New research significantly advances our understanding of the brain mechanisms that link learning with flexible decision making. The study, published by Cell Press in the May 14th issue of the journal Neuron, demonstrates that the brain does not just learn the structure of the physical world but, through learning, encodes rules that regulate how we interpret future sensory information.
"Successful everyday behavior relies on the ability of the brain to interpret and assign meaning to inherently uncertain sensory information," says senior study author Dr. Zoe Kourtzi from the University of Birmingham. "This is especially critical when the targets of our actions are highly similar to each other, such as identifying predators from prey or friends from strangers in a crowd."
Although successful decisions are thought to benefit from previous experience, the human brain mechanisms that mediate flexible decision making through learning are not well understood. Dr. Kourtzi and colleagues combined psychophysical measurements with advanced functional magnetic resonance imaging to study how participants learned to discriminate between highly similar visual patterns and to assign them in different categories (circular vs. radial).
Participants used two different rules to assign patterns into categories. As a result, patterns belonging to the same category based on one of the rules could be members of different categories based on the alternate rule. "This flexible learning paradigm allowed us to test for brain changes related to the perceived rather than the physical similarity between visual patterns," explains Dr. Kourtzi. "Our use of brain imaging and mathematical algorithms enabled us to extract sensitive information about brain signals that reflected the participant's choice."
The researchers found that neural responses in the frontal cortex changed to reflect a specific choice when participants were required to discriminate between similar sensory signals and assign objects into categories. Intriguingly, changes that reflected perceived categories rather than physical similarity were observed in more posterior brain regions (occipitotemporal areas) that are known to be engaged in the analysis of visual signals. The learning-related changes in the processing of visual categories in these areas were evident independent of the task the participants performed.
"Based on our findings, we propose that once information about categories becomes available through training in posterior brain circuits, it can be retained and potentially fed to frontal circuits that translate these signals into flexible decisions and appropriate actions depending on the task context and requirements," concludes Dr. Kourtzi.