The Journal of Neuroscience, May 17, 2006, 26(20):5448-5455; doi:10.1523/JNEUROSCI.0440-06.2006
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Behavioral/Systems/Cognitive
Neurophysiology of Implicit Timing in Serial Choice Reaction-Time Performance
Peter Praamstra,1,2
Dimitrios Kourtis,1
Hoi Fei Kwok,1 and
Robert Oostenveld3
1Behavioural Brain Sciences Centre, University of Birmingham, Birmingham B15 2TT, United Kingdom, 2Department of Neurology, Queen Elizabeth Hospital, Birmingham B15 2TH, United Kingdom, and 3F. C. Donders Centre for Cognitive Neuroimaging, 6525 EN Nijmegen, The Netherlands
Correspondence should be addressed to Peter Praamstra, Behavioural Brain Sciences Centre, University of Birmingham, Birmingham B15 2TT, UK. Email: p.praamstra{at}bham.ac.uk
Neural representations of time for the judgment of temporal durations are reflected in electroencephalographic (EEG) slow brain potentials, as established in time production and perception tasks. Here, we investigated whether anticipatory processes in reaction-time procedures are governed by similar mechanisms of interval timing. We used a choice reaction task with two different, temporally regular stimulus presentation regimes, both with occasional deviant interstimulus intervals. Temporal preparation was shown in the form of adjustments in time course of slow brain potentials, such that they reached their maximum amplitude just before a new trial, independent of the duration of the interstimulus interval. Preparation was focused on a brief time window, demonstrated by a drop in amplitude of slow potentials as the standard interval had elapsed in deviant interstimulus intervals. Implicit timing influencing perceptual processing was shown in reduced visual-evoked responses to delayed stimuli after a deviant interstimulus interval and in a reduction of EEG
power over the visual cortex at the time when the standard interval had elapsed. In contrast to explicit timing tasks, the slow brain potential manifestations of implicit timing originated in the lateral instead of the medial premotor cortex. Together, the results show that temporal regularities set up a narrow time window of motor and sensory attention, demonstrating the operation of interval timing in reaction time performance. The divergence in slow brain potential distribution between implicit and explicit timing tasks suggests that interval timing for different behaviors relies on qualitatively similar mechanisms implemented in distinct cortical substrates.
Key words: motor preparation; premotor cortex; electroencephalography; contingent negative variation; reaction time; timing
Received Jan. 31, 2006;
revised March 21, 2006;
accepted April 12, 2006.
Correspondence should be addressed to Peter Praamstra, Behavioural Brain Sciences Centre, University of Birmingham, Birmingham B15 2TT, UK. Email: p.praamstra{at}bham.ac.uk
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