Browsing by Subject "Event-related potentials"

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    Control and disposal of demonstratives, with electrophysiological evidence from English and Japanese
    (2014-06) Stevens, James Michael
    Demonstratives are lexical forms that pick out an object by making use of constraints in a discourse context to establish some form of contrast. They represent among the most basic uses of language, yet escape simple definition. The two forms gthish and gthath in English, the three forms ,± gko,h ,» gso,h , gah in Japanese, etc. have traditionally been interpreted in terms of relative distance from the speaker or hearer to the object. An alternative framework presents demonstratives as a device to refocus attention (e.g., Strauss, 2002), where gthish requires more of the hearerfs attention, to represent new information, or to refer to objects relatively important in the discourse, versus objects called gthath or gith. However, distance or attention alone is an insufficient parameter to predict form selection. This dissertation builds upon Brovold and Grushfs (2012) analysis of demonstratives in terms of control over an object. I propose that demonstrative forms, at least in English and Japanese, can be predicted from an array of control spaces that allow for varying levels of potential action toward an object. The proposed framework of control spaces implies an embodied view of language, such that language and physical behavior work toward shared goals and link mature human language use to other forms of animal communication, to child language acquisition, and with adult humansf response to a changing environment (De Ruiter, 2006; Melinger & Levelt, 2005).The control space framework incorporates previous models and makes three specific predictions. First, relative distance serves as one determinant for demonstrative form selection. Second, the weight of relative distance in demonstrative form selection will decrease without shared eye gaze between the speaker and hearer. 3. Demonstrative use would show as a tendency greater dependency on the co-speech pointing gesture for speakers of a language (e.g., English) that has fewer demonstrative terms than another (e.g., Japanese). To evaluate the three predictions, two perceptual studies that employed behavioral and event-related potential (ERP) measures were conducted to assess language usersf intuitions and cortical-level neural responses to the presentation of demonstrative expressions in differing visual contexts. When the simultaneous visual context with demonstrative expressions did not correspond with expected relative distances among speaker, hearer, and object, participants responded with significantly longer reaction times accompanied by a brain response called the N400, which is associated with semantic/contextual incongruities (Kutas & Hillyard, 1980, 1984). The elicitation of the N400 response for the incongruent audiovisual matchup in demonstrative use depended on shared gaze between the speaker and hearer, and the N400 responses were found in both English and Japanese subjects. English and Japanese subjects, however, differed in their responses to trials that did not include a pointing gesture in the visual scenes. In the absence of co-speech pointing gesture, English speakers expressed a P600 response, an index of pattern violations, but Japanese speakers did not. These findings indicate that in addition to spatial distance, language users rely on shared gaze in determining the proper use of demonstrative forms and show language-specific sensitivity to the presence or absence of gesture when analyzing demonstratives.The results of this dissertation project highlight the contingent, contrastive, and attention-orienting nature of demonstratives and further illustrate the necessity to study speech communication as a multimodal social event, which is subject to a number of factors, including perspectives of the speaker and listener, physical context, gesture, and language per se. Demonstratives function as basic lexical means to make meaning out of the world. They represent a special case of names, which are interpreted here as deictic means to form an object out of a nameless ground. Demonstratives, more specifically, serve as names that are used once and then no longer refer to the same object, resuming the naming practice with every use. The ERP results reported in this dissertation show promising brain signature markers for understanding the multimodal processing nature of spatial demonstratives. Further directions for research are suggested, including measuring the relationship between autistic individualsf competence with demonstratives alongside their imitative physical skills.
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    Event-related Potential Measurements of Long-term Orientation-specific Contrast Adaptation
    (2019-10) Baek, Yihwa
    The visual system continuously adjusts how it responds to current stimulus based on the history of the incoming stimuli, a process referred to as visual adaptation. Most of the previous studies focused on short-term adaptation effects ranging from milliseconds to minutes. Recent work has showed behavioral effects of long-term adaptation (hours and days), but their neural mechanisms remain unexplored. We aimed to uncover the neural bases of long-term orientation-specific contrast adaptation in an electroencephalography (EEG) experiment. Subjects were deprived of vertical contrast for 4 hours using altered reality goggles, which filtered out vertical energy from the scene in real-time. Event-related potentials (ERPs) in response to vertical and horizontal gratings were recorded before and after the long-term deprivation. We hypothesized that ERP response to vertical stimulation would increase in strength, and might decrease in latency, after the long-term deprivation. Results were analyzed by computing simple amplitudes of response, by comparing model fits to the ERP time courses, and by using the spatial pattern of ERP responses to classify trials by stimulation type. Early ERP components in response to vertical increased in amplitude and decreased in latency following adaptation, relative to responses to horizontal, but these differences were not significant. However, model fitting and classification results both revealed significantly greater differences in ERP responses between vertical and horizontal stimulation following adaptation. Collectively, these results suggest that long-term adaptation changes the amplitude of response in early visual cortex.
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    Is deprivation-related ADHD different from ADHD among children without histories of deprivation?
    (2012-07) Loman, Michelle M.
    Children reared in the deprived environments of institutions (e.g., orphanages) are at increased risk for problems with inattention and hyperactivity. Although these children have been reported to have higher rates of Attention Deficit/Hyperactivity Disorder (ADHD) diagnoses than would be expected in the general population, it is unclear if ADHD among post-institutionalized (PI) children is different from that among never institutionalized children. This study directly compared the clinical and symptom profile, executive function task and delay aversion task performances, and event-related potentials of 11- to 15-year-old internationally adopted PI children with ADHD (PI-A) to PI children without ADHD (PI-N) and non-adopted children with ADHD (NA-A). PI-As were found to be adopted primarily from Eastern European countries following longer periods of institutionalization than PI-Ns. They performed more poorly on most of the behavioral measures of executive function than PI-Ns; although the performance generally did not differ from NA-As. Relative to NA-As specifically, PI-As reported elevated disinhibited social behavior and, among males, demonstrated more aversion to delay, and had smaller overall N2 amplitude associated with a Go/No-go task. The results indicate that deprivation-related ADHD has an overlapping clinical profile with standard ADHD in addition to a few unique features. This profile associated with early deprived care could be considered a phenocopy of standard ADHD. A description of the deprivation-related ADHD profile has potential implications for identification and treatment of ADHD behaviors among PI youth.