Passive listening to preferred motor tempo modulates corticospinal excitability

Rhythms are an essential characteristic of our lives and auditory-motor coupling affects a variety of behaviors. Previous research has shown that neural regions associated with motor system processing are coupled to perceptual rhythmic processing, such that the perception of rhythmic stimuli can entrain motor responses. However, the degree to which individual preference modulates the motor system is unknown. Recent work has shown that passively listening to metrically strong rhythms increases corticospinal excitability, as indicated by transcranial magnetic stimulation (TMS). Furthermore, neuroimaging evidence suggests that premotor activity increases while listening to tempos occurring within a preferred tempo category. Preferred tempo (PT) refers to the rate of a hypothetical endogenous oscillator that may be indicated by spontaneous motor tempo (SMT) and preferred perceptual tempo (PPT) measurements. The present study investigated whether listening to a rhythm at an individual's PT preferentially modulates motor excitability. SMT was obtained in human participants through a tapping task, in which subjects were asked to tap a response key at their most comfortable rate. Subjects listened to tone sequences at 11 log-spaced tempos and rated their preference for each (PPT). SMT and PPT measurements were correlated, indicating that preferred and produced tempos occurred at a similar rate. Crucially, single-pulse TMS delivered to left M1 during PPT judgments revealed that corticospinal excitability, measured by motor-evoked potentials, was modulated by tempos traveling closer to individual PT. However, the specific nature of this modulation differed across individuals, with some exhibiting an increase in excitability around PT and others exhibiting a decrease. These findings suggest that auditory-motor coupling induced by rhythms is preferentially modulated by rhythms occurring at a preferred rate, and that individual differences can alter the nature of this coupling

Examining methods to induce cognitive fatigue

Cognitive fatigue is important to user task productivity and worker safety in critical occupations because it may cause exhaustion and difficulty executing mental tasks leading to increased errors and job related injuries. Activities that require sustained focused attention over time (i.e. vigilance) increase stress and induce cognitive fatigue. In careers where safety is critical, such as aviation, homeland security, and medicine, these errors can lead to serious injury or even death. Therefore, studying this phenomenon is crucial for findings ways to ameliorate these deleterious effects. In order to study cognitive fatigue effects in a laboratory setting researchers need to find effective tasks to induce fatigue. Studies that fail to do so may suffer ceiling effects as participants may not arrive to the study fatigued. Three methods shown to be stressful in the literature, a 15-minute break, a 15-minute vigilance task, and a 30-minute vigilance task were used to induce laboratory fatigue. These three methods were compared to determine their effectiveness of inducing fatigue. Physiological fatigue was determined using ECG, subjective fatigue was determined using self-report stress, task engagement, and anxiety, and cognitive fatigue was determined using performance on a cognitive test designed to measure executive functioning. It was hypothesized that a 30-minute vigilance task would be most effective at inducing fatigue, as errors during vigilance tasks tend to increase over time on watch. Overall self-reported stress and fatigue was rated high in both vigilance tasks, but only the 30-minute task induced cognitive fatigue (decreased performance pre to post on the cognitive task). This finding is unique in the literature, as previous research has tested fatigue effects using subjective measures and not cognitive ones. Researchers who are interested in studying the restoration of cognitive fatigue effects are recommended to use tasks that require sustained focused attention for at least 30-minutes. It is also recommended that future research investigate motivational differences which may have lead to these findings

Delayed onset of changes in soma action potential genesis in nociceptive A-beta DRG neurons in vivo in a rat model of osteoarthritis

<p>Abstract</p> <p>Background</p> <p>Clinical data on osteoarthritis (OA) suggest widespread changes in sensory function that vary during the progression of OA. In previous studies on a surgically-induced animal model of OA we have observed that changes in structure and gene expression follow a variable trajectory over the initial days and weeks. To investigate mechanisms underlying changes in sensory function in this model, the present electrophysiological study compared properties of primary sensory nociceptive neurons at one and two months after model induction with properties in naïve control animals. Pilot data indicated no difference in C- or Aδ-fiber associated neurons and therefore the focus is on Aβ-fiber nociceptive neurons.</p> <p>Results</p> <p>At one month after unilateral derangement of the knee by cutting the anterior cruciate ligament and removing the medial meniscus, the only changes observed in Aβ-fiber dorsal root ganglion (DRG) neurons were in nociceptor-like unresponsive neurons bearing a hump on the repolarization phase; these changes consisted of longer half width, reflecting slowed dynamics of AP genesis, a depolarized Vm and an increased AP amplitude. At two months, changes observed were in Aβ-fiber high threshold mechanoreceptors, which exhibited shorter AP duration at base and half width, shorter rise time and fall time, and faster maximum rising rate/maximum falling rate, reflecting accelerated dynamics of AP genesis.</p> <p>Conclusion</p> <p>These data indicate that Aβ nociceptive neurons undergo significant changes that vary in time and occur later than changes in structure and in nociceptive scores in this surgically induced OA model. Thus, if changes in Aβ-fiber nociceptive neurons in this model reflect a role in OA pain, they may relate to mechanisms underlying pain associated with advanced OA.</p

Predicting Mobile Mental Telehealth Usability Based on Individual Differences

Due to the increased need for the delivery of successful mental health interventions in special populations (i.e., military personnel, rural populations, aging populations, etc.), mobile mental telehealth applications have been developed to supplement patient-practitioner interaction. While there is a great deal of work on both patient and practitioner satisfaction with mobile mental telehealth devices, little is known about the influence of individual differences on user perceptions of usability and usefulness. The present study seeks to better predict the usability of mobile mental telehealth applications by drawing from the Technology Acceptance Model (Davis & Venkatesh, 1996; Venkatesh & Davis, 2000; Venkatesh, 2000) and self-determination theory literature (Deci, Eghrari, Patrick, & Leone, 1994; Ryan & Deci, 2001; Ryan & Deci, 2000). Eighty undergraduate students participated in a usability study examining the perceived ease of use of two free-to-download mobile mental telehealth applications. In this experiment, participants completed a series of surveys related to attitudes towards mental telehealth applications, motivation to use mental telehealth technology, and a brief demographic survey after interacting with the mental telehealth applications. A stepwise regression with an adjusted R2 value of .41 indicated that a little less than half of the variability in perceived mental telehealth application usability is predicted by user competence, user attitudes toward telehealth technology, and user goals for the system. The implications of these findings will be discussed further, as well as the limitations of this study

Impact of an invasive alien plant on litter decomposition along a latitudinal gradient

Invasive alien plant effects on ecosystem functions are often difficult to predict across environmental gradients due to the context-dependent interactions between the invader and the recipient communities. Adopting a functional trait-based framework could provide more mechanistic predictions for invasive species' impacts. In this study, we contrast litter decomposition rates among communities with and without the invasive plant Impatiens glandulifera in five regions along a 1600 km long latitudinal gradient in Europe. Across this gradient, four functional traits, namely leaf dry matter content (LDMC), specific leaf area (SLA), stem-specific density (SSD), and plant height, are correlated to rates of litter decomposition of standardized rooibos (labile), green tea (recalcitrant), and I. glandulifera litter. Our results show that both invaded and non-invaded plant communities had a higher expression of acquisitive traits (low LDMC and SSD, high SLA) with increasing temperature along the latitudinal gradient, partly explaining the variation in decomposition rates along the gradient. At the same time, invasion shifted community trait composition toward more acquisitive traits across the latitudinal gradient. These trait changes partly explained the increased litter decomposition rates of the labile litter fraction of rooibos and I. glandulifera litter in invaded communities, a shift that was most evident in the warmer study regions. Plant available nitrogen was lower in invaded communities, likely due to high nutrient uptake by I. glandulifera. Meanwhile, the coldest study region was characterized by a reversed effect of invasion on decomposition rates. Here, community traits related to low litter quality and potential allelopathic effects of the invader resulted in reduced litter decomposition rates, suggesting a threshold temperature at which invader effects on litter decomposition turn positive. This study therefore illustrates how functional trait changes toward acquisitive traits can help explain invader-induced changes in ecosystem functions such as increased litter decomposition

Store-Operated Ca2+ Entry (SOCE) and Purinergic Receptor-Mediated Ca2+ Homeostasis in Murine bv2 Microglia Cells: Early Cellular Responses to ATP-Mediated Microglia Activation

Microglia activation is a neuroinflammatory response to parenchymal damage with release of intracellular metabolites, e.g., purines, and signaling molecules from damaged cells. Extracellular purines can elicit Ca(2+)-mediated microglia activation involving P2X/P2Y receptors with metabotropic (P2Y) and ionotropic (P2X) cell signaling in target cells. Such microglia activation results in increased phagocytic activity, activation of their inflammasome and release of cytokines to sustain neuroinflammatory (so-called M1/M2 polarization). ATP-induced activation of ionotropic P2X4 and P2X7 receptors differentially induces receptor-operated Ca(2+) entry (ROCE). Although store-operated Ca(2+) entry (SOCE) was identified to modulate ROCE in primary microglia, its existence and role in one of the most common murine microglia cell line, BV2, is unknown. To dissect SOCE from ROCE in BV2 cells, we applied high-resolution multiphoton Ca(2+) imaging. After depleting internal Ca(2+) stores, SOCE was clearly detectable. High ATP concentrations (1 mM) elicited sustained increases in intracellular [Ca(2+)]i whereas lower concentrations (≤100 μM) also induced Ca(2+) oscillations. These differential responses were assigned to P2X7 and P2X4 activation, respectively. Pharmacologically inhibiting P2Y and P2X responses did not affect SOCE, and in fact, P2Y-responses were barely detectable in BV2 cells. STIM1S content was significantly upregulated by 1 mM ATP. As P2X-mediated Ca(2+) oscillations were rare events in single cells, we implemented a high-content screening approach that allows to record Ca(2+) signal patterns from a large number of individual cells at lower optical resolution. Using automated classifier analysis, several drugs (minocycline, U73122, U73343, wortmannin, LY294002, AZ10606120) were tested on their profile to act on Ca(2+) oscillations (P2X4) and sustained [Ca(2+)]i increases. We demonstrate specific drug effects on purinergic Ca(2+) pathways and provide new pharmacological insights into Ca(2+) oscillations in BV2 cells. For example, minocycline inhibits both P2X7- and P2X4-mediated Ca(2+)-responses, and this may explain its anti-inflammatory action in neuroinflammatory disease. As a technical result, our novel automated bio-screening approach provides a biomedical engineering platform to allow high-content drug library screens to study neuro-inflammation in vitro

Microwave-assisted synthesis of highly crystalline, multifunctional iron oxide nanocomposites for imaging applications

We report a reproducible single-step, microwave-assisted approach for the preparation of multifunctional magnetic nanocomposites comprising superparamagnetic iron oxide (Fe3O4) cores, a polyelectrolyte stabilizer and an organic dye with no requirement for post-processing. The stabilisers poly(sodium 4-styrenesulfonate) (PSSS) and sodium polyphosphate (SPP) have been thoroughly investigated and from analysis using electron microscopy, dynamic light scattering measurements, magnetic hysteresis and magnetic resonance (MR) imaging, we show that the higher degree of Fe3O4 nanoparticle crystallinity achieved with the PSSS stabiliser leads to enhanced magnetic behaviour and thus better contrast agent relaxivity compared to the less crystalline, poorly defined particles obtained when SPP is employed as a stabiliser. We also demonstrate the potential for obtaining a multifunctional magnetic-fluorescent nanocomposite using our microwave-assisted synthesis. In this manner, we demonstrate the intimate link between synthetic methodology (microwave heating with a polyelectrolyte stabilizer) and the resulting properties (particle size, shape, and magnetism) and how this underpins the functionality of the resulting nanocomposites as agents for biomedical imaging