Successive Test Sessions Research Articles

Ramadan Fasting and Short-Term Maximal Physical Performance: Searching for Optimal Timing of the Last Meal "Suhoor" in Female Pre-University Handball Players.

Aiming to identify the ideal suhoor timing for maintaining optimal physical performance and health indicators during Ramadan intermittent fasting, the present study compares the effects of early vs. late Suhoor on short-term high-intensity physical exercise while controlling the body mass index (BMI) oral temperature (OT), dietary intake, and sleep patterns. In a randomized design, 19 female pre-university handball players (age: 16.8 ± 0.4 y; height: 1.70 ± 0.9 m; and body mass: 61.5 ± 6.9 kg) underwent two test sessions (at 08:00 a.m. and 05:00 p.m.) at four different conditions: ten days prior to Ramadan (R - 10), the final ten days of Ramadan (R) including both Early Suhoor R(ES) and Late Suhoor R(LS) conditions, and the ten days immediately following Ramadan (R + 10). A recovery period of at least 48 h has been set between successive test sessions at each period. Outcome measures included the Countermovement Jumps Test (CMJ), Modified Agility t-Test (MATT), Repeated Sprint Ability (RSA), and Rating of Perceived Exertion (RPE). The Pittsburgh Sleep Quality Index (PSQI), OT, BMI, and daily diary intake were assessed across the three periods. The total scores of PSQI decreased significantly during R and R + 10 compared to R - 10. When performed in the afternoon, CMJ, MATT, and RSA performance decreased significantly at R(ES) and R(LS) conditions compared to R - 10. However, these performances decreased only after R(ES) when performed in the morning. Furthermore, performances were lower during R(ES) compared to R(LS) in the afternoon for all tests and the morning for MATT and RSA tests. These findings support prior research showing a deterioration of physical performance during Ramadan fasting and indicate a more pronounced impact following early Suhoor condition. Therefore, consuming a late suhoor, closer to pre-dawn time, could be suggested as an effective strategy to minimize physical performance decline during short-term high-intensity exercise.

Blink duration is increased in concussed youth athletes: a validity study using eye tracking in male youth and adult athletes of selected contact sports

Objective. Diagnosing a sports-related concussion (SRC) remains challenging, and research into diagnostic tools is limited. This study investigated whether selected eye tracking variables would be a valid tool to diagnose and monitor SRC in adult and youth participants in selected contact sports, such as Rugby Union (rugby) and football (soccer). Methods. This prospective cohort study, with 70 concussed and 92 non-concussed adult and youth athletes, assessed the validity of five previously selected eye tracking variables for SRC diagnostics and management. The performance between concussed and age-matched control (non-concussed) athletes, as well as between three successive testing sessions in the concussed athletes were compared. Self-paced saccade count in adult group; blink duration in the memory-guided saccade and sinusoidal smooth pursuit tasks, proportion of antisaccade errors, and gain of diagonal smooth pursuit in the youth group were assessed. Results. The youth concussed group had higher blink duration in the fast memory-guided saccades task (p = 0.001, η 2 = 0.17) and a tendency for higher blink duration in the sinusoidal smooth pursuit task (p = 0.016, η 2 = 0.06) compared to the youth control group. In both tasks the blink duration in the concussed youth group decreased from session 1 to session 2 by 24% and 18%, accordingly, although statistical significance was not reached. The concussed adult group demonstrated a lower number of self-paced saccades compared to controls (p = 0.05, η 2 = 0.09), which gradually increased, with the largest difference between session 1 and session 3 (p = 0.02). Conclusions. Blink duration in youth athletes holds promise as a valid metric for concussion diagnostics and monitoring. It is recommended to focus future studies on comparing eye tracking performance within the same concussed athletes over time rather than comparing them to healthy controls.

Do capuchin monkeys engage in calculated reciprocity?

Most research on reciprocal cooperation aims to either investigate the conditions that allow its evolution or to document actual cases of reciprocity, while the study of its proximate mechanisms is often neglected. Here, we report on an experiment aimed at testing one of the proximate mechanisms that have been proposed to underlie reciprocal cooperation. We tested ‘calculated reciprocity’, according to which animals behave cooperatively towards conspecifics driven by the expectation of a return of the favour. We examined food sharing in pairs of tufted capuchin monkeys, Sapajus spp., tested in three different experimental conditions. In the first condition (Reciprocity), we gave the subject some less preferred food that could be shared with the partner and, in a following phase, we gave the partner some preferred food that could be shared with the subject. In the second condition (Control), we gave the subject some less preferred food that could be shared with the partner, but the partner did not have the opportunity to reciprocate. In the third condition (Rewarded Cooperation), we gave the subject some less preferred food that could be shared with the partner, and then we gave the subject a quantity of preferred food proportional to the amount shared with the partner during the test. There was no difference between the three experimental conditions in the amount of food transferred from the subject to the partner. However, in the Rewarded Cooperation condition, capuchin monkeys increased the amount of food shared over successive test sessions. Although it remains undemonstrated whether the subjects understood the differences between the three experimental conditions, our results suggest that the expectation of reciprocation did not motivate capuchin monkeys to share their food. Capuchin monkeys seemed, however, able to learn that sharing can lead to a reward. • We tested whether expectation of reciprocation motivates food sharing in monkeys. • Monkeys did not share more food when their partner was able to reciprocate. • We conclude capuchin monkeys do not engage in calculated reciprocity.

The Impact of Situational Test Anxiety on Retest Effects in Cognitive Ability Testing: A Structural Equation Modeling Approach.

When a cognitive ability is assessed repeatedly, test scores and ability estimates are often observed to increase across test sessions. This phenomenon is known as the retest (or practice) effect. One explanation for retest effects is that situational test anxiety interferes with a testee’s performance during earlier test sessions, thereby creating systematic measurement bias on the test items (interference hypothesis). Yet, the influence of anxiety diminishes with test repetitions. This explanation is controversial, since the presence of measurement bias during earlier measurement occasions cannot always be confirmed. It is argued that people from the lower end of the ability spectrum become aware of their deficits in test situations and therefore report higher anxiety (deficit hypothesis). In 2014, a structural equation model was proposed that specifically allows the comparison of these two hypotheses with regard to explanatory power for the negative anxiety–ability correlation found in cross-sectional assessments. We extended this model for usage in longitudinal studies to investigate the impact of test anxiety on test performance and on retest effects. A latent neighbor-change growth curve was implemented into the model that enables an estimation of retest effects between all pairs of successive test sessions. Systematic restrictions on model parameters allow testing the hypothetical reduction in anxiety interference over the test sessions, which can be compared to retest effect sizes. In an empirical study with seven measurement occasions, we found that a substantial reduction in interference upon the second test session was associated with the largest retest effect in a figural matrices test, which served as a proxy measure for general intelligence. However, smaller retest effects occurred up to the fourth test administration, whereas evidence for anxiety-induced measurement bias was only produced for the first two test sessions. Anxiety and ability were not negatively correlated at any time when the interference effects were controlled for. Implications, limitations, and suggestions for future research are discussed.

Generalized Identity Matching to Sample after Multiple-Exemplar Training in Capuchin Monkeys.

A multiple-exemplar identity matching-to-sample baseline was established to encourage development of generalized IDMTS performances in three adult male capuchins. Mask (blank comparison) or Shuffled S- procedures were used to promote select (sample-S+) control in baseline relations and to assess stimulus control relations in generalized IDMTS tests. The IDMTS baseline comprised eight 3-stimulus sets or four 4-stimulus sets. Probe trials with new stimulus sets were substituted for baseline sets in successive testing sessions and subsequently converted to new baseline relations. All monkeys exhibited high accuracy on generalized IDMTS tests. A monkey who was given the Mask procedure in training and tests showed generalized IDMTS with select relations predominating. Two monkeys who were given training and testing with the Shuffled S- procedure performed somewhat better on Shuffled S- IDMTS test trials than on test trials that contained non-shuffled test IDMTS trials thus suggesting that exclusion of familiar nonmatching comparison stimuli from baseline in Shuffled S-test trials contributed to the higher accuracy scores with the former procedures. Development of select relations appeared to be a positive predictor of development of generalized IDMTS.

A note on pigs’ knowledge of hidden objects

Abstract. Object permanence is the notion that objects continue to exist even when they are out of observer´s sight. This ability is adaptive not only for free ranging animals who have to cope with a dangerous and highly changeable environment, allowing them to be aware of predators sneaking in their proximity or to keep track of conspecifics or food sources, even when out of sight. Farm animals, too, might profit from object permanence as the ability to follow the trajectory of hidden food or objects may lead to a higher predictability of subjects' environment, which in turn might affect the level of stress under husbandry conditions. We conducted two experiments to examine the ability of object permanence in young domestic pigs (Sus scrofa domestica). For this purpose we used a test setup that was formerly developed for primates and adopted it to the behavioural constraints of pigs. A rewarded object was hidden in one of three hiding locations with an increasing complexity of the objects movement through successive test sessions. Subjects were confronted with visible and invisible displacement tasks as well as with transpositions of hidden objects in different contextual settings. Pigs solved visible, but not invisible displacements or transpositions, indicating that they have difficulties to keep track of once hidden and then moved objects. This should be taken into account when designing husbandry environments or study designs.

Subthalamic Nucleus Deep Brain Stimulation Does Not Improve Visuo-Motor Impairment in Parkinson’s Disease

ObjectiveTo evaluate how bilateral subthalamic nucleus deep brain stimulation (STN-DBS) affects visuo-motor coordination (VMC) in patients with Parkinson’s disease (PD).BackgroundVMC involves multi-sensory integration, motor planning, executive function and attention. VMC deficits are well-described in PD. STN-DBS conveys marked motor benefit in PD, but pyscho-cognitive complications are recognized and the effect on VMC is not known.MethodsThirteen PD patients with bilateral STN-DBS underwent neurological, cognitive, and mood assessment before VMC testing with optimal DBS stimulation parameters (‘on-stimulation’) and then, on the same day without any medication changes, after DBS silencing and establishing motor function deterioration (‘off-stimulation’). Twelve age-matched healthy controls performed 2 successive VMC testing sessions, with a break of similar duration to that of the PD group. The computer cursor was controlled with a dome-shaped ‘mouse’ hidden from view that minimized tremor effects. Movement duration, hand velocity, tracking continuity, directional control variables, and feedback utilization variables were measured. MANOVA was performed on (1) clinically measured motor function, (2) VMC performance and (3) mood and attention, looking for main and interaction effects of: (1) group (controls/PD), (2) test-order (controls: first/second, PD: on-stimulation/off-stimulation), (3) path (sine/square/circle) and (4) hand (dominant/non-dominant).ResultsUnified PD Rating Scale (UPDRS) Part III worsened off-stimulation versus on-stimulation (mean: 42.3 versus 21.6, p = 0.02), as did finger tapping (p = 0.02), posture-gait (p = 0.01), upper limb function (p<0.001) and backwards digit span (p = 0.02). Stimulation state did not affect mood. PD patients performed worse in non-velocity related VMC variables than controls (F(5,18) = 8.5, p<0.001). In the control group there were significant main effects of hand (dominant/non-dominant), path (sine/square/circle) and test-order (Test_1/Test_2). In the PD group, hand and path effects, but no test-order (on-stimulation/off-stimulation), were found.Conclusions‘Low-level’ clinically-measured motor function responds to STN-DBS but ‘high-level’ motor and cognitive functions relating to VMC may be unresponsive to STN-DBS.

Evolution of visual field loss over ten years in individuals taking vigabatrin

Vigabatrin-associated visual field loss (VAVFL) occurs in around 45% of exposed people. It is generally accepted that, once established, VAVFL is stable and does not progress with continued VGB use. Most studies have, however, only followed people for short periods. We assessed the evolution of VAVFL over a ten-year period of continued VGB use. From a group of 201 vigabatrin-exposed individuals with epilepsy, fourteen individuals were identified who were currently taking vigabatrin. All individuals had at least ten years exposure to vigabatrin. Individuals underwent several visual field examinations using Goldmann perimetry between Test 1 (first recorded examination) and Test 2 (most recent examination). All visual field results were analysed and quantified retrospectively by one investigator. 174 visual fields from the fourteen participants were available. The average follow-up period was 128 months. The prevalence of VAVFL increased from 64% at Test 1 to 93% at Test 2. The visual field size was significantly smaller at Test 2 compared to Test 1. All subjects showed a trend for decreasing visual field size with increasing cumulative vigabatrin exposure, when all fields for an individual were taken into account. There was a high degree of variability in visual field size between successive test sessions. VAVFL progresses with continued vigabatrin exposure over a ten-year period. Progression may be slow and difficult to detect because of the high degree of variability in visual field size between successive test sessions. New techniques are needed to monitor the effects of vigabatrin retinotoxicity in people who continue vigabatrin therapy.

Energy System Contribution to Olympic Distances in Flat Water Kayaking (500 and 1,000 m) in Highly Trained Subjects

Olympic flat water kayaking races take place over a distance of 500 and 1,000 m. This study was designed to determine the aerobic and anaerobic contributions to 500- and 1,000-m races during flat water paddling in open water, using the accumulated oxygen deficit (AOD) method. Seven internationally ranked athletes, specialized in 500-m races and familiar with 1,000-m races, participated in this study (age: 21.86 ± 1.68 years, body mass: 78.54 ± 3.41 kg, height: 1.84 ± 0.03 m, body fat%: 10.14 ± 0.69%). All the participants performed 3 track-kayaking sessions. During the first session, the maximal oxygen uptake and maximal aerobic speed were determined using a portable gas analyzer and a global positioning system. During the successive testing sessions, paddlers performed in a randomized counterbalanced order a 500- and a 1,000-m race under field conditions (open water track kayaking). The 500-m AOD was significantly higher than the 1,000-m AOD (18.16 ± 4.88 vs. 9.34 ± 1.38 ml·kg(-1), p < 0.05). The aerobic contribution resulted in being higher during the 1,000 m compared with that in the 500-m condition (86.61 ± 1.86% vs. 78.30 ± 1.85%, respectively, p < 0.05). The results of this study showed that the 500- and 1,000-m races are 2 physiologically different kayaking events with a higher aerobic contribution in the 1,000 m. The training prescription for elite athletes should emphasize aerobic high-intensity training for the 1,000 m and anaerobic short-term training for the 500-m race.

Cognitive event-related potentials as indicators of donepezil treatment effects in mild Alzheimer's disease

Background: In previous research we identified ERP and behavioural features associated with memory that produced good discrimination between mild AD and controls. Two prominent markers include a difference wave around 600ms, and memory performance (d' measures). In the current study, we explore whether these markers of brain and cognitive function are sensitive to treatment effects of donepezil. Methods: We examined a range of ERP components and behavioral data based on a crossmodal episodic memory task designed to elicit activity in the hippocampus. The task entails an old/new decision to simple visual images coupled with auditory words. For example, the image of a train is presented with the word “tunnel.” Some pairs are presented a second or third time, at varying intervals. Dense array (128 channel) EEG is acquired continuously during testing. Patients newly diagnosed with probable AD participated in four successive test sessions: pre-treatment Session 1, and post-treatment Session 2 (1 week), Session 3 (4 weeks) and Session 4 (12 weeks). All patients received donepezil. We report here the findings for 8 patients who have completed all test sessions in the ongoing study. Results: We observed significant effects between pre-treatment and post-treatment conditions, as measured by both behaviorial (d') and ERP variables. T-tests with the d' measure show significant differences between Session 1 and 3 (t = -2.45, p < 0.045), and between Session 3 and 4 (t = -2.50, p < .042). These differences indicate an improvement in memory task performance is associated with treatment. We also observed memory-related ERP effects that vary according to treatment condition. In the time interval 520-580ms post-stimulus, in healthy controls we observe a left frontal negativity that is coupled with a right parietal positivity. Pre-treatment, this effect is greatly attenuated in AD patients. However, by Session 4 (12 weeks), we observe apparent recovery of this functional ERP pattern (Memory x Session, F = 3.45, p < 0.009; Session 1 vs Session 4, F = 12.88, p < .013). Conclusions: The improvement in memory performance, together with the recovery of brain function, indicate that cognitive ERP methods are sensitive to treatment affects of donepezil in AD.

Death, Dropout, and Longitudinal Measurements of Cognitive Change in Old Age

During a 20-year longitudinal study of cognitive change in old age 2,342 of 5,842 participants died and 3,204 dropped out. To study cognitive change as death approaches, we grouped participants by survival, death, dropout, or dropout followed by death. Linear mixed-effects pattern-mixture models compared rates of cognitive change before death and dropout from four quadrennial administrations of tests of fluid intelligence, vocabulary, and verbal learning. After we took into account the significant effects of age, gender, demographics, and recruitment cohorts, we found that approach to death and dropout caused strikingly similar reductions in mean test scores and amounts of practice gains between successive quadrennial testing sessions. Participants who neither dropped out nor died showed significant but slight cognitive declines. These analyses illustrate how neglect of dropout miscalculates effects of death, of worsening health, and of all other factors affecting rates of cognitive change.

Sudden Declines in Intelligence in Old Age Predict Death and Dropout From Longitudinal Studies

It is well known that approaching death accelerates cognitive decline. The converse issue, that is, the question of whether rapid declines in cognitive ability are risk factors for imminent death, has not been investigated. Every 4 years between 1983 and 2003, we gave 1,414 healthy community residents who were aged between 49 and 93 years the Heim AH4-1 test of fluid intelligence. A modified Andersen-Gill model evaluated AH4-1 scores at entry to the study and changes in scores between successive quadrennial test sessions as risk factors for death and dropout. Deaths, dropouts, age, gender, occupational categories, and recruitment cohorts were also taken into account. Participants with lower AH4-1 scores on entry were significantly more likely to die or to drop out. At all ages and levels of baseline intelligence, the risks of deaths and dropouts further increased if test scores fell by 10%, and again increased if they fell by 20% during 4-year intervals between successive assessments.

Warm-up or stretch as preparation for sprint performance?

Warm-up and stretching are widely used as techniques in preparation for intense physical activity, yet there is little information available to compare their effectiveness in relation to athletic performance. Fourteen elite Under-19 year old rugby league footballers undertook each of four preparation protocols (no preparation, stretching only, warm-up only, warm-up and stretching) in four successive testing sessions. Protocols were randomly allocated to players in a counterbalanced design so that each type of preparation occurred equally on each day of testing. During each session, athletes performed three solo sprint trials at maximum speed. Sprints were of 40-m distance and were electronically timed with wind speed and direction recorded. Preparation involving warm-up resulted in significantly faster sprint times compared to preparations having no warm-up, with a diminishing effect over the three trials. On the first trial, warm-up resulted in a mean advantage of 0.97 m over 40 m. Stretching resulted in a mean disadvantage of 0.18 m on the first trial, and no significant effect overall despite significant wind assistance. Warm-up was effective at improving immediate sprint performance, whereas an equivalent duration of lower limb stretching had no effect.

The influence of the perceptual or fear learning on rats’ prepulse inhibition induced by changes in the correlation between two spatially separated noise sounds

Perceptually grouping a sound source with its reflections and separating them from irrelevant background noise sounds need computation of sound correlations and are critical for identifying and localizing the sound source in a complex acoustic environment. Using the prepulse inhibition of the acoustic startle reflex (ASR) as a measure, the present study investigated whether rats are able to detect correlation changes between sounds from different spatial locations. The results show that the rat’s ASR amplitude was suppressed when the startle-eliciting stimulus was preceded by either an uncorrelated noise fragment or an anti-phase noise fragment that was embedded in two identical (correlated) but spatially separated noises. Suppression of the ASR amplitude increased as the duration of the noise fragment increased from 5 ms to 40 ms. The suppressive effect was also progressively enhanced after rats underwent successive testing sessions. Moreover, an enhanced suppression of the ASR amplitude was observed after rats were exposed to footshock that was precisely paired with a 100-ms correlation-change fragment. The results indicate that rats are able to detect the correlation change between sounds from two separated spatial locations, and the detection can be facilitated by both perceptual learning and emotional learning.

Understanding Terminal Decline in Cognition and Risk of Death

There is new empirical evidence that the effects of impending death on cognition have been miscalculated because of neglect of the incidence of dropout and of practice gains during longitudinal studies. When these are taken into consideration, amounts and rates of cognitive declines preceding death and dropout are seen to be almost identical, and participants aged 49 to 93 years who neither dropout nor die show little or no decline during a 20-year longitudinal study. Practice effects are theoretically informative. Positive gains are greater for young and more intelligent participants and at all levels of intelligence and durations of practice; declines in scores of 10% or more between successive quadrennial test sessions are risk factors for mortality. Higher baseline intelligence test scores are also associated with reduced risk of mortality, even when demographics and socioeconomic advantage have been taken into consideration.

No spatial working memory deficit in β-amyloid-exposed rats: A longitudinal study

Two experiments are described assessing whether long-term intraventricular or intrahippocampal administration of β-amyloid protein 1–40 (βA 1–40) affects spatial working memory in rats monitored in a longitudinal study using the open-field water maze. A delayed matching-to-position procedure (DMTP) was employed in which platform locations were semirandomly altered between days but were kept constant over the four trials on each day. Intertrial intervals (ITIs) were either 30 s or 1 h between Trials 1 and 2 (all other intervals=30 s), with Trial 2 performance being an index for spatial working memory. Animals were trained before and tested repeatedly at various intervals after application of various compounds (see below) in five successive test sessions (TSs). In Experiment 1, βA 1–40 was applied after a challenge with long-term oral exposure to aluminium (Al; as 0.1% sulfate in drinking water). This in itself did not affect spatial working memory at any delay, despite of the more than 6 months of intake. βA 1–40 administered alone via intracerebroventricular (icv) minipumps (20 μg in 250 μl) led to a small increase in latencies to find the platform, which recovered to control levels 3 months after minipumps were exhausted. Application of βA 1–40 in Al-exposed animals led to a subtle and progressive decline in working memory. This deterioration was reversed by the nootropic compound nefiracetam, which had no effect on the Al only group. In Experiment 2, well-trained rats were bilaterally implanted with intrahippocampal minipumps containing βA 1–40 or reverse sequence βA 40–1. This did not impair spatial working memory in the DMTP task, measured either directly after minipumps were exhausted, or 2 weeks later. When intraperitoneally (ip) injected with a low concentration of the muscarinic antagonist scopolamine (0.2 mg/kg), a dose that was not effective alone, animals in the βA 1–40 group were amnesic. These data suggest that intrahippocampal βA 1–40 administration alters cholinergic transmission, but these alterations may be mild and thus do not lead to obvious working memory deficits in a DMTP task in well-trained animals.

Predisposition to self-administer amphetamine: the contribution of response to novelty and prior exposure to the drug.

The present experiment examined the contribution of locomotor response to novelty and prior exposure to amphetamine to rats' predisposition to self-administer a low dose of the drug. Rats were screened for their locomotor response to a novel environment and divided into high (HR) or low (LR) responders based on whether their locomotor scores were above or below the median activity level of the subject sample. Animals were then pre-exposed to nine daily injections of either saline (1 ml/kg, i.p.) or amphetamine (1.5 mg/kg, i.p.). Starting 1 week after pre-exposure, animals in the four different groups (HR pre-exposed to saline or amphetamine; LR pre-exposed to saline or amphetamine) were given the opportunity, in each of ten daily sessions, to lever press for a low dose of amphetamine (10 micrograms/kg per infusion) in a two lever (active versus inactive) continuous reinforcement operant task. Initial lever press performance revealed no difference in active versus inactive lever pressing between amphetamine and saline pre-exposed animals. However, in agreement with previous reports, with successive test sessions amphetamine pre-exposed rats maintained higher levels of active versus inactive lever pressing for drug while saline pre-exposed rats showed a progressive decrease in the pressing of either lever. Interestingly, this enhanced active lever pressing was observed in HR but not LR rats pre-exposed to amphetamine. In addition, HR saline pre-exposed animals showed initial active versus inactive lever pressing equivalent to that of HR amphetamine pretreated rats but this enhanced responding for drug diminished over days and by the last day of self-administration was indistinguishable from that of LR animals having been pre-exposed either to amphetamine or saline. These findings confirm that prior exposure to amphetamine promotes the subsequent self-administration of the drug and suggest that response to novelty may be a predictor more closely linked to an animal's propensity to become sensitized to the facilitatory effects of the drug rather than to an animal's current sensitization state and predisposition to self-administer the drug.

Orcadian Rhythm in the Torque Developed by Elbow Flexors During Isometric Contraction Effect of Sampling Schedules

Time-dependent changes in elbow flexion torque have been documented according to two different sampling schedules. Seven physical education students took part in the first series of experiments, and 7 other similar subjects in the second. In both sets of experiments, the subjects performed isometric contractions: maximal and submaximal at 90° in the first experiments and maximal at different angular positions in the second. After a 30-minute rest period, the torque developed was measured at 00:00, 06:00, 09:00, 12:00, 15:00, 18:00, and 21:00h on the day of the experiment. These subjects remained in the laboratory for 24h. In the second series of experiments, the torque developed was measured at 01:00, 05:00, 09:00, 13:00, 17:00, and 21:00h over the subsequent 6 days with only one test session per day. In this case, there was an interval of 20h between two successive test sessions. In the first experiment, a significant time-of-day effect was observed for the torque of the elbow flexors under isometric conditions with an acrophase at 17:58h. The 24h normalized mean score was 92.85% with an amplitude of 7.63% of the daily mean. In the second series of experiments, there was evidence of a circadian rhythm in the torque developed by the elbow flexors at every angle position, especially at 90°, the angle investigated in the first set of experiments. The peak torque was calculated to have occurred at 17:55h. The amplitude of the rhythm was equal to 6.99% of the daily mean. There were no statistically significant differences in the characteristics of the circadian rhythm observed between the two experimental designs. We concluded that an experiment extending over several days could be employed to evaluate circadian rhythms in muscular activity reliably. (Chronobiology International, 14(3), 287–294, 1997)

Nine parallel versions of four memory tests: An assessment of form equivalence and the effects of practice on performance

AbstractFour memory tests, each containing nine parallel forms, were developed and assessed for their suitability for use in psychopharmacological research. The tests measured verbal memory, face‐name‐occupation associate learning, spatial location memory and memory for visual designs. Twenty‐seven healthy subjects completed a different form of each test on each of nine testing occasions. Test form administration order was rotated across subjects to permit the independent assessment of practice effects and test form equivalence. Performance on four of the test forms differed significantly from performance on other forms of the same test. Data from the remaining forms contained no significant test form differences and these were assumed to be equivalent. ANOVA indicated practicerelated changes in six of the seven measures examined. Four or five successive test sessions were required before performance stabilized. Initial ‘dips’ in performance observed in the verbal memory tests were attributed to proactive interference, whilst further performance improvements in spatial location performance that occurred in the last three days of the study may have been caused by the development of mnemonic strategies. Thus, patterns of change with practice varied across the four tests. The results underline the importance of documenting practice effects in relation to repeated memory assessment.

Effects of chronic marijuana use on human cognition

Impairments of human cognition and learning following chronic marijuana use are of serious concern, but have not been clearly demonstrated. To determine whether such impairments occurred, this study compared performance of adult marijuana users and non-users (N = 144 and N = 72, respectively) matched on intellectual functioning before the onset of drug use, i.e., on scores from standardized tests administered during the fourth grade of grammar school (Iowa Tests of Basic Skills). Subjects were given the twelfth grade versions of these tests (Iowa Tests of Educational Development) and other, computerized cognitive tests in successive test sessions. "Heavy" marijuana use (defined by use seven or more times weekly) was associated with deficits in mathematical skills and verbal expression in the Iowa Tests of Educational Development and selective impairments in memory retrieval processes in Buschke's Test. The retrieval impairments were restricted to words that were easy to visualize. Impairments depended on the frequency of chronic marijuana use, i.e., "light" and "intermediate" marijuana use (defined by use one to four and five to six times weekly, respectively) were not associated with deficits. Intermediate use was associated with superior performance in one condition ("fuzzy" concepts) of a Concept Formation test.