Browsing by Author "Beauchamp, Michael S."
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Item An investigation of audiovisual speech perception using the McGurk effect(2014-04-14) Basu Mallick, Debshila; Beauchamp, Michael S.; Dannemiller, James L.; Beier, Margaret E.; Schnur, Tatiana T.Integrating information from the auditory and visual modalities is vital for speech perception. In this thesis, I describe two studies of audiovisual speech perception that make use of an audiovisual illusion known as the McGurk effect. In the McGurk effect, two different syllables presented simultaneously in auditory and visual modalities are fused and perceived as a novel syllable (McGurk & MacDonald, 1976). In the first study, we conducted a large-scale assessment of the McGurk effect across fourteen McGurk stimuli tested in up to 165 participants. This study revealed that McGurk perception is characterized by wide variability across stimuli. The second study investigated whether phonetic identification training could increase McGurk perception. This study showed that participants improved on the training task, but there was no increase in McGurk perception.Item Integration of sight, hearing and touch in human cerebral cortex(2009) Yasar, Nafi; Beauchamp, Michael S.While each individual sensory modality provides us with information about a specific aspect about our environment, our senses must be integrated for us to interact with the environment in a meaningful way. My thesis describes studies of the interactions between somatosensation, vision and audition using functional Magnetic Resonance Imaging (fMRI) of normal human subjects as the primary method. In order to study somatosensation with fMRI we first built an MRI-compatible tactile-stimulation apparatus. This apparatus was then used for four separate studies. In the first study, we investigated tactile responses in lateral occipital lobe, a brain region traditionally considered "visual" cortex. We found that visual area MST, but not visual area MT, responded to tactile stimulation. In the second study we investigated a possible homologue to a macaque multisensory area that integrates visual, auditory and tactile information, called the Superior Temporal Polysensory area (STP). We found responses to tactile stimuli co-localized with auditory and visual responses in posterior superior temporal sulcus. This is likely to be a human homologue to macaque STP. In the third study, we used Multi Voxel Pattern Analysis (MVPA) to demonstrate that this homologue of macaque STP (along with traditional "somatosensory" areas) can predict the location of tactile stimulation from fMRI data. In the fourth study we used psychophysical techniques to analyze the effects of auditory stimuli on tactile perception. We found that auditory stimuli can influence detection, frequency perception, and the perception of the spatial location of vibrotactile stimuli. Two additional projects are also briefly described. The results of an effort to develop an MRI compatible Transcranial Magnetic Stimulation (TMS) device are included. Also a project I worked on during my summer internship in which I debugged a system capable of both stimulating and recording from cortical tissue at the same time is also discussed.Item The Mechanisms of Proactive Interference and Their Relationship with Working Memory(2012-09-05) Glaser, Yi; Martin, Randi C.; Byrne, Michael D.; Wilson, Rick K.; Basak, Chandramallika; Beauchamp, Michael S.Working memory (WM) capacity – the capacity to maintain and manipulate information in mind – plays an essential role in high-level cognitive functions. An important determinant of WM capacity is the ability to resolve interference of previously encoded but no longer relevant information (proactive interference: PI). Four different mechanisms of PI resolution involving binding and inhibition have been proposed in the literature, although debate continues regarding their role. Braver et al. (2007) introduced an important distinction in the PI resolution literature, proposing two general types of PI control mechanisms that occur at different time points: proactive control (involves preparation in advance of the interference) and reactive control (occurs after interference occurs). This thesis proposed that among these four functions involving binding and inhibition, item inhibition and binding could be involved in proactive control, while familiarity inhibition and episodic inhibition could be involved in reactive control. The question is which mechanism in each pair is indeed involved in proactive control and reactive control respectively, and how these proactive control and reactive control mechanisms work together to resolve PI. In addition, do these mechanisms play a role in the relationship between PI resolution and WM? In an individual differences study, individuals’ ability to resolve PI was assessed in memory tasks, with two versions of each that encouraged the use of either proactive or reactive control. In addition, measures were obtained of individuals’ ability of binding and inhibition in tasks that had minimal memory demands. Regression analyses showed contributions of binding and inhibition to PI resolution and WM. Moreover, these functions are responsible for the correlation between PI resolution and WM. In a neuroimaging study, the neural basis of proactive control was examined by comparing two memory tasks that differed in their demand on binding and inhibition. In addition, the brain regions engaged in reactive control was examined by contrasting trials involving interference or not. The thesis showed that item inhibition carried out by the left inferior frontal cortex (IFC) is involved in proactive control while episodic inhibition carried out by the left IFC and the posterior parietal cortex is involved in reactive control.Item THE NEUROLOGICAL COMPONENTS OF METAMEMORY MONITORING: JOL ACCURACY IN YOUNGER AND OLDER ADULTS(2012-09-05) Haber, Sara; Logan, Jessica M.; Beier, Margaret E.; Dannemiller, James L.; Grandy, Richard E.; Beauchamp, Michael S.Because maximizing the learning of new material is a relevant concern for most individuals, understanding the specific processes involved could be beneficial for people of all ages. Both encoding and monitoring occur during the learning acquisition phase, yet monitoring accuracy and subsequent neural activation have been relatively ignored in the literature. The current research adapts a common metacognitive paradigm using Judgments of Learning (JOLs) to explore the neural differences in monitoring between younger (18-25) and older (65+) adults. Participants were asked to remember natural scenes and predict encoding success by providing a JOL response for each item. Participants were told to respond “will remember” if they believed they would remember that item on a later recognition memory test or “will forget” if they thought they would forget that item on a later recognition memory test. Actual memory performance was compared to predicted memory performance to provide a measure of monitoring accuracy. Individuals reported a JOL response for 150 intact (Easy) and 150 scrambled (Difficult) scenes while in a 3.0T fMRI scanner. Despite minimal differences in behavioral performance, there were several age-related neuroimaging findings of note. When compared to younger adults, older adults had decreases in medial temporal lobe (MTL) activation, as well as contralateral recruitment of the anterior cingulate. Most importantly, the present study also disambiguated structures related to encoding success (the right parahippocampus) and monitoring accuracy (the anterior cingulate). A novel account of neural structures that mediate monitoring is provided both across items varying in difficulty (Easy and Difficult) and across different age groups (Young and Old). Encoding and monitoring are important for learning acquisition and the present research provides the first account that successfully disambiguates the two processes. Results are discussed in reference to their educational implications on resource allocation during the learning of new material.