Relationship Between Flat-Water Tests and Canoe Slalom Performance on 4 Different Grades of Water Terrain Difficulty

Purpose: To assess the relationship between flat-water tests and canoe slalom performance on 4 different grades of water terrain difficulty. Methods: Nineteen elite canoe slalom athletes racing in category K1 men (n = 7), K1 women (n = 5), or C1 men (n = 7) completed flat-water tests: (1) a sprint with a turn to the preferred side, (2) a sprint with a turn to the nonpreferred side, (3) a sprint with a turn to both sides, and (4) a 12 × 15-m all-out shuttle test. Canoe slalom performance was measured in competitions with 4 different grades of water terrain difficulty. Results: There were relationships between 12 × 15-m all-out shuttle test and performance across different water terrain grades (P < .001; r = .706–.871)); however, the magnitude of the relationship decreased with increasing water terrain grade difficulty. Similar trends were observed for the sprint with a turn to the preferred side (r = .588–.884), sprint with a turn to the nonpreferred side (r = .544–.864), and sprint with a turn to both sides (r = .638–.909). In addition, small to moderate differences were observed between preferred and nonpreferred side in K1 women (P = .050, ES = 0.37), K1 men (P = .019, ES = 0.66), and C1 men (P = .003, ES = 0.69). Conclusion: The novel battery of flatwater tests can be used to measure the performance-related physical fitness of canoe slalom athletes. Sprint with a turn to the preferred side and sprint with a turn to the nonpreferred side can also be used to assess the imbalance between an athlete’s preferred and nonpreferred side. Accordingly, to our findings, practitioners could consider adapting the training program in preparation for important competitions specifically to water terrain difficulty grades where these competitions will be organized.

Expression of miRNAs in Serum Exosomes versus Hippocampus in Methamphetamine-Induced Rats and Intervention of Rhynchophylline

Objective. To compare the expressions of miRNAs (microRNAs) in serum exosomes and in hippocampus and to provide insights into the miRNA-mediated relationship between peripheral and central nervous systems in the presence of methamphetamine. Methods. Published results on conditioned place preference (CPP) in rats conditioned by methamphetamine were replicated. The expressions of miRNAs in serum exosomes and hippocampus were determined by gene-chip sequencing. We then predicted the potential target genes of selected, differentially expressed (DE) miRNAs and then carried out functional analysis of these target genes. We also verified our results by RT-qPCR. Results. Methamphetamine reward could greatly increase the activity time and distance in the intrinsically nonpreferred side of the behavioral apparatus compared with control rats (P<0.01). Rhynchophylline treatment significantly counteracted these changes (P<0.01). Methamphetamine-induced CPP upregulated 23 miRNAs (log2 fold change [FC] > 1, P<0.01) in serum exosomes, whereas rhynchophylline treatment could downregulate these miRNAs (log2 FC < −1, P<0.01). Analysis of hippocampal miRNAs profiles found 22 DE miRNAs (log2 FC > 1 or <−1, P<0.01). When methamphetamine induced CPP, 11 of those miRNAs were upregulated, whereas rhynchophylline treatment could downregulate these miRNAs. The other 11 miRNAs behaved in the opposite way. We selected six DE miRNAs from each of serum exosomes and hippocampus for target gene prediction and functional analysis. We found that, in both, the DE miRNAs and their target genes may be related to neuronal information transmission and synaptic transmission. Conclusions. Rhynchophylline blocked the alteration of behavior and the expression of some DE miRNAs induced by methamphetamine. The biological functions of these DE miRNAs target genes are correlated between serum exosomes and hippocampus. As to these biological processes and pathways which are involved in the development of addiction at multiple stages, we speculate that these DE miRNAs in serum exosomes and hippocampus are closely related to methamphetamine addiction.

Intracyclic Velocity Variation and Arm Coordination Assessment in Swimmers With Down Syndrome

This study examined the differences in intracycle velocity variation and arm coordination in front crawl in swimmers with Down syndrome in three breathing conditions. International swimmers with Down syndrome (N = 16) performed 3 × 20 m front crawl at 50 m race speed: without breathing, breathing to the preferred side, and breathing to the nonpreferred side. A two dimensional video movement analysis was performed using the APASystem. Breathing conditions were compared using Repeated Measures ANOVA. Swimming velocity was higher without breathing and intracyclic velocity variation was higher while breathing. Swimmers tended to a catch up arm coordination mode for both breathing conditions and a superposition mode when not breathing. These data reflect arm coordination compromising swimming performance, particularly when comparing with non disabled swimmers in literature. The physical and perhaps cognitive impairment associated with Down syndrome may result in a disadvantage in both propulsion and drag, more evident when breathing.

Position-specific adaptation in simple cell receptive fields of the cat striate cortex

1. Responses of simple cells in cat striate cortex were studied with flashed light-slit stimuli. The responses to bars flashed in different positions in the receptive field were assessed quantitatively before and after periods of prolonged stimulation of one small region. This type of prolonged stimulation resulted in reduced responsivity over a limited zone within the simple cell receptive field. 2. The adaptation-induced responsivity decrement was generally confined to the receptive-field subregion that was adapted (either ON or OFF). Prolonged stimulation within an ON region did not usually result in adaptation effects that spread into neighboring OFF regions. Furthermore, the adaptation-induced response decrement did not necessarily spread throughout the subregion in which the adapting stimulus was presented. The adaptation effects from prolonged stimulation at a single receptive-field position spread throughout the subregion in nearly one-half of the 25 cells examined for position-specific adaptation. Another subpopulation of neurons (n = 12) displayed adaptation effects that spread through only one-half of the subregion, whereas in two neurons the spread of the adaptation effect was even more restricted and encompassed only one-fourth of the subregion. 3. The spread of adaptation was not systematically related to the size of the stimulus presented, the size of the receptive field, or the magnitude of the adaptation-induced response decrements but was significantly correlated with the spatial wavelength of the cell (the reciprocal of the cell's preferred spatial frequency) and with the size of the subregion in which the adapting stimulus was presented. Cells with large receptive-field subregions and long wave-lengths showed adaptation effects that spread further than those of cells with small subregions. 4. The adaptation effects from repeated stimulation at a single receptive-field position did not spread symmetrically across the receptive field, and the preferred direction of motion for a given cell indicated the direction of the asymmetric spread of the adaptation. Receptive-field positions that would be stimulated by a light slit originating at the point of adaptation and moving in the preferred direction (preferred side) showed greater adaptation-induced response decrements than did receptive-field positions that would be stimulated by a light slit moving in the opposite direction from the point of adaptation (nonpreferred side). There was significant enhancement of responses at some receptive-field positions on the nonpreferred side of the point of adaptation.(ABSTRACT TRUNCATED AT 400 WORDS)

EMG-Reaction Time of the Biceps Brachii in Bilateral Simultaneous Motions

EMG-RTs of the biceps brachii muscles were measured using electromyogram (EMG) in elbow flexion and forearm supination on 18 right-and 24 left-handed subjects for four tasks, flexion or supination (symmetrical) and flexion of one and supination of the other side (asymmetrical). For both subject groups, the EMG-RTs of flexion for both hands were not prolonged under asymmetrical tasks, but the EMG-RTs of supination were significantly prolonged on both sides. Comparing the coefficients of determination of the EMG-RTs of flexion to those of supination under four different tasks, those of the preferred hand for symmetrical and asymmetrical motions did not differ, but those of the nonpreferred side for asymmetrical motions were smaller than those for symmetrical motions in both subjects. These observations indicated prolongation of EMG-RT on the asymmetrical task was larger on supination than on flexion. It was suggested that the influence of strong timing constraints was greater on the auxiliary function than on the innate function of the biceps (elbow flexor). The steadiness of motor function of the preferred hand was also discussed in regard to hand preference.

Secondary Reinforcement Based on Primary Brain Stimulation Reward

15 rats were trained to run in a straight runway for rewarding brain stimulation (ESB). A consistent color of goal box—ESB reward pairing existed during runway training. When subsequently rested in a T-maze where the goal box associated with ESB was placed on the initially nonpreferred side, Ss learned to run to that side with only the goal-box color as the reward. The results are held to conclusively demonstrate that secondary reward can be based on ESB as a primary reward. Also, results appear to challenge the view that drive is necessary for the demonstration of secondary reward.