Visual sensory discrimination of threatening stimuli presenting different durations: A magnetoencephalographic and behavioral study

Whether time exposure influences visual sensory processing of emotional stimulation is an unexplored issue, despite its relevance to understanding affective processing. We recorded magnetoencephalographic (MEG) activity -concretely event-related magnetic fields (ERFs)- from 25 participants while attending to spiders (emotional stimuli) and wheels (neutral) silhouettes they had to categorize. These stimuli were presented during 33.33, 66.66, 133.33, and 266.66 ms, and could appear at the center of the screen (fixation) or in the lower visual field (periphery). Behavioral performance revealed improved detection of negative emotional stimuli at fixation, and this effect did not interact with exposure time. At the neural level, greater amplitudes for spiders than for wheels were observed when presented at fixation in two visual ERF components, M100 and M150, an effect originating in striate and extrastriate visual cortices, respectively. This effect, ocurring later for stimuli presented at the periphery (M210, estimated in the extrastriate cortex), neither interacted with stimulus duration. This threat detection mechanism in the visual cortex independent of stimulus duration points to an all-or-nothing, rather than gradual, sensory discrimination of emotional cues regarding their exposure time.