Monika Thomas

The effect of rest breaks on human sensorimotor adaptation

We have studied the effect of rest breaks on sensorimotor adaptation to rotated visual feedback in a pointing task. Adaptive improvement was significantly poorer after 1-s breaks than after 5–40-s breaks, with no significant difference among the latter break durations. The benefit of >1-s breaks emerged soon after the onset of adaptation, and then remained steady throughout the adaptation, retention (next day), and persistence (no feedback) phases. This pattern of findings indicates that break-induced facilitation is not a result of strategic adjustments, motivation, or recovery from fatigue, but rather to consolidation of previously acquired sensorimotor recalibration rules.

Concurrent adaptation to four different visual rotations

The human sensorimotor system can concurrently adapt to two different distortions without interference when the distortions are cued by different contexts. We investigated whether this holds with four distortions as well. Subjects were exposed to an interlaced sequence of +30°, −30°, +60°, and −60° visuomotor rotations as the adaptation phase, cued by combinations of workspace location and by the arm used. Adaptation phase was followed by two episodes in each condition without any distortion testing the aftereffects. Results showed that the error at the onset of adaptation gradually decreased during adaptation to all four distortions without any sign of interference between the conditions. Furthermore, aftereffects of adaptation to ±30° rotation were significantly greater than of adaptation to ±60° rotation. We conclude that the human sensorimotor system is able to concurrently adapt to four different visual distortions when they are cued by different contexts. However, the results of aftereffects are ambiguous: Recalibration could be based on at least four parallel modules.

Is sensorimotor adaptation to position- and velocity-dependent visual distortions based on distinct adaptive processes?

It is widely held that sensorimotor adaptation to different distortions is brought about by separate, distortion-specific processes which compete for the limited resources of short-term motor memory when they are activated in close temporal succession. Here we scrutinized this view by exposing participants sequentially to two distortions of equal or of opposite polarity, one proportional to the position, and the other to the velocity of their hand. We found movement errors to be largest in participants who were pre-adapted to a distortion of different type and opposite polarity, smaller in novice participants, and smaller still in participants who were pre-adapted to a distortion of different type and same polarity. The interference observed with opposite-polarity distortions can be explained by the existence of competing, independent, or cooperative adaptive processes. However, the facilitation observed with equal-polarity distortions is in quantitative disagreement with the competing- and independent-processes view, but is consistent with the cooperative-processes view. We therefore conclude that adaptation to position- and velocity-dependent visual distortions can be based on cooperative processes.

The Effects of Slackline Balance Training on Postural Control in Older Adults

The present study investigated whether slackline training enhances postural control in older adults. Twenty-four participants were randomized into an intervention and a control group. The intervention group received 6 weeks of slackline training, two times per week. Pre-post measurement included the time of different standing positions on a balance platform with and without an external disturbance and the acceleration of the balance platform. Results showed significantly improved standing times during one-leg stance without external disturbance and a significantly reduced acceleration of the balance platform for the intervention group after the training period during tandem stance with and without an external disturbance. We conclude that slackline training in older adults has a positive impact on postural control and thus on the reduction of fall risk.

EEG coherence during mental rotation of letters, hands and scenes

The purpose of the present study was to investigate differences in the electrocortical synchronization pattern during mental rotation of three different object categories as well as six different rotation angles. Therefore, event-related coherence of the electroencephalographic (EEG) activity between selective frontal and parietal electrode pairs of ten subjects was measured during the performance of a mental rotation task consisting of rotation of letters, hands and scenes. Statistical analysis showed an increased coherence of frontal and parietal electrode pairs for the condition LETTER in comparison to the other conditions in the alpha1- (8.5-10 Hz) and alpha2-band (10, 5-12 Hz) supporting the notion of different mental rotation mechanisms for externally and internally represented objects. Additionally decreased coherence of the frontal and parietal electrode pairs was found for the rotation angles 30° to 150° in comparison to the 0° and 180° rotations for the alpha1- and alpha2-band as well as the gamma frequency band (30-45 Hz). It is assumed that this decrease of synchronization reflects the mental rotation process implying that the mental rotation process of 180° differs from the rotation process of all other rotation angles.

Motor Imagery and Mental Training in Older Adults

Research has shown that mental training in terms of motor imagery (MI) can enhance movement skills and physical performance in younger adults. It has been used effectively in various settings for different objectives, and its application and benefits are well established for athletes. Yet, little is known about the benefits of mental training and MI for healthy older adults. In this chapter, we introduce the mechanisms underlying MI and provide a brief overview of MI research and mental training, focusing on healthy older adults. Finally, we describe the procedures and results of a recently conducted mental training intervention study that aimed at improving postural control in older adults.

Age-related differences of neural connectivity during mental rotation.

The purpose of the present study was to investigate age-related effects on functional brain networks during a mental rotation task. At behavioral level age-related cognitive deficits have been shown. Cognitive deficits in older adults are associated with structural decline, especially in frontal and parietal areas and in the corpus callosum. In consequence, functional networks are affected by old age as well. To this end, a graph theoretical approach was taken, which quantifies the global and local efficiency as well as the cost efficiency of frontal and parietal intrahemispheric and interhemispheric networks. Main results indicate that intrahemispheric and interhemispheric networks are differently affected by older age: in the left frontal and the left and right parietal intrahemispheric networks global and local efficiency was reduced, whereas in frontal and parietal interhemispheric networks cost efficiency was decreased.

Do pictures help to memorize? The influence of item presentation and executive functions on everyday memory in older adults

Abstract Ageing is associated with a declining memory performance. This phenomenon has been extensively investigated in different laboratory settings, while the transferability from laboratory findings to everyday life situations is rather unclear. In fact, everyday life situations have been found to enhance as well as impair older adults’ memory performance. The present study deals with the question which kind of factors influence memory performance of older adults during everyday life situations. Therefore, participants (70.16 ± 5.8 years) were exposed to a supermarket scenario. Their task was to collect previously presented objects in a specified order while objects were either presented as words or pictures in correct or randomized order. Additionally, participants performed the Stroop test, Trail making test and Bochumer Matrizen test, in order to determine a possible predictability of the performance of these tasks and everyday life performance. Results showed that older adults had more problems to memorize items in the more challenging (randomized item presentation) task but presentation via pictures could offset this effect.