Cortical Networks for Eye-Hand Coordination in the Human

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Human neuroimaging has successfully mapped the functional anatomy of the cerebral cortex, but we do not yet understand how these cortical areas interact for real world cognition and behavior. For example, it is not known how visual cortex interacts with other sensory and motor areas (i.e., for the eyes, head, arm, & hands) to produce the `simple' eye-hand coordination that underlies most daily behaviors. To investigate these fundamental issues, we will utilize various neuroimaging and brain stimulation techniques, combined with large scale functional connectivity analysis to understand how signals are shared between cortical areas. For this grant period, we will focus on the following scientific issues: 1. Cortical Networks for Allocentric versus Egocentric Coding. In previous studies we identified cortical sites for eye-centred vs. landmark centered memory of reach goals, and sites for their integration. Here we will use neuroimaging to investigate the cortical `hubs' and networks for these functions, perturb them using safe brain stimulation techniques, and then link these by combining neuroimaging with brain stimulation. 2. Cortical Networks for Reach-Grasp Coordination. Cortical reach and grasp areas have been identified, but it is not known how they are coordinated. We will use a cue-separation paradigm (reach and grasp instructions separated in time), combined with decoding and connectivity analysis to identify the hubs and networks that integrate signals for coordinated grasp. 3. Cortical Networks for Reach vs. Placement. Numerous studies have investigated the cortical mechanisms for grasping objects, but few have investigated how the brain controls placement of those objects. We will differentiate these processes, and the influence of eye movements, using neuroimaging and functional connectivity analysis. We hypothesize that the same reach/grasp areas will be activated in both tasks but network modularity will change, with further modifications when eye movements necessitate sharing of information across visual fields. 4. Cortical Networks for Integration of Eye Position into the Reach Plan. An `eye position' region has been identified in somatosensory cortex, but the role of these signals in movement control remains controversial. We will test this by combining neuroimaging and brain stimulation during a task where gaze and reach are dissociated. We hypothesize that stimulation of the eye position area will influence the motor areas, causing gaze-dependent reach errors. This whole-brain approach represents a conceptual turning point for human neuroscience. Specifically, toward understanding how different brain areas share / segregate sensorimotor signals to form functional networks across all four cortical lobes. This has important applications for Canadian healthcare (since these networks are affected by many diseases) and industry (e.g., for inspiring distributed models for adaptive robotic control systems).