Untrained Condition Research Articles

Age-related impairments and influence of visual feedback when learning to stand with unexpected sensorimotor delays.

While standing upright, the brain must accurately accommodate for delays between sensory feedback and self-generated motor commands. Natural aging may limit adaptation to sensorimotor delays due to age-related decline in sensory acuity, neuromuscular capacity and cognitive function. This study examined balance learning in young and older adults as they stood with robot-induced sensorimotor delays. A cohort of community dwelling young (mean = 23.6 years, N = 20) and older adults (mean = 70.1 years, N = 20) participated in this balance learning study. Participants stood on a robotic balance simulator which was used to artificially impose a 250 ms delay into their control of standing. Young and older adults practiced to balance with the imposed delay either with or without visual feedback (i.e., eyes open or closed), resulting in four training groups. We assessed their balance behavior and performance (i.e., variability in postural sway and ability to maintain upright posture) before, during and after training. We further evaluated whether training benefits gained in one visual condition transferred to the untrained condition. All participants, regardless of age or visual training condition, improved their balance performance through training to stand with the imposed delay. Compared to young adults, however, older adults had larger postural oscillations at all stages of the experiments, exhibited less relative learning to balance with the delay and had slower rates of balance improvement. Visual feedback was not required to learn to stand with the imposed delay, but it had a modest effect on the amount of time participants could remain upright. For all groups, balance improvements gained from training in one visual condition transferred to the untrained visual condition. Our study reveals that while advanced age partially impairs balance learning, the older nervous system maintains the ability to recalibrate motor control to stand with initially destabilizing sensorimotor delays under differing visual feedback conditions.

85 Evaluating the Improvement on the Naturalistic Action Task After the Virtual Kitchen Intervention: A Case Study

Objective:The goal-control model of the functional impairment in dementia posits two different underlying mechanisms: decay of task goals (reduced task accomplishment) and poor control over goal execution (high error rates). Here we present a case series in which we explore the effects of a performance-based, functional intervention on two participants. Outcomes were evaluated using the goal-control framework.Participants and Methods:Two participants with dementia (CS: age 70, 14 years of education; EM: age 93, 18 years of education) completed neuropsychological tests (scored using age, education, and IQ-adjusted norms) and baseline testing with the Naturalistic Action Task (NAT; a validated performance-based task of everyday function including a Breakfast and Lunch task). The Virtual Kitchen (VK) was used to train, through repeated performance, either the Breakfast (CS) or Lunch (EM) tasks for 30 minutes (or 10 total repetitions) per day over 5 days. After VK training, participants performed the NAT Breakfast and Lunch tasks again to evaluate improvement on the trained and untrained tasks. Baseline and post-training NATs were scored for task accomplishment and errors by two coders observing video recordings. Z scores were derived by calculating accomplishment and error change scores for each participant relative to the mean and standard deviations of change scores from a cohort of 36 healthy controls (mean age: 73.3, SD: 6.44; mean education: 17.42, SD: 2.17).Results:Both participants exhibited similar cognitive profiles: high estimated IQ; low MMSE (total = 19 for both CS and EM; 1st percentile); anterograde amnesia, slowed processing speed and impaired executive function; average scores on tests of attention, language, and self-reported depression. Informant report of daily functioning (FAQ) suggested that EM (FAQ=28) exhibited greater functional impairment than CS (FAQ=9). Both participants completed all VK training sessions. Z scores of the change from pre- to post-training showed significant increases in task accomplishment on the trained task (trained condition change z scores: EM = +27.69; CS =+ 6.06), but significantly less improvement or worse task accomplishment on the untrained task (untrained condition change z scores: EM = +4.06; CS = -13.69). The training did not reduce errors, as error rates increased for both participants on the trained task.Conclusions:The participants presented in this case study exhibited comparable cognitive profiles, including marked anterograde amnesia. Our results suggest that repeated training in a virtual context can improve specific aspects of functioning on real, life everyday tasks. Further, according to the goal-control framework, repeated practice reduces the decay of the task goal, as represented by greater task accomplishment, but does not improve executive control over the task execution. Important future directions are to determine if people with different cognitive profiles will demonstrate different benefits from VK training and to examine if virtual training of personally relevant, everyday tasks can promote independent living and improve quality of life.

Resting Myokine Concentrations Are Reduced With Resistance-exercise Training But Blood Flow-restricted Resistance-exercise Response Is Unchanged.

Myokines are proteins and peptides produced and secreted by skeletal muscle; some are postulated to contribute to skeletal muscle hypertrophy. PURPOSE: To evaluate systemic myokine concentrations following acute blood-flow restricted resistance-exercise (BFR-RE) after a twelve-week traditional strength-training protocol in younger and older males. METHODS: Untrained males (younger: 24.7 ± 3.9 yrs, n = 8; older: 68.3 ± 4.6 yrs, n = 7) performed full-body BFR-RE before and after 12 weeks of progressive full-body strength training. At rest, immediately after, and 3, 6, 24 and 48 hours following each BFR-RE session, venous blood was collected and analyzed in duplicate to determine concentrations of interleukin-4 (IL-4), IL-6, IL-7, irisin, Leukemia Inhibitory Factor (LIF) and nitrate/nitrite. Area under the curve was calculated and a 2-way (age × training status) repeated measures ANOVA was conducted. RESULTS: For older males, IL-4 (untrained = 6996.9 ± 9260.2 AUC vs. trained = 5681.2 ± 8133.6 AUC; p = 0.038) and IL-6 (untrained = 819.2 ± 1104.5 AUC vs. trained = 636.5 ± 952.8 AUC; p = 0.016) were higher in the untrained condition than trained but did not differ for younger males. A significant age effect was identified for irisin, as younger males had higher concentrations than older (mean difference = 9423.8 ± 12546.8 AUC; p = 0.012). However, when AUC was calculated with baseline values subtracted, participants had higher IL-7 in the untrained condition compared to trained (mean difference = 33.5 ± 56.9 AUC; p = 0.04). Other myokines showed no training differences. CONCLUSION: Younger males had higher circulating irisin, and strength training decreased IL-4 and IL-6 in older males. The disappearance of age-related changes in IL-4 and IL-6 after baseline subtraction suggests those differences were due to lower baseline concentrations following the strength training program. Thus, IL-4 and IL-6 levels did not respond differently to BFR-RE in the untrained and trained conditions. Also, the lower response of IL-7 to BFR-RE in the trained vs. the untrained condition indicates that myokine secretion is affected by an individual’s level of training. Funding: This project was supported by grants (SMC & JEA) from the University Collaborative Research Program and Faculty of Science Collaborative - University of Manitoba.

Arithmetic learning in children: An fMRI training study

Arithmetic learning is characterized by a change from procedural strategies to fact retrieval. fMRI training studies in adults have revealed that this change coincides with decreased activation in the prefrontal cortex (PFC) and that within the parietal lobe, a shift occurs from the intraparietal sulcus (IPS) to the angular gyrus (AG). It remains to be determined whether similar changes can be observed in children, particularly because children often recruit the hippocampus (HC) during arithmetic fact retrieval, an observation that has not been consistently found in adults. In order to experimentally manipulate arithmetic strategy change, 26 typically developing 9- to-10-year-olds completed a six day at-home training of complex multiplication items (e.g. 16 × 4). Before and after training, children were presented with three multiplication conditions during fMRI: (1) complex to-be-trained/trained items, (2) complex untrained items and (3) single-digit items. Behavioral data indicated that training was successful. Similar to adults, children showed greater activity in the IPS and PFC for the untrained condition post-training, indicating that the fronto-parietal network during procedural arithmetic problem solving is already in place in children of this age. We did not observe the expected training-related changes in the HC. In contrast to what has been observed in adults, greater activity in the AG was not observed for the trained items. These results show that the brain processes that accompany the learning of arithmetic facts are different in children as compared to adults.

Web-based sensitivity training for interacting with facial paralysis.

Previous research has shown that observers tend to form inaccurate and negatively biased first impressions of people with facial paralysis (FP). It has been hypothesised that this may be ameliorated by encouraging people to focus on channels of expression other than the face. This was tested in a web-based study of 466 participants. Participants in the Trained Condition received tips for perceiving expressiveness in individuals with FP, while those in the Untrained Condition received general medical information about FP. We observed no significant differences between groups for accuracy of emotion recognition, but a significant effect of the training upon perception of emotional intensity. These results show that attending to non-facial cues may improve social perception and reduce bias.

Higher Concentration Of Irisin In Younger Versus Older Adults Before And Following Blood-flow Restricted Resistance-exercise

Irisin is a myokine primarily recognized for its effect on browning adipose tissue, however emerging evidence suggests irisin also has a role in regulating skeletal muscle hypertrophy. PURPOSE: The purpose of this study was to determine if age or training status results in a differing systemic irisin concentrations following acute blood-flow restricted (BFR) resistance-exercise. METHODS: Fifteen untrained males (Younger: 24.7 ± 3.9 yrs, n = 8; Older: 68.3 ± 4.6 yrs, n = 7) performed a bout of full-body BFR resistance-exercise before and after twelve weeks of progressive full-body resistance exercise training. Blood samples were collected via venipuncture before, immediately after, and 3, 6, 24 and 48 hours post-BFR resistance-exercise. Samples were analyzed in duplicate to determine irisin concentration. RESULTS: A main effect for age (younger = 480.23 ± 34.2 pg/mL vs. older = 281.36 ± 36.57 pg/mL; p = 0.001) and interaction effect for training status x time (p = 0.02) were identified. No other main or interaction effects were noted (all p > 0.05). The concentration of irisin did not differ between any time points in the untrained condition, but differences were observed after completing twelve weeks of resistance training. In the trained condition, irisin decreased immediately post-BFR compared to baseline (Baseline = 413.13 ± 44.47 pg/mL vs. Post-BFR = 286.97 ± 47.76; p = 0.004). The concentration of irisin immediately post-BFR was also lower than 6 hours post-BFR (Post-BFR = 286.97 ± 47.76 pg/mL vs. 6-hours = 448.20 ± 47.54; p = 0.002). CONCLUSION: Older adults have a lower concentration of irisin before and after acute BFRE regardless of training status. These results suggest that the myokine irisin could contribute to differences in skeletal muscle hypertrophy response to resistance exercise between younger and older males. In the untrained condition, irisin does not respond to acute BFR, however in the trained condition irisin decreases immediately following BFR and then peaks by 6 hours of recovery. The training status of individuals alters the response of irisin to acute resistance training potentially manipulating the time course of downstream insulin-like growth factor-1 and myostatin which irisin is postulated to upregulate and downregulate, respectively.

Effects of Repeated Exposure to Synthetic and Digitized Natural Speech by Individuals With Aphasia

Purpose Technological supports provide multimodal presentation of text, which may increase understandability of written materials by people with aphasia (PWA). Extant literature reveals that digitized natural speech and synthetic computer-generated speech within these supports are comprehensible by PWA at discrete time points; however, understandability following repeated exposure is unexplored. This pilot study evaluated understanding of, and preference regarding, synthetic and digitized natural speech during and following repeated exposures by PWA. Method This multiple–case-study project included four adults with aphasia. Participants independently completed various listening tasks in a single digitized natural speech condition and one of two synthetic speech conditions across a 2-week period. Participants completed sessions to evaluate maintenance effects and generalization to novel stimuli and an untrained synthetic voice condition 1 week and 1 month following daily practice. Results Study participants demonstrated understandability evident by at- or near-ceiling performance during baseline, practice, and follow-up sessions in the digitized natural condition and one synthetic speech condition. Individuals with mild aphasia achieved relatively consistent performance during independent practice, whereas performance of individuals with moderate aphasia fluctuated in both conditions. All four participants demonstrated variable understanding during generalization and maintenance tasks at follow-up time points. Participants most frequently indicated preference for digitized natural speech over either synthetic speech condition. Conclusions Findings hold important clinical implications when considering feasibility of utilizing these speech forms as compensatory strategies for PWA. Further research is needed to more fully understand the effects of repeated exposure to synthetic speech on comprehension among PWA.

Repetition Priming in Treatment of Anomia.

Repetition priming has been suggested as a method for targeting implicit processes in anomia treatment. Prior studies have used masked priming for this purpose. This study extends that work with visible primes, a more clinically feasible approach. This study used a single-subject design across three participants with aphasia. Treatment involved repeated exposure to identity primes (trained condition) or sham primes (untrained condition) paired with pictures. Analyses assessed acquisition effects for trained items and untrained items that were seen during the training period, generalization to untrained items that had not been seen, and generalization to broader language skills, immediately and 3 months post-treatment. All participants improved in naming trained items immediately after treatment, with greater improvements for trained than for untrained items. All participants maintained some degree of improvement on trained items 3 months post-treatment, although the degree differed across participants. Inconsistent generalization occurred to unexposed items. Improvements were noted in some areas of broader language ability, although these varied. These data suggest a repetition priming treatment paradigm may increase naming accuracy for individuals with anomia and may benefit other aspects of language. Participant factors may have influenced response to treatment. Directions for future investigation are discussed.

A new format of perceptual learning based on evidence abstraction from multiple stimuli.

Perceptual learning, which improves stimulus discrimination, typically results from training with a single stimulus condition. Two major learning mechanisms, early cortical neural plasticity and response reweighting, have been proposed. Here we report a new format of perceptual learning that by design may have bypassed these mechanisms. Instead, it is more likely based on abstracted stimulus evidence from multiple stimulus conditions. Specifically, we had observers practice orientation discrimination with Gabors or symmetric dot patterns at up to 47 random or rotating location × orientation conditions. Although each condition received sparse trials (12 trials/session), the practice produced significant orientation learning. Learning also transferred to a Gabor at a single untrained condition with two- to three-times lower orientation thresholds. Moreover, practicing a single stimulus condition with matched trial frequency (12 trials/session) failed to produce significant learning. These results suggest that learning with multiple stimulus conditions may not come from early cortical plasticity or response reweighting with each particular condition. Rather, it may materialize through a new format of perceptual learning, in which orientation evidence invariant to particular orientations and locations is first abstracted from multiple stimulus conditions and then reweighted by later learning mechanisms. The coarse-to-fine transfer of orientation learning from multiple Gabors or symmetric dot patterns to a single Gabor also suggest the involvement of orientation concept learning by the learning mechanisms.

Time course of recovery from resistance exercise before and after a training program.

To analyze the short-term response to three resistance training (RT) protocols: RT protocol leading to failure (MaxRep), half-maximal repetitions protocol in untrained condition (U-HalfRep), and half-maximal repetitions protocol in trained condition (T-HalfRep). Ten males without RT experience performed 3 sets of 5 vs. 10 repetitions with their estimated 10RM load, U-HalfRep vs. MaxRep, in the bench press and squat exercises before a 10-week RT period. After the RT period, the half-maximal repetitions protocol was repeated (T-HalfRep). Mechanical performance (jump height, and velocity against the 1 m·s-1 load) and biochemical plasma profile (testosterone, cortisol, growth hormone, prolactin, IGF-1 and creatine kinase) were assessed at several time-points from 24 h pre- to 48 h postexercise. MaxRep resulted in greater reductions and slower recovery in mechanical performance compared to half-maximal repetitions protocols. Moreover, U-HalfRep resulted in greater jump performance impairment than T-HalfRep up to 48 h-post. MaxRep also showed greater acute increments in growth hormone and prolactin. U-HalfRep and MaxRep induced higher creatine kinase levels. The MaxRep resulted in greater fatigue accumulation and slower recovery, higher hormonal response and muscle damage. The same athletes suffered slower recovery and higher muscle damage before training compared to after training despite using the same relative stimulus.

Transferability and Sustainability of Motor-Cognitive Dual-Task Training in Patients with Dementia: A Randomized Controlled Trial

Background: Specific dual-task (DT) training is effective to improve DT performance in trained tasks in patients with dementia (PwD). However, it remains an open research question whether successfully trained DTs show a transfer effect to untrained DT performances. Objective: To examine transfer effects and the sustainability of a specific DT training in PwD. Methods: One hundred and five patients with mild-to-moderate dementia (Mini-Mental State Examination: 21.9 ± 2.8 points) participated in a 10-week randomized, controlled trial. The intervention group (IG) underwent a specific DT training (“walking and counting”). The control group (CG) performed unspecific low-intensity exercise. DT performance was measured under three conditions: (1) “walking and counting” (trained); (2) “walking and verbal fluency” (semi-trained), and (3) “strength and verbal fluency” (untrained). Outcomes evaluated at baseline, after training, and 3 months after the intervention period included absolute values for the motor and cognitive performance under DT conditions, and relative DT costs (DTCs) in motor, cognitive and combined motor-cognitive performance. Results: The IG significantly improved DT performances in the trained condition for absolute motor and cognitive performance and for motor, cognitive, and combined motor-cognitive DTCs compared to the CG (p ≤ 0.001–0.047; ηp² = 0.044–0.249). Significant transfer effects were found in the semi-trained condition for absolute motor and partly cognitive performance, and for motor but not for cognitive DTCs, and only partly for combined DTCs (p ≤ 0.001–0.041; ηp² = 0.049–0.150). No significant transfer effects were found in the untrained condition. Three months after training cessation, DT performance in the trained condition was still elevated for most of the outcomes (p ≤ 0.001–0.038; ηp² = 0.058–0.187). Training gains in the DT performance in the semi-trained condition were, however, not sustained, and no significant group differences were found in the DT performance in the untrained condition after the follow-up. Conclusion: This study confirmed that specific DT training is effective in improving specifically trained DT performances in PwD and demonstrated sustainability of training-induced effects for at least 3 months. Effects were partially transferable to semi-trained DTs but not to untrained DTs. With increasing distance between trained and untrained DTs, transferability of training effects decreased.

Long-Term maintenance of anomia treatment effects in primary progressive aphasia

ABSTRACTThis study examined the maintenance of anomia treatment effects in primary progressive aphasia (PPA). Following baseline testing, a phonological treatment and an orthographic treatment were administered over the course of six months. The treatment stimuli consisted of nouns that were consistently named correctly at baseline (Prophylaxis items) and/or nouns that were consistently named incorrectly at baseline (Remediation items). Naming accuracy was measured at baseline, and it was measured at 1 month, 8 months, and 15 months post-treatment. The change in naming accuracy from baseline to each post-treatment evaluation was calculated within each treatment condition, and within a matched untrained condition. The change in naming accuracy was then compared between the three conditions. The results of these analyses indicate that phonological and orthographic treatments are both effective in the Prophylaxis and Remediation of anomia in all three variants of PPA. For Prophylaxis items, some of the effects of each treatment can persist for as long as 15 months post-treatment. These long-term treatment effects were more robust in the orthographic treatment condition and for participants with the semantic variant of PPA.

The Effect of Resistance Exercise on Inflammatory and Myogenic Markers in Patients with Chronic Kidney Disease.

Background: Muscle wasting is a common complication of Chronic Kidney Disease (CKD) and is clinically important given its strong association with morbidity and mortality in many other chronic conditions. Exercise provides physiological benefits for CKD patients, however the molecular response to exercise remains to be fully determined. We investigated the inflammatory and molecular response to resistance exercise before and after training in these patients.Methods: This is a secondary analysis of a randomized trial that investigated the effect of 8 week progressive resistance training on muscle mass and strength compared to non-exercising controls. A sub-set of the cohort consented to vastus lateralis skeletal muscle biopsies (n = 10 exercise, n = 7 control) in which the inflammatory response (IL-6, IL-15, MCP-1 TNF-α), myogenic (MyoD, myogenin, myostatin), anabolic (P-Akt, P-eEf2) and catabolic events (MuRF-1, MAFbx, 14 kDa, ubiquitin conjugates) and overall levels of oxidative stress have been studied.Results: A large inflammatory response to unaccustomed exercise was seen with IL-6, MCP-1, and TNF-α all significantly elevated from baseline by 53-fold (P < 0.001), 25-fold (P < 0.001), and 4-fold (P < 0.001), respectively. This response was reduced following training with IL-6, MCP-1, and TNF-α elevated non-significantly by 2-fold (P = 0.46), 2.4-fold (P = 0.19), and 2.5-fold (P = 0.06), respectively. In the untrained condition, an acute bout of resistance exercise did not result in increased phosphorylation of Akt (P = 0.84), but this was restored following training (P = 0.01). Neither unaccustomed nor accustomed exercise resulted in a change in myogenin or MyoD mRNA expression (P = 0.88, P = 0.90, respectively). There was no evidence that resistance exercise training created a prolonged oxidative stress response within the muscle, or increased catabolism.Conclusions: Unaccustomed exercise creates a large inflammatory response within the muscle, which is no longer present following a period of training. This indicates that resistance exercise does not provoke a detrimental on-going inflammatory response within the muscle.

Limb Position Tolerant Pattern Recognition for Myoelectric Prosthesis Control with Adaptive Sparse Representations From Extreme Learning.

We present a robust sparsity-based adaptive classification method that is significantly less sensitive to signal deviations resulting from untrained conditions. We compare this approach in the offline and online contexts of untrained upper-limb positions for amputee and able-bodied subjects to demonstrate its robustness compared against other myoelectric classification methods. We report significant performance improvements () in untrained limb positions across all subject groups. The robustness of our suggested approach helps to ensure better untrained condition performance from fewer training conditions. This method of prosthesis control has the potential to deliver real-world clinical benefits to amputees: better condition-tolerant performance, reduced training burden in terms of frequency and duration, and increased adoption of myoelectric prostheses.

Correction: Bottom-up and top-down influences at untrained conditions determine perceptual learning specificity and transfer.

People can become more sensitive to small changes in what they are seeing – such as detecting a slight change in the angle of a particular line – with practice. This process is called perceptual learning, but the improvement is often specific such that it is typically lost if the line moves to a new place, or a different line angle is used. Previous work does show that it is possible to transfer the learning to a new location or angle if the individual also practices another, seemingly irrelevant, task at the same or a later time – such as judging how bright the line is. To understand what might be happening to produce these seemingly conflicting results, Xiong et al. used a technique called “continuous flash suppression” with human volunteers. This approach meant that the volunteers were shown an object (such as an angled line) in one eye, while their other eye viewed white noise similar to the “snowflakes” seen on an old-fashioned un-tuned television screen. The flashing snowflakes in one eye meant that the volunteers were not consciously aware of the presence of the angled line in the other eye. The experiments revealed that perceptual learning at the new location or line angle happened when a subconsciously-observed object was shown in the new location or angle, or when the volunteers were asked to pay attention to the “subconscious object” when no object was actually there. This suggests that perceptual learning can happen in new conditions both through ‘bottom-up’ processes, which rely entirely on information coming in from the senses, and ‘top-down’ processes, which are influenced by what a person is aware of and paying attetion to. What is more, the results suggest that the classical observations of specificity in perceptual learning are likely to be a result of the lack of bottom-up and top-down influences in the untrained condition, when the volunteers work hard to improve their performance with the trained condition. Future studies could directly look at what is going on in the brain when perceptual learning becomes less specific, for example by using a technique like functional magnetic resonance imaging to measure brain activity.

Prophylaxis and remediation of anomia in the semantic and logopenic variants of primary progressive aphasia

ABSTRACTThis study evaluated the efficacy of phonological and orthographic treatments for anomia in the semantic and logopenic variants of primary progressive aphasia (svPPA and lvPPA, respectively). Both treatments were administered for 6 months. The treatment stimuli consisted of nouns that were consistently named correctly at baseline (prophylaxis items) and/or nouns that were consistently named incorrectly at baseline (remediation items). Oral naming accuracy was measured for trained and untrained picture exemplars, as well as matched items from an untrained condition (UC). Written naming and scene description tasks were also conducted. For all tasks, the change in naming accuracy from baseline to 1 month post-treatment was compared between the UC and each treatment condition. These comparisons indicated that both treatments were effective in the remediation and prophylaxis of anomia in both variants. Furthermore, generalisation to untrained exemplars occurred in both subtypes, whereas item generalisation occurred in lvPPA, and task generalisation was present in svPPA.

Maintenance of Anomia Treatment Effects in Primary Progressive Aphasia

Maintenance of Anomia Treatment Effects in Primary Progressive Aphasia

The incremental stimulus intensity effect in the habituation of the eyeblink response in humans

Investigation of the eyeblink response of humans to auditory and tactile stimulation focused on the determinants of the so called incremental stimulus intensity effect. In Experiment 1, two groups of participants were exposed to 100 tones from 60 to 87-dB in intensity. In Group Incremental, the tones increased from 60- to 87-dB in 3-dB steps, whereas participants in Group Random received the same intensities in a pseudorandom order. The performance of the two groups was compared to Group Constant that received all 100 tones at 90-dB intensity and to a fourth group, named “Apparatus” that received no stimulation. In a subsequent testing block, the results indicated that there was less responding to a 90-dB tone in the Incremental than in the other three groups, which replicates the incremental stimulus intensity effect. The novel observation was that there was also significantly less responding in the Incremental than in the other three groups to an untrained tactile stimulus, suggesting that the differences between the conditions may have implicated differences in a more general sensitization, in addition to any differences in stimulus-specific habituation. Experiment 2 demonstrated that repetition of tones at a fixed intensity caused a decrease in responding to the tones, but also an increase in responding to a novel tactile stimulus, as compared to an untrained condition. These results are discussed in terms of the interpretation of the incremental stimulus intensity effect suggested by Davis and Wagner (1969) and the AESOP (Wagner & Brandon, 1989) treatment of habituation and sensitization.

Effects of an aerobic training and training cessation on skeletal muscle ultrastructure in domestic dogs

Abstract Introduction: Microbiopsies of the M.adductor magnus, which is an important locomotor muscle were taken to study the effects of six weeks of moderate aerobic treadmill training and their reversibility after a training pause of nine weeks in a group of seven Foxhound-Boxer-Ingelheim Labrador crossbreds. Materials and Methods: To study changes of myofibre morphometry standard morphometric methods were applied using light and transmission electron micrographs. Results: The capillary density was higher in trained condition than in untrained condition and after the end of training. In contrast, the capillaries per iber as well as the capillary-to-iber ratio, the distance between neighboring capillaries and the capillary supply area showed no significant change. Smaller myofibre diameters were found in muscles of dogs in trained condition when compared to the untrained condition but not when compared to myofibres nine weeks after the end of training. Training led to increases in the volume fraction of mitochondria within myofibres and an increase of the surface density of cristae within the mitochondria. The ratio of the surface density to the volume fraction of the mitochondria increased in response to training. Except for the decrease in myofibre diameter, all of the reported changes were reversible and measurements nine weeks after cessation of training did not differ from measurements before training started. Conclusion: The results of this study emphasize the ability of dogs to rapidly and flexibly adjust locomotor muscles to changing exercise regimes by up-and down regulation of the number and inner structure of the mitochondria while the capillary network remains stable.

Transfer of learning between unimanual and bimanual rhythmic movement coordination: transfer is a function of the task dynamic.

Under certain conditions, learning can transfer from a trained task to an untrained version of that same task. However, it is as yet unclear what those certain conditions are or why learning transfers when it does. Coordinated rhythmic movement is a valuable model system for investigating transfer because we have a model of the underlying task dynamic that includes perceptual coupling between the limbs being coordinated. The model predicts that (1) coordinated rhythmic movements, both bimanual and unimanual, are organised with respect to relative motion information for relative phase in the coupling function, (2) unimanual is less stable than bimanual coordination because the coupling is unidirectional rather than bidirectional, and (3) learning a new coordination is primarily about learning to perceive and use the relevant information which, with equal perceptual improvement due to training, yields equal transfer of learning from bimanual to unimanual coordination and vice versa [but, given prediction (2), the resulting performance is also conditioned by the intrinsic stability of each task]. In the present study, two groups were trained to produce 90° either unimanually or bimanually, respectively, and tested in respect to learning (namely improved performance in the trained 90° coordination task and improved visual discrimination of 90°) and transfer of learning (to the other, untrained 90° coordination task). Both groups improved in the task condition in which they were trained and in their ability to visually discriminate 90°, and this learning transferred to the untrained condition. When scaled by the relative intrinsic stability of each task, transfer levels were found to be equal. The results are discussed in the context of the perception-action approach to learning and performance.