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Title: The spatiotemporal dynamics of inhibition of return : evidence from computational modelling and human electrophysiology
Author: Lim, Alfred C. K.
ISNI:       0000 0004 7965 8808
Awarding Body: University of Nottingham
Current Institution: University of Nottingham
Date of Award: 2019
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Inhibition of return (IOR) refers to an orienting mechanism that biases attention against returning to a previously attended location and has frequently been studied with the use of Posner's cue-target paradigm (Posner & Cohen, 1984). Despite numerous studies that have examined many aspects of IOR, the neurophysiological mechanisms underlying IOR are still in dispute. Based on neurophysiological, behavioural, and neuroimaging data, it has been proposed IOR effects are related to different neural mechanisms and are implemented under different circumstances, and these other mechanisms may not be referred to as IOR. Behavioural inhibitory cueing effects (ICEs) are thought to be the result of multiple inhibitory cueing mechanisms - namely sensory adaptation (SA) and direct inhibition (DI). SA biases attention by attenuating the subsequent exogenous activity from an attended location, whereas late output-based DI inhibits oculomotor responses to an attended location. Simulations of inhibitory cueing mechanisms using a dynamic neural field (DNF) model of the intermediate layers of the superior colliculus (iSC) further suggest that such typical delayed behavioural responses to previously attended locations can be attributed to SA and DI. The goal of the present work was to explore the notion of multiple inhibitory mechanisms. The present thesis is structured in seven main chapters: (1) Chapter 1 provides an overview of studies that have explored the different aspects of inhibitory cueing mechanisms, including the stage of processing (i.e., input or output end of the processing continuum), temporal (e.g., onset time and duration), and spatial (e.g., retinotopic- or environment-centred) properties; (2) Chapter 2 investigates inhibitory mechanisms in a traditional cue-target paradigm on account of the two types of orienting processes, namely exogenous and endogenous, by manipulating the cue and target types between peripheral and central arrow stimuli; (3) Chapter 3 examines the dynamics between facilitatory and inhibitory mechanisms in a predictive cueing paradigm by manipulating cue predictability (i.e., 25%, 50%, 75%); (4) Chapter 4 simulates the empirical data collected in the previous two chapters using a two-dimensional DNF model of the iSC; (5) Chapter 5 demonstrates the spatial properties of SA and DI in a multiple-cue paradigm, in which saccadic reaction times were found to decrease as the distance between the target and the centre-of-gravity (CoG) of the cue array increases; (6) Chapter 6 investigates the neurophysiological markers of inhibitory mechanisms by means of steady-state visual evoked potential (SSVEP); and (7) Chapter 7 provides a general discussion of the present work. Overall, the present findings provide evidence supporting the idea that behavioural ICEs are contributed by at least two distinct inhibitory mechanisms, early input-based SA and late output-based DI. Although the two inhibitory mechanisms share the same nature of biasing attention returning to the previous attended location, they were found to have distinct temporal and spatial properties.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QP Physiology