This study investigated the neurophysiology of semantic language processing in children, ages 5 to 12 years. A well-established marker of semantic processing, the N400 event related potential (ERP), was analyzed within and across child age groups. Child N400s were recorded in response to correct sentences, semantically incorrect sentences, and syntactically incorrect sentences. N400s were also recorded across ear condition to examine potential processing differences. Children across all age groups consistently demonstrated N400s in the semantic error condition. N400s were also regularly observed in the syntactic error condition; especially, for younger children. Younger children also demonstrated N400s even in response to correct sentence types. Interestingly, clear N400 effects (i.e. N400 amplitude differences between correct and semantically incorrect sentences) were only observed for one age group. While these findings indicate that children across all age groups detect semantic errors, the ability to consistently parse error types develops later.

The examination of Event Related Potentials during language processing tasks provides valuable information of how the brain processes language over time. In the current study, the development of the early left anterior negativity (ELAN) was analyzed in young children. Previous research has described the ELAN as a negative waveform elicited during syntactic processing between 200 and 500 ms post linguistic stimuli. Thirty children from 5 to 12 years of age listened to sentences that were linguistically correct, syntactically incorrect, or semantically incorrect. Sentences were presented for right monaural, left monaural, and binaural ear conditions to determine possible differences related to right ear advantage (REA). An ELAN-like component in regards to latency and amplitude was observed in children 8 years of age and older; however, comparison between linguistic conditions suggest that the ability to differentiate between linguistically correct, syntactically incorrect, and semantically incorrect stimuli is not established until 12 years of age. Results suggest that adult-like syntactic processing of morphosyntactic errors is not established until after 12 years of age. Comparison between ear conditions suggests that the REA effect may exist in older children, a finding that has not been reflected in previous behavioral research.

Event related potentials (ERPs) may provide specific information about how particular aspects of language are processed by the brain over time. This study investigated the electrophysiology of language processing in two children with language impairment (LI) when compared to five typically developing children. The N400, P600, and the early left anterior negativity (ELAN) were analyzed after participants listened to linguistically correct, syntactically incorrect, and semantically incorrect sentences. Participants were instructed to indicate whether the sentences were correct or incorrect. Latency and amplitude of the ERP components were compared between the two groups of participants and sentence types. Results from the current study concerning the typically developing children suggest that, at least by eight years of age, typically developing children may process linguistic information similarly to adults with regard to the areas of the brain that are activated during the processing of linguistic stimuli. When comparing results from participants with LI and their typically developing counterparts, results indicate that children with LI exhibit slower real-time language processing than typically developing children. Results also indicate that children with LI require more effort than typically developing children in processing linguistic information as indicated by the amplitude of the N400 and the ELAN. In analyzing the P600 in both groups of participants, results indicate that syntactic processing may be intact in children with LI as well as typical children. Results concerning the N400 and the ELAN were variable between the two participants with LI indicating that children with LI may be heterogeneous even in the presence of similar tasks. Results obtained from the ELAN may also indicate that the ELAN is not fully mature at eight years of age.

Objective: An electroencephalographic brain-computer interface (BCI) can provide a non-muscular means of communication for people with amyotrophic lateral sclerosis (ALS) or other neuromuscular disorders. We present a novel P300-based BCI stimulus presentation - the checkerboard paradigm (CBP). CBP performance is compared to that of the standard row/column paradigm (RCP) introduced by Farwell and Donchin (1988). Methods: Using an 8 × 9 matrix of alphanumeric characters and keyboard commands, 18 participants used the CBP and RCP in counter-balanced fashion. With approximately 9-12 min of calibration data, we used a stepwise linear discriminant analysis for online classification of subsequent data. Results: Mean online accuracy was significantly higher for the CBP, 92%, than for the RCP, 77%. Correcting for extra selections due to errors, mean bit rate was also significantly higher for the CBP, 23 bits/min, than for the RCP, 17 bits/min. Moreover, the two paradigms produced significantly different waveforms. Initial tests with three advanced ALS participants produced similar results. Furthermore, these individuals preferred the CBP to the RCP. Conclusions: These results suggest that the CBP is markedly superior to the RCP in performance and user acceptability. Significance: The CBP has the potential to provide a substantially more effective BCI than the RCP. This is especially important for people with severe neuromuscular disabilities.

Objective: Brain-computer interface (BCI) technology can provide severely disabled people with non-muscular communication. For those most severely disabled, limitations in eye mobility or visual acuity may necessitate auditory BCI systems. The present study investigates the efficacy of the use of six environmental sounds to operate a 6 × 6 P300 Speller. Methods: A two-group design was used to ascertain whether participants benefited from visual cues early in training. Group A (N = 5) received only auditory stimuli during all 11 sessions, whereas Group AV (N = 5) received simultaneous auditory and visual stimuli in initial sessions after which the visual stimuli were systematically removed. Stepwise linear discriminant analysis determined the matrix item that elicited the largest P300 response and thereby identified the desired choice. Results: Online results and offline analyses showed that the two groups achieved equivalent accuracy. In the last session, eight of 10 participants achieved 50% or more, and four of these achieved 75% or more, online accuracy (2.8% accuracy expected by chance). Mean bit rates averaged about 2 bits/min, and maximum bit rates reached 5.6 bits/min. Conclusions: This study indicates that an auditory P300 BCI is feasible, that reasonable classification accuracy and rate of communication are achievable, and that the paradigm should be further evaluated with a group of severely disabled participants who have limited visual mobility. Significance: With further development, this auditory P300 BCI could be of substantial value to severely disabled people who cannot use a visual BCI.

Behavioral symptoms of autism spectrum disorder (ASD) begin to emerge around 12 months of age and are preceded by subtle differences in how infants process and interact with the world (Elsabbagh & Johnson, 2010). Similar atypical behavioral patterns and markers of brain organization (`endophenotypes') are present in infants at risk for ASD (HRA) due to their family history, regardless of whether they ultimately develop the disorder. Possible endophenotypes of ASD were investigated through four studies that examined event-related potentials (ERPs) to speech and language in HRA and low-risk control (LRC) infants as part of a larger, longitudinal project. Chapter 2 examined ERPs to language-specific phonemes at 6, 9, and 12 months (n=59 at 6mo, 77 at 9mo, and 70 at 12mo) and found that HRA infants were not delayed in phonemic perceptual narrowing yet exhibited atypical hemispheric lateralization of ERPs at 9 and 12 months. Chapter 3 explored these findings further in a sample with known developmental outcome (n=60 at 6mo, 75 at 9mo, and 72 at 12mo) in order to understand how these ERPs differ between infants who ultimately develop ASD and infants who do not. Chapter 4 examined responses to repeated speech stimuli at 9 months (n=95). HRA infants exhibited atypically large ERPs to repeated speech, and this pattern was associated with better later language ability. Finally, Chapter 5 examined ERPs to words at 18 and 24 months (n=41 at 18mo, 52 at 24mo) and found evidence for atypical topography of responses to known versus unknown words, particularly at 18 months. These findings provide evidence that in HRA infants, even those who do not develop ASD, neural processing of linguistic stimuli is altered during infancy and toddlerhood. The results from Chapter 4 suggest that at least some of the differences seen in HRA infants who do not develop ASD may reflect beneficial, rather than disordered, processing. Overall, these results contribute to growing evidence that familial risk for ASD is associated with atypical processing of speech and language during infancy. Future work should continue to investigate more closely the implications of atypical neural processing for infants' later development.

Temporally selective attention allows for the preferential processing of stimuli presented at particular times, and is reasoned to be important for processing rapidly presented information such as speech. Recent event-related potential (ERP) evidence demonstrates that listeners direct temporally selective attention to times that contain word onsets in speech. This may be an effective listening strategy since these moments provide critical information to the listener, but the mechanism that underlies this process remains unexplored. In three experiments, putative attention cues including word recognition and predictability were manipulated in both artificial and natural speech and ERP responses at various times were compared to determine how listeners selectively process word onsets in speech. The results demonstrate that listeners allocate attention to word-initial segments because they are less predictable than other times in the speech stream. Attending to unpredictable moments may improve spoken language comprehension by allowing listeners to glean the most relevant information from an otherwise overwhelming speech signal.

Hearing loss, as a result of old age, has been linked to a decline in speech perception despite the use of additional listening devices. Even though the relationship between hearing loss and decreased speech perception has been well established, research in this area has often focused on the behavioral aspects of language and not on the functionality of the brain itself. In the present study, the mismatch negativity, an event related potential, was examined in order to determine the differences in speech perception between young adult participants, geriatric normal hearing participants, and geriatric hearing-impaired participants. It was hypothesized that a significantly weaker mismatch negativity would occur in the geriatric hearing-impaired participants when compared to the young adult participants and the geriatric normal hearing participants. A passive same/different discrimination task was administered to 10 young adult controls (5 male, 5 female) and eight older adult participants with and without hearing loss (4 male, 4 female). Data from behavioral responses and event related potentials were recorded from 64 electrodes placed across the scalp. Results demonstrated that the mismatch negativity occurred at various amplitudes across all participants tested; however, an increased latency in the presence of the mismatch negativity was noted for the geriatric normal hearing and the geriatric hearing-impaired participants. Dipoles reconstructed from temporal event related potential data were located in the cortical areas known to be instrumental in auditory and language processing for the young adult participants; however, within the geriatric normal hearing and the geriatric hearing-impaired participants, dipoles were seen in multiple locations not directly associated with language and auditory processing. Although not conclusive, it appears that within the geriatric normal hearing and the geriatric hearing-impaired participants there is slower processing of the speech information, as well as some cognitive confusion which leads to fewer available resources for interpretation.

In this thesis, I investigate idiom processing from two angles through three different studies. First, I approached idiom processing from a constraint-based perspective. According to this view, not all idioms are alike: they can differ regarding lexical, and linguistic characteristics, such as their level of familiarity. In this first study, I investigated the underlying processes during the comprehension of idioms with different characteristics. I used the Event Related Potential (ERP) technique, which has high temporal resolution, to investigate this issue. I provided evidence that idioms' characteristics impact their processing. More specifically, idioms which are more familiar to language users (i.e., the ones that are encountered more frequently) showed processing facilitation compared to less familiar idioms. Also, idioms with plausible literal interpretation showed processing advantages over idioms which are less likely to be interpreted literally. The second aim of the current thesis was to investigate idiom processing from an embodied account of language processing. According to this view, various sources of information (including linguistic, affective, and sensory-motor) are available and used during the comprehension of language. While, this view has become popular in many language processing studies, studies of idiom processing are still at the beginning of this journey. To be able to investigate idiom processing while considering the role of affective and sensory-motor factors, we require access to norming data. In the second (descriptive) study, I conducted a large-scale survey and collected measures of valence, arousal, concreteness, and imageability for a set of English idioms, by both native speakers of English and proficient second language speakers. In the last study, I explored how the emotional status of idioms and their concreteness contributes to their processing, and whether this contribution is modulated by idiom familiarity. We found that the impact of non-linguistic sources of information (affective and sensory-motor) is determined by idiom familiarity, such that low familiar and high familiar idioms show different behaviour where these factors are concerned. For highly familiar idioms, behaviour aligns with the findings on word processing: for example, idioms with more positive valence showed facilitative processing. Unlike highly familiar idioms, valence had an inhibitory impact on idioms with low familiarity level, such that greater valence increased the reading time.

Grammatical gender is a complex classification system and is often referred to as one of the most difficult grammatical categories for second language (L2) speakers to master. Previous research has focused on anticipatory processing of grammatical gender cues in first language (L1) speakers of various gendered languages (French, Spanish, Dutch, etc.) and has found that speakers use gender information from a preceding determiner to facilitate access to a gender-congruent noun (e.g., Dussias et al., 2013; Lew-Williams & Fernald, 2010). These findings have been consistently found among speakers of various languages when they were presented with congruent vs. incongruent determiner phrases (DPs), subsequently collapsing across grammatical genders (e.g., congruent: la maison and le bateau vs. incongruent: *le maison vs. *la bateau). Responses to individual genders cues in Spanish has been teased apart (masculine vs. feminine) as well as the effect of inhibitory control on gender processing (Beatty-Martínez, et al., 2020). A correlation between grammatical gender error recovery and increased inhibitory control was found. The current dissertation aims to dissect the processing and underlying neural mechanisms associated with masculine and feminine grammatical gender in L1 French, simultaneous French-English, and L1 English-L2 French speakers. A series of three experiments were conducted. The first two experiments used a masked priming lexical decision task where participants were presented with congruent (e.g., la maison) and incongruent (*le maison) DPs. The first experiment employed a behavioural version of the task and the second experiment focused on event-related brain potentials (ERPs). At a behavioural level, there was no indication of grammatical gender cue use. However, ERP results show that L1 speakers employ distinct processing mechanisms for feminine (P200; *le maison) incongruencies compared to feminine congruencies (la maison). The final experiment consisted of a self-paced reading task, where participants read sentences with congruent and incongruent DPs and an AX-CPT task as a measure of inhibitory control. L1 French and simultaneous French-English speakers exhibit processing difficulties with the incongruent feminine condition (*le maison) compared to the congruent feminine condition (la maison), as well as with the incongruent masculine condition (*la bateau) compared to the congruent masculine condition (le bateau). On the other hand, L2 speakers only show difficulty with the incongruent feminine condition in relation to the congruent feminine condition. Further, there was no relationship between inhibitory control and grammatical gender processing across groups. Overall, the results reflect an intricate picture of grammatical gender processing in French speakers. At a lexical level, L1 French speakers likely process incongruent feminine DPs as a lexical clash, potentially implementing further cognitive resources during processing. At a syntactic level, L1 French and simultaneous French-English speakers show processing difficulties behaviourally to gender incongruencies. L2 speakers seem to employ the use of masculine grammatical gender cues, implying that it is perhaps the presence of a feminine noun causing processing difficulty due to a feature mismatch. These results indicate that masculine and feminine genders employ distinct processing mechanisms and may be accessed in a contrasting manner.