Thesis defense Sander Bosch (Donders series 202)

4 February 2016

Promotor: prof. dr. D. Norris, copromotor: dr. C. Döller

Reactivating memories in hippocampus and neocortex

The brain as a time machine
When we vividly remember a previously experienced event, it feels like we travel back in time: we may see, hear or even smell parts of the event. How does memory retrieval work in the brain?
The influential cortical reinstatement theory posits that sensory areas in the brain that are involved during an original experience become active again when remembering this experience. To test this theory, Sander Bosch taught his participants associations between sounds and images. In an MRI-scanner he presented the sounds again, and participants were asked to remember which images belonged with the sounds.
During memory retrieval, the visual cortex was reactivated, consistent with the cortical reinstatement theory. From these activity patterns Sander could predict which image the participants were remembering. The hippocampus, an evolutionarily old structure in the brain, contained information about the newly learned associations between sounds and images. The higher the activation in the hippocampus during memory retrieval, the better the visual reactivation and the participants’ score on the memory task.
The interaction between the hippocampus and the sensory cortex thus seems to support our ability for ‘mental time travel’.