The P300-based brain-computer interface (BCI) is an extension of the oddball paradigm, and can facilitate communication for people with severe neuromuscular disorders. It has been shown that, in addition to the P300, other event-related potential (ERP) components have been shown to contribute to successful operation of the P300 BCI. Incorporating these components into the classification algorithm can improve the classification accuracy and information transfer rate (ITR). In this paper, a single character presentation paradigm was compared to a presentation paradigm that is based on the visual mismatch negativity. The mismatch negativity paradigm showed significantly higher classification accuracy and ITRs than a single character presentation paradigm. In addition, the mismatch paradigm elicited larger N200 and N400 components than the single character paradigm. The components elicited by the presentation method were consistent with what would be expected from a mismatch paradigm and a typical P300 was also observed. The results show that increasing the signal-to-noise ratio by increasing the amplitude of ERP components can significantly improve BCI speed and accuracy. The mismatch presentation paradigm may be considered a viable option to the traditional P300 BCI paradigm.

Non-invasive brain–computer interface (BCI) technology can restore communication for those unable to communicate due to loss of muscle control. Nonetheless, compared to augmentative and alternative communication (AAC) devices requiring muscular control, BCIs provide relatively slow communication. Therefore, implementing techniques improving BCI speed and accuracy is important. Previous studies indicate that facial stimuli elicit N170 and N400 components, in addition to the P300 component associated with P300 BCI. These additional components can increase speed and accuracy. Our study investigated the influence of image size and content using four conditions: large face, small face, large non-face, and small non-face. We predicted faces would provide higher accuracy than non-face stimuli and larger stimuli would provide higher accuracy than small stimuli. We found no significant difference in performance between conditions; however, significant waveform differences were found in each condition.

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In order to further explore the nature of anesthesia-induced unconsciousness and its relationship to nociception, investigators attempted to determine whether mismatch negativity could be detected during general anesthesia and surgery. An auditory odd-ball paradigm designed to elicit mismatch negativity was presented to ten patients during general anesthesia and surgery. Five of the ten also underwent testing in the awake state prior to surgery. Multiple EEG recordings were obtained in each patient and each condition using the BioSemi ActiveTwo 64 EEG electrode system. The anesthetic regime required only that 0.7 MAC of an inhaled agent was administered. Several methods of analysis were utilized to determine whether an MMN response could be identified: visual inspection of ERP waveforms, targeted t-tests, cluster permutation tests, and multivariate pattern analysis. Whereas deviant-related negativity was readily detected in the awake state, deviant-related negativity was not detected during surgery and general anesthesia. Results demonstrate that essential components of the MMN response are abolished during typically conducted general anesthesia even with significant surgical stimulation. These results are consistent with previous research on ERPs and anesthesia. Results cast doubt on the possibility of sensory memory related to intraoperative events. / Thesis / Master of Science (MSc)

Brain-computer interface (BCI) technology holds promise to restore the communication and control ability of individuals with severe motor disabilities (Wolpaw et al. 2002). An EEG-based BCI system that detects the P300 event-related potential (ERP) allows users to select items from a matrix consisting of letters, numbers, and function calls (after the method of Donchin et al., 2000) using brain signals rather than the brain’s normal output pathways of peripheral nerves and muscles. Our laboratory seeks to realize independent home use of P300-based BCI by severely disabled individuals. In an earlier study, we found that P300-based BCI performance (i.e., accurate classification) on test data was correlated with the test data and was not correlated with the training data (Mak et al. 2009). The present study set out

<p>Cognitive impairments in schizophrenia (SZ) include abnormalities in executive function, attention, and semantic processing. Event-related potentials (ERPs) are used as neurophysiological measures of cognitive impairment that have been shown to map onto symptom dimensions of psychotic disorders, such as schizophrenia. While much research exists on schizophrenia, less is understood about the longitudinal relationships between ERPs and symptom dimensions among individuals at risk for psychosis. Of published work in risk samples, most have been cross-sectional, leaving clinical inferences regarding longitudinal patterns non-specific. The current study aimed to bridge this gap by recording ERPs (P300, ERN, N400) across a battery of tasks within a single risk sample, and measured positive, negative, and disorganized symptom severity via the Multidimensional Schizotypy Scale (MSS). Participants exhibiting psychosis-risk were recruited from the community (N=60), and completed a baseline and 6-month follow-up assessment (n=29). The primary goal of the baseline assessment aimed to replicate ERP-symptom dimension relationships observed in the SZ literature. Effect sizes for P300-positive and ERN-negative relationships were observed to be in the same directionality as noted in the clinical SZ literature. While not statistically significant, the small effects suggest that P300 and ERN may be similarly effected by presence of positive and negative symptoms, respectively. By contrast, N400, however, was found to have an effect size directionality opposite to that reported in the literature. This finding is consistent with mixed presentation of disorganized symptoms in clinical SZ populations. The follow-up assessment aimed to examine the relationship of symptom dimensions over time in a single at-risk sample, and leveraged ERPs as potential prospective predictors of worsening of symptoms. As expected, baseline symptoms prospectively predicted corresponding symptoms at follow-up. However, only N400 amplitude at baseline correlated with disorganized symptoms at follow-up, and no ERP prospectively predicted corresponding symptom dimensions at follow-up. Overall, examining the relationship between multiple ERPs and symptom dimensions in a single sample and via a longitudinal design is a novel addition to the literature. Future research will be necessary to clarify the use of ERPs as neural biomarkers to identify and predict symptom severity over time, ultimately reducing subjectivity in clinical diagnosis and treatment. </p>

This study examined the effect of acute exercise on food motivation, energy intake, and total physical activity in normal-weight and obese women. Participants of both groups were matched (except for Body Mass Index) and conditions (exercise vs. non-exercise) were randomized and counter-balanced. Eighteen normal-weight and 17 obese women completed an exercise and non-exercise day, each performed on the same day of the week. Exercise was performed on a motor-driven treadmill at 3.8 mph and 0% grade for 45 continuous minutes. To test for food motivation, participants were shown a continuous stream of pictures of food and flowers (control) while neural activity was monitored. Data were analyzed using a 2-group x 2-exercise condition x 2-picture type repeated measures analysis of covariance on event-related potential (ERP) amplitude and latency. Dietary records were analyzed using the Food Processor SQL nutrition software. Physical activity was monitored using a GT1M accelerometer. For both groups under both conditions, ERP amplitude was higher and latency was lower for food pictures compared to flower pictures. When normal-weight and obese women were combined, there was a significant condition*picture type interaction for late positive potential (P=0.04) with participants showing less neurological response to food pictures following a 45-minute exercise bout. Exercise did not alter energy intake. However, the exercise condition resulted in significantly more total physical activity, moderate intensity, vigorous intensity, moderate-to-vigorous (MVPA) intensity activity, and less sedentary time than the non-exercise condition. There was a significant group*condition interaction for MVPA (P=0.043) with obese women showing less MVPA than the normal-weight group. The sample of women studied did not show neurological differences in response to pictures of food based upon BMI. However, exercise decreased neurological responses to food, which may indicate lower food motivation. A supervised and planned exercise bout dramatically increased total physical activity in normal-weight and obese women compared to a day without planned exercise. There may be some negative compensation for MVPA in obese women following a 45-minute exercise bout compared to normal-weight women.

Schizophrenia (SZ) is a complex and chronic psychotic disorder that affects approximately 1% of the world's population and is associated with positive, negative, and cognitive symptoms. Auditory verbal hallucinations (AVHs) are a key symptom of SZ that cause functional impairments and distress. Despite antipsychotic medication treatments, 25% of patients experience medication resistant AVHs. Additional research into the underlying neuronal mechanisms of AVHs is needed to develop alternative treatments. The mismatch negativity (MMN) is an auditory event-related potential that represents pre-attentive detection of stimulus deviance. MMN deficits are prominent in SZ and are associated with greater AVH frequency. MMN deficits may also be related to qualitative features of AVHs, which have yet to be extensively assessed. The primary aim of this work was to assess differences in MMN features (amplitude and latency) between SZ patients and healthy controls (HCs) using two different versions of the MMN five deviant multi-feature task (pure tone and speech-based sounds). The second aim was to examine relationships between MMN features, clinical ratings of AVH severity (The Psychotic Symptom Rating Scale [PSYRATS] total score, Positive and Negative Syndrome Scale [PANSS] item 3 ["hallucinatory behaviour"]) and self-report measures of AVH features in SZ patients (i.e., the Beliefs About Voices Questionnaire-Revised [BAVQ-R], Voice Acceptance and Action Scale [VAAS] and the Voice Power Differential Scale [VPDS]), the latter has yet to be assessed. The secondary aim was to directly compare differences in the MMN responses between SZ and HC groups across the two tasks. Finally, exploratory aims included examining differences in MMN responses to low and high frequency and intensity deviants in the tone task and assessing differences in the MMN response between groups at the mastoid sites (TP9/TP10), where the polarity reversal of the MMN occurs. These more methodological aims have not been previously assessed, to our knowledge. The SZ group (n = 16) had significantly smaller MMN amplitudes to the frequency, gap and intensity deviants compared to the HC group (n = 17) in the MMN tone task. In the MMN speech task, the SZ group had significantly smaller MMN amplitudes to the frequency, intensity, vowel duration and consonant deviants compared to the HC group. The correlation analysis revealed that the most pronounced relation was a positive association between MMN amplitudes to the intensity deviant (tone task) and total scores on the VPDS (i.e., smaller/less negative MMN amplitudes were associated with higher VPDS scores). For the secondary analyses, the SZ group had smaller MMN amplitudes to the frequency deviant in both the tone and speech MMN tasks. Finally, the exploratory mastoid analysis in the tone task revealed that the SZ group had smaller MMN amplitudes to the frequency deviant at both mastoid sites. In the speech task, MMN amplitudes were larger at the left mastoid site (TP9) compared to the right mastoid site (TP10) across all deviant types. The HC group also had larger MMN amplitudes at the left mastoid site (TP9) compared to the SZ group. This study revealed MMN deficits in SZ patients across a variety of deviant types, including both pure tone deviants and speech-based deviants. MMN deficits were most pronounced for the frequency and intensity deviants across both tasks, suggesting that SZ patients with persistent AVHs may have more generalized deficits in the automatic processing of basic units of speech and pure tones, rather than impaired processing of specific acoustic features. Associations between MMN features and subjective measures of AVHs revealed that impaired processing of pure tone intensity deviants is related with a greater perceived "power" of the voice, impaired processing of speech-based frequency deviants is related to greater clinical AVH severity, and that impaired and less efficient processing of both vowel and pure tone deviants are related to a higher perceived hostility of the voice. This study adds valuable information to the literature regarding relationships between MMN features and subjective aspects of the AVH experience in SZ patients. Importantly, this work is novel as it is the first to directly compare MMN responses across two tasks (speech and sound) in SZ patients with persistent AVHs. This thesis emphasizes the importance of examining subjective aspects of the AVH experience in the context of the MMN to gather a more complete understanding of how AVHs are impacting brain responses.

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