Different patterns of brain activity help to distinguish between images recalled from memory and the sight of physical objects.

Picture a strawberry. Most people can easily distinguish between that image in their mind’s eye and an actual strawberry. Now researchers say that they’ve worked out how the brain draws this distinction and where in the brain the process happens.

According to a study1 in monkeys, the key part of the brain is the primary visual cortex, which is also involved in vision. The authors found that neurons in this region displayed a different activity pattern for images conjured up from memory compared with that for real-time visual input. They conclude that the primary visual cortex is crucial for recalling images stored in memory.

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