Automatic Temporal Expectancy: A High-Density Event-Related Potential Study

Giovanni Mento,Michela Sarlo,Vincenza Tarantino,Patrizia Silvia Bisiacchi,Warren H Meck

doi:10.1371/journal.pone.0062896

Abstract

How we compute time is not fully understood. Questions include whether an automatic brain mechanism is engaged in temporally regular environmental structure in order to anticipate events, and whether this can be dissociated from task-related processes, including response preparation, selection and execution. To investigate these issues, a passive temporal oddball task requiring neither time-based motor response nor explicit decision was specifically designed and delivered to participants during high-density, event-related potentials recording. Participants were presented with pairs of audiovisual stimuli (S1 and S2) interspersed with an Inter-Stimulus Interval (ISI) that was manipulated according to an oddball probabilistic distribution. In the standard condition (70% of trials), the ISI lasted 1,500 ms, while in the two alternative, deviant conditions (15% each), it lasted 2,500 and 3,000 ms. The passive over-exposition to the standard ISI drove participants to automatically and progressively create an implicit temporal expectation of S2 onset, reflected by the time course of the Contingent Negative Variation response, which always peaked in correspondence to the point of S2 maximum expectation and afterwards inverted in polarity towards the baseline. Brain source analysis of S1- and ISI-related ERP activity revealed activation of sensorial cortical areas and the supplementary motor area (SMA), respectively. In particular, since the SMA time course synchronised with standard ISI, we suggest that this area is the major cortical generator of the temporal CNV reflecting an automatic, action-independent mechanism underlying temporal expectancy.

Highlights

Time processing is one of the most pervasive aspects of our mental functioning since it is involved in all motor, perceptual, and cognitive activities
In the standard Inter-Stimulus Interval (ISI) condition S2 appeared eliciting a large sensory-evoked activity. In both the deviant ISI conditions the Contingent Negative Variation (CNV) showed a slope inversion turning toward the baseline, S2 occurred here after several hundreds of milliseconds from S2 METP
We speculated that if the supplementary motor area (SMA) plays a crucial role in perceptual timing, this area should stay activated while expecting S2, showing typical time course activation characterised by the peak maximum at S2 METP

Summary

Introduction

Time processing is one of the most pervasive aspects of our mental functioning since it is involved in all motor, perceptual, and cognitive activities. There has been growing interest in understanding the cognitive mechanisms and the neural bases underlying timing [1,2,3,4,5]. A functional taxonomy of timing processes has been proposed by Coull and Nobre [6], which identifies distinct explicit and implicit mechanisms. Explicit timing is engaged by tasks requiring either motor production (motor timing) or perceptual discrimination (perceptual timing). Implicit timing is indirectly engaged as an epiphenomenon of the temporal regularity of either a motor output (emergent timing) or a perceptual input (temporal expectation). Temporal expectation may arise incidentally from a regular stimulus structure (exogenous temporal expectation) or may be consciously driven by informative pre-cues (endogenous temporal expectation)

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