Abstract
Expected surprise, defined as the anticipation of uncertainty associated with the occurrence of a future event, plays a major role in gaze shifting and spatial attention. In the present study, we analyzed its impact on oculomotor behavior. We hypothesized that the occurrence of anticipatory saccades could decrease with increasing expected surprise and that its influence on visually-guided responses could be different given the presence of sensory information and perhaps competitive attentional effects. This hypothesis was tested in humans using a saccadic reaction time task in which a cue indicated the future stimulus position. In the ‘no expected surprise’ condition, the visual target could appear only at one previously cued location. In other conditions, more likely future positions were cued with increasing expected surprise. Anticipation was more frequent and pupil size was larger in the ‘no expected surprise’ condition compared with all other conditions, probably due to increased arousal. The latency of visually-guided saccades increased linearly with the logarithm of surprise (following Hick’s law) but their maximum velocity repeated the arousal-related pattern. Therefore, expected surprise affects anticipatory and visually-guided responses differently. Moreover, these observations suggest a causal chain linking surprise, attention and saccades that could be disrupted in attentional or impulse control disorders.
Highlights
Expected surprise, defined as the anticipation of uncertainty associated with the occurrence of a future event, plays a major role in gaze shifting and spatial attention
It has been shown that cortico-spinal excitability (CSE) as measured using transcranial magnetic stimulation is globally reduced by a task-irrelevant unexpected sound in a visually-guided Go/NoGo task[32]
Pupil size presented a biphasic time course starting with an initial transient response lasting approx. 500 ms followed by a sustained change lasting approximately 1500 ms
Summary
Expected surprise, defined as the anticipation of uncertainty associated with the occurrence of a future event, plays a major role in gaze shifting and spatial attention. We hypothesized that the occurrence of anticipatory saccades could decrease with increasing expected surprise and that its influence on visually-guided responses could be different given the presence of sensory information and perhaps competitive attentional effects. This hypothesis was tested in humans using a saccadic reaction time task in which a cue indicated the future stimulus position. Expected surprise affects anticipatory and visually-guided responses differently These observations suggest a causal chain linking surprise, attention and saccades that could be disrupted in attentional or impulse control disorders. The influence of expected surprise on visually-guided responses could be different given the presence of sensory information and perhaps competitive attentional effects. Pupil size could encode arousal related to surprise independently of other eye movements and indicate its subjective impact
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