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- Creators: Azuma, Tamiko
Description
It is commonly known that the left hemisphere of the brain is more efficient in the processing of verbal information, compared to the right hemisphere. One proposal suggests that hemispheric asymmetries in verbal processing are due in part to the efficient use of top-down mechanisms by the left hemisphere. Most evidence for this comes from hemispheric semantic priming, though fewer studies have investigated verbal memory in the cerebral hemispheres. The goal of the current investigations is to examine how top-down mechanisms influence hemispheric asymmetries in verbal memory, and determine the specific nature of hypothesized top-down mechanisms. Five experiments were conducted to explore the influence of top-down mechanisms on hemispheric asymmetries in verbal memory. Experiments 1 and 2 used item-method directed forgetting to examine maintenance and inhibition mechanisms. In Experiment 1, participants were cued to remember or forget certain words, and cues were presented simultaneously or after the presentation of target words. In Experiment 2, participants were cued again to remember or forget words, but each word was repeated once or four times. Experiments 3 and 4 examined the influence of cognitive load on hemispheric asymmetries in true and false memory. In Experiment 3, cognitive load was imposed during memory encoding, while in Experiment 4, cognitive load was imposed during memory retrieval. Finally, Experiment 5 investigated the association between controlled processing in hemispheric semantic priming, and top-down mechanisms used for hemispheric verbal memory. Across all experiments, divided visual field presentation was used to probe verbal memory in the cerebral hemispheres. Results from all experiments revealed several important findings. First, top-down mechanisms used by the LH primarily used to facilitate verbal processing, but also operate in a domain general manner in the face of increasing processing demands. Second, evidence indicates that the RH uses top-down mechanisms minimally, and processes verbal information in a more bottom-up manner. These data help clarify the nature of top-down mechanisms used in hemispheric memory and language processing, and build upon current theories that attempt to explain hemispheric asymmetries in language processing.
ContributorsTat, Michael J (Author) / Azuma, Tamiko (Thesis advisor) / Goldinger, Stephen D (Committee member) / Liss, Julie M (Committee member) / Arizona State University (Publisher)
Created2013
Description
Often termed the "gold standard" in the differential diagnosis of dysarthria, the etiology-based Mayo Clinic classification approach has been used nearly exclusively by clinicians since the early 1970s. However, the current descriptive method results in a distinct overlap of perceptual features across various etiologies, thus limiting the clinical utility of such a system for differential diagnosis. Acoustic analysis may provide a more objective measure for improvement in overall reliability (Guerra & Lovely, 2003) of classification. The following paper investigates the potential use of a taxonomical approach to dysarthria. The purpose of this study was to identify a set of acoustic correlates of perceptual dimensions used to group similarly sounding speakers with dysarthria, irrespective of disease etiology. The present study utilized a free classification auditory perceptual task in order to identify a set of salient speech characteristics displayed by speakers with varying dysarthria types and perceived by listeners, which was then analyzed using multidimensional scaling (MDS), correlation analysis, and cluster analysis. In addition, discriminant function analysis (DFA) was conducted to establish the feasibility of using the dimensions underlying perceptual similarity in dysarthria to classify speakers into both listener-derived clusters and etiology-based categories. The following hypothesis was identified: Because of the presumed predictive link between the acoustic correlates and listener-derived clusters, the DFA classification results should resemble the perceptual clusters more closely than the etiology-based (Mayo System) classifications. Results of the present investigation's MDS revealed three dimensions, which were significantly correlated with 1) metrics capturing rate and rhythm, 2) intelligibility, and 3) all of the long-term average spectrum metrics in the 8000 Hz band, which has been linked to degree of phonemic distinctiveness (Utianski et al., February 2012). A qualitative examination of listener notes supported the MDS and correlation results, with listeners overwhelmingly making reference to speaking rate/rhythm, intelligibility, and articulatory precision while participating in the free classification task. Additionally, acoustic correlates revealed by the MDS and subjected to DFA indeed predicted listener group classification. These results beget acoustic measurement as representative of listener perception, and represent the first phase in supporting the use of a perceptually relevant taxonomy of dysarthria.
ContributorsNorton, Rebecca (Author) / Liss, Julie (Thesis advisor) / Azuma, Tamiko (Committee member) / Ingram, David (Committee member) / Arizona State University (Publisher)
Created2012
Description
Distorted vowel production is a hallmark characteristic of dysarthric speech, irrespective of the underlying neurological condition or dysarthria diagnosis. A variety of acoustic metrics have been used to study the nature of vowel production deficits in dysarthria; however, not all demonstrate sensitivity to the exhibited deficits. Less attention has been paid to quantifying the vowel production deficits associated with the specific dysarthrias. Attempts to characterize the relationship between naturally degraded vowel production in dysarthria with overall intelligibility have met with mixed results, leading some to question the nature of this relationship. It has been suggested that aberrant vowel acoustics may be an index of overall severity of the impairment and not an "integral component" of the intelligibility deficit. A limitation of previous work detailing perceptual consequences of disordered vowel acoustics is that overall intelligibility, not vowel identification accuracy, has been the perceptual measure of interest. A series of three experiments were conducted to address the problems outlined herein. The goals of the first experiment were to identify subsets of vowel metrics that reliably distinguish speakers with dysarthria from non-disordered speakers and differentiate the dysarthria subtypes. Vowel metrics that capture vowel centralization and reduced spectral distinctiveness among vowels differentiated dysarthric from non-disordered speakers. Vowel metrics generally failed to differentiate speakers according to their dysarthria diagnosis. The second and third experiments were conducted to evaluate the relationship between degraded vowel acoustics and the resulting percept. In the second experiment, correlation and regression analyses revealed vowel metrics that capture vowel centralization and distinctiveness and movement of the second formant frequency were most predictive of vowel identification accuracy and overall intelligibility. The third experiment was conducted to evaluate the extent to which the nature of the acoustic degradation predicts the resulting percept. Results suggest distinctive vowel tokens are better identified and, likewise, better-identified tokens are more distinctive. Further, an above-chance level agreement between nature of vowel misclassification and misidentification errors was demonstrated for all vowels, suggesting degraded vowel acoustics are not merely an index of severity in dysarthria, but rather are an integral component of the resultant intelligibility disorder.
ContributorsLansford, Kaitlin L (Author) / Liss, Julie M (Thesis advisor) / Dorman, Michael F. (Committee member) / Azuma, Tamiko (Committee member) / Lotto, Andrew J (Committee member) / Arizona State University (Publisher)
Created2012
Description
Cognitive deficits often accompany language impairments post-stroke. Past research has focused on working memory in aphasia, but attention is largely underexplored. Therefore, this dissertation will first quantify attention deficits post-stroke before investigating whether preserved cognitive abilities, including attention, can improve auditory sentence comprehension post-stroke. In Experiment 1a, three components of attention (alerting, orienting, executive control) were measured in persons with aphasia and matched-controls using visual and auditory versions of the well-studied Attention Network Test. Experiment 1b then explored the neural resources supporting each component of attention in the visual and auditory modalities in chronic stroke participants. The results from Experiment 1a indicate that alerting, orienting, and executive control are uniquely affected by presentation modality. The lesion-symptom mapping results from Experiment 1b associated the left angular gyrus with visual executive control, the left supramarginal gyrus with auditory alerting, and Broca’s area (pars opercularis) with auditory orienting attention post-stroke. Overall, these findings indicate that perceptual modality may impact the lateralization of some aspects of attention, thus auditory attention may be more susceptible to impairment after a left hemisphere stroke.
Prosody, rhythm and pitch changes associated with spoken language may improve spoken language comprehension in persons with aphasia by recruiting intact cognitive abilities (e.g., attention and working memory) and their associated non-lesioned brain regions post-stroke. Therefore, Experiment 2 explored the relationship between cognition, two unique prosody manipulations, lesion location, and auditory sentence comprehension in persons with chronic stroke and matched-controls. The combined results from Experiment 2a and 2b indicate that stroke participants with better auditory orienting attention and a specific left fronto-parietal network intact had greater comprehension of sentences spoken with sentence prosody. For list prosody, participants with deficits in auditory executive control and/or short-term memory and the left angular gyrus and globus pallidus relatively intact, demonstrated better comprehension of sentences spoken with list prosody. Overall, the results from Experiment 2 indicate that following a left hemisphere stroke, individuals need good auditory attention and an intact left fronto-parietal network to benefit from typical sentence prosody, yet when cognitive deficits are present and this fronto-parietal network is damaged, list prosody may be more beneficial.
Prosody, rhythm and pitch changes associated with spoken language may improve spoken language comprehension in persons with aphasia by recruiting intact cognitive abilities (e.g., attention and working memory) and their associated non-lesioned brain regions post-stroke. Therefore, Experiment 2 explored the relationship between cognition, two unique prosody manipulations, lesion location, and auditory sentence comprehension in persons with chronic stroke and matched-controls. The combined results from Experiment 2a and 2b indicate that stroke participants with better auditory orienting attention and a specific left fronto-parietal network intact had greater comprehension of sentences spoken with sentence prosody. For list prosody, participants with deficits in auditory executive control and/or short-term memory and the left angular gyrus and globus pallidus relatively intact, demonstrated better comprehension of sentences spoken with list prosody. Overall, the results from Experiment 2 indicate that following a left hemisphere stroke, individuals need good auditory attention and an intact left fronto-parietal network to benefit from typical sentence prosody, yet when cognitive deficits are present and this fronto-parietal network is damaged, list prosody may be more beneficial.
ContributorsLaCroix, Arianna (Author) / Rogalsky, Corianne (Thesis advisor) / Azuma, Tamiko (Committee member) / Braden, B. Blair (Committee member) / Liss, Julie (Committee member) / Arizona State University (Publisher)
Created2019
Description
It has been suggested that directed forgetting (DF) in the item-method paradigm results from selective rehearsal of R items and passive decay of F items. However, recent evidence suggested that the passive decay explanation is insufficient. The current experiments examined two theories of DF that assume an active forgetting process: (1) attentional inhibition and (2) tagging and selective search (TSS). Across three experiments, the central tenets of these theories were evaluated. Experiment 1 included encoding manipulations in an attempt to distinguish between these competing theories, but the results were inconclusive. Experiments 2 and 3 examined the theories separately. The results from Experiment 2 supported a representation suppression account of attentional inhibition, while the evidence from Experiment 3 suggested that TSS was not a viable mechanism for DF. Overall, the results provide additional evidence that forgetting is due to an active process, and suggest this process may act to suppress the representations of F items.
ContributorsHansen, Whitney Anne (Author) / Goldinger, Stephen D. (Thesis advisor) / Azuma, Tamiko (Committee member) / Brewer, Gene (Committee member) / Homa, Donald (Committee member) / Arizona State University (Publisher)
Created2011
Description
The present study examined the effects that mild traumatic brain injury (mTBI) has on an individual’s episodic memory by looking at participants’ abilities to recall stories both immediately after being verbally told and after a delay. Thirty-seven participants were sorted into a control group (N=27) and a mTBI group (N=10) and then given the Wechsler Memory Scale’s two subtests, Logical Memory I and Logical Memory II. Logical Memory I consists of two verbally given stories in which the participant immediately retells the story to the assessor with as much detail and original vocabulary as they can remember. Logical Memory II has the participants, without prior knowledge, retell the same two stories after a thirty-minute delay. Once recorded, researchers transcribed and scored the participants’ story recalls, gathering data on what errors, correct ideas, and vocabulary the participants made and remembered. The data was then analyzed through an Analysis of Variance (ANOVA), looking at the interaction of Story (of the two stories that the participants were told), Group (whether mTBI or control) , and Delay (whether it was the immediate or delayed recall). Trends in the data show that participants with a history of mTBI do more poorly than the control group proving that memory is affected by acquired brain injury and that further studies to examine how and why this is the case are needed.
ContributorsAndrews, Chaley (Author) / Azuma, Tamiko (Thesis director) / Ratiu, Ileana (Committee member) / Barrett, The Honors College (Contributor) / College of Health Solutions (Contributor) / Sanford School of Social and Family Dynamics (Contributor)
Created2023-05
Description
The emotional enhancement of memory (EEM) has consistently suggested that memory performance is enhanced for positively and negatively valenced stimuli. Heightened arousal and activation of the noradrenergic system facilitates encoding and the formation of memory traces. However, this EEM can become maladaptive when coupled with the heightened noradrenergic activity associated with posttraumatic stress disorder (PTSD). This heightened noradrenergic response can result in chronic intrusive memories of past traumatic events. This study aims to explore overall recall, retrieval dynamics, output editing, and intrusions as a function of emotional content and prior history with traumatic experiences. Undergraduate students (N=249) from Arizona State University completed a battery surveys measuring PTSD symptomatology and other related constructs including anxiety, depression, and trauma. Participants then completed a memory task, an externalized free recall task for multiple study-blocks utilizing word list stimuli. During recall, participants were instructed to report every word that came to mind regardless of whether it was present or not in the most recent study-block, then make a judgment about recent-list membership. Main effects of valence were found for recall accuracy, intrusion generation, and successful editing. This suggests that the emotional enhancement of memory does in fact play a role in intrusion generation and the ability to edit out false recollections. Only depression levels resulted in a significant interaction effect with valence, specifically when measuring intrusion generation. This suggests that trauma level does not play a significant role in emotional intrusion memory.
ContributorsDziendziel, Hailey K (Author) / Brewer, Gene A (Thesis advisor) / Azuma, Tamiko (Committee member) / Lewis, Candace (Committee member) / Arizona State University (Publisher)
Created2023