Matching Items (5)
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- All Subjects: EEG
- Creators: Liss, Julie
- Creators: Wahnoun, Remy
- Status: Published
Description
When surgical resection becomes necessary to alleviate a patient's epileptiform activity, that patient is monitored by video synchronized with electrocorticography (ECoG) to determine the type and location of seizure focus. This provides a unique opportunity for researchers to gather neurophysiological data with high temporal and spatial resolution; these data are assessed prior to surgical resection to ensure the preservation of the patient's quality of life, e.g. avoid the removal of brain tissue required for speech processing. Currently considered the "gold standard" for the mapping of cortex, electrical cortical stimulation (ECS) involves the systematic activation of pairs of electrodes to localize functionally specific brain regions. This method has distinct limitations, which often includes pain experienced by the patient. Even in the best cases, the technique suffers from subjective assessments on the parts of both patients and physicians, and high inter- and intra-observer variability. Recent advances have been made as researchers have reported the localization of language areas through several signal processing methodologies, all necessitating patient participation in a controlled experiment. The development of a quantification tool to localize speech areas in which a patient is engaged in an unconstrained interpersonal conversation would eliminate the dependence of biased patient and reviewer input, as well as unnecessary discomfort to the patient. Post-hoc ECoG data were gathered from five patients with intractable epilepsy while each was engaged in a conversation with family members or clinicians. After the data were separated into different speech conditions, the power of each was compared to baseline to determine statistically significant activated electrodes. The results of several analytical methods are presented here. The algorithms did not yield language-specific areas exclusively, as broad activation of statistically significant electrodes was apparent across cortical areas. For one patient, 15 adjacent contacts along superior temporal gyrus (STG) and posterior part of the temporal lobe were determined language-significant through a controlled experiment. The task involved a patient lying in bed listening to repeated words, and yielded statistically significant activations that aligned with those of clinical evaluation. The results of this study do not support the hypothesis that unconstrained conversation may be used to localize areas required for receptive and productive speech, yet suggests a simple listening task may be an adequate alternative to direct cortical stimulation.
ContributorsLingo VanGilder, Jennapher (Author) / Helms Tillery, Stephen I (Thesis advisor) / Wahnoun, Remy (Thesis advisor) / Buneo, Christopher (Committee member) / Arizona State University (Publisher)
Created2013
Description
Brain-computer interface technology establishes communication between the brain and a computer, allowing users to control devices, machines, or virtual objects using their thoughts. This study investigates optimal conditions to facilitate learning to operate this interface. It compares two biofeedback methods, which dictate the relationship between brain activity and the movement of a virtual ball in a target-hitting task. Preliminary results indicate that a method in which the position of the virtual object directly relates to the amplitude of brain signals is most conducive to success. In addition, this research explores learning in the context of neural signals during training with a BCI task. Specifically, it investigates whether subjects can adapt to parameters of the interface without guidance. This experiment prompts subjects to modulate brain signals spectrally, spatially, and temporally, as well differentially to discriminate between two different targets. However, subjects are not given knowledge regarding these desired changes, nor are they given instruction on how to move the virtual ball. Preliminary analysis of signal trends suggests that some successful participants are able to adapt brain wave activity in certain pre-specified locations and frequency bands over time in order to achieve control. Future studies will further explore these phenomena, and future BCI projects will be advised by these methods, which will give insight into the creation of more intuitive and reliable BCI technology.
ContributorsLancaster, Jenessa Mae (Co-author) / Appavu, Brian (Co-author) / Wahnoun, Remy (Co-author, Committee member) / Helms Tillery, Stephen (Thesis director) / Barrett, The Honors College (Contributor) / Harrington Bioengineering Program (Contributor) / Department of Psychology (Contributor)
Created2014-05
Description
The research question this thesis aims to answer is whether depressive symptoms of adolescents involved in romantic relationships are related to their rejection sensitivity. It was hypothesized that adolescents who have more rejection sensitivity, indicated by a bigger P3b response, will have more depressive symptoms. This hypothesis was tested by having adolescent couples attend a lab session in which they played a Social Rejection Task while EEG data was being collected. Rejection sensitivity was measured using the activity of the P3b ERP at the Pz electrode. The P3b ERP was chosen to measure rejection sensitivity as it has been used before to measure rejection sensitivity in previous ostracism studies. Depressive symptoms were measured using the 20-item Center for Epidemiological Studies Depression Scale (CES-D, Radloff, 1977). After running a multiple regression analysis, the results did not support the hypothesis; instead, the results showed no relationship between rejection sensitivity and depressive symptoms. The results are also contrary to similar literature which typically shows that the higher the rejection sensitivity, the greater the depressive symptoms.
ContributorsBiera, Alex (Author) / Dishion, Tom (Thesis director) / Ha, Thao (Committee member) / Shore, Danielle (Committee member) / Barrett, The Honors College (Contributor)
Created2015-05
Description
Previous research has showed that auditory modulation may be affected by pure tone
stimuli played prior to the onset of speech production. In this experiment, we are examining the
specificity of the auditory stimulus by implementing congruent and incongruent speech sounds in
addition to non-speech sound. Electroencephalography (EEG) data was recorded for eleven adult
subjects in both speaking (speech planning) and silent reading (no speech planning) conditions.
Data analysis was accomplished manually as well as via generation of a MATLAB code to
combine data sets and calculate auditory modulation (suppression). Results of the P200
modulation showed that modulation was larger for incongruent stimuli than congruent stimuli.
However, this was not the case for the N100 modulation. The data for pure tone could not be
analyzed because the intensity of this stimulus was substantially lower than that of the speech
stimuli. Overall, the results indicated that the P200 component plays a significant role in
processing stimuli and determining the relevance of stimuli; this result is consistent with role of
P200 component in high-level analysis of speech and perceptual processing. This experiment is
ongoing, and we hope to obtain data from more subjects to support the current findings.
stimuli played prior to the onset of speech production. In this experiment, we are examining the
specificity of the auditory stimulus by implementing congruent and incongruent speech sounds in
addition to non-speech sound. Electroencephalography (EEG) data was recorded for eleven adult
subjects in both speaking (speech planning) and silent reading (no speech planning) conditions.
Data analysis was accomplished manually as well as via generation of a MATLAB code to
combine data sets and calculate auditory modulation (suppression). Results of the P200
modulation showed that modulation was larger for incongruent stimuli than congruent stimuli.
However, this was not the case for the N100 modulation. The data for pure tone could not be
analyzed because the intensity of this stimulus was substantially lower than that of the speech
stimuli. Overall, the results indicated that the P200 component plays a significant role in
processing stimuli and determining the relevance of stimuli; this result is consistent with role of
P200 component in high-level analysis of speech and perceptual processing. This experiment is
ongoing, and we hope to obtain data from more subjects to support the current findings.
ContributorsTaylor, Megan Kathleen (Author) / Daliri, Ayoub (Thesis director) / Liss, Julie (Committee member) / School of Life Sciences (Contributor) / School of International Letters and Cultures (Contributor) / Barrett, The Honors College (Contributor)
Created2020-05
Description
Transcranial Current Stimulation (TCS) is a long-established method of modulating neuronal activity in the brain. One type of this stimulation, transcranial alternating current stimulation (tACS), is able to entrain endogenous oscillations and result in behavioral change. In the present study, we used five stimulation conditions: tACS at three different frequencies (6Hz, 12Hz, and 22Hz), transcranial random noise stimulation (tRNS), and a no-stimulation sham condition. In all stimulation conditions, we recorded electroencephalographic data to investigate the link between different frequencies of tACS and their effects on brain oscillations. We recruited 12 healthy participants. Each participant completed 30 trials of the stimulation conditions. In a given trial, we recorded brain activity for 10 seconds, stimulated for 12 seconds, and recorded an additional 10 seconds of brain activity. The difference between the average oscillation power before and after a stimulation condition indicated change in oscillation amplitude due to the stimulation. Our results showed the stimulation conditions entrained brain activity of a sub-group of participants.
ContributorsChernicky, Jacob Garrett (Author) / Daliri, Ayoub (Thesis director) / Liss, Julie (Committee member) / School of Life Sciences (Contributor, Contributor) / Barrett, The Honors College (Contributor)
Created2020-05