Prefrontal activity predicts individual differences in optimal attentional strategy for preventing motor performance decline: a functional near-infrared spectroscopy study

A registered report with a single blind procedure to examine the effect of attentional focus and imagery dominance on dart throwing

External focus of attention (EFOA) has been shown to improve motor performance relative to internal focus of attention (IFOA). Recently, studies have shown that this attentional focus effect may depend upon an individual difference (i.e., motor imagery): Those with a higher ability to visualize movements benefited more from EFOA, and those with a higher ability to feel movements benefited more from IFOA. However, inconsistent findings exist, potentially due to underpowered studies with various potential biases. Thus, leveraging a registered report and single-blind procedure, we will examine the effect of EFOA and IFOA on dart-throwing performance and how the attentional focus could be altered based on individuals' imagery dominance. Participants will complete a dart-throw task with EFOA and IFOA. Then, participants will complete practice trials with no attentional focus, which will be followed by another set of performance trials with EFOA and IFOA. This study will examine whether the effect of attentional focus instruction will persist in a single-blind study and explore its effect on imagery dominance.

Dominance of attentional focus: a comparative study on its impact on standing postural control in healthy younger and older adults

Introduction

Attentional focus is a phenomenon in which shifting the focus of attention alters performance of standing postural control. It can be categorized as internal focus (IF), which directs attention to the body parts, or external focus (EF), which directs attention to the external environment. Although attentional focus that improves standing postural control in younger people exhibits individual dominance, the dominance of attentional focus in standing postural control in older adults remains ambiguous. Therefore, this study aimed to compare the dominance of attentional focus in standing postural control between healthy younger and older adults, a crucial step for understanding the aging process.

Methods

The participants performed a standing postural control task under the IF and EF conditions. Based on the condition during which they exhibited superior performance, the participants were divided into two groups: IF-dominant and EF-dominant. The standing postural control performance in each group under the IF and EF conditions was subsequently compared.

Results

The results showed that the participants, encompassing both younger and older adults, were divided into the IF-dominant and EF-dominant groups, confirming the dominance of attentional focus. The performance under the EF condition in older adults was also influenced by the dominance of attentional focus.

Conclusion

These results highlight the potential importance of intervention methods based on the dominance of attentional focus, providing valuable insights into future research and clinical practice.

The Effect of Motor Imagery Practice on an Aiming Task with Attentional Focus Cues

When one directs their attention to an intended effect (external focus of attention, EFOA), motor performance is generally better than when one directs their attention to their own body movements (internal focus of attention, IFOA). However, the effect of attentional focus is unclear when a skill is practiced through motor imagery (MI) in the absence of physical trials. Participants (N = 30, M = 22.33 yrs, SD = 2.69) in the present study completed three physical trials of a reciprocal aiming task before and (24-h) after MI practice. During MI practice, the EFOA (n = 15) and IFOA (n = 15) groups mentally practiced the task with no physical practice with EFOA-MI or IFOA-MI, respectively, for three consecutive days. Our results showed that both groups significantly improved in accuracy (F1,28 = 6.49, p = .017), supporting the benefit of MI in motor skill acquisition. However, a significant effect of attentional focus was not observed (F1.,28 = 0.445, p = 0.51). We discussed two potential explanations: EFOA/IFOA requires physical trials to affect performance, or individuals must use both EFOA and IFOA in the process of creating imagery of the environment and movements, which may obscure the effect of EFOA and IFOA.

Do attentional focus cues affect the type or number of explicit rules? Proof of concepts of the self-invoking trigger or explicit knowledge hypotheses

Internal focus has been shown to be detrimental to performance by disrupting the motor system, whereas external focus enhances performance by promoting automaticity. One hypothesis, which explains the underlying mechanism of the disruption of the motor system, proposes that internal focus affects the type of thoughts (explicit rules) by invoking self-conscious, evaluative thoughts (McKay et al., 2015). In contrast, another hypothesis proposes that internal focus increases the number of explicit rules, loading working memory (Poolton et al., 2006). To examine the competing hypotheses, neurotypical young adults (22.98 ± 4.46 years old, n = 20 males, n = 40 females) were assigned to one of three groups: external focus (n = 20), internal focus (n = 20), and control (n = 20) groups, and practiced a reciprocal aiming task for two days with retention/transfer tests. Between trials, participant's thoughts were evaluated by an open-ended questionnaire. The type of explicit rules was analyzed using a chi-square test, and the number of explicit rules was analyzed using a mixed-effect Poisson regression. The results showed that external focus resulted in a greater proportion of explicit rules about the task and a lesser proportion of self-evaluative thoughts. The number of explicit rules did not differ between groups. Our results suggest that external focus may strengthen focus on task-relevant features, while internal focus moves people's attention away from important features, potentially explaining why the motor system is disrupted by internal focus.

Predicting poststroke dyskinesia with resting-state functional connectivity in the motor network

SIGNIFICANCE

Motor function evaluation is essential for poststroke dyskinesia rehabilitation. Neuroimaging techniques combined with machine learning help decode a patient's functional status. However, more research is needed to investigate how individual brain function information predicts the dyskinesia degree of stroke patients.

AIM

We investigated stroke patients' motor network reorganization and proposed a machine learning-based method to predict the patients' motor dysfunction.

APPROACH

Near-infrared spectroscopy (NIRS) was used to measure hemodynamic signals of the motor cortex in the resting state (RS) from 11 healthy subjects and 31 stroke patients, 15 with mild dyskinesia (Mild), and 16 with moderate-to-severe dyskinesia (MtS). The graph theory was used to analyze the motor network characteristics.

RESULTS

The small-world properties of the motor network were significantly different between groups: (1) clustering coefficient, local efficiency, and transitivity: MtS > Mild > Healthy and (2) global efficiency: MtS < Mild < Healthy. These four properties linearly correlated with patients' Fugl-Meyer Assessment scores. Using the small-world properties as features, we constructed support vector machine (SVM) models that classified the three groups of subjects with an accuracy of 85.7%.

CONCLUSIONS

Our results show that NIRS, RS functional connectivity, and SVM together constitute an effective method for assessing the poststroke dyskinesia degree at the individual level.

Is cognitive control of perception and action via attentional focus moderated by motor imagery?

Motor imagery (MI) has emerged as an individual factor that may modulate the effects of attentional focus on motor skill performance. In this study, we investigated whether global MI, as well as its components (i.e., kinesthetic MI, internal visual MI, and external visual MI) moderate the effect of attentional focus on performance in a group of ninety-two young adult novice air-pistol shooters (age: M = 21.87, SD = 2.54). After completing the movement imagery questionnaire-3 (MIQ-3), participants were asked to complete a pistol shooting experiment in three different attentional focus conditions: (1) No focus instruction condition (control condition with no verbal instruction) (2) an internal focus instruction condition, and (3) an external focus condition. Shot accuracy, performance time, and aiming trace speed (i.e., stability of hold or weapon stability) were measured as the performance variables. Results revealed that shot accuracy was significantly poorer during internal relative to control focus condition. In addition, performance time was significantly higher during external relative to both control and internal condition. However, neither global MI, nor its subscales, moderated the effects of attentional focus on performance. This study supports the importance of attentional focus for perceptual and motor performance, yet global MI and its modalities/perspectives did not moderate pistol shooting performance. This study suggests that perception and action are cognitively controlled by attentional mechanisms, but not motor imagery. Future research with complementary assessment modalities is warranted to extend the present findings.

Use-dependent increase in attention to the prosthetic foot in patients with lower limb amputation

Patients with lower limb amputation experience “embodiment” while using a prosthesis, perceiving it as part of their body. Humans control their biological body parts and receive appropriate information by directing attention toward them, which is called body-specific attention. This study investigated whether patients with lower limb amputation similarly direct attention to prosthetic limbs. The participants were 11 patients with lower limb amputation who started training to walk with a prosthesis. Attention to the prosthetic foot was measured longitudinally by a visual detection task. In the initial stage of walking rehabilitation, the index of attention to the prosthetic foot was lower than that to the healthy foot. In the final stage, however, there was no significant difference between the two indexes of attention. Correlation analysis revealed that the longer the duration of prosthetic foot use, the greater the attention directed toward it. These findings indicate that using a prosthesis focuses attention akin to that of an individual’s biological limb. Moreover, they expressed that the prosthesis felt like a part of their body when they could walk independently. These findings suggest that the use of prostheses causes integration of visual information and movement about the prosthesis, resulting in its subjective embodiment.

Attentional focus effect on dual-task walking in Parkinson's disease with and without freezing of gait

In Parkinson's disease, the optimal attentional focus strategy for dual-task walking may vary with freezing of gait (FOG), due to different severities of impaired automaticity. The study aimed to investigate (i) the immediate effect of attentional focus on dual-task walking in participants with and without FOG, and (ii) the training effect of attentional focus on walking, FOG, and falls. In experiment 1, FOG and non-FOG groups (16 participants each) performed a dual-task of holding two interlocking rings apart while walking, either without attention instruction or with instructions to focus attention internally or externally. Gait parameters and ring-touching times were measured. In experiment 2, 30 participants with FOG were randomized to 6 weeks of dual-task training with internal-focus or external-focus instruction. Before and after training, we recorded timed up-and-go (TUG) and TUG dual-task (TUGdt) in on-medication and off-medication states, and the numbers of FOG episodes and falls. The non-FOG group showed less step length variability and shorter ring-touching times with external-focus. The FOG group showed less step length variability, less cadence, increased gait velocity, and longer step lengths with internal-focus compared to external-focus and no-focus instructions. Both internal-focus and external-focus training reduced FOG and falls after intervention, but only internal-focus training reduced TUG and TUGdt in both on-medication and off-medication states. Our findings suggest external-focus would enhance walking automaticity and the concurrent task accuracy for non-freezers, whereas for freezers, internal-focus could increase gait stability and lead to a more positive effect on improving locomotion control and reducing falling risk.

Individual Sensory Modality Dominance as an Influential Factor in the Prefrontal Neurofeedback Training for Spatial Processing: A Functional Near-Infrared Spectroscopy Study

Neurofeedback is a neuromodulation technique used to improve brain function by self-regulating brain activity. However, the efficacy of neurofeedback training varies widely between individuals, and some participants fail to self-regulate brain activity. To overcome intersubject variation in neurofeedback training efficacy, it is critical to identify the factors that influence this type of neuromodulation. In this study, we considered that individual differences in cognitive ability may influence neurofeedback training efficacy and aimed to clarify the effect of individual working memory (WM) abilities, as characterized by sensory modality dominance, on neurofeedback training efficacy in healthy young adults. In particular, we focused on the abilities of individuals to retain internal (tactile or somatosensory) or external (visual) body information in their WM. Forty participants performed functional near-infrared spectroscopy-based neurofeedback training aimed at producing efficient and lower-level activity in the bilateral dorsolateral prefrontal cortex and frontopolar cortex. We carried out a randomized, sham-controlled, double-blind study that compared WM ability before and after neurofeedback training. Individual WM ability was quantified using a target searching task that required the participants to retain spatial information presented as vibrotactile or visual stimuli. Participants who received feedback information based on their own prefrontal activity showed gradually decreasing activity in the right prefrontal area during the neurofeedback training and demonstrated superior WM ability during the target searching task with vibrotactile stimuli compared with the participants who performed dummy neurofeedback training. In comparison, left prefrontal activity was not influenced by the neurofeedback training. Furthermore, the efficacy of neurofeedback training (i.e., lower right prefrontal activity and better searching task performance) was higher in participants who exhibited tactile dominance rather than visual dominance in their WM. These findings indicate that sensory modality dominance in WM may be an influential neurophysiological factor in determining the efficacy of neurofeedback training. These results may be useful in the development of neurofeedback training protocols tailored to individual needs.

Individual Optimal Attentional Strategy in Motor Learning Tasks Characterized by Steady-State Somatosensory and Visual Evoked Potentials

Focus of attention is one of the most influential factors facilitating motor performance. Previous evidence supports that the external focus (EF) strategy, which directs attention to movement outcomes, is associated with better motor performance than the internal focus (IF) strategy, which directs attention to body movements. However, recent studies have reported that the EF strategy is not effective for some individuals. Furthermore, neuroimaging studies have demonstrated that the frontal and parietal areas characterize individual optimal attentional strategies for motor tasks. However, whether the sensory cortices are also functionally related to individual optimal attentional strategy remains unclear. Therefore, the present study examined whether an individual’s sensory processing ability would reflect the optimal attentional strategy. To address this point, we explored the relationship between responses in the early sensory cortex and individuals’ optimal attentional strategy by recording steady-state somatosensory evoked potentials (SSSEP) and steady-state visual evoked potentials (SSVEP). Twenty-six healthy young participants first performed a motor learning task with reaching movements under IF and EF conditions. Of the total sample, 12 individuals showed higher after-effects under the IF condition than the EF condition (IF-dominant group), whereas the remaining individuals showed the opposite trend (EF-dominant group). Subsequently, we measured SSSEP from bilateral primary somatosensory cortices while presenting vibrotactile stimuli and measured SSVEP from bilateral primary visual cortices while presenting checkerboard visual stimuli. The degree of increasing SSSEP response when the individuals in the IF-dominant group directed attention to vibrotactile stimuli was significantly more potent than those in the EF-dominant individuals. By contrast, the individuals in the EF-dominant group showed a significantly larger SSVEP increase while they directed attention to visual stimuli compared with the IF-dominant individuals. Furthermore, a significant correlation was observed such that individuals with more robust IF dominance showed more pronounced SSSEP attention modulation. These results suggest that the early sensory areas have crucial brain dynamics to characterize an individual’s optimal attentional strategy during motor tasks. The response characteristics may reflect the individual sensory processing ability, such as control of priority to the sensory inputs. Considering individual cognitive traits based on the suitable attentional strategy could enhance adaptability in motor tasks.

Distinct bilateral prefrontal activity patterns associated with the qualitative aspect of working memory characterized by individual sensory modality dominance

In addition to quantitative individual differences in working memory (WM) capacity, qualitative aspects, such as enhanced sensory modality (modality dominance), can characterize individual WM ability. This study aimed to examine the neurological basis underlying the individual modality dominance component of WM using functional near-infrared spectroscopy (fNIRS). To quantify the degree of individual WM modality dominance, 24 participants were required to find seven hidden targets and hold their spatial location and appearance order with vibrotactile or visual stimuli aids. In this searching task, eight participants demonstrated higher performance with the tactile condition (tactile-dominant) whereas sixteen demonstrated visual dominance. We then measured prefrontal activity by fNIRS during memorization of visual stimulus numbers while finger tapping as a cognitive-motor dual-task. Individual modality dominance significantly correlated with bilateral frontopolar and dorsolateral prefrontal activity changes over repeated fNIRS sessions. In particular, individuals with stronger visual dominance showed marked decreases in prefrontal area activity. These results suggest that distinct processing patterns in the prefrontal cortex reflect an individual’s qualitative WM characteristics. Considering the individual modality dominance underlying the prefrontal areas could enhance cognitive or motor performance, possibly by optimizing cognitive resources.