Mental images across the adult lifespan: a behavioural and fMRI investigation of motor execution and motor imagery

Age bias in changes in finger dexterity based on brain activation and spinal motor nerve excitability induced by motor imagery practice

Elderly adults may have poorer recall ability than young adults and may not fully enjoy the effects of motor imagery. To understand the age bias of the effect of motor imagery on hand dexterity, we evaluated brain activation and spinal motor nerve excitability. Brain activation was evaluated from changes in oxygenated hemoglobin concentration, while spinal motor nerve excitability was evaluated from F-waves in eight young (mean age 21.0 ± 0.5 years) and eight elderly (mean age 69.5 ± 2.3 years) subjects of matched sex ratio at rest and during motor imagery. Purdue Pegboard scores were also measured before and after motor imagery, and changes in hand dexterity were assessed. The results showed that motor imagery improved hand dexterity without an age bias, and in a similar trend, spinal motor nerve excitability increased during motor imagery. Functional brain connectivity analysis showed the formation of a working memory network in both groups. However, in the analysis of single brain region activation, the young group, but not the elderly group, showed increased activity in the supplementary motor cortex during motor imagery. In addition, regardless of age-related changes, causal coupling indicated the supplementary motor cortex was associated with the changes of spinal motor nerve excitability. Although the changes in brain activation during motor imagery were influenced by age, motor imagery-induced improvements in hand dexterity are also expected in the elderly. Furthermore, changes in spinal motor nerve excitability may be useful in determining the qualitative aspects of motor imagery.

Disgust drivers do not impact on the altered body in action representation in anorexia nervosa

Disgust is a powerful emotion that evolved to protect us from contamination and diseases; it also cores to very human feelings, such as shame. In anorexia nervosa, most of the knowledge on disgust regards food. However, disgust can be elicited by varied drivers, including body-related self-disgust, which may be more central to this condition. Here, we investigate in depth how disgust triggers related to the body influence altered representations in anorexia nervosa. Women with anorexia nervosa and healthy women performed the Hand Laterality Task, in which they were asked to judge the laterality of hands without and with a disgust charging feature (i.e., with a body product or with a body violation). We computed accuracy and reaction time for the effect of biomechanical constraints, an index of motor imagery. We also measured the general disgust sensitivity through a self-report questionnaire. Participants with anorexia nervosa were overall less accurate and slower compared with controls, suggesting a non-canonical (i.e., not based on motor imagery) approach to solving the task. However, they showed the same pattern of responses as controls for disgust-charged stimuli, despite reporting higher levels of disgust sensitivity. Our results suggested the absence of specific effects of disgust drivers on the (altered) body in action representation in anorexia nervosa. We discuss this evidence focusing on the role of the psychopathological symptoms characterising anorexia nervosa. We also reflect on the efficacy of experimental methodologies used to detect alterations in body representation in this clinical condition.

Brain state and dynamic transition patterns of motor imagery revealed by the bayes hidden markov model

Motor imagery (MI) is a high-level cognitive process that has been widely applied to brain-computer inference (BCI) and motor recovery. In practical applications, however, huge individual differences and unclear neural mechanisms have seriously hindered the application of MI and BCI systems. Thus, it is urgently needed to explore MI from a new perspective. Here, we applied a hidden Markov model (HMM) to explore the dynamic organization patterns of left- and right-hand MI tasks. Eleven distinct HMM states were identified based on MI-related EEG data. We found that these states can be divided into three metastates by clustering analysis, showing a highly organized structure. We also assessed the probability activation of each HMM state across time. The results showed that the state probability activation of task-evoked have similar trends to that of event-related desynchronization/synchronization (ERD/ERS). By comparing the differences in temporal features of HMM states between left- and right-hand MI, we found notable variations in fractional occupancy, mean life time, mean interval time, and transition probability matrix across stages and states. Interestingly, we found that HMM states activated in the left occipital lobe had higher occupancy during the left-hand MI task, and conversely, during the right-hand MI task, HMM states activated in the right occipital lobe had higher occupancy. Moreover, significant correlations were observed between BCI performance and features of HMM states. Taken together, our findings explored dynamic networks underlying the MI-related process and provided a complementary understanding of different MI tasks, which may contribute to improving the MI-BCI systems.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11571-024-10099-9.

Trait food craving predicts functional connectivity between dopaminergic midbrain and the fusiform food area during eating imagery

Neurofunctional coupling between the dopaminergic midbrain (i.e., ventral tegmental area, VTA) and higher-order visual regions may contribute to food craving, leading to the onset or maintenance of obesity. We recently showed that the VTA resting-state functional connectivity with the occipitotemporal cortex, at the level of the fusiform gyrus (FFG), was specifically associated with trait food craving and the implicit bias for food images, suggesting that VTA-FFG connectivity may reflect the association between the visual representations of food and its motivational properties. To further test this hypothesis, this time we studied task-based functional connectivity in twenty-eight healthy-weight participants while imagining eating their most liked high-calorie (HC) or least liked low-calorie food (LC) or drinking water (control condition). Trait food craving scores were used to predict changes in task-based functional connectivity of the VTA during imagery of HC compared to LC foods (relative to the control condition). Trait food craving was positively associated with the functional connectivity of the VTA with the left FFG: people with higher trait food craving scores show stronger VTA-FFG connectivity, specifically for the imagery of the liked HC foods. This association was not linked to the quality of imagery nor to state measures of craving, appetite, or thirst. These findings emphasize the contribution of the functional coupling between dopaminergic midbrain and higher-order visual regions to food craving, suggesting a neurofunctional mechanism by which the mental representations of the HC food we like can become much more salient if not irresistible.

Temporo-Parietal cortex activation during motor imagery in older adults: A case study of Baduanjin

Age-associated cognitive and motor decline is related to central nervous system injury in older adults. Motor imagery training (MIT), as an emerging rehabilitative intervention, can activate neural basis similar to that in actual exercise, so as to promote motor function in older adults. The complex motor skills rely on the functional integration of the cerebral cortex. Understanding the neural mechanisms underlying motor imagery in older adults would support its application in motor rehabilitation and slowing cognitive decline. Based on this, the present study used functional near infrared spectroscopy (fNIRS) to record the changes in oxygen saturation in older adults (20 participants; mean age, 64.8 ± 4.5 years) during Baduanjin motor execution (ME) and motor imagery (MI). ME significantly activated the left postcentral gyrus, while the oxy-hemoglobin concentration in the right middle temporal gyrus increased significantly during motor imagery. These results indicate that advanced ME activates brain regions related to sensorimotor function, and MI increases the activation of the frontal-parietal cortex related to vision. In older adults, MI overactivated the temporo-parietal region associated with vision, and tend to be activated in the right brain.

EEG Reveals Alterations in Motor Imagery in People With Amnestic Mild Cognitive Impairment

OBJECTIVES

Motor imagery has been used to investigate the cognitive mechanism of motor control. Although behavioral and electrophysiological changes in motor imagery in people with amnestic mild cognitive impairment (aMCI) have been reported, deficits in different types of imagery remain unclear. To explore this question, we used electroencephalography (EEG) to study neural correlates of visual imagery (VI) and kinesthetic imagery (KI) and their relationship to cognitive function in people with aMCI.

METHODS

A hand laterality judgment task was used to induce implicit motor imagery in 29 people with aMCI and 40 healthy controls during EEG recording. Mass univariate and multivariate EEG analysis was applied to explore group differences in a data-driven manner.

RESULTS

Modulation of stimuli orientation to event-related potential (ERP) amplitudes differed significantly between groups at 2 clusters located in the posterior-parietal and frontal areas. Multivariate decoding revealed sufficient representation of VI-related orientation features in both groups. Relative to healthy controls, the aMCI group lacked accurate representation of KI-related biomechanical features, suggesting deficits in automatic activation of KI strategy. Electrophysiological correlates were associated with episodic memory, visuospatial function, and executive function. Higher decoding accuracy of biomechanical features predicted better executive function via longer response time in the imagery task in the aMCI group.

DISCUSSION

These findings reveal electrophysiological correlates related to motor imagery deficits in aMCI, including local ERP amplitudes and large-scale activity patterns. Alterations in EEG activity are related to cognitive function in multiple domains, including episodic memory, suggesting the potential of these EEG indices as biomarkers of cognitive impairment.

TMS over dorsolateral prefrontal cortex affects the timing of motor imagery but not overt action: Further support for the motor-cognitive model

The Motor-Cognitive model suggests a functional dissociation between motor imagery and overt action, in contrast to the Functional Equivalence view of common processes between the two behaviours. According to the Motor-Cognitive model, motor imagery differs from overt action primarily through the use of executive resources to monitor and elaborate a motor image during execution, which can result in a lack of correspondence between motor imagery and its overt action counterpart. The present study examined the importance of executive resources in motor imagery by using TMS to impair the function of the dorsolateral prefrontal cortex while measuring the time to complete imagined versus overt actions. In two experiments, TMS over the dorsolateral prefrontal cortex slowed motor imagery but did not affect overt actions. TMS over the same region also interfered with performance of a mental calculation task, though it did not reliably affect less demanding cognitive tasks also thought to rely on executive functions. Taken together, these results were consistent with the Motor-Cognitive model but not with the idea of functional equivalence. The implications of these results for the theoretical understanding of motor imagery, and potential applications of the Motor-Cognitive model to the use of motor imagery in training and rehabilitation, are discussed.

Mapping relational links between motor imagery, action observation, action-related language, and action execution

Actions can be physically executed, observed, imagined, or simply thought about. Unifying mental processes, such as simulation, emulation, or predictive processing, are thought to underlie different action types, whether they are mental states, as in the case of motor imagery and action observation, or involve physical execution. While overlapping brain activity is typically observed across different actions which indicates commonalities, research interest is also concerned with investigating the distinct functional components of these action types. Unfortunately, untangling subtleties associated with the neurocognitive bases of different action types is a complex endeavour due to the high dimensional nature of their neural substrate (e.g., any action process is likely to activate multiple brain regions thereby having multiple dimensions to consider when comparing across them). This has impeded progress in action-related theorising and application. The present study addresses this challenge by using the novel approach of multidimensional modeling to reduce the high-dimensional neural substrate of four action-related behaviours (motor imagery, action observation, action-related language, and action execution), find the least number of dimensions that distinguish or relate these action types, and characterise their neurocognitive relational links. Data for the model comprised brain activations for action types from whole-brain analyses reported in 53 published articles. Eighty-two dimensions (i.e., 82 brain regions) for the action types were reduced to a three-dimensional model, that mapped action types in ordination space where the greater the distance between the action types, the more dissimilar they are. A series of one-way ANOVAs and post-hoc comparisons performed on the mean coordinates for each action type in the model showed that across all action types, action execution and concurrent action observation (AO)-motor imagery (MI) were most neurocognitively similar, while action execution and AO were most dissimilar. Most action types were similar on at least one neurocognitive dimension, the exception to this being action-related language. The import of the findings are discussed in terms of future research and implications for application.

Motor Imagery as a Key Factor for Healthy Ageing: A Review of New Insights and Techniques

Motor imagery (MI) describes a dynamic cognitive process where a movement is mentally simulated without taking place and holds potential as a means of stimulating motor learning and regaining motor skills. There is growing evidence that imagined and executed actions have common neural circuitry. Since MI counteracts cognitive and motor decline, a growing interest in MI-based mental exercise for older individuals has emerged. Here we review the last decade's scientific literature on age-related changes in MI skills. Heterogeneity in the experimental protocols, as well as the use of populations with unrepresentative age, is making it challenging to draw unambiguous conclusions about MI skills preservation. Self-report and behavioural tasks have shown that some MI components are preserved, while others are impaired. Evidence from neuroimaging studies revealed that, during MI tasks, older individuals hyperactivate their sensorimotor and attentional networks. Some studies have argued that this represents a compensatory mechanism, others claim that this is a sign of cognitive decline. However, further studies are needed to establish whether MI could be used as a promotion factor to improve cognitive functioning and well-being in older people.

When action prediction grows old: An fMRI study

Predicting the unfolding of others' actions (action prediction) is crucial for successfully navigating the social world and interacting efficiently. Age-related changes in this domain have remained largely unexplored, especially for predictions regarding simple gestures and independent of contextual information or motor expertise. Here, we evaluated whether healthy aging impacts the neurophysiological processes recruited to anticipate, from the observation of implied-motion postures, the correct conclusion of simple grasping and pointing actions. A color-discrimination task served as a control condition to assess the specificity of the age-related effects. Older adults showed reduced efficiency in performance that was yet not specific to the action prediction task. Nevertheless, fMRI results revealed task-specific age-related differences: while both groups showed stronger recruitment of the lateral occipito-temporal cortex bilaterally during the action prediction than the control task, the younger participants additionally showed a higher bilateral engagement of parietal regions. Importantly, in both groups, the recruitment of visuo-motor processes in the right posterior parietal cortex was a predictor of good performance. These results support the hypothesis of decreased involvement of sensorimotor processes in cognitive tasks when processing action- and body-related stimuli in healthy aging. These results have implications for social interaction, which requires the fast reading of others' gestures.

Effects of age and gender on neural correlates of emotion imagery

Mental imagery is part of people's own internal processing and plays an important role in everyday life, cognition and pathology. The neural network supporting mental imagery is bottom‐up modulated by the imagery content. Here, we examined the complex associations of gender and age with the neural mechanisms underlying emotion imagery. We assessed the brain circuits involved in emotion mental imagery (vs. action imagery), controlled by a letter detection task on the same stimuli, chosen to ensure attention to the stimuli and to discourage imagery, in 91 men and women aged 14–65 years using fMRI. In women, compared with men, emotion imagery significantly increased activation within the right putamen, which is involved in emotional processing. Increasing age, significantly decreased mental imagery‐related activation in the left insula and cingulate cortex, areas involved in awareness of ones' internal states, and it significantly decreased emotion verbs‐related activation in the left putamen, which is part of the limbic system. This finding suggests a top‐down mechanism by which gender and age, in interaction with bottom‐up effect of type of stimulus, or directly, can modulate the brain mechanisms underlying mental imagery.

How the motor system copes with aging: a quantitative meta-analysis of the effect of aging on motor function control

Motor cognitive functions and their neurophysiology evolve and degrade along the lifespan in a dramatic fashion. Current models of how the brain adapts to aging remain inspired primarily by studies on memory or language processes. Yet, aging is strongly associated with reduced motor independence and the associated degraded interaction with the environment: accordingly, any neurocognitive model of aging not considering the motor system is, ipso facto, incomplete. Here we present a meta-analysis of forty functional brain-imaging studies to address aging effects on motor control. Our results indicate that motor control is associated with aging-related changes in brain activity, involving not only motoric brain regions but also posterior areas such as the occipito-temporal cortex. Notably, some of these differences depend on the specific nature of the motor task and the level of performance achieved by the participants. These findings support neurocognitive models of aging that make fewer anatomical assumptions while also considering tasks-dependent and performance-dependent manifestations. Besides the theoretical implications, the present data also provide additional information for the motor rehabilitation domain, indicating that motor control is a more complex phenomenon than previously understood, to which separate cognitive operations can contribute and decrease in different ways with aging.

Many aspects of neuronal control degrade with ageing, including motor control. Using a meta-analysis of functional MRI images, it is made apparent that the ageing brain relies more on visual strategies than sensory stimuli to maintain motor function.

Self-perception in anorexia nervosa: When the body becomes an object

OBJECTIVE

Women with anorexia nervosa (AN) act as if they have a larger body, as evidenced in obstacle avoidance tasks, where an allocentric perspective is adopted. This alteration emerges not only when they perform, but also when they imagine movements. However, no previous study has investigated own body centered tasks. As such, in this study we aim at documenting if women with AN show an altered behaviour also when the task requires a first-person perspective.

METHOD

We explored the performance of eleven woman affected by AN compared to eighteen matched controls, in two motor imagery tasks based on a self-frame of reference, the Hand Laterality Task and the Mental Motor Chronometry Task. Moreover, two control tasks relative to visual imagery were administered.

RESULTS

In the Hand Laterality Task, affected participants did not adopt a motor strategy to judge hands laterality (i.e. no biomechanical constraints effect). Crucially, they also showed an altered behavior in the control task. Similarly, they did not show the expected isochrony in the Mental Motor Chronometry Task, when actions pertained the left (but not the right) hand, in absence of any difference in the control task.

CONCLUSIONS

Our findings reveal altered imagery processes in AN. Specifically, affected participants adopt a third-person, rather than a first-person perspective, even when the task requires to imagine their own body in an internal frame of reference. In other words, participants with AN objectify body stimuli. Different mechanisms (i.e., checking behaviour; mirror self-reflection; altered multisensory integration) can explain such an altered imagery in AN.

Where in the Brain is "the Other's" Hand? Mapping Dysfunctional Neural Networks in Somatoparaphrenia

Somatoparaphrenia refers to the delusional belief, typically observed in right brain-damaged patients, that the contralesional limbs belong to someone else. Here, we aimed to uncover the neural activity associated with this productive, i.e. confabulatory, component in a patient, S.P.P., with a large right-sided lesion of both cortical and subcortical gray and white matter. He claimed that his left paralyzed hand belonged to his mother. In a block-design functional magnetic resonance (fMRI) experiment, S.P.P. imagined that the mother would move her (i.e. his left) hand (condition "mother"). Subtraction of the activity elicited by control conditions (imagery of self-generated movement of either left or right hand) from that in the "mother" condition resulted in the focal activation of the pars opercularis of the right inferior frontal gyrus (rIFG). In a separate, resting-state fMRI experiment with S.P.P. and 21 healthy controls, we examined the functional connectivity of the rIFG and the affected hand somatosensory network to the rest of the brain. We found a negative correlation between the activity in the rIFG and that of Broca area and the temporo-parietal junction in the left hemisphere. Furthermore, the affected hand somatosensory network was disconnected from the left secondary somatosensory cortex. Our results link the productive component of somatoparaphrenia to the activity of crucial hubs for integrating the multimodal signals of the affected hand. Furthermore, they provide the first direct evidence supporting the "left narrator model", proposed by Halligan et al. (1995), according to which the confabulations of somatoparaphrenia are due to a disconnection of left hemisphere language areas from right hemisphere parieto-temporal cortex.

Synthesizing the effects of mental simulation on behavior change: Systematic review and multilevel meta-analysis

Mental simulation of future scenarios is hypothesized to affect future behavior, but a large and inconsistent literature means it is unclear whether, and under what conditions, mental simulation can change people's behavior. A meta-analysis was conducted to synthesize the effects of mental simulation on behavior and examine under what conditions mental simulation works best. An inclusive systematic database search identified 123 (N = 5,685) effect sizes comparing mental simulation to a control group. After applying a multilevel random effects model, a statistically-reliable positive effect of Hedges' g = 0.49, 95% CI [0.37; 0.62] was found, which was significantly different than zero. Using a taxonomy to identify different subtypes of mental simulation (along two dimensions, class [process, performance, outcome] and purpose [whether an inferior, standard, superior version of that behavior is simulated]), it was found that superior simulations garnered more reliable beneficial effects than inferior simulations. These findings have implications for integrating theories of how mental simulations change behavior, how mental simulations are classified, and may help guide professionals seeking evidence-based and cost-effective methods of changing behavior.

Increased links between language and motor areas: A proof-of-concept study on resting-state functional connectivity following Personalized Observation, Execution and Mental imagery therapy in chronic aphasia

A tight coupling of language and motor processes has been established, which is consistent with embodied cognition theory. However, very few therapies have been designed to exploit the synergy between motor and language processes to help rehabilitate people with aphasia (PWA). Moreover, the underlying mechanisms supporting the efficacy of such approaches remain unknown. Previous work in our laboratory has demonstrated that personalized observation, execution, and mental imagery therapy (POEM)-a new therapy using three sensorimotor strategies to trigger action verb naming-leads to significant improvements in verb retrieval in PWA. Moreover, these improvements were supported by significant activations in language and sensorimotor processing areas, which further reinforce the role of both processes in language recovery (Durand et al., 2018). The present study investigates resting state functional connectivity (rsFC) changes following POEM in a pre-/post-POEM therapy design. A whole brain network functional connectivity approach was used to assess and describe changes in rsFC in a group of four PWA, who were matched and compared with four healthy controls (HC). Results showed increased rsFC in PWA within and between visuo-motor and language areas (right cuneal cortex-left supracalcarin (SCC) cortex/right precentral gyrus (PreCG)-left lingual gyrus (LG)) and between areas involved in action processing (right anterior parahippocampal gyrus (aPaHC)-left superior parietal lobule (SPL). In comparison to HC, the PWA group showed increased rsFC between the right inferior frontal gyrus (IFG) and left thalamus, which are areas involved in lexico-semantic processing. This proof-of-concept study suggests that the sensorimotor and language strategies used in POEM may induce modifications in large-scale networks, probably derived from the integration of visual and sensorimotor systems to sustain action naming, which is consistent with the embodied cognition theory.

Talking with hands: body representation in British Sign Language users

Body representation (BR) refers to the mental representation of motor, sensory, emotional and semantic information about the physical body. This cognitive representation is used in our everyday life, continuously, even though most of the time we do not appreciate it consciously. In some cases, BR is vital to be able to communicate. A crucial feature of signed languages (SLs), for instance, is that body parts such as hands are used to communicate. Nevertheless, little is known about BR in SL: is the communicative function of the body overwriting the physical constraints? Here, we explored this question by comparing twelve British Sign Language (BSL) learners to seventeen tango dancers (body expertise but not for communication) and fourteen control subjects (no special body expertise). We administered the Body Esteem Scale (BES), the Hand Laterality Task (HLT) and the Mental Motor Chronometry (MMC). To control for visual imagery, we administered ad hoc control tasks. We did not identify parameters able to differentiate between SL users and the other groups, whereas the more implicit parameters distinguished clearly tango dancers from controls. Importantly, neither tasks on visual imagery nor the BES revealed differences. Our findings offer initial evidence that linguistic use of the body not necessarily influences the cognitive components we explored of body representation.

Eyes wide shut: How visual cues affect brain patterns of simulated gait

In the last 20 years, motor imagery (MI) has been extensively used to train motor abilities in sport and in rehabilitation. However, MI procedures are not all alike as much as their potential beneficiaries. Here we assessed whether the addition of visual cues could make MI performance more comparable with explicit motor performance in gait tasks. With fMRI we also explored the neural correlates of these experimental manipulations. We did this in elderly subjects who are known to rely less on kinesthetic information while favoring visual strategies during motor performance. Contrary to expectations, we found that the temporal coupling between execution and imagery times, an index of the quality of MI, was less precise when participants were allowed to visually explore the environment. While the brain activation patterns of the gait motor circuits were very similar in both an open‐eyed and eye‐shut virtual walking MI task, these differed for a vast temporo‐occipito‐parietal additional activation for open‐eyed MI. Crucially, the higher was the activity in this posterior network, the less accurate was the MI performance with eyes open at a clinical test of gait. We conclude that both visually‐cued and internally‐cued MI are associated with the neurofunctional activation of a gait specific motor system. The less precise behavioral coupling between imagined and executed gait while keeping eyes open may be attributed to the processing load implied in visual monitoring and scanning of the environment. The implications of these observations for rehabilitation of gait with MI are discussed.

Implicit Motor Imagery and the Lateral Occipitotemporal Cortex: Hints for Tailoring Non-Invasive Brain Stimulation

Background: Recent evidence has converged in showing that the lateral occipitotemporal cortex is over-recruited during implicit motor imagery in elderly and in patients with neurodegenerative disorders, such as Parkinson’s disease. These data suggest that when automatically imaging movements, individuals exploit neural resources in the visual areas to compensate for the decline in activating motor representations. Thus, the occipitotemporal cortex could represent a cortical target of non-invasive brain stimulation combined with cognitive training to enhance motor imagery performance. Here, we aimed at shedding light on the role of the left and right lateral occipitotemporal cortex in implicit motor imagery. Methods: We applied online, high-frequency, repetitive transcranial magnetic stimulation (rTMS) over the left and right lateral occipitotemporal cortex while healthy right-handers judged the laterality of hand images. Results: With respect to the sham condition, left hemisphere stimulation specifically reduced accuracy in judging the laterality of right-hand images. Instead, the hallmark of motor simulation, i.e., the biomechanical effect, was never influenced by rTMS. Conclusions: The lateral occipitotemporal cortex seems to be involved in mental representation of the dominant hand, at least in right-handers, but not in reactivating sensorimotor information during simulation. These findings provide useful hints for developing combined brain stimulation and behavioural trainings to improve motor imagery.

Motor neuroplasticity: A MEG-fMRI study of motor imagery and execution in healthy ageing

Age-related decline in motor function is associated with over-activation of the sensorimotor circuitry. Using a multimodal MEG-fMRI paradigm, we investigated whether this neural over-recruitment in old age would be related to changes in movement-related beta desynchronization (MRBD), a correlate of the inhibitory neurotransmitter γ-aminobutyric acid (GABA), and whether it would characterize compensatory recruitment or a reduction in neural specialization (dedifferentiation). We used MEG to assess age-related changes in beta band oscillations in primary motor cortices, fMRI to localize age-related changes in brain activity, and the Finger Configuration Task to measure task performance during overt and covert motor processing: motor execution (ME) and motor imagery (MI). The results are threefold: first, showing age-related neuroplasticity during ME of older adults, compared to young adults, as evidenced by increased MRBD in motor cortices and over-recruitment of sensorimotor areas; second, showing similar age-related neuroplastic changes during MI; and finally, showing signs of dedifferentiation during ME in older adults whose performance negatively correlated with connectivity to bilateral primary motor cortex. Together, these findings demonstrate that elevated MRBD levels, reflecting greater GABAergic inhibitory activity, and over-activation of the sensorimotor network during ME may not be compensatory, but rather might reflect an age-related decline of the quality of the underlying neural signal.

How the effects of actions become our own

Every day, we do things that cause effects in the outside world with little doubt about who caused what. To some, this sense of agency derives from a post hoc reconstruction of a likely causal relationship between an event and our preceding movements; others propose that the sense of agency originates from prospective comparisons of motor programs and their effects. Using functional magnetic resonance imaging, we found that the sense of agency is associated with a brain network including the pre-supplementary motor area (SMA) and dorsal parietal cortex. Transcranial magnetic stimulation affected the sense of agency only when delivered over the pre-SMA and specifically when time-locked to action planning, rather than when the physical consequences of the actions appeared. These findings make a prospective theory of the sense of agency more likely.

Study of the Functional Brain Connectivity and Lower-Limb Motor Imagery Performance After Transcranial Direct Current Stimulation

The use of transcranial direct current stimulation (tDCS) has been related to the improvement of motor and learning tasks. The current research studies the effects of an asymmetric tDCS setup over brain connectivity, when the subject is performing a motor imagery (MI) task during five consecutive days. A brain–computer interface (BCI) based on electroencephalography is simulated in offline analysis to study the effect that tDCS has over different electrode configurations for the BCI. This way, the BCI performance is used as a validation index of the effect of the tDCS setup by the analysis of the classifier accuracy of the experimental sessions. In addition, the relationship between the brain connectivity and the BCI accuracy performance is analyzed. Results indicate that tDCS group, in comparison to the placebo sham group, shows a higher significant number of connectivity interactions in the motor electrodes during MI tasks and an increasing BCI accuracy over the days. However, the asymmetric tDCS setup does not improve the BCI performance of the electrodes in the intended hemisphere.

The Role of Moderating Variables on BOLD fMRI Response During Semantic Verbal Fluency and Finger Tapping in Active and Educated Healthy Seniors

Semantic verbal fluency is among the most employed tasks in cognitive aging research and substantial work is devoted to understanding the underlying mechanisms behind age-related differences at the neural and behavioral levels. The present investigation aimed to evaluate the role of moderating variables, such as age, sex, MMSE, and proxies of cognitive reserve (CR) on the hemodynamic response evoked by semantic verbal fluency in healthy young and healthy older adults. So far, no study has been conducted to this end. To elucidate the exclusive effect of the mentioned variables on brain activation during semantic fluency, finger tapping was included as a control task. Results showed that disregarding adjustments for age, older adults displayed important parietal activations during semantic fluency as well as during finger-tapping. Specifically, the anterior intra-parietal sulcus (IPS) and left inferior parietal lobule (IPL) were areas activated in both tasks in the older group. Younger adults, only displayed parietal activations related to age and sex when these demographics were employed as predictors. Concerning proxies of CR in semantic fluency, the only vocabulary was an important moderator in both age groups. Higher vocabulary scores were associated with lesser activation in occipital areas. Education did not show significant correlations with brain activity during semantic fluency in any of the groups. However, both CR proxies were significantly correlated to brain activations of older adults during finger tapping. Specifically, vocabulary was associated with frontal regions, while education correlated with parietal lobe and cingulate gyrus. Finally, the effects of MMSE were mostly observed on brain activation of older adults in both tasks. These findings demonstrate that the effects of moderating variables on shaping brain activation are intricate and not exclusive of complex verbal tasks. Thus, before adjusting for “nuisance variables,” their importance needs to be established. This is especially true for samples including older adults for whom a motor task may be a demanding operation due to normal age-related processes of dedifferentiation.

How aging affects the premotor control of lower limb movements in simulated gait

Gait control becomes more demanding in healthy older adults, yet what cognitive or motor process leads to this age-related change is unknown. The present study aimed to investigate whether it might depend on specific decay in the quality of gait motor representation and/or a more general reduction in the efficiency of lower limb motor control. Younger and older healthy participants performed in fMRI a virtual walking paradigm that combines motor imagery (MI) of walking and standing on the spot with the presence (Dynamic Motor Imagery condition, DMI) or absence (pure MI condition) of overtly executed ankle dorsiflexion. Gait imagery was aided by the concomitant observation of moving videos simulating a stroll in the park from a first-person perspective. Behaviorally, older participants showed no sign of evident depletion in the quality of gait motor representations, and absence of between-group differences in the neural correlates of MI. However, while younger participants showed increased frontoparietal activity during DMI, older participants displayed stronger activation of premotor areas when controlling the pure execution of ankle dorsiflexion, regardless of the imagery task. These data suggest that reduced automaticity of lower limb motor control in healthy older subjects leads to the recruitment of additional premotor resources even in the absence of basic gait functional disabilities.

Imagery Ability and Imagery Perspective Preference: A Study of Their Relationship and Age- and Gender-Related Changes

This study examined if imagery ability (i.e., vividness and temporal congruence between imagined and executed knee extensions) and imagery perspective preference were affected by ageing and gender. Ninety-four participants, 31 young, 43 intermediate, and 20 older adults completed the Vividness of Movement Imagery Questionnaire-2 and a knee extension temporal congruence test to reflect on their imagery ability and an imagery perspective preference test. Male participants had a better imagery ability than the female participants (F (4, 85) = 2.84, p = .029, η² = .118). However, significant age-related changes in imagery ability were not found in the three age groups. Change in imagery perspective preference with a trend towards an external imagery perspective was observed with ageing (F (3, 89) = 3.16, p = .028, η² = .096) but not between male and female. The results suggest that imagery ability may be preserved with ageing. As individuals age, their preference for using an imagery perspective shifts from a more internal to a more external perspective. This understanding is important when designing future imagery research and real-life application or clinical intervention.

Mental representation of the body in action in Parkinson's disease

Mixed findings characterize studies in Parkinson's disease (PD): some studies indicate a relationship between physical impairments and the ability to mentally represent the body, while others suggest spared abilities for this cognitive function. To clarify the matter, in the present study we explored the mental representations of the body in action in the same PD patients, taking also into account lateralization of symptoms and visual imagery skills. 10 PD patients with left- (lPD), 10 with right (rPD) lateralized symptoms (lPD), and 20 matched healthy controls have been recruited for the study. All patients were screened for neuropsychological impairments. To explore a more implicit component we used the hand laterality task (HLT), while the mental motor chronometry (MMC) was used to explore a more explicit one. Two control tasks, with objects instead of body parts, were administered to control for visual imagery skills. In the HLT, we detected the effects of biomechanical constraints effects in both controls and PD patients. In the latter group, importantly, this was true independently from lateralization of symptoms. In the MMC, we found the expected positive correlation between executed and imagined movements for both hands in controls only, while all PD patients, again independently form lateralization, only showed this effect for the left hand. In terms of visual imagery, only rPD patients differed from controls when asked to implicitly rotate letters, and in terms of accuracy only. However, this difference is explained by executive functions measured through the neuropsychological assessment rather than by a "pure" visual imagery impairment. In summary, our findings suggest that two different aspects of the mental representations of the body in action, one more implicit and the other more explicit, can be differently affected by PD. These impairments are unlikely explained by a basic visual imagery deficit. When present, impairments concern a higher dimension, related to motor functions and awareness, and not driven by sensory impairments, as shown by the independence of effects from physical laterality of symptoms.

Thumbs up: Imagined hand movements counteract the adverse effects of post-surgical hand immobilization. Clinical, behavioral, and fMRI longitudinal observations

Motor imagery (M.I.) training has been widely used to enhance motor behavior. To characterize the neural foundations of its rehabilitative effects in a pathological population we studied twenty-two patients with rhizarthrosis, a chronic degenerative articular disease in which thumb-to-fingers opposition becomes difficult due to increasing pain while the brain is typically intact. Before and after surgery, patients underwent behavioral tests to measure pain and motor performance and fMRI measurements of brain motor activity.

After surgery, the affected hand was immobilized, and patients were enrolled in a M.I. training. The sample was split in those who had a high compliance with the program of scheduled exercises (T+, average compliance: 84%) and those with low compliance (T−, average compliance: 20%; cut-off point: 55%). We found that more intense M.I. training counteracts the adverse effects of immobilization reducing pain and expediting motor recovery. fMRI data from the post-surgery session showed that T+ patients had decreased brain activation in the premotor cortex and the supplementary motor area (SMA); meanwhile, for the same movements, the T− patients exhibited a reversed pattern. Furthermore, in the post-surgery fMRI session, pain intensity was correlated with activity in the ipsilateral precentral gyrus and, notably, in the insular cortex, a node of the pain matrix.

These findings indicate that the motor simulations of M.I. have a facilitative effect on recovery by cortical plasticity mechanisms and optimization of motor control, thereby establishing the rationale for incorporating the systematic use of M.I. into standard rehabilitation for the management of post-immobilization syndromes characteristic of hand surgery.

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Motor imagery training counteracts the effects of post-surgical hand immobilization.

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It also reduces pain and expedites motor recovery after immobilization.

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These effects were accompanied by significant fMRI signs of brain plasticity.

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The clinical-fMRI evidence advocates for the use of motor imagery in rehabilitation.

Disruption of motor imagery performance following inhibition of the left inferior parietal lobe

The left inferior parietal lobe (IPL), a brain region localized to the ventro-dorsal stream, is known to be critical to motor imagery (MI) performance. Yet its specific role in processes underlying MI, namely the generation, maintenance, manipulation, and controllability of motor images, is conflicting in the literature. To determine the specific role of the left IPL in MI, the current study sought to examine the effect inhibition of the left IPL has on performance on two disparate measures thought to probe different MI processes within the same participants. Participants (N = 31) completed the hand laterality judgment task (HLJT), employed to probe processes related to manipulation and controllability, and mental chronometry, employed to probe processes related to generation and maintenance, after receiving either inhibitory transcranial magnetic stimulation to the left IPL (Active-TMS group), or with the coil angled away from the scalp (Sham group). Impaired performance on the HLJT was observed following active TMS relative to sham. Similar mental chronometry performance resulted regardless of left IPL inhibition. In showing that inhibition of the left IPL selectively disrupted performance on the HLJT but not mental chronometry, our findings indicate that the left IPL is specifically involved in image manipulation and controllability during MI. Ultimately, the current study extends our understanding of the role of the left IPL in MI.

Improving Real-Time Lower Limb Motor Imagery Detection Using tDCS and an Exoskeleton

The aim of this work was to test if a novel transcranial direct current stimulation (tDCS) montage boosts the accuracy of lower limb motor imagery (MI) detection by using a real-time brain-machine interface (BMI) based on electroencephalographic (EEG) signals. The tDCS montage designed was composed of two anodes and one cathode: one anode over the right cerebrocerebellum, the other over the motor cortex in Cz, and the cathode over FC2 (using the International 10–10 system). The BMI was designed to detect two MI states: relax and gait MI; and was based on finding the power at the frequency which attained the maximum power difference between the two mental states at each selected EEG electrode. Two different single-blind experiments were conducted, E1 and a pilot test E2. E1 was based on visual cues and feedback and E2 was based on auditory cues and a lower limb exoskeleton as feedback. Twelve subjects participated in E1, while four did so in E2. For both experiments, subjects were separated into two equally-sized groups: sham and active tDCS. The active tDCS group achieved 12.6 and 8.2% higher detection accuracy than the sham group in E1 and E2, respectively, reaching 65 and 81.6% mean detection accuracy in each experiment. The limited results suggest that the exoskeleton (E2) enhanced the detection of the MI tasks with respect to the visual feedback (E1), increasing the accuracy obtained in 16.7 and 21.2% for the active tDCS and sham groups, respectively. Thus, the small pilot study E2 indicates that using an exoskeleton in real-time has the potential of improving the rehabilitation process of cerebrovascular accident (CVA) patients, but larger studies are needed in order to further confirm this claim.

Dance Training Shapes Action Perception and Its Neural Implementation within the Young and Older Adult Brain

How we perceive others in action is shaped by our prior experience. Many factors influence brain responses when observing others in action, including training in a particular physical skill, such as sport or dance, and also general development and aging processes. Here, we investigate how learning a complex motor skill shapes neural and behavioural responses among a dance-naïve sample of 20 young and 19 older adults. Across four days, participants physically rehearsed one set of dance sequences, observed a second set, and a third set remained untrained. Functional MRI was obtained prior to and immediately following training. Participants' behavioural performance on motor and visual tasks improved across the training period, with younger adults showing steeper performance gains than older adults. At the brain level, both age groups demonstrated decreased sensorimotor cortical engagement after physical training, with younger adults showing more pronounced decreases in inferior parietal activity compared to older adults. Neural decoding results demonstrate that among both age groups, visual and motor regions contain experience-specific representations of new motor learning. By combining behavioural measures of performance with univariate and multivariate measures of brain activity, we can start to build a more complete picture of age-related changes in experience-dependent plasticity.

Non-physical approaches to counteract age-related functional deterioration: Applications for rehabilitation and neural mechanisms

Normal and pathological ageing are associated with several motor impairments that reduce quality of life and represent a general challenge for public healthcare systems. Consequently, over the past decades, many scientists and physiotherapists dedicated their research to the development and improvement of safe and costless methods to counteract the progressive decline of motor functions with age. The urgency of finding new and easy to implement methods is even more paramount in case of acute pathologies (e.g. stroke or hip surgery). The frailty of older population makes it difficult or even impossible to use traditional physical therapy at an early stage after the occurrence of a pathology. To that purpose, non-physical approaches such as cognitive training (e.g. memory, attention training) and mental techniques (e.g. motor imagery) have grown in popularity for the elderly. Such methods, involving individual and/or group exercises, have shown particular effects on increasing or maintaining cognitive functions, as well as physical performances. Improving the motor function (especially in older age) requires an improvement of motor execution, i.e. the pathway from the brain motor areas to the muscle but also higher cognitive control. The present work reviews different non-physical interventions that can be used as a complementary approach by asymptomatic or frail older adults, and the effects thereof on functional performance. The use of cognitive training or motor imagery protocols is recommended when physical practice is limited or not possible. Finally, insights into the underlying neurophysiological mechanisms are proposed.

Walking, Gross Motor Development, and Brain Functional Connectivity in Infants and Toddlers

Infant gross motor development is vital to adaptive function and predictive of both cognitive outcomes and neurodevelopmental disorders. However, little is known about neural systems underlying the emergence of walking and general gross motor abilities. Using resting state fcMRI, we identified functional brain networks associated with walking and gross motor scores in a mixed cross-sectional and longitudinal cohort of infants at high and low risk for autism spectrum disorder, who represent a dimensionally distributed range of motor function. At age 12 months, functional connectivity of motor and default mode networks was correlated with walking, whereas dorsal attention and posterior cingulo-opercular networks were implicated at age 24 months. Analyses of general gross motor function also revealed involvement of motor and default mode networks at 12 and 24 months, with dorsal attention, cingulo-opercular, frontoparietal, and subcortical networks additionally implicated at 24 months. These findings suggest that changes in network-level brain-behavior relationships underlie the emergence and consolidation of walking and gross motor abilities in the toddler period. This initial description of network substrates of early gross motor development may inform hypotheses regarding neural systems contributing to typical and atypical motor outcomes, as well as neurodevelopmental disorders associated with motor dysfunction.

Motor imagery training: Kinesthetic imagery strategy and inferior parietal fMRI activation

Motor imagery (MI) is the mental simulation of action frequently used by professionals in different fields. However, with respect to performance, well-controlled functional imaging studies on MI training are sparse. We investigated changes in fMRI representation going along with performance changes of a finger sequence (error and velocity) after MI training in 48 healthy young volunteers. Before training, we tested the vividness of kinesthetic and visual imagery. During tests, participants were instructed to move or to imagine moving the fingers of the right hand in a specific order. During MI training, participants repeatedly imagined the sequence for 15 min. Imaging analysis was performed using a full-factorial design to assess brain changes due to imagery training. We also used regression analyses to identify those who profited from training (performance outcome and gain) with initial imagery scores (vividness) and fMRI activation magnitude during MI at pre-test (MI_pre ). After training, error rate decreased and velocity increased. We combined both parameters into a common performance index. FMRI activation in the left inferior parietal lobe (IPL) was associated with MI and increased over time. In addition, fMRI activation in the right IPL during MI_pre was associated with high initial kinesthetic vividness. High kinesthetic imagery vividness predicted a high performance after training. In contrast, occipital activation, associated with visual imagery strategies, showed a negative predictive value for performance. Our data echo the importance of high kinesthetic vividness for MI training outcome and consider IPL as a key area during MI and through MI training.

Age-related functional brain changes in FMR1 premutation carriers

The FMR1 premutation confers a 40–60% risk for males of developing a neurodegenerative disease called the Fragile X-associated Tremor Ataxia Syndrome (FXTAS). FXTAS is a late-onset disease that primarily involves progressive symptoms of tremor and ataxia, as well as cognitive decline that can develop into dementia in some patients. At present, it is not clear whether changes to brain function are detectable in motor regions prior to the onset of frank symptomatology. The present study therefore aimed to utilize an fMRI motor task for the first time in an asymptomatic premutation population.

Premutation carriers without a diagnosis of FXTAS (n = 17) and a group of healthy male controls (n = 17), with an age range of 24–68 years old, were recruited for this cross-sectional study. This study utilized neuroimaging, molecular and clinical measurements, employing an fMRI finger-tapping task with a block design consisting of sequential finger-tapping, random finger-tapping and rest conditions. The imaging analysis contrasted the sequential and random conditions to investigate activation changes in response to a change in task demand. Additionally, measurements were obtained of participant tremor, co-ordination and balance using the CATSYS-2000 system and measures of FMR1 mRNA were quantified from peripheral blood samples using quantitative real-time PCR methodology.

Premutation carriers demonstrated significantly less cerebellar activation than controls during sequential versus random finger tapping (FWE_corr < 0.001). In addition, there was a significant age by group interaction in the hippocampus, inferior parietal cortex and temporal cortex originating from a more negative relationship between brain activation and age in the carrier group compared to the controls (FWE_corr < 0.001).

Here, we present for the first time functional imaging-based evidence for early movement-related neurodegeneration in Fragile X premutation carriers. These changes pre-exist the diagnosis of FXTAS and are greatest in older carriers suggesting that they may be indicative of FXTAS vulnerability.

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The authors present a cross-sectional fMRI study in male carriers of the FMR1 premutation

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Carriers show decreased BOLD activation at the cerebellum in response to change in task demand in a finger-tapping task

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Carriers exhibit a group x age interaction of BOLD response in the temporoparietal area

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These changes pre-exist the diagnosis of the Fragile X-associated Tremor/Ataxia Syndrome (FXTAS)

How many deficits in the same dyslexic brains? A behavioural and fMRI assessment of comorbidity in adult dyslexics

Dyslexia can have different manifestations: this has motivated different theories on its nature, on its underlying brain bases and enduring controversies on how to best treat it. The relative weight of the different manifestations has never been evaluated using both behavioural and fMRI measures, a challenge taken here to assess the major systems called into play in dyslexia by different theories. We found that adult well-compensated dyslexics were systematically impaired only in reading and in visuo-phonological tasks, while deficits for other systems (e.g., motor/cerebellar, visual magnocellular/motion perception) were only very occasional. In line with these findings, fMRI showed a reliable hypoactivation only for the task of reading, in the left occipito-temporal cortex (l-OTC). The l-OTC, normally a crossroad between the reading system and other systems, did not show the same level of intersection in dyslexics; yet, it was not totally silent because it responded, in segregated parts, during auditory phonological and visual motion perception tasks. This minimal behavioural and functional anatomical comorbidity demonstrates that a specific deficit of reading is the best description for developmental dyslexia, at least for adult well-compensated cases, with clear implications for rehabilitation strategies. The reduced intersection of multiple systems in the l-OTC suggests that dyslexics suffer from a coarser connectivity, leading to disconnection between the multiple domains that normally interact during reading.

Modulating hemispheric lateralization by brain stimulation yields gain in mental and physical activity

Imagery plays an important role in our life. Motor imagery is the mental simulation of a motor act without overt motor output. Previous studies have documented the effect of motor imagery practice. However, its translational potential for patients as well as for athletes, musicians and other groups, depends largely on the transfer from mental practice to overt physical performance. We used bilateral transcranial direct current stimulation (tDCS) over sensorimotor areas to modulate neural lateralization patterns induced by unilateral mental motor imagery and the performance of a physical motor task. Twenty-six healthy older adults participated (mean age = 67.1 years) in a double-blind cross-over sham-controlled study. We found stimulation-related changes at the neural and behavioural level, which were polarity-dependent. Specifically, for the hand contralateral to the anode, electroencephalographic activity induced by motor imagery was more lateralized and motor performance improved. In contrast, for the hand contralateral to the cathode, hemispheric lateralization was reduced. The stimulation-related increase and decrease in neural lateralization were negatively related. Further, the degree of stimulation-related change in neural lateralization correlated with the stimulation-related change on behavioural level. These convergent neurophysiological and behavioural effects underline the potential of tDCS to improve mental and physical motor performance.

Mental steps: Differential activation of internal pacemakers in motor imagery and in mental imitation of gait

Gait imagery and gait observation can boost the recovery of locomotion dysfunctions; yet, a neurologically justified rationale for their clinical application is lacking as much as a direct comparison of their neural correlates. Using functional magnetic resonance imaging, we measured the neural correlates of explicit motor imagery of gait during observation of in-motion videos shot in a park with a steady cam (Virtual Walking task). In a 2 × 2 factorial design, we assessed the modulatory effect of gait observation and of foot movement execution on the neural correlates of the Virtual Walking task: in half of the trials, the participants were asked to mentally imitate a human model shown while walking along the same route (mental imitation condition); moreover, for half of all the trials, the participants also performed rhythmic ankle dorsiflexion as a proxy for stepping movements. We found that, beyond the areas associated with the execution of lower limb movements (the paracentral lobule, the supplementary motor area, and the cerebellum), gait imagery also recruited dorsal premotor and posterior parietal areas known to contribute to the adaptation of walking patterns to environmental cues. When compared with mental imitation, motor imagery recruited a more extensive network, including a brainstem area compatible with the human mesencephalic locomotor region (MLR). Reduced activation of the MLR in mental imitation indicates that this more visually guided task poses less demand on subcortical structures crucial for internally generated gait patterns. This finding may explain why patients with subcortical degeneration benefit from rehabilitation protocols based on gait observation. Hum Brain Mapp 38:5195-5216, 2017. © 2017 Wiley Periodicals, Inc.

Are Older Adults Less Embodied? A Review of Age Effects through the Lens of Embodied Cognition

Embodied cognition is a theoretical framework which posits that cognitive function is intimately intertwined with the body and physical actions. Although the field of psychology is increasingly accepting embodied cognition as a viable theory, it has rarely been employed in the gerontological literature. However, embodied cognition would appear to have explanatory power for aging research given that older adults typically manifest concurrent physical and mental changes, and that research has indicated a correlative relationship between such changes. The current paper reviews age-related changes in sensory processing, mental representation, and the action-perception relationship, exploring how each can be understood through the lens of embodied cognition. Compared to younger adults, older adults exhibit across all three domains an increased tendency to favor visual processing over bodily factors, leading to the conclusion that older adults are less embodied than young adults. We explore the significance of this finding in light of existing theoretical models of aging and argue that embodied cognition can benefit gerontological research by identifying further factors that can explain the cause of age-related declines.

Mental chronometry and mental rotation abilities in stroke patients with different degrees of sensory deficit

BACKGROUND

Motor imagery is used for treatment of motor deficits after stroke. Clinical observations suggested that motor imagery abilities might be reduced in patients with severe sensory deficits. This study investigated the influence of somatosensory deficits on temporal (mental chronometry, MC) and spatial aspects of motor imagery abilities.

METHODS

Stroke patients (n = 70; <6 months after stroke) were subdivided into 3 groups according to their somatosensory functions. Group 1 (n = 31) had no sensory deficits, group 2 (n = 27) had a mild to moderate sensory impairment and group 3 (n = 12) had severe sensory deficits. Patients and a healthy age-matched control group (n = 23) participated in a mental chronometry task (Box and Block Test, BBT) and a mental rotation task (Hand Identification Test, HIT). MC abilities were expressed as a ratio (motor execution time-motor imagery time/motor execution time).

RESULTS

MC for the affected hand was significantly impaired in group 3 in comparison to stroke patients of group 1 (p = 0.006), group 2 (p = 0.005) and healthy controls (p < 0.001). For the non-affected hand MC was similar across all groups. Stroke patients had a slower BBT motor execution than healthy controls (p < 0.001), and group 1 executed the task faster than group 3 (p = 0.002). The percentage of correct responses in the HIT was similar for all groups.

CONCLUSION

Severe sensory deficits impair mental chronometry abilities but have no impact on mental rotation abilities. Future studies should explore whether the presence of severe sensory deficits in stroke patients reduces the benefit from motor imagery therapy.

Simultaneous EEG-fNIRS reveals how age and feedback affect motor imagery signatures

Stroke frequently results in motor impairment. Motor imagery (MI), the mental practice of movements, has been suggested as a promising complement to other therapeutic approaches facilitating motor rehabilitation. Of particular potential is the combination of MI with neurofeedback (NF). However, MI NF protocols have been largely optimized only in younger healthy adults, although strokes occur more frequently in older adults. The present study examined the influence of age on the neural correlates of MI supported by electroencephalogram (EEG)-based NF and on the neural correlates of motor execution. We adopted a multimodal neuroimaging framework focusing on EEG-derived event-related desynchronization (ERD%) and oxygenated (HbO) and deoxygenated hemoglobin (HbR) concentrations simultaneously acquired using functional near-infrared spectroscopy (fNIRS). ERD%, HbO concentration and HbR concentration were compared between younger (mean age: 24.4 years) and older healthy adults (mean age: 62.6 years). During MI, ERD% and HbR concentration were less lateralized in older adults than in younger adults. The lateralization-by-age interaction was not significant for movement execution. Moreover, EEG-based NF was related to an increase in task-specific activity when compared to the absence of feedback in both older and younger adults. Finally, significant modulation correlations were found between ERD% and hemodynamic measures despite the absence of significant amplitude correlations. Overall, the findings suggest a complex relationship between age and movement-related activity in electrophysiological and hemodynamic measures. Our results emphasize that the age of the actual end-user should be taken into account when designing neurorehabilitation protocols.

Motor and mental training in older people: Transfer, interference, and associated functional neural responses

Learning new motor skills may become more difficult with advanced age. In the present study, we randomized 56 older individuals, including 30 women (mean age 70.6 years), to 6 weeks of motor training, mental (motor imagery) training, or a combination of motor and mental training of a finger tapping sequence. Performance improvements and post-training functional magnetic resonance imaging (fMRI) were used to investigate performance gains and associated underlying neural processes. Motor-only training and a combination of motor and mental training improved performance in the trained task more than mental-only training. The fMRI data showed that motor training was associated with a representation in the premotor cortex and mental training with a representation in the secondary visual cortex. Combining motor and mental training resulted in both premotor and visual cortex representations. During fMRI scanning, reduced performance was observed in the combined motor and mental training group, possibly indicating interference between the two training methods. We concluded that motor and motor imagery training in older individuals is associated with different functional brain responses. Furthermore, adding mental training to motor training did not result in additional performance gains compared to motor-only training and combining training methods may result in interference between representations, reducing performance.

Disembodied Mind: Cortical Changes Following Brainstem Injury in Patients with Locked-in Syndrome

Locked-in syndrome (LIS) following ventral brainstem damage is the most severe form of motor disability. Patients are completely entrapped in an unresponsive body despite consciousness is preserved. Although the main feature of LIS is this extreme motor impairment, minor non-motor dysfunctions such as motor imagery defects and impaired emotional recognition have been reported suggesting an alteration of embodied cognition, defined as the effects that the body and its performances may have on cognitive domains. We investigated the presence of structural cortical changes in LIS, which may account for the reported cognitive dysfunctions. For this aim, magnetic resonance imaging scans were acquired in 11 patients with LIS (6 males and 5 females; mean age: 52.3±5.2SD years; mean time interval from injury to evaluation: 9±1.2SD months) and 44 healthy control subjects matching patients for age, sex and education. Freesurfer software was used to process data and to estimate cortical volumes in LIS patients as compared to healthy subjects. Results showed a selective cortical volume loss in patients involving the superior frontal gyrus, the pars opercularis and the insular cortex in the left hemisphere, and the superior and medium frontal gyrus, the pars opercularis, the insular cortex, and the superior parietal lobule in the right hemisphere. As these structures are typically associated with the mirror neuron system, which represents the neural substrate for embodied simulation processes, our results provide neuroanatomical support for potential disembodiment in LIS.

A Program to Improve Reach Estimation and Reduce Fall Risk in the Elderly

Contemporary research findings indicate that in older persons (typically 64 > years) there are functional decrements in the ability to mentally represent and effectively plan motor actions. Actions, if poorly planned, can result in falling, a major health concern for the elderly. Whereas a number of factors may contribute to falls, over- or underestimation of reach abilities may lead to loss of postural control (balance) and pose a higher risk of falling. Our intent with this paper was to provide: (1) a brief background of the problem, (2) suggest strategies for mental (motor) imagery practice in the context of reach planning, and (3) describe general guidelines and a sample practice format of a training program for clinical use. Mental (motor) imagery practice of reach planning has potential for improving motor performance in reach-related everyday activities and reducing the risk of falls in older persons.

EEG Resting-State Brain Topological Reorganization as a Function of Age

Resting state connectivity has been increasingly studied to investigate the effects of aging on the brain. A reduced organization in the communication between brain areas was demonstrated by combining a variety of different imaging technologies (fMRI, EEG, and MEG) and graph theory. In this paper, we propose a methodology to get new insights into resting state connectivity and its variations with age, by combining advanced techniques of effective connectivity estimation, graph theoretical approach, and classification by SVM method. We analyzed high density EEG signals recorded at rest from 71 healthy subjects (age: 20–63 years). Weighted and directed connectivity was computed by means of Partial Directed Coherence based on a General Linear Kalman filter approach. To keep the information collected by the estimator, weighted and directed graph indices were extracted from the resulting networks. A relation between brain network properties and age of the subject was found, indicating a tendency of the network to randomly organize increasing with age. This result is also confirmed dividing the whole population into two subgroups according to the age (young and middle-aged adults): significant differences exist in terms of network organization measures. Classification of the subjects by means of such indices returns an accuracy greater than 80%.

When I am (almost) 64: The effect of normal ageing on implicit motor imagery in young elderlies

Motor imagery (M.I.) is a cognitive process in which movements are mentally evoked without overt actions. Behavioral and fMRI studies show a decline of explicit M.I. ability (e.g., the mental rehearsal of finger oppositions) with normal ageing: this decline is accompanied by the recruitment of additional cortical networks. However, none of these studies investigated behavioral and the related fMRI ageing modifications in implicit M.I. tasks, like the hand laterality task (HLT). To address this issue, we performed a behavioral and fMRI study: 27 younger subjects (mean age: 31 years) and 29 older subjects (mean age: 61 years) underwent two event-related design fMRI experiments. In the HLT, participants were asked to decide whether a hand rotated at different angles was a left or right hand. To test the specificity of any age related difference in the HLT, we used a letter rotation task as a control experiment: here subjects had to decide whether rotated letters were presented in a standard or a mirror orientation. We did not find any group difference in either behavioral task; however, we found significant additional neural activation in the elderly group in occipito-temporal regions: these differences were stronger for the HLT rather than for the LRT with group by task interactions effects in right occipital cortices. We interpret these results as evidence of compensatory processes associated with ageing that permit a behavioral performance comparable to that of younger subjects. This process appears to be more marked when the task specifically involves motor representations, even when these are implicitly evoked.

Selective improvement of anosognosia for hemiplegia during transcranial direct current stimulation: a case report

Right brain damage patients may not complain of a left sided paralysis up to the point of denying it or even claiming of having just moved an otherwise paralyzed limb. This condition is known as anosognosia for hemiplegia (AHP). Recent behavioural experiments suggest that some residual intentionality might be preserved in patients with anosognosia and that the false belief of having moved originates from a failure to notice discrepancies between movement expectancies and the actual state of the motor system. This failure may be caused by a lack of afferent sensory information concerning the movement or alternatively by a direct dysfunction of the brain regions involved in actions' motor monitoring (i.e., the comparator system). Here we examined the effect of anodal transcranial direct current stimulation (tDCS) of the right premotor cortex in a patient with a bilateral lesion, involving predominantly the right hemisphere, and a dense unawareness for his left hemiplegia. During sham or anodal tDCS the patient was requested to judge his ability to perform simple motor actions (i) without actually executing the movement itself ("offline" condition) and after having performed a series of verbally cued finger opposition movements ("online" condition) with (i) eyes-closed or (ii) eyes-open. We found that anodal tDCS induces a significant remission of the false experience of movement only when the patient is requested to actually perform the movement with eyes open. Conversely, the patient's awareness does not improve in both the "offline" condition (in which the patient does not attempt to perform the movement) and in the "online" condition, when vision is precluded ("online" condition, eyes-closed). We conclude that the stimulation of the premotor cortex by tDCS activates brain regions involved in motor monitoring, temporary restoring the ability of the motor comparator system to correctly appreciate afferent information and build up a veridical motor awareness.