Watching the 1994 Tom Hanks movie Forrest Gump may have affected you in strange and unusual ways.
British research suggests that throughout the two-hour Hollywood blockbuster the response of your hippocampus, the part of your brain associated with memories, was more likely influenced by subjective event boundaries than by specific transitions between scenes, such as changes in location.
This suggests the hippocampus is sensitive to meaningful units of experience rather than perceptual cues. If that is correct, it likely means that the brain region plays an important role in segmenting our continuous everyday experience into discrete events for storage in long-term memory.
The research, carried out by Aya Ben-Yakov and Richard Henson at the MRC Cognition and Brain Sciences Unit at the University of Cambridge, UK, is among the first to investigate hippocampal function during a natural experience.
The scientists recruited two groups of volunteers. The first was asked to watch Forrest Gump, while the second was shown an abridged version of Alfred Hitchcock’s 1961 television drama Bang! You’re Dead, edited from 30 minutes down to eight.
In each participant, the hippocampus responded as the researchers hypothesised it would.
“We observed a strong hippocampal response at boundaries defined by independent observers, which was modulated by boundary strength (the number of observers that identified each boundary),” they write in a paper published in the journal JNeurosci.
“In the longer film, there were sufficient boundaries to show that this modulation remained after co-varying out a large number of perceptual factors.
“The hippocampus was the only brain region whose response showed a significant monotonic increase with boundary strength in both films, suggesting that modulation by boundary strength is selective to the hippocampus.”
The hippocampus is one of the most widely-studied regions in the human brain, with research suggesting it has many roles, including assisting with navigation and direction, as well as memory formation.
The aim of Ben-Yakov and Henson was not to test how the hippocampus responds in specific situations, but to expose it to a continuous stream of complex information and thus gain an insight into how it behaves in a naturalistic setting.