Tonic Changes Research Articles

Global postural evaluation and motor treatment in the subject with Down Syndrome: Clinical case reports

The aim of the study was to evaluate postural tonic changes and the motor difficulties of the subjects examined were taken into account. For the study, 10 subjects with Down syndrome between the ages of 17 and 38, 7 male and 3 females, were recruited, for a period of 10 month, all with different postural alterations and pathologies. Everyone three times a week performed adapted physical activity protocols; these have been customized and adapted to each individual case, taking into account not only the problems related to the syndrome, but also the emotional sphere of each of them and motor skills. The subjects were subjected a preliminary (T0) static and dynamic baropodometric tests and video-analysis and then repeated every three months (T1, T2). It’s results total and partial improvements in 85% of cases. For each subject, an individual motor treatment program has been drawn up. We can conclude in saying that motor treatment is an important method of treating paramorphisms of the lower limb even in the case of subjects with Down Syndrome that translates into prevention and mitigation of the pathologies from which they suffer, improving daily life, autonomy and quality of life.

Cocaine-Induced Changes in Tonic Dopamine Concentrations Measured Using Multiple-Cyclic Square Wave Voltammetry in vivo.

For over 40 years, in vivo microdialysis techniques have been at the forefront in measuring the effects of illicit substances on brain tonic extracellular levels of dopamine that underlie many aspects of drug addiction. However, the size of microdialysis probes and sampling rate may limit this technique’s ability to provide an accurate assessment of drug effects in microneural environments. A novel electrochemical method known as multiple-cyclic square wave voltammetry (M-CSWV), was recently developed to measure second-to-second changes in tonic dopamine levels at microelectrodes, providing spatiotemporal resolution superior to microdialysis. Here, we utilized M-CSWV and fast-scan cyclic voltammetry (FSCV) to measure changes in tonic or phasic dopamine release in the nucleus accumbens core (NAcc) after acute cocaine administration. Carbon-fiber microelectrodes (CFM) and stimulating electrodes were implanted into the NAcc and medial forebrain bundle (MFB) of urethane anesthetized (1.5 g/kg i.p.) Sprague-Dawley rats, respectively. Using FSCV, depths of each electrode were optimized by determining maximal MFB electrical stimulation-evoked phasic dopamine release. Changes in phasic responses were measured after a single dose of intravenous saline or cocaine hydrochloride (3 mg/kg; n = 4). In a separate group, changes in tonic dopamine levels were measured using M-CSWV after intravenous saline and after cocaine hydrochloride (3 mg/kg; n = 5). Both the phasic and tonic dopamine responses in the NAcc were augmented by the injection of cocaine compared to saline control. The phasic and tonic levels changed by approximately x2.4 and x1.9, respectively. These increases were largely consistent with previous studies using FSCV and microdialysis. However, the minimal disruption/disturbance of neuronal tissue by the CFM may explain why the baseline tonic dopamine values (134 ± 32 nM) measured by M-CSWV were found to be 10-fold higher when compared to conventional microdialysis. In this study, we demonstrated phasic dopamine dynamics in the NAcc with acute cocaine administration. M-CSWV was able to record rapid changes in tonic levels of dopamine, which cannot be achieved with other current voltammetric techniques. Taken together, M-CSWV has the potential to provide an unprecedented level of physiologic insight into dopamine signaling, both in vitro and in vivo, which will significantly enhance our understanding of neurochemical mechanisms underlying psychiatric conditions.

Calcium signaling cascades differentially regulate PGF2α-induced myometrial contractions in water buffaloes (Bubalus bubalis).

This study unravels the differential involvement of calcium signaling pathway(s) in PGF2α-induced contractions in myometrium of nonpregnant (NP) and pregnant buffaloes. Compared to the myometrium of pregnant animals, myometrium of NP buffaloes was more sensitive to PGF2α as manifested by changes in mean integral tension (MIT) and tonicity. In the presence of nifedipine, myometrial contraction to PGF2α was significantly attenuated in both NP and pregnant uteri; however, mibefradil and NNC 55-0396 produced inhibitory effects only in uterus of pregnant animals, thus suggesting the role of extracellular Ca2+ influx through nifedipine-sensitive L-type Ca2+-channels both in NP and pregnant, but T-type Ca2+ channels seem to play a role only during pregnancy. Entry of extracellular Ca2+ is triggered by enhanced functional involvement of Pyr3-sensitive TRPC3 channels and Rho-kinase pathways as evidenced by a significant rightward shift of the concentration-response curve of PGF2α in the presence of Pyr3 and Y-27632 in NP myometrium. But significant down-expressions of TRPC3 and Rho-A proteins during pregnancy apparently facilitate uterine quiescence. In the presence of Ca2+-free solution and cyclopiazonic acid (SERCA blocker), feeble contraction to PGF2α was observed in both NP and pregnant myometrium which suggests minor role of intracellular source of Ca2+ in mediating PGF2α-induced contractions in these tissues.

Selective serotonin reuptake inhibitor treatment retunes emotional valence in primate ventral striatum.

Selective serotonin reuptake inhibitors (SSRIs) are widely used to treat psychiatric disorders with affective biases such as depression and anxiety. How SSRIs exert a beneficial action on emotions associated with life events is still unknown. Here we ask whether and how the effectiveness of the SSRI fluoxetine is underpinned by neural mechanisms in the ventral striatum. To address these issues, we studied the spiking activity of neurons in the ventral striatum of monkeys during an approach-avoidance task in which the valence assigned to sensory stimuli was manipulated. Neural responses to positive and negative events were measured before and during a 4-week treatment with fluoxetine. We conducted PET scans to confirm that fluoxetine binds within the ventral striatum at a therapeutic dose. In our monkeys, fluoxetine facilitated approach of rewards and avoidance of punishments. These beneficial effects were associated with changes in tonic and phasic activities of striatal neurons. Fluoxetine increased the spontaneous firing rate of striatal neurons and amplified the number of cells responding to rewards versus punishments, reflecting a drug-induced positive shift in the processing of emotionally valenced information. These findings reveal how SSRI treatment affects ventral striatum neurons encoding positive and negative valence and striatal signaling of emotional information. In addition to a key role in appetitive processing, our results shed light on the involvement of the ventral striatum in aversive processing. Together, the ventral striatum appears to play a central role in the action of SSRIs on emotion processing biases commonly observed in psychiatric disorders.

Hyponatraemia and hypernatraemia: Disorders of Water Balance in Neurosurgery.

Disorders of tonicity, hyponatraemia and hypernatraemia, are common in neurosurgical patients. Tonicity is sensed by the circumventricular organs while the volume state is sensed by the kidney and peripheral baroreceptors; these two signals are integrated in the hypothalamus. Volume is maintained through the renin-angiotensin-aldosterone axis, while tonicity is defended by arginine vasopressin (antidiuretic hormone) and the thirst response. Edelman found that plasma sodium is dependent on the exchangeable sodium, potassium and free-water in the body. Thus, changes in tonicity must be due to disproportionate flux of these species in and out of the body. Sodium concentration may be measured by flame photometry and indirect, or direct, ion-sensitive electrodes. Only the latter method is not affected by changes in plasma composition. Classification of hyponatraemia by the volume state is imprecise. We compare the tonicity of the urine, given by the sodium potassium sum, to that of the plasma to determine the renal response to the dysnatraemia. We may then assess the activity of the renin-angiotensin-aldosterone axis using urinary sodium and fractional excretion of sodium, urate or urea. Together, with clinical context, these help us determine the aetiology of the dysnatraemia. Symptomatic individuals and those with intracranial catastrophes require prompt treatment and vigilant monitoring. Otherwise, in the absence of hypovolaemia, free-water restriction and correction of any reversible causes should be the mainstay of treatment for hyponatraemia. Hypernatraemia should be corrected with free-water, and concurrent disorders of volume should be addressed. Monitoring for overcorrection of hyponatraemia is necessary to avoid osmotic demyelination.

Tonic and Phasic Amperometric Monitoring of Dopamine Using Microelectrode Arrays in Rat Striatum

Here we report a novel microelectrode array recording approach to measure tonic (resting) and phasic release of dopamine (DA) in DA-rich areas such as the rat striatum and nucleus accumbens. The resulting method is tested in intact central nervous system (CNS) and in animals with extensive loss of the DA pathway using the neurotoxin, 6-hydroxyDA (6-OHDA). The self-referencing amperometric recording method employs Nafion-coated with and without m-phenylenediamine recording sites that through real-time subtraction allow for simultaneous measures of tonic DA levels and transient changes due to depolarization and amphetamine-induced release. The recording method achieves low-level measures of both tonic and phasic DA with decreased recording drift allowing for enhanced sensitivity normally not achieved with electrochemical sensors in vivo.

Hyaluronic acid‐based two‐stage medical therapy to unfold the aged face: The centrifugal approach

Facial aging is a multifactorial process characterized by structural changes to the dermis and ligaments, lipoatrophy in the fat pads and hypodermis, remodeling of the bony skeleton, change in muscle tonicity and tissue descent. The purpose of this study is to evaluate the efficacy of a hyaluronic acid-based treatment for the aging face that addresses all its causes in a caudal to cranial and medial to lateral direction: the centrifugal technique. Between March 2015 and January 2018, 187 patients were treated with a high G' hyaluronic acid in two sessions, one/two weeks apart, to improve signs of facial aging, starting from the lower centrofacial area and progressing laterally and cranially. Results were assessed using a Global Aesthetic Improvement Scale (GAIS) judging pre- and post-treatment (32weeks) pictures. The technique effectively treated the aging face. The investigator and all patients evaluated the results improved or very much improved and agreed that the results were very natural looking. Use of a systematic centrifugal technique to address the signs of facial aging resulted in significant and long-lasting improvement, as judged by the investigator and high patient acceptance and satisfaction.

Influence of Moderate Hyperosmotic Stress on Ultrastructure and Indicators of Energy Metabolism of Chlorella vulgaris (Chlorophyta)

A comparison of the response of freshwater alga Chlorella vulgaris Beijer. on a quantitatively identical change in tonicity of growth medium by different osmotics (NaCl and sucrose) has been studied. Upon an increase in growth-medium osmotic potential (regardless the nature of osmoticum), increased thermogenesis and decreased oxygen absorption by Chlorella is observed first. The difference in the reaction of Chlorella to equiosmotic concentrations of NaCl and sucrose is revealed. Upon an increased salt background, thermogenesis and photosynthetic activity decreases in comparison with the control and the respiration rate is close to the control. In the presence of sucrose, the culture has a higher level of thermogenesis, respiration, and photosynthesis. Sodium chloride does not cause significant changes in ultrastructure of Chlorella and does not lead to significant changes in the diffusional decay of water magnetization in comparison with the control. Under sucrose stress, a change in the cell shape indicating cytorhysis is revealed. The effective water-diffusion coefficient (according to NMR data) decreases, which also indicates the reduction of cell sizes. Sucrose affects Chlorella as a nonpenetrating osmotically active substance. Under moderate hyperosmotic stress, the toxicity of NaCl is a smaller problem for freshwater microalga Chlorella than the partial dehydration caused by sucrose.

The Influence of Ionizing Radiation on Proneness to Audiogenic Seizure and Behavior in Krushinsky–Molodkina Rats

We studied the effects of whole body gamma-radiation (4 Gy, dose rate 0.6 Gy/min) and proton-beam head irradiation (with an energy of 150 meV, 4 Gy and a dose rate of 0.8 Gy/min) on the intensity and timing of audiogenic seizures in rats of the Krushinsky–Molodkina selected strain. In experiments using gamma rays the rat behavior was tested in the open field, elevated plus maze, and Morris water maze tests. No changes in audiogenic tonic–clonic seizures (originating in the brain stem) were found during the first exposure to sound after gamma-irradiation. Slower development of seizures and larger latency of the tonic seizure phase were found following serial daily exposure to sound in rats after proton irradiation. It was also noted that audiogenic myoclonic seizures (which developed in the forebrain) in irradiated rats that were exposed daily to sound had shorter durations, while the intensity of these seizures was at a maximum in all groups. The behavioral tests revealed a moderate increase in anxiety after radiation exposure.

WNK3 and WNK4 exhibit opposite sensitivity with respect to cell volume and intracellular chloride concentration.

Cation-coupled chloride cotransporters (CCC) play a role in modulating intracellular chloride concentration ([Cl-]i) and cell volume. Cell shrinkage and cell swelling are accompanied by an increase or decrease in [Cl-]i, respectively. Cell shrinkage and a decrease in [Cl-]i increase the activity of NKCCs (Na-K-Cl cotransporters: NKCC1, NKCC2, and Na-Cl) and inhibit the activity of KCCs (K-Cl cotransporters: KCC1 to KCC4), wheras cell swelling and an increase in [Cl-]i activate KCCs and inhibit NKCCs; thus, it is unlikely that the same kinase is responsible for both effects. WNK1 and WNK4 are chloride-sensitive kinases that modulate the activity of CCC in response to changes in [Cl-]i. Here, we showed that WNK3, another member of the serine-threonine kinase WNK family with known effects on CCC, is not sensitive to [Cl-]i but can be regulated by changes in extracellular tonicity. In contrast, WNK4 is highly sensitive to [Cl-]i but is not regulated by changes in cell volume. The activity of WNK3 toward NaCl cotransporter is not affected by eliminating the chloride-binding site of WNK3, further confirming that the kinase is not sensitive to chloride. Chimeric WNK3/WNK4 proteins were produced, and analysis of the chimeras suggests that sequences within the WNK's carboxy-terminal end may modulate the chloride affinity. We propose that WNK3 is a cell volume-sensitive kinase that translates changes in cell volume into phosphorylation of CCC.

Advances in the neurophysiology of magnocellular neuroendocrine cells.

Hypothalamic magnocellular neuroendocrine cells have unique electrical properties and a remarkable capacity for morphological and synaptic plasticity. Their large somatic size, their relatively uniform and dense clustering in the supraoptic and paraventricular nuclei, and their large axon terminals in the neurohypophysis make them an attractive target for direct electrophysiological interrogation. Here, we provide a brief review of significant recent findings in the neuroplasticity and neurophysiological properties of these neurones that were presented at the symposium "Electrophysiology of Magnocellular Neurons" during the 13th World Congress on Neurohypophysial Hormones in Ein Gedi, Israel in April 2019. Magnocellular vasopressin (VP) neurones respond directly to hypertonic stimulation with membrane depolarisation, which is triggered by cell shrinkage-induced opening of an N-terminal-truncated variant of transient receptor potential vanilloid type-1 (TRPV1) channels. New findings indicate that this mechanotransduction depends on actin and microtubule cytoskeletal networks, and that direct coupling of the TRPV1 channels to microtubules is responsible for mechanical gating of the channels. Vasopressin neurones also respond to osmostimulation by activation of epithelial Na+ channels (ENaC). It was shown recently that changes in ENaC activity modulate magnocellular neurone basal firing by generating tonic changes in membrane potential. Both oxytocin and VP neurones also undergo robust excitatory synapse plasticity during chronic osmotic stimulation. Recent findings indicate that new glutamate synapses induced during chronic salt loading express highly labile Ca2+ -permeable GluA1 receptors requiring continuous dendritic protein synthesis for synapse maintenance. Finally, recordings from the uniquely tractable neurohypophysial terminals recently revealed an unexpected property of activity-dependent neuropeptide release. A significant fraction of the voltage-dependent neurohypophysial neurosecretion was found to be independent of Ca2+ influx through voltage-gated Ca2+ channels. Together, these findings provide a snapshot of significant new advances in the electrophysiological signalling mechanisms and neuroplasticity of the hypothalamic-neurohypophysial system, a system that continues to make important contributions to the field of neurophysiology.

Phylogenic Determinants of Cardiovascular Frailty, Focus on Hemodynamics and Arterial Smooth Muscle Cells.

The evolution of the circulatory system from invertebrates to mammals has involved the passage from an open system to a closed in-parallel system via a closed in-series system, accompanying the increasing complexity and efficiency of life's biological functions. The archaic heart enables pulsatile motion waves of hemolymph in invertebrates, and the in-series circulation in fish occurs with only an endothelium, whereas mural smooth muscle cells appear later. The present review focuses on evolution of the circulatory system. In particular, we address how and why this evolution took place from a closed, flowing, longitudinal conductance at low pressure to a flowing, highly pressurized and bifurcating arterial compartment. However, although arterial pressure was the latest acquired hemodynamic variable, the general teleonomy of the evolution of species is the differentiation of individual organ function, supported by specific fueling allowing and favoring partial metabolic autonomy. This was achieved via the establishment of an active contractile tone in resistance arteries, which permitted the regulation of blood supply to specific organ activities via its localized function-dependent inhibition (active vasodilation). The global resistance to viscous blood flow is the peripheral increase in frictional forces caused by the tonic change in arterial and arteriolar radius, which backscatter as systemic arterial blood pressure. Consequently, the arterial pressure gradient from circulating blood to the adventitial interstitium generates the unidirectional outward radial advective conductance of plasma solutes across the wall of conductance arteries. This hemodynamic evolution was accompanied by important changes in arterial wall structure, supported by smooth muscle cell functional plasticity, including contractility, matrix synthesis and proliferation, endocytosis and phagocytosis, etc. These adaptive phenotypic shifts are due to epigenetic regulation, mainly related to mechanotransduction. These paradigms actively participate in cardio-arterial pathologies such as atheroma, valve disease, heart failure, aneurysms, hypertension, and physiological aging.

β-Amyloid 25–35 Suppresses the Secretory Activity of the Dopaminergic System in the Rat Brain

Dysfunction of the dopaminergic system of the brain may underlie a number of the clinical manifestations of Alzheimer’s disease. Published data provide evidence that impairments to the normal metabolism of β-amyloid may be the cause of such dysfunction. Experimental increases in β-amyloid levels in the brains of animals lead to decreases in the extracellular dopamine levels and its long-term (tonic) changes in the dorsal ventral striatum. The aim of the present work was to study the effects of β-amyloid on short-term (phasic) changes in dopamine secretion. Aggregated β-amyloid (25–35) solution or physiological saline was administered into the ventricular system of the brains of urethane-anesthetized rats. Dopamine release induced by electrical stimulation was recorded before administration and 10, 30, and 60 min after administration by fast-scan cyclic voltammetry. Dopamine release in the dorsomedial striatum was decreased during the first hour after β-amyloid administration. No statistically significant changes in the core and shell of the nucleus accumbens were seen.

Emotional interference under low versus high executive control

Previous research has demonstrated that task-irrelevant emotional distractors interfere with task performance especially under low phasic executive control (i.e., in nonconflict trials). In the present study, we measured medio-frontal ERPs (N2 and correct-related negativity, CRN) to elucidate which aspects of task performance are affected by emotional interference in a flanker task. To create emotional interference, negative and neutral pictures were presented during the flanker stimuli. N2 and CRN were reduced after negative pictures, indicating that conflict processing and performance monitoring are both affected by emotional interference. On the behavioral level, prolonged response times after negative pictures were observed under low phasic executive control (i.e., in compatible trials). Additionally, we explored whether emotional interference is modulated not only by phasic changes in executive control (i.e., conflict vs. nonconflict trials) but also by tonic changes in executive control (i.e., low vs. high overall conflict frequency). To this end, the flanker task consisted of two blocks with 25% versus 75% incompatible trials. Prolonged response times after negative pictures in compatible trials were observed only under low tonic executive control but not under high executive control.

The Hypotonic Environmental Changes Affect Liposomal Formulations for Nose-to-Brain Targeted Drug Delivery

Systemic administration of drugs is ineffective in the treatment of central nervous system disorders because of the blood-brain barrier. Nasal administration has been suggested as an alternative administration route as drugs absorbed in the olfactory epithelium bypass the blood-brain barrier and reach the brain within minutes. However, the nasal mucosa properties (e.g., tonicity, pH) are not constant because of physiological and environmental factors, and this might limit the therapeutic outcome of nanocarrier-based formulations. To shine light on the impact of environmental ionic strength on nanocarrier-based formulations, we have studied how liposomal formulations respond to the change of tonicity of the external environment. Large unilamellar vesicles loaded with 6 different drugs were exposed to different hypotonic environments, creating an osmotic gradient within the inner core and external environment of the liposomes up to 650 mOsm/kg. Both size and polydispersity of liposomes were significantly affected by tonicity changes. Moreover, the release kinetics of hydrophilic and lipophilic drugs were largely enhanced by hypotonic environments. These results clearly demonstrate that the environmental ionic strength has an impact on liposomal formulation stability and drug release kinetics and it should be considered when liposomal formulations for nose-to-brain targeted drug delivery are designed.

Sperm motility and lipid composition in internally fertilizing ocellate river stingray Potamotrygon motoro

All extant groups of Elasmobranches have internal fertilization and the structure of the male reproductive organs is very specific: sperm passes from the internal organs via the cloaca, but the male copulating organ (clasper) is distant from the cloaca. This suggests that sperm can contact the surrounding medium before fertilization. Because of this involvement with the environment, external signaling in sperm motility activation could occur in these species even though their fertilization mode is internal. In this case, spermatozoa of Elasmobranches should hypothetically possess a specific structure and membrane lipid composition which supports physiological functions of the sperm associated with environmental tonicity changes occurring at fertilization. Additionally, sperm motility properties in these taxa are poorly understood. The current study examined sperm lipid composition and motility under different environmental conditions for the ocellate river stingray, Potamotrygon motoro, an endemic South America freshwater species. Sperm samples were collected from six mature males during the natural spawning period. Sperm motility was examined in seminal fluid and fresh water by light video microscopy. Helical flagellar motion was observed in seminal fluid and resulted in spermatozoon progression; however, when diluted in fresh water, spermatozoa were immotile and had compromised structure. Lipid class and fatty acid (FA) composition of spermatozoa was analyzed by thin layer and gas chromatography. Spermatozoa FAs consisted of 33 ± 1% saturated FAs, 28 ± 1% monounsaturated FAs (MUFAs), and 41 ± 1% polyunsaturated FAs (PUFAs), and a high content of n-6 FAs (32 ± 2%) was measured. These results allowed us to conclude that sperm transfer from P. motoro male into female should occur without coming into contact with the hypotonic environment so as to preserve potent motility. In addition, this unusual reproductive strategy is associated with specific spermatozoa structure and lipid composition. Low level of docosahexaenoic acid and relatively low PUFA/MUFA ratio probably account for the relatively low fluidity of freshwater stingray membrane and can be the main reason for its low tolerance to hypotonicity.

Detailed analysis of skin conductance responses during a gambling task: Decision, anticipation, and outcomes.

Physiological arousal is considered a key factor of gambling behavior. Hence, to understand gambling behavior it is important to study the arousal responses during gambling. Moreover, crucial mechanisms of action could be uncovered by detailing the situations that produce an arousal response. A gamble, or bet, can be partitioned into three distinct phases: (a) decision phase, during which the information concerning the gamble is presented, outcomes are appraised, and a decision is made on how to gamble; (b) anticipation phase, during which the result of the gamble is awaited; (c) outcome phase, during which the outcome of the gamble is presented. Previous research on arousal responses to gambling have mostly measured tonic changes in arousal, and when phasic responses have been measured, analyses have generally concentrated on one of the gamble phases. The aim of the present study was to map the arousal responses during gambling in more detail by measuring skin conductance responses (SCRs) during all three gamble phases of a simple card game. The anticipation phase was found to produce the largest arousal response, suggesting anticipation to be a major contributor to arousal during gambling behavior. Risk behavior during the gambling task was mirrored in self-reported risk taking in everyday life, and risk-takers displayed smaller SCRs compared to nonrisk-takers during decision making, suggesting this as a possible biomarker for risk-taking individuals.

Sequential and synchronized hypertonicity-induced activation of Rel-family transcription factors is required for osmoprotection in renal cells

NF-κB and TonEBP belong to the Rel-superfamily of transcription factors. Several specific stimuli, including hypertonicity which is a key factor for renal physiology, are able to activate them. It has been reported that, after hypertonic challenge, NF-κB activity can be modulated by TonEBP, considered as the master regulator of transcriptional activity in the presence of changes in environmental tonicity. In the present work we evaluated whether hypertonicity-induced gene transcription mediated by p65/RelA and TonEBP occurs by an independent action of each transcription factor or by acting together. To do this, we evaluated the expression of their specific target genes and cyclooxygenase-2 (COX-2), a common target of both transcription factors, in the renal epithelial cell line Madin-Darby canine kidney (MDCK) subjected to hypertonic environment. The results herein indicate that hypertonicity activates the Rel-family transcription factors p65/RelA and TonEBP in MDCK cells, and that both are required for hypertonic induction of COX-2 and of their specific target genes. In addition, present data show that p65/RelA modulates TonEBP expression and both colocalize in nuclei of hypertonic cultures of MDCK cells. Thus, a sequential and synchronized action p65/RelA → TonEBP would be necessary for the expression of hypertonicity-induced protective genes.

Affect dynamics of facial EMG during continuous emotional experiences

Emotional experiences are complex, multi-component processes that unfold over time. Accordingly, it is crucial to understand the temporal dynamics of these constituent components. Here we studied the dynamics of one of the core emotional systems, i.e. facial muscle activity, during continuous emotional experiences, elicited by movies. We found that transient zygomatic fluctuations were narrowly tuned to a positive emotional experience. During a positive but not a negative movie, zygomatic response patterns were consistent across participants, tracked with subjective ratings and co-varied with emotional dynamics. Corrugator activity evidenced a broader affective profile and larger individual variability. It was coordinated with tonic changes in emotional negativity and inversely coupled with transient changes in positive affect. Taken together, our results confirmed previous findings on the affective profiles of facial responses and extended them to temporal dynamics. They further uncovered important differences in temporal response characteristics of zygomatic and corrugator measures.

Network mechanisms underlying the role of oscillations in cognitive tasks.

Oscillatory activity robustly correlates with task demands during many cognitive tasks. However, not only are the network mechanisms underlying the generation of these rhythms poorly understood, but it is also still unknown to what extent they may play a functional role, as opposed to being a mere epiphenomenon. Here we study the mechanisms underlying the influence of oscillatory drive on network dynamics related to cognitive processing in simple working memory (WM), and memory recall tasks. Specifically, we investigate how the frequency of oscillatory input interacts with the intrinsic dynamics in networks of recurrently coupled spiking neurons to cause changes of state: the neuronal correlates of the corresponding cognitive process. We find that slow oscillations, in the delta and theta band, are effective in activating network states associated with memory recall. On the other hand, faster oscillations, in the beta range, can serve to clear memory states by resonantly driving transient bouts of spike synchrony which destabilize the activity. We leverage a recently derived set of exact mean-field equations for networks of quadratic integrate-and-fire neurons to systematically study the bifurcation structure in the periodically forced spiking network. Interestingly, we find that the oscillatory signals which are most effective in allowing flexible switching between network states are not smooth, pure sinusoids, but rather burst-like, with a sharp onset. We show that such periodic bursts themselves readily arise spontaneously in networks of excitatory and inhibitory neurons, and that the burst frequency can be tuned via changes in tonic drive. Finally, we show that oscillations in the gamma range can actually stabilize WM states which otherwise would not persist.