Abstract
Temporal orienting in humans is typically assessed by measuring classical behavioral measurements, such as reaction times (RTs) and accuracy-rates, and by examining electrophysiological responses. But these methods have some disadvantages: RTs and accuracy-rates provide only retrospective estimates of temporal orientation, and electrophysiological markers are often difficult to interpret. Fixational eye movements, such as microsaccades, occur continuously and involuntarily even when observers attempt to suppress them by holding steady fixation. These continuous eye movements can provide reliable and interpretable information on fluctuations of cognitive states across time, including those that are related to temporal orienting. In a series of studies, we show that temporal orienting is associated with the inhibition of oculomotor behaviors, including saccades, microsaccades and eye-blinks. First, we show that eye movements are inhibited prior to predictable visual targets. This effect was found for targets that were anticipated either because they were embedded in a rhythmic stream of stimulation or because they were preceded by an informative temporal cue. Second, we show that this effect is not specific to the visual modality but is present also for temporal orienting in the auditory modality. Last, we show that the oculomotor inhibition effect of temporal orienting is related to the construction of expectations and not to the estimation of interval duration, and also that it reflects a local trial-by-trial anticipation rather than a global arousal state. We conclude that pre-target inhibition of oculomotor behaviors is a reliable correlate of temporal orienting processes of various types and modalities.