The first goal of these experiments is to delineate how brain areas in posterior parietal cortex of New World cebus monkeys operate within a cortical network that is critical for reaching, grasping and bimanual behaviors. The second goal is to extend our ongoing collaboration with faculty at the Instituto de Biofisica Carlos Chagas Filho (IBCCF;Drs. Franca, Gattass, Fiorani and Soares) at the Federal University of Rio de Janeiro, Brazil by introducing a new technology that was developed as a joint project between laboratories at the Center for Neuroscience (Krubitzer) and Department of Biomedical Engineering (Simon) at UC Davis. Cebus monkeys, like humans, have an opposable thumb, utilize a precision grip and engage in a variety of complex manual behaviors. Their use of tools in both the wild and laboratory settings make cebus monkeys an excellent model for understanding the neural basis of complex manual abilities in humans, more so than the commonly used macaque monkey, which rarely uses tools. The new technology that this international consortium will introduce to IBCCF is the microfluidic cooling device. This is an indwelling and biocompatible device that can selectively and reversibly deactivate one or more brain areas in awake animals performing a trained task. This is equivalent to reversibly 'lesioning'a brain area and will enable us to probe the function of the affected area by detection of specific deficits in behavior during deactivation. Using this device we can compare similarities in cortical circuits between Old World macaque monkeys and New World cebus monkeys that are involved in coordinated hand use, and define differences in circuits that have arisen in conjunction with tool use in cebus monkeys. These studies have important clinical relevance because they will reveal the relationship between the size of a deactivated area and the extent of behavioral dysfunction and recovery that is possible. Application of this device simulates a calibrated clinical lesion and provides a novel approach to assess the effects of progressively larger "lesions" such as can occur during stroke in humans.
Humans are highly dexterous animals, and bimanual dexterity is critical for even the most rudimentary tasks that humans perform daily. The importance of these abilities is particularly marked when parietal cortical areas that lie at the core of these abilities are lost due to stroke or lesions, and severe deficits such as optic ataxias, dystonias, choreas, and neglect occur. The proposed studies will examine posterior parietal areas involved in manual behaviors and tool use in an important non-human primate model, the cebus monkey, and the behavioral deficits that arise when these areas are deactivated.