Adam C. Snyder, Ph. D. - US grants

DESCRIPTION (provided by applicant): When covertly attending to regions of space where behaviorally relevant information is expected to occur, processing of visual stimuli appearing at those locations is enhanced. Conversely, if a region of space is expected to be a locus of distracting events, processing of stimuli occurring there is attenuated. This latter suppressive process is reflected by retinotopically specific increases of alpha-band (8-15Hz) oscillatory power in the electroencephalogram. Based on the cellular physiology of similar oscillations in animals, it has been proposed that alpha might serve as a functional gating mechanism. Importantly, the network of neural areas that have been found to contribute to the generation of these rhythms, which include frontal, parietal and occipital visual areas and thalamic nuclei are the same areas implicated in several influential theories of attentional operations. Further characterization of the alpha-band measure is needed to determine the extent to which it is epiphenomenal to attentional deployment mechanisms, or rather an endogenous attentional mechanism per se. To date, the alpha-band measure of selective attention has only been characterized with respect to spatial attention. However, attention can also be deployed to non-spatial visual features, such as color or motion parameters, facilitating the processing of subsequent stimuli with the attended feature, independently of its spatial location. The goal of this project is to further characterize the alpha-band attentional measure by testing its spatiotemporal properties in a purely feature-based attention task. To this end, a classic visual spatial selective attention task will be transformed into a purely featural domain. A symbolic cue will inform participants about a task-relevant feature of an upcoming stimulus, while electrical brain activity is recorded at the scalp. The cue and imperative stimuli will be separated by an interval during which no stimulation occurs, the brain activity during which reflects internal preparatory attentional processes. By varying parameters of the cue (such as its informativeness) and imperative stimuli (such as its duration or coherence) contexts will be created for which different attentional sets are advantageous, allowing the assessment of the extent and limits of alpha-band power increases as a mechanism for suppression in biased competition models. PUBLIC HEALTH RELEVANCE: Project Narrative The ability to bias attention in favor of behaviorally relevant aspects of the environment is critical for good mental health. Disruptions of normal attentional function, and in particular the ability to suppress irrelevant information, has been implicated in many psychiatric disorders such as attention deficit disorder, autism spectrum disorders and schizophrenia. The contributions of this project to understanding the neurophysiological mechanisms underlying normal attentional suppression will greatly advance research of disorders involving attention. This work dovetails nicely with ongoing research in our laboratory and with collaborators concerning autism spectrum disorders and schizophrenia.

DESCRIPTION (provided by applicant): The visual world contains more information than the brain can process. Fortunately, we have some ability to influence which sources of information receive processing priority through the mechanism of selective attention, and this ability is critical for daily life. Attention involves coordination across the brain at a global level to contol the balance of processing resources in functionally-specialized brain areas operating at a local level. To date, however, laboratory techniques for investigating the neural bases of attention, such as human scalp EEG and single-unit recordings in primates, have been sensitive to only one of these two levels of operation at a time. The goal of this research project is to combine these two methods in a single comprehensive investigation to characterize how these two levels of brain function, the global and the local, interact during control of selective attention. We hav developed a carefully titrated research strategy that will achieve this overarching goal through three systematic and specific aims. We will begin by establishing baseline measures of the links between correlated variability in small populations of neurons and EEG signals measured at the scalp, both in the spontaneous brain state as well as during basic visual perception. We will then add a layer of complexity by introducing an endogenous selective attention task, enabling us to expand our scope beyond low-level perception to higher-level cognitive processes. Finally, with an eye for potential applications of the knowledge gained from the preceding two aims, we will monitor attention signals with a 'closed-loop' system. This will enable us to monitor the animals' natural attentional fluctuations in order to present stimuli in a contextually optimal fashion. Such a 'brain-state-contingent' system would have clear advantages across a wide range of applications. Since this is a training award, another major goal of this project is the training of Dr. Adam C. Snyder, a promising postdoctoral fellow, in the techniques required for single-unit electrophysiology in non-human primates, as well as the professional practices that will be needed throughout what will undoubtedly be his long and productive career as an independent scientist. At the end of this project, Dr. Snyder will have received first-rate trainin in the practices of primate electrophysiology, which will complement his established and proven expertise in human EEG methods, strengthening his foundation as an innovative and successful neuroscientist. From a scientific perspective, we will have developed a model of attention control that spans local and global levels of brain function. This advancement will not only benefit attention research itself, but will provide a framework for future investigations of other brain processes that similarly operate across a range of spatial scales. An understanding of the functioning of attention in health individuals is essential to guide potential therapeutic interventions in disorders involving deficits in attention, including autism, schizophrenia and attention deficit disorder.

? DESCRIPTION (provided by applicant): The visual world contains more information than the brain can process. Fortunately, we have some ability to influence which sources of information receive processing priority through the mechanism of selective attention, and this ability is critical for daily life. While much research has focused on the effects of attention on information processing, relatively little remains known about how attention states are established. This is because clear effects of attention preparation at the level of single neurons have not been forthcoming. Recently, movement preparation has been linked to activity patterns that can be identified by analyzing dozens of neurons together. Such `high-dimensional' analyses have not been applied to sensory brain areas however, and we reasoned that a similar approach may overcome the barriers to progress in explaining attention preparation in sensory cortex. The goal of this research project is to apply high-dimensional analyses to the neuronal activity in sensory cortex in order to characterize how attention states are established. We have developed a carefully titrated research strategy that will achieve this overarching goal through three systematic and specific aims. We will begin by identifying the activity patterns in visual cortex that correlate with attention and inattention, both in the context of attention to spatial locations and in the context of attention to visual features. We will then add a layer of complexit by analyzing neuronal activity recorded from both visual cortex and frontal cortex -a presumed source of attention control signals -to identify the processes that drive these preparatory attention states. Finally, to test the causal nature of the neuronal correlates identified by the preceding two aims, we will use microstimulation in frontal cortex in an effort to mimic the neural and behavioral effects of attentional preparation. Since this is a career development award, another major goal of this project is the training of Dr. Adam C. Snyder in the high-dimensional analysis methods (under the mentorship of Dr. Byron Yu of Carnegie Mellon University) and experimental techniques (under the mentorship of Dr. Matthew Smith of the University of Pittsburgh) required for the achievement of the research aims, as well as the professional practices that will be needed throughout his career as an independent scientist. At the end of this project, Dr. Snyder will have received first-rate training in the analysis of high-dimensional datasets and practices of primate electrophysiology, strengthening his foundation as an innovative and successful neuroscientist. From a scientific perspective, we will have developed a new model of attention preparation that will overcome a long-standing barrier to progress in attention research. This advancement will not only benefit attention research itself, but will provide a framework for future investigations of other brain processes that involve feedback modulation of sensory processing, such as learning and memory. An understanding of the functioning of attention in health individuals is essential to guide potential therapeutic interventions in disorders involving deficits in attention, including autism, schizophrenia and attention deficit disorder.

? DESCRIPTION (provided by applicant): The visual world contains more information than the brain can process. Fortunately, we have some ability to influence which sources of information receive processing priority through the mechanism of selective attention, and this ability is critical for daily life. While much research has focused on the effects of attention on information processing, relatively little remains known about how attention states are established. This is because clear effects of attention preparation at the level of single neurons have not been forthcoming. Recently, movement preparation has been linked to activity patterns that can be identified by analyzing dozens of neurons together. Such `high-dimensional' analyses have not been applied to sensory brain areas however, and we reasoned that a similar approach may overcome the barriers to progress in explaining attention preparation in sensory cortex. The goal of this research project is to apply high-dimensional analyses to the neuronal activity in sensory cortex in order to characterize how attention states are established. We have developed a carefully titrated research strategy that will achieve this overarching goal through three systematic and specific aims. We will begin by identifying the activity patterns in visual cortex that correlate with attention and inattention, both in the context of attention to spatial locations and in the context of attention to visual features. We will then add a layer of complexit by analyzing neuronal activity recorded from both visual cortex and frontal cortex -a presumed source of attention control signals -to identify the processes that drive these preparatory attention states. Finally, to test the causal nature of the neuronal correlates identified by the preceding two aims, we will use microstimulation in frontal cortex in an effort to mimic the neural and behavioral effects of attentional preparation. Since this is a career development award, another major goal of this project is the training of Dr. Adam C. Snyder in the high-dimensional analysis methods (under the mentorship of Dr. Byron Yu of Carnegie Mellon University) and experimental techniques (under the mentorship of Dr. Matthew Smith of the University of Pittsburgh) required for the achievement of the research aims, as well as the professional practices that will be needed throughout his career as an independent scientist. At the end of this project, Dr. Snyder will have received first-rate training in the analysis of high-dimensional datasets and practices of primate electrophysiology, strengthening his foundation as an innovative and successful neuroscientist. From a scientific perspective, we will have developed a new model of attention preparation that will overcome a long-standing barrier to progress in attention research. This advancement will not only benefit attention research itself, but will provide a framework for future investigations of other brain processes that involve feedback modulation of sensory processing, such as learning and memory. An understanding of the functioning of attention in health individuals is essential to guide potential therapeutic interventions in disorders involving deficits in attention, including autism, schizophrenia and attention deficit disorder.