2012 — 2014 |
Pratte, Michael S |
F32Activity Code Description: To provide postdoctoral research training to individuals to broaden their scientific background and extend their potential for research in specified health-related areas. |
Continuously Decoding Visual Perception and Working Memory
DESCRIPTION (provided by applicant): Early visual areas encode detailed visual input through feature-based coding, thereby providing an ecient code for representing ne-grained dierences between visual stimuli. For example, neurons in V1 respond selectively to particular retinotopic locations, orientations, spatial frequencies, colors, motion directions, and binocular dis- parities. We have learned a great deal regarding these feature-tuning properties from neurophysiology studies. More recently, fMRI studies utilizing pattern classication techniques have allowed for the examination of feature- tuning properties in the human visual system. In these studies, researchers train a classier on fMRI activity to discriminate between activity patterns associated with a small set of stimulus conditions, and discrimination accuracy provides a measure of how much information those areas convey about the stimulus conditions. For example, it is possible to discern which of eight orientations a participant is viewing from fMRI activity patterns in V1, and similar approaches have been successful in identifying other feature-based response patterns. However, the stimulus dimensions of interest, such as orientation, motion or color are typically continuous variables that can take on any value within some range. Moreover, the cortical response patterns associated with these stimulus variables likely vary on a continuum. The goal of this proposal is to develop methods that account for relationships between fMRI activation patterns and the actual value of a feature experienced on some dimension, rather than discriminating between a small set of values. The existence of such continuous decoding methods will provide for a far richer set of experimental paradigms than are currently possible, allowing for novel investigations into how features are represented in visual cortex. The goal of Aim 1 is to use continuous decoding to extract ne-grained information about orientation-selective responses from the human visual cortex. The goal of Aim 2 is to inves- tigate the relationship between these orientation-selective responses and perceptions of orientation by applying continuous decoding during experiences of visual illusions. The goal of Aim 3 is to study relationships between behavioral performance on a working memory task and cortical representations of the remembered features in the absence of visual stimulation. The overall objective of this fellowship is to train the applicant in the use o fMRI, with an emphasis on decoding methods. In addition, the applicant will be trained in the eld of vision science through directed reading, weekly seminars, and course work taught by faculty in the Vanderbilt Vision Research Center. This training will make possible the applicant's long-term goal of becoming an independent researcher, developing novel analytic techniques for functional imaging data and using them to further our understanding of the neural bases of visual perception and higher-order cognition. PUBLIC HEALTH RELEVANCE: The goal of this research training plan is to develop and apply novel methods for studying relationships between visual feature perception and brain activity. Such advancements are critical for understanding how processes such as vision and working memory depend on the central nervous system, and how these functions may be impaired by disease, aging, or neurological disorders.
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0.948 |
2017 |
Pratte, Michael S |
R15Activity Code Description: Supports small-scale research projects at educational institutions that provide baccalaureate or advanced degrees for a significant number of the Nation’s research scientists but that have not been major recipients of NIH support. The goals of the program are to (1) support meritorious research, (2) expose students to research, and (3) strengthen the research environment of the institution. Awards provide limited Direct Costs, plus applicable F&A costs, for periods not to exceed 36 months. This activity code uses multi-year funding authority; however, OER approval is NOT needed prior to an IC using this activity code. |
Mechanisms and Neural Correlates of Iconic Memory Decay @ Mississippi State University
Project Summary The iconic memory system stores a snapshot of incoming visual information, and is characterized by its brief du- ration but large storage capacity. Information from iconic memory is transferred to visual working memory (VWM), which is characterized by its very limited storage capacity. The limitation of information storage in VWM is often characterized as an all-or-none process, whereby information is either successfully stored or it is lost completely. This view raises a simple question: If the majority of perceived visual information is initially stored in iconic memory, but one second later most of it is completely absent from VWM, what happened to it? Characterizing the nature of how information is lost during the process of iconic memory decay is a critical step toward understanding this memory system, which plays a fundamental role in almost all aspects of vision, including our fluid visual percep- tion of the world across time and eye movements. Moreover, deficits in iconic and working memory have been implicated in may psychological disorders including Schizophrenia, Alzheimer?s Disease and children with ADHD, and a better understanding of how iconic memory works and how to measure it may provide a basis for studying several psychological disorders in ways that are not currently possible. Here we first seek to characterize how the precision and storage capacity of iconic memory change over time. In preliminary experiments we observe a clear dissociation: Iconic decay results from a rapidly shrinking capacity, evidence by the complete loss of more and more items over time. However, the precision of those items that are retained in memory does not decrease over time. This result implies that the way in which visual information decays in iconic memory is a highly complex process that involves higher-level visual representations, and that the discrete-capacity limit often attributed to working memory may in fact result from iconic memory processes. In this proposal we systematically character- ize both the behavioral and neural signatures of this capacity-limiting iconic memory decay process. Part of this work involves the development of new mathematical models, capable of characterizing how different pieces of information decay differently in iconic memory. This modeling framework will provide a new approach for assess- ing how different types of information are represented in and lost from iconic memory, and will allow for a more accurate characterization of the time course of decay than is currently possible. In addition, a novel neuroimaging approach is developed that allows the neural signatures of information loss in iconic and working memory to be tracked with high temporal resolution using EEG. Taken together, the developed behavioral paradigms, mathe- matical models, and neuroimaging techniques comprise a new framework that is capable of characterizing the mechanisms that underlie the iconic and working memory systems with a far greater resolution than is currently possible. By using this framework to shed light on the nature of information representation and loss in iconic memory, our results will provide new avenues for conceptualizing, testing and diagnosing the many psychological disorders that are associated with this fundamental part of our perception and cognition.
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2021 |
Pratte, Michael S |
R15Activity Code Description: Supports small-scale research projects at educational institutions that provide baccalaureate or advanced degrees for a significant number of the Nation’s research scientists but that have not been major recipients of NIH support. The goals of the program are to (1) support meritorious research, (2) expose students to research, and (3) strengthen the research environment of the institution. Awards provide limited Direct Costs, plus applicable F&A costs, for periods not to exceed 36 months. This activity code uses multi-year funding authority; however, OER approval is NOT needed prior to an IC using this activity code. |
Temporal Dynamics and Selection Mechanisms of Visual Memory Consolidation @ Mississippi State University
Project Summary Our ability to hold information in working memory is related to almost every aspect of our cognition, including ?uid intelligence. De?cits in working memory have been implicated in many psychological disorders including Schizophrenia, Alzheimer's Disease, ADHD, and in normal aging. However, even after decades of research, many fundamental questions about the mechanisms underlying working memory remain unanswered. We have demonstrated that several experimental results which have been thought to characterize visual working memory in fact re?ect fundamentally different processes, including visual sensory memory and response strategies. Here we propose to further isolate memory storage mechanisms from other processes, so that accurate theories of information processing and storage can be developed. In particular, we propose a comprehensive approach for characterizing the nature of how visual information is transferred into the working memory store, a process termed memory consolidation. The development of novel behavioral paradigms, mathematical modeling techniques and neurophysiological techniques will provide a platform for examining the process of visual memory consolidation with unprecedented precision. By characterizing the mechanisms of consolidation, the results of this work will also be informative for the many processes related to it including attention and working memory storage. We ?rst examine the small number of previous studies on consolidation, and suggest that recent research on working memory retention explains why these studies have provided con?icting results. An experimental approach for examining the consolidation process is developed that mitigates these issues by removing retention intervals from memory paradigms. Preliminary results show that doing so provides a parsimonious experimental design that is uniquely powerful for examining the time course of memory consolidation. In Aim 1 this approach is used to characterize properties of consolidation for color, shape, and face information. Comparing the results across these levels of visual complexity will provide novel insights into memory consolidation and storage. In Aim 2 a similar approach is used to examine not only how visual features are consolidated, but also how the binding between multiple features of an object becomes consolidated into working memory over time. By examining the mechanisms of consolidating feature bindings, the results will also shed light on how this information is eventually represented within working memory. Whereas these and previous experiments consider the consolidation of very brie?y presented information, in natural environments we may spend several seconds encoding a scene. Therefore, the goal of Aim 3 is to use this new paradigm, combined with eye tracking electrophysiological approaches (EEG), to measure how visual information is dynamically consolidated during extended viewing periods. Taken together the results of these studies will greatly advance our understanding of how visual information gets consolidated into memory. Moreover, the development of new experimental and analytic approaches will provide research tools that will be useful in many areas of psychological research.
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