Carl Zimmer does a nice piece
on the tens of millions of people who don't experience a mental camera. The condition has been named aphantasia, and millions more experience extraordinarily strong mental imagery, called hyperphantasia. British neurologist Adam Zeman estimates that 2.6 percent of people have hyperphantasia and that 0.7 percent have aphantasia...a website called the Aphantasia Network
has grown into a hub for people with the condition and for researchers studying them.
The vast majority of people who report a lack of a mind’s eye have no memory of ever having had one, suggesting that they had been born without it. Yet...they had little trouble recalling things they had seen. When asked whether grass or pine tree needles are a darker shade of green, for example, they correctly answered that the needles are.
Researchers are .. starting to use brain scans to find the circuitry that gives rise to aphantasia and hyperphantasia. So far, that work suggests that mental imagery emerges from a network of brain regions that talk to each other...Decision-making regions at the front of the brain send signals to regions at the back, which normally make sense of information from the eyes. Those top-down signals can cause the visual regions to produce images that aren’t there.
In a study published in May, Dr. Zeman and his colleagues scanned the brains of 24 people with aphantasia, 25 people with hyperphantasia and 20 people with neither condition...The people with hyperphantasia had stronger activity in regions linking the front and back of the brain. They may be able to send more potent signals from decision-making regions of the front of the brain to the visual centers at the back.
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