Specific ERPs such as error- related negativity (ERN) and feedback- related negativity (FRN) reflect error processing/performance monitoring. The reinforcement learning theory of error processing suggests that ERN reflects the first detection of error commission. In order to elicit ERN, participants must perceive a response as erroneous. This implies that as learning occurs, ERN amplitude increases. A previous study (Horst, Johnson, & Donchin, 1980) examining the P300 component on a learning task demonstrated increased amplitude in response to violations of participants’ expectations about task events. The current study sought to replicate this finding while extending the analysis to include ERN and FRN amplitudes on incorrect trials. Participants completed a complex learning task in which they were required to learn 3 lists of paired nonsense syllables. Participants viewed a stimulus syllable, typed what they believed to be the correct response, then indicated their confidence level on a scale from 0- 100. Feedback was then presented regarding response accuracy. Each list was considered learned after 10 consecutively correct trials. Data from electrodes Fz, Cz, Pz, and Oz showed an increased ERN amplitude 50ms after error commission on incorrect trials. The ERN and FRN amplitudes were greater for incorrect trials than for correct trials. Larger P300 amplitudes were observed for trials in which participants’ outcome expectation was violated. This extension of previous findings provides further insight into the role of error processing in the context of reinforcement learning.

Error- related Negativity (ERN) is an event- related potential elicited by the commission of errors. It appears as a negative deflection peaking between 50ms and 100ms after an erroneous response. Previous literature demonstrated that individuals who suffer from either anxiety or depression display a higher ERN amplitude compared to a control group. It has also been shown that people with ADHD display a lower ERN amplitude. Based on these findings, we investigated the relationships between these three disorders and their effects on the amplitude of the ERN. We recruited thirty- one students at East Tennessee State University and gathered data on their level of anxiety, depression, and ADHD through completion of three surveys: the Beck Anxiety Inventory, Beck Depression Inventory, and the ADHD self- report scale. Subsequently, participants were asked to perform a modified Flanker task while their EEG was collected using a 32- channel EEG cap. ERN amplitude for error responses was significantly higher than ERN amplitude for correct responses. In contrast with previous literature, no significant influence on the ERN due to anxiety, depression, and ADHD was found. Additional research on the topic with larger sample size and different diagnostic procedures may be necessary to further investigate the phenomenon.

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Dictyostelium discoideum (Dd) is a model organism, studied for reasons from cell movement to chemotaxis to human disease control. Creating a computer model of the life cycle of Dd has garnered great interest, one part of which is the Aggregation Stage, where thousands of amoeba gather together to form a slug. Chemotaxis is the mechanism through which this is accomplished. This thesis develops two- and three-dimensional alternating direction implicit code which solves the diffusion equation on an adaptive grid. The calculated values for both two and three dimensions are checked against the actual solution and error results are provided. Comparisons are made between the coarse grid with refinement case and a fine grid without refinement case. Also, a non-negativity condition for two dimensions is derived to give a bound on the three major parameters: the diffusion coefficient and the spatial and time discretizations.

Phonemic categorization is the ability to discriminate and organize speech sounds into categories. This ability begins soon after birth and continues to refine as an individual matures. An association between categorical labeling and phonological awareness has been reported. A strong link between perception and production has been established. The present study examined phonemic categorization of two groups of four listeners. Eight-to ten-year-old children with an articulation disorder were compared with typically speaking peers to determine if the two groups differed in their ability to categorize speech sounds. Behavioral and electrophysiological measures were used to ascertain if any differences existed. These measures were obtained in response to four stimulus pairs (/pɑ/-/tɑ/, /tɑ/-/kɑ/, /pɑ/-/kɑ/, /sɑ/-/ʃɑ/). Three of the pairs (/pɑ/-/tɑ/, /tɑ/-/kɑ/, /pɑ/-/kɑ/) differed by place of articulation only and the fourth pair (/sɑ/-/ʃɑ/) consisted of sounds that are more commonly found in error for the age group of the participants. Behavioral data showed differences in reaction time between the two groups as well as between correct and incorrect responses. Electrophysiological data including the mismatch negativity showed that both groups perceived a distinction between the stimuli presented, but the normal control group generally displayed a higher SD for peak latency and amplitude. The normal control group also generally displayed a higher mean amplitude. These results suggest a difference between the two groups in the underlying processes of phonemic categorization. Specifically, these results support that the normal control group's ability to distinguish and categorize speech sounds is better established than that of their peers with an articulation disorder.

Many real world problems require multi-label classification, in which each training instance is associated with a set of labels. There are many existing learning algorithms for multi-label classification; however, these algorithms assume implicit negativity, where missing labels in the training data are automatically assumed to be negative. Additionally, many of the existing algorithms do not handle incremental learning in which new labels could be encountered later in the learning process. A novel multi-label adaptation of the backpropagation algorithm is proposed that does not assume implicit negativity. In addition, this algorithm can, using a naive Bayesian approach, infer missing labels in the training data. This algorithm can also be trained incrementally as it dynamically considers new labels. This solution is compared with existing multi-label algorithms using data sets from multiple domains and the performance is measured with standard multi-label evaluation metrics. It is shown that our algorithm improves classification performance for all metrics by an overall average of 7.4% when at least 40% of the labels are missing from the training data, and improves by 18.4% when at least 90% of the labels are missing.

Metacognition, which involves monitoring and controlling of one’s thoughts and actions, is essential for guiding behavior and organization of information. Deficits in self-monitoring have been suggested to lead to psychosis and poor functional outcome. Abnormalities in eventrelated potentials originating from the anterior cingulate cortex (ACC), a brain region associated with error detection, have been consistently reported in individuals with schizophrenia during error monitoring tasks. This study sought to examine whether these abnormalities are present in individuals with a history of psychosis across diagnostic categories and whether they are associated with subjective appraisal of self-performance and personality traits related to psychosis. The error-related negativity (ERN), the correct response negativity (CRN), and the error positivity (Pe) were recorded in 15 individuals with a history of psychosis (PSY) and 12 individuals without a history of psychosis (CTR) during performance on a flanker task. Participants also continuously rated their performance on the task and completed the Schizotypal Personality Questionnaire – Brief Revised (SPQ-BR). Compared with the CTR group, the PSY group exhibited reduced ERN and Pe amplitudes during error trials, but normal CRN and Pe amplitudes during correct trials. The PSY group also was less accurate at identifying their errors than the CTR group but just as accurate at identifying correct responses. Across all participants, smaller ERN amplitudes were associated with greater scores on the Disorganized factor of the SPQ-BR and smaller Pe amplitudes were associated with greater scores on the Cognitive Perceptual factor of the SPQ-BR. Individuals with a history of psychosis regardless of diagnosis demonstrated abnormal neural activity during error monitoring. Error monitoring deficits may be associated with vulnerability for psychosis across disorders.

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.

In this systematic review and meta-analysis, the relationship between error awareness and the amplitude of Error-Related Negativity (ERN), a neural response to errors associated with cognitive control and error monitoring processes, was examined. Five studies published between 2010 and 2020, involving a total of 302 participants, were analyzed. Findings revealed a more pronounced negative amplitude of the ERN for aware errors compared to unaware errors, supporting the Error Detection Theory and Reinforcement Learning Theory. The results did not directly support or contradict the Conflict-Monitoring Theory. These findings underscore the critical role of conscious error detection in modulating ERN responses and adaptive behavioral modifications. However, due to the limited number of included studies and variability in their methodologies, caution is needed in interpreting the results. Future research should aim to validate these findings with larger samples and standardized study designs, while also exploring a more nuanced understanding of error awareness.

Timing, and ergo rhythm, are intrinsic features of language that help facilitate real-time speech comprehension. However, work exploring how variable timing is processed in speech is limited. This dissertation addresses this gap in literature by exploring the tenets of how temporal variability is cognitively processed, particularly in the context of real-time stimulus processing. This research is one of the first works to examine temporal variations in linguistic and other acoustically complex contexts. Using electroencephalography (EEG) and behavioural methods, participants were tested on their perception of temporal variations within a continuous stream of either simple tones, complex waves, or syllables. Two timing deviants were presented that occurred early or late compared to other stimuli in the sequence. Event-related potentials (ERPs) were recorded for each stimulus type across three experiments. A fourth experiment tested participant recognition memory for syllable order. Results showed differential processing between the two timing deviants. Unexpectedly earlier tokens elicited larger pre-attentive responses compared to late, suggesting a saliency for the earlier tokens that was not present for the delayed ones. This pattern was observed across all three levels of acoustic and linguistic complexity. Compared to sequences with no timing deviants or an early timing deviant, unexpectedly late tokens were more detrimental to memory, suggesting a negative impact of delays on verbal recognition. Thus, not only were early and late timing variations processed differently, but delays in continuous sequences were also more cognitively taxing for working memory. The results reported in this dissertation contribute to existing knowledge by enriching our understanding of the fundamentals of how aspects of prosodic timing may affect attention and memory. Additionally, it provides new insights into how speech synthesis can be used in neurolinguistic research by tracking how neurophysiological responses change with increasing acoustic complexity and linguistic familiarity. / Dissertation / Doctor of Philosophy (PhD) / This thesis examines how unexpectedly shorter or longer pauses in speech may affect speech comprehension. Specifically, the research reported here examined how stimuli that are presented unexpectedly early or unexpectedly late in a steady-rate sequence impact a listener’s attention and memory. Although the speed at which we speak has been studied previously, work on unexpected changes in its timing has been limited. This research begins to explore this aspect of speech processing. It contributes to our understanding of how speech timing is processed in two important ways. First, we found that unexpected delays in both non-linguistic sounds and syllables were less noticeable than unexpectedly early presentations, when participants were not required to pay attention to them. Second, we found that unexpected delays made recognition memory for stimulus order worse. Overall, the results of these studies indicate that unexpected delays in the rhythm of speech make it more difficult to understand.