Classification characteristics of fine motor experts based on electroencephalographic and force tracking data.

The application of machine learning techniques provides a data-driven approach for a deeper understanding of the development and expressions of expertise. In extension to the common procedure of comparing experts' and novices' performances in expertise-domain-related tasks we applied conventional classification algorithms. We distinguished between tasks for each participant and between groups, i.e., experts or novices, based on electroencephalographic (EEG) activity patterns and force output variables during four different force modulation tasks. The tasks under investigation involved sinusoidal and steady force tracking tasks, which were performed with the left and right hand. Classification of tasks based on EEG patterns as well as force output was possible with high accuracy in novices and experts, whereas classification of group membership, i.e., experts or novices, was at chance level. In follow-up analyses, we found a high degree of individuality in the EEG patterns of the experts, implying the long-term development of specialized central processing during fine motor tasks in fine motor experts. Taken together, the results suggest that continuous practice in the work context leads to the development of a highly individual and task-specific central control pattern.

Classification of visuomotor tasks based on electroencephalographic data depends on age-related differences in brain activity patterns.

Classification of physiological data provides a data driven approach to study central aspects of motor control, which changes with age. To implement such results in real-life applications for elderly it is important to identify age-specific characteristics of movement classification. We compared task-classification based on EEG derived activity patterns related to brain network characteristics between older and younger adults performing force tracking with two task characteristics (sinusoidal; constant) with the right or left hand. We extracted brain network patterns with dynamic mode decomposition (DMD) and classified the tasks on an individual level using linear discriminant analysis (LDA). Next, we compared the models' performance between the groups. Studying brain activity patterns, we identified signatures of altered motor network function reflecting dedifferentiated and compensational brain activation in older adults. We found that the classification performance of the body side was lower in older adults. However, classification performance with respect to task characteristics was better in older adults. This may indicate a higher susceptibility of brain network mechanisms to task difficulty in elderly. Signatures of dedifferentiation and compensation refer to an age-related reorganization of functional brain networks, which suggests that classification of visuomotor tracking tasks is influenced by age-specific characteristics of brain activity patterns. In addition to insights into central aspects of fine motor control, the results presented here are relevant in application-oriented areas such as brain computer interfaces.

Regular participation in leisure time activities and high cardiovascular fitness improve motor sequence learning in older adults.

INTRODUCTION: Older adults show higher interindividual performance variability during the learning of new motor sequences than younger adults. It is largely unknown what factors contribute to this variability. This study aimed to, first, characterize age differences in motor sequence learning and, second, examine influencing factors for interindividual performance differences. METHOD: 30 young adults (age M = 21.89, SD = 2.08, 20 female) and 29 older adults (age M = 69.55, SD = 3.03, 18 female) participated in the study. Motor sequence learning was assessed with a discrete sequence production (DSP) task, requiring key presses to a sequence of visual stimuli. Three DSP practice phases (á 8 blocks × 16 sequences, two six-element sequences) and two transfer blocks (new untrained sequences) were performed. Older participants conducted the Mini-Mental Status Examination and a visuospatial working-memory task. All participants finished a questionnaire on everyday leisure activities and a cardiovascular fitness test. RESULTS: Performance speed increased with practice in both groups, but young improved more than older adults (significant Group × Time effect for response time, F(1,5) = 4.353, p = 0.004, [Formula: see text] = 0.071). Accuracy did not change in any age group (non-significant Group × Time effect for error rates, F(1,5) = 2.130, p = 0.091, [Formula: see text] = 0.036). Older adults revealed lower transfer costs for performance speed (significant Time × Group effect, e.g., simple sequence, F(1,2) = 10.511, p = 0.002, [Formula: see text] = 0.156). High participation in leisure time activities (ß = - 0.58, p = 0.010, R2 = 0.45) and high cardiovascular fitness (ß = - 0.49, p = 0.011, R2 = 0.45) predicted successful motor sequence learning in older adults. DISCUSSION: Results confirmed impaired motor learning in older adults. Younger adults seem to show a better implicit knowledge of the practiced sequences compared to older adults. Regular participation in leisure time activities and cardiovascular fitness seem to prevent age-related decline and to facilitate motor sequence performance and motor sequence learning in older adults.

Not only age but also tactile perception influences the preference for cosmetic creams applied to the forearm.

OBJECTIVE: We aimed to examine whether and how age as well as tactile sensitivity and perception had an impact on how women liked richer and lighter creams. Furthermore, the question arose if age and tactile perception had an influence on the ability to distinguish between the creams and how the ability to distinguish between creams influenced the liking of these creams. METHODS: A total of 299 female participants were invited to rate how much they liked four different cosmetic creams applied to their forearms. The creams were based on the same base formula but differed with respect to the texture. In order to arouse the impression of more lightness (quasi-light) or more richness (quasi-rich), polyethylene particles of different sizes were added to the base formula. First of all, the participants were tested for their tactile sensitivity and perception. Tactile sensitivity was tested by Von Frey filaments, tactile spatial perception by the tactile Landolt ring test and the ability to discriminate surface structures by a sandpaper test. Furthermore, the participants rated the creams with respect to the acceptance, the subjective skin feeling after application and performed paired-comparison tests. Analyses of variance and regression analyses were applied to the data. RESULTS: In general, participants liked quasi-rich creams less than quasi-light creams. However, older women compared to younger women and women with lower tactile performance in comparison with women with higher tactile performance revealed a weaker influence of cream type-specific acceptance ratings. Further results revealed that young participants perceived the quasi-light creams (with particles of ~50 µm diameter) as soft and quasi-rich creams (with particles of ~100 µm and ~165 µm diameter), as coarse. In contrast, this subjective skin feeling after application in participants at age 50 and older did not differ much. CONCLUSION: Age and tactile perceptual abilities have additive effects on the acceptance of creams with different textures when applied to the forearm.

Exercise-induced changes in basal ganglia volume and cognition in older adults.

Physical activity has been demonstrated to diminish age-related brain volume shrinkage in several brain regions accompanied by a reduction of age-related decline in cognitive functions. Most studies investigated the impact of cardiovascular fitness or training. Other types of fitness or training are less well investigated. In addition, little is known about exercise effects on volume of the basal ganglia, which, however, are involved in motor activities and cognitive functioning. In the current study (1) we examined the relationships of individual cardiovascular and motor fitness levels with the volume of the basal ganglia (namely caudate, putamen, and globus pallidus) and selected cognitive functions (executive control, perceptual speed). (2) We investigated the effect of 12-month training interventions (cardiovascular and coordination training, control group stretching and relaxation) on the volume of the respective basal ganglia nuclei. Results revealed that motor fitness but not cardiovascular fitness was positively related with the volume of the putamen and the globus pallidus. Additionally, a moderating effect of the volume of the basal ganglia (as a whole, but also separately for putamen and globus pallidus) on the relationship between motor fitness and executive function was revealed. Coordination training increased caudate and globus pallidus volume. We provide evidence that coordinative exercise seems to be a favorable leisure activity for older adults that has the potential to improve volume of the basal ganglia.

[Activity, physical and psychological mobility in old age]. / Bewegung, körperliche und geistige Mobilität im Alter.

Old age and aging are accompanied by a number of physical and mental changes. However, these so-called age-dependent processes are not exclusively genetically determined or irreversible but can be partially delayed, prevented, or compensated and some can even be reversed. The goal of this article is to highlight the plasticity, or the "mobility", of physical and mental aging. We will point out in what respects an appropriate lifestyle or purposeful interventions can positively influence the reserve capacity of aging human beings and the aging process. Using the example of physical activity, we will illustrate how we can influence physiological development, cognitive performance, longevity, as well as the development and the occurrence of chronic diseases. Additionally, it is shown that cognitive development is malleable as well. It is facilitated or debilitated by behavior and activity-this covers not only cognitive but also physical activity. It is our particular concern to demonstrate the close interconnectedness of body and mind.

Activity patterns of human somatosensory cortex adapt dynamically to stimulus properties.

Long-term synchronous tactile stimulation of two sites of the body results in integrated, overlapping cortical representations whereas asynchronous stimulation leads to segregated representations. To investigate the cortical capacity to adapt dynamically to stimulation properties 22 subjects were stimulated at digits 1, 3 and 5 of both hands in either random or fixed order. Changes in the functional organization of the somatosensory cortex were inferred by neuromagnetic source analysis based on somatosensory evoked magnetic fields. Compared to the stimulation in random sequence, the stimulation in fixed order revealed a reduction in distance between the cortical representation of D1 and D3. We conclude that the pattern of activation in the somatosensory cortex adapts dynamically to the spatio-temporal characteristics of the stimuli.

fMRI evaluation of somatotopic representation in human primary motor cortex.

We used fMRI to map foot, elbow, fist, thumb, index finger, and lip movements in 30 healthy subjects. For each movement type confidence intervals of representational sites in the primary motor cortex (M1) were evaluated. In order to improve the precision of their anatomical localization and to optimize the mapping of cortical activation sites, we used both the assessment of locations in the conventional 3D system and a 2D projection method. In addition to the computation of activation maxima of activation clusters within the precentral gyrus, centers of gravity were determined. Both methods showed a high overlap of their representational confidence intervals. The 2D-projection method revealed statistically significant distinct intralimb locations, e.g., elbow versus index finger movements and index finger versus thumb movements. Increased degree of complexity of finger movements resulted in a spread of the somatotopic location toward the arm representation. The 2D-projection method-based fMRI evaluation of limb movements showed high precision and was able to reveal differences in intralimb movement comparisons. fMRI activation revealed a clear somatotopic order of movement representation in M1 and also reflected different degrees of complexity of movement.

Tactile coactivation-induced changes in spatial discrimination performance.

We studied coactivation-based cortical plasticity at a psychophysical level in humans. For induction of plasticity, we used a protocol of simultaneous pairing of tactile stimulation to follow as closely as possible the idea of Hebbian learning. We reported previously that a few hours of tactile coactivation resulted in selective and reversible reorganization of receptive fields and cortical maps of the hindpaw representation of the somatosensory cortex of adult rats (Godde et al., 1996). In the present study, simultaneous spatial two-point discrimination was tested on the tip of the right index finger in human subjects as a marker of plastic changes. After 2 hr of coactivation we found a significant improvement in discrimination performance that was reversible within 8 hr. Reduction of the duration of the coactivation protocol revealed that 30 min was not sufficient to drive plastic changes. Repeated application of coactivation over 3 consecutive days resulted in a delayed recovery indicating stabilization of the improvement over time. Perceptual changes were highly selective because no transfer of improved performance to fingers that were not stimulated was found. The results demonstrate the potential role of sensory input statistics (i.e., their probability of occurrence and spatiotemporal relationships) in the induction of cortical plasticity without involving cognitive factors such as attention or reinforcement.

Optical imaging of cat auditory cortical organization after electrical stimulation of a multichannel cochlear implant: differential effects of acute and chronic stimulation.

OBJECTIVE: To study the effects of electrical stimulation on cortical activation patterns. MATERIALS AND METHODS: Optical imaging of auditory cortex in cats that are acutely and chronically electrically stimulated with cochlear implants. RESULTS: Chronic electrical stimulation results in expansion of cortical territory and overlap. CONCLUSION: Effects of chronic electrical stimulation are comparable to use-dependent cortical plastic reorganization.

Optical imaging of cat auditory cortex cochleotopic selectivity evoked by acute electrical stimulation of a multi-channel cochlear implant.

We measured reflectance changes by means of optical imaging of intrinsic signals to study the effects of acute electrical cochlear stimulation on the topography of the cat auditory cortex. After single-pulse electrical stimulation at selected sites of a multichannel implant device, we found topographically restricted response areas representing mainly the high-frequency range in AI. Systematic variation of the stimulation pairs and thus of the cochlear frequency sites revealed a systematic and corresponding shift of the response areas that matched the underlying frequency organization. Intensity functions were usually very steep. Increasingly higher stimulation currents evoked increasingly larger response areas, resulting in decreasing spatial, i.e. cochleotopic, selectivity; however, we observed only slight positional shifts of the focal zones of activity. Electrophysiological recordings of local field potential maps in the same individual animals revealed close correspondence of the locations of the cortical response areas. The results suggest that the method of optical imaging can be used to map response areas evoked by electrical cochlear stimulation, thereby maintaining a profound cochleotopic selectivity. Further experiments in chronically stimulated animals will shed more light on the degree of functional and reorganizational capacities of the primary cortex and could be beneficial for our understanding of the treatment of profound deafness.

Short-term functional plasticity of cortical and thalamic sensory representations and its implication for information processing.

We studied phenomena, constraints, rules, and implications of cortical plastic reorganization produced by input coactivation patterns in primary somatosensory cortex of adult rats. Intracortical microstimulation (ICMS) and an associative pairing of tactile stimulation (PPTS) induced plastic changes within minutes to hours that were fully reversible. Reorganization of receptive fields and topographic maps was studied with electrophysiologic recordings, mapping techniques, and optical imaging of intrinsic signals. Utilizing the specific advantages of local application of ICMS, we investigated lamina-specific properties of cortical representational plasticity, revealing a prominent role of the input layer IV during plastic reorganization. To study subcortical plasticity, we compared ICMS and intrathalamic microstimulation (ITMS), revealing robust thalamic reorganizations that were, however, much smaller than cortical changes. Using PPTS, we found significant reorganizational processes at the cortical level, including receptive fields, overlap, and cortical representational maps. The protocol was similarly effective at the perceptual level by enhancing the spatial discrimination performance in humans, suggesting that these particular fast plastic processes have perceptual consequences. The implications were discussed with respect to parallel changes of information processing strategies. We addressed the question of the possible role of RF size and size of cortical area, inhibitory mechanisms, and Hebbian and non-Hebbian learning rules. The short time scale of the effects and the aspect of reversibility support the hypothesis of fast modulations of synaptic efficiency without necessarily involving anatomic changes. Such systems of predominantly dynamically maintained cortical and adaptive processing networks may represent the neural basis for life-long adaptational sensory and perceptual capacities and for compensational reorganizations following injuries.

Associative pairing of tactile stimulation induces somatosensory cortical reorganization in rats and humans.

We used a protocol of associative (Hebbian) pairing of tactile stimulation (APTS) to evoke cortical plastic changes. Reversible reorganization of the adult rat paw representations in somatosensory cortex (SI) induced by a few hours of APTS included selective enlargement of the areas of cortical neurones representing the stimulated skin fields and of the corresponding receptive fields (RFs). Late, presumably NMDA receptor-mediated response components were enhanced, indicating an involvement of glutamatergic synapses. A control protocol of identical stimulus pattern applied to only a single skin site revealed no changes of RFs, indicating that co-activation is crucial for induction. Using an analogous APTS protocol in humans revealed an increase of spatial discrimination performance indicating that fast plastic processes based on co-activation patterns act on a cortical and perceptual level.

Optical imaging of rat somatosensory cortex reveals representational overlap as topographic principle.

We measured reflectance changes by means of optical imaging of intrinsic signals to study the topography of the paw representations in rat somatosensory cortex. Following circumscribed tactile stimulation of single digits or pads, we found large and partially overlapping areas of reflectance changes (delta R). The diameters of their focal zones defined at 75% maximal delta R were in the range of 150 microns and preserved all details of the underlying maps. Zones of overlap were in the range 15-25% measured at half-maximal delta R. In contrast, we found sharp boundaries with no overlap between the fore- and hindpaw representations. The data suggest that large and overlapping cortical maps constitute a normal type of neural representation supporting the idea of a distributed neural processing scheme.

Effects of ageing on topographic organization of somatosensory cortex.

Deficits in limb coordination and decreased motor activity have been described in old rats older than 24 months, an approved animal model in ageing research. We investigated the implications of age-related decline of sensorimotor performance by studying the functional cortical organization of aged rats. The cutaneous receptive fields of the hindpaw representations in somatosensory cortex and the cortical areas excited by tactile point-stimulation were enlarged and highly overlapping in old rats when compared with young rats. This gives rise to a complete loss of topographic detail. These functional changes were correlated with the rat's individual walking patterns, indicating that age-related deficits in sensorimotor performance are paralleled by degradation of the functional representations in the ageing nervous system.