Spatial Accuracy of Predictive Saccades Determines the Performance of Continuous Visuomotor Action

In a table tennis rally, players perform interceptive actions on a moving ball continuously in a short time, such that the acquisition process of visual information is an important determinant of the performance of the action. However, because it is technically hard to measure gaze movement in a real game, little is known about how gaze behavior is conducted during the continuous visuomotor actions and contributes to the performance. To examine these points, we constructed a novel psychophysical experiment model enabling a continuous visuomotor task without spatial movement of any body parts, including the arm and head, and recorded the movement of the gaze and effector simultaneously at high spatiotemporal resolution. In the task, Gabor patches (target) moved one after another at a constant speed from right to left at random vertical positions on an LC display. Participants hit the target with a cursor moving vertically on the left side of the display by controlling their prehensile force on a force sensor. Participants hit the target with the cursor using a rapid-approaching movement (rapid cursor approach, RCA). Their gaze also showed rapid saccadic approaching movement (saccadic eye approach, SEA), reaching the predicted arrival point of the target earlier than the cursor. The RCA reached in or near the Hit zone in the successful (Hit) trial, but ended up away from it in the unsuccessful (Miss) trial, suggesting the spatial accuracy of the RCA determines the task's success. The SEA in the Hit trial ended nearer the target than the Miss trial. The spatial accuracy of the RCA diminished when the target disappeared 100 ms just after the end of the SEA, suggesting that visual information acquired after the saccade acted as feedback information to correct the cursor movement online for the cursor to reach the target. There was a target speed condition that the target disappearance did not compromise RCA's spatial accuracy, implying the possible RCA correction based on the post-saccadic gaze location information. These experiments clarified that gaze behavior conducted during fast continuous visuomotor actions enables online correction of the ongoing interceptive movement of an effector, improving visuomotor performance.

Proposal of an algorithm to evaluate geometric distortion and artifact spreading in digital breast tomosynthesis

Background According to the European Reference Organization for Quality Assurance Breast Screening and European Diagnostic Services, the spatial accuracy of reconstructed images and reconstruction artifacts must be evaluated in digital breast tomosynthesis (DBT) quality control procedures. Purpose To propose a computational algorithm to evaluate the geometric distortion and artifact spreading (GDAS) in DBT images. Material and Methods The proposed algorithm analyzed tomosynthesis images of a phantom that contains aluminum spheres (1 mm in diameter) arranged in a rectangular matrix spaced 5 cm apart that was inserted in 5-mm-thick polymethylmethacrylate (PMMA). Results The obtained results were compared with the values provided by the algorithm developed by the National Coordinating Center for the Physics of Mammography (NCCPM). In the comparison, the results depended on the dimensions of the region of interest (ROI). This dependence proves the benefit of the proposed algorithm because it allows the user to select the ROI. Conclusion The computational algorithm proved to be useful for the evaluation of GDAS in DBT images, in the same way as the reference algorithm (NCCPM), as well as allowing the selection of the ROI dimensions that best suit the spreading of the artifact in the analyzed images.

DNA Nanodevices: from Mechanical Motions to Biomedical Applications

: Inspired by molecular machines in nature, artificial nanodevices have been designed to realize various biomedical functions. Self-assembled deoxyribonucleic acid (DNA) nanostructures that feature designed geometries, excellent spatial accuracy, nanoscale addressability and marked biocompatibility provide an attractive candidate for constructing dynamic nanodevices with biomarker-targeting and stimuli-responsiveness for biomedical applications. Here, a summary of typical construction strategies of DNA nanodevices and their operating mechanisms are presented. We also introduced recent advances in employing DNA nanodevices as platforms for biosensing and intelligent drug delivery. Finally, the broad prospects and main challenges of the DNA nanodevices in biomedical applications are discussed.

Creative people use memory differently: Divergent thinking modulates how episodic memory is combined with semantic knowledge

The ability to generate novel ideas, known as divergent thinking, is dependent on both semantic knowledge and episodic memory. Semantic knowledge and episodic memory are known to interact to support memory decisions, but it is not known how they may interact to support divergent thinking. We addressed this question by examining whether divergent thinking ability moderates interactions between semantic knowledge and different episodic memory processes in a spatial memory task. Participants completed the Alternative Uses Test to assess divergent thinking ability, then completed a memory task in which they searched for target objects that were either placed in semantically expected or semantically unexpected locations within scenes. In a subsequent test, participants indicated where in each scene the target object had been located previously (i.e., spatial accuracy test), then provided confidence-based recognition memory judgments that indexed distinct episodic memory processes (i.e., recollection, familiarity strength, and unconscious memory) for the scenes. We found that higher divergent thinking ability predicted 1) an increased benefit from putatively hippocampus-based episodic memory (i.e., recollection and unconscious memory) on spatial accuracy overall, and 2) beneficial differences in how semantic knowledge was combined with recollection and unconscious memory to influence spatial accuracy. In contrast, there were no effects of divergent thinking with respect to non-hippocampal memory (i.e., familiarity). These findings indicate that semantic knowledge and episodic memory function differently in highly divergent thinkers. In particular, these results suggest that divergent thinking is supported by the ability to flexibly combine semantic knowledge with episodic memory, particularly hippocampus-based memory.

High-precision spatial analysis of mouse courtship vocalization behavior reveals sex and strain differences

Mice display a wide repertoire of vocalizations that varies with sex, strain, and context. Especially during social interaction, mice emit sequences of ultrasonic vocalizations (USVs) of high complexity. As animals of both sexes vocalize, a reliable attribution of USVs to their emitter is essential. The state-of-the-art in sound localization for USVs in 2D allows spatial localization at a resolution of multiple centimeters. However, animals interact at closer ranges, e.g. snout-to-snout. Hence, improved algorithms are required to reliably assign USVs. We present a novel algorithm, SLIM (Sound Localization via Intersecting Manifolds), that achieves a 3-fold improvement in accuracy (12-14.3mm) using only 4 microphones and extends to many microphones and localization in 3D. This accuracy allows reliable assignment of 84.3% of all USVs in our dataset. We apply SLIM to courtship interactions between adult C57Bl/6J wildtype mice and those carrying a heterozygous Foxp2 variant (R552H). The improved spatial accuracy reveals detailed vocalization preferences for specific spatial relations between the mice. Specifically, vocalization probability, duration, Wiener entropy, and frequency level differed in particular spatial relations between WT females, Foxp2-R552H and WT males. In conclusion, the improved attribution of vocalizations to their emitters provides a foundation for better understanding social vocal behaviors.

Differences on Prosaccade Task in Skilled and Less Skilled Female Adolescent Soccer Players

Although the relationship between cognitive processes and saccadic eye movements has been outlined, the relationship between specific cognitive processes underlying saccadic eye movements and skill level of soccer players remains unclear. Present study used the prosaccade task as a tool to investigate the difference in saccadic eye movements in skilled and less skilled Chinese female adolescent soccer players. Fifty-six healthy female adolescent soccer players (range: 14–18years, mean age: 16.5years) from Fujian Youth Football Training Base (Fujian Province, China) took part in the experiment. In the prosaccade task, participants were instructed to fixate at the cross at the center of the screen as long as the target appeared peripherally. They were told to saccade to the target as quickly and accurately as possible once it appeared. The results indicated that skilled soccer players exhibited shorter saccade latency (p=0.031), decreased variability of saccade latency (p=0.013), and higher spatial accuracy of saccade (p=0.032) than their less skilled counterparts. The shorter saccade latency and decreased variability of saccade latency may imply that the attentional system of skilled soccer player is superior which leads to smaller attention fluctuation and less attentional lapse. Additionally, higher spatial accuracy of saccade may imply potential structural differences in brain underlying saccadic eye movement between skilled and less skilled soccer players. More importantly, the results of the present study demonstrated that soccer players’ cognitive capacities vary as a function of their skill levels. The limitations of the present study and future directions of research were discussed.

Acoustic wave propagation with new spatial implicit and temporal high-order staggered-grid finite-difference schemes

The implicit staggered-grid (SG) finite-difference (FD) method can obtain significant improvement in spatial accuracy for performing numerical simulations of wave equations. Normally, the second-order central grid FD formulas are used to approximate the temporal derivatives, and a relatively fine time step has to be used to reduce the temporal dispersion. To obtain high accuracy both in space and time, we propose a new spatial implicit and temporal high-order SG FD stencil in the time–space domain by incorporating some additional grid points to the conventional implicit FD one. Instead of attaining the implicit FD coefficients by approximating spatial derivatives only, we calculate the coefficients by approximating the temporal and spatial derivatives simultaneously through matching the dispersion formula of the seismic wave equation and compute the FD coefficients of our new stencil by two schemes. The first one is adopting a variable substitution-based Taylor-series expansion (TE) to derive the FD coefficients, which can attain (2M + 2)th-order spatial accuracy and (2N)th-order temporal accuracy. Note that the dispersion formula of our new stencil is non-linear with respect to the axial and off-axial FD coefficients, it is complicated to obtain the optimal spatial and temporal FD coefficients simultaneously. To tackle the issue, we further develop a linear optimisation strategy by minimising the L2-norm errors of the dispersion formula to further improve the accuracy. Dispersion analysis, stability analysis and modelling examples demonstrate the accuracy, stability and efficiency advantages of our two new schemes.