Effects of trying 'not to move' instruction on cortical load and concurrent cognitive performance.

Motor and cognitive tasks often interfere when performed concurrently. The amount of interference typically scales with difficulty of the tasks involved. Thus, supposedly 'easy' motor tasks with restricted movement amplitude, like sitting on a chair, should show little or no interference with cognitive tasks at all. We measured the processing load induced by different postural tasks and their effect on cognitive performance under cognitive-motor dual-task conditions. Sixteen subjects performed postural motor tasks in three different positions: 'Lying in a sun lounger', 'Sitting on a bike saddle', and 'Upright on feet'. In each position, three different movement instructions were given; 'Stay stock-still', 'Relax', 'Move easily'. Each combination of position and instruction was performed as single task but also in a dual-task condition with a concurrent calculation task. Brain activity in the right prefrontal cortex was monitored using functional near-infrared spectroscopy. The instruction to 'Stay stock-still' produced higher cortical loads in single-task conditions for all positions compared to all other instructions. The calculation task induced additional brain activity in the same prefrontal area as the motor task. Calculation performance tended to be reduced in the 'Lying'-'Stay stock-still' condition. We discuss the relevance of these findings for learning scenarios in school.

Parietal and premotor cortices: activation reflects imitation accuracy during observation, delayed imitation and concurrent imitation.

This study investigated whether activation within areas belonging to the action observation and imitation network reveals a linear relation to the subsequent accuracy of imitating a bimanual rhythmic movement measured via a motion capturing system. 20 participants were scanned with functional magnetic resonance imaging (fMRI) when asked to imitate observed bimanual movements either concurrently versus with a delay (2s) or simply to observe the movements without imitation. Results showed that action observation relates to activation within classic mirror-related areas. Activation patterns were more widespread when participants were asked to imitate the movement. During observation with concurrent imitation, activation in the left inferior parietal lobe (IPL) was associated negatively with imitation accuracy. During observation in the delayed imitation condition, higher subsequent imitation accuracy was coupled with higher activation in the right superior parietal lobe (SPL) and the left parietal operculum (POp). During the delayed imitation itself, a negative association between imitation accuracy and brain activation was revealed in the right ventral premotor cortex (vPMC). We conclude that the IPL is involved in online comparison and visuospatial attention processes during imitation, the SPL provides a kinesthetic blueprint during movement observation, the POp preserves body identity, and the vPMC recruits motor representations--especially when no concurrent visual guidance is possible.

Contributions of open-loop and closed-loop control in a continuous tracking task differ depending on attentional demands during practice.

Improving tracking performance requires numerous adjustments in the motor system, including peripheral muscle functions and central motor commands. These commands can rely on sensory feedback processing during tracking, i.e., closed-loop control. In the case of repeated tracking sequences, these commands can rely on an inner representation of the target trajectory to optimize pre-planning, i.e., open-loop control. Implicit learning in a continuous tracking task with repeated sequences proves the availability of an inner target representation, which emerges by learning task regularities, even without explicit knowledge. We hypothesize that the actual use of open-loop or closed-loop control is influenced by the demand for attention. Specifically, we suggest that closed-loop control and its development during practice need attentional resources, whereas open-loop control can work and evolve in a more automatic way without attentional demands. To test this, we investigated motor-control strategies when extensively practicing a continuous compensatory force-tracking task using isometric leg muscle activation, either as a single-motor task or as a motor-cognitive dual task. After training, we found evidence for predominantly closed-loop control in the single-task training group and for open-loop control in the dual-task training group. In particular, we ascertained dual-task motor costs and a weakly developed implicit knowledge of task regularities in the single-task training group. In contrast, in the dual-task training group dual-task motor costs disappeared, while implicit learning was clearly observed. We conclude that motor-cognitive dual-task training may boost implicit motor learning, without necessarily impeding concurrent improvement in the cognitive task. Data repository: reserved doi: https://doi.org/10.5281/zenodo.6759377.

Muscle activity in explicit and implicit sequence learning: Exploring additional measures of learning and certainty via tensor decomposition.

Sequence learning in serial reaction time tasks (SRTTs) is usually inferred through the reaction time measured by a keyboard. However, this chronometric parameter offers no information beyond the time point of the button-press. We therefore examined whether sequence learning can be measured by muscle activations via electromyography (EMG) in a dual-task paradigm. The primary task was a SRTT, in which the stimuli followed a fixed sequence in some blocks, whereas the sequence was random in the control condition. The secondary task stimulus was always random. One group was informed about the fixed sequence, and the other not. We assessed three dependent variables. The chronometric parameter premotor time represents the duration between stimulus onset and the onset of EMG activity, which indicates the start of the response. The other variables describe the response itself considering the EMG activity after response start. The EMG integral was analyzed, and additionally, tensor decomposition was implemented to assess sequence dependent changes in the contribution of the obtained subcomponents. The results show explicit sequence learning in this dual-task setting. Specifically, the informed group show shorter premotor times in fixed than random sequences as well as larger EMG integral and tensor contributions. Further, increased activity seems to represent response certainty, since a decrease is found for both groups in trials following erroneous responses. Interestingly, the sensitivity to sequence and post-error effects varies between the subcomponents. The results indicate that muscle activity can be a useful indicator of response behavior in addition to chronometric parameters.

The self-organized task switching paradigm: Movement effort matters.

The self-organized task switching paradigm enables to investigate the link between task performance and task selection in a voluntary task switching setting that benefits task switches over task repetitions. For example, waiting for a repetition-related stimulus onset denotes environmental costs, which are balanced with internal task-switch costs. Here we extent this research by asking whether movement effort also plays a crucial role for task selection. In detail, we investigate how motor-related consequences, i.e., increasing force for task repetitions, influence task-switching behavior. Participants voluntarily switched between a number (i.e., even or odd) or letter task (i.e., vowel or consonant) using a robot system for response execution. With consecutive task repetitions the robot system was harder to move to the response target as we systematically added a damping load. We found that switch rate correlated with cognitive switch costs (i.e., costs in: reaction time, r = -0.741, and error rate, r = -0.545), and motor repetition cost represented by movement-time increment, r = 0.414. Interestingly, switch rate also correlated with individual force maximum, r = -0.480. However, switch rate did not correlate with movement-impulse increment, r = -0.033. Stepwise multiple regression analyses across participants revealed that 66% of variance are explained including all predicting factors. Yet, only cognitive costs and individual force maximum reached significant importance in the regression model. Hence, we extended switch-rate analyses using linear regression on a within-subject level, and thus, keeping individual force maximum constant. We found about 84% of variance explained by motor and cognitive costs. Thereby, movement impulse predicted task selection more than reaction time and more than movement time. Thus, we demonstrated that both cognitive and motor consequences influence task-switch behavior. Furthermore, we showed that task selection is importantly modulated by motor effort related to individual motor skills.

Prescheduled Interleaving of Processing Reduces Interference in Motor-Cognitive Dual Tasks.

Continuous motor tasks like walking have the potential to allow a dynamic allocation of processing resources when interrupted by intermittent cognitive tasks. The degree to which a successful interleaving of processing streams of both tasks is possible may depend on the temporal regularity of events. Fifteen subjects participated in an experiment where we systematically manipulated the regularity of stimulus onsets in a 2-back task relative to the step cycle. We tested three conditions where stimulus onset was always synchronous to a defined event in the stride (right heel strike, left heel strike, and midway between two heel strikes) and two conditions where the temporal location of the stimulus shifted from stride to stride. In order to test for potential effects of task difficulty, we also manipulated walking speed. We measured reaction times, accuracy of the reactions and several measures describing motor performance. There was no sign of task interference in these measures when stimuli always appeared at the same relative location within the step cycle. However, we observed prolonged reaction times when the stimulus came up earlier than expected. Surprisingly, in the other non-regular regime, where the stimulus appeared later than expected, reaction times were fastest. We interpret this result in the light of a prescheduled allocation of processing resources that is linked to the cyclic profile of processing requirements of the motor task.

Empirical Support for 'Hastening-Through-Re-Automatization' by Contrasting Two Motor-Cognitive Dual Tasks.

Motor-cognitive dual tasks have been intensely studied and it has been demonstrated that even well practiced movements like walking show signs of interference when performed concurrently with a challenging cognitive task. Typically walking speed is reduced, at least in elderly persons. In contrast to these findings, some authors report an increased movement frequency under dual-task conditions, which they call hastening. A tentative explanation has been proposed, assuming that the respective movements are governed by an automatic control regime. Though, under single-task conditions, these automatic processes are supervised by "higher-order" cognitive control processes. However, when a concurrent cognitive task binds all cognitive resources, the automatic process is freed from the detrimental effect of cognitive surveillance, allowing higher movement frequencies. Fast rhythmic movements (>1 Hz) should more likely be governed by such an automatic process than low frequency discrete repetitive movements. Fifteen subjects performed two repetitive movements under single and dual-task condition, that is, in combination with a mental calculation task. According to the expectations derived from the explanatory concept, we found an increased movement frequency under dual-task conditions only for the fast rhythmic movement (paddleball task) but not for the slower discrete repetitive task (pegboard task). fNIRS measurements of prefrontal cortical load confirmed the idea of an automatic processing in the paddleball task, whereas the pegboard task seems to be more controlled by processes interfering with the calculation related processing.