The behavioural and neurophysiological modulation of microsaccades in monkeys

Systematic modulations of microsaccades have been observed in humans during covert orienting. We show here that monkeys are a suitable model for studying the neurophysiology governing these modulations of microsaccades. Using various cue-target saccade tasks, we observed the effects of visual and auditory cues on microsaccades in monkeys. As in human studies, following visual cues there was an early bias in cue-congruent microsaccades followed by a later bias in cue-incongruent microsaccades. Following auditory cues there was a cue-incongruent bias in left cues only. In a separate experiment, we observed that brainstem omnipause neurons, which gate all saccades, also paused during microsaccade generation. Thus, we provide evidence that at least part of the same neurocircuitry governs both large saccades and microsaccades

Priming of pop-out depends upon the current goals of observers.

What you have seen before helps you see it again. This effect has been shown in visual search studies looking at the consequence of the previous trial: Reaction times are shorter when the features defining a target and distractors are repeated. Here, I explore whether this bias in attentional selection occurs automatically or whether it depends upon the current goals of observers. Participants performed a visual search task, in which both a color singleton and a shape singleton appeared in the search array. The observers were instructed at the beginning of every trial as to which singleton was relevant. The data show that repeating the color or shape from the previous trial benefits performance only when this information is relevant to the observers' current goals