Anne B. Sereno - US grants

DESCRIPTION(adapted from applicant's abstract): This proposal examines two kinds of working memory-memory for shape and space- at the cellular level using a single unit recording technique in awake behaving rhesus monkeys. Much work suggests that perceptual processing proceeds along two cortical paths in temporal and parietal cortices, often characterized as the 'what' and where pathways, respectively. Both pathways project to regions of prefrontal cortex. Previous work has not been careful in the manipulation of featural and spatial working memory requirements and no study has compared cell response to both kinds of working memory within the same cortical area with identical visual conditions. Using the proposed paradigms, we have just finished recording from posterior parietal and inferior temporal cortices of animals performing these tasks where we found quite different patterns of findings. This study will provide valuable information as to whether working memory of shape and space are physiologically segregated in prefrontal cortex. We will also be able to report exactly how these types of working memory modulate cell response and how this relates to the sensory and motor response of the cell. Further, we will be able to compare the findings directly to data we have obtained from posterior parietal and inferior temporal cortices. Prefrontal cortex has been implicated in a variety of human neurological and mental diseases, including Parkinson's disease. Huntington's chorea, Korsakoff's disease, and schizophrenia. Little work in the neuropsvchology of memory has focused on short-term or working memory. Characterization of mechanisms related to working memory in prefrontal cortex may prove useful for better understanding what role short-term or working memory deficits play in the cognitive and psychiatric abnormalities that are associated with these conditions.

[unreadable] DESCRIPTION (provided by applicant): Visual orienting can be either generated voluntarily via cognitive control or evoked externally (reflexively) via stimulus-driven processes. In addition, orienting may be either covert (attentional shifts) or overt (eye movements). We have proposed a tonic inhibition model of attention and orienting that details specific neural substrates for these processes and their interactions. Given the known disruption of the basal ganglia and frontal lobes in Parkinson's disease (PD), this population represents an ideal test of the model. This proposal will thus carry out a systematic investigation of orienting in PD, and will be the first study to comprehensively examine performance across both of these dimensions (i.e., voluntary vs. reflexive and covert vs. overt) in this population. In the first section we will compare voluntary and reflexive overt orienting in PD and control subjects. Based on our and others' previous research, we expect PD subjects to be deficient in voluntary eye movements but, under certain conditions, to be more efficient in reflexive eye movements. In a second section, we will examine the relative importance of deficient working memory vs. failure to inhibit irrelevant information in explaining poor voluntary performance in PD, both factors having been often proposed as possible explanations for poor performance on voluntary tasks. A third section of the proposal will compare voluntary and reflexive attention in PD and control subjects. No previous study in PD has examined reflexive spatial attention independent of voluntary spatial attention. The final section of the proposal will study the effect of different sensorimotor transformations on visuospatial attention in PD. We have previously found that simple or direct stimulus-response (S-R) mappings show a different attentional time course than do more complex, indirect S-R mappings. PD patients have difficulties with some visuomotor transformations. Hence, we will examine and compare the effects of S-R mappings on attentional paradigms in PD and control subjects. All proposed experiments would systematically manipulate medication status of the PD subjects to clarify the role of medication in alleviating orienting dysfunctions in PD. Despite its obvious importance, we are unaware of any overt or covert orienting studies that have examined this issue. Finally, the results of this proposal will have important implications for our understanding and modeling of the relation between attention and overt orienting.

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

The NSF funded research project conducted by Anne Sereno and Saumil Patel at the University of Houston will use human behavioral experiments and a mathematical model to examine the brain mechanisms underlying reflexive spatial attention in vision. The information processing capability of the human central nervous system (CNS) is limited by factors such as the number of neurons available in the system as well as the way they are connected to each other. These limitations are overcome by mechanisms that either move and aim the sensory organs towards the source of relevant information in the environment (such as head and eye movements) or "aim" the CNS itself towards the relevant information arriving from these sensory organs ("covert" attention). It is well known that visual spatial attention can occur reflexively and automatically without conscious awareness. However, the details of the neural circuitry involved in reflexive spatial attention are still largely unknown. Further, although much of what is known about the neural mechanisms of visual spatial attention has been learned from studying monkeys, there are few, if any, theoretical models that link neurophysiological data from monkeys to human behavioral data. Sereno and Patel's research will begin to fill this gap by extending a physiologically plausible model of reflexive attention to analyze previously collected neural data from monkeys. Recent work suggests that the parietal areas of the brain, previously thought to be largely devoted to spatial processing, and thus important for spatial attention, are also sensitive to stimulus shape. Thus, an additional goal of this research is to determine the role that object shape plays in reflexive spatial attention.

Understanding the neural circuitry of reflexive spatial attention is an important step in linking sensory signals to perception and behavior. This research will provide a theoretical framework for linking physiological data from monkeys to human behavioral data. In particular, the work proposed here will yield insight into how the brain automatically filters information and guides behavior. Knowledge gained from this project may improve the design and performance of machine-vision systems (such as those used in robotics), particularly their ability to automatically focus attention and thus successfully function in crowded environments. This project will also provide unique training for psychology graduate students, with an emphasis on the application of mathematical tools to understanding the workings of the human nervous system.