We talk about memory for ‘events’, but how does the brain decide what an event is? How does it decide what is part of an event and what isn’t? A new study suggests that our brain uses categories it creates based on temporal relationships between people, objects, and actions — i.e., items that tend to—or tend not to—pop up near one another at specific times.
This explanation is much more in line with the way semantic memory is organized, but challenges the dominant theory that says our brain draws a line between the end of one event and the start of another when things take an unexpected turn.
“Everyone agrees that ‘having a meeting’ or ‘chopping vegetables’ is a coherent chunk of temporal structure, but it’s actually not so obvious why that is if you’ve never had a meeting or chopped vegetables before. You have to have experience with the shared temporal structure of the components of the events in order for the event to hold together in your mind.”
In the study, participants were shown sequences of abstract symbols and patterns, which, unbeknownst to the participants, were grouped into three “communities” of five symbols with shapes in the same community tending to appear near one another in the sequence.
After watching these sequences for roughly half an hour, participants were asked to segment the sequences into events in a way that felt natural to them. They tended to break the sequences into events that coincided with the communities the researchers had prearranged. Images in the same community also produced similar activity in neuron groups at the border of the brain’s frontal and temporal lobes, a region involved in processing meaning.
All of which is to say that event memory seems to be less different from semantic memory than thought - perhaps this is true of other memory domains too?
 . Neural representations of events arise from temporal community structure. Nature Neuroscience [Internet]. 2013 ;16(4):486 - 492. Available from: http://www.nature.com/neuro/journal/v16/n4/abs/nn.3331.html