Cognitive Neuroscience and Neuropsychology

While studies on temporal information processing traditionally focused on psychophysical aspects,1 more recent work on temporal information processing has concentrated on cognitive aspects such as memory and attention. Two main models of temporal information processing have evolved: ‘storage size’ models consider subjective sensation of duration to be a by-product of general information processing and reject the idea of an internal timing mechanism as well as the independent notion of temporal information.2 According to this view, duration judgment is a function of the amount of (non-temporal) information processed during the tobe-judged interval, as it is shown to be affected by factors such as non-temporal information processing load3 or number of contextual changes in a judged interval.4 In contrast, proponents of ‘attentional’ models argue that duration is one of the attributes of any stimulus and, therefore, is information that can be selectively attended to.5 They stress the need for a specific timing mechanism6 that can be triggered by attention.7,8 This timing mechanism has recently been discussed in the context of the functional meaning of the prefrontal cortex.9–11 It is generally agreed that on-line processing of temporal information, such as comparing two duration intervals, requires operations of the working memory.12–14 The notion of working memory used here refers to a modular account of a system conceptualized as consisting of several components: a central executive for decision and control processes and at least two subsystems, specialized for phonological and visuo-spatial information processing.15 However, despite the extensive body of evidence in support of this multi-component model of working memory, the issue of the actual number of its substructures and their neurophysiological specificity requires further research. Additional subdivision of the socalled visuo-spatial sketch-pad, supporting visuospatial processing, into a ‘what-system’ supporting object processing and a ‘where-system’ responsible for processing spatial information,16 as well as that of the phonological loop supporting different aspects of phonological processing,17 are currently under discussion. The multi-component model of working memory and the timer model of temporal information processing were recently brought together by considering an additional component, the ‘context timing signal’, to explain particular time-related aspects during phonological processing.18 The present study addressed the issue of how duration as a specific type of temporal information is stored and manipulated in working memory. We recorded event-related brain potentials (ERPs) from healthy human subjects while they had to maintain either visuo-spatial or temporal information in memory for a subsequent memory test. If multicomponent models of working memory are valid and basic informational dimensions are processed separately by domain-specific memory subsystems, as supposed, topographical differences in ERP activity should occur when subjects are holding either Cognitive Neuroscience and Neuropsychology