Abstract
Microsaccades, small saccadic eye movements occurring during fixation, have been suggested to be modulated by various sensory, cognitive, and affective processes relating to arousal. Although the modulation of fatigue-related arousal on microsaccade behavior has previously been characterized, the influence of other aspects of arousal, such as emotional arousal, is less understood. Moreover, microsaccades are modulated by cognitive processes (e.g., voluntary saccade preparation) that could also be linked to arousal. To investigate the influence of emotional arousal, saccade preparation, and global luminance levels on microsaccade behavior, emotional auditory stimuli were presented prior to the onset of a fixation cue whose color indicated to look either at the peripheral stimulus (pro-saccade) or in the opposite direction of the stimulus (anti-saccade). Microsaccade behavior was found to be significantly modulated by saccade preparation and global luminance level, but not emotional arousal. In the pro- and anti-saccade task, microsaccade rate was lower during anti-saccade preparation as compared to pro-saccade preparation, though microsaccade dynamics were comparable during both trial types. Our results reveal a differential role of arousal linked to emotion, fatigue, saccade preparation, and global luminance level on microsaccade behavior.
Highlights
Even during periods of visual fixation, our eyes are not perfectly still
The goal of the present study is to investigate the influence of emotional arousal, saccade preparation, and global luminance level on microsaccade rates and dynamics by incorporating emotional auditory stimuli into an interleaved proand anti-saccade paradigm
To understand whether microsaccade dynamics are modulated by emotional arousal evoked by auditory stimuli, we separated trials into two arousal categories in order to have an approximately equal number of trials across conditions and participants
Summary
Even during periods of visual fixation, our eyes are not perfectly still. Instead, small fixational eye movements such as drift, tremor, and microsaccades are commonly observed. After 900–1,100 ms of central fixation, background luminance either increased to 15 or 20 cd/m2, decreased to 0.1 or 5 cd/m2 (both with 50 and 100% contrast relative to the gray background), or stayed the same (10 cd/m2). Previous research has investigated the relationship between emotional processing and microsaccade behavior using visual stimuli (Kashihara et al, 2014; Yep et al, 2018; Krejtz et al, 2020). Foveated visual information modulates fixation-related activity in the SC, which in turn affects microsaccade generation (Hafed, 2011; Hafed and Krauzlis, 2012). To avoid this potential confound associated with the use of visual stimuli, here we used auditory stimuli to induce emotional arousal. The volume of the stimuli was fixed at a level predetermined to be comfortable and clear for all participants
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