Motor imagery requires individuals to form an internal representation of a specific action within working memory without any overt output. Motor imagery has proven effective in improving motor performance of specific skills. This study explored whether different motor imagery strategies influence corticospinal excitability in young (20-35 years) and older subjects (over 55 years). In addition, the effectiveness of these strategies in targeting modulations in motor cortical output and whether the hand “performing” the task was important were also examined. Motor imagery ability was measured using the Kinesthetic and Visual Imagery Questionnaire (KVIQ) and mental chronometry. Working memory including visuospatial, verbal and kinesthetic domains was measured by immediate serial recall. To determine the effect of imagery on corticospinal excitability transcranial magnetic stimulation (TMS) was applied over the contralateral motor cortex as subjects imagined abducting their index finger. Motor evoked potentials (MEPs) were recorded from first dorsal interosseous (FDI), abductor pollicis brevis and abductor digiti minimi muscles (ADM). As subjects performed motor imagery, they were guided by visual, auditory or a combination of visual and auditory cues. Strategies were introduced in randomized sequence interspersed with a rest and a muscle activation condition. Motor imagery ability and verbal working memory were comparable between young and older subjects (p > 0.05). In both groups, MEP amplitudes in the FDI muscle were significantly increased during motor imagery compared to rest regardless of the strategy used (p < 0.001). Visual cueing was the most effective at isolating facilitation to the target muscle (FDI), whereas with the auditory and combined strategies both FDI and ADM muscles generated MEPs that were comparable in amplitude (p > 0.05). TMS induced MEPs were greater in amplitude when the left hemisphere was stimulated during motor imagery of the right finger while being guided by either auditory or visual cueing. In combination, these findings suggest that motor imagery increases corticospinal excitability and the strategy used may serve to target the facilitation. / Thesis (Master, Rehabilitation Science) -- Queen's University, 2008-08-26 15:58:21.277

Research has shown the combination of strength training and motor imagery can increase isometric force production. This study explored the impact of motor imagery on dynamic strength using a 3RM bench press and back squat. Participants were randomized into either the treatment or placebo condition and engaged in an11 week training program (motor imagery: n=8; motivational music: n=7). Results for both the upper and lower body strength showed a significant overall main effect for time from baseline to post-test measure (upper body: motor imagery: M= 43.5 kg, SD= 18.65 kg to M= 60.7 kg, SD= 24.0 kg; placebo: M= 45.0 kg, SD= 15.54 kg to M=55.0 kg, SD=17.9 kg; p=.000) (lower body: motor imagery: M= 82.9 kg, SD= 29.72 kg to M=110.0 kg, SD= 23.4 kg; placebo: M= 84.6 kg, SD= 20.29 kg to M=119.3 kg, SD= 24.6 kg; p=.000). The upper body strength displayed a significant interaction effect (p=.001) between program type and time, lower body strength had an insignificant interaction effect (p=.162, ?p2=.162). Finally, there was no between group significant difference for overall main of upper (p=.870, ?p2=.002) and lower body (p=.818, ?p2=.004) strength. These results suggest that motor imagery may have an impact on the development of strength over an 11 week training program. However, further understanding of imagery use and how it impacts strength is needed.

The topic of this work is motor imagery. Through 7 different studies, the process and proprieties of motor imagery and its impact on motor learning were assessed. It was found that this cognitive activity is closely linked to the motor system. This characteristic underlies the positive effects of motor imagery on motor learning. This can have many practical applications in the domain of sport and motor rehabilitation.

The primary intent of this study was to explore fundamental questions about the role and relationship between motor (MI) and visual (VI) imagery within the context of estimating reach. Experiment 1 examined and compared VI and MI tasks under matched environmental conditions with the intent to explore the distinction and cooperation of the visual and motor systems in representing actions. The design of this experiment included an interference paradigm modified from Stevens (2005) in which six blocks of trials (conditions) were used: MI, VI, MI with visual interference, MI with motor interference, VI with motor interference, and VI with visual interference. Results indicated that MI was significantly more accurate than VI in regard to total error, distribution of error and mean bias (p <= .05). Significant increases in the number of errors and estimation bias were found when the modalities for the imagined task and the interference task were matched. The data showed that motor tasks interfered with the ability to MI, whereas visual tasks interfered with the ability to VI. Experiment 2 included a response-delay paradigm modified from Bradshaw and Watt (2002) in which eight blocks of trials were used: MI and VI conditions with no-delay and delays of 1-, 2- and 4 s. Overall, this experiment demonstrated that response-delay influenced accuracy of the MI (visuomotor) task, but not the VI (perceptual) task. That is, after a 4s delay, error in MI increased significantly. Interestingly, these results may indicate a crucial temporal constraint for the representation of distance, isolated in the visuomotor system. In view of both experiments, the findings are consistent with the notion of a distinction between vision for perception (VI) and vision for action (MI) as advanced by Goodale, Westwood & Milner (2004). In conclusion, VI seems to delineate relevant spatial parameters within the environment and then transfer the information to MI. At this point, information is computed in terms of biomechanical possibilities for a certain movement. In summary, just as perception and action are firmly linked, so too are MI and VI.

The primary intent of this study was to explore fundamental questions about the role and relationship between motor (MI) and visual (VI) imagery within the context of estimating reach. Experiment 1 examined and compared VI and MI tasks under matched environmental conditions with the intent to explore the distinction and cooperation of the visual and motor systems in representing actions. The design of this experiment included an interference paradigm modified from Stevens (2005) in which six blocks of trials (conditions) were used: MI, VI, MI with visual interference, MI with motor interference, VI with motor interference, and VI with visual interference. Results indicated that MI was significantly more accurate than VI in regard to total error, distribution of error and mean bias (p <= .05). Significant increases in the number of errors and estimation bias were found when the modalities for the imagined task and the interference task were matched. The data showed that motor tasks interfered with the ability to MI, whereas visual tasks interfered with the ability to VI. Experiment 2 included a response-delay paradigm modified from Bradshaw and Watt (2002) in which eight blocks of trials were used: MI and VI conditions with no-delay and delays of 1-, 2- and 4 s. Overall, this experiment demonstrated that response-delay influenced accuracy of the MI (visuomotor) task, but not the VI (perceptual) task. That is, after a 4s delay, error in MI increased significantly. Interestingly, these results may indicate a crucial temporal constraint for the representation of distance, isolated in the visuomotor system. In view of both experiments, the findings are consistent with the notion of a distinction between vision for perception (VI) and vision for action (MI) as advanced by Goodale, Westwood & Milner (2004). In conclusion, VI seems to delineate relevant spatial parameters within the environment and then transfer the information to MI. At this point, information is computed in terms of biomechanical possibilities for a certain movement. In summary, just as perception and action are firmly linked, so too are MI and VI.

Past research has indicated that motor imagery, or imagined movement, follows Fitts' law similarly to physical movement. Additionally, motor imagery has been shown to improve real motor performance in multiple contexts, showcasing a remarkable connection with real motion. The current study examines how the subject of motor imagery, imagining oneself, another person, or an object, impacts this faithfulness to real movement, specifically in following Fitts' law. Participants viewed 2D photos of a virtual environment with an "X", a humanoid, or a disc facing a gate at 6 distances and 4 widths for 24 combinations. Each combination was repeated twice randomly for 48 trials per condition, and conditions were presented in random order for a total of 144 trials. Results indicate that object-imagery does trigger motor imagery and follow Fitts' law, in contrast to prior research. However, further analysis showed that the function produced in the object condition was significantly different from both self and other, while self and other were not significantly different from one another. This was due to a higher index of performance value in the object condition, implying that participants assigned the object different abilities than the two human-centered conditions. These results indicate a difference related to biological, or perhaps human, motion, and future studies should further explore the impact of the subject and characteristics of the subject on motor imagery. Understanding these intricacies is crucial to refine and understand the benefits of motor imagery seen in multiple motor performance contexts.

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Muscle weakness is one of the major causes of post-stroke disability. Stroke rehabilitation programs now often incorporate the same type of resistance training that is used for healthy subjects; however, the training effects induced from these training strategies are often limited for stroke patients. An important resistance training principle is that an optimal level of stress is exerted on the neuromuscular system, both during concentric (shortening) and eccentric (lengthening) contractions. One potential problem for post-stroke patients might be difficulties achieving sufficient levels of stress on the neuromuscular system. This problem may be associated with altered muscular function after stroke. In healthy subjects, maximum strength during eccentric contractions is higher than during concentric contractions. In individuals with stroke, this difference in strength is often increased. Moreover, it has also been shown that individuals with stroke exhibit alteration with respect to how the strength varies throughout the range of motion. For example, healthy subjects exhibit a joint specific torque-angle relationship that normally is the same irrespective of contraction mode and contraction velocity. In contrast, individuals with stroke exhibit an overall change of the torque-angle relationship. This change, as described in the literature, consists of a more pronounced strength loss at short muscle length. In individuals with stroke, torque-angle relationships are only partially investigated and so far these relationships have not been analysed using testing protocols that include eccentric, isometric, and concentric modes of contraction.   This thesis investigates the torque-angle relationship of elbow flexors in subjects with stroke during all three modes of contractions – isometric, concentric, and eccentric ­– and the relative loading throughout the range of movement during a resistance exercise. In addition, this thesis studies possible central nervous system mechanisms involved in the control of muscle activation during eccentric and concentric contractions.   The torque-angle relationship during maximum voluntary elbow flexion was examined in stroke subjects (n=11), age-matched healthy subjects (n=11), and young subjects (n=11) during different contraction modes and velocities. In stroke subjects, maximum torque as well as the torque angle relationship was better preserved during eccentric contractions compared to concentric contractions. Furthermore, the relative loading during a resistance exercise at an intensity of 10RM (repetition maximum) was examined. Relative loading throughout the concentric phase of the resistance exercise, expressed as percentage of concentric torque, was found to be similar in all groups. However, relative loading during the eccentric contraction phase, expressed as the percentage of eccentric isokinetic torque, was significantly lower for the stroke group. In addition, when related to isometric maximum voluntary contraction, the loading for the stroke group was significantly lower than for the control groups during both the concentric and eccentric contraction phases. Functional magnetic resonance imaging was used to examine differences between recruited brain regions during the concentric and the eccentric phase of imagined maximum resistance exercise of the elbow flexors (motor imagery) in young healthy subjects (n=18) and in a selected sample of individuals with stroke (n=4). The motor and premotor cortex was less activated during imagined maximum eccentric contractions compared to imagined maximum concentric contraction of elbow flexors. Moreover, BA44 in the ventrolateral prefrontal cortex, a brain area that has been shown to be involved in inhibitory control of motor activity, was additionally recruited during eccentric compared to concentric conditions. This pattern was evident only on the contralesional (the intact hemisphere) in some of the stroke subjects. On the ipsilesional hemisphere, the recruitment in ventrolateral prefrontal cortex was similar for both modes of contractions.    Compared to healthy subjects, the stroke subjects exhibited altered muscular function comprising a specific reduction of torque producing capacity and deviant torque-angle relationship during concentric contractions. Therefore, the relative training load during the resistance exercise at a training intensity of 10RM was lower for subjects with stroke. Furthermore, neuroimaging data indicates that the ventrolateral prefrontal cortex may be involved in a mechanism that modulates cortical motor drive differently depending on mode of the contractions. This might partly be responsible for why it is impossible to fully activate a muscle during eccentric contractions. Moreover, among individuals with stroke, a disturbance of this system could also lie behind the lack of contraction mode-specific modulation of muscle activation that has been found in this population. The altered neuromuscular function evident after a stroke means that stroke victims may find it difficult to supply a sufficient level of stress during traditional resistance exercises to promote adaptation by the neuromuscular system. This insufficiency may partially explain why the increase in strength, in response to conventional resistance training, often has been found to be low among subjects with stroke. / Muskelsvaghet är en av orsakerna till funktionshinder efter stroke. I rehabiliteringsprogram för personer som drabbats av stroke förekommer det numera att styrketräning används i syfte att öka muskelstyrkan. Effekten av styrketräning har dock ofta visat sig vara begränsad. En viktig styrketräningsprincip är att muskulaturen belastas tillräckligt nära maximal styrka under både koncentriska kontraktioner (när man lyfter en vikt) och excentriska kontraktioner (när man kontrollerat sänker en vikt). Ett potentiellt problem skulle kunna vara att personer med stroke inte belastas optimalt under träning på grund av förändrad muskelfunktion. Efter stroke är muskelfunktionen ofta förändrad såtillvida att styrkenedsättningen är mer uttalad under koncentriska kontraktioner. Därutöver har man funnit att styrkenedsättningen är mest uttalad när muskeln är i sitt mest förkortade läge. Detta fenomen har dock inte studerats för alla tre kontraktionstyper, det vill säga excentriska, koncentriska och isometriska kontraktioner, hos personer med stroke.   Denna avhandling undersöker sambandet mellan styrka och ledvinkel över armbågsleden hos personer med stroke under alla tre kontraktionstyper – excentrisk, koncentrisk och isometrisk, samt relativ belastning genom rörelsebanan under en styrketräningsövning. Därutöver undersöker denna avhandling också hjärnans aktiveringsmönster under excentriska och koncentriska kontraktioner.   Sambandet mellan styrka och ledvinkel undersöktes hos personer med stroke (n = 11), åldersmatchade (n = 11) och unga försökspersoner (n = 11). Jämfört med kontrollgrupperna var maximal styrka för personer med stroke mest nedsatt, samt även den oproportionerligt stora styrkenedsättningen vid kort muskelängd som mest uttalad, under koncentriska kontraktioner. Denna avvikelse var minst uttalad vid excentriska kontraktioner. Vidare studerades hur hög belastningen på muskulaturen var i jämförelse med muskelns maximala styrka under en styrketräningsliknande övning för armbågsflexorer vid en träningsintensitet på 10RM. Den uppmätta belastningen under den koncentriska fasen av styrketräningsövningen, uttryckt som procent av den genomsnittliga koncentriska styrkan, var densamma för alla grupperna. Under den excentriska fasen av övningen var dock belastningen, uttryckt som procent av den maximala excentriska styrkan, signifikant lägre för personer med stroke. Träningsbelastningen utgjorde också en lägre andel av den maximala isometriska styrkan för personer med stroke, både under den koncentriska och under den excentriska fasen.   Funktionell magnetresonanstomografi (fMRI) användes för att undersöka hjärnans aktiveringsmönster hos unga försökspersoner (n = 18) och hos individer med stroke (n = 4) när de föreställde sig att de utförde maximal styrketräning för armbågsflexorer (motor imagery). Resultatet visade att primära motorbarken och premotoriska barken var mindre aktiverade när unga friska försökspersonerna föreställde sig utföra maximala excentriska, jämfört med maximala koncentriska kontraktioner. Dessutom var en region i ventrolaterala prefrontala barken, som i tidigare studier visat sig vara inblandat i reglering och hämning av muskelaktivering, mer aktiverade under föreställda excentriska kontraktioner. Detta aktiveringsmönster i den prefrontala barken återfanns dock endast i den icke skadade hjärnhalvan hos personer med stroke.   Jämfört med kontrollgrupperna uppvisade försökspersonerna med stroke en förändrad muskelfunktion som bestod av en specifik nedsättning av styrkan under koncentriska kontraktioner samt också ett mer avvikande samband mellan styrka och ledvinkel under koncentriska kontraktioner. Den relativa belastningen under utförandet av en styrketräningsövning med en intensitet på 10RM var på grund av dessa avvikelser lägre för försökspersoner med stroke. Hjärnavbildnings-studierna indikerade att ventrolaterala prefrontala barken verkar vara involverat i ett kortikalt moduleringssystem som reglerar muskel-aktivering olika beroende på kontraktionstyp under maximala kontraktioner. Detta skulle kunna vara en underliggande mekanism bakom den hittills obesvarade frågan varför det är omöjligt att aktivera muskulaturen maximalt under excentriska kontraktioner. En störning av detta moduleringssystem hos personer med stroke verkar också kunna ligga bakom den förändrade regleringen av muskelaktivering som visat sig förekomma hos personer med stroke. Neuromuskulär funktion efter stroke är förändrad i flera avseenden vilket verkar medföra att muskulaturen inte belastas optimalt under konventionell styrketräning. Detta kan vara en delförklaring till varför styrkeökningen som svar på träning ofta är liten hos personer med stroke.

New neuroimaging techniques have made it possible to examine imagery and found evidence for that imagery share similar neural correlates as in perception. Imagery can be used in different areas to enhance performance, and it is a popular technique in sports. Similar to physical practice (PP), motor imagery (MI) can result in brain plasticity. The aim of this thesis is to describe what imagery means and describe different theories of imagery. This is to further look into what impact MI has on performance in different sports, and then to further see if there are any changes in brain plasticity as a result of using MI. There is a lack of studies done on MI, performance and brain plasticity in sport. To answer the latter focus of this thesis, studies of healthy persons and patient studies using MI to improve performance and examining changes in the brain have been used. In order to do that this thesis aims to do a literature review. The results indicate that MI combined with PP can improve sport performance. It has also been showed that MI alone can be as good as PP. Most studies found that MI combined with PP can result in brain plasticity, and only one study did not found evidence for it. It has also showed that MI alone can result in brain plasticity. Future research should include larger samples, matching subjects, and comparing the effects of MI in several kinds of sports.

Imagética motora é um processo mental que produz modulações na amplitude dos sinas de eletroencefalogramas em progresso. Os padrões presentes nestas modulações podem ser usados para classificar este processo mental, mas a identificação destes padrões não é uma tarefa trivial, porque eles estão presentes em bandas de frequências que são específicas para cada pessoa. Neste trabalho, apresenta-se um novo método para selecionar as bandas de frequência específicas para cada pessoa baseado na arquitetura do método Filter Bank Common Spatial Pattern. Para selecionar as bandas de frequência mais relevantes para cada pessoa, o método proposto aplica uma busca exaustiva para encontrar o melhor subconjunto de bandas de frequência contendo os padrões mais discriminativos dentro de um espaço de busca restrito a um tamanho fixo para este subconjunto. Esse tamanho é determinado usando validação cruzada e o método Sequential Forward Floating Selection. O método proposto foi avaliado usando a base de dados pública 2b da BCI Competition IV, mostrando melhores resultados do que todos os métodos também avaliados nessa base de dados. / Motor imagery is a mental process that when performed, produces modulations in the amplitude of ongoing electroencephalogram signals. These modulations happen following a series of patterns that can be used to classify this mental process, but the detection of those patterns is not a trivial task, because they occur in frequency bands that are specific for each person. In this work, we present a method to select these subject-specific frequency bands based on the arquitecture of the Filter Bank Common Spatial Pattern approach. To select the most relevant frequency bands for each person, our method uses an exhaustive search to find the best subset of frequency bands containing the most discriminative patterns, but with one restriction, the search space is restricted to find a subset with a fixed number of frequency bands. The number is determined using cross-validation and the Sequential Forward Floating Selection method. We demonstrate that, using the data set 2b of the BCI Competition IV, our method is more accurate than current methods evaluated on the same data set.