Active Research Projects
We conduct experiments examining the neural underpinnings of aspects of language and cognitive processing, in typically developing children and adults as well as those exhibiting atypical or pathological development utilizing combinations of behavioral and electrophysiological techniques. This page provides short summaries of our current and recent research projects.
If you would like to participate in any of these studies, please visit the volunteer page.
This study uses EEG to investigate lexical and syntactic processing in codeswitching between two language varieties which exist in a diglossic situation (Modern Standard Arabic (MSA) and Colloquial Palestinian Arabic (PCA)). Study participants are presented with sentences in PCA and MSA: grammatical sentences in the targeted variety, sentences with semantically anomalous final words, sentences with codeswitched final words, and sentences where the final word was both semantically anomalous and code-switched. Participants are asked to judge whether the final word is in the same language as the rest of each sentence. Brain responses to the four conditions in each language variety, and between the two language varieties, showed that differences in N400 amplitude correlated with semantic anomaly in both languages, whereas the codeswitching manipulation resulted in a variety of changes both earlier (ELAN: 100-300 milliseconds post-onset) and later (P600: 500-700 milliseconds post-onset) in the processing stream. These results for the first time provide insight into the organization of diglossic languages in the brain; even though the speakers of such languages experience them as being closely related, this evidence suggests that diglossic languages are separate from one another but might differ in the strength of their connections at different levels of representation (phonological, lexical, semantic and syntactic).
Effects of Mindfulness Practices on Attention and Stress in School Children (5-7 year olds)
Research has supported the effectiveness of mindfulness training among adults on anxiety, attention, working memory, and executive function, a suite of skills used in the service of goal-directed behavior, which includes selective attention and inhibition. However there have been few investigations of the effects of mindfulness in young children. In the light of recent findings demonstrating the deleterious effects of poverty on educational attainment, cognitive development, attention and executive function, this study undertakes to evaluate the effects of mindfulness in kindergarten children. Using a Go/No-Go task designed to detect the ability to attend only to specified stimuli, we will record and analyze the brain responses of kindergarten children who have undertaken mindfulness training and compare them with their age-matched peers who have not had such experience. In keeping with our overall commitment to multi-modal investigations of cognitive processes, we will correlate the ERP findings related to executive function and attention with measures of stress hormones in saliva (cortisol and alpha amylase). It is hoped that these preliminary studies will provide a foundation for a larger-scale investigation that will focus on the effects of meditation on stress and language development in children of varying socioeconomic status. Principal Investigator: Trey Avery, PhD Candidate
Evaluation of MMN as biomarker for language impairment in autism spectrum disorders.
Current recommendations for diagnosis of Autism Spectrum Disorders (ASD) rely on determining whether a concomitant language impairment is present. It is very difficult to identify specific ASD type before an age when language delays are apparent; as a result, children with ASD go without intervention until, on average, 3 years of age or older. The ability to identify language impairment earlier in development is essential for achieving more timely and specific diagnoses and interventions for at-risk children. However, in order to achieve this, methods for examining language processing in young children must go beyond the behavioral observations used by most language assessments. Passive brain-imaging paradigms (for example electroencephalography or EEG) minimize receptive and expressive language demands, thus making them valuable measurement tools for determining language abilities in infants and children with ASD. This study targets the possibility of using EEG to examine aspects of language processing in the brains of children with ASD. Specifically, this study will evaluate the effectiveness and discriminatory value of this approach, and lay the foundations for a biomarker that could direct early speech and language intervention for children at risk for language impairment associated with ASD. Principal Investigator: Heather Green, PhD Candidate
Exploring Early Visual Sensory Differences in Dyslexia
Once referred to as "word blindness," dyslexia is now understood to involve more than visual perception and for decades has been viewed as a linguistic problem relating to a phonological deficit. Described as an inability to achieve reading competency despite adequate motivation, cognition and sensory levels, and appropriate educational input, dyslexia affects 5-17% of the population. The characteristic deficits of the disorder are not clearly homogeneous and hence an underlying explanation continues to elude researchers, evaluators and remediation specialists, though various proposals are emerging.
One such proposal, the Magnocellular Theory of Developmental Dyslexia, posits deficits in magnocellular neurons in the brain as the underlying basis for developmental dyslexia. These "large cells" support the transmission of fast temporal, low-contrast sensory information. Although magnocellular neurons can be found in sensory and motor systems throughout the central nervous system, only the visual system has a distinct magnocellular pathway. Studies of the magnocellular pathway in the visual system suggest that this pathway follows a protracted course of development, raising the possibility that it is more vulnerable to pathological change during development as well as having greater potential for plasticity. These observations led to the suggestion that the magnocellular pathway might be implicated in developmental dyslexia.
In contrast to the magnocellular pathway, the visual system employs parvocellular systems (that have "small cells") to process high frequency stimuli, such as color. In this study, we aim to establish whether magnocellular brain responses are compromised in people with dyslexia, in contrast to stimuli that are typically processed by the parvocellular pathways. Because the stimuli are "basic" in the sense of being pure visual (not alphabetic) percepts, this line of research may lead to procedures that are useful for very early (in infancy) identification of magnocellular changes. Such early identification could lead to pre-linguistic intervention - and hence perhaps prevention - for those at risk of developmental dyslexia. Principal Investigator: Lisa Levinson, PhD Student
Audiovisual Integration in Acquired Apraxia of Speech
Apraxia of Speech (AOS) is caused by stroke and subsequent damage to Broca's area in the brain. Patients with AOS experience non-fluent and halting speech, which impedes verbal communication. Currently AOS is considered a disorder of pure motor planning despite our understanding of the reciprocal relationship between speech production and perception. Speech perception is a multisensory audiovisual experience. fMRI studies show that a speech-production motor network, including Broca's area, is critical to audiovisual speech perception. Not knowing if there is a deficit in audiovisual speech perception in AOS complicates diagnosis of this disorder. Furthermore, the use of patients with AOS to inform theories of motor planning is convoluted by a lack of understanding of the nature of the disorder.
Co-articulation of speech segments is a fundamental impediment for patients with AOS. The Motor Theory of Speech Perception posits that there is a reciprocal relationship between the acoustic speech signal and the articulatory gestures used in production. Speech perception is a unique audiovisual experience because the timing of the speech signal is influenced by multiple articulatory gestures simultaneously in co-articulation. Therefore, individuals with AOS who have difficulty co-articulating speech could also have a disruption to the perceptual system for the rapid timing of overlapping articulatory gestures. This knowledge would validate the evidence of Broca's area involvement in speech perception and demarcate use of AOS patients in models of motor planning. Moreover, this knowledge would inform current treatments for individuals struggling with AOS.
EEG Studies of Audiovisual Integration in Apraxia of Speech
Evidence for the audiovisual nature of speech perception comes from the McGurk Effect, which shows that incongruent (non-matching) auditory and visual information alters speech perception. To investigate whether there is a breakdown in audiovisual integration in AOS, we will exploit the McGurk effect using EEG. Previous EEG studies of the McGurk effect have shown a mismatch negativity (MMN) to incongruent audiovisual speech stimuli. The MMN is an automatic and pre-attentive response to change in stimulus, which is an ideal method for investigating perceptual processing in individuals whose behavioral responses are limited by linguistic and motoric impairments. The MMN identifies an automatic response to the presentation of a novel stimulus among recurring standard stimuli. In the McGurk paradigm participants view a standard presentation of congruent (matching) auditory and visual information (e.g. articulation of /ba/) interspersed with a presentation of incongruent visual information (e.g. articulation of /ga/) dubbed over the original auditory stimulus. We hypothesize that in line with the body of previous research, healthy control subjects will experience the McGurk effect, hearing /da/, a fusion of /ba/ and /ga/, thus producing an MMN response. In contrast, we hypothesize that patients with AOS will not be sensitive to the change in visual information and will continue to perceive the auditory /ba/ stimulus, with no MMN response, indicating a deficit in audiovisual integration for speech. Principal Investigator: Melissa Randazzo-Wagner, PhD Student
Language and Music in Second Language Acquisition
In light of recent cuts to public school programming, questions are being raised about the necessity of programs in the arts and how the arts do or do not contribute to cognitive development. Neuroscientific research is beginning to explore how music is represented in the brain and has demonstrated that many brain regions engaged during language activities, are also engaged by musicians during musical activities. Psychological research suggests that when language sounds are presented along with musical tones, second-language learning time is reduced. This is intriguing because for many years music has been considered a “language.” A further focus on how music and language relate and/or can influence a reciprocal learning relationship is essential to understanding how musical training might enhance language learning.
This research study aims to investigate the question of whether adding musical tones has an effect on word boundary detection, by making statistical probabilities more salient, helping reduce the learning time of the new language. One theory of early-stage language acquisition suggests that we innately calculate the probability of one speech sound co-occurring with another (Transitional Probability). While the literature that addresses the use of musical tone and language learning is very limited, one psycholinguistic study used an artificial language to investigate this question, reporting significant results. It is now important, building on the behavioral research, to use a more detailed level, like EEG, to look at the neurological response that has the potential to shed light on the interaction between musical training and second-language learning at the level of the brain. This additional insight could help inform instructional practices aimed at second-language learners
Moving toward a neurophysiological understanding of dialectal variation: African American English and Standard American English syntax
Speakers of non-standard American English comprise a large majority of the speech therapy caseloads in public schools, and this study seeks to shed some light on our neurophysiological understanding of dialectal language differences - often misjudged as indicators of a language disorder. This experiment seeks to compare ERP responses to sentences in African American English (AAE) and Standard American English (SAE) between monolingual and bidialectal speakers. Adult participants in both groups will listen to sentences with the inclusion or omission of 3rd person present tense -'-s' marker, the absence of which is a syntactic violation to only SAE monolingual speakers (e.g., The black cat lap/s the milk). Preliminary findings from pilot research (Garcia, Froud & Khamis-Dakwar, 2013) indicate SAE speakers' brains respond to the syntactic violation, while AAE/SAE speakers demonstrate no statistically significant difference between conditions. This suggests that AAE is represented in the brain as a linguistic system distinct from AAE - not simply as a different or less formal "register". This perspective could help us to a better understanding of the difficulties encountered by children who are exposed to an English language variety at home that is syntactically and semantically different from the Standard American English used in school curriculums. Principal Investigator: Felicidad Garcia, PhD Student