Rapid and accurate saccadic eye movements are crucial for vision. Since real-world scenes are often crowded with many objects, a fundamental requirement for saccades is the serial selection of single targets from a field of multiple potentil targets. Saccade target selection is subserved by a network of cortical and subcortical brain areas, but we still have little idea of how activity across these areas is coordinated. This projec investigates the interactions among the superior colliculus (SC), the frontal eye field (FEF), and the dorsolateral prefrontal cortex (dlPFC). The SC is regarded as the gateway for eye-movement commands from cortex to reach the brainstem, but perturbations in SC activity do not just affect the execution of saccades; they also influence the selection of eye-movement targets. This raises a key question: Does the SC simply act as a final selection stage before transmitting saccade commands downstream, or does SC activity influence saccadic decision-making in cortex? To answer this, we will simultaneously record isolated neurons and local field potentials from SC and FEF, and apply advanced analysis techniques to reveal the interactions and likely flow of information between these two areas. Next, we will perturb activity in the SC by temporarily inactivating a portion of it, and will determine whether and how selection-related activity in FEF is altered. We will also investigate how frontal cortex influences selection in the SC. Specifically, frontal area dlPFC is thought to be particularly important for selection based on abstract rules or internal goals. We will test this idea and investigate dlPFC's influence on the SC by analyzing simultaneously-recorded activity in the two areas during performance of rule-governed and salience-based selection tasks. Finally, to test for a causal link with dlPFC, we will record behavior and SC activity while dlPFC is temporarily inactivated. The results will not only provide new information about the functional architecture of saccadic decision-making; they will also lead toward a better understanding of how cortical and subcortical brain areas interact in performance of a cognitive task.
Our ability to select appropriate targets from a cluttered visual field is normally taken for granted, and its importance only becomes apparent when it fails, as in cognitive impairments such as attention deficit hyperactivity disorder (ADHD) or unilateral visual neglect, for example. This study will illuminate the interactions within a network of brain areas involved in target selection. The results will bring new insights into the likely causes of target selection deficits, and may eventually lead to improved strategies for diagnosis, rehabilitation or treatment of disorders affecting visual selection.
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