Previous investigations comparing direct versus indirectly cued movements have consistently shown that indirectly cued movements take longer to prepare (Neely and Heath, 2010) and involve the recruitment of additional brain areas (Connolly et al., 2000). This increase in processing time has been associated with the additional cognitive transformations required of the task (Neely and Heath, 2010). In the present study we investigated whether differences between direct versus indirectly cued movements are also reflected in the time course of motor preparation. Participants performed a targeting task, moving directly to the location of a visual cue (i.e., directly cued movement) or to a location that differed by 60˚, 90˚, or 120˚ with respect to the visual cue provided (i.e., indirectly cued movements). Participants were instructed to initiate their movements concurrently with an anticipated go-signal. To examine the time course of motor preparation, a startling acoustic stimulus (SAS, 124dB) was randomly presented 150 ms, 500 ms, or 1000 ms prior to the go-signal. Results from the startle trials revealed that the time course of motor preparation was similar regardless of the angle of rotation required and hence whether it was a direct or indirectly cued trial. Specifically, motor preparation was delayed until less than 500 ms prior to movement initiation for both direct and indirectly cued movements. These findings indicate that similar motor preparation strategies are engaged for both types of cued movements, suggesting that the time to prepare a motor response may be similar regardless of whether a cognitive transformation is required.

Previous investigations comparing direct versus indirectly cued movements have consistently shown that indirectly cued movements take longer to prepare (Neely and Heath, 2010) and involve the recruitment of additional brain areas (Connolly et al., 2000). This increase in processing time has been associated with the additional cognitive transformations required of the task (Neely and Heath, 2010). In the present study we investigated whether differences between direct versus indirectly cued movements are also reflected in the time course of motor preparation. Participants performed a targeting task, moving directly to the location of a visual cue (i.e., directly cued movement) or to a location that differed by 60˚, 90˚, or 120˚ with respect to the visual cue provided (i.e., indirectly cued movements). Participants were instructed to initiate their movements concurrently with an anticipated go-signal. To examine the time course of motor preparation, a startling acoustic stimulus (SAS, 124dB) was randomly presented 150 ms, 500 ms, or 1000 ms prior to the go-signal. Results from the startle trials revealed that the time course of motor preparation was similar regardless of the angle of rotation required and hence whether it was a direct or indirectly cued trial. Specifically, motor preparation was delayed until less than 500 ms prior to movement initiation for both direct and indirectly cued movements. These findings indicate that similar motor preparation strategies are engaged for both types of cued movements, suggesting that the time to prepare a motor response may be similar regardless of whether a cognitive transformation is required.

Increasing evidence supports the use of physical activity for modifying brain activity and overall neurological health (Hillman et al, 2008). Specifically, aerobic exercise appears to improve cognitive efficacy with regards to decisional oddball tasks shown through the P300, whose amplitude and latency is augmented (Magnié et al., 2000). Furthermore, the effects of an acute bout of aerobic exercise on cardiovascular function are well established and are sustained following exercise cessation. Based on these findings, we proposed that (1) an acute bout of exercise may modulate movement-related cortical excitability within motor areas and (2) that transient effects would be sustained as long as heart rate (HR) remained elevated. Subjects (n=23) were placed in a soundproof booth and instructed to perform a self-paced unimanual ballistic wrist extension every 3-6 seconds of the right wrist while holding a moveable handle. The motion involved a brisk contraction followed by relaxation and positional reset, collected continuously for approximately 8 minutes. Electroencephalography was used to measure movement-related cortical activity of the Bereitschaftspotential (BP) time-locked to onset of muscle activity associated with movement. The BP is a slow negative self-paced movement related cortical potential that precedes movement by approximately 1500ms. Current work commonly separates the BP into 3 main components early, late, and re-afferent Potentials. The early BP is representative of motor preparation of supplementary motor area (SMA) activity while the late component is representative of motor execution from primary motor cortex (M1). Early and late components are often distinguished by a a characteristic change in slope; where the early BP is a slow negative rise and the late components a steeper negative deflection beginning approximately 500ms prior to movement onset. Broken down further the late component consists of a portion of negative slope before giving rise to a peak approximately 100ms after movement onset known as the motor potential (MP). Following baseline measures, subjects performed 20 minutes of aerobic exercise at a moderate intensity (70% of age-predicted maximum heart rate) on a recumbent cycle ergometer. After the cessation of exercise, BP measures were recorded at two time points: immediately post-exercise (Post) and following a return to iv baseline HR (Post[Rest]) and two additional measures separated by 15 minutes each (Post[Rest2] and Post[Rest3]) which was, on average, 45 minutes after the cessation of exercise. Electromyography (EMG) was employed over the extensor carpi radialis muscle belly to describe muscle burst activity and onset characteristics. Results determined that Early but not Late BP was influenced by aerobic exercise. This early movement related cortical adaptation is indicative of enhanced processing within supplementary motor area. Moreover, this effect was sustained for up to an hour and 15 minutes following exercise cessation. This data is suggestive that aerobic exercise influences on motor related cortical excitability is not driven by an aerobic exercise effect and is more indicative of a delayed neurotransmitter effect.

Increasing evidence supports the use of physical activity for modifying brain activity and overall neurological health (Hillman et al, 2008). Specifically, aerobic exercise appears to improve cognitive efficacy with regards to decisional oddball tasks shown through the P300, whose amplitude and latency is augmented (Magnié et al., 2000). Furthermore, the effects of an acute bout of aerobic exercise on cardiovascular function are well established and are sustained following exercise cessation. Based on these findings, we proposed that (1) an acute bout of exercise may modulate movement-related cortical excitability within motor areas and (2) that transient effects would be sustained as long as heart rate (HR) remained elevated. Subjects (n=23) were placed in a soundproof booth and instructed to perform a self-paced unimanual ballistic wrist extension every 3-6 seconds of the right wrist while holding a moveable handle. The motion involved a brisk contraction followed by relaxation and positional reset, collected continuously for approximately 8 minutes. Electroencephalography was used to measure movement-related cortical activity of the Bereitschaftspotential (BP) time-locked to onset of muscle activity associated with movement. The BP is a slow negative self-paced movement related cortical potential that precedes movement by approximately 1500ms. Current work commonly separates the BP into 3 main components early, late, and re-afferent Potentials. The early BP is representative of motor preparation of supplementary motor area (SMA) activity while the late component is representative of motor execution from primary motor cortex (M1). Early and late components are often distinguished by a a characteristic change in slope; where the early BP is a slow negative rise and the late components a steeper negative deflection beginning approximately 500ms prior to movement onset. Broken down further the late component consists of a portion of negative slope before giving rise to a peak approximately 100ms after movement onset known as the motor potential (MP). Following baseline measures, subjects performed 20 minutes of aerobic exercise at a moderate intensity (70% of age-predicted maximum heart rate) on a recumbent cycle ergometer. After the cessation of exercise, BP measures were recorded at two time points: immediately post-exercise (Post) and following a return to iv baseline HR (Post[Rest]) and two additional measures separated by 15 minutes each (Post[Rest2] and Post[Rest3]) which was, on average, 45 minutes after the cessation of exercise. Electromyography (EMG) was employed over the extensor carpi radialis muscle belly to describe muscle burst activity and onset characteristics. Results determined that Early but not Late BP was influenced by aerobic exercise. This early movement related cortical adaptation is indicative of enhanced processing within supplementary motor area. Moreover, this effect was sustained for up to an hour and 15 minutes following exercise cessation. This data is suggestive that aerobic exercise influences on motor related cortical excitability is not driven by an aerobic exercise effect and is more indicative of a delayed neurotransmitter effect.

Previous investigations comparing direct versus indirectly cued movements have consistently shown that indirectly cued movements take longer to prepare (Neely and Heath, 2010) and involve the recruitment of additional brain areas (Connolly et al., 2000). This increase in processing time has been associated with the additional cognitive transformations required of the task (Neely and Heath, 2010). In the present study we investigated whether differences between direct versus indirectly cued movements are also reflected in the time course of motor preparation. Participants performed a targeting task, moving directly to the location of a visual cue (i.e., directly cued movement) or to a location that differed by 60˚, 90˚, or 120˚ with respect to the visual cue provided (i.e., indirectly cued movements). Participants were instructed to initiate their movements concurrently with an anticipated go-signal. To examine the time course of motor preparation, a startling acoustic stimulus (SAS, 124dB) was randomly presented 150 ms, 500 ms, or 1000 ms prior to the go-signal. Results from the startle trials revealed that the time course of motor preparation was similar regardless of the angle of rotation required and hence whether it was a direct or indirectly cued trial. Specifically, motor preparation was delayed until less than 500 ms prior to movement initiation for both direct and indirectly cued movements. These findings indicate that similar motor preparation strategies are engaged for both types of cued movements, suggesting that the time to prepare a motor response may be similar regardless of whether a cognitive transformation is required.

Synchronizing hand and foot movements under reactive versus predictive control results in differential timing structures between the responses. Under reactive control, where the movement is externally triggered, the electromyographic (EMG) responses are synchronized, resulting in the hand displacement preceding the foot. Under predictive control, where the movement is self-paced, the motor commands are organized such that the displacement onset occurs relatively synchronously, requiring the EMG onset of the foot to precede that of the hand. The current study used a startling acoustic stimulus (SAS), which is known to involuntarily trigger a prepared response, to investigate whether these results are due to differences in the pre-programmed timing initiation structure of the responses. Participants (n=17) performed isolated and synchronous movements of the right heel and right hand under both reactive and predictive modes of control. The reactive condition involved a simple reaction time (RT) task where participants performed the required movement in response to a visual go-signal. The predictive condition involved an anticipation-timing task where participants initiated the required movement coincidently with a sweeping clock hand reaching a target. On a subset of trials, a SAS (114 dB) was presented 150 ms prior to the imperative stimulus. Results from the SAS trials revealed that while the differential timing structures between the responses was maintained under both reactive and predictive control, the EMG onset asynchrony under predictive control was significantly smaller following the SAS. Additionally, there was no difference in the effect of the SAS when the movements were performed in isolation versus synchronously. Together, these results suggest that the timing between the responses, which differs between the two control modes, is pre-programmed; however, under predictive control, an increase in cortical activation from the SAS may have shortened the between-limb delay.

No description available.

[Truncated abstract] There is overwhelming evidence that PD leads to impairments in executing voluntary movements. However, it is less clear whether it also leads to impairment in the preparation of movement. The current investigation first aims to further our understanding of motor preparation in people with PD. Two techniques are commonly used to assess motor preparation. These are the manipulation of response complexity and cueing response-related information in advance of the imperative signal. They were both incorporated into a motor task in which participants performed two-movement sequences on a response board. In Experiment 1, people with PD (comprising two groups one on their anti-Parkinsonian medication, and the other following a delay in its normal administration) showed patterns in their motor performance that was similar to healthy age-matched adults. They showed lengthening in their reaction time (RT) with increased response complexity, indicating that the sequences were prepared before their initiation. In addition, both of the PD groups, as well as the healthy adult group, showed shorter RTs with valid cueing and longer RTs with invalid cueing relative to the neutral cue condition. In response to a part-invalid cue (with both valid and invalid information) all three groups had very similar RTs to that in the neutral cue condition. ... in the third experiment, participants were first presented with a sequence to perform, and then, while initiating and executing that sequence, they were presented with a second sequence, providing either valid or invalid visual information about the twomovement sequence. It was expected that if invalid visual information evokes a stronger obligatory response in people with PD, then these participants would experience greater difficulties ignoring such information. This was not found to be the case. Rather the PD group showed a similar pattern of performance to the healthy adults. This indicates that they were able to ignore visual information when it was invalid and unhelpful, and so suggests that people with PD use external information strategically. The results presented in this thesis suggest that motor preparation is largely intact in people with PD. Motor preparation may, however, be incomplete under reduced visual information. Furthermore, while visual information may be particularly important to people with PD, it does not seem to evoke a stronger obligatory response than in healthy adults. Rather, people with PD seem to use external information strategically.

The process of movement execution can be separated into two sections; the foreperiod and the response time. The foreperiod represents the time between the warning signal (WS) and the presentation of the imperative “go” signal, and the response time incorporates both the reaction time (RT) and the movement time (Schmidt & Lee, 2011). Transcranial magnetic stimulation (TMS) was used to probe corticospinal excitability (CE) which has been measured in a variety of RT tasks during both the foreperiod and the response time periods. The purpose of the two studies in this thesis was to measure when and at what rate changes in CE occur in both simple and complex tasks. The results of the first experiment indicated that CE levels quickly increased from baseline with the presentation of the WS. This was followed by a holding period in which CE was held constant until a decline in CE occurred prior to the presentation of the IS. This decline was followed by a rapid increase in CE as the movement was initiated and released. Importantly, even though levels of CE were decreasing relative to the start of the decline, participants were still in a heightened state as they prepared to release their movements. Furthermore, it is suggested that selective inhibitory control mechanisms were at least partly responsible for the decline prior to the IS. The results of the second experiment indicated that MEP amplitudes in a simple task were significantly larger compared to those in a complex task relative to both the IS and the onset of electromyography. These findings suggest that simple and complex tasks achieve differing levels of corticospinal excitability, and it is suggested that the complex requires the use of the cerebellum, which suppresses excitatory projections to the thalamus, and consequently to the motor cortex.

Submitted by Daniely Januário (daniely.januario@gmail.com) on 2018-03-02T12:16:08Z No. of bitstreams: 1 anaelliaparecidanogueiracampos.pdf: 15440844 bytes, checksum: a786f15fa4f523f31128b53fda8765c2 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2018-03-02T12:24:59Z (GMT) No. of bitstreams: 1 anaelliaparecidanogueiracampos.pdf: 15440844 bytes, checksum: a786f15fa4f523f31128b53fda8765c2 (MD5) / Made available in DSpace on 2018-03-02T12:24:59Z (GMT). No. of bitstreams: 1 anaelliaparecidanogueiracampos.pdf: 15440844 bytes, checksum: a786f15fa4f523f31128b53fda8765c2 (MD5) Previous issue date: 2012-12-21 / PROQUALI (UFJF) / O objetivo desse estudo foi investigar por meio da estimulação magnética transcraniana (EMT), se a excitabilidade córtico-espinhal durante a preparação motora é afetada pela valência emocional de um estímulo com o qual se irá interagir. Além disso, avaliamos se o efeito da modulação emocional sobre a excitabilidade córtico-espinhal era específica para o músculo diretamente envolvido na tarefa. Dez participantes foram orientados a realizar uma tarefa que incluía duas condições: mover (condição AÇÃO) ou observar (condição NÃO-AÇÃO) objetos com diferentes valências (agradável, neutro e desagradável). A ordem de apresentação das condições e das valências foi aleatória, compreendendo quatro blocos, sendo dois de cada condição. O peso de todos os objetos foi contrabalançado e apresentado dentro de copos transparentes a fim de uniformizar o tipo de preensão manual que os participantes teriam que utilizar para segurá-los. O início de cada tentativa foi marcado pela apresentação do estímulo. Dado a apresentação de cada estímulo, 3s depois um sinal resposta acendia, indicando que o participante deveria mover ou apenas observar, dependendo da condição experimental. O pulso de EMT foi aplicado sobre o córtex motor primário em 500 ou 250 ms antes do sinal resposta, de forma aleatória. O potencial evocado motor (PEM) foi medido através do registro do sinal eletromiográfico dos músculos: primeiro interósseo dorsal (PID) e abdutor do dedo mínimo (ADM). Uma ANOVA para medidas repetidas de três fatores foi utilizada para avaliar o efeito da emoção em cada um dos músculos. Na condição AÇÃO, a ANOVA revelou uma interação condição x valência (p = 0,003) para o músculo PID. A amplitude do PEM foi maior para a categoria desagradável, quando comparado com a neutra e agradável. Além disso, a amplitude do PEM para a categoria agradável foi menor do que a neutra. Não houve efeito significativo da valência na condição NÃO-AÇÃO. Um efeito de valência entre as condições também foi encontrado. A amplitude do PEM para a categoria desagradável foi maior na condição AÇÃO do que na NÃO-AÇÃO. O contrário ocorreu para a categoria agradável, onde a amplitude do PEM foi menor na condição AÇÃO, quando comparado com a NÃOAÇÃO. Para o ADM, não houve efeito significativo entre as categorias emocionais nem entre as condições (p = 0,76). Concluímos que a atividade preparatória que antecede a preensão de um estímulo, medida pela excitabilidade córtico-espinhal, é afetada por seu valor emocional. A modulação emocional sobre a excitabilidade é músculo-específica. / The aim of this study was to examine by means of Transcranial Magnetic Stimulation (TMS) if the corticospinal excitability (CSE) is affected by the emotional valence of the stimulus which with one is about to grab. We also examined if effect of emotional modulation upon CSE is specific to the muscle directly enrolled in the task. Ten participants were instructed to perform a task with two experimental conditions: to grasp (ACTION condition) or just to look (NO-ACTION condition) at objects with different valences (pleasant, neutral and unpleasant). Conditions and valence order were randomly presented within four blocks. Objects were balanced in weight and placed inside transparent cups to prompt a similar grip among trials. Trials began with the stimulus presentation. After stimulus presentation, a go signal was turned on 3 s later indicating that the participant should move or just observe, depending on the experimental condition. TMS was applied over the participant primary motor cortex at 500 or 250 ms before the go signal, randomly. Motor evoked potentials (MEP) were measured by recording the electromyographic signal from first dorsalis interosseous - FDI and abductor digiti minimi - ADM muscles. Tree-way ANOVA was conducted to evaluate the emotional effect for each muscle. In ACTION condition, the ANOVA revealed a condition x valence interaction (p = 0.003) for FDI. The MEP was larger for unpleasant compared to neutral and pleasant category. Also, MEP amplitude for pleasant was lower than neutral category. There was no significant effect for FDI in NO-ACTION condition. Furthermore, a significant valence effect across conditions (ACTION and NO-ACTION) was also found: higher MEP amplitudes were found for the unpleasant category in ACTION condition as compared to NON-ACTION condition. The reverse was true for the pleasant category: lower MEP amplitudes were found in the ACTION as compared to NON-ACTION condition. For the ADM, there was neither a significant effect among emotional categories nor across conditions (p = 0.76). In conclusion, we showed here that the preparatory activity preceding the grasping of a stimulus, as measured by corticospinal excitability, is affected by its emotional value. In other words, our findings show a muscle specific modulation of corticospinal excitability during motor preparation depending on the valence of the stimuli to be grasped.