Thesis defense Anke Marit Albers (Donders series 250)

22 March 2017

Promotor: prof. dr. I. Toni, copromotor: dr. F. de Lange

On mental images in the early visual cortex

Imagine you are on a tropical beach with palm trees waving in the wind and a bright blue sky. As you notice, such an image can be very vivid: you see the trees move and you feel the warmth of the sun. But how much does such a fantasy image resemble actual vision?

To investigate this, I showed participants images and asked them to imagine these. Sometimes, we asked the participants to first mentally manipulate the image, for example, to rotate it. Meanwhile, we measured their brain activity in the visual cortex with an MRI scanner. Subsequently, we ‘trained’ a computer to predict which image they were imagining, based on the brain activity. The computer was able to do this much better than you would expect by chance. You could call this brain reading. The patterns in the brain activity resembled those during vision to a large extent. So, if you see that tropical beach in your mind, the visual part of the brain is at work as well and it is almost, as if you really see it.