New research investigates the manner in which the brain sorts out priorities and keeps processes organized.
For example, your brain knows it’s time to cook when the stove is on, and the food and pots are out. When you rush away to calm a crying child, though, cooking is over and it’s time to be a parent.
Your brain processes and responds to these occurrences as distinct, unrelated events.
Researchers wanted to study the manner by which the brain breaks such experiences into “events,” or the related groups that help us mentally organize the day’s many situations.
A dominant concept of event-perception known as prediction error says that our brain draws a line between the end of one event and the start of another when things take an unexpected turn (such as a suddenly distraught child).
In the new study, Princeton University researchers challenge the concept of prediction error and suggest that the brain may actually work from subconscious mental categories it creates based on how it considers people, objects and actions are related.
Specifically, these details are sorted by temporal relationship, which means that the brain recognizes that they tend to — or tend not to — pop up near one another at specific times.
Results from the new study are reported in the journal Nature Neuroscience.
Investigators believe a series of experiences that usually occur together (temporally related) form an event until a non-temporally related experience occurs and marks the start of a new event.
In the example above, pots and food usually make an appearance during cooking; a crying child does not. Therein lies the partition between two events, or so says the brain.
This dynamic, which the researchers call “shared temporal context,” works very much like the object categories our minds use to organize objects, explained lead author Anna Schapiro, a doctoral student in psychology and neuroscience.
“We’re providing an account of how you come to treat a sequence of experiences as a coherent, meaningful event,” Schapiro said. “Events are like object categories. We associate robins and canaries because they share many attributes: They can fly, have feathers, and so on. These associations help us build a ‘bird’ category in our minds. Events are the same, except the attributes that help us form associations are temporal relationships.”
Researchers found support for this theory when they discovered brain activity when individuals observed abstract symbols and patterns with no obvious similarity were presented as a group to study participants. The “grouping” apparently excited the brain as overlapping groups of neurons were observed.
From this, the researchers constructed a computer model that can predict and outline the neural pathways through which people process situations, and can reveal if those situations are considered part of the same event.
The parallels drawn between event details are based on personal experience, Schapiro said. People need to have an existing understanding of the various factors that, when combined, correlate with a single experience.
“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,” Schapiro said.
“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,” she said. “And the way the brain implements this is to learn to use overlapping neural populations to represent components of the same event.”
During a series of experiments, the researchers presented human participants with sequences of abstract symbols and patterns. Without the participants’ knowledge, the symbols 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, which shows that the brain quickly learns the temporal relationships between the symbols, Schapiro said.
The researchers then used functional magnetic resonance imaging to observe brain activity as participants viewed the symbol sequences. Images in the same community produced similar activity in neuron groups at the border of the brain’s frontal and temporal lobes, a region involved in processing meaning.
The researchers interpreted this activity as the brain associating the images with one another, and therefore as one event. At the same time, different neural groups activated when a symbol from a different community appeared, which was interpreted as a new event.
The researchers fashioned these data into a computational neural-network model that revealed the neural connection between what is being experienced and what has been learned. When a simulated stimulus is entered, the model can predict the next burst of neural activity throughout the network, from first observation to processing.
“The model allows us to articulate an explicit hypothesis about what kind of learning may be going on in the brain,” Schapiro said.
“It’s one thing to show a neural response and say that the brain must have changed to arrive at that state. To have a specific idea of how that change may have occurred could allow a deeper understanding of the mechanisms involved.”
Source: Princeton University