Visuo-motor learning with combination of different rates of motor imagery and physical practice

Sports psychology suggests that mental rehearsal facilitates physical practice in athletes and clinical rehabilitation attempts to use mental rehearsal to restore motor function in hemiplegic patients. Our aim was to examine whether mental rehearsal is equivalent to physical learning, and to determine the optimal proportions of real execution and rehearsal. Subjects were asked to grasp an object and insert it into an adapted slot. One group (G0) practiced the task only by physical execution (240 trials); three groups imagined performing the task in different rates of trials (25%, G25; 50%, G50; 75%, G75), and physically executed movements for the remaining trials; a fourth, control group imagined a visual rotation task in 75% of the trials and then performed the same motor task as the others groups. Movement time (MT) was compared for the first and last physical trials, together with other key trials, across groups. All groups learned, suggesting that mental rehearsal is equivalent to physical motor learning. More importantly, when subjects rehearsed the task for large numbers of trials (G50 and G75), the MT of the first executed trial was significantly shorter than the first executed trial in the physical group (G0), indicating that mental practice is better than no practice at all. Comparison of the first executed trial in G25, G50 and G75 with the corresponding trials in G0 (61, 121 and 181 trials), showed equivalence between mental and physical practice. At the end of training, the performance was much better with high rates of mental practice (G50/G75) compared to physical practice alone (G0), especially when the task was difficult. These findings confirm that mental rehearsal can be beneficial for motor learning and suggest that imagery might be used to supplement or partly replace physical practice in clinical rehabilitation.     

Spatial navigation in the Morris water maze: working and long lasting reference memories

Spatial navigation development in the Morris water maze (MWM) paradigm was studied in 70-day-old male Long-Evans hooded rats. During 5 consecutive days, rats' training consisted of a daily block of 10 trials. Escape latency was measured in each trial. Probe testing was performed every day immediately before and after the daily block of trials. In addition, a final probe was performed on Day 6. During the first 3 days of training, the escape latency became progressively shorter, showing an asymptotic trend on Days 4 and 5. Probe trials administered at the end of the first acquisition sessions showed clear preference for the target quadrant but this information was not recalled at probe trials given 24h later. The memory trace retrieved after 24-h delay was formed only after 30 trials received over three sessions. The probe trial given at the end of an acquisition session tests the efficiency of the working memory whereas the 24h delayed probe trial reflects better-consolidated spatial information corresponding to long lasting reference memory. It can be noted that the progressive shortening of escape latencies does not express closely the evolution of the rat's long lasting (consolidated) reference memory. This memory can be satisfactorily measured only by probe testing performed at an adequate delay after training. These considerations may be of some interest when interpreting the rat's performance in the MWM.     

A trial of detecting impending access-graft failure by simplified weekly flow monitoring

Access graft failure is a major problem in hemodialysis. Monitoring the flow through the access so that impending failure can be detected and prevented seems reasonable, but recent clinical trials have failed to show any benefit of such monitoring. Described here are plans for a clinical trial of a new flow monitoring procedure that measures access flow weekly instead of monthly and, being performed before dialysis, avoids the dialysis-induced changes in graft flow that may have affected earlier trials. The planned trial is to be carried out in two stages, the first to establish the sensitivity and specificity of the new method, and the second (if the results of the first stage warrant it) a controlled trial comparing access-costs and hospitalization days between a monitored group and a matched standard care control group. It is hoped that this trial of the new method will establish it as an effective means of extending access-graft life.     

Temporally graded, age-related impairments in spatial memory in the rat

We report here on the analysis of data from 6-, 12-, and 24-month-old Long-Evans rats tested in the Morris water maze. The animals were given 18 trials over a 5-day period with the platform submerged (spatial condition); 3 trials on the first day, 4 trials on each of the subsequent 3 days, followed by 3 trials on the fifth day. On the sixth day, the animals were given five trials in which the platform was elevated above the water level (cued condition). Over the 18 trials in the spatial condition, the 24-month-old animals took significantly longer to find the platform than did the 6-month-old animals; the performance of the 12-month-day animals lay between the older and younger groups. We then analyzed the latency data depending on the position of the trial in that day of testing: The first trial of each day followed the preceding trial by 20-22 hours, whereas the last trial of each day followed the preceding trial by only 20 minutes. The performance of the 12-month-old animals on the first trial of the second, third, and fourth days of testing was indistinguishable from that of the 24-month-old animals. Whereas, the performance of the 12-month-old animals on the last trial of the second, third, and fourth days of testing was indistinguishable from that of the 6-month-old animals. An analysis of the distance data (distance covered before locating the platform) revealed the same pattern of results.(ABSTRACT TRUNCATED AT 250 WORDS)     

A tale of two studies: the importance of setting, subjects and context in two randomized, controlled trials of a web-based decision support for perimenopausal and postmenopausal health decisions

OBJECTIVE: Knowledge relevant to women's peri- and postmenopausal health decisions has been evolving rapidly. Web-based decision supports can be rapidly updated and have the potential to improve the quality of patients' decisions. We developed and tested a web-based decision support for peri- and postmenopausal health decisionmaking. METHODS: We recruited 409 women aged 45-75 for one randomized, controlled trial and 54 women with an upcoming clinic appointment for a subsequent trial. Women were randomized to use the web-based decision support versus a printed brochure (first trial) and usual care (second trial). Outcomes were changes in decisional satisfaction, decisional conflict, and knowledge, both within each trial and compared across the trials. RESULTS: Intervention subjects had greater increases in decisional satisfaction in the second trial and knowledge in both trials. A high dropout rate among women randomized to the website in the first trial effectively negated benefits in that trial, but not in the second. CONCLUSIONS: The utility of this web-based decision support in two trials depended on a number of factors that appear related to the urgency of making a decision. PRACTICE IMPLICATIONS: Decision aids should be targeted to patients actively trying to make a decision.     

Effects of swimming with a wet suit on energy expenditure during subsequent cycling.]

The aim of this study was to investigate the effects of swimming with a wetsuit on energy expenditure during subsequent cycling. Nine well-trained triathletes underwent three submaximal trials. The first trial (SC) consisted of a 750-m swim realised at a competition pace, followed by a 10-min cycling exercise at a power output corresponding to the ventilatory threshold . The two other trials were composed of the same cycling exercise, preceded either by a 750-m swim with a wetsuit (WSC) or by a cycling warm-up (Ctrl). The main results are that the WSC trial was characterised by significantly lower swimming cadence (-14%), heart rate (-11%), and lactate values (-47%) compared to the SC trial, p < 0.05. Moreover, cycling efficiency was significantly higher in the WSC trial compared to the SC trial (12.1% difference, p < 0.05). The lower relative intensity observed during swimming with a wetsuit suggest the relative importance of swimming condition on the total performance in a sprint triathlon.     

A paradigm for measuring the olfactory event-related potential in the clinic

Recent research on the olfactory event-related potential (OERP) using inter-stimulus intervals (ISIs) of 90 s and shorter has revealed a marked decrease in component amplitude after the first trial, with a leveling off for the remaining trials. Studies manipulating the ISI in olfactory and other modalities demonstrate an association between higher amplitudes and longer ISIs, suggesting that habituation occurs at short time intervals between each stimulus presentation. The present study attempted to reduce the effects of habituation by using a 10-min ISI and fewer trials. OERPs were recorded monopolarly at the Fz, Cz and Pz electrode sites in ten subjects (five males, five females), for three trials using a 10-min ISI. Results demonstrated no significant reduction in component amplitudes across trials and no significant difference in latencies over trials, indicating no habituation effect at this ISI. These results indicate that with a 10-min ISI and three trial recordings, a complete reduction in habituation can be achieved. These findings may prove to be clinically useful to physicians who can implement this technique to assess olfactory functioning in cognitively impaired individuals or to assess malingering.     

Persistence of spatial memory in the Morris water tank task

Persistence of the spatial memory record was examined in 30 rats overtrained in the working memory version of the Morris water tank task. In Experiment 1, the animal had to find during the acquisition trial an invisible underwater platform randomly located at one of 4 possible sites in the pool. Retention test was performed 1 min, 60 min, 4 h or 24 h later with the same position of the platform and same or changed position of the start. Whereas in the acquisition trials the rats reached the goal after 12 s on average, the latency in the retrieval trials increased with the acquisition-retrieval interval. It was 5 s with the 1-min delay and exponentially approached, but did not quite reach the acquisition trial latency with the 24-h delay. In Experiment 2 the rats were started from the same position of the tank to goal positions changing from trial to trial in a prearranged sequence. There were either 1-h or alternating 1-min and 2-h intervals between the 6 daily trials. The latencies were long during the first trial and whenever the goal changed and short when the goal remained the same as on the previous trial. The latencies were not significantly influenced by intertrial interval in the 1 min to 2 h range. It is concluded that the decay of spatial memory in the water tank task is slow and is little affected by proactive interference.     

The transitive fallacy for randomized trials: If A bests B and B bests C in separate trials, is A better than C?

Background

If intervention A bests B in one randomized trial, and B bests C in another randomized trial, can one conclude that A is better than C? The problem was motivated by the planning of a randomized trial, where A is spiral-CT screening, B is x-ray screening, and C is no screening. On its surface, this would appear to be a straightforward application of the transitive principle of logic.

Methods

We extended the graphical approach for omitted binary variables that was originally developed to illustrate Simpson's paradox, applying it to hypothetical, but plausible scenarios involving lung cancer screening, treatment for gastric cancer, and antibiotic therapy for clinical pneumonia.

Results

Graphical illustrations of the three examples show different ways the transitive fallacy for randomized trials can arise due to changes in an unobserved or unadjusted binary variable. In the most dramatic scenario, B bests C in the first trial, A bests B in the second trial, but C bests A at the time of the second trial.

Conclusion

Even with large sample sizes, combining results from a previous randomized trial of B versus C with results from a new randomized trial of A versus B will not guarantee correct inference about A versus C. A three-arm trial of A, B, and C would protect against this problem and should be considered when the sequential trials are performed in the context of changing secular trends in important omitted variables such as therapy in cancer screening trials.     

The effect of ECS upon spontaneous alternation in rats

Rats were given two pairs of unreinforced trials in a Y-maze with one hour between trials of a pair. It was found that ECS given immediately after the first trial of a pair did not reduce the rat's tendency to alternate on the second trial, although ECS was shown to impair passive avoidance learning in the same apparatus. It is argued that spontaneous alternation involves a kind of memory, and that these results show that this memory is not affected by ECS. This conclusion is discussed in relation to the hypothesis that ECS produces retrograde amnesia.     

Fatigue profile: a numerical method to examine fatigue in cycle ergometry

Fatigue Profile, a new numerical method for characterising fatigue in isokinetic cycle ergometry is presented and compared with the conventional fatigue index (FI). The new method describes the temporal development of muscle fatigue based on the decline of peak power output throughout a whole trial. The advantage of this method is demonstrated by the analysis of two 25?s maximum trials, separated by 90?s recovery, performed by a well-trained athlete at a pedal frequency of 120 revolutions per minute. A fourth degree polynomial was fitted to model the peak power data. Using the polynomial model coefficients the first derivative represented the rate of changing peak power which represented the Fatigue Profile. The conventional FI was calculated as ?35?Ws^?1 and ?32?Ws^?1 for trials 1 and 2 respectively, indicating minor differences in fatigue between trials. In contrast the Fatigue Profile revealed important numeric and temporal differences between the trials. For trial 1 a maximum rate of peak power decline of ?65?Ws^?1 was reached at approximately 6?s into the trial. In marked contrast, in trial 2, maximum rate of peak power decline (?146?Ws^?1) occurred immediately. The Fatigue Profile approach allows the characterisation of the temporal development of fatigue under different experimental conditions and in combination with other techniques may yield further insight into the underlying mechanisms of fatigue.     

Therapeutic Trials in HIV Infection: Which Benefits for Which Patients?

Abstract

Purpose: The purpose of our study was to make an assessment of the HIV patients’ overall opinion of therapeutic trials, to analyze the motivations and the reasons linked to this perception, and to determine if their involvement in a therapeutic trial is a help or a hindrance to their treatment. Method: All the inpatients and outpatients attending the Dijon University Hospital AIDS day care unit during the first 4 months of 1999 were given an anonymous questionnaire designed to record the patients’ attitudes toward therapeutic trials, their motivations, and the perceived risks. The questionnaire was often completed in consultation with a psychoanalyst. Results: Two hundred and seven (207) patients were surveyed; 194 of them had a favorable opinion of therapeutic trials. The main motivations to take part in a therapeutic trial were altruistic. In contrast, individualistic considerations and relational motivations (such as to modify the relationship between the caregiver and the patient) were more closely associated with a negative perception. Conclusion: Most of the patients will benefit or at least will not be harmed by being involved in a trial. However, the patients’ attitudes toward the principle of therapeutic trials have to be determined before these patients are included in a given therapeutic trial. This is necessary to avoid the risk of subsequent medical care being altered because participation was either induced or compelled.     

The effect of even,positive and negative pacing on metabolic,kinematic and temporal variables during breaststroke swimming

The aim of this investigation was to determine the effect of even, negative and positive pacing on metabolic, kinematic and temporal variables during breaststroke swimming. Nine male swimmers [mean (SD): age 21 (3) years, height 178 (5) cm, body mass 77.2 (6.7) kg, 200 m-time 158.6 (13.6) s] completed a 200-m breaststroke time trial and then 72 h later three paced (even, positive, negative) 175-m breaststroke swims in random order, 48 h apart. The swimmers paced accurately in all trials. The evenly paced trial produced lower post-exercise peak blood lactate and rating of perceived exertion values compared to the positively paced trial (P<0.05). Peak oxygen uptake was not significantly different between trials (P>0.05). Heart rate immediately following exercise was lower in the negatively paced trial (P<0.05) than the other paced trials. Stroke rates were lower during the first half of the evenly and negatively paced trials compared to the positively paced trial (P<0.01), but no differences were observed between the second half of the trials. Across all trials the stroke count increased as the trials progressed (P<0.01). Turning times were observed to be shorter during the first half of the positively paced trial compared to the other paced trials (P<0.01). Even paced swimming appears to be less physically stressful than positively paced swimming during high intensity exercise, as indicated by a lower post-exercise blood lactate concentration, perceived exertion and variability within turning times. Electronic Publication     

Reward improves working memory of rats in the radial maze

The effect of reward on the formation and retention of short-term memory traces was examined in the radial maze. In Experiment 1, overtrained rats (n=12) made fewer errors (0.45 errors/trial) in an empty than in a baited 12-arm maze (1.19 errors/trial). In Experiment 2, two-min interval between the first six and second six choices only slightly increased error incidence in rewarded trials (1.33 errors/trial), but significantly deteriorated performance in non-rewarded trials (2.48 errors/trial). In Experiment 3, restricting the reward and non-reward conditions to the first six (R-N) or last six (N-R) choices of a trial only slightly impaired performance (about 1.5 errors/trial). In Experiment 4, rats were rewarded or non-rewarded in the first six choices made in maze A or in the second six choices performed in the similar maze B. The performances in the second six choices were close to chance in the AN-BN and AR-BN conditions (2.58 errors/trial) and intermediate in the AR-BR and AN-BR conditions (1.91 and 2.04 errors/trial, respectively). The positive effect of reward was not eliminated by the change of apparatus and cannot be due, therefore, to more intense scent marking. It is concluded that anticipated or accomplished consummatory activity improves efficiency of the working memory.     

Updating the programming of a precision grip is a function of recent history of available feedback

In a recent study (Whitwell et al. in Exp Brain Res 185:111–119, 2008), we showed that the visuomotor system is “cognitively impenetrable” to the extent that explicit predictive knowledge of the availability of visual feedback on an upcoming trial fails to optimize grasping. The results suggested that the effects of trial history, rather than the anticipatory knowledge of the nature of an upcoming trial, plays the most significant role in how the availability of visual feedback is exploited by the visuomotor system when programming grip aperture (e.g., opening the hand wider when visual feedback is unavailable). Here, we provide direct evidence that trial history indeed plays a critical role in the programming of grip aperture. Twelve individuals grasped objects of three different sizes placed at one of two distances either with or without visual feedback of the hand and object (closed- or open-loop trials, respectively). Runs of four consecutive closed- or open-loop trials were interleaved with sequences of closed and open-loop trials that alternated back and forth from trial to trial. Peak grip aperture (PGA) decreased linearly with successive closed-loop trials and increased linearly with successive open-loop trials. We also compared PGA for trials that were preceded by a run of four consecutive closed- (or open-loop) trials with trials that were preceded by only one closed- (or open-loop) trial. This analysis indicated that consistency in the runs of closed- or open-loop trials significantly reduced the effect of the availability of feedback on grasping in the trial following the run. We conclude that while the margin of error observed in precision grasping is largely a function of the availability of visual feedback on the current trial, it is evidently also a function of the recent history of the availability of visual feedback on previous trials.     

Paradoxical fall in repetitive learning of a random series of digits

In this study, on each trial subjects were presented visually a different random series of nine digits, and required to memorize and recall them immediately. Among a sequence of trials there were three repetitive learning trials, a few trials apart one from another. On these trials an identical series of nine digits was presented repeatedly. Recall rates of the series of digits on repetitive learning trials rose from the first trial to the second, and, by contraries, fell on the third. We call this fall "paradoxical fall," since it is contrary to the expectation of standard theories of learning. It was pointed out that we should investigate the detailed cognitive process, i.e., the microcognitive process, in learning.memory of simple series of digits, because it involves the important basic cognitive process of learning.memory.     

Hyperprolactinaemia during prolonged exercise in the heat: evidence for a centrally mediated component of fatigue in trained cyclists

Several lines of evidence suggest that central serotoninergic neurons may mediate fatigue signals during prolonged exercise. In this study we examined the effects of diet and ambient temperature on peripheral modulators and indices of serotoninergic function and their relationship to exercise performance. Six well-trained cyclists participated, in randomised order, in two diet and exercise regimens each lasting 8 days and comprising four cycle tests to exhaustion at 70 % of maximum oxygen uptake. On days 1 and 5, subjects exercised to exhaustion to deplete muscle glycogen. For 3 days after the first depletion trial a diet providing 10 % of energy in the form of carbohydrate (CHO) was consumed (low CHO), and for 3 days after the second depletion trial a diet providing 80 % (high CHO) of energy as CHO was consumed, and each diet was followed by a performance trial at the same ambient temperature, either 10 degrees C or 30 degrees C (days 4 and 8). This schedule was repeated after 1 week, but performance trials were carried out at the other ambient temperature. In the cold, cycling time increased (P < 0.01) from 89.2 (78.0-129.5) min (median (range)) in the low CHO trial to 158.2 (116.9-165.6) min in the high CHO trial. In the heat, cycling time increased from 44.0 (31.8-51.4) min in the low CHO trial to 53.2 (50.2-82.2) min on the high CHO trial (P = 0.02). The serum prolactin (Prl) concentration was higher at exhaustion during the two trials in the heat than in the two trials in the cold. Serum Prl levels were unrelated to the purported peripheral modulators of serotoninergic function (plasma concentrations of total tryptophan (Trp), free Trp, branched-chain amino acids (BCAAs), free Trp/BCAA ratio and total Trp/BCAA ratio) but were significantly related to the rectal temperatures measured during the two trials in the heat. This finding provides indirect evidence that the serotoninergic system may be involved in fatigue during exercise under conditions of heat stress.     

Do we use a priori knowledge of gravity when making elbow rotations?

In this study, we aim to investigate whether motor commands, emanating from movement planning, are customized to movement orientation relative to gravity from the first trial on. Participants made fast point-to-point elbow flexions and extensions in the transverse plane. We compared movements that had been practiced in reclined orientation either against or with gravity with the same movement relative to the body axis made in the upright orientation (neutral compared to gravity). For each movement type, five rotations from reclined to upright orientation were made. For each rotation, we analyzed the first trial in upright orientation and the directly preceding trial in reclined orientation. Additionally, we analyzed the last five trials of a 30-trial block in upright position and compared these trials with the first trials in upright orientation. Although participants moved fast, gravitational torques were substantial. The change in body orientation affected movement planning: we found a decrease in peak angular velocity and a decrease in amplitude for the first trials made in the upright orientation, regardless of whether the previous movements in reclined orientation were made against or with gravity. We found that these decreases disappeared after participants familiarized themselves with moving in upright position in a 30-trial block. These results indicate that participants used a general strategy, corresponding to the strategy observed in situations with unreliable or limited information on external conditions. From this, we conclude that during movement planning, a priori knowledge of gravity was not used to specifically customize motor commands for the neutral gravity condition.     

Alpha- and Theta-Range Cortical Synchronization and Corticomuscular Coherence During Joystick Manipulation in a Virtual Navigation Task

Previous studies have reported that multiple brain regions are activated during spatial navigation, but it remains unclear how this activation is converted to motor commands for navigation. This study was aimed to investigate synchronization across different brain regions and between cortical areas and muscles during spatial navigation. This synchronization has been suggested to be essential for integrating activity in the multiple brain areas to support higher cognitive functions and for conversion of cortical activity to motor commands. In the present study, the subjects were required to sequentially trace ten checkpoints in a virtual town by manipulating a joystick and to perform this three times while electroencephalograms and electromyograms from the right arm were monitored. Time spent on the task in the third trial was significantly lesser than that in the first trial indicating an improvement in task performance. This repeated learning was associated with an increase in alpha power at the electrodes over the contralateral sensorimotor region and in theta power at the electrodes over the bilateral premotor and frontotemporal regions. Alpha- and theta-range corticocortical coherences between these regions and other brain areas were also increased in the third trial compared to the first trial. Furthermore, alpha- and theta-range corticomuscular coherence was significantly increased in the second and third trials compared to the first trial. These results suggest that alpha- and theta-range synchronous activity across multiple systems is essential for the integrated brain activity required in spatial navigation and for the conversion of this activity to motor commands.     

Movement reduces the dynamic response of muscle spindle afferents and motoneuron synaptic potentials in rat

Among the mechanisms that may result in modulation of the stretch reflex by the recent history of muscle contraction is the history dependence observed under some conditions in the response properties of muscle spindles. The present study was designed to test one report that in successive trials of muscle stretch-release, spindle afferent firing during stretch, i.e., the dynamic response shows no history dependence beyond the initial burst of firing at stretch onset. Firing responses of spindle afferents were recorded during sets of three consecutive trials of triangular stretch-release applied to triceps surae muscles in barbiturate-anesthetized rats. All 69 spindle afferents fired more action potentials (spikes) during the dynamic response of the first trial, excluding the initial burst, than in the following two trials. The reduced dynamic response (RDR) was nearly complete after trial 1 and amounted to an average of approximately 12 fewer spikes (16 pps slower firing rate) in trial 3 than in trial 1. RDR was sensitive to the interval between stretch sets but independent of stretch velocity (4-32 mm/s). RDR was reflected in the synaptic potentials recorded intracellularly from 16 triceps surae alpha-motoneurons: depolarization during muscle stretch was appreciably reduced after trial 1. These findings demonstrate history dependence of spindle afferent responses that extends throughout the dynamic response in successive muscle stretches and that is synaptically transmitted to motoneurons with the probable effect, unless otherwise compensated, of modulating the stretch reflex.