Functional neuroimaging techniques such as near-infrared spectroscopy (NIRS) have been studied in brain-computer interface (BCI) development. Previous research has suggested that the addition of a second brain-monitoring modality may improve the accuracy of a NIRS-BCI. The objective of this study was to determine whether the classification accuracies achievable by a multimodal BCI, which combines NIRS and transcranial Doppler ultrasonography (TCD) signals, can exceed those attainable using a unimodal NIRS-BCI or TCD-BCI. Nine able-bodied subjects participated in the study. Simultaneous measurements were made with NIRS and TCD instruments while participants were prompted to perform a verbal fluency task or to remain at rest, within the context of a block-stimulus paradigm. In five of nine (55.6%) participants, classification accuracies with the NIRS-TCD system were significantly higher (p<0.05) than with NIRS or TCD systems alone. Our results suggest that multimodal neuroimaging may be a promising approach towards improving the accuracy of future BCIs.

Functional neuroimaging techniques such as near-infrared spectroscopy (NIRS) have been studied in brain-computer interface (BCI) development. Previous research has suggested that the addition of a second brain-monitoring modality may improve the accuracy of a NIRS-BCI. The objective of this study was to determine whether the classification accuracies achievable by a multimodal BCI, which combines NIRS and transcranial Doppler ultrasonography (TCD) signals, can exceed those attainable using a unimodal NIRS-BCI or TCD-BCI. Nine able-bodied subjects participated in the study. Simultaneous measurements were made with NIRS and TCD instruments while participants were prompted to perform a verbal fluency task or to remain at rest, within the context of a block-stimulus paradigm. In five of nine (55.6%) participants, classification accuracies with the NIRS-TCD system were significantly higher (p<0.05) than with NIRS or TCD systems alone. Our results suggest that multimodal neuroimaging may be a promising approach towards improving the accuracy of future BCIs.

<p>In this work, I examine the problem of rapid imaging of stroke and present ultrasound-based approaches for addressing it. Specifically, this dissertation discusses aberration and attenuation due to the skull as sources of image degradation and presents a prototype system for simultaneous 3D bilateral imaging via both temporal acoustic windows. This system uses custom sparse array transducers built on flexible multilayer circuits that can be positioned for simultaneous imaging via both temporal acoustic windows, allowing for registration and fusion of multiple real-time 3D scans of cerebral vasculature. I examine hardware considerations for new matrix arrays--transducer design and interconnects--in this application. Specifically, it is proposed that signal-to-noise ratio (SNR) may be increased by reducing the length of probe cables. This claim is evaluated as part of the presented system through simulation, experimental data, and in vivo imaging. Ultimately, gains in SNR of 7 dB are realized by replacing a standard probe cable with a much shorter flex interconnect; higher gains may be possible using ribbon-based probe cables. In vivo images are presented depicting cerebral arteries with and without the use of microbubble contrast agent that have been registered and fused using a search algorithm which maximizes normalized cross-correlation. </p><p>The scanning geometry of a brain helmet-type system is also utilized to allow each matrix array to serve as a correction source for the opposing array. Aberration is estimated using cross-correlation of RF channel signals followed by least mean squares solution of the resulting overdetermined system. Delay maps are updated and real-time 3D scanning resumes. A first attempt is made at using multiple arrival time maps to correct multiple unique aberrators within a single transcranial imaging volume, i.e. several isoplanatic patches. This adaptive imaging technique, which uses steered unfocused waves transmitted by the opposing or "beacon" array, updates the transmit and receive delays of 5 isoplanatic patches within a 64°×64° volume. In phantom experiments, color flow voxels above a common threshold have increased by an average of 92% while color flow variance decreased by an average of 10%. This approach has been applied to both temporal acoustic windows of two human subjects, yielding increases in echo brightness in 5 isoplanatic patches with a mean value of 24.3 ± 9.1%, suggesting such a technique may be beneficial in the future for improving image quality in non-invasive 3D color flow imaging of cerebrovascular disease including stroke.</p><p>Acoustic window failure and the possibility of overcoming it using a low frequency, large aperture array are also examined. In performing transcranial ultrasound examinations, 8-29% of patients in a general population may present with window failure, in which it is not possible to acquire clinically useful sonographic information through the temporal acoustic window. The incidence of window failure is higher in the elderly and in populations of African descent, making window failure an important concern for stroke imaging through the intact skull. To this end, I describe the technical considerations, design, and fabrication of low-frequency (1.2 MHz), large aperture (25.3 mm) sparse matrix array transducers for 3D imaging in the event of window failure. These transducers are integrated into the existing system for real-time 3D bilateral transcranial imaging and color flow imaging capabilities at 1.2 MHz are directly compared with arrays operating at 1.8 MHz in a flow phantom with approximately 47 dB/cm0.8/MHz0.8 attenuators. In vivo contrast-enhanced imaging allowed visualization of the arteries of the Circle of Willis in 5 of 5 subjects and 8 of 10 sides of the head despite probe placement outside of the acoustic window. Results suggest that the decrease from approximately 2 to 1 MHz for 3D transcranial ultrasound may be sufficient to allow acquisition of useful images either in individuals with poor windows or outside of the temporal acoustic window by untrained operators in the field.</p> / Dissertation

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No description available.

Swallowing is a complex sensorimotor behaviour that includes precisely-timed bilateral activation and relaxation of muscles of the face, lips, tongue, cheeks, palate, larynx, pharynx and oesophagus. These events of activation and inhibition are controlled by many structures of the brain and are executed by cranial nerves that carry motor and sensory information to and from the swallowing muscles. Swallowing disorders are common sequelae of many neurological and structural disorders, including stroke, Parkinson’s disease, and head and neck cancer. Changes to swallowing physiology are also prevalent in older individuals, but these changes do not necessarily translate to dysphagia. Decreased muscle strength, changes to motor unit properties, and hypotrophic changes in skeletal muscles can result in age-related changes in swallowing physiology. In addition to muscular changes, neural changes might also change swallowing function in older subjects. The motor-learning literature presents a clear distinction between the differential applications and effects of skill- and strength-training approaches for rehabilitation of limb movement. In contrast to limb-movement rehabilitation, swallowing rehabilitation approaches consist mainly of strength training, although the pathophysiological basis for dysphagia is not always weakness. Therefore, this Phase I clinical-trial critically evaluated a unique swallowing skill training protocol in which the goal of intervention is to increase precision of motor control during swallowing. A Phase I clinical-trial was necessary to identify the appropriate protocol for inducing neurophysiological, biomechanical, and structural adaptations, to estimate effect sizes, and to identify adverse effects. The first and primary question addressed in this thesis was whether swallowing skill training would produce greater physiological effects in healthy subjects than a traditional swallowing strength training approach. In order to answer this question, three levels of assessment were included. Neurophysiological assessment consisted of delivering single-pulse transcranial magnetic stimulation (TMS) over the M1 area that sends efferent projections to the submental muscle group during a functional task of volitional saliva swallowing, and during a non-functional task of submental muscle group contraction. Biomechanical assessments consisted of pharyngeal and upper esophageal sphincter (UES) pressure measurements using pharyngeal manometry during effortful and non-effortful swallowing tasks, submental muscle activation measurements using surface electromyography (sEMG) during effortful and non-effortful swallowing tasks, and hyoid displacement using ultrasonography. Structural assessment consisted of measuring the cross sectional area of the submental muscle group. Finally, motor performance during training, and subjective ratings of the training protocols were assessed. Two skill training protocols were developed to assess the use of immediate versus delayed visual feedback in swallowing skill training. In addition, a pilot study aimed at examining the effects of increased dosage of training sessions was conducted. Forty healthy subjects (20 young, and 20 old; 20 females and 20 males) were allocated to skill and strength training groups in a counterbalanced manner. Strength training consisted of execution of the effortful swallowing technique targeting increased demand for strength. Skill training targeted precise timing and force execution during swallowing execution. Several motor-learning principles were considered in devising the training protocols, including the principles of task specificity and high intensity of training. Biofeedback was included to promote motor learning. Since the submental muscle group plays an important role in hyolaryngeal excursion, the current study utilized submental sEMG biofeedback using custom-made training software. The training protocols consisted of 1000 repetition of swallowing over a 2-week period. Subjects trained for an hour, five days a week, for 2 weeks (i.e., 10 training sessions). The extended dosage protocol included 10 subjects and comprised an additional eight sessions. The results indicated that there was a significant difference in submental activation following training, with strength training having an increase in sEMG peak amplitude in comparison to skill training. There were no other differences between groups at the 5% error level. Patterns of change were revealed when marginally significant results (0.05 < p ≤ 0.10) were investigated as well. Strength training resulted in a trend towards increased neural drive for volitional effortful-type tasks (i.e., effortful saliva swallowing, effortful water swallowing, and submental muscle contraction) as indicated by increased MEP magnitude (p = 0.07) which was consistent with significantly increased peak amplitude of submental activity measures (p < 0.001). This finding supports the task specificity principle of motor learning. Skill training resulted in no changes in MEP magnitude. There was a trend (p = 0.06) towards increased submental muscles activity during functional swallowing tasks (i.e., non-effortful swallowing) in young subjects,. Males in skill training had decreased duration of UES opening in 10 mL water effortful swallowing task (p = 0.02), a trend towards increased UES pressure in non-effortful saliva swallowing task (p = 0.07), and reduced hyoid displacement following training (p < 0.001). Changes in pharyngeal pressures were detected for skill training with delayed visual feedback that resulted in decreased pressure at mid-pharynx in effortful and non-effortful tasks (p < 0.05). No difference in submental CSA changes was detected in either training group. Both groups improved motor performance measured by data collected during the session (target hit-rate and muscle activity). The results of the pilot study that examined the effects of an extended dosage of training were difficult to interpret due to the small sample size. However, there were significant and marginally significant effects of skill training on mid-pharyngeal and UES pressure duration events. Dysphagia is common in patients with Parkinson’s disease, but no specific training programme exists for these patients, leading to the second question addressed through this research. Since movement planning is compromised due to dysfunction of the basal ganglia, providing external information for planning and executing swallowing was hypothesized to alleviate dysphagic symptoms. Ten subjects were recruited. Swallowing skill training with immediate feedback was administered for one hour every day, five days a week, for 2 weeks, similar to the training dosage and frequency in the healthy group. Biomechanical and structural changes were assessed. Swallowing skill training with immediate feedback led to an increase in submental activity in effortful swallowing tasks but not non-effortful tasks. In addition, it was found that individuals with dysphagia secondary to Parkinson’s disease have deceased submental muscle reserve relative to healthy subjects. Preliminary analysis of MEP data led to exploration of submental MEP measures between younger and older subjects. This ‘discovery’ research shed light on the third topic addressed in this thesis. There are contradicting results in the literature regarding age-related brain activity during swallowing. Since submental MEPs were included as an outcome measure in the main study, it was important to evaluate them at baseline in order to understand and interpret changes in this measure. Unlike other measures, such as pharyngeal pressure and hyoid displacement that have been documented in the literature to change with age, no similar study has been conducted to assess for differences in swallowing-related MEPs. Baseline data from the main study were analysed. Older subjects produced larger MEP magnitude in comparison to young in volitional saliva swallowing and volitional submental contraction. This finding raised some questions regarding the use of MEPs as an outcome measure, since it is not clear what constitutes a ‘positive’ change. This study documented, for the first time, the application of skill training in swallowing in a healthy and dysphagic population. Positive effects of treatment were found in the dysphagic group; an indication of negative effects was identified in the healthy group. In addition, this is the first study to compare skill to strength training in swallowing. The only significant difference between the two was significantly greater submental activation in effortful swallowing tasks following strength training in comparison to skill training; although there were some significant interactions between age and training type and gender and training type. This project represents the first Phase I clinical-trial of an innovative approach for addressing swallowing impairments. Achieving the ultimate aim of finding the most appropriate training protocol for treating individuals with a specific pathophysiological basis of dysphagia, requires the implementation of a long-term on-going research programme characterized by a staged process. This research programme sets an initial reference framework from which further projects can estimate the sample size required to answer specific questions, control for effects of age and gender and their interaction with training, increase precision in choosing assessment tools, and test new specific questions.

Background and aims: The primary motor cortex (M1) controls voluntary motor behaviours. M1 has been identified to play a major role in the execution of voluntary corticospinal tasks as well as self-initiated corticobulbar tasks. However, the involvement of M1 in more complex corticubulbar tasks, such as swallowing, is not yet fully understood. Swallowing is quite different from other voluntary motor tasks as it has both voluntary and reflexive components. The degree of M1 involvement in the pharyngeal, or more reflexive, component of swallowing is unclear. Studies investigating the role of M1 in swallowing have yielded contradictory findings regarding the specific functional contribution of M1 to swallowing. Therefore, further investigation is warranted to clarify the role of M1 in pharyngeal swallowing. Discrete saliva or water swallowing has been utilized in most studies investigating neurophysiology of swallowing in health and disease. However, individuals most frequently complete multiple, consecutive swallows during the ingestion of liquid. Biomechanical differences between discrete and continuous water swallows have been identified using videofluoroscopic swallowing study (VFSS). However, no studies have investigated the pharyngeal pressure differences between these two swallowing tasks. Additional insights into task differences may be revealed through evaluation of pharyngeal pressure utilizing pharyngeal manometry. This research programme sought to clarify the role of M1 in reflexively and volitionally initiated pharyngeal swallowing. In order to understand M1 involvement in the execution of swallowing, comparative tasks that require known dependence on M1 were also included in this research programme. This research programme addressed the biomechanical changes in motor behaviours as a result of neural disruption during the performance of a number of motor tasks. This neural disruption was intrinsically generated through application of dual task (DT) paradigm and extrinsically generated using single pulse transcranial magnetic stimulation (TMS). A secondary aim of this research programme was to identify the differences in pharyngeal pressure generation between discrete and continuous swallowing. Methods: Twenty-four right handed participants (12 males, average age= 24.4, SD= 6.3) were recruited to this research programme. A number of motor tasks that vary in complexity were tested. These tasks included: volitional swallowing, reflexive swallowing, eyebrow movement, jaw movement and finger tapping with right, left, or bilateral index fingers. Participants performed multiple trials of several tasks in each study. Repetitions of tasks during a single session may affect performance due to factors such as fatigue or practice. A baseline study was undertaken to determine within-participant variability of measures across repeated trials. Following the baseline study, the role of M1 in pharyngeal swallowing was investigated in two main studies in counter balanced order. The role of M1 in pharyngeal swallowing was evaluated by investigating swallowing parameters during neural disruption using a DT paradigm. Participants performed tasks in isolation (baseline) and with interference that consisted of pairing swallowing with comparative task that activates M1 (fingers tapping and eyebrow movement tasks). In the other study, single pulse TMS was utilized to create an electrophysiological disruption to the areas of M1 associated with muscular representation of a number of motor behaviours (swallowing tasks, jaw movement and fingers tapping tasks). Stimulation was provided to both hemispheres in random order to evaluate laterality effects. Swallowing parameters and the performance of the other motor tasks were evaluated when performed with and without electrophysiological disruption. Differences in pharyngeal pressure generation between discrete and continuous swallowing were investigated using pharyngeal manometry. Pharyngeal pressures were recorded at three locations: upper pharynx, mid-pharynx and upper esophageal sphincter (UES) during four swallowing types: discrete saliva swallowing, discrete 10 ml swallowing, volitional continuous swallowing, and reflexive continuous swallowing. The research paradigm used in this research programme identified the effect of experimental conditions on the rate and regularity of task performance. In addition, pharyngeal manometry was utilised to measure the effect of experimental conditions on the pattern of the pharyngeal pressure generation during swallowing. Within subject differences from baseline were identified by means of Repeated Measures Analyses of Variance (RM-ANOVA). Results: Initial analysis of the data revealed that repetition of tasks within a session did not affect the rate and regularity of voluntary corticospinal tasks, voluntary corticiobulbar tasks nor swallowing tasks. In addition, repeating the swallowing tasks during a session did not affect pharyngeal pressure as measured by pharyngeal manometry. When motor tasks were performed concurrently in the DT paradigm, rate and regularity of eyebrow movements were significantly decreased when paired with swallowing tasks, whereas rate and regularity of swallowing were significantly decreased when paired with left finger tapping, but not right finger tapping. However, there was no significant effect of any task on the pattern of pharyngeal pressure generation. Extrinsically generated disruption using TMS significantly reduced rate and regularity of finger tapping tasks and regularity of jaw movement and swallowing tasks. In addition, interruption of pharyngeal M1 during the volitional swallowing task produced significant increase in the duration but not the amplitude of the pharyngeal pressure. Pharyngeal pressure generation differed between swallowing types and boluses types, in that saliva swallowing produced longer pharyngeal pressure duration and lower nadir pressure than water swallows. Discrete water bolus swallowing produced longer UES opening compared to both saliva swallowing or continuous water swallowing. Conclusion: The results of this research programme provided valuable methodological information regarding the effect of trials on task performance as well as identifying pharyngeal pressure differences between discrete and continuous swallowing. In addition to the methodological contribution, this research programme expanded on previous knowledge of neural control of swallowing, in that it extended the findings regarding potential role of M1 in pharyngeal swallowing. Given the absent effect of task repetition on the performance of corticospinal and corticobulbar motor tasks, it is speculated that outcomes of research investigating the effect of experimental manipulation on motor tasks performance is due to the experimental tasks, rather than natural variance in the data. The effect of swallowing on the rate and regularity of eyebrow movement, when performed concurrently using DT paradigm, suggest bilateral functional overlapping to a significant degree between neural substrates that control swallowing and orofacial muscles. These results offer partial support of bilateral representation of swallowing in the cortex. In addition, results further revealed potential involvement of right M1 in the regulation of pharyngeal swallowing as evidenced by a disruptive effect of left finger tapping on the rate and regularity of swallowing. The results from the hemispheric TMS disruption study support the active involvement M1 in the execution of voluntary corticospinal and corticobulbar motor tasks. In addition, the current findings extended previous knowledge of neural control of pharyngeal swallowing by documenting the effect of neural disruption on the regularity and pharyngeal pressure measures during volitional and reflexive swallowing. The current programme documented potential role of M1 in the control of pharyngeal swallowing possibly by modulating the motor plan at the swallowing CPG in the brainstem. This project is the first to document pharyngeal pressure differences between discrete and continuous swallowing. These findings contribute valuable information to the swallowing literature as limited number of studies investigated the biomechanical differences between discrete and continuous liquid ingestion. This knowledge will assist clinicians and researchers in identifying the pharyngeal pressure differences between normal and abnormal swallowing in different swallowing types and ultimately guide their rehabilitation decisions. Data from this research programme will add to the existing knowledge of neurophysiology of swallowing, thereby facilitating understanding of swallowing pathophysiology which is crucial for appropriate management of swallowing disorders.

A full-sine (biphasic) pulse waveform is most commonly used for repetitive transcranial magnetic stimulation (TMS), but little is known about how variations in duration or amplitude of distinct pulse segments influence the effectiveness of a single TMS pulse to elicit a corticomotor response. Using a novel TMS device, we systematically varied the configuration of full-sine pulses to assess the impact of configuration changes on resting motor threshold (RMT) as measure of stimulation effectiveness with single-pulse TMS of the non-dominant motor hand area (M1). In young healthy volunteers, we (i) compared monophasic, half-sine, and full-sine pulses, (ii) applied two-segment pulses consisting of two identical half-sines, and (iii) manipulated amplitude, duration, and current direction of the first or second full-sine pulse half-segments. RMT was significantly higher using half-sine or monophasic pulses compared with full-sine. Pulses combining two half-sines of identical polarity and duration were also characterized by higher RMT than fullsine stimuli resulting. For full-sine stimuli, decreasing the amplitude of the halfsegment inducing posterior-anterior oriented current in M1 resulted in considerably higher RMT, whereas varying the amplitude of the half-segment inducing anterior-posterior current had a smaller effect. These findings provide direct experimental evidence that the pulse segment inducing a posterior anterior directed current in M1 contributes most to corticospinal pathway excitation. Preferential excitation of neuronal target cells in the posterior-anterior segment or targeting of different neuronal structures by the two half-segments can explain this result. Thus, our findings help understanding the mechanisms of neural stimulation by full-sine TMS.

Demencija yra vienas iš dažniausiai sutinkamų psichikos sutrikimų vyresniame amžiuje. Pastebėta, kad dalis vyresnio amžiaus pacientų, kuriems vėliau išsivysto demencija, dažniau nei bendraamžiai skundžiasi pažinimo sutrikimais, tačiau kasdieninė veikla yra nesutrikusi. Ši būklė buvo pavadinta lengvu kognityviniu sutrikimu (LKS). Neurosonografiniai tyrimai pateikia daug naudingos informacijos apie funkcinius galvos ir kaklo kraujagyslių parametrus. Tyrimo tikslas buvo nustatyti neurosonografinių galvos ir kaklo arterijų parametrų vertę prognozuojant demenciją lengvu kognityviniu sutrikimu sergantiems pacientams. Tyrimo uždaviniai: 1) ištirti LKS turinčių pacientų demografines ir klinikines charakteristikas ir įvertinti jų ir progresavimo į demenciją ryšį; 2) ištirti LKS turinčių pacientų ekstrakranijinės kraujotakos parametrus ir įvertinti jų ir progresavimo į demenciją ryšį; 3) ištirti LKS turinčių pacientų intrakranijinės kraujotakos parametrus ir įvertinti jų ir pogresavimo į demenciją ryšį; 4) ištirti LKS turinčių pacientų miego arterijų sienelių parametrus ir įvertinti jų ir pogresavimo į demenciją ryšį; 5) ištirti LKS turinčių pacientų miego arterijų aterosklerozinius požymius ir įvertinti jų ir pogresavimo į demenciją ryšį; 6) įvertinti bendrą tiriamųjų demografinių ir klinikinių charakteristikų bei neurosonografinių parametrų diagnostinę reikšmę prognozuojant progresavimą iš lengvo kognityvinio sutrikimo į demenciją. / Dementia is one of the most commonly occurring mental disorders in older age. It was noticed that some of the elderly patients who later develop dementia, more often than contemporaries complained of cognitive impairment, but daily activities were not affected. This condition was called mild cognitive impairment (MCI). Neurosonographic studies provide a lot of useful information about the functional head and neck vascular parameters. The aim of our study was to provide more information about the significance of the extra- and intracranial arterial blood flow and carotid arterial wall parameters for prediction of dementia for patients with MCI. Objectives of the study is 1) to investigate the demographic and clinical characteristics of MCI patients and to assess their relation with progression to dementia; 2) to investigate blood flow parameters of the extracranial arteries and to assess their relation with progression to dementia; 3) to investigate blood flow parameters of the intracranial arteries and to assess their relation with progression to dementia; 4) to investigate the intima-media thickness and stiffness of carotid arteries walls and to assess their relation with progression to dementia, 5) to investigate the atherosclerotic changes and to assess their relation with progression to dementia; 6) to assess the value of demographic and clinical characteristics and neurosonographic parameters for prediction of dementia.

Motion-selectivity in human visual cortex comprises a number of different cortical loci including V1, V2, V3A, V3B, hV5/MT+ and V6 (Wandell et al., 2007). This thesis sought to investigate the specific functions of V3A and sub-divisions of hV5/MT+ (TO-1 and TO-2) by using transcranial magnetic stimulation (TMS) to transiently disrupt cortical activations within these areas during psychophysical tasks of motion perception. The tasks were chosen to coincide with previous non-human primate and human neuroimaging literature; translational, radial and rotational direction discrimination tasks and identification of the position of a focus of expansion. These results assert that TO-1 and TO-2 are functionally distinct subdivisions of hV5/MT+, as we have shown that both TO-1 and TO-2 are responsible for processing translational motion direction whilst only TO-2 is responsible for processing radial motion direction. In ipsilateral space, it was found that TO-1 and TO-2 both contribute to the processing of ipsilateral translational motion. Taken in a wider context, further results also suggested that these areas may form part of a network of cortical areas contributing to perception of self-motion (heading/egomotion), as TO-2 was not found to be responsible for processing the position of the central focus of expansion (imperative for self-direction). Instead, area V3A has been implicated as functionally responsible for processing this attribute of vision. Overall it is clear that TO-1, TO-2 and V3A have specific, distinct functions that contribute towards both parallel and serial motion processing pathways within the human brain.