Attending to multiple objects : the dynamics of attentional control in multi-target stimulus arrays

Abstract

In this thesis, the cognitive and neural mechanisms of attentional control are examined, with a specific focus on investigating the temporal dynamics of these mechanisms in scenarios where multiple objects must be attended. Event-related potential (ERP) measures are used to track the continuous time course of visual responses in the brain, and the N2pc component is employed as a marker for the attentional selection of target objects. Two broad lines of research are presented. The first line examines the attentional selection of multiple rapidly presented instances of a single target object defined by varying properties, revealing very rapid and flexible brain responses triggered independently to the appearance of each target. The second line investigates the speed and qualitative nature of strictly serial attention shifts when they are guided by stimulus features or only by location information, revealing the availability of different attentional control mechanisms for these different shifts. In the context of these findings, this thesis attempts to improve the cognitive and neural understanding of how attentional control operates. The attentional template, a working memory representation of currently task-relevant properties, is proposed to flexibly allow for the preparatory enhancement of the activity of neurons that respond to these target-defining properties, allowing for the independent allocation of attention to each instance of a target in real-time. The properties that can be maintained by the attentional template are not restricted to being visual in nature, but can consist of more complex semantic and category-related information. Importantly, the experiments of this thesis demonstrate that attentional control is a highly flexible cognitive mechanism that can be rapidly altered on the basis of current goals, and can rapidly influence the processing of incoming visual informatio