Electroencephalography (EEG) was formerly confined to clinical and research settings with the necessary hardware costing thousands of dollars. In the last five years a number of companies have produced simple electroencephalograms, priced below $300 and available direct to consumers. These have stirred the imaginations of enthusiasts and brought the prospects of "thought-controlled" devices ever closer to reality. While these new devices were largely targeted at video games and toys, active research on enabling people suffering from debilitating diseases to control wheelchairs was being pursued. A number of neurochairs have come to fruition offering a truly hands-free mobility solution, but whether these results could be replicated with emerging low cost products, and thus become a viable option for more people is an open question. This thesis examines existing research in the field of EEG-based assistive technologies, puts current consumer-grade hardware to the test, and explores the possibility of a system designed from the ground up to be only a fraction of the cost of currently completed research prototypes.

Blast-induced traumatic brain injury and hearing loss are two of the most common forms of the “invisible wounds of war” resulting from the United States’ Global War on Terror. Several published studies have been confirming recent reports from VA healthcare centers of blast-exposed Service Members complaining of auditory problems despite having hearing that is, for all intents and purposes, normal. Most common among these complaints is problems understanding speech in crowded and noisy situations. We hypothesized that problems with speech comprehension could either be the result of 1) damage to sensory areas in the auditory periphery or 2) blast-induced traumatic brain injury (TBI) to cortical networks associated with the processing of attention, memory, and other executive functions related to the processing of speech and linguistic information. In Chapter 1 of this thesis, we found that in a population of blast-exposed Veteran Service Members, problems with speech comprehension in noise were due to cognitive deficits likely resulting from issues related to their post-traumatic stress disorder (PTSD) diagnoses. Chapter 2 takes and expanded look at the topics of Chapter 1 with a more comprehensive battery of audiological, electrophysiological, and neuropsychological tests in active duty Service Members with and without a history of blast exposure. Unlike in veterans with PTSD, we found subclinical levels of peripheral auditory dysfunction, as well as evidence of compromised neural processing speed in the blast-exposed group. These deficits were also consistent with poorer performance on a standardized speech-in-noise test and lower self-reported ratings on an abbreviated version of the Speech, Spatial, and Qualities (SSQ) of Hearing questionnaire (Gatehouse and Noble, 2004). In Chapter 3,we modeled outcomes from the SSQ survey using objective measures of hearing function related to audibility, distortion of the neural representation of sound, attention, age, and blast status. We found for all subjects age and high frequency hearing thresholds predicted survey outcomes related to everyday listening ability. Within non-blast controls, however, measures of attention could differentiate between good and exceptional listening ability. Results from blast exposed subjects remained inconclusive. Collectively, these findings highlight the need for audiologists to take into account more than audiometric measures alone when diagnosing and treating hearing dysfunction in this unique and specialized patient population.

The current research project consists of three experiments on motor asymmetry tasks. Electroencephalogram (EEG) was applied to examine neural activation patterns in coincidence with motor performance across ages. A total of 48 right-handed participants were recruited and conducted the Purdue Pegboard test, graphic test, and aiming test. The three motor tasks were designed to assess functional asymmetry at behavioral level. Brain activities were acquired through EEG while performing the tasks. Measures of EEG signals were mean relative power of 12 electrodes. To examine movement-related brain activity, Mu rhythm within a frequency band of 8 Hz to 12 Hz was filtered with a high-pass of 1 Hz and a low-pass of 50 Hz. Statistical analyses aimed to examine effects of aging on motor asymmetry and hemispheric asymmetry. One-way repeated ANOVA was first conducted on each age group separately to identify motor asymmetry characterized by a significant difference between left hand and right hand. In addition, two-way (Age × Hand) mixed design ANOVA was implemented to examine whether age-related changes in motor asymmetry were significant. The three motor tasks indicated significant motor asymmetry in young adults, with the dominant (right) hand having an advantage over the nondominant (left) hand. However, no significant results were identified in the manual performance of older adults, suggesting reduction of motor asymmetry in aging population. In addition, the two-way ANOVA identified a significant interaction effect between age and hand, which further confirmed the significant changes in motor asymmetry over the life span. Hemispheric activation indicated consistent pattern of changes with motor performance. Hemispheric activation of young adults was strongly lateralized during motor performance, with the frontal regions in the contralateral hemisphere being more activated than the corresponding regions in the ipsilateral hemisphere. On the other hand, hemispheric activation of older adults indicated increased ipsilateral activation which resulted in bilateral and symmetric patterns. The current research substantiated hypothesis proposed in previous motor behavior research that reduced motor asymmetry linked with less hemispheric lateralization in older adults. Based on evidence from motor behavior and neural connectivity, we concluded that aging reduces asymmetries at both behavioral and neural levels.

The rapid advancements in the field of machine learning and artificial intelligence has led to the emergence of technologies like the Brain Computer Interface (BCI), which has revolutionized rehabilitation protocols. However, given the neural basis of BCIs and the dependence of its performance on cognitive factors, BCIs may be used to characterize the functional capacity of the user. A resting state segment can also be considered for characterization of the functional network integrity, creating a two part framework that probes the functional networks and their cognitive manifestations. This thesis explores such a two part framework using a simultaneous EEG-fMRI setup on a healthy population. The BCI accuracies for all subjects increased over the course of the scan and is thought to be due to learning processes on the subject's part. Since such learning processes require cognitive faculties such as attention and working memory, these factors might modulate the BCI performance profile, making it a potential metric for the integrity of such cognitive factors. The resting state analysis identified four EEG Microstates that have been previously found to be associated with verbal, visual, saliency and attention reorientation tasks. The proportion of each microstate that composed the corresponding fMRI resting state networks (RSN) were identified, opening up the potential for predicting fMRI-based RSN information, from EEG microstates alone. The developed protocol can be used to diagnose potential conditions that negatively affect the functional capacity of the user by using the results from this study as healthy control data. This is the first known BCI based system for characterization of the user's functional integrity, opening up the possibility of using BCIs as a metric for diagnosing a neuropathology. / Thesis / Master of Applied Science (MASc)

<p> The present study has two objectives. The first is to apply a reliable and valid technique of eeg frequency analysis to the measurement of the human alpha rhythm. The second objective is to find a chemical agent which will alter an individual's dominant occipital frequency 2 Hz from its resting frequency. The techniques used are: dextrose ingestion, fasting, oxygen inhalation, hyperventilation, carbon dioxide inhalation, diamox, alcohol, librium and dexedrine. The treatments which did produce a 2 Hz shift in dominant frequency also produced new peaks in other parts of the frequency spectrum. Evidence is presented which suggests that the alpha rhythm can be made to fluctuate over a very narrow frequency range (approx. 1 Hz ).</p> / Thesis / Master of Arts (MA)

Unlike other domains of cognition, the acquisition of procedural skills (e.g., the "how to" of memory) is spared by age. However, the consolidation (i.e., the transformation from labile memory to long-term storage) of this type of memory is compromised by age. Optimal memory consolidation for procedural skills is dependent on sleep. Sleep is also negatively impacted by normal, healthy aging. Recent research has identified the neural markers of the lost benefit of sleep for reduced memory consolidation with age. While this is relatively well-established for procedural memory, and for cognitively simple motor skills, the impact of age-related changes in sleep on cognitively complex procedural memory consolidation (i.e., novel cognitive strategies required for "problem-solving skills") remains to be investigated. Furthermore, reduced capacity to solve problems with age has serious mental health-related consequences, including increased depression and suicide attempts, as well as disability in depressed, cognitively impaired older adults. Moreover, problem-solving therapy has been found to improve quality of life in older adults. As such, the aims of these series of studies were to investigate: 1) the behavioural consequences of age on sleep-dependent memory consolidation, 2) identify the electrophysiological markers during sleep of the lost benefit of sleep, 3) identify the age-related changes in brain structure and how this relates to and behavioural outcomes and sleep, and, 4) identify the impact of age on sleep-dependent consolidation of the memory trace for problem-solving skills. Using an innovative combination of EEG, MRI, and behavioural testing in healthy young and older adults, these series of studies revealed novel insights into the breakdown of the normal processes that occur during sleep that support memory. The main objective of this thesis is to identify the neural markers of the very earliest signs under optimal conditions of age-related cognitive decline for problem-solving skills. Investigating the neurophysiological and behavioral consequences of age-related changes in sleep, and their impact on problem-solving skills, will help reveal therapeutic targets for future research that will improve quality of life for seniors. Furthermore, this research will ultimately lead to the development of early interventions targeting sleep that could delay or lessen the severity of the onset of clinically significant cognitive impairment; as those who sleep better, may also age better cognitively.

Recent advances in neuroimaging and electromagnetic measurement technology have permitted the exploration of structural and functional brain alterations associated with chronic pain. A number of cortical and subcortical brain regions have been found to be involved in the experience of chronic pain (Baliki et al., 2008; Jensen et al., 2010). Evidence suggests that living with chronic pain shapes the brain from both an architectural and a functional perspective, and that individuals living with chronic pain display altered brainwave activity even at rest. Quantitative EEG (qEEG) is a method of spectral analysis that utilizes a fast Fourier transform algorithm to convert analog EEG signals into digital signals, allowing for precise quantification and analysis of signals both at single electrode locations and across the scalp as a whole. An important advance that has been permitted by qEEG analysis is the development of lifespan normative databases against which individual qEEGs can be compared (Kaiser, 2006; Thatcher et al, 2000). Pilot data utilizing qEEG to examine brainwave patterns of individuals with chronic pain have revealed altered EEG activity at rest compared to age- and gender-matched healthy individuals (Burroughs, 2011). The current investigation extended the findings of the pilot study by utilizing qEEG to examine a larger sample of individuals with chronic pain. Individuals with chronic pain displayed significantly reduced slow wave activity in frontal, central, and temporal regions. Findings will be presented in terms of specific patterns of altered EEG activity seen in individuals with chronic pain.

Most previous research has explored how words are processed in isolation. However, reading is a complex process where an interplay of various factors affects word identification. Moreover, previous research has mainly focused on alphabetical languages, so extension of the existent findings to non-alphabetical languages is crucial. The current dissertation uses natural reading paradigms to study eye-movements and neurophysiological correlates of the statistical properties of words that affect word recognition during natural reading in English and Chinese. Chapter 2 concerns the time-courses of word frequency and semantic similarity effects in the reading of English derived words. Previous research pointed to a paradox where behavioural experimental techniques showed earlier signatures of these properties than neuro-imaging techniques. By combining eye-tracking and EEG and applying analytical techniques that target the onset of these effects, this study aims at investigating this paradox. Results still show that neurophysiological responses are either largely absent or appear at the same time as shown in eye-movement data. Chapter 3 shows that the existence of spelling errors negatively impacts the recognition of correct spellings in Chinese. This is revealed by the “spelling entropy effect”, which measures the uncertainty about choosing between correct and alternative spelling variants. This is the first study that used co-registration of eye-tracking and EEG to explore the behavioral and neurophysiological signatures of this uncertainty. Chapter 4 studies how segmentation probabilities influence word segmentation and identification when reading Chinese. The results reveal that space becomes beneficial only when located at places where segmentation probability is considered high. This study is among the first to show beneficial effects of spacing at the sentence level and demonstrates how segmentation probabilities play a crucial role in Chinese word segmentation. Cumulatively, the results obtained point to the existence of numerous factors involved in word identification in both alphabetic and logographic languages, which should be explored using natural reading experimental paradigms, such as co-registration of EEG and eye-tracking, for obtaining a multifaceted view of word recognition processes. / Thesis / Doctor of Philosophy (PhD)

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