Environmentally Tolerant Ionic Hydrogel with High Power Density for Low-Grade Heat Harvesting.

Harvesting low-grade heat by an ionic hydrogel thermoelectric generator (ITEG) into useful electricity is promising to power flexible electronics. However, the poor environmental tolerance of the ionic hydrogel limits its application. Herein, we demonstrate an ITEG with high thermoelectric properties, as well as excellent capabilities of water retention, freezing resistance, and self-regeneration. The obtained ITEG can maintain the original water content at ambient conditions (302 K, 65% relative humidity (RH)) for 7 days and keep unfreezing at a low temperature (253 K). It can even be self-regenerated and recovered to its original state after a water loss in high-temperature conditions. Furthermore, a high ionic Seebeck coefficient of 11.3 mV K-1 and an impressive power density of 167.90 mW m-2 are achieved under a temperature difference of 20 K. A high power density of 60.00 mW m-2 can also be maintained even at 258 K. After drying and regeneration, ITEG-re could even exhibit a higher ionic Seebeck coefficient of 11.8 mV K-1. Successful lighting of light-emitting diodes (LEDs) and charging of capacitors demonstrate the great potential of ITEG to provide continuous energy supply for powering flexible electronics.

Coal and gangue identification method based on the intensity image of lidar and DenseNet.

Coal and gangue (rock) identification is the essential process in a coal preparation plant. In an actual coal preparation plant, the existing classification methods have many disadvantages in safety and identification rate. We utilized the echo intensity image (EII) of lidar for coal and gangue identification for the first time, to the best of our knowledge, and achieved outstanding recognition results with a convolutional neural network. First, we acquire the information of the 3D point cloud, including the distance and the echo intensity, and decompose them into two channels. Then, we utilize the distance channel to remove the background noises and separate the object and the echo intensity channel to construct the 2D EII. Finally, we prune the dense convolutional network (DenseNet-121) to DenseNet-40 for the real-time identification and compare its F1 score with the other two traditional recognition algorithms. The experiment shows that the F1 score of the DenseNet-40 is up to 0.96, which indicates the DenseNet-40 is provably higher than other traditional algorithms in accuracy. Through trial and error, we find that the echo intensity of lidar can clearly show the texture information of coal and gangue. After combining with the DenseNet-40, it has more benefits than the existing classification methods in accuracy, efficiency, and robustness.

Age and multiparity related urethral sphincter muscle dysfunction in a rabbit model: Potential roles of TGF-ß and Wnt-ß catenin signaling pathways.

AIMS: Prior studies demonstrate increased incidence of urinary incontinence (UI) in the geriatric population which affects their quality of life. Pathophysiology of UI in the geriatric population and the underlying molecular mechanisms are still unclear. To elucidate these mechanisms, we performed a pre-clinical study in a rabbit model and the objectives were to (i) determine the effect of aging as well as multiparity on urethral sphincter muscle thickness and urethral closing pressure (UCP); (ii) examine the role of fibrosis and atrophy; and (iii) elucidate the molecular pathways that mediate fibrosis and atrophy in the urethral tissue. METHODS: New Zealand White female rabbits (n = 6 each; young 6-12 months and old over 30 months of age) were anesthetized and urethral muscle thickness and sphincter closure function were measured. Rabbits were then sacrificed and urethral tissues (bladder neck and mid-urethra) were collected to process for immunostaining as well as for molecular studies for markers for fibrosis (ß-catenin which is an important mediator of Wnt signaling, Collagen-1, and TGF-ß) and atrophy (MuRF-1). RESULTS: Our studies showed a significant decrease in the urethral sphincter muscle thickness and closure function with age. Age-related increase in protein and mRNA expression levels of fibrosis, as well as atrophy markers were observed in the bladder neck and mid-urethral tissues. CONCLUSIONS: Age and multiparity related increase in fibrosis and atrophy of urethral sphincter muscles may contribute to impaired urethral closure function seen in old animals.

Prolonged human neural stem cell maturation supports recovery in injured rodent CNS.

Neural stem cells (NSCs) differentiate into both neurons and glia, and strategies using human NSCs have the potential to restore function following spinal cord injury (SCI). However, the time period of maturation for human NSCs in adult injured CNS is not well defined, posing fundamental questions about the design and implementation of NSC-based therapies. This work assessed human H9 NSCs that were implanted into sites of SCI in immunodeficient rats over a period of 1.5 years. Notably, grafts showed evidence of continued maturation over the entire assessment period. Markers of neuronal maturity were first expressed 3 months after grafting. However, neurogenesis, neuronal pruning, and neuronal enlargement continued over the next year, while total graft size remained stable over time. Axons emerged early from grafts in very high numbers, and half of these projections persisted by 1.5 years. Mature astrocyte markers first appeared after 6 months, while more mature oligodendrocyte markers were not present until 1 year after grafting. Astrocytes slowly migrated from grafts. Notably, functional recovery began more than 1 year after grafting. Thus, human NSCs retain an intrinsic human rate of maturation, despite implantation into the injured rodent spinal cord, yet they support delayed functional recovery, a finding of great importance in planning human clinical trials.

Neural stem cells in models of spinal cord injury.

Replication of published studies is an important and respected aspect of the conduct of science. Most would argue that the interpretation of "negative" outcomes is still more challenging than the interpretation of "positive" findings, however, due to uncertainty in knowing precisely why a hypothesized outcome was not observed: in particular, are "negative" findings in replication studies a result of invalidity of the original experimental hypothesis, or due to a methodological failure, insensitivity of the applied instruments of analysis, or other factors? These points must be carefully considered. Steward and colleagues report findings of a study in which multipotent neural progenitor cells were grafted to sites of T3 complete transection. Unlike our study, cells failed to fill the lesion site, leaving collagenous rifts between rostral and caudal graft components. This "anatomical" failure precluded formation of neural relays across the lesion site, and was predictably associated with a failure to detect functional improvement. In summarizing outcomes of the study, Steward and colleagues did not clearly link the failure to achieve graft continuity in the lesion cavity with functional outcomes, despite the central role of this observation in cogently interpreting results of the replication study. In addition, the authors stated that they failed to replicate our report of "extensive" host axonal regeneration into grafts, but we did not report "extensive" host anatomical regeneration; moreover, underexposed images may have contributed to Steward's underestimation of host axonal penetration. The authors also stated that our original study excluded some animals from functional analysis, and this is incorrect. While replication studies are important and necessary, this particular report contained several errors, and the failure to form a continuous neural progenitor cell bridge across the lesion site limited the ability to conclude whether continuous grafts can restore function. In subsequent experiments we too have observed rift formation in animals grafted at long delays (>2weeks) after SCI, and we confirm that animals with rifts do not exhibit functional improvement; we are developing methods to remove or prevent rift formation. The replication study confirmed the cardinal finding of our original report: that early-stage neural precursors extend very large numbers of axons over remarkably long distances through the lesioned adult spinal cord.

Long-distance axonal growth from human induced pluripotent stem cells after spinal cord injury.

Human induced pluripotent stem cells (iPSCs) from a healthy 86-year-old male were differentiated into neural stem cells and grafted into adult immunodeficient rats after spinal cord injury. Three months after C5 lateral hemisections, iPSCs survived and differentiated into neurons and glia and extended tens of thousands of axons from the lesion site over virtually the entire length of the rat CNS. These iPSC-derived axons extended through adult white matter of the injured spinal cord, frequently penetrating gray matter and forming synapses with rat neurons. In turn, host supraspinal motor axons penetrated human iPSC grafts and formed synapses. These findings indicate that intrinsic neuronal mechanisms readily overcome the inhibitory milieu of the adult injured spinal cord to extend many axons over very long distances; these capabilities persist even in neurons reprogrammed from very aged human cells.

Promotion of survival and differentiation of neural stem cells with fibrin and growth factor cocktails after severe spinal cord injury.

Neural stem cells (NSCs) can self-renew and differentiate into neurons and glia. Transplanted NSCs can replace lost neurons and glia after spinal cord injury (SCI), and can form functional relays to re-connect spinal cord segments above and below a lesion. Previous studies grafting neural stem cells have been limited by incomplete graft survival within the spinal cord lesion cavity. Further, tracking of graft cell survival, differentiation, and process extension had not been optimized. Finally, in previous studies, cultured rat NSCs were typically reported to differentiate into glia when grafted to the injured spinal cord, rather than neurons, unless fate was driven to a specific cell type. To address these issues, we developed new methods to improve the survival, integration and differentiation of NSCs to sites of even severe SCI. NSCs were freshly isolated from embryonic day 14 spinal cord (E14) from a stable transgenic Fischer 344 rat line expressing green fluorescent protein (GFP) and were embedded into a fibrin matrix containing growth factors; this formulation aimed to retain grafted cells in the lesion cavity and support cell survival. NSCs in the fibrin/growth factor cocktail were implanted two weeks after thoracic level-3 (T3) complete spinal cord transections, thereby avoiding peak periods of inflammation. Resulting grafts completely filled the lesion cavity and differentiated into both neurons, which extended axons into the host spinal cord over remarkably long distances, and glia. Grafts of cultured human NSCs expressing GFP resulted in similar findings. Thus, methods are defined for improving neural stem cell grafting, survival and analysis of in vivo findings.

Long-distance growth and connectivity of neural stem cells after severe spinal cord injury.

Neural stem cells (NSCs) expressing GFP were embedded into fibrin matrices containing growth factor cocktails and grafted to sites of severe spinal cord injury. Grafted cells differentiated into multiple cellular phenotypes, including neurons, which extended large numbers of axons over remarkable distances. Extending axons formed abundant synapses with host cells. Axonal growth was partially dependent on mammalian target of rapamycin (mTOR), but not Nogo signaling. Grafted neurons supported formation of electrophysiological relays across sites of complete spinal transection, resulting in functional recovery. Two human stem cell lines (566RSC and HUES7) embedded in growth-factor-containing fibrin exhibited similar growth, and 566RSC cells supported functional recovery. Thus, properties intrinsic to early-stage neurons can overcome the inhibitory milieu of the injured adult spinal cord to mount remarkable axonal growth, resulting in formation of new relay circuits that significantly improve function. These therapeutic properties extend across stem cell sources and species.

Motor axonal regeneration after partial and complete spinal cord transection.

We subjected rats to either partial midcervical or complete upper thoracic spinal cord transections and examined whether combinatorial treatments support motor axonal regeneration into and beyond the lesion. Subjects received cAMP injections into brainstem reticular motor neurons to stimulate their endogenous growth state, bone marrow stromal cell grafts in lesion sites to provide permissive matrices for axonal growth, and brain-derived neurotrophic factor gradients beyond the lesion to stimulate distal growth of motor axons. Findings were compared with several control groups. Combinatorial treatment generated motor axon regeneration beyond both C5 hemisection and T3 complete transection sites. Yet despite formation of synapses with neurons below the lesion, motor outcomes worsened after partial cervical lesions and spasticity worsened after complete transection. These findings highlight the complexity of spinal cord repair and the need for additional control and shaping of axonal regeneration.

Pranlukast prevents cysteinyl leukotriene-induced emesis in the least shrew (Cryptotis parva).

Many chemotherapeutic agents activate multiple signaling systems, including potentially emetogenic arachidonic acid metabolites. Of these messengers, the emetic role of the leukotriene family has been neglected. The aims of this study were to test the emetic potential of key leukotrienes (LTA(4), LTB(4), LTF(4), and the cysteinyl leukotrienes LTC(4), LTD(4) and LTE(4)), and to investigate whether the leukotriene CysLT(1) receptor antagonist pranlukast or mixed leukotriene CysLT(1/2) receptor antagonist Bay u9773 can prevent the LTC(4)-induced emesis. Least shrews were injected with varying doses of one of the six tested leukotrienes and vomiting parameters were measured for 30min. LTC(4) and LTD(4) were most efficacious, and significantly increased both the frequency and percentage of animals vomiting at doses from 0.1 and 0.05mg/kg, respectively. The other tested leukotrienes were either weakly emetic or ineffective at doses up to 4mg/kg. The relative emetogenic activities of the cysteinyl leukotrienes (LTC(4)=LTD(4)>LTE(4)) suggest that leukotriene CysLT(2) receptors have a key role in emesis. However, pranlukast dose-dependently, and at 10mg/kg completely, blocked LTC(4)-induced vomiting, implicating a leukotriene CysLT(1) receptor-mediated emetic effect. Bay u9773 dose-dependently reduced the percentage of animals vomiting, but did not significantly reduce vomiting frequency. Fos immunoreactivity, measured subsequent to LTC(4)-induced vomiting to define its putative anatomical substrates, was significantly increased in the enteric nervous system and medullary dorsal vagal complex following LTC(4) (P<0.05) versus vehicle injections. This study is the first to show that some leukotrienes induce emesis, possibly involving both central and peripheral leukotriene CysLT(1) and/or leukotriene CysLT(2) receptors.

The antiemetic interaction of Delta9-tetrahydrocannabinol when combined with tropisetron or dexamethasone in the least shrew.

5-HT3 receptor antagonists (e.g. tropisetron) combined with dexamethasone are effective for the acute phase of cisplatin (CIS)-induced emesis. This study determined the possible additive or synergistic antiemetic efficacy of Delta9-THC when combined with tropisetron or dexamethasone (DEX). Delta9-THC (0-10 mg/kg i.p.) was injected in combination with tropisetron (0-5 mg/kg i.p.) or dexamethasone (0-20 mg/kg i.p.) prior to CIS (20 mg/kg i.p.) in the least shrew, and the induced emesis was recorded for 60 min. CIS-induced vomiting was dose-dependently and significantly attenuated by individual administration of Delta9-THC (59-97% reductions) and tropisetron (79-100% attenuation), but not dexamethasone (26-40%), although a trend (p<0.1) towards reduced vomiting frequency following DEX was noted. Low doses of Delta9-THC (0.25 or 0.5 mg/kg) when combined with low doses of tropisetron (0.025, 0.1, or 0.25 mg/kg) were more efficacious in reducing emesis frequency than when given individually, but Delta9-THC had no antiemetic interactions with DEX. However, no tested combination provided a significantly greater effect on the number of animals vomiting than their individually-administered counterparts. The modest interaction of Delta9-THC with tropisetron suggests they activate overlapping antiemetic mechanisms, while the lack of interaction with dexamethasone needs further clarification.

Utilization of the least shrew as a rapid and selective screening model for the antiemetic potential and brain penetration of substance P and NK1 receptor antagonists.

Substance P (SP) is thought to play a cardinal role in emesis via the activation of central tachykinin NK1 receptors during the delayed phase of vomiting produced by chemotherapeutics. Although the existing supportive evidence is significant, due to lack of an appropriate animal model, the evidence is indirect. As yet, no study has confirmed that emesis produced by SP or a selective NK1 receptor agonist is sensitive to brain penetrating antagonists of either NK1, NK2, or NK3 receptors. The goals of this investigation were to demonstrate: 1) whether intraperitoneal (i.p.) administration of either SP, a brain penetrating (GR73632) or non-penetrating (e.g. SarMet-SP) NK1 receptor agonist, an NK2 receptor agonist (GR64349), or an NK3 receptor agonist (Pro7-NKB), would induce vomiting and/or scratching in the least shrew (Cryptotis parva) in a dose-dependent manner; and whether these effects are sensitive to the above selective receptor antagonists; 2) whether an exogenous emetic dose of SP (50 mg/kg, i.p.) can penetrate into the shrew brain stem and frontal cortex; 3) whether GR73632 (2.5 mg/kg, i.p.)-induced activation of NK1 receptors increases Fos-measured neuronal activity in the neurons of both brain stem emetic nuclei and the enteric nervous system of the gut; and 4) whether selective ablation of peripheral NK1 receptors can affect emesis produced by GR73632. The results clearly demonstrated that while SP produced vomiting only, GR73632 caused both emesis and scratching behavior dose-dependently in shrews, and these effects were sensitive to NK1-, but not NK2- or NK3-receptor antagonists. Neither the selective, non-penetrating NK1 receptor agonists, nor the selective NK2- or NK3-receptor agonists, caused a significant dose-dependent behavioral effect. An emetic dose of SP selectively and rapidly penetrated the brain stem but not the frontal cortex. Systemic GR73632 increased Fos expression in the enteric nerve plexi, the medial subnucleus of nucleus tractus solitarius, and the dorsal motor nucleus of the vagus, but not the area postrema. Ablation of peripheral NK1 receptors attenuated the ability of GR73632 to induce a maximal frequency of emesis and shifted its percent animals vomiting dose-response curve to the right. The NK1-ablated shrews exhibited scratching behavior after systemic GR73632-injection. These results, for the first time, affirm a cardinal role for central NK1 receptors in SP-induced vomiting, and a facilitatory role for gastrointestinal NK1 receptors. In addition, these data support the validation of the least shrew as a specific and rapid behavioral animal model to screen concomitantly both the CNS penetration and the antiemetic potential of tachykinin NK1 receptor antagonists.

Effects of temporary bilateral ligation of the internal carotid arteries on the low- and high-frequency somatic evoked potentials in the swine.

OBJECTIVE: We studied effects of a temporary bilateral ligation of the internal carotid arteries on the subcortical and cortical structures of the somatosensory system by examining the thalamic input and postsynaptic cortical responses contained in the somatic evoked potentials (SEPs) recorded from the primary somatosensory cortex (SI) of the juvenile piglets in vivo. We predicted that the ligation should differentially affect these structures due to differences in blood supply. METHODS: The SEPs between 1 and 3000 Hz were measured in the SI cortex with a multichannel electrode array before, during and after a 20 min bilateral ligation of the internal carotid arteries in the swine under a barbiturate anesthesia. RESULTS: The ligation differentially affected the thalamic input and the cortical responses contained in the high-frequency signals (HFSs) between 400 and 2000 Hz. The amplitude of the thalamic input did not change, but the amplitudes of the cortical HFS postsynaptic to the thalamic inputs decreased immediately after start of ligation, recovering over the next 30-90 min. The latency showed a small, but significant increase for several minutes after the start of ligation for both the thalamic input and cortical responses. The ligation increased the latency and reduced the amplitude of the peak of the first cortical response in the wideband SEP corresponding to human N20. CONCLUSIONS: The HFS is useful for distinguishing selective effects of the temporary ligation on the subcortical and cortical structures of the somatosensory system. Since the porcine N20 starts after the presynaptic HFS, it was not useful in differentiating thalamic and cortical effects. SIGNIFICANCE: The HFS may open a new window in studying the cortical physiology in humans.

Evaluation of the distortion of EEG signals caused by a hole in the skull mimicking the fontanel in the skull of human neonates.

OBJECTIVE: Interpretation of Electroencephalography (EEG) signals from newborns is in some cases difficult because the fontanels and open sutures produce inhomogeneity in skull conductivity. We experimentally determined how EEG is influenced by a hole mimicking the anterior fontanel since distortion of EEG signals is important in neurological examinations during the perinatal period. METHODS: Experiments were carried out on 10 anesthetized farm swine. The fontanel was mimicked by a hole (12 x 12 mm) in the skull. The hole was filled with 3 types of medium differing in conductivity (air, 0 S/m; sucrose-agar, 0.017 S/m; saline-agar, 1.28 S/m). Three positions of the snout were stimulated with a concentric bipolar electrode to activate cortical areas near the middle, the edge, and the outside of the hole. The somatic-evoked potential (SEP) was recorded by a 4 x 4 electrode array with a 4mm grid spacing. It was placed on the 4 quadrants of a 28 x 28 mm measurement area on a saline-soaked filter paper over the skull, which served as artificial scalp. RESULTS: The SEP over the hole was clearly stronger when the hole was filled with sucrose- or saline-agar as compared to air, although paradoxically the leakage current was stronger for the sucrose- than saline-agar. The current leaking from the hole was strongly related to position of the active tissue. It was nearly negligible for sources 6-10 mm away from the border of the hole. The distortion was different for 3 components of the SEP elicited by each stimulus, probably indicating effects of source distance relative to the hole. CONCLUSIONS: EEG is strongly distorted by the presence of a hole/fontanel with the distortion specifically dependent on both conductivity of the hole and source location. SIGNIFICANCE: The distortion of the EEG is in contrast to the lack of distortion of magnetoencephalography (MEG) signals shown by previous studies. In studying brain development with EEG, the infant's head and sources should be modeled accurately in order to relate the signals to the underlying activity. MEG may be particularly advantageous over EEG for studying brain functions in infants since it is relatively insensitive to skull defects.

Origins of the somatic N20 and high-frequency oscillations evoked by trigeminal stimulation in the piglets.

OBJECTIVE: In humans, the somatic evoked potentials (SEPs) and magnetic fields (SEFs) elicited by peripheral nerve stimulation contain high-frequency oscillations (HFOs) around 600 Hz superimposed on the initial cortical response N20. Responses elicited by snout stimulation in the swine also contain similar HFOs during the rising phase of the porcine N20. This study examined the generators of the N20 and HFOs in the swine. METHODS: We recorded intracortical SEPs and multi-unit activities in the sulcal area of the primary somatosensory cortex (SI) simultaneously with SEFs. The laminar profiles of the potential and current-source-density (CSD) were analyzed. RESULTS: The CSD analysis revealed that the N20 was produced by two dipolar generators, both directed toward the cortical surface. After the arrival of the initial thalamocortical volley in layer IV, the sink of the first generator shifted toward shallower layers II-III with a velocity of 0.109+/-0.038 m/s (mean+/-SD). The sink of the second generator moved to layer V. The initial thalamocortical axonal component of the HFO was produced by repolarizing current with the sink in layer IV. The CSD laminar profile of the postsynaptic component was very similar to the profile of intracortical N20. The current sink within each cycle of HFO propagated upward with a velocity of 0.633+/-0.189 m/s, indicating backpropagation. CONCLUSIONS: We propose that the N20 is generated by two sets of excitatory neurons which also produce the HFOs. Although the loci of synaptic inputs are unknown, these neurons appear to fire initially in the soma and produce backpropagating spikes toward distal apical dendrites. SIGNIFICANCE: These conclusions relate the N20 to the HFO and provide a new explanation of how the current underlying the N20 is invariantly directed toward superficial layers across species.

Depressed cortical excitability and elevated matrix metalloproteinases in remote brain regions following intracerebral hemorrhage.

The absence of cortical responses to external stimuli is a dubious clinical sign during the first 1-2 days of brain injury. We previously showed that the amplitude of the somatic evoked potential (SEP) in the swine is diminished at the infarct site and perihematomal surround within the first 6 h of collagenase-induced intracerebral hemorrhage (ICH). We now report that this depressed SEP persists during the subchronic (48 h) period of ICH in the swine not only within the injured primary somatosensory (SI) cortex, but also in the contralateral homotopic SI cortex. This impairment of sensory responsiveness was accompanied by increases in various matrix metalloproteinases (MMPs) in different brain regions. By 24 h, a marked rise in MMP-9, an inflammatory marker, was detected in the white matter of the ipsilesional SI and secondary somatosensory cortex (SII), and in the contralesional SI gray matter, as compared to saline-injected controls. A subsequent increase in MMP-9 level was found in the ipsilesional SI and SII gray matter, and in the contralesional SI white matter by 48 h (P<0.05). By 7 days, significant levels of MMP-9 were detected only in the ipsilesional SI white and gray matter tissues. In contrast, the elevation of MMP-2, a marker of degeneration, was delayed until 7 days post-ICH in the ipsilesional SII gray matter. A significant rise in MMP-9 was also noted in CA1 of the ipsilesional and contralesional hemispheres during 1-2 days. Our MMP assay shows that the depressed cortical excitability seen in the contralateral SI cortex is a manifestation of the broad effect of a focal ICH that produces inflammatory and degenerative processes not only in the region adjacent to the focal ICH site, but also in remote regions that are functionally connected to the site of focal ICH.

Stable synchronized high-frequency signals from the main sensory and spinal nuclei of the pig activated by Abeta fibers of the maxillary nerve innervating the snout.

The primary somatosensory cortex of various species including man, monkey, pig and rat is capable of producing high-frequency signals in the 600 Hz range and above with very little latency jitter. We have recently observed such cortical signals for the trigeminal system of the swine. This study determined the projection of the maxillary nerve innervating the snout to the sensory trigeminal nuclear complex in the brain stem and stability of outputs of each nucleus receiving the projection. The snout stimulation activated large-caliber Abeta fibers in the trigeminal nerve with a mean velocity of 64.4+/-2.7 m/s (mean+/-1 S.E.M., six animals) comparable in velocity to the tooth pulp Abeta fibers (57.9+/-3.4 m/s) obtained from the same animals. These afferents activated the main sensory nucleus, and subnuclei oralis, interpolaris and caudalis of the spinal nucleus, as judged by evoked field potential maps superimposed on the histological maps of the trigeminal nuclei from the same animals. Inputs from these fast afferents arrived at all the four trigeminal nuclei almost simultaneously within a span of 0.7+/-0.2 ms (mean+/-1 S.D., seven animals). Evoked high-frequency signals were reproducible with a latency jitter of less than 0.2 ms during the first 4 ms of postsynaptic activity for each of main sensory and spinal nuclei. These results indicate that the snout stimulation activates fast-conducting peripheral afferents which project to all the sensory trigeminal nuclei and produces highly reproducible initial responses nearly simultaneously across the multiple trigeminal nuclei. These outputs from the trigeminal nuclei may play an important role in triggering the stable high-frequency signals in the cortex.

Synchronized spikes of thalamocortical axonal terminals and cortical neurons are detectable outside the pig brain with MEG.

We show that it is feasible to monitor the synchronized population spikes of the thalamocortical axonal terminals and cortical neurons outside the brain using high-resolution magnetoencephalography (MEG). Electrical stimulation of the snout elicited somatic-evoked magnetic fields (SEFs) above the primary somatosensory cortex (SI) of the piglet. The SEFs contained high-frequency oscillations (HFOs) around 600 Hz similar in many respects to the noninvasively measured HFOs from humans with MEG and electroencephalography (EEG). These HFOs were highly correlated with those in simultaneously measured intracortical somatic-evoked potentials (SEPs) in the snout projection area in SI. Both HFOs in SEFs and SEPs consisted of an initial component insensitive to cortically injected kynurenic acid (Kyna, 20 mM), a nonspecific antagonist of glutamatergic receptors, and a subsequent Kyna-sensitive component. The former was localized in cortical layer IV, indicating that it was due to spikes produced by the specific thalamocortical axonal terminals, whereas the latter was initially localized in layer IV and subsequently in the superficial and deeper layers. These results suggest that it may be possible to study properties of the thalamocortical and cortical spike activities in humans with MEG.