Top-down contribution to motor network reorganization during action preparation

It is unclear whether the Bereitschaftspotential (BP) recorded in humans during action preparation mirrors motor areas activation escalation, or if its early and late phases reflect the engagement of different functional networks. Here, we aimed at recording the TMS evoked-potentials (TEP) stimulating the supplementary motor area (SMA) to assess whether and how cortical excitability and functional connectivity of this region change as the BP increases. We hypothesize that, at later stages, the SMA functional network should become more connected to regions relevant for the implementation of the final motor plan. We performed TMS-EEG recordings on fourteen healthy subjects during the performance of a visuomotor Go/No-go task, eliciting and recording cortical activity and functional connectivity at -700 ms and -300 ms before the onset of visual stimuli over the SMA. When approaching stimulus onset, and thus BP peak, the SMA increased its functional connectivity with movement-related structures in the gamma and alpha bands, indicating a regional top-down preparation to implement the motor act. Beta-band connectivity, instead, was maintained constant for the whole BP time-course, being potentially related to sustained attention required by the experimental task. These findings reveal that the BP is not a mere result of increased activation of the SMA, but the functional networks in which this region is involved qualitatively changes over time, becoming more related to the execution of the motor act.

Parietal and Motor Cortical Dynamics Differentially Shape the Computation of Choice History Bias

Humans and other animals tend to systematically repeat (or alternate) their previous choices, even when judging sensory stimuli presented in a random sequence. Choice history biases may arise from action preparation in motor circuits, or from perceptual or decision processing in upstream areas. Here, we combined source-level magnetoencephalographic (MEG) analyses of cortical population dynamics with behavioral modeling of a visual decision process. We disentangled two neural history signals in human motor and posterior parietal cortex. Gamma-band activity in parietal cortex tracked previous choices throughout the trial and biased evidence accumulation toward choice repetition. Action-specific beta-band activity in motor cortex also carried over to the next trial and biased the accumulation starting point toward alternation. The parietal, but not motor, history signal predicted the next trial's choice as well as individual differences in choice repetition. Our results are consistent with a key role of parietal cortical signals in shaping choice sequences.

Experimental investigation of peculiarities for impact of a sorption action preparation silicon dioxide on infectious agents of cholangitis

Objective. Determination of impact of combination, consisted of 3% solution of silicon dioxide and antibacterial preparations, on bacterial cultures of S. aureus, P. aeruginosa, E. coli. Materials and methods. Clean cultures of bacteria, kept in Collection of Microorganisms in Department of Microbiology and Immunology of Training–Scientific Centre «Іnstitute of Biology and Medicine» of Taras Shevchenko National University: S. aureus (Rosenbach, 1884), P. aeruginosa (Schröter, 1872; Migula, 1900), E. coli (Migula, 1895; Castellani і Chalmers, 1919) were applied. Action of antibacterial preparations cefoperazon, cefoperazon–sulbactam, ampicillin–sulbactam, amicacin, as well as enterosorbent 3% solution of silicon dioxide, was investigated. In the investigation the impact of antibacterial preparations and silicon dioxide together with antibacterial preparations on test–cultures of bacteria was studied, using broth and agarised medium of Muller–Hinton. Results. The data, obtained in the investigation, trust efficacy of combined application of 3% solution of silicon dioxide, owing sorption capacity, with antibacterial preparations in reduction or elimination of subsequent growth of bacterial test–cultures of S. aureus, P. aeruginosa, E. coli. Combination of 3% solution of silicon dioxide with ampicillin–sulbactam in dilutions 64 and 32 mg/l promotes reduction of the E. coli growth on surface of agarised medium in comparison with the investigation variant without application of 3% solution of silicon dioxide. While polyresistence of P. aeruginosa revealed, 3%solution of silicon dioxide together with cefoperazon–sulbactam in concentrations 8 and 16 mg/l and ceftazidime in concentrations 8, 16, 32, 64 mg/l guarantees bactericidal effect for this microorganism. Growth of P. aeruginosa while application of 3% solution of silicon dioxide in combination with ampicillin–sulbactam in dilutions 8, 16, 32, 64 mg/l was arrested. Application of 3% solution of silicon dioxide in combination with amicacin–sulbactam 16 mg/l inhibits the S. aureus growth, what is observed, when combination of 3% solution of silicon dioxide with amicacin in dilutions 8, 16 mg/l and cefoperazon–sulbactam in dilutions 8, 16 mg/l are exploited. Growth of the microorganism do not evolve in variants of the investigation without 3% solution of silicon dioxide, as well as with him, if amikacin is applied in concentrations 64 and 32 mg/l. Conclusion. The biliary ducts drainage in obturative jaundice of tumoral genesis and subsequent presence of drainage (internal or external) constitute the main risk factors for their colonization by multiresistant microorganisms. At the same time, the biliary ducts drainage in combination with antibioticotherapy is estimated as an urgent method for control of the infection primary focus in an acute cholangitis. Establishing of procedure for application of 3% solution of silicon dioxide in combination with certain groups of antibacterial preparations for microorganisms revealed constitute important measure for bacteriobilia prophylaxis. The further investigations conduction with wider spectrum of antibacterial preparations and 3% solution of silicon dioxide for control of clinically significant species of microorganisms is necessary and perspective.

Engagement of the contralateral limb can enhance the facilitation of motor output by loud acoustic stimuli

When intense sound is presented during light muscle contraction, inhibition of the corticospinal tract is observed. During action preparation, this effect is reversed, with sound resulting in excitation of the corticospinal tract. We investigated how the combined maintenance of a muscle contraction during preparation for a ballistic action impacts the magnitude of the facilitation of motor output by a loud acoustic stimulus (LAS) – a phenomenon known as the StartReact effect. Participants executed ballistic wrist flexion movements and a LAS was presented simultaneously with the imperative signal in a subset of trials. We examined whether the force level or muscle used to maintain a contraction during preparation for the ballistic response impacted reaction time and/or the force of movements triggered by the LAS. These contractions were sustained either ipsilaterally or contralaterally to the ballistic response. The magnitude of facilitation by the LAS was greatest when low force flexion contractions were maintained in the limb contralateral to the ballistic response during preparation. There was little change in facilitation when contractions recruited the contralateral extensor muscle, or when they were sustained in the same limb that executed the ballistic response. We conclude that a larger network of neurons which may be engaged by a contralateral sustained contraction prior to initiation may be recruited by the LAS, further contributing to the motor output of the response. These findings may be particularly applicable in stroke rehabilitation where engagement of the contralesional side may increase the benefits of a LAS to the functional recovery of movement.

Approach-Avoidance Decisions Under Threat: The Role of Autonomic Psychophysiological States

Acutely challenging or threatening situations frequently require approach-avoidance decisions. Acute threat triggers fast autonomic changes that prepare the body to freeze, fight or flee. However, such autonomic changes may also influence subsequent instrumental approach-avoidance decisions. Since defensive bodily states are often not considered in value-based decision-making models, it remains unclear how they influence the decision-making process. Here, we aim to bridge this gap by discussing the existing literature on the potential role of threat-induced bodily states on decision making and provide a new neurocomputational framework explaining how these effects can facilitate or bias approach-avoid decisions under threat. Theoretical accounts have stated that threat-induced parasympathetic activity is involved in information gathering and decision making. Parasympathetic dominance over sympathetic activity is particularly seen during threat-anticipatory freezing, an evolutionarily conserved response to threat demonstrated across species and characterized by immobility and bradycardia. Although this state of freezing has been linked to altered information processing and action preparation, a full theoretical treatment of the interactions with value-based decision making has not yet been achieved. Our neural framework, which we term the Threat State/Value Integration (TSI) Model, will illustrate how threat-induced bodily states may impact valuation of competing incentives at three stages of the decision-making process, namely at threat evaluation, integration of rewards and threats, and action initiation. Additionally, because altered parasympathetic activity and decision biases have been shown in anxious populations, we will end with discussing how biases in this system can lead to characteristic patterns of avoidance seen in anxiety-related disorders, motivating future pre-clinical and clinical research.

Output planning at the input stage in visual working memory

Working memory serves as the buffer between past sensations and future behavior, making it vital to understand not only how we encode and retain sensory information in memory but also how we plan for its upcoming use. We ask when prospective action goals emerge alongside the encoding and retention of visual information in working memory. We show that prospective action plans do not emerge gradually during memory delays but are brought into memory early, in tandem with sensory encoding. This action encoding (i) precedes a second stage of action preparation that adapts to the time of expected memory utilization, (ii) occurs even ahead of an intervening motor task, and (iii) predicts visual memory–guided behavior several seconds later. By bringing prospective action plans into working memory at an early stage, the brain creates a dual (visual-motor) memory code that can make memories more effective and robust for serving ensuing behavior.

Numbers in action

To understand the number sense, we need to understand its function. We argue that numerosity estimation is fundamental not only for perception, but also preparation and control of action. We outline experiments that link numerosity estimation with action, pointing to a generalized numerosity system that serves both perception and action preparation.

Response preparation involves a release of intracortical inhibition in task-irrelevant muscles

Action preparation involves widespread modulation of motor system excitability, but the precise mechanisms are unknown. In this study, we investigated whether intracortical inhibition changes in task-irrelevant muscle representations during action preparation. We used transcranial magnetic stimulation (TMS) combined with electromyography in healthy human adults to measure motor evoked potentials (MEPs) and cortical silent periods (CSPs) in task-irrelevant muscles during the preparatory period of simple delayed response tasks. In Experiment 1, participants responded with the left-index finger in one task condition and the right-index finger in another task condition, while MEPs and CSPs were measured from the contralateral non-responding and tonically contracted index finger. During Experiment 2, participants responded with the right pinky finger while MEPs and CSPs were measured from the tonically contracted left-index finger. In both experiments, MEPs and CSPs were compared between the task preparatory period and a resting intertrial baseline. The CSP duration during response preparation decreased from baseline in every case. A laterality difference was also observed in Experiment 1, with a greater CSP reduction during the preparation of left finger responses compared to right finger responses. Despite reductions in CSP duration, consistent with a release of intracortical inhibition, MEP amplitudes were smaller during action preparation when accounting for background levels of muscle activity, consistent with earlier studies that reported decreased corticospinal excitability. These findings indicate intracortical inhibition associated with task-irrelevant muscles is transiently released during action preparation and implicate a novel mechanism for the controlled and coordinated release of motor cortex inhibition.