Correlation of risk-taking propensity with cross-frequency phase–amplitude coupling in the resting EEG

Objective

Recent evidence has suggested that the weak inhibitory influence of the prefrontal cortex on the subcortical structures may be responsible for risk-taking behaviour. The aim was to determine the possibility that this weakness in top-down control is reflected in changes in the cross-frequency phase–amplitude coupling (CFPAC) in the electroencephalography (EEG).

Methods

Nineteen-channel EEGs were recorded from 50 healthy volunteers with their eyes closed before risk-taking propensity was assessed by behavioural measures, the domain-specific risk-taking (DOSPERT) scale and the Barrett impulsiveness scale (BIS). Correlation analyses between the CFPACs and the behavioural measures were performed.

Results

The CFPACs were negatively correlated with the risk-taking DOSPERT and BIS scores in frontal (Fp2) and centro–parietal (C3, C4 and P4) regions. By contrast, the CFPACs were positively correlated with the risk-taking DOSPERT and BIS scores in the right hemisphere (T8 and P8).

Conclusions

We suggest that frequent risk-taking behaviour is closely associated with the reduced interference of the cortical control network on the reward-oriented system. The CFPAC, which reflects the degree of interactions among functional systems, provides information about an individual’s risk-taking propensity.

Significance

The CFPAC may be a useful neurophysiological indicator of an individual’s tendency towards risk-taking behaviours, which thus potentially contributes to evaluating the severity of the psychiatric diseases exhibiting abnormal risk-taking behaviours.     

Distribution and intrinsic membrane properties of basal forebrain GABAergic and parvalbumin neurons in the mouse

The basal forebrain (BF) strongly regulates cortical activation, sleep homeostasis, and attention. Many BF neurons involved in these processes are GABAergic, including a subpopulation of projection neurons containing the calcium‐binding protein, parvalbumin (PV). However, technical difficulties in identification have prevented a precise mapping of the distribution of GABAergic and GABA/PV+ neurons in the mouse or a determination of their intrinsic membrane properties. Here we used mice expressing fluorescent proteins in GABAergic (GAD67‐GFP knock‐in mice) or PV+ neurons (PV‐Tomato mice) to study these neurons. Immunohistochemical staining for GABA in GAD67‐GFP mice confirmed that GFP selectively labeled BF GABAergic neurons. GFP+ neurons and fibers were distributed throughout the BF, with the highest density in the magnocellular preoptic area (MCPO). Immunohistochemistry for PV indicated that the majority of PV+ neurons in the BF were large (>20 μm) or medium‐sized (15–20 μm) GFP+ neurons. Most medium and large‐sized BF GFP+ neurons, including those retrogradely labeled from the neocortex, were fast‐firing and spontaneously active in vitro. They exhibited prominent hyperpolarization‐activated inward currents and subthreshold “spikelets,” suggestive of electrical coupling. PV+ neurons recorded in PV‐Tomato mice had similar properties but had significantly narrower action potentials and a higher maximal firing frequency. Another population of smaller GFP+ neurons had properties similar to striatal projection neurons. The fast firing and electrical coupling of BF GABA/PV+ neurons, together with their projections to cortical interneurons and the thalamic reticular nucleus, suggest a strong and synchronous control of the neocortical fast rhythms typical of wakefulness and REM sleep. J. Comp. Neurol., 521:1225–1250, 2013. © 2012 Wiley Periodicals, Inc.     

Synthesis and antimicrobial evaluation of piperic acid amides and their lower homologues

Seven piperic acid amides along with their lower homologs (12) were synthesized using HATU-DIPEA coupling reagent. All the synthesized derivatives were evaluated for their antibacterial activities against Staphylococcus aureus, Pseudomonas aeruginosa, and vancomycin-resistant P. aeruginosa. They were found to be more active on P. aeruginosa than on S. aureus. However, they did not exhibit potent activity on Vancomycin resistant P. aeruginosa. Among the tested compounds, methylenedioxycinnamic acid amide of anthranilic acid (MDCA-AA, 2a) was found to be most active against S. aureus with MIC of 3.125 μg/ml. The PAS and INH amides of piperic acid were screened against Mycobacterium tuberculosis H37R_a strain. They were found to be most active among all the tested compounds but were found to be less active than the standard drug, isoniazid.     

Novel approach to real-time flash photolysis and confocal [Ca2+] imaging

Flash photolysis of “caged” compounds using ultraviolet light is a powerful experimental technique for producing rapid changes in concentrations of bioactive signaling molecules. Studies that employ this technique have used diverse strategies for controlling the spatial and temporal application of light to the specimen. In this paper, we describe a new system for flash photolysis that delivers light from a pulsed, adjustable intensity laser through an optical fiber coupled into the epifluorescence port of a commercial confocal microscope. Photolysis is achieved with extremely brief (5 ns) pulses of ultraviolet light (355 nm) that can be synchronized with respect to confocal laser scanning. The system described also localizes the UV intensity spatially so that uncaging only occurs in defined subcellular regions; moreover, because the microscope optics are used in localization, the photolysis volume can be easily adjusted. Experiments performed on rat ventricular myocytes loaded with the Ca²⁺ indicator fluo-3 and the Ca²⁺ cage o-nitrophenyl ethylene glycol bis(2-aminoethyl ether)-N,N,N′N′-tetraacetic acid (NP–EGTA) demonstrate the system’s capabilities. Localized intracellular increases in [Ca²⁺] can trigger sarcoplasmic reticular Ca²⁺ release events such as Ca²⁺ sparks and, under certain conditions, regenerative Ca²⁺ waves. This relatively simple and inexpensive system is, therefore, a useful tool for examining local signaling in the heart and other tissues.     

Robust coupling of body movement and gaze in young infants

In the first few months after birth, rapid bursts of body movement precede and possibly facilitate shifts of gaze during free looking, with potential consequences for perception and cognition. Here we report that the characteristic features of movement-gaze coupling found during free looking are preserved when attention is perturbed by a salient change in the visual environment. Twenty-four 3-month-olds looked at two attractive 3-dimensional objects while body movement and corneal reflections of the objects were recorded. Lateral head movement was measured offline. After approximately 2 s of looking at one stimulus, the nonfixated stimulus either began to rotate back and forth (distracter events) or remained motionless (control events). In distracter events, the motion of the nonfixated stimulus triggered substantial motor quieting, shortened the duration of the look, and shortened the time to reorient gaze compared to control events. Abbreviated motor quieting and small increases in lateral head movement occurred during control events at the same time in the look as the protracted motor quieting and increased head movement in distracter events. Despite these perturbations, the characteristic bursts of body movement that precede shifts of gaze during free looking occurred in both distracter and control events. The results demonstrate the robust nature of early movement-gaze coupling, raise questions about the specific role of attention in the dynamic links between body movement and gaze, and highlight the potential short and long term functional significance of movement-gaze-attention coupling.     

Hydrolytic stability of composite repair bond

The hydrolytic stability of composite repairs is a desirable property. In the present study, the composite repair microtensile bond strength, failure mode distribution, and nanoleakage occurrence before and after thermocycling were evaluated. Standardized, 1-month-old composite substrates were roughened, cleaned, and randomly assigned to seven groups according to the intermediate agent applied. Resin-based, silane-based, and combined silane/adhesive coupling agents were investigated. The same resin composite as the substrate was used for repair. For each group, repaired samples were wet stored for 24 h (37 degrees C) or thermocycled (5,000 cycles, 5-55 degrees C). Failure mode and silver nitrate penetration were examined by stereomicroscopy. Intermediate agent, experimental condition, and their interaction were significant factors. Hydrophobic flowable composites resulted in statistically higher repair strengths, lower occurrence of adhesive failures, and good quality interfacial coupling without any silver uptake in both conditions. Light-curing, hydrophilic resin monomer-based intermediate agents, although not affected by thermocycling, showed a more pronounced silver penetration. The composite repair strength of a self-curing silane/adhesive agent was significantly affected by thermal stresses, despite the absence of silver uptake. A prehydrolized silane agent recorded the lowest repair strength, with minimal or no evidence of interfacial silver impregnation after thermocycling. In conclusion, flowability and hydrophobic nature can be considered important properties when selecting intermediate agents for composite repair.     

Cardiac alternans and intracellular calcium cycling

Cardiac alternans refers to a condition in which there is a periodic beat‐to‐beat oscillation in electrical activity and the strength of cardiac muscle contraction at a constant heart rate. Clinically, cardiac alternans occurs in settings that are typical for cardiac arrhythmias and has been causally linked to these conditions. At the cellular level, alternans is defined as beat‐to‐beat alternations in contraction amplitude (mechanical alternans), action potential duration (APD; electrical or APD alternans) and Ca²⁺ transient amplitude (Ca²⁺ alternans). The cause of alternans is multifactorial; however, alternans always originate from disturbances of the bidirectional coupling between membrane voltage (V_m) and intracellular calcium ([Ca²⁺]_i). Bidirectional coupling refers to the fact that, in cardiac cells, V_m depolarization and the generation of action potentials cause the elevation of [Ca²⁺]_i that is required for contraction (a process referred to as excitation–contraction coupling); conversely, changes of [Ca²⁺]_i control V_m because important membrane currents are Ca²⁺ dependent. Evidence is mounting that alternans is ultimately caused by disturbances of cellular Ca²⁺ signalling. Herein we review how two key factors of cardiac cellular Ca²⁺ cycling, namely the release of Ca²⁺ from internal stores and the capability of clearing the cytosol from Ca²⁺ after each beat, determine the conditions under which alternans occurs. The contributions from key Ca²⁺‐handling proteins (i.e. surface membrane channels, ion pumps and transporters and internal Ca²⁺ release channels) are discussed.     

Vasorelaxation induced by methyl cinnamate,the major constituent of the essential oil of Ocimum micranthum,in rat isolated aorta

The aim of the present study was to investigate the vascular effects of the E‐isomer of methyl cinnamate (E‐MC) in rat isolated aortic rings and the putative mechanisms underlying these effects. At 1–3000 μmol/L, E‐MC concentration‐dependently relaxed endothelium‐intact aortic preparations that had been precontracted with phenylephrine (PHE; 1 μmol/L), with an IC₅₀ value (geometric mean) of 877.6 μmol/L (95% confidence interval (CI) 784.1–982.2 μmol/L). These vasorelaxant effects of E‐MC remained unchanged after removal of the vascular endothelium (IC₅₀ 725.5 μmol/L; 95% CI 546.4–963.6 μmol/L) and pretreatment with 100 μmol/L N^G‐nitro‐l ‐arginine methyl ester (IC₅₀ 749.0 μmol/L; 95% CI 557.8–1005.7 μmol/L) or 10 μmol/L 1H‐[1,2,4]oxadiazolo[4,3‐a]quinoxalin‐1‐one (IC₅₀ 837.2 μmol/L; 95% CI 511.4–1370.5 μmol/L). Over the concentration range 1–3000 μmol/L, E‐MC relaxed K⁺‐induced contractions in mesenteric artery preparations (IC₅₀ 314.5 μmol/L; 95% CI 141.9–697.0 μmol/L) with greater potency than in aortic preparations (IC₅₀ 1144.7 μmol/L; 95% CI 823.2–1591.9 μmol/L). In the presence of a saturating contractile concentration of K⁺ (150 mmol/L) in Ca²⁺‐containing medium combined with 3 μmol/L PHE, 1000 μmol/L E‐MC only partially reversed the contractile response. In contrast, under similar conditions, E‐MC nearly fully relaxed PHE‐induced contractions in aortic rings in a Ba²⁺‐containing medium. In preparations that were maintained under Ca²⁺‐free conditions, 600 and 1000 μmol/L E‐MC significantly reduced the contractions induced by exogenous Ca²⁺ or Ba²⁺ in KCl‐precontracted preparations, but not in PHE‐precontracted preparations (in the presence of 1 μmol/L verapamil). In addition, E‐MC (1–3000 μmol/L) concentration‐dependently relaxed the contractions induced by 2 mmol/L sodium orthovanadate. Based on these observations, E‐MC‐induced endothelium‐independent vasorelaxant effects appear to be preferentially mediated by inhibition of plasmalemmal Ca²⁺ influx through voltage‐dependent Ca²⁺ channels. However, the involvement of a myogenic mechanism in the effects of E‐MC is also possible.