Differential processing of duration changes within short and long sounds in humans Sabine Grimm * , Andreas Widmann, Erich Schro ¨ger Institut fu ¨r Allgemeine Psychologie, Universita ¨t Leipzig, Seeburgstraße 14–20, 04103 Leipzig, Germany Received 26 September 2003; received in revised form 4 November 2003; accepted 13 November 2003 Abstract It has been postulated that there exist two different mechanisms of duration processing. Brief durations, shorter than 500 ms, are processed sensorially, whereas longer durations are processed via a cognitive mechanism. We investigated whether electrophysiological evidence for this distinction can be found. In particular, we measured the mismatch negativity (MMN) to auditory duration deviants (40% decrements) in blocks of short (200 ms) and long sounds (1000 ms) in Ignore and in Attend conditions. Our results show a typical MMN for long and short durations in the Attend condition, whereas no MMN was obtained for long durations in the Ignore condition. This interaction between duration and attention seems to reflect a breakdown of the sensorial mechanism of temporal processing at some critical duration of about 1 s when sounds are ignored. q 2003 Elsevier Ireland Ltd. All rights reserved. Keywords: Mismatch negativity; Sound duration; Auditory sensory memory; Preattentive change detection; Event-related brain potentials; Electrophysiology The processing of time has been an issue since the advent of experimental psychology [6,17]. One common distinction is between a sensorial mechanism for processing duration information and a mechanism that is mediated via cognitive operations. The former is believed to apply to durations up to about one-third of a second, while the latter comes into play with longer durations [10]. However, direct exper- imental evidence for this distinction between sensorial and cognitive time is rare. Nevertheless, there are a few findings that time measurement has quite different properties at sub- and supra-second duration ranges. For instance, psychophysical characteristics differ [2], neuropharmacological effects show a dissociation [12], and the distraction of attention in dual task scenarios can have a differential influence [13]. Furthermore, lesions to specific brain areas elicit differential impairments [1], and recently, Rubia et al. [14] and Lewis and Miall [9] presented neuroimaging data which show separate brain activations for the production as well as the discrimination of intervals shorter or longer than 1 s. They suppose a tight connection between what they call the automatic timing system (related to timing in the milli- second range) and the motor system or cerebellum. Temporal processing of longer durations is mediated by a cognitively controlled timing system, which may use neural circuits that are typically invoked for other cognitive operations, and hence draws on modules within the prefrontal and parietal cortex. Rammsayer [12] reported that the effects of midazolam on the processing of duration information were confined to stimuli exceeding 500 ms in duration, supporting the notion that temporal processing of longer intervals is mediated by working-memory functions whereas that of shorter durations is not. We tested whether the event-related potentials (ERPs) of the human brain may yield additional support for the distinction between two mechanisms for the processing of duration information. We confined our study to the auditory modality, where time is a crucial dimension as the input to be encoded by the brain is in nature serial. We measured the mismatch negativity (MMN) component of the ERP elicited by the infrequent shortening of sound duration (see Refs. [5, 7,8,11]). The MMN component has been proposed as an indicator of preattentive, sensory-memory based deviant detection in audition. MMN is elicited whenever there is a change in a repetitive sequence of stimuli (oddball paradigm). It usually appears at a latency of 100–250 ms 0304-3940/03/$ - see front matter q 2003 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.neulet.2003.11.035 Neuroscience Letters 356 (2004) 83–86 www.elsevier.com/locate/neulet * Corresponding author. Tel.: þ 49-341-9735975; fax: þ 49-341- 9735969. E-mail address: grimms@uni-leipzig.de (S. Grimm).