The Sense of Agency during Continuous Action: Performance Is More Important than Action-Feedback Association

<div><p>The sense of agency refers to the feeling that one is controlling events through one’s own behavior. This study examined how task performance and the delay of events influence one’s sense of agency during continuous action accompanied by a goal. The participants were instructed to direct a moving dot into a square as quickly as possible by pressing the left and right keys on a keyboard to control the direction in which the dot traveled. The interval between the key press and response of the dot (i.e., direction change) was manipulated to vary task difficulty. Moreover, in the assisted condition, the computer ignored participants’ erroneous commands, resulting in improved task performance but a weaker association between the participants’ commands and actual movements of the dot relative to the condition in which all of the participants’ commands were executed (i.e., self-control condition). The results showed that participants’ sense of agency increased with better performance in the assisted condition relative to the self-control condition, even though a large proportion of their commands were not executed. We concluded that, when the action-feedback association was uncertain, cognitive inference was more dominant relative to the process of comparing predicted and perceived information in the judgment of agency.</p></div

Frequency of key presses in each condition.

<p>Error bars represent standard errors. We believe that the frequency of key presses reflects the extent of feelings of control. The higher the frequency of key presses, the less control is experienced. The participants pressed the keys more frequently in the 400 ms and 700 ms conditions relative to the 100 ms condition, while the difference between the two longer delay conditions was non-significant. Participants pressed the keys less frequently in the assisted condition relative to the self-control condition. The interaction between delay in response and assistance was non-significant.</p

An example of the assisted condition.

<p>In the assisted condition, when the angle between the direction of the dot and the target location was less than 90° (the left figure; i.e., when the direction of the dot was within the range shown with the semicircle), commands that caused the dot to move away from the target location (clockwise turn in the left figure) were ignored, while commands that caused the dot to move toward the target location were executed (counterclockwise turn in the left figure). When the angle between the direction of the dot and target location was at least 90° (the right figure), all commands were executed.</p

The number of times participants pressed the left or right key and the number of ignored key presses in each trial.

<p>Error bars represent standard errors. The participants pressed the keys more often when the delay in response was longer. The number of times participants pressed the keys did not differ significantly between the assisted and self-control conditions when the delay was 100 ms, but when the delay increased to 400 ms or 700 ms, they pressed the keys fewer times in the assisted condition relative to the self-control condition. The proportion of ignored operations was greater in the 400 ms and 700 ms conditions relative to the 100 ms condition.</p

Mean control ratings in each condition.

<p>Error bars represent standard errors. The rating scores decreased significantly with incremental delays in response. The differences between the assisted and self-control conditions were significant in the 400 ms and 700 ms conditions but non-significant in the 100 ms condition.</p

The flow of each trial of the experimental task. Arrows with broken lines indicate the direction in which the dot moved.

<p>Participants were instructed to direct the moving dot into the square as quickly as possible by pressing the left or right key to turn the moving dot clockwise or counterclockwise, respectively. After moving the dot to the destination, they used a mouse to rate the extent to which they felt that the dot was under their control, using a 9-point scale.</p

Studying DNA G‑Quadruplex Aptamer by ¹⁹F NMR

In this study, we demonstrated that ¹⁹F NMR can be used to study the thrombin-binding aptamer (TBA) DNA G-quadruplex, widely used as a model structure for studying G-quadruplex aptamers. We systematically examined the structural feature of the TBA G-quadruplex aptamer with fluorine-19 (¹⁹F) labels at all of the thymidine positions. We successfully observed the structural change between the G-quadruplex and the unstructured single strand by ¹⁹F NMR spectroscopy. The thermodynamic parameters of these DNA G-quadruplex aptamers were also determined from the ¹⁹F NMR signals. We further showed that the ¹⁹F NMR method can be used to observe the complex formed by TBA G-quadruplex and thrombin. Our results suggest that ¹⁹F NMR spectroscopy is a useful approach to study the aptamer G-quadruplex structure

Thiol-Mediated Synthesis of Hyaluronic Acid–Epigallocatechin-3‑<i>O</i>‑Gallate Conjugates for the Formation of Injectable Hydrogels with Free Radical Scavenging Property and Degradation Resistance

Hyaluronic acid (HA)-based biomaterials have demonstrated only limited in vivo stability as a result of rapid degradation by hyaluronidase and reactive oxidative species. The green tea catechin, (−)-epigallocatechin-3-<i>O</i>-gallate (EGCG), has received considerable attention because of its powerful antioxidant and enzyme-inhibitory activities. We describe here the synthesis of HA-EGCG conjugate using a thiol-mediated reaction and its use for the preparation of a long-lasting injectable hydrogel. HA-EGCG conjugates with tunable degrees of substitution were synthesized by the nucleophilic addition reaction between EGCG quinone and thiolated HA under mild conditions. Contrary to unmodified HA, the conjugates exhibited free radical scavenging and hyaluronidase-inhibitory activities. Peroxidase-catalyzed coupling reaction between EGCG moieties was employed to produce in situ forming HA-EGCG hydrogel with surprisingly high resistance to hyaluronidase-mediated degradation. When injected subcutaneously in mice, HA-EGCG hydrogel was retained much longer than HA-tyramine hydrogel with minimal inflammation

Novel Lysophospholipid Acyltransferase PLAT1 of <i>Aurantiochytrium limacinum</i> F26-b Responsible for Generation of Palmitate-Docosahexaenoate-Phosphatidylcholine and Phosphatidylethanolamine

<div><p>N-3 polyunsaturated fatty acids (PUFA), such as docosahexaenoic acid (DHA, 22:6n-3), have been reported to play roles in preventing cardiovascular diseases. The major source of DHA is fish oils but a recent increase in the global demand of DHA and decrease in fish stocks require a substitute. Thraustochytrids, unicellular marine protists belonging to the Chromista kingdom, can synthesize large amounts of DHA, and, thus, are expected to be an alternative to fish oils. DHA is found in the acyl chain(s) of phospholipids as well as triacylglycerols in thraustochytrids; however, how thraustochytrids incorporate DHA into phospholipids remains unknown. We report here a novel lysophospholipid acyltransferase (PLAT1), which is responsible for the generation of DHA-containing phosphatidylcholine and phosphatidylethanolamine in thraustochytrids. The PLAT1 gene, which was isolated from the genomic DNA of <i>Aurantiochytrium limacinum</i> F26-b, was expressed in <i>Saccharomyces cerevisiae</i>, and the FLAG-tagged recombinant enzyme was characterized after purification with anti-FLAG affinity gel. PLAT1 shows wide specificity for donor substrates as well as acceptor substrates <i>in vitro</i>, <i>i.e</i>, the enzyme can adopt lysophosphatidylcholine, lysophosphatidylethanolamine, lysophosphatidylserine and lysophosphatidylinositol as acceptor substrates, and 15:0/16:0-CoA and DHA-CoA as donor substrates. In contrast to the <i>in vitro</i> experiment, only lysophosphatidylcholine acyltransferase and lysophosphatidylethanolamine acyltransferase activities were decreased in <i>plat1</i>-knockout mutants, resulting in a decrease of 16:0-DHA-phosphatidylcholine (PC) [PC(38∶6)] and 16:0-DHA-phosphatidylethanolamine (PE) [PE(38∶6)], which are two major DHA-containing phospholipids in <i>A. limacinum</i> F26-b. However, the amounts of other phospholipid species including DHA-DHA-PC [PC(44∶12)] and DHA-DHA-PE [PE(44∶12)] were almost the same in plat-knockout mutants and the wild-type. These results indicate that PLAT1 is the enzyme responsible for the generation of 16:0-DHA-PC and 16:0-DHA-PE in the thraustochytrid.</p></div

Disruption of the <i>plat1</i> gene in <i>A. limacinum</i> F26-b.

<p>(A, B) LPCAT activity was measured using 25 µM of 15:0-CoA (A) or DHA-CoA (B), 1 µM [1-¹⁴C]palmitoyl-LPC and 10 µg of the cell protein (cell lysate) from the <i>plat1</i>-knockout mutant (KO; red column) or wild-type (WT; blue column). (C) Various LPLAT activities were measured using 25 µM of the corresponding LPLs, 1 µM [1-¹⁴C]palmitoyl-CoA, 10 µg of the cell protein from KO (red column) or WT (blue column). Data represent the mean ± SD (n = 3). * and ** represent p<0.05 and not significant (p>0.10), respectively. (D) Change in the molecular species of PC and PE after the disruption of the <i>plat1</i> gene in <i>A. limacinum</i> F26-b. The PL fraction was prepared from <i>A. limacinum</i> F26-b before and after the disruption of the <i>plat1</i> gene. PLs were analyzed by Chip-based nanoESI-MS using a 4000Q TRAP with chip-based ionization source, TriVersa NanoMate (Advion BioSystems, Ithaca, NY, USA). The intensities at m/z 850 for 16:0-22:6-PC [PC(38∶6)], m/z 764 for 16:0-22:6-PE [PE(38∶6)], m/z 922 for 22:6-22:6-PC [PC(44∶12)], and m/z 836 for 22:6-22:6-PE [PE(44∶12)] were extracted and analyzed. The intensity of PL species of KO (red column) was expressed as a percentage of that of WT (blue column). Data represent the mean ± SD for 3 independent experiments (n = 1). * and ** represent p<0.05 and not significant (p>0.10), respectively.</p