Brain activity during normal behaviour reflects a combination of externally generated (sensory) and internally generated (thought) representations. For example, when driving a car, the parts of the brain that process what we see might represent both a person crossing the street and the mental picture of a map to help us navigate.
Because the capacity of the visual system is limited, externally and internally generated information compete for representation. Therefore, successful behaviour requires us to rapidly and frequently shift attention between external and internal sources of information, for example to prioritize what you see when a pedestrian is about to cross the road. The ability to do this differs between individuals and deteriorates with age.
Unique combination of methods
During this project, Marius Peelen will use human brain scans and behavioural tasks to explore how the brain handles information from the outside world in combination with information from our own thoughts. Peelen: “We plan to investigate how these two types of information interact in the visual part of the brain. To accomplish this, we will apply ideas and models from visual neuroscience to understand how external and internal representations compete with each other in our brain.”
To provide an overview of the project, the project will: show how what we see and what we think about compete in the brain; reveal how focusing our attention (inwards or outwards) changes this competition; compare how this competition works in younger and older people to understand how aging affects it; investigate how different people's thinking styles - how vivid their mental images are, and how prone they are to hallucinations - affect this competition; and finally, test how internal-external competition affects real-life situations, like riding a bike in traffic, using a bike simulator.
Altogether, the aim is to provide a neural mechanism for why we sometimes succeed and sometimes fail in simultaneously processing external and internal visual information. The outcomes of this study could be relevant for informing traffic safety policy and the way we should use traffic signs for instance.
