Why Darkness Doesn’t Descend

We blink yet our conscious theatre appears to still hold in mind a holistic and constant image of our surroundings. It follows, then, that the brain must coalesce and retain visual information for short periods of time, allowing the formation of an uninterrupted stream of vision – a useful feature of the human brain.

Neuroscientists have opined that the brain maintains a form of perceptual memory within its executive and decision-making modules, storing a close representation of — before the blink — experienced states. A region of interest concerning the brains ability to maintain this implicit memory, despite the bombardment of noisy alternate signals, is the prefrontal cortex (PFC). It’s thought that because the cells of PFC exert facets of stability — meaning these neural cells store information for longer periods of time, without much synaptic change from other inputs – they are perhaps contenders for aiding in the ability to maintain perceptual, in between blink, representations.

Caspar Schwiedrzik and his colleagues at New York University had the chance to examine this hypothesis by using patients with epilepsy. In order for these patients not to fall foul to the onset of constant epileptic fits, temporary microelectrodes had to be inserted into their brains. Participants were presented an ambiguous dot lattice on screen and were asked to self-report their perception concerning the orientation of the points (i.e. either horizontal or vertical). Proceeding this first trial, patients were shown a second dot lattice and were again asked the same question. If patients reported perceiving the same orientation in the second trial to the first, this was interpreted to mean that patients used perceptual information recovered from the first to establish a perceptual awareness of the second trial. Whilst patients involved themselves in these tasks their neural activity in the PFC was recorded.

Schwiedrzik and his team found a correlation between PFC elicited Gamma waves and participants aligning their first and second perceptions of the dots’ orientation (e.g. horizontal and horizontal). “Our research shows that the medial prefrontal cortex calibrates current visual information with previously obtained information and thus enables us to perceive the world with more stability, even when we briefly close our eyes to blink,” Caspar Schwiedrzik explained to neurosciencenews.com. Perceptions, however, do not only pertain to the directions in which we see dots moving, as Schwiedrzik says “Even when we see a facial expression, this information influences the perception of the expression on the next face that we look at.”

the mPFC

The medial prefrontal cortex is depicted by the green and the locations of the elicited brain activity are shown with the purple dots. Image credited to Caspar M.Schwiedrzik.   

It appears, from this research, that we do not lose our seamless conscious theatre depicting our outside environments when we blink, due to our prefrontal cortex maintaining memorised perceptions and incorporating them into our further gathered perceptual information. We blink yet our prefrontal cortex still sees.

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