Marian E. Berryhill, PhD - US grants

[unreadable] DESCRIPTION (provided by applicant): The aim of this revised proposal is to further detail the role of the posterior parietal cortex (PPC) in visual short-term memory (VSTM). A number of functional magnetic resonance imaging (fMRI) studies observe bilateral PPC activations during varied VSTM tasks. In contrast, PPC damage is not associated with generalized deficits in VSTM performance. Right PPC damage is known to impair spatial attention while left PPC damage is known to impair processing of numerical magnitude. The conflict between fMRI and patient data suggests several possibilities: VSTM deficits in PPC patients have not been carefully evaluated, or neuroimaging activations are epiphenomenal to VSTM task performance. In preliminary studies, I show that unilateral right PPC patients exhibit general impairment at VSTM for object, spatial and object-spatial VSTM for colors, novel shapes and tools stimulus categories. Left PPC patients do not exhibit general VSTM deficits, performing normally in the VSTM tasks. Bilateral PPC patients with simultanagnosia (the inability to see more than 1 thing at a time) are also globally impaired. Bilateral PPC also demonstrate sensitivity to experimental paradigm and performed worse in old/new VSTM recognition than in comparable recall tasks. The goal of the proposed studies is to investigate the parameters of PPC involvement in VSTM. Unresolved issues are addressed: the mechanism of VSTM impairment (encoding, maintenance, capacity, retrieval), whether recognition paradigms (old/new recognition versus 2 alternative forced-choice) affect bilateral PPC recognition performance, and whether left PPC activitations are due to involvement in processing magnitude. To accomplish this goal, I propose studies examining VSTM using complimentary approaches: neuropsychological studies of unilateral and bilateral parietal patients, as well as functional magnetic resonance imaging (fMRI) with normal subjects. PUBLIC HEALTH RELEVANCE: This set of studies is particularly relevant to the rehabilitation of parietal stroke patients. In the United States, stroke affects approximately 700,000 people annually, is the third leading cause of death, and is the leading cause of serious, long-term disability. Parietal lobe strokes are relatively common and the behavioral consequences on vision and action are devastating. In the proposed studies, VSTM impairments in parietal patients are evaluated. Deficits in VSTM have direct real-world implications relating to cognitive function. These data may provide affordable assessment measures and help guide rehabilitation strategies. [unreadable] [unreadable] [unreadable]

DESCRIPTION (provided by applicant): Working memory (WM) serves as the 'mental workspace' permitting us to maintain and manipulate on-line mental representations of everything from a phone number to the objects around us. Given its critical importance for healthy cognition, it is not surprising that WM impairments can lead to a significant decrease in the quality of life. As such, understanding the behavioral and neuronal mechanisms that underlie healthy WM function is critical to one day developing treatments and interventions to stave off declines in WM performance. In spite of its importance for performing cognitive tasks, a surprising feature of WM is that it is severely capacity limited to ~4 items. One of the mysterie surrounding WM is how and why this capacity limitation arises. One potential source of capacity limitation may arise from how items from the environment are encoded into WM from the numerous possible items around us at any given time. Previous work has relied on behavioral and physiological measures to study factors influencing WM encoding, e.g. manipulations of encoding depth, stimulus number, or stimulus set size. However, all of these previous approaches used indirect measurements of the aggregate processing associated with performing the WM task, and none have focused directly on the processes associated with the encoding of a specific individual stimulus. Here, we propose to apply a powerful event related potential (ERP) technique: Frequency-Tagging, to directly measure the processing of individual items at encoding. This technique has been widely used in the study of visual perception, and here we propose to apply it to perform a comprehensive investigation of WM encoding. The approach entails the presentation of stimuli each flickering on and off at unique flicker rate. Intriguingly, this periodic stimulation leads to corresponding neural oscillations that can be recorded in the electroencephalogram (EEG) and analyzed in the frequency domain by looking at the frequencies at which a stimulus was flickered. The amplitudes of these 'frequency-tags' can be correlated with the behavioral outcomes of whether or not the stimulus is successfully retrieved from WM to obtain a neuronal correlate of WM encoding that is specific to an individual-stimulus. This R15/AREA grant proposal combines the theoretical and technical expertise of two researchers with years of experience studying visual perception and memory. The PIs will work closely with undergraduate and graduate students to advance our understanding of the WM encoding process. Through the proposed experiments, students will receive training in a number of areas (critical to establishing a solid foundation upon which to build future research careers in psychology and neuroscience. This innovative proposal will significantly contribute to the research and educational training goals of the University of Nevada, Reno PUBLIC HEALTH RELEVANCE: Working memory (WM) is a fundamental aspect of cognition that is highly limited in capacity. The fundamental goal of this proposal is to further our understanding of the behavioral and neural mechanisms that underlie healthy WM function. In the long-term, this research may contribute to the development of effective interventions and treatments designed to prevent or alleviate WM impairments. This R15/AREA grant proposal investigates the WM encoding process using a powerful ERP approach called frequency-tagging. We propose the collaboration between two laboratories (Caplovitz Vision Lab and the Berryhill Memory and Brain Lab) to provide student training in multiple experimental techniques to answer longstanding questions in the WM field.

Understanding the Neural Basis of Working IVIemory to Improve WIVI Function The purpose of this proposal is to conduct basic research to understand the neural correlates of working memory. The second purpose is to then apply our findings to improve working memory function in the healthy aging and in those with traumatic brain injury through novel neurostimulation protocols. First, we will use functional neuroimaging (fMRI) to test two contradictory theoretical viewpoints regarding the role of the posterior parietal cortex in working memory. It is important to understand the role of the posterior parietal cortex to appropriately design therapeutic studies for improving working memory. Thus, the results from the first experiments will guide the design and predicted outcomes ofthe applied experiments in which transcranial direct current stimulation (tDCS) is applied to special populations. TDCS is thought to improve cognitive function through several mechanisms. The tDCS technique involves the application of a safe, low level of electrical current to the scalp. The electrical current passes into the cortex and can transiently increase or decrease the likelihood of neurononal firing in the cortex, and it may also increase the activity in white matter tracts to overcome white matter damage. We predict that anodal (+) tDCS applied to the prefrontal and/or parietal cortices, will improve visuospatial and verbal working memory function by increasing the underactivity of cortical activations in the healthy aging. In a longitudinal study of working memory, we will apply parietal, prefrontal or alternating parietal/prefrontal anodal tDCS to separate groups of healthy aging individuals. The duration of improvement will be tested by bringing participants in for a final behavioral session one month after their final tDCS session. The second set of applied experiments will test whether tDCS can also be used effectively to improve cognitive function in participants with mild or moderate traumatic brain injury. In these participants, there is is often white matter damage. We will conduct experiments to see if alternating parietal/prefrontal tDCS stimulation will improve visuospatial or verbal working memory in those with traumatic brain injury.

The University of Nevada, Reno (UNR) proposes to increase the number of well-trained, highly qualified neuroscientists from underrepresented populations. Accelerating the research training of students from underrepresented ethnic/racial groups, students with disabilities, first generation students, and students from lower income backgrounds is central to efforts to broaden participation and enhance inclusiveness in the service of stronger science. UNR is the land grant university of Nevada, and is an R1 institution with a strong tradition of educating students whose access to higher education historically has been limited. Our primary partner and neighbor institution, Truckee Meadows Community College (TMCC), is a Hispanic Serving Institution with an outstanding record of preparing students to transition to upper level undergraduate education at UNR. The proposed Nevada ENDURE program will facilitate an intensive two-year training program for 12- 14 trainees per year. During the academic year, trainees will conduct research and participate in weekly professional development and skills training seminars at UNR. During each summer, trainees will participate in summer research programs at our summer educational partner institutions: the University of California, Berkeley, the University of California, Davis, the University of Michigan, and Stanford University. We propose five activities: (1) To provide scientific skills and research experiences through placements with actively funded neuroscientists, (2) To implement academic curriculum enhancement and professional development activities to augment trainees' research activities, (3) To facilitate effective mentoring by program faculty, (4) To maintain an effective Administrative Core to support trainees' development, evaluate program effectiveness, and disseminate best practices, and (5) To expand the ENDURE network and pipeline of talented underrepresented students to doctoral programs in neuroscience. Our measurable objectives during the requested funding period include: (1) attainment of 85-90% admission to doctoral programs in neuroscience, (2) improvement of trainees' research and quantitative skills, and (3) improvement in trainees' scientific writing and presentation skills.