Down but not out in posterior cingulate cortex : Deactivation yet functional coupling with prefrontal cortex during demanding semantic cognition

The posterior cingulate cortex (pCC) often deactivates during complex tasks, and at rest is often only weakly correlated with regions that play a general role in the control of cognition. These observations led to the hypothesis that pCC contributes to automatic aspects of memory retrieval and cognition. Recent work, however, has suggested that the pCC may support both automatic and controlled forms of memory processing and may do so by changing its communication with regions that are important in the control of cognition across multiple domains. The current study examined these alternative views by characterising the functional coupling of the pCC in easy semantic decisions (based on strong global associations) and in harder semantic tasks (matching words on the basis of specific non-dominant features). Increasingly difficult semantic decisions led to the expected pattern of deactivation in the pCC; however, psychophysiological interaction analysis revealed that, under these conditions, the pCC exhibited greater connectivity with dorsolateral prefrontal cortex (PFC), relative to both easier semantic decisions and to a period of rest. In a second experiment using different participants, we found that functional coupling at rest between the pCC and the same region of dorsolateral PFC was stronger for participants who were more efficient at semantic tasks when assessed in a subsequent laboratory session. Thus, although overall levels of activity in the pCC are reduced during external tasks, this region may show greater coupling with executive control regions when information is retrieved from memory in a goal-directed manner

Boosted visual performance after eye blinks

We blink more often than is required for eye lubrication, frequencies fluctuating greatly depending on task. Are there perceptual or cognitive benefits that may justify the high frequency of eye blinks? We tested the effect of blinks on performance in a rapid serial visual presentation (RSVP) task. In Experiment 1, participants had to identify a target digit embedded in a random stream of letter distractors, presented foveally for 60 ms each. Participants blinked once during the presentation stream. In a separate condition, blinks were simulated by shutter glasses. We found enhancements of performance (up to ~15% increased accuracy) for targets appearing up to ~360 ms after real or simulated blinks. This finding was replicated for object recognition with naturalistic stimuli (Experiment 2), but not in a numerosity task (Experiment 3), and not for perifoveally distributed stimuli (Experiment 4). This early performance boost may be based on retinal transients. We also observed a later performance boost 900-1080 ms after blinks, but not simulated blinks. This later boost may be based on an attentional reset triggered by eye blinks. Based on data across all experiments, eyeblinks can enhance object recognition via introducing artificial transients and via causing a reset of attention

Boosted visual performance after eye blinks

We blink more often than required for maintaining the corneal tear film. It is unclear whether there are perceptual or cognitive consequences of blinks that may justify their high frequency. Recent findings showed that blinks occur at consistent time points and may indicate switches between large scale cortical networks, such as dorsal attention and default-mode networks. Thus, blinks may trigger a refresh of visual attention, although this has so far not been confirmed behaviourally. Here, we tested the effect of blinks on visual performance in a rapid serial visual presentation task. In Experiment 1, participants had to identify a target digit embedded in a random stream of letter distractors, presented foveally for 60 ms each. Participants blinked once during the presentation stream. In a separate condition, blinks were simulated by shutter glasses. We found enhancements of performance (up to 15% point increase in accuracy) for targets appearing up to 300 ms after blinks. This finding was replicated for object recognition with naturalistic stimuli (Experiment 2) and for spatially distributed stimuli (Experiment 4), but not in a numerosity task (Experiment 3). We also observed a later, suatained performance boost after blinks in five experiments. While the early performance boost may be partially based on retinal transients induced by blinks, the later boost signifies an attentional reset triggered by eye blinks. We conclude that eye blinks lead to attentional benefits in the period after reopening of the eyelids and may be used strategically for temporarily boosting visual performance