It’s Sunday morning and I am looking through tweets while watching the news. With smartphones now ubiquitous, such situation are increasingly common: taking in information with multiple interruptions, often by choice. In a new study, researchers studied this phenomenon on the neural level by having people watch movie clips in different combinations – finding significant changes in brain activity when switching between different movie scenes.
“We essentially wanted to assess how task switching and integration of interrupted information streams are accomplished in the brain,” says Lauri Nummenmaa of the University of Turku in Finland. “To that end, we compared how the brain processes natural event scenes when they are presented as whole versus as when interleaved.”
In the study, the movie clips that were “interleaved” jumped back and forth between different plotlines but stayed in the correct order within each movie. The participants viewed the video clips (from the movies Star Wars: Episode IV, Indiana Jones: Raiders of the Lost Ark, and Golden Eye) while undergoing an fMRI scan. The idea, Nummenmaa says, was to simulate channel surfing or even constant switching between independent conversations in a party.
As published in the journal Human Brain Mapping, Nummenmaa and colleagues identified areas of the brain that appear to support integration of smaller events into a coherent event. These areas include the posterior temporal and dorsomedial prefrontal cortices, as well as the cerebellum and dorsal precuneus. Each interruption brought changes to brain activity, with the brain having to constantly reorient itself.
CNS spoke with Nummenmaa about past work in understanding perceptions of events, how they picked the movies for the study, and future work for modelling real-life brain function.
CNS: How did you become personally interested in this research area?
Nummenmaa: As with many research questions, this stemmed from an everyday observation: that we need to switch between task and goals. An example would be channel surfing on TV; another example is changing the radio station while driving, which requires that we interrupt one task while completing the other.
CNS: Why is it important to study interruptions in perception?
Nummenmaa: As task switching is ubiquitous in many complex jobs (think about surgeons or air traffic controllers!) it is important to understand how the brain does it and how it may load the sensory and attention systems in the brain.
CNS: What have we known previously about how we perceive temporally extended events?
Nummenmaa: Previous studies have revealed how the brain automatically “segments” extended events (such as movies) by detecting boundaries between clearly separable events and acts. Moreover, it is known that different brain systems integrate such information at different time scales. Fastest integration occurs in the sensory cortex, followed by parietal attention-related areas and the long-term integration, for example of movie plot, is accomplished in the frontal cortex.
CNS: Why use movies for this study?
Nummenmaa: This type of “natural” tasks have become increasingly popular in brain research lately, as the movies with complex social events provide a very good simulation to real life. Thus, they elicit much stronger and consistent brain responses than conventionally used still pictures or sounds.
CNS: How did you choose the specific movie clips?
Nummenmaa: Well, we’re pretty nerdy people and we obviously enjoy Star Wars, Indy, and 007. From more scientific point of view, all these films were clearly distinguishable in terms of characters and settings, so it was always clear to the viewers that the movie switched to another one when that occurred.
CNS: You gathered data on responses to specific auditory and visual stimuli in the clips… what were you hoping to understand with that?
Nummenmaa: This helped us to model the brain regions responding to, for example, speech and social features in the movies. When we had mapped these regions, we could see whether e.g. the speech-selective regions were most influenced by switching from movie to another.
Interruptions disrupt information accumulation because the brain has to constantly reorient to the new information.
CNS: What were your most excited to find?
Nummenmaa: I think it is fascinating that exactly the same events result in profoundly different activation patterns in the brain if their order is simply altered. These results show that the posterior temporal and dorsomedial prefrontal cortices support integration of events into coherent event sequences, as their responses were most affected by making participants switch their attention from one scene to another and back.
CNS: What do you most want people to understand about this work?
Nummenmaa: Interruptions disrupt information accumulation because the brain has to constantly reorient to the new information. The brain tries to constantly predict what is going to happen next, and with each interruption these predictions have to be revised.
CNS: What’s next for this line of work?
Nummenmaa: We are keen to push this type of cinema viewing studies further, as they are really good for modelling real-life brain function. We are recently started measuring how brain’s specific neurotransmitter systems influence the neural responses to emotional episodes in movies. As many psychiatric drugs target these very same neurotransmitters, this could improve our understanding of different affective disorders.
-Lisa M.P. Munoz
