Knockdown of the Non-canonical Wnt Gene Prickle2 Leads to Cerebellar Purkinje Cell Abnormalities While Cerebellar-Mediated Behaviors Remain Intact.

Autism spectrum disorders (ASD) involve brain wide abnormalities that contribute to a constellation of symptoms including behavioral inflexibility, cognitive dysfunction, learning impairments, altered social interactions, and perceptive time difficulties. Although a single genetic variation does not cause ASD, genetic variations such as one involving a non-canonical Wnt signaling gene, Prickle2, has been found in individuals with ASD. Previous work looking into phenotypes of Prickle2 knock-out (Prickle2-/-) and heterozygous mice (Prickle2-/+) suggest patterns of behavior similar to individuals with ASD including altered social interaction and behavioral inflexibility. Growing evidence implicates the cerebellum in ASD. As Prickle2 is expressed in the cerebellum, this animal model presents a unique opportunity to investigate the cerebellar contribution to autism-like phenotypes. Here, we explore cerebellar structural and physiological abnormalities in animals with Prickle2 knockdown using immunohistochemistry, whole-cell patch clamp electrophysiology, and several cerebellar-associated motor and timing tasks, including interval timing and eyeblink conditioning. Histologically, Prickle2-/- mice have significantly more empty spaces or gaps between Purkinje cells in the posterior lobules and a decreased propensity for Purkinje cells to fire action potentials. These structural cerebellar abnormalities did not impair cerebellar-associated behaviors as eyeblink conditioning and interval timing remained intact. Therefore, although Prickle-/- mice show classic phenotypes of ASD, they do not recapitulate the involvement of the adult cerebellum and may not represent the pathophysiological heterogeneity of the disorder.

Concerted Actions of Octopamine and Dopamine Receptors Drive Olfactory Learning.

Aminergic signaling modulates associative learning and memory. Substantial advance has been made in Drosophila on the dopamine receptors and circuits mediating olfactory learning; however, our knowledge of other aminergic modulation lags behind. To address this knowledge gap, we investigated the role of octopamine in olfactory conditioning. Here, we report that octopamine activity through the ß-adrenergic-like receptor Octß1R drives aversive and appetitive learning: Octß1R in the mushroom body αß neurons processes aversive learning, whereas Octß1R in the projection neurons mediates appetitive learning. Our genetic interaction and imaging studies pinpoint cAMP signaling as a key downstream effector for Octß1R function. The rutabaga-adenylyl cyclase synthesizes cAMP in a Ca2+/calmodulin-dependent manner, serving as a coincidence detector for associative learning and likely representing a downstream target for Octß1R. Supporting this notion, the double heterozygous rutabaga/+;octß1r/+ flies perform poorly in both aversive and appetitive conditioning, while individual heterozygous rutabaga/+ and octß1r/+ flies behave like the wild-type control. Consistently, the mushroom body and projection neurons in the octß1r brain exhibit blunted responses to octopamine when cAMP levels are monitored through the cAMP sensor. We previously demonstrated the pivotal functions of the D1 receptor dDA1 in aversive and appetitive learning, and the α1 adrenergic-like receptor OAMB in appetitive learning. As expected, octß1r genetically interacts with dumb (dDA1 mutant) in aversive and appetitive learning, but it interacts with oamb only in appetitive learning. This study uncovers the indispensable contributions of dopamine and octopamine signaling to aversive and appetitive learning. All experiments were performed on mixed sex unless otherwise noted.SIGNIFICANCE STATEMENT Animals make flexible behavioral choices that are constantly shaped by experience. This plasticity is vital for animals to appropriately respond to the cues predicting benefit or harm. In Drosophila, dopamine is known to mediate both reward-based and punishment-based learning while octopamine function is important only for reward. Here, we demonstrate that the octopamine-Octß1R-cAMP pathway processes both aversive and appetitive learning in distinct neural sites of the olfactory circuit. Furthermore, we show that the octopamine-Octß1R and dopamine-dDA1 signals together drive both aversive and appetitive learning, whereas the octopamine-Octß1R and octopamine-OAMB pathways jointly facilitate appetitive, but not aversive, learning. This study identifies the cognate actions of octopamine and dopamine signaling as a key neural mechanism for associative learning.

Prefrontal D1 Dopamine-Receptor Neurons and Delta Resonance in Interval Timing.

Considerable evidence has shown that prefrontal neurons expressing D1-type dopamine receptors (D1DRs) are critical for working memory, flexibility, and timing. This line of work predicts that frontal neurons expressing D1DRs mediate cognitive processing. During timing tasks, one form this cognitive processing might take is time-dependent ramping activity-monotonic changes in firing rate over time. Thus, we hypothesized the prefrontal D1DR+ neurons would strongly exhibit time-dependent ramping during interval timing. We tested this idea using an interval-timing task in which we used optogenetics to tag D1DR+ neurons in the mouse medial frontal cortex (MFC). While 23% of MFC D1DR+ neurons exhibited ramping, this was significantly less than untagged MFC neurons. By contrast, MFC D1DR+ neurons had strong delta-frequency (1-4 Hz) coherence with other MFC ramping neurons. This coherence was phase-locked to cue onset and was strongest early in the interval. To test the significance of these interactions, we optogenetically stimulated MFC D1DR+ neurons early versus late in the interval. We found that 2-Hz stimulation early in the interval was particularly effective in rescuing timing-related behavioral performance deficits in dopamine-depleted animals. These findings provide insight into MFC networks and have relevance for disorders such as Parkinson's disease and schizophrenia.

Dorsal Raphe Serotonin Neurons Mediate CO2-Induced Arousal from Sleep.

Arousal from sleep in response to CO2 is a critical protective phenomenon. Dysregulation of CO2-induced arousal contributes to morbidity and mortality from prevalent diseases, such as obstructive sleep apnea and sudden infant death syndrome. Despite the critical nature of this protective reflex, the precise mechanism for CO2-induced arousal is unknown. Because CO2 is a major regulator of breathing, prevailing theories suggest that activation of respiratory chemo- and mechano-sensors is required for CO2-induced arousal. However, populations of neurons that are not involved in the regulation of breathing are also chemosensitive. Among these are serotonin (5-HT) neurons in the dorsal raphe nucleus (DRN) that comprise a component of the ascending arousal system. We hypothesized that direct stimulation of these neurons with CO2 could cause arousal from sleep independently of enhancing breathing. Dialysis of CO2-rich acidified solution into DRN, but not medullary raphe responsible for modulating breathing, caused arousal from sleep. Arousal was lost in mice with a genetic absence of 5-HT neurons, and with acute pharmacological or optogenetic inactivation of DRN 5-HT neurons. Here we demonstrate that CO2 can cause arousal from sleep directly, without requiring enhancement of breathing, and that chemosensitive 5-HT neurons in the DRN critically mediate this arousal. Better understanding mechanisms underlying this protective reflex may lead to interventions to reduce disease-associated morbidity and mortality.SIGNIFICANCE STATEMENT Although CO2-induced arousal is critical to a number of diseases, the specific mechanism is not well understood. We previously demonstrated that serotonin (5-HT) neurons are important for CO2-induced arousal, as mice without 5-HT neurons do not arouse to CO2 Many have interpreted this to mean that medullary 5-HT neurons that regulate breathing are important in this arousal mechanism. Here we found that direct application of CO2-rich aCSF to the dorsal raphe nucleus, but not the medullary raphe, causes arousal from sleep, and that this arousal was lost with genetic ablation or acute inhibition of 5-HT neurons. We propose that 5-HT neurons in the dorsal raphe nucleus can be activated directly by CO2 to cause arousal independently of respiratory activation.

Clumping Between Carbon Black and Titanium Dioxide Pigment by Water Vapor Absorption and Its Correlation with Electrophoretic Display.

Carbon black and titanium dioxide have been widely used as pigment particles for electrophoretic displays. However, the effect of external water vapor on these pigment particles has not yet been presented. Therefore, in this work, we report the clumping phenomenon between pigment particles as a result of water vapor absorption. To verify clumping between pigment particles, various analysis techniques were used, including scanning electron microscopy, atomic force microscopy, zeta potential measurement, and Raman spectroscopy. We examined the Raman spectrum of carbon black to demonstrate the effect of water vapor absorption on particles. According to the Raman spectrum analysis, the 2D and 2D' peak intensities were significantly increased; moreover, the full widths at half maximum were modified. Thus, we concluded that water vapor absorption on pigment particles can induce the clumping phenomenon on pigments. To protect an electrophoretic display device from external gas transmission, we applied a nanocomposites gas barrier film to the device. The device lifetime was consequently improved by 336%.

Appetitive learning requires the alpha1-like octopamine receptor OAMB in the Drosophila mushroom body neurons.

Associative learning is a fundamental form of behavioral plasticity. Octopamine plays central roles in various learning types in invertebrates; however, the target receptors and underlying mechanisms are poorly understood. Drosophila provides a powerful system to uncover the mechanisms for learning and memory. Here, we report that OAMB in the mushroom body neurons mediates the octopamine's signal for appetitive olfactory learning. The octopamine receptor OAMB has two isoforms (OAMB-K3 and OAMB-AS), differing in the third cytoplasmic loop and downstream sequence. The activation of each OAMB isoform increases intracellular Ca(2+) similar to the alpha1 adrenergic receptor, while OAMB-K3 additionally stimulates cAMP production. The oamb-null mutants showed severely impaired learning in appetitive olfactory conditioning that tests flies' capacity to learn and remember the odor associated with sugar reward. This deficit was also seen in the hypomorphic mutant with reduced OAMB expression in the mushroom bodies, the brain structure crucial for olfactory conditioning. Consistently, the oamb mutant's learning phenotype was fully rescued by conditional expression of either OAMB isoform in the mushroom body αß and γ neurons. These results indicate that the OAMB receptor is a key molecule mediating the octopamine's signal for appetitive olfactory learning and its functional site is the mushroom body αß and γ neurons. This study represents a critical step forward in understanding the cellular mechanism and neural circuit mediating reward learning and memory.

Complementary cognitive roles for D2-MSNs and D1-MSNs in interval timing.

The role of striatal pathways in cognitive processing is unclear. We studied dorsomedial striatal cognitive processing during interval timing, an elementary cognitive task that requires mice to estimate intervals of several seconds, which involves working memory for temporal rules as well as attention to the passage of time. We harnessed optogenetic tagging to record from striatal D2-dopamine receptor-expressing medium spiny neurons (D2-MSNs) in the indirect pathway and from D1-dopamine receptor-expressing MSNs (D1-MSNs) in the direct pathway. We found that D2-MSNs and D1-MSNs exhibited opposing dynamics over temporal intervals as quantified by principal component analyses and trial-by-trial generalized linear models. MSN recordings helped construct and constrain a four-parameter drift-diffusion computational model. This model predicted that disrupting either D2-MSN or D1-MSNs would increase interval timing response times and alter MSN firing. In line with this prediction, we found that optogenetic inhibition or pharmacological disruption of either D2-MSNs or D1-MSNs increased response times. Pharmacologically disrupting D2-MSNs or D1-MSNs also increased response times, shifted MSN dynamics, and degraded trial-by-trial temporal decoding. Together, our findings demonstrate that D2-MSNs and D1-MSNs make complementary contributions to interval timing despite opposing dynamics, implying that striatal direct and indirect pathways work together to shape temporal control of action. These data provide novel insight into basal ganglia cognitive operations beyond movement and have implications for a broad range of human striatal diseases and for therapies targeting striatal pathways.

Collateralizing ventral subiculum melanocortin 4 receptor circuits regulate energy balance and food motivation.

Hippocampal dysfunction is associated with major depressive disorder, a serious mental illness characterized by not only depressed mood but also appetite disturbance and dysregulated body weight. However, the underlying mechanisms by which hippocampal circuits regulate metabolic homeostasis remain incompletely understood. Here we show that collateralizing melanocortin 4 receptor (MC4R) circuits in the ventral subiculum (vSUB), one of the major output structures of the hippocampal formation, affect food motivation and energy balance. Viral-mediated cell type- and projection-specific input-output circuit mapping revealed that the nucleus accumbens shell (NAcSh)-projecting vSUBMC4R+ neurons send extensive collateral projections of to various hypothalamic nuclei known to be important for energy balance, including the arcuate, ventromedial and dorsomedial nuclei, and receive monosynaptic inputs mainly from the ventral CA1 and the anterior paraventricular nucleus of thalamus. Chemogenetic activation of NAcSh-projecting vSUBMC4R+neurons lead to increase in motivation to obtain palatable food without noticeable effect on homeostatic feeding. Viral-mediated restoration of MC4R signaling in the vSUB partially restores obesity in MC4R-null mice without affecting anxiety- and depression-like behaviors. Collectively, these results delineate vSUBMC4R+ circuits to the unprecedented level of precision and identify the vSUBMC4R signaling as a novel regulator of food reward and energy balance.

Drosophila D1 dopamine receptor mediates caffeine-induced arousal.

The arousing and motor-activating effects of psychostimulants are mediated by multiple systems. In Drosophila, dopaminergic transmission is involved in mediating the arousing effects of methamphetamine, although the neuronal mechanisms of caffeine (CAFF)-induced wakefulness remain unexplored. Here, we show that in Drosophila, as in mammals, the wake-promoting effect of CAFF involves both the adenosinergic and dopaminergic systems. By measuring behavioral responses in mutant and transgenic flies exposed to different drug-feeding regimens, we show that CAFF-induced wakefulness requires the Drosophila D1 dopamine receptor (dDA1) in the mushroom bodies. In WT flies, CAFF exposure leads to downregulation of dDA1 expression, whereas the transgenic overexpression of dDA1 leads to CAFF resistance. The wake-promoting effects of methamphetamine require a functional dopamine transporter as well as the dDA1, and they engage brain areas in addition to the mushroom bodies.

Stay or go? Neuronal activity in medial frontal cortex during a voluntary tactile preference task in head-fixed mice.

The decision to move is influenced by sensory, attentional, and motivational cues. One such cue is the quality of the tactile input, with noxious or unpleasant sensations causing an animal to move away from the cue. Processing of painful and unpleasant sensation in the cortex involves multiple brain regions, although the specific role of the brain areas involved in voluntary, rather than reflexive movement away from unpleasant stimuli is not well understood. Here, we focused on the medial subdivision of secondary motor cortex, which is proposed to link sensory and contextual cues to motor action, and tested its role in controlling voluntary movement in the context of an aversive tactile cue. We designed a novel, 3D-printed tactile platform consisting of innocuous (grid) and mildly noxious (spiked) surfaces (50:50 % of total area), which enabled monitoring neuronal activity in the medial frontal cortex by two-photon imaging during a sensory preference task in head-fixed mice. We found that freely moving mice spent significantly less time on a spiked-surface, and that this preference was eliminated by administration of a local anesthetic. At the neuronal level, individual neurons were differentially modulated specific to the tactile surface encountered. At the population level, the neuronal activity was analyzed in relation to the events where mice chose to "stop-on" or "go-from" a specific tactile surface and when they "switched" surfaces without stopping. Notably, each of these three scenarios showed population activity that differed significantly between the grid and spiked tactile surfaces. Collectively, these data provide evidence that tactile quality is encoded within medial frontal cortex. The task pioneered in this study provides a valuable tool to better evaluate mouse models of nociception and pain, using a voluntary task that allows simultaneous recording of preference and choice.

Prevalence and characterization of methicillin-resistant Staphylococcus aureus in raw meat in Korea.

A total of 2,858 meat samples collected during 2003-2008 in Korea were investigated, and methicillin-resistant Staphylococcus aureus (MRSA) were isolated from 1.0% (9/890) of beef, 0.3% (4/1,055) of pork, and 0.3% (3/913) of chicken meat samples, respectively. MRSA isolates showed the two sequence types (STs), ST72 from beef and pork and ST692 from chicken meat. MRSA isolates from beef and pork were Panton-Valentine leukocidin -negative, staphylococcal cassette chromosome mec type IVa strain with ST 72, which is the most prevalent type of community acquired-MRSA in Korea. An identical pulse-field gel electrophoresis pattern was detected among 10 of 16 MRSA isolates: 9 strains from beef (n=5) and pork (n=4) in 2008, respectively, and one strain from beef in 2005.

In vivo electrochemical measurements of exogenously applied dopamine in Drosophila melanogaster.

Carbon-fiber microelectrodes coupled with electrochemical detection have been used extensively for the analysis of biogenic amines. In order to determine the functional role of these amines, in vivo studies have primarily used rats and mice as model organisms. Here, we report on the development of these microanalytical techniques for in vivo electrochemical detection of dopamine in the adult Drosophila melanogaster central nervous system (CNS). A triple-barrel micropipet injector was used to exogenously apply three different concentrations of dopamine, and a cylindrical carbon-fiber microelectrode was placed in the protocerebral anterior medial brain area where dopamine neurons are densely populated. Background-subtracted fast-scan cyclic voltammetry was used to measure dopamine concentration in the fly CNS. Distinct differences are shown for the clearance of exogenously applied dopamine in the brains of wild type flies versus fumin (fmn) mutants lacking a functional dopamine transporter. The current response due to oxidation of dopamine increased significantly from baseline for wild type flies following cocaine incubation. Interestingly, the current remained unchanged for mutant flies under the same conditions. These data confirm the accepted theory that cocaine blocks dopamine transporter function and validates the use of in vivo electrochemical methods to monitor dopamine uptake in Drosophila. Furthermore, after incubation with tetrodotoxin (TTX), a sodium channel blocker, there was a significant increase in peak oxidation current in the wild type flies; however, the current did not significantly change in the fmn mutant. These data suggest that factors that affect neuronal activity via ion channels such as TTX also influence the function of the dopamine transporter in Drosophila.

D1 dopamine receptor dDA1 is required in the mushroom body neurons for aversive and appetitive learning in Drosophila.

Drosophila has robust behavioral plasticity to avoid or prefer the odor that predicts punishment or food reward, respectively. Both types of plasticity are mediated by the mushroom body (MB) neurons in the brain, in which various signaling molecules play crucial roles. However, important yet unresolved molecules are the receptors that initiate aversive or appetitive learning cascades in the MB. We have shown previously that D1 dopamine receptor dDA1 is highly enriched in the MB neuropil. Here, we demonstrate that dDA1 is a key receptor that mediates both aversive and appetitive learning in pavlovian olfactory conditioning. We identified two mutants, dumb1 and dumb2, with abnormal dDA1 expression. When trained with the same conditioned stimuli, both dumb alleles showed negligible learning in electric shock-mediated conditioning while they exhibited moderately impaired learning in sugar-mediated conditioning. These phenotypes were not attributable to anomalous sensory modalities of dumb mutants because their olfactory acuity, shock reactivity, and sugar preference were comparable to those of control lines. Remarkably, the dumb mutant's impaired performance in both paradigms was fully rescued by reinstating dDA1 expression in the same subset of MB neurons, indicating the critical roles of the MB dDA1 in aversive as well as appetitive learning. Previous studies using dopamine receptor antagonists implicate the involvement of D1/D5 receptors in various pavlovian conditioning tasks in mammals; however, these have not been supported by the studies of D1- or D5-deficient animals. The findings described here unambiguously clarify the critical roles of D1 dopamine receptor in aversive and appetitive pavlovian conditioning.

Projection targets of medial frontal D1DR-expressing neurons.

Prefrontal neurons expressing D1-type dopamine receptors (D1DRs) have been implicated in a variety of cognitive processes including working memory and timing. Although D1DRs are most strongly expressed on layer V/VI projection neurons, it is unknown which brain areas are specifically targeted by these projections. Here we selectively marked D1DR neurons using cre-loxP techniques with AAV carrying mCherry fluorescent protein, and traced projection targets of D1DR+ neurons in the mouse medial frontal cortex (MFC). We found relatively strong MFC D1DR+ projections to cortical areas as well as projections to basal ganglia and thalamic nuclei. We found relatively weaker MFC D1DR+ projections to the brainstem, hypothalamus, and other subcortical nuclei. These data intimate that MFC D1DR+ projections are well-positioned to powerfully influence cortical processing and have subcortical specificity. Thus MFC D1DR+ projection neurons may play a key role in tuning cortical networks during goal-directed behavior.

Axial levodopa-induced dyskinesias and neuronal activity in the dorsal striatum.

Levodopa-induced dyskinesias are abnormal involuntary movements that limit the effectiveness of treatments for Parkinson's disease. Although dyskinesias involve the striatum, it is unclear how striatal neurons are involved in dyskinetic movements. Here we record from striatal neurons in mice during levodopa-induced axial dyskinesias. We developed an automated 3-dimensional motion tracking system to capture the development of axial dyskinesias at ∼10ms resolution, and correlated these movements with neuronal activity of striatal medium spiny neurons and fast-spiking interneurons. The average firing rate of medium spiny neurons increased as axial dyskinesias developed, and both medium spiny neurons and fast-spiking interneurons were modulated around axial dyskinesias. We also found that delta field potential power increased in the striatum with dyskinesia, and that this increased delta power coupled with striatal neurons. Our findings provide insight into how striatal networks change as levodopa-induced dyskinesias develop, and suggest that increased medium spiny neuron firing, increased delta field potential power, and abnormal delta-coupling may be neurophysiological signatures of dyskinesias. These data could be helpful in understanding the role of the striatum in the pathogenesis of dyskinesias in Parkinson's disease.

RNA Interference of Human α-Synuclein in Mouse.

α-Synuclein is postulated to play a key role in the pathogenesis of Parkinson's disease (PD). Aggregates of α-synuclein contribute to neurodegeneration and cell death in humans and in mouse models of PD. Here, we use virally mediated RNA interference to knockdown human α-synuclein in mice. We used an siRNA design algorithm to identify eight siRNA sequences with minimal off-targeting potential. One RNA-interference sequence (miSyn4) showed maximal protein knockdown potential in vitro. We then designed AAV vectors expressing miSyn4 and injected them into the mouse substantia nigra. miSyn4 was robustly expressed and did not detectably change dopamine neurons, glial proliferation, or mouse behavior. We then injected AAV2-miSyn4 into Thy1-hSNCA mice over expressing α-synuclein and found decreased human α-synuclein (hSNCA) in both midbrain and cortex. In separate mice, co-injection of AAV2-hSNCA and AAV2-miSyn4 demonstrated decreased hSNCA expression and rescue of hSNCA-mediated behavioral deficits. These data suggest that virally mediated RNA interference can knockdown hSNCA in vivo, which could be helpful for future therapies targeting human α-synuclein.

Optogenetic Stimulation of Frontal D1 Neurons Compensates for Impaired Temporal Control of Action in Dopamine-Depleted Mice.

Disrupted mesocortical dopamine contributes to cognitive symptoms of Parkinson's disease (PD). Past work has implicated medial frontal neurons expressing D1 dopamine receptors (D1DRs) in temporal processing. Here, we investigated whether these neurons can compensate for behavioral deficits resulting from midbrain dopamine dysfunction. We report three main results. First, both PD patients and mice with ventral tegmental area (VTA) dopamine depletion had attenuated delta activity (1-4 Hz) in the medial frontal cortex (MFC) during interval timing. Second, we found that optogenetically stimulating MFC D1DR neurons could increase ramping activity among MFC neurons. Finally, stimulating MFC D1DR neurons specifically at delta frequencies (2 Hz) compensated for deficits in temporal control of action caused by VTA dopamine depletion. Our results suggest that cortical networks can be targeted by frequency-specific brain stimulation to improve dopamine-dependent cognitive processing.

Disease-modifying therapeutic directions for Lewy-Body dementias.

Dementia with Lewy bodies (DLB) is the second leading cause of dementia following Alzheimer's disease (AD) and accounts for up to 25% of all dementia. DLB is distinct from AD in that it involves extensive neuropsychiatric symptoms as well as motor symptoms, leads to enormous societal costs in terms of direct medical care and is associated with high financial and caregiver costs. Although, there are no disease-modifying therapies for DLB, we review several new therapeutic directions in treating DLB. We discuss progress in strategies to decrease the level of alpha-synuclein, to prevent the cell to cell transmission of misfolded alpha-synuclein, and the potential of brain stimulation in DLB.

New therapeutic strategies targeting D1-type dopamine receptors for neuropsychiatric disease.

The neurotransmitter dopamine acts via two major classes of receptors, D1-type and D2-type. D1 receptors are highly expressed in the striatum and can also be found in the cerebral cortex. Here we review the role of D1 dopamine signaling in two major domains: L-DOPA-induced dyskinesias in Parkinson's disease and cognition in neuropsychiatric disorders. While there are many drugs targeting D2-type receptors, there are no drugs that specifically target D1 receptors. It has been difficult to use selective D1-receptor agonists for clinical applications due to issues with bioavailability, binding affinity, pharmacological kinetics, and side effects. We propose potential therapies that selectively modulate D1 dopamine signaling by targeting second messengers downstream of D1 receptors, allosteric modulators, or by making targeted modifications to D1-receptor machinery. The development of therapies specific to D1-receptor signaling could be a new frontier in the treatment of neurological and psychiatric disorders.

Highly oriented gold/nanoclay-polymer nanocomposites for flexible gas barrier films.

Layer-by-layer (LBL) assembly, which uses electronic and ionic intermolecular bonding under nonvacuum conditions, is a promising technology for fabricating gas barrier films owing to its simple processing and easy formation of a multilayer structure. In this research, nanoclay-polymer multilayers of Na(+)-montmorillonite (Na-MMT) were fabricated. Particularly, the addition of AuCl3 on fabricated MMT layers caused a reaction with the surface silanol functional groups (Si-O-H) of the MMT platelets, resulting in the formation of Au2O3 on the MMT-polymer multilayers. The Au2O3 filled the vacancies between the MMT platelets and linked the MMT platelets together, thus forming a gas barrier film that reduced the water vapor transmission rate (WVTR) to 3.2 × 10(-3) g m(-2) day(-1). AuCl3-treated MMT-polymer multilayers thus have the potential to be utilized for manufacturing gas barrier films for flexible electronics on a large scale.