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BackgroundReaching movements are crucial for daily living and rehabilitation, for which Fitts' Law describes a speed-accuracy trade-off that movement time increases with task difficulty. This study aims to investigate whether cortical activation in motor-related areas is directly linked to task difficulty as defined by Fitts' Law. Understanding this relationship provides a physiological basis for parameter selection in therapeutic exercises.MethodsSixteen healthy subjects performed 2D reaching movements using a rehabilitation robot, with their cortical responses detected using functional near-infrared spectroscopy (fNIRS). Task difficulty was manipulated by varying target size and distance, resulting in 3 levels of index-of-difficulty (ID). Kinematic signals were recorded alongside cortical activity to assess the relationship among movement time, task difficulty, and cortical activation.ResultsOur results showed that movement time increased with ID by 0.2974s/bit across all subjects (conditional r2 = 0.6434, p < 0.0001), and all subjects showed individual trends conforming Fitts' Law (all p < 0.001). Neither activation in BA4 nor in BA6 showed a significant correlation with ID (p > 0.05), while both the target size and distance, as well as the interaction between them, showed a significant relationship with BA4 or BA6 activation (all p < 0.05).ConclusionThis study found that although kinematic measures supported Fitts' Law, cortical activity in motor-related areas during reaching movements did not correlate directly with task difficulty as defined by Fitts' Law. Additional factors such as muscle activation may call for different cortical control even when difficulty was identical.

Background: Reaching movements are crucial for daily living and rehabilitation, for which Fitts' Law describes a speed-accuracy trade-off that movement time increases with task difficulty. This study aims to investigate whether cortical activation in motor-related areas is directly linked to task difficulty as defined by Fitts' Law. Understanding this relationship provides a physiological basis for parameter selection in therapeutic exercises., Methods: Sixteen healthy subjects performed 2D reaching movements using a rehabilitation robot, with their cortical responses detected using functional near-infrared spectroscopy (fNIRS). Task difficulty was manipulated by varying target size and distance, resulting in 3 levels of index-of-difficulty (ID). Kinematic signals were recorded alongside cortical activity to assess the relationship among movement time, task difficulty, and cortical activation., Results: Our results showed that movement time increased with ID by 0.2974s/bit across all subjects (conditional r 2 = 0.6434, p < 0.0001), and all subjects showed individual trends conforming Fitts' Law (all p < 0.001). Neither activation in BA4 nor in BA6 showed a significant correlation with ID ( p > 0.05), while both the target size and distance, as well as the interaction between them, showed a significant relationship with BA4 or BA6 activation (all p < 0.05)., Conclusion: This study found that although kinematic measures supported Fitts' Law, cortical activity in motor-related areas during reaching movements did not correlate directly with task difficulty as defined by Fitts' Law. Additional factors such as muscle activation may call for different cortical control even when difficulty was identical., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Ji, Chen, Qiao, Yan, Chen, Luo, Cui, Zong, Xie and Niu.)

Shannon’s Index of Difficulty ( $ID$ ), reputable for quantifying the perceived difficulty of pointing tasks as a logarithmic relationship between movement-amplitude ( $A$ ) and target-width ( $W$ ), is used for modeling the corresponding observed movement-times ( $MT_{O}$ ) in such tasks in controlled experimental setup. However, real-life pointing tasks are both spatially and temporally uncontrolled, being influenced by factors, such as – human aspects, subjective behavior, the context of interaction, the inherent speed-accuracy trade-off, where, emphasizing accuracy compromises speed of interaction and vice versa. Effective target-width ( $W_{e}$ ) is considered as spatial adjustment for compensating accuracy. However, no significant adjustment exists in the literature for compensating speed in different contexts of interaction in these tasks. As a result, without any temporal adjustment, the true difficulty of an uncontrolled pointing task may be inaccurately quantified using Shannon’s $ID$ . To verify this, we propose ANTASID (A Novel Temporal Adjustment to Shannon’s ID) formulation with detailed performance analysis. We hypothesized a temporal adjustment factor ( $t$ ) as a binary logarithm of $MT_{O}$ , compensating for speed due to contextual differences and minimizing the non-linearity between movement-amplitude and target-width. Considering spatial and/or temporal adjustments to $ID$ , we conducted regression analysis using our own and Benchmark datasets in both controlled and uncontrolled scenarios of pointing tasks with a generic mouse. ANTASID formulation showed significantly superior fitness values and throughput in all the scenarios while reducing the standard error. Furthermore, the quantification of $ID$ with ANTASID varied significantly compared to the classical formulations of Shannon’s $ID$ , validating the purpose of this study.

Background and Study Aim: The purpose of this study is to examine the specific memory representation in special skill of Basketball Free Throw in distances (set shot) except 4.5 m distance. It is aimed to examine the role of the Index of Difficulty (ID) in creating the specific memory in other distances except the distance of penalty shoots. Material: Fifteen skilled basketball players (M age = 21.6 years, SD = 2.45 years) were chosen from sixty players; they performed 70 trials from 7 different distances on the first day (10 SHOTS from each distance toward the basket). The next day, each player performed 10 SHOTS from each distance, but this time, it was different in terms of the baskets’ sizes and their quantities. Results: The result of linear regression on trials score on the first day revealed the representation of special skill in penalty point and on the second day, representation of special skill was seen in 3 different distances from the ring (manipulated ring). These results indicate that Index of Difficulty protection can be a factor of private memory representation in distances except 4.5 m distance. Conclusions: Results suggest that mass training stabilizes the ratio of target distance and width (Index of Difficulty) in mind and this ratio is the main reason of specific memory representation in basketball free throw.

ABSTRACTIntroduction Increasing numbers of people globally are affected by obesity, and the number of obese parturient women has correspondingly risen. For obese parturient women, neuraxial anesthetic procedures are generally safe. As the body mass index (BMI) increases, spinal anesthesia becomes more challenging, with a larger failure rate.Methodology A total of 383 parturient women were included in this research. They were assigned to three groups according to BMI: Group 1 included 157 women with a BMI of 40. Participants’ ages, weights, and heights were documented, and the number of attempts at inducing spinal anesthesia during labor was counted. Every new skin puncture was considered a new attempt. The success or failure of the blockade was noted.Results In pregnant participants, we found that BMI was a reliable predictor of difficulty with the neuraxial technique of inducing spinal anesthesia. We found a weakly positive correlation (r = 0.132) between BMI and the number of attempts to induce spinal anesthesia. This association was statistically significant (p = 0.01).Conclusion In pregnant patients, especially those who are obese and have a substantial amount of fatty tissue in the back, anesthesiologists should check the patient’s back thoroughly during the initial patient encounter. We also advise that anesthesia induction be carried out by an experienced senior anesthesiologist.

Increasing numbers of people globally are affected by obesity, and the number of obese parturient women has correspondingly risen. For obese parturient women, neuraxial anesthetic procedures are generally safe. As the body mass index (BMI) increases, spinal anesthesia becomes more challenging, with a larger failure rate. A total of 383 parturient women were included in this research. They were assigned to three groups according to BMI: Group 1 included 157 women with a BMI of <30; group 2 included 189 women with a BMI of 30–40, and group 3 included 37 women with a BMI of >40. Participants' ages, weights, and heights were documented, and the number of attempts at inducing spinal anesthesia during labor was counted. Every new skin puncture was considered a new attempt. The success or failure of the blockade was noted. In pregnant participants, we found that BMI was a reliable predictor of difficulty with the neuraxial technique of inducing spinal anesthesia. We found a weakly positive correlation (r = 0.132) between BMI and the number of attempts to induce spinal anesthesia. This association was statistically significant (p = 0.01). In pregnant patients, especially those who are obese and have a substantial amount of fatty tissue in the back, anesthesiologists should check the patient's back thoroughly during the initial patient encounter. We also advise that anesthesia induction be carried out by an experienced senior anesthesiologist. [ABSTRACT FROM AUTHOR]

Through mathematics, this paper works to analyse the Index of Difficulty in ISO9241-Part 411: Evaluation methods for the design of physical input devices. It was proven that all the target circles always intersect for very low Index of Difficulty; which conjectured to disturb the experiment or affect the focus of the subject. Some examples are provided, in addition, to support the proof. We hope this proof will contribute to the improvement of ISO9241, where the result might become a special attention to the designer of the experiment in human-computer interaction field; especially in checking the influence of overlap area in the human factor.

Speed-accuracy trade-offs in persons with Down syndrome and typically developing controls were tested with a Fitts' task. Movement time scaled linearly with index of difficulty in both groups, and there were no accuracy differences. Persons with Down syndrome were slower than typically developing individuals. Regression analysis on movement time and index of difficulty showed a nearly two-fold higher regression coefficient and a nearly three-fold larger intercept value in the Down syndrome group. The dwell time on a target was much longer for Down syndrome persons but scaled with index of difficulty in about the same percentage for participants in both groups. Because of differences primarily related to scaling, we conclude that mechanisms of motor control are similar in Down syndrome and typically developing groups.

Background. Brain hemispheres play different roles in the control of aiming movements that are impaired after unilateral stroke. It is not clear whether those roles are influenced by the direction and the difficulty of the task. Objective. To evaluate the influence of direction and index of difficulty (ID) of the task on performance of ipsilesional aiming movements after unilateral stroke. Methods. Ten individuals with right hemisphere stroke, ten with left hemisphere stroke, and ten age- and gender-matched controls performed the aiming movements on a digitizing tablet as fast as possible. Stroke individuals used their ipsilesional arm. The direction (ipsilateral or contralateral), size (0.8 or 1.6 cm), and distance (9 or 18 cm) of the targets, presented on a monitor, were manipulated and determined to be of different ID (3.5, 4.5, and 5.5). Results. Individuals with right hemisphere lesion were more sensitive to ID of the task, affecting planning and final position accuracy. Left hemisphere lesion generated slower and less smooth movements and was more influenced by target distance. Contralateral movements and higher ID increased planning demands and hindered movement execution. Conclusion. Right and left hemisphere damages are differentially influenced by task constraints which suggest their complementary roles in the control of aiming movements.

This study investigated the validity of Fitts' index of difficulty as a measure of task difficulty perceived by the performer. Eight subjects performed self-terminated horizontal elbow-extension movements toward targets of three indices of difficulty in two task conditions. In the target-size condition, triceps and biceps activities during acceleration and deceleration respectively decreased with increasing index of difficulty, resulting in a lower peak velocity and longer movement time. In the movement amplitude condition, however, triceps activity after movement onset and biceps activity during deceleration increased with increasing index of difficulty, resulting in a higher peak velocity. The movement time also increased as a function of the index of difficulty given increase in the distance traveled by the limb. These results suggest that Fitts' index of difficulty may not reflect the difficulty of task performance because its effect on the pattern of motor output is dependent upon the task variable manipulated in measuring the index of difficulty.