive the contribution of a spinal reflex during movements that combined both reflexive and voluntary contributions. Volunteers reported the reflexive contribution in leg movements that were partly driven by the knee-jerk reflex induced by a patellar tendon tap and partly by voluntary motor control. In one condition, participants were instructed to kick back in response to a tendon tap. The results were compared to reflexes in a resting baseline condition without voluntary movement. In a further condition, participants were instructed to kick forwards after a tap. Volunteers reported the perceived reflex contribution by repositioning the leg to the perceived maximum displacement to which the reflex moved the leg after each tendon tap. In the resting baseline condition, the reflex was accurately perceived. We found a near-unity slope of linear regressions of perceived on actual reflexive displacement. Both the slope value and the quality of regression fit in individual volunteers were significantly reduced when volunteers were instructed to generate voluntary backward kicks as soon as they detected the tap. In the kick forward condition, kinematic analysis showed continuity of reflex and voluntary movements, but the reflex contribution could be estimated from electromyography (EMG) recording on each trial. Again, participants' judgements of reflexes showed a poor relation to reflex EMG, in contrast to the baseline condition. In sum, we show that reflexes can be accurately perceived from afferent information. However, the presence of voluntary movement significantly impairs reflex perception. We suggest that perceptual separation between voluntary and reflex movement is poor at best. Our results imply that the brain has no clear marker for perceptually separating voluntary and involuntary movement. Attribution of body movement to voluntary or involuntary motor commands is surprisingly poor when both are present.

Astrocytes play a crucial role in maintaining neuronal function and monitoring their activity. According to neuronal activity maps, the body is represented topographically in the somatosensory cortex. In rats, neighboring cortical areas receive forelimb (FL) and hindlimb (HL) sensory inputs. Whether astrocytic activity is also restricted to the cortical area receiving the respective peripheral sensory inputs is not known. Using wide field optical imaging we measured changes in the concentration of astrocytic calcium within the FL and HL sensorimotor cortex in response to peripheral sensory inputs. Mapping the calcium signals upon electrical stimulation of the forepaw and hindpaw we found activity largely restricted to the FL and HL area, respectively. In comparison to neuronal activity the time course of the astrocytic calcium activity was considerably slower. The signal took 6 s to peak after the onset of a 2 Hz and 2 s long electrical stimulation of the hindpaw and 8 s for a 4 s stimulation. The astrocytic signals were delayed relative to cerebral blood flow measured using laser speckle imaging. The intensity of both the astrocytic and neuronal signals in the HL sensorimotor cortex declined with increase in stimulation frequency. Moreover, blocking neuronal input by tetrodotoxin abolished astrocytic calcium signals. We suggest that the topographical representation of the body is not only true for cortical neurons but also for astrocytes. The maps and the frequency-dependent activations reflect strong reciprocal neuroglial communication and provide a new experimental approach to explore the role of astrocytes in health and disease.

As a common neuroscientific observation, the more a body part is used, the less variable the corresponding computations become. We here report a more complicated scenario concerning the fingertips of smartphone users. We sorted 21-days histories of touchscreen use of 57 volunteers into social and non-social categories. Sensorimotor variability was measured in a laboratory setting by simple button depressions and scalp electrodes (electroencephalogram, EEG). The ms range trial-to-trial variability in button depression was directly proportional to the number of social touches and inversely proportional to non-social touches. Variability of the early tactile somatosensory potentials was also proportional to the number of social touches, but not to non-social touches. The number of Apps and the speed of touchscreen use also reflected this variability. We suggest that smartphone use affects elementary computations even in tasks not involving a phone and that social activities uniquely reconfigure the thumb to touchscreen use.Impact StatementUnconstrained behavior on a smartphone is a powerful predictor of neuronal functions measured in the laboratory and the details of the smartphone-neuronal association challenges the established ideas of brain plasticity.

The capacity to inhibit actions is central to voluntary motor control. However, the control mechanisms and subjective experience involved in voluntarily stopping an involuntary movement remain poorly understood. Here we examined, in humans, the voluntary inhibition of the Kohnstamm phenomenon, in which sustained voluntary contraction of shoulder abductors is followed by involuntary arm raising. Participants were instructed to stop the involuntary movement, hold the arm in a constant position, and 'release' the inhibition after ∼2s. Participants achieved this by modulating agonist muscle activity, rather than by antagonist contraction. Specifically, agonist muscle activity plateaued during this voluntary inhibition, and resumed its previous increase thereafter. There was no discernible antagonist activation. Thus, some central signal appeared to temporarily counter the involuntary motor drive, without directly affecting the Kohnstamm generator itself. We hypothesise a form of "negative motor command" to account for this novel finding. We next tested the specificity of the negative motor command, by inducing bilateral Kohnstamm movements, and instructing voluntary inhibition for one arm only. The results suggested negative motor commands responsible for inhibition are initially broad, affecting both arms, and then become focused. Finally, a psychophysical investigation found that the perceived force of the aftercontraction was significantly overestimated, relative to voluntary contractions with similar EMG levels. This finding is consistent with the hypothesis that the Kohnstamm generator does not provide an efference copy signal. Our results shed new light on this interesting class of involuntary movement, and provide new information about voluntary inhibition of action.

Little is known about the functional role of axotomized cortical neurons that survive spinal cord injury. Large thoracic spinal cord injuries in adult rats result in impairments of hindlimb function. Using retrograde tracers, we found that axotomized corticospinal axons from the hindlimb sensorimotor cortex sprouted in the cervical spinal cord. Mapping of these neurons revealed the emergence of a new forelimb corticospinal projection from the rostral part of the former hindlimb cortex. Voltage-sensitive dye (VSD) imaging and blood-oxygen-level-dependent functional magnetic resonance imaging (BOLD fMRI) revealed a stable expansion of the forelimb sensory map, covering in particular the former hindlimb cortex containing the rewired neurons. Therefore, axotomized hindlimb corticospinal neurons can be incorporated into the sensorimotor circuits of the unaffected forelimb.

Although most spinal cord injuries are anatomically incomplete, only limited functional recovery has been observed in people and rats with partial lesions. To address why surviving fibers cannot mediate more complete recovery, we evaluated the physiological and anatomical status of spared fibers after unilateral hemisection (HX) of thoracic spinal cord in adult rats. We made intracellular and extracellular recordings at L5 (below HX) in response to electrical stimulation of contralateral white matter above (T6) and below (L1) HX. Responses from T6 displayed reduced amplitude, increased latency and elevated stimulus threshold in the fibers across from HX, beginning 1-2 weeks after HX. Ultrastructural analysis revealed demyelination of intact axons contralateral to the HX, with a time course similar to the conduction changes. Behavioral studies indicated partial recovery which arrested when conduction deficits began. In conclusion, this study is the first demonstration of the delayed decline of transmission through surviving axons to individual lumbar motoneurons during chronic stage of incomplete spinal cord injury in adult rats. These findings suggest a chronic pathological state in intact fibers and necessity for prompt treatment to minimize it.

The perceived distance between touches on the limbs is generally bigger for distances oriented across the width of the limb than for distances oriented along the length of the limb. The present study aimed to investigate the coherence of such distortions of tactile size perception across different skin surfaces. We investigated distortions of tactile size perception on the dorsal and palmar surfaces of both the left and right hands as well as the forehead. Participants judged which of two tactile distances felt larger. One distance was aligned with the proximodistal axis ( along the body), the other with the mediolateral axis ( across the body). Clear distortions were found on all five skin surfaces, with stimuli oriented across the width of the body being perceived as farther apart than those oriented along the length of the body. Consistent with previous results, distortions were smaller on the palmar than on the dorsal hand surface. Distortion on the forehead was intermediate between the dorsal and palmar surfaces. There were clear correlations between distortion on the left and right hands, for both the dorsal and palmar skin surfaces. In contrast, within each hand, there was no significant correlation between the two skin surfaces. Distortion on the forehead was not significantly correlated with that on any of the other skin surfaces. These results provide evidence for bilaterally symmetric representations underlying tactile size perception.

Neutralizing antibodies against the neurite growth inhibitory protein Nogo-A are known to induce regeneration, enhance compensatory growth, and enhance functional recovery. In intact adult rats and monkeys or spinal cord injured adult rats, antibodies reached the entire spinal cord and brain through the CSF circulation from intraventricular or intrathecal infusion sites. In the tissue, anti-Nogo antibodies were found inside Nogo-A expressing oligodendrocytes and neurons. Intracellularly, anti-Nogo-A antibodies were colocalized with endogenous Nogo-A in large organels, some of which containing the lysosomal marker cathepsin-D. This suggests antibody-induced internalization of cell surface Nogo-A. Total Nogo-A tissue levels in spinal cord were decreased in intact adult rats following 7 days of antibody infusion. This mechanism was confirmed in vitro; cultured oligodendrocytes and neurons had lower Nogo-A contents in the presence of anti-Nogo-A antibodies. These results demonstrate that antibodies against a CNS cell surface protein reach their antigen through the CSF and can induce its downregulation.

Cortical activity allotted to the tactile receptors on fingertips conforms to skilful use of the hand [1, 2 and 3]. For instance, in string instrument players, the somatosensory cortical activity in response to touch on the little fingertip is larger than that in control subjects [1]. Such plasticity of the fingertip sensory representation is not limited to extraordinary skills and occurs in monkeys trained to repetitively grasp and release a handle as well [4]. Touchscreen phones also require repetitive finger movements, but whether and how the cortex conforms to this is unknown. By using electroencephalography (EEG), we measured the cortical potentials in response to mechanical touch on the thumb, index, and middle fingertips of touchscreen phone users and nonusers (owning only old-technology mobile phones). Although the thumb interacted predominantly with the screen, the potentials associated with the three fingertips were enhanced in touchscreen users compared to nonusers. Within the touchscreen users, the cortical potentials from the thumb and index fingertips were directly proportional to the intensity of use quantified with built-in battery logs. Remarkably, the thumb tip was sensitive to the day-to-day fluctuations in phone use: the shorter the time elapsed from an episode of intense phone use, the larger the cortical potential associated with it. Our results suggest that repetitive movements on the smooth touchscreen reshaped sensory processing from the hand and that the thumb representation was updated daily depending on its use. We propose that cortical sensory processing in the contemporary brain is continuously shaped by the use of personal digital technology.

Involuntary movements such as spontaneous eye blinks can be successfully inhibited at will. Little do we know how the voluntary motor circuits countermand spontaneous blinks. Do the voluntary inhibitory commands act to pause or to turn off the endogenous blink generator, or does inhibition intersect and counter the generator׳s excitatory outputs? In theory, the time taken for the system to generate an after-inhibition blink will reflect onto the form of inhibition. For instance, if voluntary commands were to turn the blink generator off then the after-blink latency would be fixed to the inhibition offset and reflect the time it takes for the generator to rebound and turn on. In this study we measured the after-blink latency from the offset of voluntary inhibition. Volunteers inhibited their blinks in response to sound tones of randomly varying durations. At the offset volunteers withdrew the inhibition and relaxed. Interestingly, the spontaneous after-blinks were fixed to the offset of the inhibition as if the generator rebounded from an off state. The after-blink latency was not related to the duration of the inhibition, and inhibiting even for a small fraction of the mean inter-blink interval generated an after-blink time-locked to the inhibition offset. Interestingly, the insertion of voluntary blinks after inhibition further altered the blink generator by delaying the spontaneous after-blinks. We propose that the inhibition of spontaneous blinks at the level of the generator allows for highly effective voluntary countermanding. Nevertheless, the withdrawal of such inhibition was strongly associated with motor excitation.

A hallmark of voluntary motor control is the ability to stop an ongoing movement. Is voluntary motor inhibition a general neural mechanism that can be focused on any movement, including involuntary movements, or is it mere termination of a positive voluntary motor command? The involuntary arm lift, or ‘floating arm trick’, is a distinctive long-lasting reflex of the deltoid muscle. We investigated how a voluntary motor network inhibits this form of involuntary motor control. Transcranial magnetic stimulation of the motor cortex during the floating arm trick produced a silent period in the reflexively contracting deltoid muscle, followed by a rebound of muscle activity. This pattern suggests a persistent generator of involuntary motor commands. Instructions to bring the arm down voluntarily reduced activity of deltoid muscle. When this voluntary effort was withdrawn, the involuntary arm lift resumed. Further, voluntary motor inhibition produced a strange illusion of physical resistance to bringing the arm down, as if ongoing involuntarily generated commands were located in a ‘sensory blind-spot’, inaccessible to conscious perception. Our results suggest that voluntary motor inhibition may be a specific neural function, distinct from absence of positive voluntary motor commands.

Plastic interactions between face and hand cortical tactile circuits occur after severe injuries that affect the hand such as in amputation or spinal cord injury. However, whether loss of facial movements alters the cortical circuits involved in processing tactile inputs from the hand remains unknown. In this prospective observational study we used electroencephalography (EEG) to measure cortical activity evoked by tactile stimulation of the hands before and after botulinum toxin-A-induced facial paralysis. We found a reduction in the tactile event-related potentials (ERPs) 6 weeks after the treatment. This suggests that the limited paralysis of facial muscles induced during cosmetic interventions designed to smooth lines and wrinkles on the face is sufficient to alter the cortical processing of tactile inputs from the hand., Annals of Clinical and Translational Neurology, 1 (1), ISSN:2328-9503

Thoracic spinal cord injured rats rely largely on forelimbs to walk, as their hindlimbs are dysfunctional. This increased limb use is accompanied by expansion of the cortical forelimb sensory representation. It is unclear how quickly the representational changes occur and whether they are at all related to the behavioral adaptation. Using blood oxygenation level dependent functional mangetic resonance imaging (BOLD-fMRI) we show that major plastic changes of the somato-sensory map can occur as early as one day after injury. The extent of map increase was variable between animals, and some animals showed a reduction in map size. However, at three or seven days after injury a significant enhancement of the forelimb representation was evident in all the animals. In a behavioral test for precise limb control, crossing of a horizontal ladder, the injured rats relied almost entirely on their forelimbs; they initially made more mistakes than at 7 days post injury. Remarkably, in the individual animals the behavioral performance seen at seven days was proportional to the physiological change present at one day after injury. The rapid increase in cortical representation of the injury-spared body part may provide the additional neural substrate necessary for high level behavioral adaptation.

Cerebral Cortex, 22 (6), ISSN:1047-3211, ISSN:1460-2199

A lateral hemisection injury of the cervical spinal cord results in Brown-Séquard syndrome in humans and rats. The hands/forelimbs on the injured side are rendered permanently impaired, but the legs/hindlimbs recover locomotor functions. This is accompanied by increased use of the forelimb on the uninjured side. Nothing is known about the cortical circuits that correspond to these behavioral adaptations. In this study, on adult rats with cervical spinal cord lateral hemisection lesions (at segment C3/4), we explored the sensory representation and corticospinal projection of the intact (ipsilesional) cortex. Using blood oxygenation level-dependent functional magnetic resonance imaging and voltage-sensitive dye (VSD) imaging, we found that the cortex develops an enhanced representation of the unimpaired forepaw by 12 weeks after injury. VSD imaging also revealed the cortical spatio-temporal dynamics in response to electrical stimulation of the ipsilateral forepaw or hindpaw. Interestingly, stimulation of the ipsilesional hindpaw at 12 weeks showed a distinct activation of the hindlimb area in the intact, ipsilateral cortex, probably via the injury-spared spinothalamic pathway. Anterograde tracing of corticospinal axons from the intact cortex showed sprouting to recross the midline, innervating the spinal segments below the injury in both cervical and lumbar segments. Retrograde tracing of these midline-crossing axons from the cervical spinal cord (at segment C6/7) revealed the formation of a new ipsilateral forelimb representation in the cortex. Our results demonstrate profound reorganizations of the intact sensory-motor cortex after unilateral spinal cord injury. These changes may contribute to the behavioral adaptations, notably for the recovery of the ipsilesional hindlimb.