Motor-related Cortical Potentials Research Articles

Cardiorespiratory fitness is associated with cognitive performance in 80 + -year-olds: Detangling processing levels

Cardiorespiratory fitness is known to protect against cognitive decline in older adults. Specifically, it has been shown that physical activity and fitness are beneficial for executive functions that are crucial for independent living up to old age. In this study, 115 individuals aged 80 years and older underwent a cardiorespiratory fitness assessment using the two-minute step test and had their electroencephalogram recorded during a colored flanker task in order to measure executive function performance. Cardiorespiratory fitness was related to quicker responses during the flanker task. A mediation analysis was carried out to determine whether these positive effects were mediated through event-related potentials (N1, N2, or P3) or motor-related cortical potentials (MRCP). Cardiorespiratory fitness was related to better visual discriminative processing as indicated by larger occipital N1 amplitudes. In addition, fitness was associated with larger MRCP amplitudes, which are a correlate of the response generation process. Fitness was not found to have a significant effect on fronto-central N2 or parietal P3, which are thought to capture cognitive control processes such as conflict detection and response inhibition. Moreover, all effects reported were present in all three flanker trial conditions (congruent, neutral, and incongruent). Thus, these results indicate that the quicker response times in fitter people were related to visual processing and motor response generation rather than cognitive control.

Effect of a sex stereotype on cortical activity during a self-paced exercise: A motor-related cortical potential approach

Recent research has shown that inducing a negative stereotype toward women does not always decrease the subsequent motor performance of women, but can increase it, especially during endurance tasks. The mechanisms involved are nonetheless still poorly understood. The main aim of the present study was to investigate the effect of a negative stereotype toward women on men’s and women’s performance during an endurance task, and to analyze the neuropsychological mechanisms involved through motor-related cortical potentials and motivation toward men/women. Thirty-four participants were assigned to a negative stereotype toward women condition and a nullified-stereotype condition and performed 80 self-paced intermittent isometric elbow contractions at a moderate perceived intensity. Results showed that women performed better when assigned to the negative stereotype toward women condition, they were more motivated to outperform men, and their MRCP amplitudes were higher in this same condition over the prefrontal cortex (i.e., FP1 and FP2). Concerning men, they also performed better when the negative stereotype toward women was induced. However, no effect emerged on motivation toward women and MRCP amplitudes. This study showed that inducing a negative stereotype during an endurance task led to a performance increase in women, which is contrary to the stereotype threat theory, strengthening the idea of a task-dependency effect when inducing a negative stereotype. This performance improvement observed in women may be caused by increased motivation to outperform men and a planning of the upcoming movement. Concerning men, more research is needed to clarify the mechanisms involved in such performance improvement.

Neural Bases of Age-Related Sensorimotor Slowing in the Upper and Lower Limbs.

With advanced age, there is a loss of reaction speed that may contribute to an increased risk of tripping and falling. Avoiding falls and injuries requires awareness of the threat, followed by selection and execution of the appropriate motor response. Using event-related potentials (ERPs) and a simple visual reaction task (RT), the goal of our study was to distinguish sensory and motor processing in the upper- and lower-limbs while attempting to uncover the main cause of age-related behavioral slowing. Strength (amplitudes) as well as timing and speed (latencies) of various stages of stimulus- and motor-related processing were analyzed in 48 healthy individuals (young adults, n = 24, mean age = 34 years; older adults, n = 24, mean age = 67 years). The behavioral results showed a significant age-related slowing, where the younger compared to older adults exhibited shorter RTs for the upper- (222 vs. 255 ms; p = 0.006, respectively) and the lower limb (257 vs. 274 ms; p = 0.048, respectively) as well as lower variability in both modalities (p = 0.001). Using ERP indices, age-related slowing of visual stimulus processing was characterized by overall larger amplitudes with delayed latencies of endogenous potentials in older compared with younger adults. While no differences were found in the P1 component, the later components of recorded potentials for visual stimuli processing were most affected by age. This was characterized by increased N1 and P2 amplitudes and delayed P2 latencies in both upper and lower extremities. The analysis of motor-related cortical potentials (MRCPs) revealed stronger MRCP amplitude for upper- and a non-significant trend for lower limbs in older adults. The MRCP amplitude was smaller and peaked closer to the actual motor response for the upper- than for the lower limb in both age groups. There were longer MRCP onset latencies for lower- compared to upper-limb in younger adults, and a non-significant trend was seen in older adults. Multiple regression analyses showed that the onset of the MRCP peak consistently predicted reaction time across both age groups and limbs tested. However, MRCP rise time and P2 latency were also significant predictors of simple reaction time, but only in older adults and only for the upper limbs. Our study suggests that motor cortical processes contribute most strongly to the slowing of simple reaction time in advanced age. However, late-stage cortical processing related to sensory stimuli also appears to play a role in upper limb responses in the elderly. This process most likely reflects less efficient recruitment of neuronal resources required for the upper and lower extremity response task in older adults.

The Neural Blending of Words and Movement: Event-Related Potential Signatures of Semantic and Action Processes during Motor-Language Coupling.

Behavioral embodied research shows that words evoking limb-specific meanings can affect responses performed with the corresponding body part. However, no study has explored this phenomenon's neural dynamics under implicit processing conditions, let alone by disentangling its conceptual and motoric stages. Here, we examined whether the blending of hand actions and manual action verbs, relative to nonmanual action verbs and nonaction verbs, modulates electrophysiological markers of semantic integration (N400) and motor-related cortical potentials during a lexical decision task. Relative to both other categories, manual action verbs involved reduced posterior N400 amplitude and greater modulations of frontal motor-related cortical potentials. Such effects overlapped in a window of ∼380-440 msec after word presentation and ∼180 msec before response execution, revealing the possible time span in which both semantic and action-related stages reach maximal convergence. These results allow refining current models of motor-language coupling while affording new insights on embodied dynamics at large.

Locomotor activities as a way of inducing neuroplasticity: insights from conventional approaches and perspectives on eccentric exercises.

Corticospinal excitability, and particularly the balance between cortical inhibitory and excitatory processes (assessed in a muscle using single and paired-pulse transcranial magnetic stimulation), are affected by neurodegenerative pathologies or following a stroke. This review describes how locomotor exercises may counterbalance these neuroplastic alterations, either when performed under its conventional form (e.g., walking or cycling) or when comprising eccentric (i.e., active lengthening) muscle contractions. Non-fatiguing conventional locomotor exercise decreases intracortical inhibition and/or increases intracortical facilitation. These modifications notably seem to be a consequence of neurotrophic factors (e.g., brain-derived neurotrophic factor) resulting from the hemodynamic solicitation. Furthermore, it can be inferred from non-invasive brain and peripheral stimulation studies that repeated activation of neural networks can endogenously shape neuroplasticity. Such mechanisms could also occur following eccentric exercises (lengthening of the muscle), during which motor-related cortical potential (electroencephalography) is of greater magnitude and lasts longer than during concentric exercises (i.e., muscle shortening). As single-joint eccentric exercise decreased short- and long-interval intracortical inhibition and increased intracortical facilitation, locomotor eccentric exercise (e.g., downhill walking or eccentric cycling) may be even more potent by adding hemodynamic-related neuroplastic processes to endogenous processes. Besides, eccentric exercise is especially useful to develop relatively high force levels at low cardiorespiratory and perceived intensities, which can be a training goal alongside the induction of neuroplastic changes. Even though indirect evidence let us think that locomotor eccentric exercise could shape neuroplasticity in ways relevant to neurorehabilitation, its efficacy remains speculative. We provide future research directions on the neuroplastic effects and underlying mechanisms of locomotor exercise.

Effects of a dual task and different levels of divided attention on motor-related cortical potential.

[Purpose] The aim of this study was to investigate the effect of divided attention on motor-related cortical potential (MRCP) during dual task performance while the difficulty of the secondary task was altered. [Participants and Methods] Twenty-two right-handed healthy volunteers participated in the study. MRCPs were recorded during two tasks, a single task (ST) and a simple (S-DT) or complex dual task (C-DT). The ST involved a self-paced tapping task in which the participants extended their right index finger. In the dual task, the participants performed the ST and a visual number counting task simultaneously. [Results] The amplitude and integral value of MRCP from electroencephalography electrode C3 was significantly higher in the S-DT than in the ST, whereas they were similar between the C-DT and the ST. Medium-load divided attention (i.e., S-DT) led to significantly more changes in the MRCP magnitude than did low-load divided attention (i.e., ST). However, the MRCP of high-load divided attention (i.e., C-DT) was similar to that of low-load divided attention. [Conclusion] These results suggest that MRCP reflects the function of or network between the supplementary motor area and the dorsolateral prefrontal cortex, and may serve as a marker for screening the capacity of individuals to perform dual tasks.

Cognitive performance and brain dynamics during walking with a novel bionic foot: A pilot study

ObjectivesThe objectives are to determine neural dynamics during gait using electro-encephalography and source localization, and to investigate the attentional demand during walking in able-bodied individuals, and individuals with an amputation.Materials & methodsSix able-bodied individuals conducted one experimental trial, and 6 unilateral transtibial and 6 unilateral transfemoral amputees performed 2 experimental trials; the first with the prosthesis currently used by the subjects and the second with a novel powered transtibial prosthesis, i.e. the Ankle Mimicking Prosthetic foot 4.0. Each experimental trial comprised 2 walking tasks; 6 and 2 minutes treadmill walking at normal speed interspersed by 5 minutes of rest. During 6 minutes walking the Sustained Attention to Response (go-no go) Task, which measures reaction time and accuracy, was performed. Electro-encephalographic data were gathered when subjects walked 2 minutes. Motor-related cortical potentials and brain source activity during gait were examined. Normality and (non-) parametric tests were conducted (p<0.05).Results and discussionIn contrast to transtibial amputees, transfemoral amputees required more attentional demands during walking with Ankle Mimicking Prosthetic foot 4.0 compared to the current passive prosthetic device and able-bodied individuals (reaction time and accuracy: p≤0.028). Since risk of falling is associated with altered attentional demands, propulsive forces of the novel device need to be better controlled for transfemoral amputees. No motor-related cortical potentials at Cz were observed in transfemoral amputees walking with the novel prosthesis, whereas motor-related cortical potentials between transtibial amputees and able-bodied individuals during walking at normal speed did not differ. The first positive electro-physiological peak deflection appeared during toe-off phase and showed higher activity within the underlying brain sources in transtibial amputees walking with Ankle Mimicking Prosthetic foot 4.0 compared to able-bodied individuals. The required higher neural input to accomplish the same physical activity compared to able-bodied individuals is possibly due to the limited acclimation period to the novel device and consequently increased afferent sensory feedback for postural control.

Movement-related cortical potential in patients with acute stroke

Aim To identify the pattern and side of brain plasticity following acute stroke in patients who recovered and assess motor upper limb function using motor-related cortical potentials. Patients and methods Eleven patients diagnosed with acute ischemic stroke were recruited from in patients and stroke clinic within Ain Shams University Hospital. They were assessed after 2 or more weeks from stroke onset and showed power in finger flexors and extensors of two or more according to Medical Research Council; their motor recovery was assessed by using Fugal–Meyer scale. A high-density 64-channel electroencephalogram connected to an event-related potential software detector is used to record motor-related cortical potential by asking the patient to press on a bottom for an average of 130 presses with a free interval of 3–5 s between each press using the index finger of the paretic hand. Motor potential epoch component was filtered and analyzed regarding amplitude and latency using event-related potential lab within a MATLAB software programmed for analyzing event-related potentials with particular attention to lateralized readiness potentials along cortical areas of interest. Results A total of 11 adult patients completed the study. Three (75%) patients with right-side weakness had potential from the intact side, and one (25%) patients had potential from the lesion side. Six (86%) patients with left-side weakness had potential from the intact side, and one (14%) patients had potential from the lesion side. There was a weak nonassociation between the source of potential and the side of weakness (Cramer's V = 0.13, P = 0.65). Conclusion This study investigated brain activity changes during movement intention and execution of index movement using comprehensive EEG analysis method, which combined indicator mammalian ependymin-related proteins (MERPs) and choroidal neovascularization (CNV) time-frequency mapping. EEG changes in time and time-frequency domains showed different topographical features and might provide comprehensive information for studying movement disorders such as those in a poststroke patient.

Concealed Around-the-Ear EEG Captures Cognitive Processing in a Visual Simon Task.

In theory, miniaturized systems such as the around-the-ear electrode arrays (cEEGrids) enable mobile monitoring of the electroencephalogram (EEG) in a variety of real life situations without interfering with the natural setting. However, the research benefit of such cEEGrid recordings critically depends on their validity. To investigate whether visual and motor processing are reflected in the cEEGrid-EEG, a direct comparison of EEG that was concurrently recorded with the cEEGrids and with a high-density cap setup was conducted. Thirteen participants performed a classic Simon task in which letters were presented laterally and a lateralized choice response was executed. N1, P1 and P300 event-related potential (ERP) waveforms were extracted from cEEGrid-EEG: they were found to be strongly correlated with corresponding waveforms extracted from cap-EEG but with lower signal strength and lower signal-to-noise-ratio (SNR). Event-related lateralizations (ERLs) recorded at posterior scalp sites were well reflected in middle cEEGrid pairs. Moreover, the effect size of the Simon correspondence effect on the extracted ERLs was similar between the two systems. However, lateralizations at central cap sites were less well reflected in the cEEGrid-EEG indicating a difficulty in capturing motor response preparation and execution. These results show that well-described visual and cognitive ERPs and ERLs can be measured using the cEEGrids, while motor-related cortical potentials are not well captured. This study further demonstrates the potential and possible limitations of unobtrusive cEEGrid-EEG recordings.

17. Simultaneous recording of motor related cortical potentials to different basal components of voluntary movements

The purpose of the paper was to compare motor related cortical potentials (MRCPs) to basic components of voluntary movements in prolonged recording sessions. EEG activity (27 electrodes placed over the sensorimotor cortex) was recorded in 10 normal volunteers instructed to perform a sequence of 3 simple self-paced movements with the right index finger, separated by an interval of at least 3–4 s: (1) rapid, ballistic-type (Bt-) extension with immediate automated return to resting position; (2) rapid extension (Ex-) to reach and maintain a defined target followed by (3) relaxation (Re-) with passive return to resting position. A prolonged recording session (80 min) provided, for each task, a sequence of 4 MRCPs resulting from the average of 4 successive blocks of 40–80 artefact-free EEG epochs (3 s before and 1 s after onset of individual movements derived from the mechanogram). Recording breaks of about 10–20 s, without interruption of motor task, were interposed at intervals of 3–4 min. Pre- and post-movement components were stable in all MRCPs throughout the recording session. All potentials showed a similar onset and duration of pre-movement components with a similar scalp distribution. Clear-cut differences were observed in the post-movement components probably reflecting different afferent patterns from peripheral effectors.

18. Simultaneous recording of motor related cortical potentials to different basal components of voluntary movements during a sustained fatigue task

Our aim was to study the effects of a sustained fatigue task on Motor Related Cortical Potentials (MRCPs) to basic components of voluntary movements. In 10 normal volunteers MRCPs to Ballistic, Extension movements and Relaxation of the right index finger, according to the method described in the companion paper (Troni et al.,1966) were recorded during a sustained (80 min) fatigue task. The task consisted in continuous finger extension to maintain a fixed position at half of maximal range of motion (basal position) while supporting a load (30–50 g) hanging on distal phalanx. The sequence of the 3 motor tasks was superimposed to the fatigue task. Fatigue was monitored using a 10 points Visual Analogic Scale (VAS). A significant increase in amplitude of all post-movement components was observed in Bt- and Ex-MRCPs, associated with a substantial stability of pre-movement components (early- and late-BP) throughout the experimental session. A similar trend was initially observed for Re-MRCP, later followed by a progressive reduction in amplitude of both late-BP and post-movement components. The post-movement changes of Bt- and Ex-MRCP can hardly be attributed to fatigue because of early occurrence and temporal stability. The late and progressive deterioration of Re-MRCP strongly indicates a fatigue effect.

The temporal coupling effect: Preparation and execution of bimanual reaching movements

The study of bimanual movements has allowed to describe an interesting phenomenon known as the bimanual coupling effect: a lack of independence between the two hands that induces an interference process, which has been reported in both the spatial and temporal domain. Here, we studied for the first time the electro-cortical activity of the temporal bimanual coupling effect, specifically focused on the motor preparation of the two hands movements. Participants performed congruent movements, with both hands heading towards easy or difficult targets, and incongruent movements, with the two hands heading to separate targets (i.e. left to the easy target and right to the difficult target). Motor Related Cortical Potentials (MRCPs) showed no effect of conditions or difficulty on the early phase of the activity (posterior and anterior BP). Additionally, the two hands were prepared together, as if a single movement was about to start. As such, behavioral results showed strong synchronization between the hands, which always tended to start and end their movement together. Importantly, the effect of movement difficulty was present at the movement onset and just after it when the movement unfolded. Coherently with behavioral results, difficult movements generated a strong Post-motor potential (N4), more prominent when the right hand was heading towards the difficult target. Our findings show that bimanual movements are actually planned and programmed as a single motor program, but movement difficulty emerges in the execution of the action.

Cortical substrates of the effects of caffeine and time-on-task on perception of effort.

Caffeine intake results in a decrease in perception of effort, but the cortical substrates of this perceptual effect of caffeine are unknown. The aim of this randomized counterbalanced double-blind crossover study was to investigate the effect of caffeine on the motor-related cortical potential (MRCP) and its relationship with rating of perceived effort (RPE). We also investigated whether MRCP is associated with the increase in RPE occurring over time during submaximal exercise. Twelve healthy female volunteers performed 100 intermittent isometric knee extensions at 61 ± 5% of their maximal torque 1.5 h after either caffeine (6 mg/kg) or placebo ingestion, while RPE, vastus lateralis electromyogram (EMG), and MRCP were recorded. RPE and MRCP amplitude at the vertex during the first contraction epoch (0-1 s) were significantly lower after caffeine ingestion compared with placebo (P < 0.05) and were significantly higher during the second half of the submaximal intermittent isometric knee-extension protocol compared with the first half (P < 0.05). No significant effects of caffeine and time-on-task were found for EMG amplitude and submaximal force output variables. The covariation between MRCP and RPE across both caffeine and time-on-task (r10 = -0.335, P < 0.05) provides evidence in favor of the theory that perception of effort arises from neurocognitive processing of corollary discharges from premotor and motor areas of the cortex. Caffeine seems to reduce perception of effort through a reduction in the activity of cortical premotor and motor areas necessary to produce a submaximal force, and time-on-task has the opposite effect.

Differences in Visuo-Motor Control in Skilled vs. Novice Martial Arts Athletes during Sustained and Transient Attention Tasks: A Motor-Related Cortical Potential Study

Cognitive and motor processes are essential for optimal athletic performance. Individuals trained in different skills and sports may have specialized cognitive abilities and motor strategies related to the characteristics of the activity and the effects of training and expertise. Most studies have investigated differences in motor-related cortical potential (MRCP) during self-paced tasks in athletes but not in stimulus-related tasks. The aim of the present study was to identify the differences in performance and MRCP between skilled and novice martial arts athletes during two different types of tasks: a sustained attention task and a transient attention task. Behavioral and electrophysiological data from twenty-two martial arts athletes were obtained while they performed a continuous performance task (CPT) to measure sustained attention and a cued continuous performance task (c-CPT) to measure transient attention. MRCP components were analyzed and compared between groups. Electrophysiological data in the CPT task indicated larger prefrontal positive activity and greater posterior negativity distribution prior to a motor response in the skilled athletes, while novices showed a significantly larger response-related P3 after a motor response in centro-parietal areas. A different effect occurred in the c-CPT task in which the novice athletes showed strong prefrontal positive activity before a motor response and a large response-related P3, while in skilled athletes, the prefrontal activity was absent. We propose that during the CPT, skilled athletes were able to allocate two different but related processes simultaneously according to CPT demand, which requires controlled attention and controlled motor responses. On the other hand, in the c-CPT, skilled athletes showed better cue facilitation, which permitted a major economy of resources and “automatic” or less controlled responses to relevant stimuli. In conclusion, the present data suggest that motor expertise enhances neural flexibility and allows better adaptation of cognitive control to the requested task.

The motor preparation of directionally incompatible movements

This work explores, for the first time, the electro-cortical activity related to the preparation of bimanual incompatible actions. To accomplish this aim, we recorded motor-related cortical potentials (MRCPs) in 16 healthy subjects, who were asked to draw lines and/or circles during three experimental conditions: Unimanual, Bimanually Compatible (either lines or circles with both hands) and Bimanually Incompatible (a line with one hand and a circle with the other hand). We show that the electro-cortical activity recorded during the preparation of the bimanually incompatible actions included a central positivity (CP) that began approximately 2.5s before movement onset and was localized in medial frontal areas. We then recorded a later (ca. 700ms before movement onset) negative activity in the supplementary motor area (consistent with Bereitschaftspotential). Finally, a strong frontal lateral positivity (FLP) emerged ca. 1.8s before the initiation of drawing that was localized in the dorsolateral prefrontal cortex. All components were bilateral. The CP component has not been described before. These data are discussed with regard to the “interference network” theory.

Efficacy of brain-computer interface-driven neuromuscular electrical stimulation for chronic paresis after stroke

Brain computer interface technology is of great interest to researchers as a potential therapeutic measure for people with severe neurological disorders. The aim of this study was to examine the efficacy of brain computer interface, by comparing conventional neuromuscular electrical stimulation and brain computer interface-driven neuromuscular electrical stimulation, using an A-B-A-B withdrawal single-subject design. A 38-year-old male with severe hemiplegia due to a putaminal haemorrhage participated in this study. The design involved 2 epochs. In epoch A, the patient attempted to open his fingers during the application of neuromuscular electrical stimulation, irrespective of his actual brain activity. In epoch B, neuromuscular electrical stimulation was applied only when a significant motor-related cortical potential was observed in the electroencephalogram. The subject initially showed diffuse functional magnetic resonance imaging activation and small electro-encephalogram responses while attempting finger movement. Epoch A was associated with few neurological or clinical signs of improvement. Epoch B, with a brain computer interface, was associated with marked lateralization of electroencephalogram (EEG) and blood oxygenation level dependent responses. Voluntary electromyogram (EMG) activity, with significant EEG-EMG coherence, was also prompted. Clinical improvement in upper-extremity function and muscle tone was observed. These results indicate that self-directed training with a brain computer interface may induce activity- dependent cortical plasticity and promote functional recovery. This preliminary clinical investigation encourages further research using a controlled design.

Similar Cerebral Motor Plans for Real and Virtual Actions

A simple movement, such as pressing a button, can acquire different meanings by producing different consequences, such as starting an elevator or switching a TV channel. We evaluated whether the brain activity preceding a simple action is modulated by the expected consequences of the action itself. To further this aim, the motor-related cortical potentials were compared during two key-press actions that were identical from the kinematics point of view but different in both meaning and consequences. In one case (virtual grasp), the key-press started a video clip showing a hand moving toward a cup and grasping it; in the other case, the key-press did not produce any consequence (key-press). A third condition (real grasp) was also compared, in which subjects actually grasped the cup, producing the same action presented in the video clip. Data were collected from fifteen subjects. The results showed that motor preparation for virtual grasp (starting 3 s before the movement onset) was different from that of the key-press and similar to the real grasp preparation–as if subjects had to grasp the cup in person. In particular, both virtual and real grasp presented a posterior parietal negativity preceding activity in motor and pre-motor areas. In summary, this finding supports the hypothesis that motor preparation is affected by the meaning of the action, even when the action is only virtual.

Awareness affects motor planning for goal-oriented actions

We studied pre-movement cortical activity related to praxic actions performed at self-paced rate and having ecological meanings and functions. Motor-related cortical potentials were recorded using 64-channels EEG in two experiments. Experiment 1 included 15 subjects performing in separate blocks two object-oriented actions: grasping a tea-cup and impossible grasping of a tea-cup (same goal but the grasp was mechanically hindered). Experiment 2 included a subset of 7 subjects from Exp. 1 and the action was reaching a tea-cup; this control condition had a different goal but was kinematically similar to impossible grasping. Different activity patterns in terms of onset, amplitude, duration and, at least in part, sources were recorded in the preparation phase (BP component) according to the specific action and to the possibility of accomplishing it. The main result is that parietal areas were involved in grasping preparation (called “posterior” BP) and not in reaching and impossible grasping preparation. The anterior frontal-central activity (called “anterior” BP) during preparation for grasping started earlier than the other two conditions. The cortical activity during preparation for reaching was similar to that for impossible grasping, except for a frontal activity only detected in the latter condition. It is concluded that the action preparation, even in its early phase, is affected by action meaning and by the awareness of being able to perform the requested action.

Effect of Mastication on Human Brain Activity

Mastication is a complicated movement generated from a neural population in the brainstem and a neural network involving several brain regions. Recently, attention has been focused on the relationship between mastication and age-related decline in human cognitive function, but the neural mechanisms underlying this association remain unknown. In this article, we review research on the effect of mastication based on data obtained using event-related potentials (ERPs), including the P300 component and contingent negative variation (CNV), motor-related cortical potentials (MRCPs), and reaction time (RT) as behavioral data. The peak latency of P300 and RT clearly shortened with the repetition of sessions in Mastication, but not in Control, Jaw Movement, or Finger Tapping. The mean amplitude of CNV differed between the Mastication and Control conditions with the repetition of sessions. By contrast, there was no significant difference in the amplitude of MRCP between Mastication and Control in any of the sessions. These results suggest that mastication is associated with cognitive processing rather than movement-related processing in the human brain. We believe that non-invasive recording methods, such as electroencephalography (EEG), magnetoencephalography (MEG), transcranial magnetic stimulation (TMS), functional magnetic resonance imaging (fMRI), and near-infrared spectroscopy (NIRS), will supply valuable evidence in support of a positive relationship between mastication and cognition.

Perceived effort in force production as reflected in motor-related cortical potentials

Objective: The perceived effort in force production was investigated in a series of experiments where subjects performed isometric force tasks with the index finger while the nominal force, the rate of force development and signal gain were controlled and rating of effort for each task was obtained. The hypotheses tested were that: (1) force-related perceived effort may selectively influence the amplitude of motor-related cortical potentials (MRCP); and (2) the MRCP may directly reflect the intensity of perceived effort associated with force production. Methods: The force trace was displayed on a computer monitor using various control-gains so that the perceived effort matched or was at odds with actual muscular effort applied to the load cell to accomplish the task. The MRCP were extracted from continuous EEG records using averaging techniques. Results: The findings showed that: (1) perceived effort proportionally increased with the increment of rate of force development and force error, but not with the actual force level; (2) the amplitude of the MRCP increased when a large amount of force was accompanied by an increased rate of force development; (3) the amplitude of early components of MRCP preceding the force initiation (MP-100 to 0) increased as a function of anticipated effort, whereas, the amplitude movement-monitoring potentials (MMP) accompanying the force production increased as a function of actual force level. Conclusions: The findings from this study provide additional insight clarifying the distinct patterns of EEG activity exhibited under various degrees of perceived effort associated with force output. The findings support the hypothesis that the early components of MRCP may reflect the perceived effort associated with achieving the required force level. Significance: The results from this study may be considered in the larger context of physical activity in terms of importance of perceived effort during prescribed exercise in rehabilitation programs.