Why are we not constantly hallucinating? These are the questions that the brain must answer

A 1910 study by the psychologist Mary Cheves West Perky found that when our perceptions match what we are imagining, we assume that their inputs are imaginary.

If an imagined signal is strong enough to cross the threshold, the brain takes it for reality.

The new findings raise questions about whether variations or alterations in this system could lead to hallucinations.

Study: Brain scans show imagined and perceived images trigger similar patterns of activity, but the signals are weaker for the imagined ones.

Participants who thought the image was there saw it more vividly than those who thought it was all their imagination.

The observations suggest imagery in our mind’s eye and real perceived images in the world do get mixed together.

The authors speculate that projected images, video and other representations of reality are commonplace in the 21st century .

But they also hint at another possibility: that we could be perceiving the world differently than our ancestors did.

The findings open up questions about whether the mechanism could be relevant to a range of conditions in which the distinction between imagination and perception dissolves.