Functions of the thalamus in attention and perception

Princeton University, Princeton NJ

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Abstract

PROJECT SUMMARY The visual thalamus has been extensively studied in terms of its anatomical organization, connectivity patterns, and basic neural response properties. However, its role in perception and cognition has remained poorly understood. The present application is a competing renewal submission for our grant “Functions of the thalamus in perception and cognition” (RO1-EY017699). Pulvinar is the largest nucleus in the primate thalamus and is considered a higher-order nucleus, because it forms input-output loops almost exclusively with cortex. In addition to cortical inputs, pulvinar also receives projections from the superior colliculus (SC) – a midbrain area controlling saccadic eye movements and spatial attention. From an anatomical perspective, pulvinar is ideally positioned to regulate the transmission of information to cortex and between cortical areas to influence perceptual and cognitive processes. Evidence from lesion studies in humans and monkeys demonstrates a critical involvement of pulvinar in a number of fundamental cognitive functions, including orienting responses and the filtering of unwanted information. Our studies during the last funding cycle have begun to establish neural correlates that may underlie some of these functions. By using simultaneous multi-site recordings in fronto-parietal cortex and pulvinar, we (i) established a link of pulvinar population responses predicting attention behaviors and (ii) defined a specific role for functional interactions between pulvinar and the lateral intraparietal area (LIP) in regulating temporal population dynamics during spatial attention. This application extends this work to further a causal role of the macaque pulvinar in attention control by probing the hypothesis that pulvinar is an integral subcortical part of a large-scale attention network and that, with critical input from SC, pulvinar operates by coordinating activity across attentional control centers in fronto-parieto-temporal cortex. Using an integrated multi-modal methods approach that includes simultaneous multi-site recordings with dense electrode arrays, neuroimaging, reversible inactivation and behavioral measures in monkeys trained on variants of an Egly-Driver task, we will probe these ideas by pursuing three specific aims. First, we will systematically characterize attentional modulation and functional interactions across pulvinar subdivisions as a function of behavioral demands by simultaneously recording from large neuronal populations. Second, we will probe the idea that pulvinar coordinates interactions within a fronto-parieto-temporal attention control network, thus acting as a temporal coordinator, in a causal manner by simultaneously recording from FEF, LIP, PITd and their interconnected projection zones in pulvinar before and during reversible pulvinar inactivation. And third, we will investigate causal influences of SC on pulvinar and their effects on pulvino-cortical interactions by simultaneously recording from the aforementioned network and the SC before and during reversible SC inactivation. The significance of the proposed research is that it will contribute to a better understanding of pulvinar’s role in a fundamental cognitive operation, selective attention—the impairment of which has devastating consequences on human health.