Human intracranial recordings link suppressed transients rather than 'filling-in' to perceptual continuity across blinks

Abstract

We hardly notice our eye blinks, yet an externally generated retinal interruption of a similar duration is perceptually salient. We examined the neural correlates of this perceptual distinction using intracranially measured ECoG signals from the human visual cortex in 14 patients. In early visual areas (V1 and V2), the disappearance of the stimulus due to either invisible blinks or salient blank video frames ('gaps') led to a similar drop in activity level, followed by a positive overshoot beyond baseline, triggered by stimulus reappearance. Ascending the visual hierarchy, the reappearance-related overshoot gradually subsided for blinks but not for gaps. By contrast, the disappearance-related drop did not follow the perceptual distinction – it was actually slightly more pronounced for blinks than for gaps. These findings suggest that blinks' limited visibility compared with gaps is correlated with suppression of blink-related visual activity transients, rather than with "filling-in" of the occluded content during blinks.DOI: http://dx.doi.org/10.7554/eLife.17243.001

Widespread Suppression of High-Order Visual Cortex During Blinks and External Predictable Visual Interruptions

“…Suppression of blink-related visual responses is commonly viewed as a product of a specialized 'hardwired' efferent copy pathway, linking oculomotor activity with suppression of visual responses (e.g., in the seminal work by Volkmann et al 1980;Volkmann et al 1982). This view is also supported by psychophysical (Bidder and Tomlinson 1997) and electrophysiological (Golan et al 2017) evidence linking blink suppression with saccadic suppression.…”

“…To further control for potential duration differences between spontaneous and voluntary blinks, we matched the durations of the two blink types selecting a subset of spontaneous blink events and a subset of voluntary blink events so the two subsets will have a highly compatible duration distribution. This was done using an iterative procedure (Golan et al 2016): in each iteration, a pair of a spontaneous blink and a voluntary blink was added to the selected subsets. The criteria for selection were a duration difference of no more than 5 ms between the spontaneous and voluntary blink, and the minimization of the mean duration of the two subsets.…”

“…If we had the fMRI results alone, the most straightforward interpretation of the mid-and high-level visual cortex effects would have been that unpredictable external darkenings excite the high-level visual cortex whereas spontaneous and voluntary blinks, as well as self-initiated external darkenings, reduce its activity. However, timeresolved iEEG recordings acquired across the visual cortex during a similar task (Golan et al 2016) mandate a more nuanced interpretation: these recordings showed that the unpredictable darkenings caused a small, transient activity drop (see Golan et al, 2016…”

“…Spontaneous blinks during movie watching were found to be correlated with default mode activation (Nakano et al 2013). Finally, our recent intracranial EEG (iEEG) study of spontaneous blinks (Golan et al 2016) revealed that positive stimulus-driven activation transients in high order visual areas were suppressed during spontaneous blinks, potentially accounting for the lack of visual awareness of these interruptions.…”

“…In particular, when eye blinks and external darkenings are contrasted, at least one major general cognitive factor confounds this contrast -predictability. Whereas eye blinks (either spontaneous or voluntary) are self-initiated and thus predictable, external darkenings, as applied in all of the studies that used this control (including Martin 2000, 2002;Nakano et al 2013;Golan et al 2016), were controlled by the experimenter and presented in an unpredictable manner.…”