Everyday activities like reaching for our morning coffee depend on a well-orchestrated coupling of where we look with our eyes and where we reach with our hand. Over a century of research has contributed to our understanding of how saccadic eye movements occur in concert with arm and hand movements. The onset and acceleration of hand movements occur at reliable times with respect to the saccade, suggesting common or inter-related control mechanisms.
Despite the wealth of behavioral literature, little is known about how brain computes the necessary transformations to link coordinated eye-hand movements. Situated in the dorsal stream of the visual system, the PPC has a well-established role in visually-guided behavior and is critical for the coordination of visual behavior. Damage to the PPC gives rise to sensory-motor deficits such as optic ataxia, the inability to accurately reach to visually presented targets. Within the PPC, area LIP sits has a well-established role in guiding saccadic eye movements. The PRR has been studied for its role in visually-guided reaches.
To test whether the neural activity in the PPC was modulated by coordinated reach and saccade activity, we trained two subjects to perform a series of tasks involving coordinated reaches and saccades and saccades made alone. While subjects performed these tasks, we took simultaneous neural recordings from area LIP and the PRR. We find that coordination significantly changes the activity of individual neurons in area LIP, increasing or decreasing the firing rate when a reach is made with a saccade compared with when a saccade is made alone. Neurons with suppressed firing rates during a coordinated reach and saccade task have higher local SFC within area LIP and neurons with elevated firing rates have higher SFC with the PRR. Neurons with local SFC within area LIP and the LFP in the PPC predict the reaction times of coordinated reaches and saccades. Finally, saccades made immediately after reach completion have longer latencies and the neural activity in area LIP is suppressed. Together, the results make a case for area LIP and the PRR as participants in the network that mediates coordinated eye-hand behaviors.
|Commitee:||Curtis, Clay, Hawken, Michael, Kiorpes, Lynne, McPeek, Robert|
|School:||New York University|
|Department:||Center for Neural Science|
|School Location:||United States -- New York|
|Source:||DAI-B 74/12(E), Dissertation Abstracts International|
|Keywords:||Area lip, Coordination, Eye-hand, Parietal cortex, Reaching, Saccades|
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