Brain Research

Associative memory, the ability to bind and retrieve relationships between unrelated elements, is a cornerstone of human cognition and a primary target for neurorehabilitation. Vagus nerve stimulation (VNS) has emerged as a promising method to modulate the locus coeruleus-norepinephrine (LC-NE) system and hippocampal-prefrontal circuits essential for memory. However, the comparative efficacy of non-invasive modalities such as electrical (E-taVNS) and the emerging field of ultrasound (U-taVNS) remains poorly understood in the context of active recall. In this study, participants performed a crossmodal video-word associative memory task before and after receiving either E-taVNS or U-taVNS in active and sham conditions. We investigated whether these modalities enhance cued recall accuracy and retrieval reaction time. Our results revealed that neither E-taVNS nor U-taVNS significantly improved recall accuracy. However, E-taVNS significantly accelerated response times specifically for correctly recalled items. These findings suggest that while taVNS may not increase the likelihood of recalling associative memories, electrical stimulation may enhances the efficiency in which we do so. These findings suggest that electrical taVNS is a viable tool for facilitating memory search processes, though further research is required to optimize ultrasound parameters and validate mechanistic pathways through physiological monitoring.

Transcutaneous spinal cord stimulation (tSCS) of the cervical spinal cord has been thought to modulate lumbar networks, leading to the hypothesis that leg muscle recruitment may occur via recruitment of long-range spinal connections between cervical and lumbar circuits. To directly test this hypothesis, we compared arm and leg muscle responses elicited in unimpaired participants (N = 12) by cervical tSCS with the anodes placed over the iliac crests, with the anodes placed over the clavicles, and with lumbar tSCS as a control for leg muscle recruitment via the posterior root-muscle reflex. The idea of tSCS targeting cervico-lumbar connectivity would suggest that cervical stimulation could evoke responses in leg muscles. However, in our experiments, leg responses via cervical tSCS were only observed when the anodes were placed over the iliac crests, but not over the clavicles. These leg muscle responses had shorter latencies than those with lumbar tSCS and showed minimal post-activation depression, indicating efferent rather than afferent recruitment. Therefore, changes in leg muscle excitability by cervical-iliac tSCS previously attributed to descending cervical circuits could instead be explained by direct recruitment of efferent fibers near the iliac anodes. These findings suggest that cervical tSCS alone does not engage leg muscle motoneurons via long-range spinal or bidirectional pathways. Therefore, our study highlights the need to carefully consider electrode configuration when interpreting cervical tSCS mechanisms and additional or unexpected rehabilitative effects that extend caudally from the cervical spinal cord.

Mental fatigue (MF) arises from sustained cognitive load and produces a multisystem signature spanning subjective experience, task performance, cortical oscillations, and oculomotor dynamics. It may alter higher-order cognitive functions essential to everyday life, underscoring the need for preventive strategies. Although moderate aerobic exercise (EXO) facilitates recovery from MF, its influence on the onset and expression of MF when performed beforehand remains unexplored. This study provided a multimodal characterization of MF, assessed its impact on associative memory and divergent creativity, and examined whether prior EXO modulated these outcomes. Twenty-nine participants completed either 15 min of EXO or rest before a 35-min MF-inducing Time Load Dual Back task. Subjective fatigue and effort, performance, EEG activity, and eye-blink rate were continuously recorded; associative memory and divergent creativity were assessed pre-intervention and post-MF. Both groups showed progressive increases in MF and effort from 7 min onward, stable performance, and a rise in parieto-central alpha power at 18 min. The EXO group exhibited higher frontal-medial theta power and stable blink rates, whereas blink rate in REST increased at 21 min. EXO did not prevent subjective MF nor influence behavioral stability but modulated neurophysiological markers potentially related to compensatory control and dopaminergic regulation. Associative memory remained preserved in both groups, whereas creative flexibility increased in REST but not EXO, suggesting MF-related disinhibition in the former and preserved inhibitory control in the latter. These findings refine temporal and multimodal profile of MF and highlight the need to optimize exercise parameters and task demands to enhance preventive efficacy and guide interventions.

Traumatic brain injury (TBI) induces a series of neuropathological changes in the brain including neurogenesis, an important cellular response involved in brain repair and regeneration. TBI-enhanced neurogenesis in the dentate gyrus (DG) of the hippocampus is of particular importance due its contribution to learning and memory functions. In the neurogenic process, proliferation and differentiation of neural stem cells (NSCs) follow a well-characterized sequence controlled by many factors including Notch1, which plays essential roles in regulating NSC fate determination under physiological conditions in both developing and adult brains. Following TBI, the dynamic changes of NSCs and the involvement of Notch1 on their development at different stages post-injury are not fully characterized. In the current study, we examined the impact of TBI and Notch1 on NSCs proliferation, survival and neuronal differentiation. Utilizing transgenic mice with tamoxifen-induced GFP expression and Notch1 knock-out in nestin+ NSCs, we examined DG neurogenic response at acute, subacute and chronic stages following a moderate lateral fluid percussion injury. We found that TBI enhanced a proliferative response in the DG at the acute stage following injury; however, this injury response was abolished when Notch1 was conditionally deleted from nestin+ NSCs. We also found that injury and Notch1 deletion drove NSCs committing fate choice towards neuronal differentiation. The results of this study provides further knowledge regarding TBI-induced neurogenic response and Notch1 as the key regulating mechanism.

Serotonin is one of the main neuromodulators in the brain, involved in regulating mood, complex behaviors and sensory input. Serotonin reaches primary somatosensory cortex (S1) via axons of neurons located in the dorsal raphe nucleus (DRN). DRN neurons can be modulated, amongst others, by reward, sensory stimulation, or movement but the activity pattern of serotonergic neurons targeting S1 is not known. Therefore, it is unclear under which circumstances serotonin is released in S1. Here, we expressed GCaMP8 in serotonergic neurons of the DRN to analyze the activity of their axons in S1 using two-photon Ca2+-imaging. Cluster analysis of axonal activities suggests that one to four functional groups of serotonergic axon segments project to a 0.3 mm2 horizontal plane of S1. We show that activity in serotonergic axons is strongly driven by reward and weakly by sensory stimulation of the whiskers. Movement, however, is preceded by a modulation, up and down, of the serotonergic signal seconds before the running onset. In summary, rewards and sensory stimulation lead to activity in serotonergic axons which is likely to adjust signal processing in S1 upon these events. The serotonergic signal changes seconds before movement onset probably preparing the neural network in S1 for the state change that accompanies running.

Acute spinal cord injury is a condition with a poor prognosis, leading to reduced quality of life and high economic costs for both patients and health systems, and only a minority of patients with this injury can achieve a meaningful recovery. Given the high frequency of traumatic events such as vehicle collisions and falls, research aimed at limiting injury extension, promoting neuronal recovery, and improving prognosis is essential. It has been shown that ketone bodies have anti-inflammatory properties and also mediate the Nrf2 pathway, exerting antioxidant effects. The aim was to identify any alternative to mitigate the extension and progression of secondary injury by using 1,3 butanediol as a {beta}-hydroxybutyrate source. An experimental model (n= 60) of clinically healthy male Wistar rats were used, divided into five groups (n=12) as a control group, while the remaining rats were subjected to extradural spinal cord clipping according to the following groups (n=12): Spinal Cord Injury (SCI); endogenous ketosis + methylprednisolone (Endo-K+MP); exogenous ketosis + methylprednisolone (Exo-K+MP), and methylprednisolone (MP). After 8 hours of spinal cord injury, tissue was collected, immunohistochemistry and PCR analyses were carried out. Nrf2 and 3NT for the antioxidant pathway, and HIF-1, NFkB, NLRP3, TNF-[a] and IL-1{beta} for inflammation were analyzed. Results demonstrated that the groups thrown into a ketosis state had better outcomes, and, according to the Exo-k+MP and Endo-k+MP groups, increased Nrf2 and decreased 3NT (p < 0.05), which resulted in an upregulation of antioxidant pathways. According to HIF-1 and NF{kappa}B, Endo-K+MP showed better outcomes p<0.05 and proinflammatory cytokines showed the same pattern as the standard treatment (MP) p<0.05). Overall, our results also demonstrated a downregulation of inflammatory pathways. Author SummarySpinal cord injury is a devastating condition that frequently results in permanent neurological damage, reduced quality of life, and high social and healthcare costs. Current treatments are limited and mainly focus on reducing inflammation after injury, with methylprednisolone being one of the most commonly used therapies despite its associated adverse effects. Previous studies have shown that ketosis, a metabolic state characterized by increased ketone bodies, has anti-inflammatory and antioxidant properties in several neurological conditions. In this study, we investigated whether inducing ketosis could improve early outcomes after acute spinal cord injury. Using a rat model, we compared the effects of endogenous ketosis (induced by fasting) and exogenous ketosis (induced by ketone precursors), alone or in combination with methylprednisolone. We analyzed inflammatory and oxidative stress pathways using immunohistochemistry and molecular techniques. Our findings show that ketosis enhances the anti-inflammatory and antioxidant effects of methylprednisolone, leading to reduced activation of inflammatory pathways and increased antioxidant responses during the first hours after injury. These results suggest that metabolic interventions such as ketosis may represent a promising complementary strategy to improve early management of spinal cord injury.

Traumatic brain injury (TBI), particularly sports- and recreational activity related mild TBI (mTBI), is common in young adults and can be followed by persistent attentional and executive complaints. This study investigated chronic ([&ge;]6 months post-injury) structural brain alterations in gray matter (GM) and white matter (WM) and their associations with self-reported inattentive and hyperactive/impulsive symptoms, with a focus on sex-differentiated patterns. Structural brain properties in gray matter (GM) and white matter (WM) were acquired from 44 subjects with TBI and 45 matched controls, by utilizing structural MRI and diffusion tensor imaging techniques. Behavioral measures assessing severities of post TBI inattentive and hyperactive/impulsive symptoms were collected from each participant. Between-group and sex-specific differences of these brain and behavioral measures were conducted. Interactions among the TBI-induced significant brain- and behavioral-alterations, and their sex-specific patterns, were assessed as well. Male-dominated pattern of increased cortical thickness in superior parietal lobule (SPL) and female-dominated pattern of higher superior longitudinal fasciculus and superior fronto-occipital fasciculus (sFOF) fractional anisotropy (FA) were observed in the TBI group, when compared to controls. In males with TBI, greater SPL cortical thickness was significantly correlated with increased inattentive behaviors. In females with TBI, higher FA of sFOF was significantly correlated with decreased hyperactive/impulsive behaviors. Findings suggest that TBI-induced superior parietal cortical GM abnormalities may significantly cause attention deficits in patients with TBI, especially in males; while optimal post-TBI WM recovery in sFOF significantly contributes to maintenance of inhibitive control in patients with TBI, especially in females.

Concentrations of estradiol (E2) and progesterone (P4), the main female sex hormones, exhibit large fluctuations across the menstrual cycle. Due to their receptors throughout the central nervous system, both hormones have the potential to influence motor function by influencing ionotropic and metabotropic inputs to motor pools, which can be estimated through the neural codes extracted from motor unit discharge patterns. To address key methodological limitations in prior menstrual cycle research on motor output, we established the Motor Units and Sex Hormones (MUSH) collaboration. The objective of this multi-site investigation was to determine whether endogenous fluctuations in estradiol and progesterone influence human motor unit activity. We hypothesized that motor unit discharge rates and persistent inward current (PIC)-related contributions to discharge would be greatest during the late follicular phase, when estradiol concentrations were highest. Fifty females completed a comprehensive protocol involving menstrual cycle and ovulation tracking, serum hormone measurement, and high-density surface electromyographic recordings during isometric contractions to quantify motor unit activity in the early follicular, late follicular, and mid luteal phases. After exclusion of 10 females with either atypical hormone concentration profiles or insufficient motor unit yield, 40 remained in the final analysis. There were significant changes in several motor unit discharge variables between menstrual cycle phases and significant associations with hormone concentrations. Increased estradiol was associated with higher peak discharge rates and ascending discharge rate nonlinearity, while increased progesterone was associated with higher peak discharge rates, more discharge rate hysteresis and ascending discharge rate nonlinearity. Despite reaching statistical significance, the magnitudes of these effects (i.e., effect sizes) were small. Overall, these findings indicate that fluctuations in sex hormones influence motor unit behavior, but the effects are subtle, highlighting the need for well-powered and methodologically rigorous menstrual cycle research. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=151 SRC="FIGDIR/small/699975v1_ufig1.gif" ALT="Figure 1"> View larger version (33K): org.highwire.dtl.DTLVardef@2eb2c0org.highwire.dtl.DTLVardef@1d98359org.highwire.dtl.DTLVardef@13e772borg.highwire.dtl.DTLVardef@1bb27_HPS_FORMAT_FIGEXP M_FIG C_FIG KEY POINTSO_LIThere are small but detectable differences in motor unit discharge rates between menstrual cycle phases, which are predicted by within-participant fluctuations in estradiol and progesterone. C_LIO_LIDischarge rate patterns that provide estimates of neuromodulatory and inhibitory input suggest that estradiol and progesterone can influence spinal cord circuitry differently than has previously been documented in the brain, highlighting an understudied aspect of female neurophysiology. C_LIO_LIVariability in menstrual cycles and associate hormones makes large-scale, rigorous studies especially valuable in female neuromuscular research. C_LI

Transcutaneous auricular vagus nerve stimulation (taVNS) may offer a powerful, noninvasive way to stimulate activity of brainstem arousal systems, including the locus coeruleus-norepinephrine (LC-NE) system. Pulsed taVNS is known to elicit pupil dilation, a marker of LC activity. However, studies reporting taVNS effects on pupil dilation have delivered taVNS and sham stimulation in separate blocks of trials or in separate sessions, hindering the integration of taVNS into rapid, event-related task designs of cognitive neuroscientists. In two experiments, we examined the effectiveness of pulsed taVNS in eliciting pupil dilation when active and sham stimulation were intermixed within the same blocks of trials, and whether these effects depend on sham location and respiratory phase. In Experiment 1 (N = 40), intermixed taVNS and (earlobe) sham pulses of 3.4 seconds produced inconclusive evidence for increased taVNS-evoked pupil dilation. In contrast, in Experiment 2 (N = 60), taVNS pulses of 1.0 seconds had a strong effect on pupil dilation, but only in a group of participants that received sham stimulation at the earlobe; this effect was abolished in a group that received sham stimulation at the upper scapha, a non-vagal control area with a similar density of sympathetic nerve fibers as the cymba concha. Furthermore, taVNS-evoked pupil dilation was not enhanced when stimulation was delivered during exhalation, as would be expected if pupil effects were mediated by the vagus nerve-nucleus tractus solitarius-LC pathway. Together, these findings show that the effect of pulsed taVNS on pupil dilation can be preserved when taVNS and (earlobe) sham are delivered in the same blocks of trials. However, the null finding with the scapha as sham location, and the absence of an enhanced taVNS effect during exhalation call into question the assumption that taVNS-induced pupil dilation is mediated by activation of the vagal afferent pathway.

K+ channels are important for controlling membrane potential and regulating functional properties of microglia. Whereas the inward-rectifying K+ (Kir) channel 2.1 modulates proliferation, voltage-gated K+ channels (Kv) are linked to inflammatory response in mouse microglia (mMG). These channels serve as possible drug targets but little is known regarding their activity in human microglia. We used patch-clamp recording to study membrane currents of primary human microglia (hMG) and human induced pluripotent stem cell-derived microglia-like cells (hiPSC-MGL) and compared them with mMG. Unlike mMG, hMG and hiPSC-MGL exhibited Kir2.1 currents only after LPS+IFN-{gamma} stimulation. Interestingly, Kv currents were not observed in hMG or hiPSC-MGL under any condition. While mMG had a progressively ameboid morphology after stimulation, hMG showed few morphological changes and hiPSC-MGL increased ramification. Overall, the activity of Kir2.1 and Kv channels in hMG and hiPSC-MGL differs fundamentally from mMG. Our findings highlight differences between species and underscore the need for translational approaches.

This study investigated the spinal neural mechanisms underlying post-activation potentiation in ten healthy young males (21.9 {+/-} 4.8 years). Participants performed a 10-second maximal isometric plantarflexion, after which we measured twitch torque and assessed spinal excitability using the soleus H-reflex, D1 presynaptic inhibition and heteronymous Ia facilitation (HF). High-density surface EMG was decomposed to track single motor unit responses. The conditioning contraction increased twitch torque by 12.2 Nm (p < 0.001) immediately and returning to baseline within nine minutes. This mechanical potentiation was accompanied by a 29% reduction in H-reflex amplitude (p < 0.001), which recovered within three minutes. Paradoxically, neurophysiological indices of presynaptic inhibition, D1 and HF were significantly increased (D1: p<0.017; HF: p<0.001), resulting in spinal facilitation. Single MU analysis revealed increased discharge probability, particularly in higher-threshold units indicating overall spinal facilitation. These results demonstrate that post-activation potentiation involves a complex dissociation: H-reflex pathway inhibition along with facilitation of presynaptic spinal mechanisms. This paradox can be explained by either post-activation depression (caused by depletion of neurotransmitter at the Ia-motoneuron synapse) or muscle thixotropy, a contraction history-dependent decrease in muscle spindle sensitivity, which reduces the efficacy of the Ia afferent volley independently of spinal inhibitory mechanisms. Our findings highlight a dissociation between spinal presynaptic facilitation and the decreased H-reflex, underscoring the need for future studies to explicitly test the roles of post-activation depression and muscle thixotropy during post-activation potentiation. New & NoteworthyThis study provides evidence that post-activation potentiation reduces the soleus H-reflex amplitude while concurrently facilitating presynaptic spinal mechanisms. By combining global EMG and single motor unit analyses extracted from high-density surface EMG, we reveal a dissociation between spinal disinhibition and reflex depression. These findings suggest that acute post-contraction reflex suppression might be mediated by mechanisms other than presynaptic inhibition, potentially involving post-activation depression spinal mechanisms or changes in muscle spindle sensitivity.

Phosphorus magnetic resonance spectroscopy (31P-MRS) enables non-invasive measurement of brain metabolism, yet its reproducibility in clinical settings remains unclear. We systematically assessed intra- and intersession variability as well as inter-individual differences of key phosphorus metabolites at 3 Tesla in healthy individuals and persons with Parkinsons disease under various experimental condition. Intersession variability, as measured by coefficients of variation (CoV) increased notably for longer scan intervals ([~]1 year), and metabolite ratios from well-resolved spectral signals (i.e., adenosine triphosphate (ATP), phosphocreatine (PCr), intracellular inorganic phosphate Pi) exhibited consistently higher stability compared to ratios calculated from metabolite signals overlapping on the spectrum (e.g., total nicotinamide adenine dinucleotide (tNAD), as well as phosphate monoesters (PMEs) and phosphate diesters (PDEs). Test-retest variability ranged from [~]5-25 CoV%, where PCr, ATP- and ATP-{gamma} were the most stable while glycerophosphocholine (GPC), glycerophosphoethanolamine (GPE), phosphoethanolamine (PE) and tNAD varied considerably. Inter-individual variability was found to be higher than intra-individual variability for all metabolite ratios, ranging from [~]9-33 CoV%. By systematically quantifying intra-individual and inter-individual variability, as well as providing explicit sample-size recommendations, this study facilitates more reliable longitudinal and cross-sectional clinical trials and translational studies of brain metabolism featuring 31P-MRS.

Adult survivors of pediatric cancers are at elevated risk for neurocognitive late effects, but how these effects relate to metabolic perturbations in the brain remains unclear. To address this knowledge gap, the present study explored associations between neurometabolite levels and neurocognitive function in adult survivors of Hodgkin lymphoma (HL) and acute lymphocytic leukemia (ALL). Data were collected from a single-center observational study conducted at St. Jude Childrens Research Hospital (SJCRH) between October 2022 and November 2024. Adult survivors of HL (N=11 [5 females]; [&ge;]5 years post-diagnosis; mean [SD] current age 34 [9.5] years) and ALL (N=24 [16 females]; [&ge;]5 years post-diagnosis; current age 40 [12.6] years) and community controls (N=35 [17 females]; current age 40 [11] years) completed standardized neurocognitive tests of memory, attention, executive function, and processing speed. Participants also underwent proton magnetic resonance spectroscopy (1H MRS) to quantify neurometabolite levels in the left dorsolateral prefrontal cortex (dlPFC), left hippocampus, and left cerebellum. Analyses used regression models to examine differences in the slope of the relationship between neurometabolite and neurocognitive function or between neurometabolite and age. When comparing HL survivors vs controls, significant interactions were identified for group x age on the ratio of myo-inositol to N-Acetyl aspartic acid (mI/NAA; p=0.007) and group x Gamma-Aminobutyric Acid (GABA) on processing speed (p=0.04) in the left dlPFC. When comparing ALL survivors vs controls, significant interactions were identified for group x myo-inositol on verbal fluency in the left hippocampus (p=0.01) and group x GABA on cognitive flexibility in the left cerebellum (p=0.01). These preliminary findings suggest that neuroinflammation may be a mechanistic underpinning of age-associated neurocognitive impairment in pediatric cancer survivors.

Cervical spinal cord injury (SCI) frequently leads to life-threatening respiratory insufficiency by disrupting descending phrenic pathways. There is growing interest in non-invasive neuromodulatory approaches to enhance plasticity of spared respiratory circuits. We investigated whether cervical repetitive magnetic stimulation (rMS) applied to the injured cervical spinal cord promotes ventilatory recovery in a preclinical mouse model. Adult mice received a unilateral C3 hemicontusion followed by either rMS or sham stimulation. We found that rMS-treated mice significantly improved recovery of tidal volume and minute ventilation at 21 days post injury(dpi) compared to sham controls under various breathing conditions (isoflurane anesthesia, poikilocapnic phase and hypercapnic challenge). Correspondingly, diaphragm EMG enhanced ipsilateral hemidiaphragm activity in ventral and medial regions, and even contralateral hemidiaphragm activity in its ventral part. This was associated with a marked attenuation of the inflammatory response at the cervical spinal cord level. Indeed, rMS lowered astroglial, fibrotic scarring, pro-inflammatory CD68-, Iba1- microglial/macrophage markers. Moreover, perineuronal net expression (WFA positive staining) is globally reduced in the ventral spinal horn, whereas at the lesion site it is markedly increased and tightly wrapped around motoneurons. Together, these findings demonstrate that rMS promotes functional respiratory recovery after cervical SCI through combined enhancement of diaphragmatic motor output and modulation of the inflammatory and extracellular environment. Together, these functional and cellular findings indicate that spinal rMS promotes a permissive, pro-regenerative environment supporting respiratory circuit plasticity. We conclude that rMS significantly enhances ventilatory recovery via reduced inflammatory response and improved intraspinal rewiring after high cervical SCI, suggesting it is a promising non-invasive strategy. The ability of rMS to engage spared respiratory networks and support neuroplasticity highlights its promise as a safe, non-invasive therapeutic strategy with translational potential for rehabilitation of breathing function after SCI. One Sentence SummaryNoninvasive cervical magnetic stimulation improves breathing after spinal cord injury by boosting diaphragm activity and reducing inflammation.

Acute spinal cord injury triggers a complex secondary injury cascade characterized by lesion expansion, neuroinflammation, glial reactivity, and oligodendrocyte degeneration, which together limit endogenous repair. Identifying neuroprotective interventions capable of targeting distinct components of this cascade remains a major challenge. In this study, we compared the neuroprotective profiles of minocycline, a tetracycline derivative with anti-inflammatory and antioxidant properties, and bone marrow mononuclear cells (BMMCs), which exert paracrine immunomodulatory and trophic effects, using a model of complete thoracic spinal cord transection in adult rats. Animals received either BMMCs (5 x 106 cells, intravenously, 24 h post-injury) or minocycline (50 mg/kg twice daily for 48 h, followed by 25 mg/kg for five days). Histological and immunohistochemical analyses revealed that both treatments attenuated secondary damage, reducing lesion area, microglial/macrophage activation (ED1+ cells), and oligodendrocyte pathology (Tau-1+ cells). However, the magnitude and pattern of protection differed between interventions: minocycline produced a stronger reduction in lesion area, whereas BMMCs exerted greater suppression of microglial/macrophage activation and superior preservation of oligodendrocytes. Astrocyte counts (GFAP+ cells) did not differ quantitatively among groups, despite qualitative differences in astrocytic morphology. Integrated effect size analysis further highlighted these complementary neuroprotective profiles across outcomes. Collectively, these findings indicate that minocycline and BMMCs target distinct components of secondary injury after severe spinal cord injury, providing a mechanistic rationale for future studies exploring multi-targeted or combinatorial therapeutic strategies.

Tissue-nonspecific alkaline phosphatase (TNAP) is a ubiquitous enzyme whose substrates are various phosphorylated extracellular molecules including pyridoxal phosphate (vitamin B6) and adenine nucleotides. Dysfunctions of TNAP result in hypophosphatasia, a rare disease characterized by defective bone mineralization and impaired brain functions. In the brain, TNAP expression peaks during development and is associated with various steps of neurogenesis. However, the influence of TNAP activity on neurogenesis remains poorly understood in its cellular and molecular aspects. Here we used the SK-N-SH D human neuroblastoma cell line as a cell culture model to further investigate the involvement of TNAP in neuronal precursor proliferation and neuronal differentiation. We also used 1H-NMR-based metabolomics to investigate the molecular correlates of TNAP action on SK-N-SH D cell proliferation and differentiation. We first observed an increase in alkaline phosphatase (AP) activity when the cells were placed in differentiation medium. We next found that inhibiting TNAP with a specific inhibitor (MLS-0038949) impeded neuroblastoma cell proliferation. TNAP inhibition also hindered neuronal differentiation, as evidenced by a decrease in the number of neurite-bearing cells. In contrast, neurite length was not affected by TNAP inhibition, suggesting that TNAP controls neurite sprouting, but not neurite outgrowth per se. The metabolomic results indicate that proliferation and differentiation are associated with a decrease in the amounts of proteinogenic amino acids as well as that of compounds potentially involved in lipid production. This analysis also revealed that proliferation and differentiation are associated with increased glutathione levels and decreased amounts of hypotaurine and taurine, supporting proposals that organosulfur compounds play an important role in these processes. Since pyridoxine was present in the culture media, these results suggest that TNAP is involved in neurogenesis through mechanisms in addition to its role in vitamin B6 metabolism and may instead involve the ectonucleotidase activity (or an unidentified activity) of TNAP.

ObjectiveTo test the effect of Isoflurane on synaptic transmission of cortico-cortical and thalamocortical projections to the auditory cortex, and investigate how it modulates cortical sensory information processing to produce unconsciousness. MethodsUsing murine auditory thalamocortical brain slices, afferent pathways from the medial geniculate body (MGB) and layer 1 of the proximal cortex were stimulated to evoke excitatory postsynaptic potentials (eEPSPs) in cortical neurons. Whole-cell recordings were made from pyramidal and fast-spiking neurons in layer 2/3 and layer 5. eEPSPs were evaluated along with intrinsic membrane properties in response to stimulation of both pathways with and without isoflurane. ResultsIsoflurane administration resulted in significant eEPSP amplitude reduction following stimulation of both thalamic and cortical pathways, in layer 2/3 (p=0.015, p<0.001) and layer 5 (p<0.001, p<0.001) pyramidal neurons; while it only significantly reduced eEPSP amplitude in fast-spiking interneurons with cortical stimulation (p<0.001). Overall, isoflurane preferentially suppressed synaptic responses to cortico-cortical stimulation compared to thalamocortical (p=0.0002). Under isoflurane, cortico-cortical compared to thalamocortical stimulation evoked eEPSPs with reduced 10-90% rise time in both layer 2/3 and 5 pyramidal neurons, and shorter latency layer 5 neurons. Paired pulse ratio was not changed by isoflurane application, although an interesting loss of depression trend appear in layer 5 pyramidal neurons stimulated by cortical activation. Additional intrinsic neuronal measurements revealed that isoflurane reduced spike threshold significantly in both layer 2/3 and layer 5 neurons, reduced spike latency in layer 2/3 neurons, and input resistance in layer 5 neurons. However, these intrinsic neuronal changes were not seen in fast-spiking interneurons. All isoflurane induced changes were reversible during wash out. ConclusionsApplication of 1% isoflurane to brain slices significantly reduced the amplitudes of eEPSPs and modulated intrinsic neuronal properties. The effects on eEPSP amplitude were greater for cortical stimulation compared to thalamic stimulation. Isoflurane modulated intrinsic neuronal firing properties in pyramidal neurons, but not in fast-spiking interneurons.

Transcranial electrical stimulation (tES) can modulate neural dynamics, yet its effects on memory are heterogeneous. Individual differences in cognitive profiles, may well be one of the potential causes by setting boundary conditions on the extent and mode of the tES-induced modulation of network dynamics. In a sham-controlled, within-subject study (N = 42), we compared the effects of tDCS (1.5 mA), tACS ({+/-}1.0 mA at individual theta frequency, ITF), and otDCS (1.5 mA {+/-} 0.5 mA at ITF) over the left posterior parietal cortex on object-location (OL) associative memory, and examined whether six cognitive abilities (figural reasoning, semantic, visuospatial, processing speed, working memory, mnemonic binding) moderate stimulation outcomes. Associative memory recognition improved selectively under theta-otDCS, whereas tDCS and tACS showed no significant group-level effects. Yet all tES protocols exhibited considerable interindividual variability. Relative to cognitive abilities, processing speed moderated tES effects in line with neural efficiency predictions, yielding greater gains in cognitively faster individuals. In contrast, mnemonic binding and figural reasoning moderated benefits in a compensatory manner, with larger improvements in lower-ability individuals. Overall, the effects of tES on associative memory were specific to the tES protocol and outcome measure while being strongly shaped by cognitive profile via complementing magnification and compensation mechanisms.

With few exceptions, pathological progression in ischemic stroke is presumed to occur uniformly within the ischemic core region. These exceptions include edema formation, brain tissue [Na+] increase, and the qualitative visually-observed decrease of brain tissue [K+], [K+]br, all of which occur in peripheral regions of the ischemic core. We hypothesize that [K+]br within these peripheral regions are heterogeneous (with lower [K+]br in the peripheral compared to the central ischemic core) and are not associated with neuronal degradation. Permanent focal ischemia in 13 rats was produced for 2.5-5 h. Brain sections were quantitatively stained for K+ to assess [K+]br variations between the peripheral and central ischemic core. Regions within the cortical ribbon were used to explore differing rates of K+-depletion expressed as the slopes of [K+]br vs. time relations. Adjacent sections were observed for reflective change and stained for microtubule-associated protein 2 (MAP2) to identify the ischemic region and to relate neuronal pathology to [K+]br variations. The mean value of normal cortex (NC) [K+]br was 96 mEq/kg and of K+-depletion in all ischemic regions over time was 12.2 mEq/kg/h, consistent with measurements from other studies. Exaggerated K+-depletion occurred in 56% of the peripheral ischemic core regions classed as depleted peripheral ischemic core (ICp-DP) regions. These were clearly separated (p<0.001) from the non-depleted peripheral ischemic core (ICp-ND) regions. The normal cortex (NC) regions show stability of [K+]br with a slope near zero. However, the 13.6 mEq/kg/h slopes of the central ischemic core (ICc) and ICp-ND regions were similar (p=0.99) and showed a significant decrease over time. The 6.2 mEq/kg/h slope of the ICp-DP regions was significantly different from that of the ICc (p=0.010) and the ICp-ND (p=0.0071). This lower slope of the ICp-DP curve 2.5 h after stroke onset is due to the accelerated K+-efflux from 0 to 2.5 h, as its value at stroke onset must be [~]100 mEq/kg. However, these differential K+ losses were not reflected in the homogeneous peripheral ischemic core MAP2 immunoreactivity losses. Unlike [K+]br, there was no difference between the MAP2 immunoreactivity in K+-depleted and non-K+-depleted peripheral ischemic core regions (ICp-ND vs ICp-DP, ICp-ND vs ICp-DP, unpaired t-test, p=0.83, p=0.16, respectively). While confirming previous results of quantitative regional losses of [K+]br in the ischemic core, we show that K+ dynamics within the peripheral and the central ischemic core are heterogeneous and not related to MAP2-assessed neuronal structural integrity: the K+-depleted regions in the peripheral ischemic core regions are presumably closer to glymphatic system and other K+-efflux pathways. Such differing K+ dynamics at the edge of the ischemic core in the hyper-acute period in first hours after ischemic onset possibly relate to the spreading depolarization-mediated expansion of the infarct during the period of secondary brain injury. Peripheral ischemic core regions with less K+ might limit spreading depolarization initiation and propagation if there is insufficient K+ for depolarization to occur and make restoration of parenchymal membrane potential improbable even if the functionality of the Na+,K+-ATPase is restored. Further study of differing K+-dynamics within the ischemic core might lead to a better understanding of ischemic stroke pathophysiology.

Phasic increase of frontal midline theta (Fm theta) has been described as a key indicator of cognitive processing, while relatively lower task-related Fm theta is associated with reduced cognitive strain, reflecting less intensive cognitive processing. In a previous investigation, reduced task-related Fm theta in relation to higher expertise, as well as higher setting anticipation performance in the domain of volleyball was identified. In the present study a single-session sham-controlled neurofeedback training (NFT) intervention was conducted to investigate the feasibility of Fm theta downregulation for the improvement of volleyball setting anticipation. A total of 24 volleyball novices was allocated to "Real" (n = 12) and "Sham" (n = 12) Fm theta downregulation NFT groups. NFT-related Fm theta, pre-/post-NFT setting anticipation task performance and task-related Fm theta, as well as resting EEG activity were analyzed. Incongruous with our expectations, the Real NFT group showed a tendency toward stronger Fm theta synchronization compared with the Sham group during NFT. Anticipation task performance did not change significantly from before to after NFT in both groups, yet a significant reduction of task-related Fm theta was observed in the Real NFT group following NFT. A post-NFT rebound of Fm theta could be responsible for this result. With our findings we provide further evidence for the existence of an apparent paradox of Fm theta downregulation, in which cognitive control mechanisms, associated with oscillatory Fm theta activity, appear to hinder explicit downregulation of Fm theta through classical neurofeedback learning mechanisms.