Reaching towards a visual target is ubiquitous in daily life. The task seems effortless, yet requires substantial processing to accomplish. Our goal is to better understand the visuospatial information processing underlying action. For this purpose, we use visually-guided reaching in the non-human primate as a model system.
Our first aim i s to determine the specific contributions of posterior parietal areas to the kinematics and dynamics of visually-guided reaching. We will use a novel method to precisely localize the sites of reversible injections placed throughout the intraparietal sulcus. After each injection we will test animals on a panel of tasks (reaches, saccades and visual search) and then image the site of inactivation. This method is comprehensive and better indicates the true functional contributions of parietal areas than can be achieved through single unit recording.
Our second aim i s to identify and quantify components of activity in posterior parietal cortex that are related to bimanual coordination. Primates commonly use the two arms together to accomplish tasks that are difficult or impossible to perform with a one arm. Clinical evidence suggests a role of the parietal cortex in bimanual coordination. Our results will help distinguish between two specific models of how bimanual coordination might be manifest at the level of individual neurons.
Our third aim i s to quantify the activity of posterior parietal neurons during evaluation of targets and decision-making in performing reaches, and to compare that activity to that observed during decision-making for saccadic eye movements. Recent work has suggested a specific model for decision-making for saccadic eye movements. Our results will indicate whether parietal circuits for target evaluation and decision circuits are the same or different for different kinds of action (reaches versus saccades). Achieving these aims will help us understand the early processes involved in sensory to motor transformation, motor coordination, and decision-making. The results will critically inform the devise of rational strategies for aiding recovery from strokes and other central damage, as well as the design of optimal brain interfaces for a new generation of prosthetic devices.

Public Health Relevance

The central goal of this proposal is to understand the early processing of visuospatial information for visually- guided reaching. Achieving this goal will help clinicians to understand and ultimately reverse the damage caused by parietal and occipital strokes and other brain trauma. Understanding how the brain generates and represents plans for movement is also critical to the development of promising neuroprosthetics for patients with amputations, spinal cord injuries, and disorders such as amyotrophic lateral sclerosis.

National Institute of Health (NIH)
National Eye Institute (NEI)
Research Project (R01)
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Central Visual Processing Study Section (CVP)
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Steinmetz, Michael A
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Washington University
Schools of Medicine
Saint Louis
United States
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Papadimitriou, Charalampos; Ferdoash, Afreen; Snyder, Lawrence H (2015) Ghosts in the machine: memory interference from the previous trial. J Neurophysiol 113:567-77
Yttri, Eric A; Wang, Cunguo; Liu, Yuqing et al. (2014) The parietal reach region is limb specific and not involved in eye-hand coordination. J Neurophysiol 111:520-32
Patel, Gaurav H; Kaplan, David M; Snyder, Lawrence H (2014) Topographic organization in the brain: searching for general principles. Trends Cogn Sci 18:351-63
Mooshagian, Eric; Wang, Cunguo; Ferdoash, Afreen et al. (2014) Movement order and saccade direction affect a common measure of eye-hand coordination in bimanual reaching. J Neurophysiol 112:730-9
Yttri, Eric A; Liu, Yuqing; Snyder, Lawrence H (2013) Lesions of cortical area LIP affect reach onset only when the reach is accompanied by a saccade, revealing an active eye-hand coordination circuit. Proc Natl Acad Sci U S A 110:2371-6
Kubanek, Jan; Snyder, Lawrence H; Brunton, Bingni W et al. (2013) A low-frequency oscillatory neural signal in humans encodes a developing decision variable. Neuroimage 83:795-808
Kubanek, J; Wang, C; Snyder, L H (2013) Neuronal responses to target onset in oculomotor and somatomotor parietal circuits differ markedly in a choice task. J Neurophysiol 110:2247-56
Chang, Steve W C; Snyder, Lawrence H (2012) The representations of reach endpoints in posterior parietal cortex depend on which hand does the reaching. J Neurophysiol 107:2352-65
Liu, Yuqing; Yttri, Eric A; Snyder, Lawrence H (2010) Intention and attention: different functional roles for LIPd and LIPv. Nat Neurosci 13:495-500
Patel, Gaurav H; Shulman, Gordon L; Baker, Justin T et al. (2010) Topographic organization of macaque area LIP. Proc Natl Acad Sci U S A 107:4728-33

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