Edward J. Golob - US grants

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).

The ability to use spatial information is crucial to survival because space is such a basic feature of the world. Our brains are endowed with circuits that represent spatial information, which can then be used to guide intelligent behavior. The auditory system is particularly important for spatial cognition because our ears can detect sounds coming from any direction, which affords panoramic sensitivity to events happening in the environment. We take the ability to use spatial information for granted because everyday activities, such as hearing a friend call our name and turning in their direction to wave in response, seem so automatic. However, this sense of automaticity is the product of delicate interactions between representions of spatial information and their application by other cognitive systems. With support from the National Science Foundation, Dr. Edward Golob and colleagues at Tulane University will study how auditory spatial information is used by higher-level cognitive processes in the brain. The experiments focus on the interface between representing sound location and two cognitive functions that prioritize subregions of space: spatial attention and motor responses. In a series of studies, human subjects will perform various auditory spatial tasks. During performance, sensors will monitor electrical brain activity, and brief magnetic pulses will be applied to influence brain activity. These experiments will identify properties of spatial attention gradients, and relate the findings to auditory cortical processing and the role of posterior parietal cortex. Studies examining interactions between the auditory and motor systems will determine if auditory processing is influenced by location of the hands and, conversely, whether sound location influences motor cortex activity.

This project will help provide a deeper understanding of how spatial information is used by other cognitive systems and the neural networks that support these interactions. The results may also be applied to improving human-machine interfaces and to improving rehabilitation techniques for patients with brain damage. This research and integrated education plan will promote undergraduate and graduate education in New Orleans. A collaboration between Tulane and Xavier will offer research opportunities to undergraduates that will culminate in a Masters degree, with a focus on minority participation and infrastructure enhancement.

Normal aging is accompanied by declines in cognitive control that are mediated, in part, by compromised prefrontal cortex function. However the repercussions of prefrontal changes on other cortical structures recruited for cognitive control are not well understood. In this project control of auditory spatial attention will be used to study interactions between prefrontal and posterior cortical regions, and how these interactions are affected by age and task demands. Our overarching hypothesis is that age-related changes in cognitive control are mediated by network level impairments in coordination between prefrontal and parietal/temporal lobe areas. Corollary hypotheses are that aging is associated with constrained spatial attention gradients (Aim 1), and greater sensitivity of spatial orienting to perceptual and short-term memory load manipulations (Aim 2), both of which can be improved by magnetic stimulation of cortex (Aim 3). Methods include using EEG and event-related potentials to define cortical processing and interactions between prefrontal and posterior areas. Spatial gradients will be mapped by presenting acoustic virtual reality stimuli from locations in the frontal azimuth plane during task performance. Transcranial magnetic stimulation will be used to temporarily influence prefrontal cortical activity. The effects of transcranial magnetic stimulation will be assessed using behavioral and EEG/event-related potential measures. Three Specific Aims are proposed. In Aim 1 age differences in spatial attention gradients will be assessed using neuroelectric measures of automatic (mismatch negativity) and controlled (P3a) processing of distractor stimuli. Aim 2 will test the hypothesis that declines in cognitive control are associated with reduced perceptual capacity and greater proactive interference in short-term memory. Separate experiments will parametrically vary perceptual or short-term memory load, with a separate assessment of high vs. low proactive interference conditions in the memory load experiments. Aim 3 will determine if magnetic stimulation of cortex can broaden spatial attention gradients and improve performance on cognitive control tasks.

? DESCRIPTION (provided by applicant): Hearing can serve as an early warning system because it can panoramically monitor the environment for events happening at a distance or out of sight. These ecological considerations make the auditory system particularly useful for studying mechanisms for shifting spatial attention. The focus of this project is on the interplay between top-down and bottom-up spatial attention biases that govern shifting auditory attention to distractors during performance of a simple spatial attention task. The overall goal of this proposal is to use an interdisciplinary approach to better understand at the cognitive and neural levels of analysis how auditory attention is distributed over space. We will test the hypothesis that the spatial distribution of auditory attentional emerges from interactions among two basic factors. The first factor is a voluntary (top-down) attention bias that weakens with distance from the current focus of attention. Conversely, the second factor is an automatic (bottom-up) bias that is tuned to shift attention to unexpected events away from the current focus of attention. The first aim tests a computational model of top-down and bottom-up attention bias in shifting auditory spatial attention. Different aspects of the model will be quantitatively tested against findings from behavioral experiments, and observations will be used to further develop the model. The computational model will incorporate artificial intelligence methods to represent human cognitive processes. The second aim uses transcranial magnetic stimulation to test the role of key right hemisphere cortical areas in shifting of auditory spatial attention. We focus on neural mechanisms of bottom-up attentional bias. The third aim tests whether auditory attention gradients become less focused over time. This will determine how gradients relate to cognitive resources and neural blood flow measures that are known to decline with extended vigilance. This project will help advance knowledge in the field of auditory attention and cognitive hearing, and also addresses general issues in attention research such as top-down and bottom-up processes, vigilance, and their relations to neurobiological attention networks. Outcomes will have practical significance because shifting auditory attention is vital for avoiding accidents at ll ages, maintaining independent living at older ages, and is applicable to neurological and psychiatric disorders having attentional impairments (e.g. PTSD, attention deficit disorder, schizophrenia, stroke, dementia).

Project summary Brain dynamics that drive variability within and between patients are an important, but poorly understood, element of many cognitive disorders. The long-term goal of this research project is to develop technology that will identify brain activity patterns associated with successful performance on a given task, and use this pattern as a target for brain-computer interface (BCI) training. The overarching hypothesis is that using BCI training to more often have a brain state that is spontaneously correlated to good performance will, in turn, improve overall performance. This approach could be developed into a powerful tool for rehabilitation and therapy for many neurological and psychiatric disorders. Here we will investigate persistent developmental stuttering (PDS) as a model to study brain dynamics associated with successful vs. unsuccessful performance. PDS is a speech disorder where fluent speech is punctuated to various degrees by stuttering. Individuals with PDS are otherwise neurologically in the normal range, which avoids complicating factors in most patient populations. Stuttering is intermittent; thus on some occasions the brain is in a state conducive to fluent speech and at other times it is not. We propose to use EEG activity shortly before speaking to predict whether somebody with PDS will stutter or speak fluently. Preliminary data are given to show proof of concept with traditional EEG analysis methods. This approach will be expanded by first using advanced methods such as common spatial pattern analysis and machine learning over multiple subject sessions to identify EEG signals that distinguish fluent vs. dysfluent trials (Aim 1). PDS subjects will then be trained to produce and maintain their EEG pattern that is most strongly associated with fluent speech by using BCI methods. We hypothesize that individuals will learn to modulate EEG features to be more consistent with fluent trials, which in turn will significantly reduce stuttering rate. After successful completion of this project we envision a new BCI-based intervention that can be used to encourage neural states conducive to fluent speech in those who stutter. The BCI intervention would complement traditional speech therapy using behavioral methods. The ?two-step approach? of first identifying brain states associated with a patient?s best performance followed by BCI training to enter that state more often can be applied to rehabilitation in many other neurological and psychiatric disorders, such as Alzheimer?s disease, traumatic brain injury, and mood disorders, to name a few.