Dissertation (Ph.D.) --University of Texas Graduate School of Biomedical Sciences at San Antonio, 2008. / Vita. Includes bibliographical references.

Ideomotor theory holds that motor plans producing action and the sensory effects of the actions are cognitively represented in a functionally similar way. The response-effect (R-E) association is considered bidirectional and automatic in nature. The current research project was designed to test the hypothesized bidirectional nature of R-E associations by determining if motor codes were activated following perception of an effect. The automaticity of motor code activation was investigated via TMS–induced motor evoked potentials (MEPs) following the presentation an after-effect. To this end, participants completed a training phase in which they learned a specific R-E association. During the testing phase, the effects were presented prior to the imperative and TMS stimuli. Behavioural results replicated previous research; participants preferred to execute the response associated with the presented effect. MEP data, however, did not support the initial hypothesis. These results are discussed with relation to ideomotor theory and experimental design.

Ideomotor theory holds that motor plans producing action and the sensory effects of the actions are cognitively represented in a functionally similar way. The response-effect (R-E) association is considered bidirectional and automatic in nature. The current research project was designed to test the hypothesized bidirectional nature of R-E associations by determining if motor codes were activated following perception of an effect. The automaticity of motor code activation was investigated via TMS–induced motor evoked potentials (MEPs) following the presentation an after-effect. To this end, participants completed a training phase in which they learned a specific R-E association. During the testing phase, the effects were presented prior to the imperative and TMS stimuli. Behavioural results replicated previous research; participants preferred to execute the response associated with the presented effect. MEP data, however, did not support the initial hypothesis. These results are discussed with relation to ideomotor theory and experimental design.

Previous research and current models have proposed that the right temporoparietal junction (rTPJ) is crucially involved in the control and distinction of shared representations of action. Hitherto, this assumption has mainly been based on neuroimaging work ( (Spengler, von Cramon, & Brass, 2009); (Spengler, von Cramon, & Brass, 2010)) We tested this hypothesis, that the rTPJ is causally involved in managing shared representations by using repetitive transcranial magnetic stimulation in an offline paradigm to disrupt neural activity in this region. Using a simple imitation-inhibition task we showed that stimulation of the rTPJ led to increased reaction times when participants had to control automatic imitation of a perceived hand movement, as they had to concurrently plan and execute an opposite movement. Our study provides the first empirical evidence that the rTPJ is necessary for managing and navigating within a shared representational system. These results may also have important implications for future theorizing about the role of the TPJ region in controlling shared representations also in other domains, such as somatosensation or emotional experiences.

The thesis designs, constructs, and tests an electrically small dipole antenna probe for the measurement of electric field distributions induced by a transcranial magnetic stimulation (TMS) coil. Its unique features include high spatial resolution, large frequency band from 100 Hz to 300 kHz, efficient feedline isolation via a printed Dyson balun, and accurate mitigation of noise. Prior work in this area is thoroughly reviewed. The proposed probe design is realized in hardware; implementation details and design tradeoffs are described. Test data is presented for the measurement of a CW capacitor electric field, demonstrating the probe’s ability to properly measure conservative electric fields caused by a charge distribution. Test data is also presented for the measurement of a CW solenoidal electric field, demonstrating the probe’s ability to measure non-conservative solenoidal electric fields caused by Faraday’s law of induction. Those are the primary fields for the transcranial magnetic stimulation. Advantages and disadvantages of this probing system versus those of prior works are discussed. Further refinement steps necessary for the development of this probe as a valuable TMS instrument are discussed.

The upper extremity is often left with permanent disability following stroke and therapeutic techniques used at present have had limited success. This prospective clinical trial evaluated the effectiveness of mental practice (MP) through motor imagery (MI) a therapy technique to enhance upper extremity motor recovery after stroke. MI ability, upper extremity hand function, finger strength, and motor cortical output were examined in 18 stroke subjects (mean 67.5 years). Subjects were randomly allocated to the MP treatment group or the control group which received cognitive therapy. Both groups received their respective treatment daily for 30 minutes for a 3 week period. Assessments were performed prior to treatment, post treatment and at 3 months post treatment. Imagery ability was measured using the Kinesthetic and Visual Imagery Questionnaire (KVIQ) and mental chronometric testing. Hand function was assessed with the box and block test (BBT) and finger strength with maximum voluntary contraction (MVC). To determine the effect of MI on neural excitability, focal transcranial magnetic stimulation was applied over the primary motor cortex while participants were at rest and while they imagined themselves performing abduction of the index finger. Motor evoked potentials were recorded from the contralateral first dorsal interosseous (FDI), abductor digiti minimi (ADM) and abductor pollicis brevis (APB) muscles. Data were analyzed using multifactor and repeated measures ANOVAs with the significance level set to p < 0.05. Results showed no significant difference between groups on any of the outcome measures (p > 0.05) although all subjects improved their hand function over the study period (p < 0.05). In addition, motor threshold was found to decrease over time (p < 0.001) in all subjects demonstrating improvement in cortical motor excitability and output. Motor evoked potentials (MEPs) elicited during MI were significantly larger compared to those evoked at rest (p < 0.022). MEP amplitudes from FDI, the muscle targeted with MP, showed a significant interaction effect between time and group (p = 0.021) which reflected an increase in MEPs in the MP group over time whereas a decline occurred in the cognitive group. These findings indicate that MI enhances motor cortical output in stroke and that MP using MI appears to increase corticospinal output to the target FDI muscle. No differential effects of MP and cognitive therapy interventions were evident in terms of hand function and finger muscle strength. / Thesis (Master, Rehabilitation Science) -- Queen's University, 2008-04-25 16:23:51.775 / Heart and Stroke Foundation

Over the past decade, efforts have been made to assess the positive therapeutic effects of transcranial magnetic stimulation (TMS) by altering the excitability of the brain. We conducted a double-blind, placebo-controlled study to assess the efficacy of right prefrontal slow repetitive TMS in patients with treatment refractory major depression. This pilot study supports the therapeutic potential of rTMS in the low-frequency range of 1 Hz on right prefrontal cortex for the treatment of refractory major depression. Additional studies will be necessary to assess the efficacy of rTMS with different indices (frequency, intensity, and stimulation site) for major depression and other psychiatric diseases.

Afferent Inhibition is the reduction in motor output when Transcranial Magnetic Stimulation (TMS) of the motor cortex is preceded by peripheral nerve stimulation. Afferent inhibition can be subdivided into two circuits of Short- (SAI) and Long-Afferent Inhibition (LAI). Reliability reflects the repeatability of a measure and can be measured in terms of both absolute and relative reliability. Relative reliability refers to the ability of a measure to identify individuals on repeated testing, measured through the Intraclass Correlation Coefficient (ICC); absolute reliability is the repeatability of scores through repeated testing, measured through Standard Error of Measurement (SEM) and Smallest Detectable Change (SDC). Current literature has highlighted only the intersession reliability of SAI and LAI, but measures of the intrasession reliability are also needed. This study aims to quantify the intrasession reliability of SAI and LAI, alongside identifying the minimum number of trials needed to obtain a reliable measure. 30 healthy individuals (21.17 ± 2.84 years) took part in one session, with SAI and LAI obtained three times at 30-minute intervals. To identify the minimum number of trials required to reliably elicit SAI and LAI, relative reliability was assessed at running intervals of every 5 trials. Results indicate that SAI had moderate–high, and LAI had high-excellent relative reliability. Both SAI and LAI had high amounts of measurement error. LAI was seen to have high relative reliability when only 5 frames of data were included, whereas for SAI, ~20-30 frames of data resulted in high relative reliability. For LAI, a minimal sample size of 19 is needed to have an SDCGroup < 10, whereas for SAI, a sample size of 22 is needed to achieve the same. These results can be used to inform future work regarding the clinical utility of these measures, particularly in terms of their diagnostic ability. / Thesis / Master of Science (MSc)

No description available.

Post-concussion syndrome (PCS) is a poorly understood sequela of mild traumatic brain injury (mTBI), more commonly referred to as concussion. While PCS is known to affect a subset of individuals following injury, it remains unclear how and why specific individuals incur chronic symptoms. Concussions disrupt normal neurophysiologic function within the brain, however the neurophysiologic underpinnings of PCS are unclear. Using transcranial magnetic stimulation (TMS), it is possible to non-invasively investigate neurotransmission in clinical populations such as those with PCS by stimulating the primary motor cortex (M1) and recording motor outputs in a contralateral hand muscle. A study was conducted using TMS to measure corticospinal excitability, intracortical facilitation and inhibition, and transcallosal inhibition in M1 of a group with PCS and a non-injured, healthy control group. Greater corticospinal excitability, and specific reductions in intracortical and transcallosal inhibition were observed in the PCS group, providing evidence of impaired neurotransmitter receptor activity. Importantly, these findings differed from previous observations in recovered concussion groups using similar stimulation techniques. Furthermore, it was observed that these neurophysiological differences may relate specifically to the presence of depression symptoms rather than general concussion symptoms. The physiologic and clinical implications of the findings of this thesis are discussed, and novel research avenues warranting investigation are identified. / Thesis / Master of Science in Kinesiology