Timing processes: an outline of behavioural and neural indices not systematically considered in timing models.

This paper deals with two questions: what are the main characteristics of timing performance, and how do current timing models account for them? An outline of the most significant behavioural and neural indices of time processing is presented, with particular emphasis on the effects of activation and attention, and on data drawn from an important electrophysiological indice, the Contingent Negative Variation (CNV). A sample of influent timing models is then considered, ranged in two categories depending on whether they provide a representation of the time elapsing online between the limits of a target interval or a representation of the interval limits. The authors support the concept of online "pulse accumulation" as various types of cumulative mechanisms have been described at both neural and behavioural levels.