A multi-level account of selective at tention

Neural information processing systems must overcome a series of bottlenecks that interrupt the sequence of events between sensory input and motor output. First, the sensory neurons that encode external stimuli are noisy. As a result, an identical stimulus will evoke a slightly diff erent response pattern each time it is presented, and this instability can place limits on the amount of information that neurons can relay about stimulus features (Pouget, Dayan, and Zemel 2003; Seung and Sompolinsky 1993). Second, multiple items in the visual fi eld compete for representation, and this competition must be resolved so that the most behaviourally relevant sensory stimuli are represented and allowed to guide goal-directed behaviour. Th ird, there are limits on the number of responses that can be selected simultaneously (Pashler 1994), and obvious limits on the number of simultaneous motor plans that can be executed. All of these factors restrict the speed and accuracy of sensory–response mappings, and at each stage, relevant stimuli must be prioritized over irrelevant distractors to ensure the successful completion of behavioural goals. Th e ability to prioritize relevant stimuli is generally referred to as selective attention , where the prefi x selective is intentionally used to distinguish the term from changes in general arousal or states of consciousness. Th ere are three general mechanisms that support selection attention: signal enhancement, external and internal noise suppression, and selective read-out. Th e fi rst two mechanisms infl uence selection by directly mediating the information content of neural representations as sensory signals are relayed and transformed across the processing hierarchy. Selective read-out is conceptually diff erent, as it does not directly modify the quality of sensory representations. Instead, selective read-out infl uences the effi ciency with which sensory information is used to inform decisions about the contents of the sensory array, either in the absence of or in combination with signal enhancement and noise suppression. OUP UNCORRECTED PROOF – REVISES, Mon Dec 02 2013, NEWGEN