A longitudinal study of the performance of the elderly and young on the Tower of Hanoi puzzle and Rey recall.

Normal performance on the Tower of Hanoi puzzle by amnesic patients has been taken as support for viewing this problem solving task as having a nondeclarative memory component. Individuals in each decade of life between the 20s and 80s were asked to solve this puzzle four times in four sessions with intersession intervals from 1 to 7 days (Davis & Keller, 1998). Participants in their 70s and 80s were significantly impaired compared to participants in their 20s and 30s. The elderly were also significantly impaired on five immediate trials of a 15 words verbal recall test. Participants were readministered these tests an average of 6.6 years later for the elderly (n = 12) and 7.7 years later for the young (n = 11). For the Tower of Hanoi, the performance of the elderly, but not the young individuals, was significantly poorer than their original performance. For the verbal recall test, no significant change over time was detected for the young or elderly participants. These findings support the view that some nondeclarative and/or problem solving tasks demonstrate as great or greater decline with age than some declarative tasks.

A ten-year longitudinal examination of repetition priming, incidental recall, free recall, and recognition in young and elderly.

The effects of age and time on nondeclarative and declarative memory in young and elderly were examined in a 10-year longitudinal study using tests of word-stem priming, incidental recall, free recall, and recognition. The elderly were significantly impaired on all tests, but no reliable longitudinal decrement by the elderly was detected for priming, incidental recall,or recognition. The elderly demonstrated a significant longitudinal decline in declarative memory as assessed by a test of free recall. While nondeclarative memory declines with age, the longitudinal findings are consistent with the view that declarative memory is more susceptible to the effects of aging.

Validity of lower extremity strength and power utilizing a new closed chain dynamometer.

PURPOSE: The purpose of this study was to compare selected variables measured on a traditional isokinetic dynamometer (Cybex II) with a new lower extremity, closed chain dynamometer (Omnikinetic, OmK). METHODS: Twelve subjects (6 male, 6 female, age = 28+/-5 yr, mean +/- SD) performed Cybex II knee flexion and extension at 1.05, 3.14, and 5.23 rad x s(-1). A maximal effort of 10 repetitions of lower extremity concentric extension and eccentric flexion at 36% of subject's 1-RM was performed on the OmK. Crank power and joint (ankle, knee, and hip) kinetics were recorded as a mean of 10 repetitions. RESULTS: t-Tests revealed right versus left leg differences (P < 0.05) for Cybex II peak torque flexion at 5.23 rad x s(-1), and OmK knee and hip peak power and hip root mean square power (RMS) power. Cybex peak knee torques were related (Pearson r values 0.78-0.92, P < 0.01) to OmK peak knee torques. Cybex average power was related to OmK knee power (Pearson r values 0.71-0.96, P < 0.01) and OmK crank power (r = 0.62-0.94, P < .01). Correlations tended to be stronger comparing the OmK with the fastest (5.23 rad x s(-1)) Cybex II speed. CONCLUSIONS: These results suggest that the OmK knee and crank kinetic data are comparable to Cybex It isokinetic dynamometry. The ability to evaluate lower extremity joint exercise at a subject's maximal movement speed, in addition to the use of a closed-chain, multi-joint motion, may allow for the OmK to provide a more global evaluation of lower extremity kinetics during seated concentric-extension, eccentric-flexion exercise.

A new bilateral closed chain assessment technique: methods and error analysis.

PURPOSE: The purpose of this paper is to present the Omnikinetic methodology for clinical evaluation of lower extremity function, to characterize its sensitivity to errors, and to present typical data for an assessment protocol. METHODS: A 5-bar, 2-degree of freedom linkage was used to model the geometry of the crank, pedal, and lower extremity. Two-degree force transducers at the pedal were used to calculate center of pressure and force applied at the foot. A Newton-Euler inverse dynamic model was used to calculate net joint torques and powers bilaterally of the ankle, knee, and hip. Ten subjects performed a high velocity evaluation protocol which served as the control. Error sensitivity was determined by adding instrumental error, hip translation, and segmental length errors to the collected data and comparing the outcome to the control. RESULTS: All variables associated with instrumental error had mean errors under 4%. Mean errors associated with violations of the fixed hip assumption were under 15% for all variables. Mean errors associated with anthropometric measures were divided into two types: relative error (overall length unchanged, ratios of segments changed) and absolute (overall length changed, ratios of segment lengths unchanged). Relative anthropometric mean errors were under 5%. Absolute anthropometric mean errors were under 12%. CONCLUSION: The Omnikinetic is a new tool for bilateral lower extremity evaluation that enables the whole lower extremity to be evaluated at the joint level. Instrumental accuracy was excellent. The instrument was most sensitive to violations of the fixed hip position assumption over the last 20 degrees of knee extension.

A comparison of computerized and standard versions of the Wisconsin Card Sorting Test.

The manual version of the Wisconsin Card Sorting Test (WCST) is the most frequently used neuropsychological instrument for differentiating normal from populations with frontal-lobe impairments. A number of computerized versions have become available, and their ability to accurately detect frontal-lobe dysfunction is based on the assumption of equivalence with the standard manual version. Accordingly, comparisons of the distribution properties of central tendency, variability, and shape between the manual version with four computerized versions of the WCST were performed (n = 22 per condition). None of the computerized versions were found to be equivalent to the manual version on all assessment measures. Given the discrepancies between the manual and computerized versions, it is concluded that the norms provided for the standard manual presentation method should not be used for the computerized versions, and for continued use of the computerized versions, new norms for computer versions need to be established. Thus, clinicians and experimenters must use caution when basing conclusions on scores from computer versions of the WCST.

The effect of age on the learning of a nondeclarative category classification task.

A category classification task was administered to participants in their twenties through their eighties. Participants studied a set of high distortions of a prototype dot pattern and were then asked to choose whether or not a new set of dot patterns (random patterns, high distortions, low distortions, and the prototype) belonged to the same category of dot patterns as studied. Participants were also administered a recognition test after studying a second set of dot patterns. There were no significant differences for age groups on the pattern recognition test. In 2 of the 3 analyses of the category classification task, there were no significant age effects. However, there was a small age effect in one analysis with the young making more accurate classifications on two aspects of the task. The results are consistent with the view that small age-related effects may exist for some tests of nondeclarative memory.

Detecting simulated memory impairment with the Rey Auditory Verbal Learning Test: implications of base rates and study generalizability.

The accuracy of the Rey Auditory Verbal Learning Test (RAVLT) for detecting simulated neuropsychological impairment was investigated using discriminant function analyses and cross-validation procedures. In Study 1, a discriminant function analysis, using six RAVLT variables, correctly classified 80% of 50 simulating and 50 non-simulating participants. Base rates were changed and this discriminant function was tested in Study 2 with a 33% base rate of simulation. The discriminant function correctly classified 75% of 20 simulators and 90% of 40 non-simulators, yielding an overall classification rate of 85%. To determine the generalizability of this discriminant function to a clinical sample, Study 3 compared the RAVLT performance of 20 simulating participants to that of 40 motor vehicle accident (MVA) patients. The discriminant function from Study 1 incorrectly classified 60% of the MVA patients and yielded an overall correct classification rate of 48%. The limitations associated with generalizing from analog research and the implications of varying base rates on classification accuracy are discussed.

The detection of simulated malingering using a computerized category classification test.

A category classification test was used to differentiate between normal student control participants, students instructed to malinger a memory deficit, and amnesic patients. Controls (N = 44) and amnesic patients (N = 10) were instructed to do their best, while simulators of malingering (N = 43) were instructed to fake a memory deficit for credit and possible financial compensation. Participants studied a list of high distortions of a prototype dot pattern and were then asked to choose whether or not a new set of dot patterns (random patterns, high distortions, low distortions, and the prototype) belonged to the same category of dot patterns as studied. Malingerers performed significantly worse than normal controls and amnesic patients. A discriminant function analysis showed that the classification test can be used to correctly classify participants as simulated malingerers, controls, or amnesic patients significantly higher than chance. These results indicate that a category classification test can be used in the detection of simulated malingering and that some tests of implicit memory provide a potential supplement to standard forced choice tests in the detection of malingering.

The detection of simulated malingering using a computerized priming test.

A word completion priming test was used to differentiate between normal student control subjects and students instructed to malinger. Controls (n = 60) were instructed to do their best, while malingering subjects (n = 60) were instructed to fake a memory deficit for credit and possible financial compensation. Subjects initially rated and completed stems for words that had at least 10 possible completions. Thirty minutes later, subjects rated and completed stems for words that were either uniquely defined by the stem or could only be completed with a variation of the word. Simulated malingerers and controls differed significantly on response latencies (time to produce rated words-time to produce baseline words, 10 second time limit) and priming scores. Discriminant function analyses showed that as high as 92% of the controls could be correctly identified, and 73% of the malingerers could be correctly identified. These results indicate that priming tests can be used in the detection of malingering.

The effect of trial size and variability on statistical power.

A computer model was developed, validated, and used in conjunction with Monte Carlo procedures to study the effects of sample size (subjects and trials), mean differences, and subject variability on statistical power. Also examined were the differences between single subject (SS) and group results. Mean differences were varied from 1/4 to 4 times the distribution SD resulting in improved power values. Mean group F results ranged from 63.6% to 100% while SS results were poorer, especially for the smaller mean differences (16.8%-100%). Subject variability was examined for a Simple model and two Complex (MOD1 and MOD4) models. MOD1 produced group results similar to the corresponding Simple model with an overall mean of 78.2% and a Complex/Simple (C/S) ratio of 0.99. The more variable model (MOD4) produced fewer significant results (52.9%) and a lesser C/S ratio (0.82). The SS results were more dramatic. The percentages of significant values were less (38.1% and 33.9%) and the C/S ratios favored the Complex models (1.48 and 3.17). Both sample size and trial size had a major impact on the results. In summary, these results provide additional insight into the interactive effects and importance of the factors investigated, especially in the area of SS experiments.

The effect of trial size on statistical power.

Many research studies produce results that falsely support a null hypothesis due to a lack of statistical power. The purpose of this research was to demonstrate selected relationships between single subject (SS) and group analyses and the importance of data reliability (trial size) on results. A computer model was developed and used in conjunction with Monte Carlo procedures to study the effects of sample size (subjects and trials), within- and between-subject variability, and subject performance strategies on selected statistical evaluation procedures. The inherent advantages of the approach are control and replication. Selected results are presented in this paper. Group analyses on subjects using similar performance strategies identified 10, 5, and 3 trials for sample sizes of 5, 10, and 20, respectively, as necessary to achieve statistical power values greater than 90% for effect sizes equal to one standard deviation of the condition distribution. SS analyses produced results exhibiting considerably less power than the group results for corresponding trial sizes, indicating how much more difficult it is to detect significant differences using a SS design. These results should be of concern to all investigators especially when interpreting nonsignificant findings.

Early post-natal administration of 5,7-dihydroxytryptamine destroys 5-HT neurons but does not affect spatial memory.

The neurotransmitter serotonin (5-hydroxytryptamine, 5-HT) may play an important role in learning and memory. It has also been suggested that 5-HT abnormalities may mediate some aspects of the cognitive disorders associated with Korsakoff syndrome and Alzheimer's Disease. The effect of intracisternally applied 5-HT neurotoxin, 5,7-dihydroxytryptamine (5,7-DHT) on learning and memory in rodents was evaluated. Three-day-old rat pups were treated with pargyline (40 mg/kg, i.p.) followed by 5,7-DHT (50 micrograms/pup) and returned to the dam for a month. At 75 days of age, rats were tested on a learning set problem in the Morris water maze for 5 days followed by 30 days of testing in a 12-arm radial maze with 8 of the 12 arms baited. In the Morris water maze, the latency to locate the hidden platform did not differ significantly for 5,7-DHT treated and control rats (F less than 1.0). Similarly, 5,7-DHT treated rats performed comparably to controls on the 12-arm radial maze (F less than 1.0). At 106 days of age the assay of tryptophan hydroxylase activity in the dorsal raphe nuclei and hippocampus showed marked reduction (86%, 78%, respectively) in 5,7-DHT treated animals compared to vehicle injected controls. Immunocytochemical analysis was consistent with the biochemical results. In 5,7-DHT treated animals there was severe loss of neurons that bind 5-HT antibody in the dorsal and medial raphe nuclei.(ABSTRACT TRUNCATED AT 250 WORDS)

Loss of hippocampal CA1 pyramidal neurons correlates with memory impairment in rats with ischemic or neurotoxin lesions.

Rats were trained for 20 days in a modified T maze to perform an invariant, tactile discrimination and a variable, delayed spatial discrimination, and then were exposed either to 30 min of transient forebrain ischemia or to low- or high-dose ibotenic acid to damage the dorsal hippocampus bilaterally. Only rats exposed to ischemia or high-dose ibotenic acid demonstrated impaired performance during 30 postoperative test days on both aspects of the task (p less than .05). Volume of hippocampal damage did not predict performance. However, the extent of CA1 pyramidal neuron loss correlated significantly with performance on the delayed spatial discrimination (p less than .01). Damage to the dentate gyrus and CA2-3 did not correlate with performance. These results support the view that the hippocampus, in particular the CA1 region, is crucial for certain types of memory performance.

Dynamic performance assessment of selected sport shoes on impact forces.

Few investigators have evaluated the performance characteristics of non-running sport shoes. The purpose of this study was to assess the dynamic performance characteristics of four different shoe models during landings. Five male subjects performed 25 voluntary hanging drop landings (60 cm) onto a force platform (1000 Hz) for each of four shoe conditions (C1 and C2 = basketball shoe, C3 = running shoe, C4 = volleyball shoe). Ground reaction force data were evaluated for maximum forefoot (F1) and rearfoot (F2) impact forces as well as the respective times of occurrence of these events (T1, T2). Results of the group data analysis indicated a preferential performance rank order of C1, C3, C4, C2 although significant interaction effects were observed, indicating a need for single-subject analyses. Three techniques were incorporated to assess individual subject condition differences, all of which elicited unique rank orders for the shoes although each identified C1 as the "best" shoe condition. The results of the study support the necessity for within-subject analyses conducted with an adequate number of trials when attempting to detect subtle performance differences that may exist between various sport shoes. Whether the observed statistically significant differences are biomechanically meaningful remains an important unanswered question.

Lexical priming deficits as a function of age.

The effects of age on implicit memory were assessed in elderly young adults using 2 priming procedures. Subjects also completed the WAIS-R, 3 tests to assess frontal lobe function, and 2 recall and 2 recognition tests of explicit memory. In Experiment 1, subjects were exposed to the low-frequency member of a homophone pair in a test purported to assess general knowledge. Subsequently, subjects completed a spelling test that contained the previously presented homophones to assess priming. Young subjects demonstrated priming (p less than .01). Elderly subjects demonstrated a high baseline that may have obscured priming. In Experiment 2, subjects from each decade of life from the 20s through the 80s were given a word-stem completion test of priming. All age conditions demonstrated an effect of priming (p less than .01). However, subjects in their 70s and 80s demonstrated lower priming scores (p less than .05). Elderly subjects were also impaired on immediate-and delayed-recall tests. These results suggest an age-related decline in both implicit and explicit memory.

Preoperative training modifies radial maze performance in rats with ischemic hippocampal injury.

Rats exposed to 30 minutes of four-vessel occlusion reliably develop severe bilateral CA1 hippocampal injury; under certain conditions of radial maze training, such rats perform the reference memory component as well as controls yet perform the working memory component worse than controls. Reference memory is thought to depend on invariable and working memory on variable spatial information. We assessed the effect of training before ischemia. In Experiment 1, rats trained for 36 trials on 12-arm radial mazes before ischemia demonstrated a persistent impairment on the working memory task but eventually performed the reference memory task comparable to controls. Ischemic rats made more working memory errors as the number of choices increased. This pattern of working memory errors was similar to that in controls except, as expected, ischemic rats made many more errors. In Experiment 2, training for 80 trials before ischemia in rats decreased the severity of both the working and the reference memory impairment. Ischemia did not affect motor behavior in either experiment. These results characterize the working memory deficit in ischemic rats and demonstrate the importance of experimental factors, particularly in the design of treatment strategies to reduce functional impairments caused by ischemia.

Allocentric spatial and tactile memory impairments in rats with dorsal caudate lesions are affected by preoperative behavioral training.

Rats with caudate lesions and pretrained for 36 trials demonstrated impaired performance on the "reference memory" or invariant aspect of a 12-arm radial maze and normal performance on the "working memory" or variable aspect of the maze. Rats with caudate lesions and no pretraining were also impaired on an invariant tactile discrimination in a T maze, but they were not impaired on the variable goal-arm choice of the T maze. More extensive preoperative training ameliorated behavioral deficits of rats with caudate lesions in the T maze and radial arm maze. Results showed that behavioral impairment after damage to the caudate is not restricted to egocentric tasks as previously suggested, but the caudate seems to be involved in the initial acquisition of information that is invariant over many trials.